United States
Environmental Protection
Agency
Research and Development
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-78-154
September 1978
Animal Waste Composting
with Carbonaceous
Material
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E PA-600/2-78-154
September 1978
ANIMAL WASTE COMPOSTING WITH CARBONACEOUS MATERIAL
by
W. S. Galler
C. B. Davey
W. L. Meyer
D. S. Airan
North Carolina State University
Raleigh, North Carolina 27607
Grant No. 00270
Project Officer
Clarence A. demons
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
This study was conducted
in cooperation with
U.S. Department of Health, Education, and Welfare
Public Health Service
Consumer Protection and Environmental Health Service
Environmental Control Administration
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
i i
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FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled
land are tragic testimony to the deterioration of our natural environment.
The complexity of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem solu-
tion and it involves defining the problem, measuring its impact, and search-
ing for solutions. The Municipal Environmental Research Laboratory develops
new and improved technology and systems for the prevention, treatment, and
management of wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources, for the preservation and treatment of
public drinking water supplies, and to minimize the adverse economic, social,
health, and aesthetic effects of pollution. This publication is one of the
products of that research; a most vital communications link between the re-
searcher and user community.
This report covers research conducted in the combining of selected
organic waste materials in a manner that eliminates the formation of second-
ary pollutants and produces a safe, aesthetically pleasing, and effective
soil amendment. The materials used are of agricultural origin but have
municipal and industrial analogs. Consequently, the information contained
in this report should be of interest to anyone concerned with the disposal
of organic solid wastes.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
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ABSTRACT
High-rate thermophilic composting of animal wastes and added carbonaceous
waste followed by land application has considerable potential for the treat-
ment and useful final disposal of organic wastes. The process described in
this report involves a mechanically mixed, thoroughly aerated, thermophilic
first stage in which the readily available carbonaceous materials are utilized
by bacteria during the stabilization of the nitrogenous wastes. This is fol-
lowed by a curing period in which the hollocellulose is partially decomposed,
principally by fungi. The compost may then be added to soil.
During the thermophilic stage, the composting material must be continu-
ously mixed at a slow rate to ensure that oxygen reaches all parts of the
mass. Additionally, forced aeration must be used otherwise the oxygen sup-
plied is used up in less than 2 minutes. Under forced aeration, nitrogen
losses are minimized. The completion of this stage is recognized, in batch
operation, by a decrease in both temperature and oxygen usage.
Continuous runs were carried out in which up to 60-80 percent of the
mass could be replaced daily. For the material removed during both batch and
continuous runs the undersirable characteristics contributed by animal waste
had disappeared.
Placed in storage after the initial thermophilic phase, the compost again
heated as filamentous fungi spread through the material. During this second
stage (about 4 weeks), the hollocellulose content decreased and the cation-
exchange-capacity increased.
Testing the compost's effect on plant growth was done in three phases.
The first phase involved spreading the compost over grass as a top-dressing;
the second was a greenhouse study using tomatoes, wheat, millet, and beans;
and the third was a field test on tomato crops.
In all three tests, the compost exhibited significant beneficial effects.
The mulching experiment yielded increases in the dry weights of grasses of up
to 57 percent over the control. The greenhouse experiments (terminated after
90 days) showed increases in dry weights of up to 400 percent for tomatoes
and wheat over the control (no compost or inorganic fertilizer added).
Field studies using tomato plants were carried out at six compost appli-
cation rates ranging from 5.6 to 488 tonnes/ha. Although the plots having
lower treatments yielded fruit approximately 1 to 2 weeks earlier than those
with the higher treatments, both the tomato size and total yield over the
growing season increased with increasing compost application. The tomato size
i v
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increased from an average of 92 g for the control to 119 g for the maximum
treatment whereas the maximum yield increased from less than 50 to an esti-
mated 167 tonnes/ha.
This report was submitted in fulfillment of Contract No. 00270 by North
Carolina State University under the sponsorship of the U.S. Environmental
Protection Agency. This report covers the period June 1, 1967, to May 31,
1970, and work was completed September 30, 1975.
v
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CONTENTS
Forward i i i
Abstract iv
Figures viii
Tables x
1. Conclusions and Recommendations 1
2. Introduction and Literature Review 3
The extensive solid waste problem 3
Composting 4
Product evaluation 12
3. Thermophilic Composting 18
Experimental arrangement 18
Experimental procedure 20
Results 22
4. Economic Feasibility 52
Level of production 52
Costs of production 53
Sale of compost 59
Minimum production level 59
5. Product Evaluation 63
Materials and methods 63
Results and discussion 65
References 92
vi i
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FIGURES
Number Page
1 Growth phases in biological processes 6
2 Relation between moisture and oxygen uptake rates 8
3 Relation between temperature and oxygen uptake rates g
4 pH variations in batch composting 10
5 Diagram of composting system 19
6 Comparisons of decomposition rate for completely aerobic and
partly anaerobic systems 25
7 Phases of batch composting as evidenced by changes in acidity ... 26
8 Phases of batch composting as evidenced by temperature 26
9 Oxygen uptake rates during the course of decomposition of C:N
25 and C:N 40 batch mixtures 27
10 Total oxygen uptake as a function of composting time 28
11 Relationships between volatile solids reduction, percentage
manure, and initial C:N for batch composting of sawdust and
poultry manure mixtures 30
12 Effect of storage upon compost maturity as evidenced by
holocel1ulose content 32
13 Effect of storage upon compost maturity as evidenced by cation
exchange capacity 32
14 Temperature variation during continuous composting with saw-
dust and swine waste 35
15 Temperature variation during continuous composting with saw-
dust and poultry waste 36
16 Temperature variation during continuous composting with saw-
dust and poultry waste 37
vi i i
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Number Page
17 Temperature variation during continuous composting with
shredded paper and poultry waste 38
18 Moisture content variation during continuous composting with
sawdust and poultry waste 40
19 Ash content variation during continuous composting with saw-
dust and poultry waste 41
20 Acidity variation during continuous composting with shredded
paper and poultry waste 43
21 Bulkweight variation during continuous composting with saw-
dust and poultry waste 46
22 Typical "heating phenomenon" evidenced by composted shredded
paper and poultry waste undergoing storage 48
23 Compost cost-return curve 61
24 Dry weight yields of millet, tomato, and wheat tops in response
to sawdust-poultry manure compost and soil mixtures 70
25 Total tomato fresh weight yield and yield per tonne of sawdust-
poultry manure compost in the field 76
26 Water holding capacity of soil and soil-compost mixture over
a range of tensions from 0 to 15 bars 85
27 Total tomato fresh weight yield and yield per tonne of paper-
poultry manure compost in the field 87
ix
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TABLES
NUMBER Page
1 Essential Nutrient Contents of Sawdust and Poultry Manure 23
2 Nitrogen Losses During the Course of Decomposition of
Sawdust and Poultry Manure Mixtures 29
3 Mean, Standard Deviation, and Standard Error of the Mean
for the Chemical Composition of Domestic Refuse in
Raleigh, North Carolina 33
4 Variation of Average Moisture, Ash, and Volatile Solids
Content in Input Mix and Output Compost in Different
Continuous Runs 39
5 Nitrogen Loss in Different Continuous Runs 44
6 Essential Nutrients and Moisture in Raw Materials 45
7 Antibiotics Tested for Use in Isolation Media 49
8 Cardinal Temperatures of Organisms Isolated from
Poultry Manure-Sawdust Compost 51
9 Unit Production Cost at Different Levels of Production 60
10 Physical and Chemical Characteristics of Composts
Utilized in this Study 66
11 Dry Weight Production of Three Harvests of Lawn
Grasses at Various Rates of Sawdust-Poultry Manure Compost
Applied as a Surface Mulch 68
12 Nitrogen Uptake by Lawn Grasses at Various Rates of Sawdust-
Poultry Manure Compost Applied as a Surface Mulch 68
13 Total Nutrient Uptake by Tomatoes in the Greenhouse 72
14 Soil Test Levels Prior to Sawdust-Poultry Manure Compost
Addition 73
x
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Number Page
15 Residual Soil Test: Soil Test Levels After Sawdust-
Poultry Manure Compost Additions and Growing Tomatoes
for 90 Days 73
16 Initial Soil Test: Soil Test Prior to Adding Sawdust-
Poultry Manure Compost 78
17 Residual Soil Test: Soil Test After Adding Sawdust-
Poultry Manure Compost 78
18 Total Nutrient Uptake and Dry Weight Production in the
Field of Marion Tomatoes in Response to Sawdust-
Poultry Manure Compost 79
19 Total Dry Weight Production of Tomatoes in the Field
in Response to Sawdust-Poultry Waste Compost 81
20 Nitrogen Removal from Soil by Tomato Plants and Fruit in
the Field in Response to Sawdust-Poultry Waste Compost 81
21 Per Plant Dry Weight Production of Tomatoes in the Field
in Response to Sawdust-Poultry Waste Compost 82
22 N and P Content of Tomatoes: Total Uptake from Sawdust-
Poultry Manure Compost 84
23 Cation Content of Field-Grown Tomatoes in Mi Hi equivalents
per Gram of Dry Weight 84
24 Nutrient Uptake by Tomatoes in the Field at Various Levels
of Paper-Poultry Manure Compost 88
25 Initial and Residual Soil Test: Soil Test Values Before
and After Adding Paper-Poultry Waste Compost and Growing
Tomato Crop 90
xi
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SECTION 1
CONCLUSIONS AND RECOMMENDATIONS
The following conclusions resulted from the data and experience obtained
during the fulfillment of Grant Number EC 00270.
1. The practicality of aerobic thermophilic composting of animal wastes
with carbonaceous material has been demonstrated. A wide range of types of
both materials are suitable for use in the process.
2. The process is a two-stage fermentation. The first stage occurs
under conditions of forced aeration, mechanical mixing and very high tempera-
ture, and may be accomplished in batches or as a continuous process. In this
stage bacteria are the principal active agents and the soluble components of
the mixture are stabilized. The second stage occurs as actinomycetes and
themophilic and thermotolerant fungi oxidize the cellulosic and related
materials.
3. The end product is characterized by a high cation-exchange capacity,
a narrow carbon-to-nitrogen ratio, elimination of offensive odors, and a
balanced mixture of nutrient elements suitable for use as a soil amendment.
4. The end product stimulates plant growth either when incorporated
into the soil prior to planting the crop or when applied as a surface dress-
ing to establishing sod.
5. Growth stimulation occurs over a very wide range of application, up
to and including using pure compost as the rooting medium.
6. Because of the very wide range of useful application rates, the end
product can be used economically at low rates to provide nutrients and im-
prove soil physical properties or it may be used at very high rates where it
is desirable to use the soil as a sink in a waste disposal system.
7. The total yield, fruit size, flavor, and nutritional quality of
tomatoes grown with the compost are all excellent; both in the greenhouse
and in the field. Fruit ripening may be delayed by a few days where compost
is employed.
8. The process appears to be economically attractive to investors. It
definitely offers an excellent means of waste control and disposal to animal
growers. This would be especially true where there are concentrations of
animal populations such as occur in poultry or pork production facilities.
9. The entire process involves the production and use of a valuable
material from two potential environmental pollutants and does not result in
the transformation of one form of pollutant into another form of pollutant.
When employed properly it is environmentally safe.
The following recommendations have been made in light of experience
gained during the research and evaluation phases of the grant.
1. It would usually be preferable to locate a composting facility as
1
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described herein at or quite near the site of origin of the animal waste
since it is easier, cheaper, and more sanitary to transport the much drier,
and virtually odorless carbonaceous material.
2. Mechanical mixing and forced aeration are required during the first
phase of the process. The exit gasses should be monitored for oxygen con-
tent which should not be allowed to drop below 5 percent concentration.
3. The moisture content of the mixture placed in the composter drum
should be approximately 50 percent for optimum fermentation conditions.
4. When the compost is incorporated in soil at very high rates, the
moisture infiltration rate may be excessive for a few days. Thus irrigation
may be needed until the plant roots become established. At moderate or low
rates of application this is not a problem.
5. A very satisfactory compost can be made using shredded paper as the
carbonaceous material. Some paper contains a large amount of clay sizing.
If such paper is used and high rates of soil application are employed, early
cultivation may be recommended to prevent the formation of a thin crust at
the surface of the soil. Again this is not a problem at moderate or low
rates of application.
6. An economic analysis is recommended before a commercial composting
operation is begun. An adequate, continuous supply of animal waste and car-
bonaceous materials must be assured. Adequate land area for the entire pro-
cess must be available. A satisfactory packaging, transporting, advertising,
and marketing system must be available. Finally, an adequately-sized market
for the end-product must exist within an economical hauling distance of the
production facility.
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SECTION 2
INTRODUCTION AND LITERATURE REVIEW
THE EXTENSIVE SOLID WASTE PROBLEM
Amounted Generated
According to Can We Conquer the Solid Waste Mountain? (Anon., 1968),
the per capita production of municipal refuse in the United States grew from
1.25 kg per day in 1920 to 2.04 kg per day in 1965. Presently, the refuse
production per capita is believed to be increasing at about four per cent
per year. The 150 million tonnes of solid wastes which were discarded na-
tionally in 1966 will, therefore, reach 236 million tonnes by 1976. The dis-
posable container, disposable tissue, disposable garment, and the many "dura-
ble" items combine to compound the nation-wide disposal problem.
Unfortunately, municipal refuse is only a part of the solid waste pro-
blem. Industrial and agricultural wastes also contribute greatly. Animal
wastes have become a particularly serious problem since the confinement of
many animals on a small area has become common. It is now quite common in
the hog industry to find confinement units which market 3000 to 10,000 hogs
per year and poultry ranches which house up to one million birds at one time.
In 1970 the population of farm animals was estimated to be in excess of 3.1
billion animals including 189 million cattle, sheep and swine; 310 million
hens; and 2.8 billion fryers (U.S. Department of Agriculture, 1970).
The volume of waste produced by these animals is equally large. Poultry
manure alone totals about 36 million tonnes annually. Cattle produce approx-
imately 64 kg of manure per day per tonne of live weight, and hogs average
7 kg per 100 kg of live weight. Farm animal wastes total about ten times the
current human wastes in the U.S.
Ultimate Goal of Recycling Waste
Whatever the treatment method employed, it must be realized that the
ultimate answer to the solid waste problem will involve the recycling of all
organic solid waste to the soil in a safe, hygienic manner. Ultimately, mere
attention must be given to the realization of this ideal. It is quite im-
possible for the human species to continue present rates of population in-
crease and per capita consumption of goods and simultaneously maintain an
environment in which waste products do not become inhibitory to life. There-
fore, consideration must be given to a treatment method for total recycling
of ail materials consumed and subsequently discharged.
3
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Composting is one such method for handling solid organic wastes. It
not only provides a means of disposing putrescible wastes, but the final
product may also be utilized as a valuable soil amendment.
Keller (1961) stated that the following effects should be attained
through the use of compost as a soil additive:
1. Improvement in soil structure with greater friability and pore
volume which results in improved moisture distribution and gas
exchange;
2. Increased retention of plant-available moisture;
3. Increased retention of plant nutrients due to chelation and ion-
exchange properties of humus;
4. Prevention of erosion because of improved soil structure; and
5. Promotion of plant growth by providing slowly available nutrients
and increased activity of the micro- and macro-fauna in the soil.
Depletion of soil organic matter in certain regions of high-intensity
agriculture is approaching a critical stage (Schatz, 1966). A low level of
organic matter causes low productivity in many soils. Chemical fertilizers
offer no solution to this problem. The solution is to replace the organic
matter in the soil.
Although addition of raw waste into the soil results in rapid decom-
position, humus in the soil is also decomposed. The total soil humus con-
tent is thus raised only a little or not at all. The high biological activ-
ity may also result in the fixing of plant nutrients and a depletion of oxy-
gen. On the other hand, properly treated compost increases soil humus con-
tent and provides plant nutrients in a slowly available form.
The potential markets for compost may be divided into two categories:
farm markets and specialty markets. Specialty markets include home gardens
and lawns, parks, golf courses, plant nurseries, flower and vegetable pro-
duction areas, etc. Partridge (1969) indicated that sales to farmers should
involve large volumes at low unit cost, while specialty market sale units
should be smaller and the unit price higher.
COMPOSTING
Engineering and Biological Aspects of High-rate Composting
Purpose of Mechanized Composting--
The purpose of mechanized composting is to accelerate the rate of solid
waste decomposition--by means of aerobic, thermophilic composting--so that
large amounts of waste may quickly be treated and disposed (Wylie, 1960).
This is accomplished through a high degree of environmental control. By
optimizing control variables such as nutrient supply, moisture content, tem-
perature, aeration rate, and acidity (pH), high rate composting can be accom-
plished.
Characterization and Routine Control Testing--
For rapid composting and stabilization of solid organic waste, it is
4
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necessary that the following three conditions exist during the composting
operation (Eckenfelder and McCabe, 1963):
1. The waste contains all the nutrient elements required for biological
growth, and in the proper amounts;
2. The environment is completely aerobic, so that there is always an
excess of oxygen in the system; and
3. The environment is optimum with respect to temperature and acidity
at all times.
Characterization (analysis) of raw waste material and routine control
tests provide the information needed to ensure that all the above conditions
are attained, and the system is operating at the peak of its efficiency. By
this means, the biological population may be kept in the phase of maximum
growth (Figure 1). The maximum rate of organic matter stabilization will
thus be accomplished.
Batch Composting--
Schulze (1962) confirmed that batch composting -- which is treatment of
a single collection of waste—proceeds through a series of four distinct
phases: 1) fermentation; 2) acid formation; 3) thermophilic activity; and
4) temperature decline. During the fermentation phase, complex organic mole-
cules (proteins, polysaccharides, fats, etc.) are hydrolyzed by extra-cellu-
lar enzymes to more simple compounds. These compounds are then further de-
graded to simple organic acids, such as lactic acid, acetic acid, and other
organic and inorganic compounds (Eckenfelder and McCabe, 1963). Snell (1960)
found that 35°C is optimum for these two phases of aerobic decomposition by
mesophilic organisms. However, when the temperature exceeds 45°C, thermo-
philic microorganisms develop and replace the mesophiles in decomposing the
waste material. The temperature range for thermophilic microorganisms is
usually reported as 45 to 70°C. As mentioned earlier, thermophilic micro-
organisms are very effective for rapid decomposition. Finally, as available
nutrients are deplenished and the temperature subsides, actinomycetes and
fungi become actively involved in the decomposition of cellulose and other
resistent carbon compounds.
Batch composting studies are quite useful in establishing the optimum
operating parameters for efficient and rapid decomposition. Gotaas (1956)
reported that the time required for composting depends upon several factors:
1. The initial carbon to nitrogen ratio;
2. The degree of mixing and particle size;
3. The moisture content; and
4. The maintenance of aerobic conditions.
In addition, efficient composting requires control of temperature, pH,
and recycle of seed compost. The following sections are devoted to a thor-
ough look at these operating parameters.
Carbon to nitrogen ratio--Microorqanisms utilize 30 parts of carbon for
each part of nitrogen (Gotaas, 1956). Therefore, an initial C:N of 30 would
seem most favorable for rapid composting. However, many forms of carbon are
not readily available for decomposition; carbon contained in cellulose and
5
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LOG
GROWTH
PHASE
MAXIMUM
STATIONARY
GROWTH
PHASE
DEATH
PHASE
LAG
PHASE
TIME
Figure 1. Growth phases in biological processes
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lignin, for example, is resistant to degradation. A C:N of greater than 30
might therefore be expected to be optimal. Initial ratios reported as opti-
mum generally range from 25 to 50.
Nitrogen loss in the form of ammonia is also affected by the C:N ratio.
Since conservation of nitrogen is an important objective of aerobic compost-
ing, the C:N ratio should be adjusted for maximum nitrogen conservation.
According to Gotaas (1956), there are three alternative phases in the rela-
tion of nitrogen supply and conservation to available carbon in biological
decomposi tion:
1. When the initial C:N ratio is low, nitrogen is lost as ammonia;
2. When the required amount of carbon to nitrogen for microbial utili-
zation is present, decomposition proceeds without much loss of ni-
trogen; and
3. When the initial C:N is high, nitrogen is conserved, but the rate
of decomposition is lowered.
When adding mature compost to soil, a C:N ratio of 20 is generally men-
tioned as the upper limit at which there is no danger of robbing the soil of
nitrogen. Therefore, the higher the initial C:N ratio, the greater is the
work required by the microorganisms to reach the ratio of 20. Therefore,
when other conditions are optimum, the rate of compost production is deter-
mined by the initial ratio of carbon to nitrogen. In addition, it must be
remembered that the total carbon and nitrogen in a material or mixture is not
the only important factor. The form and availability of these nutrients are
also very important to the rate of composting and nitrogen conservation.
Moisture content--The moisture or water content of a compost material is
important because of the essential role of water in the metabolism of micro-
organisms and indirectly in the supply of oxygen. The optimum moisture con-
tent for aerobic composting of municipal refuse lies in the range of 40 to
60 percent.
Schulze (1961) determined the relation between moisture content of mu-
nicipal refuse and activity of the microorganisms involved in composting.
He measured the biological activity in terms of the rate of oxygen consump-
tion (Figure 2). At 10 percent moisture, no measurable oxygen uptake was
found. Even at 20 percent moisture, the consumption was practically negli-
gible. However, from this point the rate of oxygen consumption increased
rapidly with moisture to a maximum at a moisture content of 60 percent.
The results of Schulze clearly indicate two extremes:
1. Too little moisture deprives the microorganisms of water needed
for metabolism; and
2. Too much moisture displaces air by filling free pore space, thereby
inducing anaerobic decomposition.
Moisture content affects nitrogen consumption, but to a much less extent
than the C:N ratio or acidity (pH). Ammonia escape increases as the moisture
decreases to below 40 percent (Gotaas, 1956).
7
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Figure 2. Relation between moisture and oxygen uptake rates (Schulze, 1961)
Aeration—Aerobic organisms require free oxygen just as they require
moisture and food. Oxygen is normally provided by either, or a combination
of, forced aeration and mechanical stirring. Schulze (1962) found that with
thermophilic composting a continuous air supply of 0.30-0.71 m^ per day per
kg of volatile solids was needed. Insufficient air caused the temperature
to decrease sharply. At the other extreme, continuous mixing and over-aera-
tion also decreased temperature and tended to reduce moisture by increased
evaporation. Partridge (1969) found that the maximum air requirement for
optimum composting is 2.6 m3 per day per kg of volatile solids.
In studies conducted by Schulze (1960), the actual oxygen consumption
rate varied from one to five mg 02 per g initial volatile solids per hour
for a temperature range of 35 to 65°C. Translated into aeration require-
ments, 0.39 m3 of air per kg of volatile solids per day would be needed
during the period of peak demand. Obviously, in order to maintain highly
aerobic conditions, considerably more oxygen must be provided than is con-
sumed. Adequately aerobic conditions have been reported at oxygen concen-
trations ranging from 10 percent to as low as 2 percent (Grub et al., 1970;
Willson, 1971). The 2 percent figure has been challenged (Willson, 1971).
Aeration and stirring adversely affect nitrogen conservation. However,
if the initial C:N ratio is sufficiently high and the pH value sufficiently
low, the nitrogen losses should be small.
Temperature--The response of temperature during the four phases of
batch composting has been mentioned earlier. The high temperature during
the thermophilic phase of composting represents energy in excess of that re-
quired by the microbes for maintaining metabolic reactions. Gotaas (1956)
E
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(XI
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0 10 20 30 40
PERCENT MOISTURE
50
60
70
80
8
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showed that under aerobic conditions as much as 674 kcal of heat may be re-
leased per gram-mole of glucose decomposed. It is important, therefore, to
maintain an aerobic condition and its accompanying high release of energy
which promotes rapid decomposition of solid waste.
There is a strong linear relation between temperature and oxygen con-
sumption rate (Schulze, 1960, 1962). The higher the temperature, the great-
er is the oxygen uptake (Figure 3). An increase of 10°C between 35 and 65°C
produced a doubling of the oxygen consumption rate (i.e., Q]q = 2). The re-
sults leave no doubt that at temperatures in the thermophilic range, oxygen
consumption rates are considerably higher than at temperatures in the meso-
philic range. The general concept that thermophilic temperatures are con-
nected with a higher rate of compost stabilization is therefore correct.
0 10 20 30 40 50 60 70
TEMPERATURE (°C)
Figure 3. Relation between temperature and oxygen uptake rates (Schulze,
1962)
However, at very high temperatures (above 70°C), the rate of oxygen
consumption begins to decrease because of the thermal inactivation of micro-
organisms. An effort should be made to maintain the temperature between 55
and 65°C.
The maintenance of thermophilic temperature for several hours should
render the final compost free of all pathogenic microorganisms as a result
of thermal kill alone (Gotaas, 1956). Aside from temperature, however, it
is probable that biological antagonisms in the composting material also aid
9
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the destruction of pathogenic organisms and parasites. Evidence indicates
that high temperatures are most important and that where thermophilic tem-
peratures are maintained, pest destruction is complete.
High temperature increases volatilization and escape of ammonia (Hashi-
moto and Ludington, 1971). However, little can be done to prevent this ex-
cept to avoid temperatures above 70°C, where bacterial activity is retarded
and ammonia accumulates. If other factors conducive to nitrogen conserva-
tion are maintained and the temperature is below 70°C, the nitrogen loss will
be smal1.
Acidity--The optimum acidity for microorganisms involved in high-rate
composting generally lies between pH 6.5 and 7.5. Unless the compost material
is buffered, however, the acidity will normally vary as shown in Figure 4.
In general, the compost material should never be allowed to exceed the acid-
ity range of pH 4.5 to 9.5.
Conservation of nitrogen is very much pH-dependent. The pH effect on
the potential for nitrogen loss as NH3 is considerable. The NH4-NH3 equili-
brium shifts as follows:
pH Equilibrium Percent NH3
6 0.1
7 1
8 10
9 50
Toward the end of the thermophilic period, when the compost is near pH 9.0,
the potential for the loss of nitrogen as ammonia becomes appreciable. How-
ever, in the latter (cooler) stages of composting, most of the remaining in-
organic nitrogen should be in either nitrite or nitrate form. There should
not be an excessive amount of nitrogen present as ammonia.
9
8
7
6
5
7
4
6
2
3
5
TIME (days)
Figure 4. pH variations in batch composting
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Recycle of seed compost—Experience has shown that recycling relatively
small amounts of active compost material appreciably reduced lag periods
associated with batch composting. This is accomplished by the placement of
aclimatized microbes in the raw waste, thus reducing the time required for
the correct organisms to develop. Recycling of one to ten percent of seed
compost is normally sufficient. It has been found (Bell, 1969), however,
that even 10 percent of old compost in the mix does not appreciably reduce
the lag period. The material must be active.
Continuous Composting--
Schulze (1962) demonstrated that under properly controlled conditions it
is possible to operate a composting process continuously in the thermophilic
phase. His procedure of operation eliminated the lag period associated with
the two initial phases of batch operation and provided rapid decomposition of
the waste. After the initial charge of waste material reached the thermo-
philic phase, he maintained the thermophilic process by the daily addition of
raw material and daily removal of decomposing material. He stated that under
equilibrium conditions, the weight of material removed should range between
65 and 80 percent of the weight of raw waste added.
Degree of Compost Maturity--
If conditions favor decomposition (nutrients, pH, O2, etc.) the presence
of much available carbon (large supply of energy) results in an intensive
decomposition during which resistant carbon in the form of cellulose and
lignin is also attacked to some extent. When the supply of readily available
carbon is exhausted, the energy supply, and therefore the decomposition in-
tensity, is reduced. At this point, a degree of stabilization has been
reached in which the compost is designated as being mature (Davey, 1954;
Spohn, 1969). According to Keller (1961), determination of "degree of matu-
rity" is accomplished by visual observation, by the course of decomposition,
or most accurately by chemical analysis.
Raw organic waste material undergoes extensive changes in physical
appearance during decomposition. The color and structure of the initial
material generally disappear. Mature compost has a brown-black color and a
friable texture. In addition, the rancid or putrid odor or raw organic waste
disappears during composting, and the mature compost smells much like forest
humus. From the standpoint of determining compost maturity, however, it
should be mentioned that there is danger of erroneous interpretation. Com-
post which has undergone only a brief period of decomposition often looks
much like a mature compost although it is still far from ripe (Spohn, 1969).
Provided favorable conditions exist, raw waste passes through character-
istic stages when composted. Among the variables which may be monitored to
follow these stages are temperature, pH, and oxygen consumption. Temperature
is the best single indicator of the progress of batch composting. A tempera-
ture decline which has followed the typical normal steep rise and sustained
high plateau is a good practical criterion for judging when a compost is ma-
ture enough for use, although some additional curing may take place at lower
temperatures (Bell, 1969). In addition, oxygen consumption values which have
decreased from the peak values of the thermophilic phase are also good indi-
cators of batch compost maturity. Schulze (1961) found, for example, that
11
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the oxygen consumption is five to ten times greater in the intensive, as
compared to the mature, stage. Finally each type of compost has a charac-
teristic pattern of changes in pH values which will indicate to some extent
its stage of maturity.
Chemical analysis is the primary method of determining compost maturity
in continuous operations. The most important parameters are the ratio of
carbon to nitrogen (C:N ratio), chemical oxygen demand (COD), total volatile
solids, percentage ash, nitrite/nitrate nitrogen, percentage cellulose and
lignin, and cation-exchange capacity.
1. The C:N ratio has been discussed in a previous section of this re-
port. At that time it was mentioned that initial ratios reported
as optimum range from 25 to 50. The C:N ratio also serves as an
index of maturity for a compost material from the standpoint that a
mature compost has C:N ratio values between 10 and 20. However, the
C:N ratio value is only an indication of degree of maturity when the
carbon and nitrogen contents exist in available form in which they
can be assimilated by microorganisms.
2. The COD determination provides a measure of the oxygen equivalent of
that portion of the organic matter in a sample that is susceptible
to oxidation by a strong chemical oxident. An 85 percent reduction
in COD from raw waste to finished compost gives good reliability for
determining compost maturity.
3. Total volatile solids and percentage ash are determined upon combus-
tion of a sample in a muffle furnace at 600°C. Reduction in vola-
tile solids from a raw waste to mature compost ranged from 37 to 45
percent (Schulze, 1962). The average percentage ash in matured com-
post was about 1.5 times greater than that in the raw waste. The
actual loss figure would vary with the nature of the residue being
composted.
4. Nitrogen in organic compounds is released upon microbial decomposi-
tion as ammonia (NHo). The majority of NH? is either assimilated
by organisms or oxidized to N02~ and then NO3". Accumulation of ni-
trate nitrogen is, therefore, an indication of maturity.
5. Determinations of the cellulose content and its percentage of the
total organic matter at various degrees of composting give a good
index for intensity of decomposition and dearee of maturity (Davey,
1955; Keller, 1961).
6. An increase in lignin content and a decrease in the methoxyl content
of the lignin also give estimates of the stage of decomposition
(Davey, 1955).
7. Cation-exchange capacity (CEC) increases during decomposition. It
is an important characteristic when compost is used in soil. In
compost which contains only small amounts of soil or other mineral
matter, the CEC should approximately double as the compost matures.
PRODUCT EVALUATION
The Soil as an Animal Waste Disposal Medium
Regardless of the uniqueness of the solution to animal waste management-
12
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disposal problems, one factor is common to most solutions--the soil is the
ultimate disposal medium (Loehr, 1972). The function of integrating the soil
with animal waste disposal is two-fold: (1) Animal wastes are applied to the
soil for nutrient utilization for crop production at optimum-use-efficiency;
and (2) To apply animal waste at such rates that the practice becomes pri-
marily one of disposal without contributing to pollution (Webber and Lane,
1969). Animal wastes are organic in nature and serve as carbon, energy, and
nutrient sources and waste pre-treatment products for the biological fraction
of the soil. The biological fraction of the soil is composed of very large
populations and varieties of microorganisms. These microorganisms stabalize
animal waste by converting the waste to a higher oxidation level; for exam-
ple, reduced carbonaceous materials such as cellulose would be converted into
CC>2 and other nutrients are converted into microbial tissue. Except for ni-
trogenous materials, the higher the oxidation level the lower the pollution
potential for animal waste. The biological fraction of the soil combined
with the large area of reactive surfaces and other physical and chemical pro-
perties of the soil give it a tremendous capacity to assimilate organic waste
materials (Bohn and Cauthorn, 1972). However, there are several factors that
must be considered if the soil is to be effectively utilized as the ultimate
disposal medium for animal waste.
There are two basic alternatives. One is to employ the soil strictly
as a sink (Loehr, 1972). The primary objective of this alternative is to add
waste materials to the soil until an equilibrium is established between the
degradation capacity of the soil and waste application that is below the
threshold of environmental contamination by the wastes. This alternative may
be important where land areas are limited for waste disposal (Loehr, 1972).
Employing animal waste as an amendment to increase the productivity of
the soil is the major objective of the second alternative. This alternative
includes the addition of animal waste to the soil only to the point that
physical and chemical properties are modified or enhanced to obtain a more
optimum growth medium for plants.
Either of these alternatives will require intensive management to re-
duce the potential for environmental contamination from animal waste. The
second alternative may be more practical for long term applications of animal
wastes to the soil. This alternative utilizes plants as a sink for the re-
moval of the products derived from the degradation of animal wastes such as
inorganic nutrients. The first alternative allows these degradation products
to accumulate and remain in the soil. Long term, repeated applications under
such a system might reduce the effectiveness of utilizing the soil as a dis-
posal medium without environmental contamination.
Another factor to be considered in utilizing the soil as a disposal
medium is to distinguish between "the soil" and a specific soil type. Vari-
ability is a major characteristic of individual soil types. This variation
will influence the applicability of utilizing specific soils for animal waste
disposal. "The soil" may be defined as a biochemically weathered upper por-
tion of the earth's crust. "A soil" is a subdivision of the soil with well-
defined physical, chemical, and biological properties (Buckman and Brady,
13
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1969). The physical, chemical, and biological parameters of a soil will de-
termine the applicability of utilizing it for animal waste disposal. Envi-
ronmental factors including rainfall, drainage, vegetation, temperature, and
topography will also exert a modifying influence on utilizing a soil for ani-
mal waste disposal.
Soils in North Carolina range from poorly drained organic soils to ex-
cessively drained deep sands to clay. Topography ranges from relatively flat
areas to steep mountain slopes. Both mesic and thermic soil temperature re-
gimes exist. Rainfall varies from 112 cm to 203 cm with a statewide average
of approximately 127 cm per year (Lee, 1955). These factors will exert a
modifying influence on the degradation of animal waste by land disposal. For
example, Wilkes County is a major poultry producing county in North Carolina
and, consequently, generates large quantities of poultry waste. Part of
Wilkes County is in the mesic temperature region and the cool climate will
reduce microbial activity, thereby, reducing the assimilation of poultry
waste into the soil. The topography is generally rolling to mountainous
which reduces the land available for poultry waste disposal. By contrast,
Duplin County, which generates approximately the same amount of poultry
waste, is in the thermic region which will allow more rapid degradation of
poultry waste added to the soil and is relatively flat. On a percentage
basis more land is available in Duplin County for poultry waste disposal when
topography is considered. It is obvious that if guidelines are established
for land disposal of animal waste, that all these complexities must be con-
sidered.
Integrating Plants into a Compostinq-Soil Disposal System
Animal wastes contain many nutrients essential for plant growth. How-
ever, due to potential water contamination and the ensuing health hazards
associated with NO3-N, effective management of the nitrogen fraction is of
primary concern with respect to land disposal of animal wastes. The nitrogen
contained in animal waste and its removal from soil by plant uptake is basic
to all land disposal-plant growth systems.
Poultry manure has the highest concentration of nitrogen and other plant
nutrients among animal wastes (Taiganides, 1964). This indicates that both
the potential for environmental contamination and plant response per unit of
waste is greatest for poultry manure. The nutrients contained in animal
manures can be and are utilized effectively by crop plants. Use of these
nutrients constitutes a valid link in the recycling process of animal wastes
(Heald and Loehr, 1971). The opportunities to recycle and use waste are
enormous and society will increasingly demand the adequate utilization of
these wastes since they are a valuable part of our national resource (Murphy
et al., 1972). Composting, land spreading, and crop plant production offer
a set of sequential steps that are compatible with the ideals of conserving
and ultimately recycling animal wastes. Composting results in the conserva-
tion of plant nutrients in animal waste. Land spreading of composted mate-
rials enhances the soil as a growth medium for plants. Crop plants can be
integrated into this system to remove nitrogen and other nutrients with pol-
lution potential and simultaneously produce a marketable or useful product.
14
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Selection of plants to be integrated into animal waste disposal systems is
largely dependent upon site selection, the use and value of the harvested
crop, labor requirements for crop management, and the amounts and patterns of
nutrient utilization by the crop. From a nutrient recycling point of view
the last criterion is of major importance (Reed, 1972; Webber and Lane, 1969).
Many different field crops have been successfully used in land disposal
of wastes and recycling systems. Reed (1972) listed eleven crops that can be
integrated into animal wastes--forage operations. Papanose and Brown (1950)
indicated that many vegetable crops can be adequately grown with poultry
manure as a fertilizer. Although positive crop responses have been produced
with properly composted solid waste employed as a soil amendment (Davey,
1953, 1954; Gray, 1970; Hart, 1970; MacDonald and Dunn, 1953; Tacquin, 1965;
Wolfe and Dunn, 1953), little information is available concerning agronomic
crop response to composts integrated into animal waste disposal-piant sys-
tems. Previous investigations indicate that field crop response to composts
will vary according to the nature of the compost, rates of application, and
characteristics of the crop and soil. These parameters must be considered
before composts can be effectively incorporated into a system that is con-
sistent with the two-fold objective suggested by Webber and Lane (1969)--max-
imum application of waste materials for disposal and efficient nutrient up-
take by plants without secondary environmental contamination.
The most efficient method of removing nutrients is to select a plant
that has a high nutrient absorption and a large part of the plant is removed
from the site after the growing season. The amounts of nutrients removed
through plant uptake are the amounts removed through harvesting of at least
a part of the plant. The quantity of element removed per hectare depends not
only on the content of the nutrient in the part of the crop that is harvested
but also on the total amount of dry matter removed. Nutrients accumulated in
plant parts not removed by harvest will remain on the disposal site. Plant
composition and yield vary widely; therefore, different amounts of nutrients
are removed by different plant species. Many investigators suggest that corn
or a forage crop be employed for nutrient removal (Reed, 1972; Webber and
Lane, 1969). This is largely due to the ease with which these crops can be
worked into a livestock feeding program. Corn will generally require 180-
190 kg of nitrogen per hectare (Barber and Olson, 1968; Chandler, 1960). Ap-
proximately 60 percent of this nitrogen will be removed from the soil when
the grain is harvested leaving 40 percent to be returned to the soil in veg-
etative residue. Other grain crops take up less nitrogen, thus decreasing
the amounts removed from the disposal site (Reed, 1972). Coastal bermuda-
grass utilized for lawns or as forage and hay crops in North Carolina, can
remove up to 640 kg of nitrogen per hectare per year at yields of 22.4 tonnes
per hectare (Wagner and Jones, 1968). A large portion of the crop would be
removed from the disposal site by harvesting. Vegetable crops are an alter-
native for removing nutrients from amended soil. Vegetable crops include
many species that have exceedingly high rates of nutrient absorption. Cel-
ery, Producing 168 tonnes fresh weight Der hectare, may utilize up to 336 kg
of nitrogen of which 90 percent is removed from the disposal site in the pro-
cess of harvesting. In the leafy vegetable crops practically all the nutri-
ents are removed from the land. Tomatoes, producing 67 tonnes of fruit per
15
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hectare, will utilize 280 kg of nitrogen. Approximately 70 percent of the
nitrogen will be removed leaving 30 percent to be returned to the disposal
site (Lorenz and Bartz, 1968). It would appear that vegetable crops would
result in a greater potential for removal of nutrients from animal waste from
soil than corn or small grains and most forages.
In order to successfully utilize crops with high rates of nutrient up-
take, a compost-soil medium must be able to supply large amounts of nutrients
at the times of nutrient stress and in a form available for plant uptake.
Composts are low analysis organic fertilizers. Toth and Gold (1971) suggest
that an ideal compost contains approximately 2.5-3.5 percent total nitrogen,
0.4-0.7 percent phosphorus, and 0.8-1.2 percent potassium. Not only do com-
posts have low nutrient content but the forms of nutrients in compost are not
generally readily available for plant uptake. A major portion of the nutri-
ents in composts are in an organic form. Plants take up nutrients primarily
in their inorganic forms (Tisdale and Nelson, 1976); therefore compost nutri-
ents must be mineralized (converted from organic to inorganic forms) to be-
come available for plant growth. Composts are considered to be slow-release
fertilizers due to this characteristic. Mineralization is affected by the
microbial population of the soil, the physical and chemical properties of the
soil, and the climate. The rate of mineralization will be a major factor in
nutrient availability from compost amendments.
Because of the nature of composts (low analysis, organic, and slow re-
lease fertilizer), high rates of application have to be employed to supply
nutrients needed by high yielding crops. Yet, a balance between crop selec-
tion and rate of application of compost must be maintained. Nutrients, in
excess of crop requirements, even though initially in the organic form, may
become subject to leaching after mineralization has occurred (Webber and
Lane, 1969). Rate of application of compost and the rate of mineralization
will determine the supply of nutrients to field crops. From 34-112 tonnes
of compost per hectare per year are necessary for crop production (Hart,
1970). Some crops with exceedingly high rates of nutrient uptake may require
even higher rates of compost applications.
Perennial crops will require nutrients to be available every day of
their growth cycle to assure that nutrients will not be limiting (Wagner and
Jones, 1968) whereas, crops such as celery, corn, and tomatoes exhibit short
periods of extremely high nutrient demands (Lorenz and Bartz, 1968). In the
case of celery which has a growth period of 150 days from seeding to harvest,
it has been found that approximately 2 percent of the growth and nutrient up-
take occurred during the first half of the growing period and more than half
of the nutrients were taken up during the last three weeks of growth. A
similar pattern occurs with corn and tomatoes during grain and fruit forma-
tion and maturation (Chandler, 1960; Lorenz and Bartz, 1968; Ward, 1964).
This situation of nutrient uptake may be described as periods of low and high
uptake. Composted amendments must be able to adequately supply these nutri-
ent demands for optimum plant growth. The rate of compost application will
largely determine the success of this.
16
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Little research has been focused on high rates of compost application to
agricultural crops for waste disposal purposes. Integrating compost materi-
als into the production of crops with high market value which are heavy
nutrient feeders should include an adequate evaluation of a composting-land
disposal-plant system as a means of animal waste disposal. If composts are
able to produce adequate yields of high market value crops with no secondary
environmental contamination, then such a system becomes more feasible as a
solution to animal waste disposal problems. Until the present, this systems
approach remained an untested, hypothetical solution to most animal waste
disposal problems.
17
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SECTION 3
THERMOPHILIC COMPOSTING
The primary steps in the investigations being reported are summarized
below:
1. Sawdust and poultry manure were collected separately, analyses of
each were performed to determine their moisture, pH, ash, and nutri-
ent contents;
2. The wastes were weighed, combined, and mixed to a uniform mass by
hammer mill;
3. The mixture was subjected to an aerobic, thermophilic composting
process;
4. The batchwise decomposition was followed by measuring temperature,
oxygen uptake, pH, moisture content, ash, and loss of nitrogen;
5. After the thermophilic phase, the total amount of decomposition was
determined on a weight basis;
6. Holocel1ulose content and cation-exchange capacity were evaluated
to determine what effect, if any, a secondary curing stage might
have on final compost maturity; and
7. After completion of the batch studies, the composter was fed daily
and the process studied in continuous operation.
EXPERIMENTAL ARRANGEMENT
The central unit of equipment in the investigation was a 1.22 m capac-
ity composter, which was custom-fabricated by Aeroglide Corporation, Raleigh,
North Carolina. The composter consisted of a rotating drum reactor which was
mounted on a central shaft with a frame support (Figure 5). The reactor has
a chain-sprocket drive powered by an electric motor. An electric timer and
relay switch provided intermittent rotation. Other than entrance and exit
air ports the drum reaction chamber was a closed system with respect to mass
transfer. Heat losses were minimized by a 2.5 cm layer of styrofoam insula-
tion which was taped over the ends and sides of the drum. Two doors located
on the side of the drum were provided for addition and removal of material.
During operation, these doors were closed by a hinged cover with a fitted
rubber gasket.
Accessory equipment included an air compressor capable of delivering
1.2 1/s continuously, an airflow meter having a capacity of 1.9 1/s, ther-
mister probes and temperature recorder, and galvanic cell oxygen analyzer for
residual oxygen analysis. An acid trap was added to absorb evolved ammonia
for nitrogen-loss determinations.
18
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oxygen
ANALYZER
ROTAMETER _
GENERAL SERVICE
GAS METER
INSULATED
DRUM REACTOR
MOTOR
0
GEAR
SYSTEM
FILTER
M ?
o°
o
o
AIR
COMPRESSOR
ELECTRIC TIMER
o
[o o.
1 PROBE
-C±3—
NH3 TRAP
TO
ATMOS
TEMPERATURE RECORDER
Figure 5. Diagram of the composting system
-------
Analytical work was centered in the Sanitary Chemistry and Biology
Laboratory of the Civil Engineering Department at North Carolina State Uni-
versi ty.
EXPERIMENTAL PROCEDURE
Waste Preparation and Analytical Methods
Sawdust for this investigation was several years old and included mostly
southern pine species; 75 percent or more of which was loblolly pine (Pinus
taeda L.). This sawdust was stored at the compost site until needed. Poul-
try manure was donated by the Poultry Science Department at North Carolina
State University, and was collected in a fresh state as needed.
In preparation for each experimental run, the sawdust was partly air-
dried. By this means moisture contents of 55 to 60 percent were obtained for
initial combined waste mixtures. Schulze (1961) reported an optimum moisture
content of 60 percent for the composting process. The sawdust and poultry
manure then were weighed, samples for analysis were taken from each, and then
were mixed to a reasonably uniform condition by passage through a hammer
mill. A range of initial C:N ratio values from 20 to 45 was studied during
the batch runs.
Characterization tests were conducted for each batch and continuous run
to establish that all nutrient elements were present in adequate amounts for
composting. The testing methods were:
1. Carbon was determined by absorption with the semi-automatic Coleman
33 Carbon-Hydrogen Analyzer;
2. Nitrogen was determined with the semi-automatic Coleman 29A Nitrogen
Analyzer;
3. Phosphorus was determined colorimetrically by the stannous chloride
method (Standard Methods, 1965, p. 234);
4. Potassium was determined by flame spectrophotometry according to the
procedure in Standard Methods (1965); and
5. Calcium and magnesium were determined by atomic absorption spectro-
photometry.
In addition, moisture content, ash, volatile solids, and pH were in-
cluded in the characterization work. An electric drying oven at 75°C, muffle
furnace at 600°C, and pH meter were used in these determinations.
Batch Reaction Study
Except where otherwise specified, each experimental run was standardized
according to the following conditions:
1. The reaction chamber was filled to about two-thirds capacity;
2. Microbial seeding of each batch was accomplished by recycling 2 per-
cent (by weight) of "seed compost" (material from the just com-
pleted batch). The seed compost should contain a wide variety of
microorganisms specially adapted to the aerobic, thermophilic
20
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conditibns;
3. Oxygen consumption and compost temperature were measured four times
daily throughout the run;
4. Decomposing waste was sampled twice daily and tested for moisture
content, ash, volatile solids, and pH;
5. Evolved ammonia was absorbed in a phosphoric acid trap located in
the effluent gas line for nitrogen-loss determinations;
6. The runs were terminated when oxygen uptake and temperature indicat-
ed a sustained decrease in microbial activity; and
7. Finally, the compost product was weighed for determination of total
percentage decomposition.
In addition, the agitation rate (composter drum rotation) was adjusted to 1
rpm. Intermittent agitation of 2 min/4 hr was applied to runs 1 through 10;
whereas, the interval was 2 min/15 min for runs 11 and 12. Continuous agita-
tion was applied to runs 13 through 16.
The oxygen consumption rate, which is an accurate indicator of process
activity was used to follow the decomposition process. It was determined by
measuring the residual oxygen content of the effluent gases at constant air
input. For example, a concentration of 5 percent oxygen in the exhaust in-
dicated that 16 percent (by volume) of incoming air had been consumed as
oxygen.
Continuous Operation
After completion of the batch studies, a series of continuous-run opera-
tions was undertaken. The materials used during this phase of the program
included poultry manure, swine manure, sawdust, and shredded paper. The
equipment was the same as that used during the batch studies. The primary
steps in the operation of the process are summarized below:
1. Sawdust, poultry manure, swine manure, and waste paper were collect-
ed separately when needed and periodic analyses of each were per-
formed to determine their moisture and ash content and acidity (pH);
2. The wastes were weighed, combined (manure-sawdust or manure-shredded
paper), and mixed to a uniform mass;
3. The mixture was subjected to an aerobic, thermophilic composting
process with periodic removal of part of the material and addition
of fresh mixture;
4. The continuous process was monitired by measuring oxygen use, tem-
perature, pH, moisture content, and ash content; and
5. The output from the drum was stored in a pile and monitored for fur-
ther biological activity.
The sawdust was partly air-dried before each run. The waste paper was
shredded and sprayed with water to increase its moisture content as well as
the weight-to-volume ratio. Neither the poultry waste nor swine waste need-
ed any pre-treatment. The raw materials were then mixed as evenly as possi-
ble with shovels and then run through a hammer mill to distribute the animal
waste more evenly through the sawdust. In the case of shredded paper the
mixture tended to choke the hammer mill and thus additional shovel mixing
21
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was done.
The waste mixture was fed into the composter drum and the doors were
closed tightly. The drum was rotated continuously at 1 rpm. Air was suppli-
ed at an average rate of 0.9 1/s. The exhaust air was passed through the
phosphoric acid trap where any ammonia in the exhaust was removed. The tem-
perature was measured at two ports in the drum. Samples were taken at vary-
ing frequency and tested for acidity (pH), bulk weight, percent moisture,
percent volatile solids, and percent ash. The oxygen concentration in the
exhaust gas was also monitored.
When the temperature started to decline, a portion of the compost was
removed and fresh mix was added. The neutralized phosphoric acid was added
to the compost pile so as to return the nitrogen lost during active degrada-
tion and to supplement the phosphorus content of the compost.
Secondary Curing
After discharge from the reactor, the compost was placed in storage.
Periodically, the compost was turned and remoistened. It was presumed that
the major breakdown of cellulose occurs during this immediate post-thermo-
philic stage. However, no data were found in the literature to substantiate
this. Therefore, holocel1ulose content and cation-exchange capacity of the
initial sawdust, compost before storage, and compost after storage were eval-
uated to determine what effect, if any, a secondary curing stage might have
on final compost maturity.
RESULTS
Nutrient Studies
The most widely used parameter for assessing composting is the carbon-
to-nitrogen (C:N) ratio. It has been suggested that the optimum C:N ratio
ranges from 30 to 50. However, other nutrient elements are necessary for
proper organism metabolism. Sawyer (1956) reported that the nitrogen-to-
phosphorus ratio should be 5:1. Thus, the combined carbon-to-nitrogen-to-
phosphorus (C:N:P) ratio should be 30 to 50:1:0.2. Trace amounts of other
elements also are required for proper nutrition.
Table 1 lists the analyses of sawdust and poultry manure used in each
batch run. The average C:N:P ratio for the sawdust was found to be 290:1.0:
trace, while for the manure, it was 5.2:1.0:0.18. The C:N:P ratio for the
waste mixtures used in the batch runs ranged from 21:1.0:0.19 to 43:1.0:0.15.
The amounts of calcium, magnesium, and potassium were regarded as adequate.
Batch Composting
Aeration and Agitation Requirements-
Oxygen utilization determinations were made for each run except runs 3,
4, and 10 and the air supply rate was adjusted so that the exhaust gases
22
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TABLE 1
ESSENTIAL NUTRIENT CONTENTS OF SAWDUST AND POULTRY MANURE*
Carbon Nitroqen Phosphorus Potassium Calcium Magnesium
Run Date S.D.t P.M.t S.D. P.M. S.D. P.M. S.D. P.M. S.D. P.M. S.D. P.M.
1
4/10
47.7
34.8
0.135
6.83
<0.001
1 .47
0.050
0.85
0.075
2.50
0.025
0.750
2
4/18
3
4/24
48.5
35.8
0.103
6.44
4
5/1
5
5/14
48.9
37.1
0.130
6.95
t+
1 .23
0.046
1 .41
0.058
2.12
0.061
0.645
6
6/4
48.3
36.3
0.143
6.64
7
6/16
48.5
35.2
0.115
6.81
8
6/27
9
7/11
48.5
35.5
0.132
7.20
t
1.11
0.024
1.58
0.048
2.03
0.048
0.723
10
7/28
47.1
37.2
0.150
7.12
11
8/8
48.5
38.0
0.110
7.68
12
8/18
49.3
37.5
0.122
7.50
13
8/22
47.8
38.0
0.111
7.28
t
1 .21
0.057
1 .33
0.063
1 .74
0.055
0.734
14
8/28
50.4
36.0
15
9/3
49.9
37.4
16
9/11
48.7
36.3
0.116
7.54
Average
48.5
36.6
0.124
7.09
t
1 .25
0.044
1 .29
0.061
2.10
0.047
0.713
* All values are presented as percent oven-dry weight,
t S. D. (sawdust); P. M. (poultry manure); t (trace).
-------
contained at least 5 percent residual oxygen, by volume. The drum agitation
also was varied as previously indicated.
During run 10, it was determined that while the composter drum was not
being agitated (i.e. turning) the oxygen being supplied could not penetrate
to all parts of the composting mass. During runs 11 and 12, it was deter-
mined that in the first 2 min following the end of the agitation period, all
oxygen had been used up in the region of the reactor near the bottom.
The oxygen uptake for runs 5 and 15, which had similar C:N ratios may
be compared by reference to Figure 6. Run 15 had a substantially higher peak
oxygen uptake rate than did run 5. This peak also was reached much sooner.
Both batches were removed from the composter when their temperatures had
dropped to 42°C. Batch 15 required 139 hr while batch 5 required 210 hr for
the temperature to reach this point. The areas under the two curves are al-
most equal, thus indicating that the oxygen requirement was substantially the
same for both batches; however, the biological activity rate, as shown by the
oxygen utilization rate curve, was much greater in run 15 (Figure 6).
Changes in Acidity (pH) —
Acidity determinations (pH) were made twice daily during the course of
each batch run. The results of a typical run are presented in Figure 7. The
initial readings of the mixtures used ranged from pH 5.4 to 7.2. After an
initial lag period, all batches rose to a range of pH 8.5 to 9.0.
Those batches having the lower initial pH values required more time to
reach the thermophilic temperature range (above 45°C) than those having high-
er initial pH values. The length of the initial lag period did not affect
the total length of time required for composting as did the need for proper
aeration.
Temperature—
Figure 8 presents a typical temperature curve for a batch process. The
temperature remained in the mesophilic range (25 to 45°C) until the pH value
exceeded 7.0. The temperature then climbed rapidly to between 60 and 70°C,
where it remained for up to 30 hr. The temperature then began to decline
slowly until the composting batch again was out of the thermophilic range.
The length of time that the composting batch remained at this high tempera-
ture level depended on proper aeration as well as the amount of readily
available carbon, rather than the C:N ratio per se.
Carbon:Nitrogen Ratio-
Batches having an initial C:N ratio ranging from 21:1 to 43:1 were com-
posted. Figures 9 and 10 show the oxygen uptake rate and the cumulative
oxygen usage for runs having a low C:N (25:1) and a high C:N (40:1) ratio.
The results indicate that the batches having the lower C:N ratio had a high-
er oxygen usage which extended over a longer period. These batches also had
the higher manure-to-sawdust ratios.
The relationships between the volatile solids reduction, percentage of
manure in the composting batch, and the initial C:N ratio are shown in
24
-------
5.0
4.0
3.0
~ RUN *15 -C:N25
O RUN * 5 - C N23
UJ o
* "
ft
^ > 2.0
z
uj
id o
x <*
O E
150
180
120
210
90
30
60
TIME (he.)
Figure 6. Comparisons of decomposition rate for completely aerobic
and partly anaerobic systems
-------
10
9
8
7
6
RUN *15
5
150
30
120
0
60
90
TIME (hr)
Figure 7. Phases of batch composting as evidenced by
changes in acidity
80
70
60
50
40
30
120
90
150
60
30
TIME (hr)
Figure 8. Phases of batch composting as evidenced
by temperature
26
-------
5.0
4.0
3.0
C N 25-AVERAGE OF RUNS
<15 8 *16
2.0
C N 40-AVERAGE OF RUNS
X»I3 a *14
Z
CVJ
Q-
60
90
120
150
TIME (hr.)
Figure 9. Oxygen uptake rates during the course of decomposition of
C:N 25 and C:N 40 batch mixtures
-------
250
200
150
CM
O
100
r
50
~ C:N 25-AVERAGE OF
RUNS* 15 8*16
OC:N 40-average: OF
RUNS *138 *14
30
60
90
TIME ( hr. )
20
150
Fiaure 10. Total oxygen uptake as a function
of composting time
28
-------
Figure 11. The volatile solids reduction is seen to parallel closely the
percentage of manure. Two curves are presented for volatile solids reduc-
tion. The upper curvp is for early runs using relatively fresh sawdust; the
lower curve is for runs using sawdust that had been in storage at least 2.5
months longer than that used in the earlier runs.
The above data indicate that the majority of the carbon used as an
energy source during this portion of the process is derived from the manure.
If the carbon in the sawdust had contributed substantially to the available
carbon, the volatile solids reduction would not have paralleled the percen-
tage of manure curve in Figure 11 as closely as it did, but should have been
much closer to horizontal. The sawdust appears to be resistant to the micro-
bial action in the composter (see section on organisms associated with ther-
mophilic composting).
Moisture Content--
Quantitative determinations for optimum moisture content were not made.
The moisture contents of the initial batches ranged from 50.8 percent to 63.6
percent wet weight. It was noted that as the moisture levels increased above
60 percent, there was a tendency to form small balls. During the course of
a run, the moisture level did not vary by more than 1.2 percent. Apparently
volatilized moisture which was lost with the exhaust gasses was balanced by
the production of respiratory moisture.
Nitrogen Conservation--
Nitrogen losses ranged from 2.69 to 7.90 percent (Table 2). The results
indicate that the C:N ratio had little effect on the percentage N lost. The
losses were greatest in runs 6 through 9, where the agitation was least and
the aeration poorest. Runs 13 through 16 had continuous agitation and the
best aeration. It is thus concluded that the nitrogen conservation depends
more on the rate of biological activity than the C:N ratio in the range stud-
ied.
TABLE 2
NITROGEN LOSSES DURING THE COURSE OF DECOMPOSITION
OF SAWDUST AND POULTRY MANURE MIXTURES
Batch
Initial C:N
Final Acidity
N Loss
Ratio
(pH)
(%)
6
42
1
8.85
4.52
7
31
1
8.90
7.90
8
35
1
8.45
5.90
9
28
1
8.90
7.17
12
38
1
8.90
3.84
13
43
1
8.80
2.69
15
25
1
8.75
3.83
16
27
1
8.80
3.35
29
-------
O FRESH SAWDUST
~ OLD SAWDUST
A PERCENT MANURE
32
INITIAL C'N
20
Figure 11. Relationships between volatile solids reduction,
percentage manure, and initial C:N for batch
composting of sawdust and poultry manure mixtures
30
-------
Cellulose Degredation--
Results derived from the high-rate composter studies give evidence that
the holocellulose and lignin are resistant to microbial attack during this
phase. As the runs were completed, the compost was placed into storage.
During the storage period, fungi developed rapidly and began decomposing the
cellulose in the compost. The cellulose content did decrease during the
storage phase (Figure 12).
As the cellulose content decreased, the cation-exchange capacity (CEC)
of the compost increased (Figure 13). The final CEC of the compost was 67
meq/100 g. This is well within the range of a desirable soil additive.
Continuous Operation
In continuous composting, the lag phase found in the batch process was
not observed. The input-output frequency and the amount of exchange are im-
portant factors in the operation of the process.
The initial continuous run was started using sawdust and poultry waste.
However, the run was stopped after 10 days due to difficulties experienced in
obtaining sufficient poultry waste of known composition.
A continuous run was started using sawdust and swine waste. After the
thermophilic temperature was attained, a part of the composted material was
taken out every day and fresh mix was fed into the composter. The input-out-
put ratio was changed to find the maximum value that would maintain the ther-
mophilic stage without reverting to the initial lag phase. After 12 days,
due to the use of high input-output ratio continuously, the composter was
nearly full and free air-sapce became limiting. Consequently, the tempera-
ture dropped below the thermophilic range. No fresh mix was fed for 2 days.
On the 15th and 16th days, the feeding-removal process was repeated but the
temperature did not go above the lower thermophilic range. The composter
was emptied after a total of 475 hours of operation. The process was repeat-
ed twice more.
For the sixth run, poultry manure was used with shredded paper instead
of sawdust. The paper was a mixture of newsprint and glossy paper used in
magazines, mostly printed in black ink. It is assumed that the paper used
had the same average composition as the paper content in domestic refuse,
thus its chemical composition is assumed to be very close to that given for
"other combustibles" in Table 3.
Two batch runs were carried out with the shredded paper-poultry waste
mix. Each time, the initial mix had to be sprayed with some water in order
to bring the moisture content up to the level of at least 50 percent. The
continuous run was then started. Thermophilic temperatures were observed ex-
cept briefly, after each feeding. The drum was stopped and emptied after a
time of 1,245 hours had elapsed; an obviously successful continuous operation.
The different variables affecting thermophilic aerobic composting were
investigated during the batch studies and have been dealt with in detail in
31
-------
75
70
65
60
55
50
1
1
1—
1
-
¦A
V o
-
o
o
—O— _
o
1
1
'
L-
8
12
16
20
TIME (weeks)
Figure 12. Effect of storage upon compost maturity
as evidenced by holocellulose content
75
65
55
45
35
1
i
1
—1—
-
o
o
-
-
a °
o
-
/
-
i -
¦
1
1
8 12
TIME (weeks)
16
20
Figure 13. Effect of storage upon compost maturity
as evidenced by cation-exchange capacity
32
-------
TABLE 3
MEAN, STANDARD DEVIATION, AND STANDARD ERROR OF THE MEAN FOR THE CHEMICAL
COMPOSITION OF DOMESTIC REFUSE IN RALEIGH, NORTH CAROLINA *+
Component
Food wastes
Other combustibles
Mean
Standard
deviation
Standard error
of mean Mean
Standard
deviation
Standard error
of mean
Moisture
69.25
14.20
8.20
19.60
8.35
4.82
Acidity (pH)
5.70
0.17
0.10
Ash
11.74
3.60
2.08
4.11
0.91
0.52
Volatile solids
88.26
3.60
2.08
95.89
0.91
0.52
Protei n
12.10
2.88
1.66
1.15
0.17
0.09
Lipids
11.20
3.48
2.07
5.33
1.92
1.12
Crude fiber
13.03
8.00
4.78
56.83
5.15
2.98
Liquids
75.70
11.60
6.70
25.61
9.16
5.30
Calorific value
+ 853
12.58
7.21
901
2.23
1.29
Sulfur
0.16
0.01
0.01
1.06
0.05
0.02
Carbon
29.23
1.55
0.90
33.02
2.20
1.27
Ni trogen
1.92
0.28
0.16
0.20
0.03
0.02
Potassi urn
0.92
0.10
0.05
0.18
Phosphorus
0.28
0.38
0.02
0.12
0.02
0.01
C:N
15.40
3.36
1.94
178
8.10
4.67
* All values are in terms of percentage dry weight except percentage moisture and percentage liquid,
which are based on wet weight of the raw material, and pH and calorific values.
f From Partridge, 1969.
+ Kcal/kg dry weight.
-------
the earlier portions of this report. The trend of the variables in con-
tinuous composting are discussed below.
Temperature--
Temperature readings were taken frequently during the continuous com-
posting study. The rise and fall of temperature is directly related to the
oxygen uptake rates. In a typical continuous run using sawdust and swine
waste, it was noted that after the initial lag phase the temperature in-
creased to the thermophilic range (45 to 70°C) and stayed there most of the
time (Figure 14). The arrows in Figure 14 indicate the times at which com-
post was removed and fresh mix was added. At these times, there was a rapid
drop in temperature followed by a return to the thermophilic range beginning
fifteen minutes after the feeding. It is presumed that if the system were
devised so that the feeding and emptying were done continuously at opposite
ends of a drum, the fluctuation in temperature would be minimized. The tem-
perature variations were recorded in continuous runs using sawdust and poul-
try waste (Figure 15 and 16) and in a run using shredded paper and poultry
waste (Figure 17). Due to difficulties caused by ball-forming and with mois-
ture control and turn-over-rate, the temperature in this run was comparative-
ly lower even though the overall trend was the same as in the other runs.
Moisture--
Moisture content is a very significant factor in the functioning of the
composting process. According to Schulze (1962), the oxygen uptake rate in-
creases directly with the moisture content from a minimum of zero at moisture
contents below 20 percent to a maximum at a moisture content of 60 percent.
Above 60 percent moisture, there is a tendency to form small balls and the
composting rate decreases. During the continuous operation study, the mois-
ture content of the input mix ranged from 53.5 to 64.5 percent (Table 4). It
is noted that the moisture lost in exhaust gas is almost balanced by the
moisture produced by the biological process of respiration and thus the net
moisture content of the compost remained practically the same during the en-
tire run. The variation of moisture in the input mix and output compost in
a typical continuous run is shown in Figure 18.
Ash Content--
The percent fixed solids at any particular time is determined in part by
the rate of biological oxidation. In order to determine ash content, a
weighed sample is dried overnight at 105°C. After the dry weight is obtain-
ed, the sample is placed in a muffle furnace at 600°C for 3 hours. The
weight of fixed solids or ash is determined and the ash content is expressed
as percent of dry weight. The successive change of ash content in the input
mix and output compost in a typical continuous run with sawdust and poultry
waste is shown in Figure 19.
Acidi ty—
The input mix ranged from pH 5.4 to 9.05 and the output compost varied
from pH 5.95 to 9.3. The lower pH values corresponded to the use of animal
waste which was collected more than 24 hours prior to its use. After a lag
phase at the start of each run, most runs increased to be between pH 8 and 9.
It was also observed that whenever the input mix had a low pH value, it took
34
-------
80
FEEDING
70
60
o
50
oc. 40
30
20
RUN
500
400
300
200
100
TIME (hr.
Figure 14. Temperature variation during continuous composting with
sawdust and swine waste
-------
70
FEEDING
60
50
o
Ul
cr
=> 30
<
cr
UJ
RUN
350
250
300
400
200
150
100
50
Figure 15. Temperature variation during continuous composting with
sawdust and poultry waste
-------
80
FEEDING
70
60 -
50
40
30
20
RUN
900
600
700
800
500
TIME (hr.)
300
400
200
100
Figure 16. Temperature variation during continuous composting with sawdust
and poultry waste
-------
80
70
FEEDING
60
50
o
©
40
ui
-------
TABLE 4
VARIATION OF AVERAGE MOISTURE, ASH, AND VOLATILE SOLIDS CONTENT IN INPUT MIX
AND OUTPUT COMPOST IN DIFFERENT CONTINUOUS RUNS
Run No. Raw Percent Mositure Percent Ash Percent Volatile Solids
Materials ~ ~~
I.M. O.C. I.M. O.C. I.M. O.C.
1
S.D.
&
P.W.*
53.5
56.7
3.80
4.90
96.20
95.10
3
S.D.
&
S.W.
55.6
56.8
4.06
4.97
95.94
95.03
4
S.D.
&
P.W.
56.9
55.3
4.26
5.11
95.74
94.89
5
S.D.
&
P.W.
55.1
55.2
4.48
95.52
8
S.P.
&
P.W.
64.5
45.2
21 .13
25.52
78.87
74.48
* S.D. = Sawdust, S.P. = Shredded Paper, P.W. = Poultry waste,
S.W. = Swine waste, I.M. = Input mix, O.C. = Output compost.
-------
1
1
i
• i '
-
FEEDING
-
_
\ \ \
~
~ \ *
-
-
4 "%
— -*p~
' *" " ~ 4
-
-
0 OUTPUT
-
-
— —INPUT
-
-
RUN *4
-
1
i
i
1 1 1
ol I I I I I 1
50 100 150 200 250 300 350 400
TIME ( hr )
Figure 18. Moisture content variation during continuous composting with
sawdust and poultry waste
-------
X
-------
more time to reach thermophilic temperatures than when the value was high.
Whenever the pH value exceeded 9, there appeared to be increased loss of ni-
trogen as ammonia. The variation of pH values during a typical continuous
run is given in Figure 20.
Nitrogen Conservation--
The nitrogen losses from the composter are mostly a function of the
biological activity. During the decomposition process, any ammonia that es-
caped in the exhaust gas was captured in the phosphoric acid trap. The ni-
trogen losses for the continuous runs are presented in Table 5. The percent
nitrogen lost in the runs with sawdust and animal wastes ranged from 1.88 to
8.35 percent. The percent of nitrogen lost in the run with shredded paper
and poultry waste was calculated to be 20.2 percent which is strikingly high,
probably due to high total nitrogen content compared to total carbon content
resulting in high pH and escape of extra nitrogen as ammonia. Better control
of moisture (and thus physical condition of the mix) and turnover rate might
have helped. While calculating the nitrogen losses presented above, average
analysis of raw materials was assumed (Table 6).
Turnover Rate--
The turnover rate is defined here as the ratio of the output compost to
the total compost in the drum. Initially, only about one-third of the total
volume was replaced. However, in later studies, as much as two-thirds of the
composting mass was replaced satisfactorily. The weight of the output was
generally kept in the range of 60 to 80 percent of the weight of input mix in
order to allow for the oxidation of volatile matter. A high turnover rate is
significant in the sense that it tells us the minimum residence time neces-
sary for proper decomposition of materials in the composter.
Buikweight--
The bulkweight is generally represented as weight per unit volume; the
units being kilograms per cubic meter (kg/m^). According to Schulze (1962),
the moisture and free air-space considerations necessitate that the bulk-
weight of the raw feed material be kept between 400 and 480 kg/m^. During
the composting process, the volatile matter is oxidized and bulkweight of the
material generally increases. During the composting of animal wastes mixed
with sawdust, the analyzed samples showed that the bulkweight of input mix
ranged from 370 to 493 kg/m3 with an average value of 448 kg/m3. The bulk-
weight of the output compost, ranged from 456 to 564 kg/m3 with an average at
509 kg/m3. The variation in bulkweight of the input mix and output compost
during a typical continuous run is given in Figure 21.
Aeration--
The aeration rate in the composter varied from 0.6 to 1.2 1/s with a
value of 0.9 1/s used most of the time. Based upon earlier studies, it was
believed that this rate would meet the oxygen requirements of the composting
mass satisfactorily. There were some very small leakages in the system, but
overall the losses were minor and can be safely neglected.
42
-------
14
13
12
11
10
9
8
7
6
5
4
3
2
I
FEEDING
• WITHDRAW!.
+• — -ADDITIONAL FEED
RUN *8
100 200 300 400 500 600 700 800 900 1000 1100
TIME (hr.)
20.
Acidity variation during continuous composting with shredded paper
and poultry waste
-------
TABLE 5
NITROGEN LOSS IN DIFFERENT CONTINUOUS RUNS
Run No.
Raw Materials
Total Carbon
Total Nitroqen
Averaqe Acidity
(PH) (pH)
Nitrogen Lost*
(kq)
(kq)
I.M.
O.C.
(%)
1
S.D. &
P.W.+
70.8
1.76
8.78
8.57
5.21
3
S.D. &
S.W.
306.6
7.13
6.41
7.83
3.10
4
S.D. &
P.W.
346.9
10.43
8.27
8.82
1.88
5
S.D. &
P.W.
1091.6
38.14
7.15
8.35
8
S.P. &
P.W.
212.3
15.17
7.95
8.76
20.20
* Lost from the compost in the drum but captured in the phosphoric acid trap,
t S.D. = Sawdust, S.P. = Shredded Paper, P.W. = Poultry Waste,
S.W. = Swine Waste, I.M. = Input Mix, and O.C. = Output Compost.
-------
TABLE 6
ESSENTIAL NUTRIENTS AND MOISTURE IN RAW MATERIALS
C N P K Ca Mg Percent
Moi sture
Raw material Percent (oven-dry basis) (wet weight basis)
Poultry Manure
Lowest Value 34.8 6.44 1.11
Highest Value 38.0 7.68 1.47
Average* 36.6 7.09 1.25
Swine Manure
Average + 3.75
Sawdust
Lowest Value 47.1 0.103 Trace
Highest Value 50.4 0.150 <<0.001
Average 48.5 0.124 Trace
Shredded Paper +
Mean 33.02 0.20 0.12
Standard Deviation 2.20 0.03 0.02
Standard Error 1.27 0.02 0.01
of Mean
0.85
1.58
1 .29
0.024
0.057
0.044
0.18
1 .74
2.50
2.10
0.048
0.075
0.061
0.645
0.750
0.713
0.025
0.061
0.047
75.9
72.7
42.3
19.6
* After Walter N. Reed (1969).
t After Harold B. Gotaas (1956).
+ After Lawrence J. Partridge (1969). Assuming that the "Other Combustibles" part of domestic refuse
is mostly paper.
-------
70
60 -
50 -
40 -
» 30 -
cn
x
o
UJ
*
as
20 -
10 -
100
FEEDING
WITHDRAWAL
A- ADDITIONAL FEED
RUN *4
J I I 1—
X
120
140
160
180
200 220
TIME (hr)
240
250
280
300 320
Figure 21. Bulkweight variation during continuous composting with
sawdust and poultry waste
-------
Storage Effects on Compost Maturity
The finished compost was taken out of the composter and placed in heaps
in a storage room. The outer surface of the piles reached ambient tempera-
ture and lost moisture quickly. However, after approximately one day, the
temperature began to rise again at depths of 15 cm or more below the surface.
A light spray of water over the pile appeared to benefit the biological ac-
tivity causing further rise in temperature. For example, the temperature of
the batch compost composed of shredded paper and poultry waste was 30°C when
removed from the composter. It was stored in a pile and was sprayed lightly
with water. After 71 hours, the temperature reached 66°C. This typical
"heating phenomenon" is shown in Figure 22. It was noted that very high tem-
peratures, representing the upper range of thermophilic activity were obtain-
ed. A heavy growth of actinomycetes and fungi was observed in the pile.
After the temperature subsided, it would rise again temporarily when the pile
was turned and sprayed with water. However, the renewed biological activity
was not maintained. During the storage phase, there was no smell of ammonia
in the piles. On the average, after four weeks, the compost was "matured"
in the sense that, the biological activity had subsided and the compost had
obtained a dark color with an odor like that of forest humus.
Organisms Associated With Thermophilic Composting
The objective of the microbiological phase of this project was to char-
acterize the organisms involved in the composting process -- both in the
thermophilic and in the mesophilic stages. The organisms involved may in-
clude bacteria, actinomycetes, or fungi, and the predominance of each group
may change rapidly as composting proceeds. Few quantitative studies on the
organisms involved in composting have been done due to the lack of suitable
methods and assay media (Cross, 1968). Attempts were made therefore to eval-
uate media which might be useful in quantifying changes in the microflora.
This report summarizes the methods attempted, problems encountered, and re-
sults obtained.
Bacteria and Actinomycetes--
The method initially tested for the isolation and enumeration of bac-
teria and actinomycetes was the widely used dilution-plate technique. A
sample of freshly collected compost was dispersed in sterile water in a
Waring blender. Further dilutions were prepared from this suspension and
one-half milliliter aliquots of the appropriate dilutions were spread on nu-
trient agar plates which had been poured two days previously. The plates
were incubated at 47°C.
After several attempts using this technique, it became apparent that the
presence of motile bacteria frequently prevented the development of distinct,
countable colonies. These bacteria (Bacillus spp.) covered the entire sur-
face of the agar in 12-24 hours. Thus, other media or techniques were sought
which would permit accurate counting.
A low concentration of aureomycin inhibits bacteria, thus permitting the
growth of actinomycetes (Fergus, 1964). Also, Cross (1968) found Novobiocin
47
-------
80
70
60
50
40
30'
20
250
200
150
100
STORAGE TIME (hr )
50
Figure 22. Typical "heating phenomenon" evidenced by composted shredded paper
and poultry waste undergoing storage
-------
very useful in isolatinq Themoactinomyces. Therefore a spectrum of anti-
biotics was tested for their ability to restrict spreading colonies of bac-
teria and to inhibit either all bacteria or all actinomycetes so that each
group could be counted separately. The antibiotics tested and the concentra-
tions used are given in Table 7.
In general, none of the antibiotics tested were appropriate for general
use in an isolation medium. Polymyxin B was the most potent antibiotic used;
10 ppm eliminated all bacteria and actinomycetes. The only antibiotic test-
ed that appeared to be useful was Erythromycin. When used at a concentration
of 1 ppm, it resulted in increased numbers of colonies of a blue actinomy-
cete, which has not been identified, but is readily differentiated from all
other actinomycetes seen due to the production of blue spores and a blue pig-
ment which diffuses into the agar. However, this actinomycete appears to be
of minor importance as compared to a much more numerous white actinomycete
and the bacteria.
TABLE 7
ANTIBIOTICS TESTED FOR USE IN ISOLATION MEDIA
Antibiotic
Concentrations Used
(ppm)
Streptomycin
50, 100
Aureomycin
50
Neomyci n
10, 100
Chloramphenical
10
Polymyxin B
10
Erythromycin
1, 10
Novobiocin
10, 100
Penicillin
2, 50, 100
Since motile bacteria prevented counting on agar plates, the dilution
tube technique was tried (Alexander, 1964). Population estimates were made
during several stages of the composting process, using dilution tubes, but
two methodological problems prevented clear interpretation of the data.
First, nutrient broth (pH 8) was used as the detection medium and both bac-
teria and actinomycetes grow in it. While total numbers could be estimated,
the simultaneous development of bacteria and actinomycetes precluded accurate
estimates of either group. Second, the bacterium active during the thermo-
philic phase of composting is a Bacillus species which forms resting spores.
Thus, total counts of Baci11 us sp. represent both inactive propagules
(spores) and vegetative cells. However, if this technique is coupled with a
treatment that eliminates vegetative cells (e.g., heating compost suspensions
to 80°C), it may be possible to determine the principal organisms active as
composting progresses. Preliminary tests on estimating spore populations in-
dicated further problems.
49
-------
Two methods were used to eliminate vegetative cells; heating a compost
suspension to 80°C for 10 min (Clark, 1964) and exposing a suspension to 70
percent ethanol for 30 min as recommended by Jurgensen (1967). When assayed
by the dilution tube method, heating gave a spore population about three
times larger than the ethanol treatment. Further, the spore density indi-
cated by dilution tubes was only about 1/20 that indicated by dilution plates.
Clearly, more critical evaluation of these techniques needs to be done if
quantitative estimates of active bacteria and actinomycetes are to be obtain-
ed.
Fungi--
Fungi are much more readily detected and isolated than the bacteria or
actinomycetes. The isolation media used include yeast-glucose agar and
yeast-starch agar (Cooney and Emerson, 1964). Contrary to the opinion of
some earlier investigators (Apinis, 1963; Cooney and Emerson, 1964; Fergus,
1964), the inclusion of several antibiotics in the isolation media was found
to be necessary. The combinations of antibiotics used included 1) Strepto-
mycin (50 ppm)-Penicil1 in (40 ppm), 2) Streptomycin (100 ppm)-Neomycin (100
ppm)-Penici11 in (100 ppm), 3) Streptomycin (50 ppm)-Chloramphenicol (40 ppm),
and 4) Streptomycin (50 ppm). Although the effectiveness of the antibiotic
combinations change as the compost matures, the best combination during the
thermophilic stage was found to be Streptomycin-Penicillin-Neomycin. As the
compost matures and bacteria and actinomycetes become less dominant, the
Streptomycin-Chloramphenicol mixture yields plates completely free of bac-
teria and actinomycetes.
The plates were inoculated by either sprinkling small pieces of compost
directly on the surface of the agar or utilizing a multipoint replicator
(Stotzky, 1965). The plates then were incubated at 25, 39, and 47°C.
Organisms Prevalent during Composting--
During the thermophilic phase of composting, a Bacillus sp. was consis-
tently observed to be virtually the only organism present in large numbers.
However, due to the variety of conditions imposed on the various batches of
compost, it is difficult to generalize further on the organisms that predom-
inate during the different stages of the composting process. For example,
when a batch process was used with chicken manure, actinomycetes colonized
the material following removal from the composter to the extent that the com-
post acquired a whitish cast. Also, the fungus Coprinus frequently was ob-
served fruiting on the piles. However, when a continuous process with hog
manure was used, the material was heavily colonized by a species of Paecilo-
m.yces and no Coprinus mushrooms were observed. Also, in the latter material,
huge populations of nematodes and mites developed which were not observed in
the batch-processed material. The nematodes and mites were determined to
have been contaminants brought in after the compost was removed from the com-
poster.
The lack of Coprinus in the continuous-process material may be an indi-
cation of an incomplete initial fermentation that left some readily available
carbohydrates in the material removed from the composter. In pure culture on
autoclaved compost, high levels of dextrose slowed both vegetative growth and
50
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basidiocarp formation of Coprinus. When 10 g of dextrose were added to 150 g
of compost, fruiting occured extensively in several flushes in from 11-43
days of incubation. However, when 30 g of dextrose were added, no mushrooms
were formed until 53 days of incubation. Similarly, Coprinus readily fruits
on yeast-gluclose agar but not on potato-dextrose agar which contains much
higher levels of carbohydrates.
Only one true thermophilic fungus, Thermoascus aurantiacus Miehe, was
isolated from the compost. This fungus was isolated only sporadically and
is thus thought to be of minor importance in the composting process. The re-
sults of temperature studies of this and other organisms isolated from the
compost are given in Table 8.
In contrast to Thermoascus, the thermotolerant basidiomycete Coprinus
frequently was observed fruiting and appears to be one of the major organisms
active in the compost as it matures. Coprinus usually became abundant early
in the mesophilic phase and could be isolated from virtually every particle
of material that has been composted for six months.
As mentioned earlier, Paecilomyces sp. is also a very important second-
ary colonizer of the compost. Although this fungus grows very slowly in cul-
ture, it seems well adapted to growing on the natural compost in that it can
be observed fruiting on much of the older compost. Part of this success may
be due to the fact that Paecilomyces apparently is well adapted to alkaline
conditions, growing best on media of about pH 8. The response of Coprinus
sp. to acidity (pH) is quite similar. Thus, secondary colonization of the
compost may be determined by tolerance to alkaline conditions much as primary
colonization is determined largely by temperature.
TABLE 8
CARDINAL TEMPERATURES OF ORGANISMS ISOLATED FROM POULTRY
MANURE-SAWDUST COMPOST
Vegetative growth Sporocarp formation
Organisms TemperatureuC TemperatureuC
Min. Opt. Max. Min. Opt. Max.
Coprinus sp. *
20
38
46.5
20
32
32
Thermoascus aurantiacus *
29
47
58
29
36-42
47
Blue actinomycete +
29
44-
-51
57
White actinomycete +
27
42-
-49
55
Bacillus sp. +
66
* Linear growth on yeast-glucose agar.
t 32°C maximum for full development; abortive basidiocarps formed between 33
and 38°C (i.e. stipe and cap partly developed but no basidiospores formed).
+ Growth estimated on nutrient agar.
51
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SECTION 4
ECONOMIC FEASIBILITY
High rate thermophilic composting of animal wastes with other carbona-
ceous materials can be accomplished either in batch processing or by using a
continuous system. However, in order for the process to be commerically at-
tractive, it must be economically feasible. Thus, this section of the report
deals with cost estimates based on a poultry production unit of 100,000 birds.
The costs reported in this section reflect the economic situation at the
time this part of the study was conducted (1971). It preceded the several
years of field evaluation of the end products. Most figures remain in rela-
tive proportion to one another and thus a similar survey would be revealing
at any point in time. It is interesting to note that this survey resulted in
an estimated cost of finished compost of $18 per tonne. In September, 1976,
we were informed that essentially this same process was being used in a com-
mercial operation in the U.S. and that the actual present cost was $17 per
tonne (personnel communication, Harold E. Schlichting, Jr., BioControl Com-
pany, Port Sanilac, Michigan).
LEVEL OF PRODUCTION
The initial size of the composting plant is determined by the needs of
waste-disposal for a poultry ranch having 100,000 birds. The average manure
production for poultry is assumed to be 0.19 1/bird/day, including both solid
and liquid wastes. Weight of manure to be disposed daily = (100,000 birds) x
(0.19 1) x (1 kg/1) = 19,000 kg = 19 tonnes.
A sawdust-to-manure ratio of about 3:1 is used. Therefore, weight of
sawdust needed daily = 19 x 3 = 57 tonnes. The sawdust may have to be partly
dried so that the mix-moisture remains in the optimum range. Sometimes, the
manure may also have to be dried. Weight of the mix = 19+ 57 = 76 tonnes/
day.
Assuming that only 80 percent of the mass is left after the thermophilic
reaction and 60 percent of the original mass is left after 4 weeks of curing,
the ultimate weight of the product due to one day's operation would be 45.6
tonnes.
52
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COSTS OF PRODUCTION
Raw Materials per Tonne of Compost
One tonne of finished compost requires:
1.4 tonnes of raw mix
weight of sawdust = 1.4 x 3/4 = 1.05 tonnes
weight of poultry manure = 0.35 tonnes
Green sawdust can be available for about $2.20/tonne^
The poultry waste needs to be disposed of. Thus, there is little or no cost
attached to it. Instead, there will be potential savings of the expenses in-
curred for safe disposal of poultry manure by any other methods. These sav-
ings depend upon the alternative method of disposal and are not included in
this study.
Phosphoric acid will be used to trap any escaping ammonia from the re-
actor. The neutralized acid will be sprinkled on the compost piles in the
curing stage to retain the nitrogen and supplement the phosphorus content of
the compost. The amount of phosphoric acid needed is a function of nitrogen
loss, which should be kept to its minimum. From the experience gained during
the continuous composting, it was found that 10 liters of solution containing
1 liter of commercial grade (85 percent pure) H~P0, was neutralized by about
450 kg of raw-mix while under thermophilic decomposition. Therefore, the
amount of commercial grade H3PO4 for a mix of 1.4 tonnes is 1.4 i 0.45 = 3.1
1. The specific gravity of H3PO4 is 1.884. The weight of H3PO4 needed for 1
tonne of finished compost = 3.1 1 x 1.884 kg/1 = 5.84 kg. Commercial grade
(85 percent pure) H0PO4 costs about $196/tonne2. Therefore, cost of 5.84 kg
of H3PO4 = 196/1000 x 5.84 = $1.14. Total cost of raw materials per ton of
finished compost is:
sawdust $2.31
Poultry manure $0.00
H3PO4 $1.14
Total cost per tonne of compost = $3.45
^Personal contact with Mr. R. H. Hogan, Evans Products Corporation, Moncure,
N. C. June, 1971.
2
Personal contact with Mr. J. H. Collie, Southchem Inc. Durham, N. C. June,
1971.
53
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Real Estate Requirements
A sizeable area of land will be required for the curing Of the thermo-
philically reacted compost for 4 weeks. About 76 x 0.80 = 60.8 tonnes of such
compost will be produced per day. Assuming that it takes one more week for
the cured compost to be packed and hauled for sale, the amount of compost con-
tinuously on hand = 60.8 x 7 x 5 = 2128 tonnes.
The bulk weight of the compost is about 480 kg/m^. Thus a rectangular-
shaped pile 1 m deep and 2 m wide at the base will contain about 2 nr per
running meter, or 960 kg per running meter. Therefore, one tonne of compost
would need 1000/960 = 1 running meter. There are 10,000 square meters per
hectare (ha), 10,000/2 = 5,000 running meters (2 m wide) to a hectare.
5000/1 = 5000 tonnes per hectare.
Thus, approximately one half hectare will be enough for the compost curing.
Sawdust will be stored in piles on the ground, maintaining a seven day stock
pile. Poultry waste will be obtained from the ranch daily. Land will be re-
quired for the construction of a composting plant, packaging plant, offices,
parking of heavy and light machinery, storage ground, etc. Approximately 4
hectares should be sufficient for the entire operation. Cost of industrial
land around Raleigh, N. C. is about $740 - $1250 per hectare.3
cost of land = 4 x 1250 = $5000
The land should be fairly level, clean, with an ample water supply and on or
near a railroad siding.
The estimated construction cost (1972) of plant buildings, offices, etc.
is about $30,000 and of the railroad spur is about $10,000.
Total real estate cost = $45,000. Let the life of the plant be 30 years
after which the land could be sold at least at par. Then at an interest rate
of 10 percent, the annual cost of capital recovery is given by:
CR = (45,000 - 5000) x
0.10 (1 + 0.10)
30
30
- 1
+ (5000) x (0.10)
(l + n.io)
= (40,000) x (0.10608) + 500
= 4243 + 500 = $4743
Let the annual maintenance expenses for the real estate items be 1 percent of
the total cost = (45,000 x 1)/100 = $450.
3
Personal contact with Mr. C. F. Gaddy, Gaddy Real Estate Company, Raleigh,
N. C. June, 1971.
54
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The property tax will be charged on half the actual value of total property,
i.e., $22,500. The rate of tax, including a reasonable fire charge, is about
$1.98 per $100.4
yearly tax expense = 1.98 x 22,500/100 = $456
total annual expense due to real estate property = $5649.
Annual production of compost = 45.4 x 365 = 16,556 tonnes
annual cost of real estate/ton = $5,649/16,556
= $0.34/tonne
Heavy Machinery^
Bulk Feed Body Trucks--
These will be used to bring sawdust and to transport final compost.
Three trucks will be needed.
Initial investment per truck = $25,000
Total investment = $75,000
Truck-Mounted Rotary Plows--
These will be used as spreader, loader and unloader for sawdust as well
as compost.
One double rotary snow-go plow equipped with drive unit
= $5,000
One six-wheel drive truck
- 15,000
One single rotary snow-flye plow with power unit
= 2,500
Loading chute and mechanical cab controlled chute rotation
500
Tractor with power loader attachment
= 8,000
Railroad Car Loaders--
These will be used to load the railroad cars with the finished compost.
Two units needed. Two forge blower drive units @ $1500 = $3000.
The total value of the heavy machinery as outlined above is $109,000. Con-
sidering an average life period of ten years with a salvage value of 10 per-
cent of the initial investment and an interest rate of 10 percent we have the
4
Personal contact with Wake County Tax Department, Raleigh, N. C., 1971.
5
All cost figures for heavy machinery were obtained by personal contact with
Mr. George Jones, General Machinery Company, Raleigh, N. C., June 1971.
55
-------
annual capital recovery as:
CR = (109,000 - 10,900) x (0.16275) + (10,900) x (0.10)
= (98,100) x (0.16275) + (10,900) x (0.10)
= 15,980 + 1,090
= $17,070
If the yearly operation and maintenance costs are assumed to be 1 percent of
the initial cost, then total yearly expense = 17,070 + 1,090 = $18,160.
Cost per tonne of compost = $18,160/16,556 = $1.10/tonne
Other Equipment
Compost Drums--
Three 4.6 m diameter by 9.2 m long drums with about 150 nr capacity will
be fed with raw mix at one end and with processed compost coming out the
other end. The drums will be rotated at 1 RPM by an electric motor and gear
system. The cost per drum is $70,000. Cost of fabricating three drums" =
$210,000.
Electric Motor-
Three 40 hp electric motors @ $3000 = $9000'
Air Compressor and Flow Rater--
These should be capable of supplying as much as 470 1/s of air at atmos-
pheric pressure to the three drums. The cost is estimated to be $10,000.8
Mixing Mechanism--
A blending mill to mix the sawdust and poultry manure homogeneously be-
fore it is fed into the drum is estimated to cost $5,000.°
Packaging Plant--
Packaging plant is to make 25 kg, 50 kg, and 250 kg packets of finished
compost. The cost is estimated to be $10,000.8
^Personal contact with Mr. Edward Wood and Mr. Charles Stanley, Aeroglide
Corporation, Raleigh, N. C., June 1971.
^Personal contact with Mr. E. D. Reams, Electrical Equipment Company,
Raleigh, N. C., June 1971.
O
Personal estimate, D. S. Airan, 1971.
56
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Phosphoric Acid Tank—
The tank should be stainless steel, on piers, and have a capacity of
29 The cost of the tank and installation as given by Schmaedick (1958)
is assumed to hold good as: Total cost = $20,000.
Water Tank—
A lined steel tank of 436 m^ capacity equipped with centrifugal pumps
to deliver 19 1/s is required. Cost of tank, pump and installation as given
by Schmaedick (1958) is assumed = $30,000. Total cost of above equipment =
$294,000.
Considering this equipment for 30 years (the life of the plant) with a
salvage value of 5 percent of initial investment and an interest rate of 10
percent, we have the annual capital recovery as:
CR = (294,000 - 14,700) x (0.10608) + (14,700) x (0.10)
= (279,300) x (0.10608) + 1470
= 29,625 + 1470
= $31,095
Assuming that yearly operation and maintenance costs are 1 percent of the
initial cost, total yearly expenses are 31, 095 + 2940 = $34,035.
Cost per tonne of compost = $34,035/16,556
= $2.06/tonne
Miscellaneous Yearly Expenses
Miscellaneous Equipment--
This equipment consists of shovels, moisture testing equipment, pH
meter, chemical analysis apparatus, tools for general maintenance, office
furnishings, locker room furnishings, first aid kits, conveyor belts, etc.
for raw materials or finished compost. Overall expenses estimated to be =
$5000.8
Electric Power Requirements-
Yearly consumption of electric power is estimated to cost $2000.°
Water Requirements-
Yearly consumption of water is estimated to cost $1000.8
Communications--
Telephone, stationary, and postage - $2500.°
57
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Bags for Packaging Finished Compost--
$15008 (including printing of brand name on the bags).
Advertising and Publicity--
Initial investment is expected to be higher than later routine expenses.
The product can be put on trial basis first in local area, then statewide,
and finally slowly expanding its scope in other states. A figure of $25,000
is estimated.9 Total miscellaneous expenses = $37,000 per year.
cost/tonne of compost = $37,000/16,556 = $2.23/tonne
Labor Requirements
The yearly expenses for
labor
will be roughly as
follows:
Persons
No.
Yearly Rate^
Annual Cost
Plant Superintendent
1
$20,000
$20,000
Truck Drivers
3
8,000
24,000
Rotary Plow Drivers
2
8,000
16,000
Railroad Car Loader
1
8,000
8,000
Composter Drums Operators
2
7,000
14,000
Mixing Plant Operator
1
7,000
7,000
Packaging Plant Operator
1
7,000
7,000
Laboratory Supervisor
1
10,000
10,000
General Laborers
2
6,000
12,000
Secretaries for Office
2
8,000
16,000
Bookkeeper
1
8,000
8,000
Mechanic
1
8,000
8,000
Total cost of labor/yr.
=
$150,000
Yearly expense per tonne of compost = $150,000/16,556
= $9.06/tonne
g
Personal contact with Mr. W. M. Merrel1, J. T. Howard Advertising Agency,
Raleigh, N. C., June 1971.
58
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Total Cost per Tonne
The following is a summation of the total production cost.
Raw materials
Real estate
Heavy machinery
Other Equipment
Miscellaneous expenses
Labor expenses
$3.45
0.34
1.10
2.06
2.23
9.06
Total cost/tonne
$18.24
Thus, at a production level of 45.4 tonnes/day, the unit cost of production
for the finished compost will be $18.24 or approxiamtely $18/tonne.
SALE OF COMPOST
The finished compost is a sanitary, non-offensive material which smells
like forest humus when wetted. It can be used in greenhouses, nurseries,
home gardens, farms, cemeteries, golf courses, athletic fields, and city
parks. The product can also be used on heavily worked soils as a soil con-
ditioner to help retain moisture.
The possible competitors to this product in the market are peat moss,
old sawdust, dehydrated cow manure and other such organic materials. Dehy-
drated cow manure retails for $11/100 kg and produces offensive odor when
wetted. The compost produced will definitely be competitive in terms of
quality and in order to introduce it in the market, a wholesale price of
$2.20/100 kg FOB plant will be established. Thus the retail price should not
need to exceed $4-6/100 kg which should be very attractive to the custom-
ers.^ Thus the compost can wholesale for $22/tonne which will give an an-
nual profit, P, of:
MINIMUM PRODUCTION LEVEL
The enterprise can sustain at a minimum production level where the con-
dition of TOTAL INCOME = TOTAL COST is satisfied. It can be seen from Table
9 and Figure 23 that as the level of production is raised, the unit cost of
production falls. If the sale price of compost is fixed at $22/tonne, then
the break-even level of production will be about 36 tonnes/day. This means
^Personal contact with Mrs. R. A. Fowler, Fowler's Nurseries, Raleigh, N. C.,
June, 1971.
P = ($22.00 - $18.24) x (16,556) = $3.76 x 16,556
= $62,251
59
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TABLE 9
UNIT PRODUCTION COST AT DIFFERENT LEVELS OF PRODUCTION*
Level of
Production
Cost per
Tonne
Per Day,
Tonnes
Per Year,
Tonnes
Raw
Materials
$
Real
Estate
$
Heavy
Machinery
$
Other
Equipment
$
Mi scellaneous
Expenses
$
Labor
Expenses
$
Total
Cost/Tonne
$
18
6,623
3.45
0.97
2.75
5.16
5.60
22.65
40.58
27
9,934
3.45
0.65
1 .84
3.44
3.74
15.10
28.22
36
13,245
3.45
0.49
1 .38
2.58
2.80
11.33
22.03
45.4
16,556
3.45
0.34
1.10
2.06
2.23
9.06
18.24
54
19,867
3.45
0.33
0.93
1.72
1.87
7.55
15.85
*The calculations are based upon the assumption that the real estate property, machinery and equipment,
and labor remain at the same level at various production levels. In practice, it will not actually
hold. However, for the purposes of illustration here, it was assumed to be satisfactory.
-------
40
a
c
c
o
30
Z
o
u
o
o
ae
a.
10
O
u
10
z
p
J 1 1 I
0 10 20 30 40 50 60 70
PRODUCTION PER DAY (tonnes)
Figure 23. Compost cost-return curve
61
-------
a yearly production of 13,140 tonnes of finished compost.
This process might be attractive to some poultrymen even at a loss if
the loss were less than their current cost of waste disposal. Also the
amount of land required is much less than would be needed for waste disposal
via land spreading and the process is less offensive than lagooning of
wastes.
62
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SECTION 5
PRODUCT EVALUATION
As indicated in the Introduction section of this report, the efficient
method of preparation of compost from animal waste and carbonaceous material
would be mostly of academic interest unless there were a beneficial use for
the end-products. This section includes the results of both greenhouse and
field evaluations of different end-product and presents solid data indicating
that the material does have beneficial properties from the standpoint of both
soil improvement and increased food production. A very wide range of rates
of application were tested since it was of interest to determine both the
minimum amount capable of producing a significant yield increase and the max-
imum amount usable without causing either crop or environmental damage. In
the former case the compost is serving as a fertilizer substitute while in
the latter case the soil is serving as a sink in a waste disposal and nutri-
ent recycling system.
MATERIALS AND METHODS
Sawdust-Poultry Manure Compost Mulching Experiment on an Established Lawn
Sawdust-poultry waste compost was applied as a surface mulch to an es-
tablished lawn. Grasses in the lawn were largely coastal bermudagrass with
small amounts of fescue. A 15 m x 2.5 m plot was separated into twenty-three
plots of 16.3 m2 each. Compost was applied as a mulch on top of the grasses
at three levels; 1.1 tonnes/ha, 2.3 tonnes/ha, and 4.5 tonnes/ha. These were
completely randomized by treatment and replication. Each treated plot was
separated from other treated plots by a control plot. There were three re-
plications each of the 1.1 tonnes/ha and the 4.5 tonnes/ha treatments, six
replications of the 2.3 tonnes/ha treatment, and eleven replications of the
control treatment. The plots were established in May, and harvested with a
lawn mower and grass catcher device approximately every thirty days for three
harvests. Each plot was clipped to a 1.3 cm level at each harvest. Dry
weight was determined after drying in a forced-air oven at 70°C for 48 hrs.
A subsample was obtained, dried, ground in a Wiley mill to pass a 20 mesh
sieve, and analyzed for total nitrogen content in a nitrogen analyzer.
Sawdust-Poultry Manure Compost Applications to Wheat, Millet, and Tomatoes
in the Greenhouse
Cultivar GAHI-1 Pearl Millet, a summer cereal grain, and Knox winter
wheat were the field crops employed. Compost was applied at nine rates to a
sandy soil from the Norfolk soil series in 4.5 1 plastic containers. The
compost was thoroughly mixed with the soil and the pots were filled to
63
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capacity. Treatments were a control, consisting of soil only, 100 percent
compost, and the following rates of compost application to the soil (tonnes/
ha equivalent): 1.12, 2.24, 5.6, 11.2, 22.4, 112, 224, and 448. Each treat-
ment was replicated three times. A completely randomized design was used.
Randomization was by treatment and replication with each crop. The grain
seeds were germinated prior to planting to insure viability and equal plant
population per pot. The pots were watered to maintain approximate field
capacity. Initial plant population was fifty plants per pot. The plants
were harvested after ninety days of growth. A 25 percent sub-sample was
dried at 70°C,ground in a Wiley mill to pass a 20 mesh sieve, and analyzed
for N, P, K, Ca, and Mg. Methods of nutrient analysis were Kjeldahl for N;
vanadate-molybdate for P on a spectrophotomer; flame photometry for K; and
atomic absorption spectrophotometry for Ca and Mg. The experiment was es-
tablished in August and terminated in November.
The same experimental design and procedures were used for the tomato
greenhouse experiment as were used for the grains with t'ne exception of plant
population per pot. There was one Marion tomato plant per pot. Tomato seeds
were planted in a sterilized coarse sand seed bed, and the resulting seed-
lings were transplanted to the pots at a uniform height of ten centimeters.
Soil samples were obtained with a core sampler. Five cores per pot were
composited and analyzed by the Agronomic Division of the North Carolina De-
partment of Agriculture.
Sawdust-Poultry Manure Compost Applied to Tomatoes in the Field
Sawdust-poultry manure compost was applied at six rates to a Chester-
field sandy loam soil located on the North Carolina State University Central
Crops Research Station at Clayton, North Carolina. The compost was thorough-
ly incorporated in the surface fifteen centimeters of the soil by spading and
disc harrowing. Treatments consisted of a control treatment (no compost) and
5.6, 11.2, 22.4, 44.6, 336, and 448 tonnes/ha of compost. There were three
replications of each treatment, and a completely randomized design was used.
Twenty-one plots, measuring 1.8 x 1.8 m, were arranged in a 15.2 x 15.2 m
block. Each plot was isolated by a 60 cm border area.
Marion tomato plants, 20 cm in height, were transplanted to the plots
in April. Each plot had a plant density of nine plants in three rows. The
spacing was 60 cm between rows and between plants in the rows. The border
areas were planted with the same plant density as the plots. Three border
rows were planted around the exterior of the entire block. Fresh fruit
weight and number of friut were determined from each plant in all treatments.
Mature fruit was harvested 12 times. The initial harvest was June 29, and
terminal harvest was August 18. A random sample of fruits from all treatment
replications from each harvest was dried at 70°C, ground, and analyzed for
N, P, K, Ca, Mg, and Mn.
Six plant tops were randomly selected from each plot, dried at 70°C,
ground, and analyzed for the same nutrients. The plants were harvested on
August 18. Methods of analysis were the same as those reported for the
64
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greenhouse study. In addition, Mn was determined by atomic absorption spec-
trophotometry. Soil samples for chemical analysis were obtained with a
bucket auger in the immediate root zone of each plant to a depth of 15 cm.
Soil chemical analyses were conducted by the Agronomic Division of the North
Carolina Department of Agriculture, undisturbed soil samples for physical
analysis were obtained with a Lutz soil sampler. A tension table and pres-
sure membrane apparatus were utilized to determine soil moisture characteris-
tics.
Two irrigations each of 55 mm of water, were applied to the tomatoes
during the growth period. Weed control was by hand-hoe cultivation. No pes-
ticides were used nor were any needed during this study.
Paper-Poultry Manure Compost Applied to Tomatoes in the Field
Paper-poultry waste compost was applied at four rates to Marion tomatoes
on a Chesterfield sandy loam soil. Treatments consisted of a control treat-
ment (no compost), 2.2, 11.2, 22.4, and 112 tonnes/ha of compost. There were
three replications of each treatment. A completely randomized design (ran-
domization by treatment and replication) was employed.
Row width was 1.5 m and spacing between plants was 45 cm. The plots
consisted of fifteen-2.3 m rows. Border plants were planted on the ends of
each row, and one row of border plants surrounded the entire plot area.
Compost was applied in a one meter wide band in the center of each row
and incorporated into the soil with a rotary tiller to a depth of 15 cm. The
compost was applied May 26, and 20-cm-tall Marion tomato seedlings were
transplanted to the plots on May 27.
Tomato fruit was harvested eight times, and fruits from each plant were
weighed and counted. A random sample of fruit from each plant was oven-dried
at 70°C for nutrient analysis. Final fruit harvest and plant tissue harvest
was September 9. Plant tops were dried at 70°C for tissue analysis. Tissue
was analyzed for N, P, K, Ca, Mg, and Mn. Soil samples were also taken
September 9, and analyzed by the Agronomic Division of the North Carolina
Department of Agriculture.
Both the sawdust-poultry waste and paper-poultry waste composts were
analyzed for nutrient content and other characteristics (Table 10).
RESULTS AND DISCUSSION
Sawdust-Poultry Manure Compost Mulching Experiment on an Established Lawn
Surface mulches of properly composted materials may have value as an
amendment for home lawns, gardens, golf courses, cemetaries, nurseries, and
commercial crops requiring infrequent or no cultivation. Sawdust, leaves,
straw, and other litter have been effectively used as mulches to reduce soil
loss and weed growth and to conserve moisture. Composts provide these bene-
fits and supply nutrients for plant growth. Home owners, a potential market
for compost used as surface mulch, could utilize composts in the maintenance
65
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TABLE 10
PHYSICAL AND CHEMICAL CHARACTERISTICS
OF COMPOSTS UTILIZED IN THIS STUDY
Type of
Physical and Chemical Properties
Compost
Nutrient Content
fPprrpnt drv wpiaht.}
(ppm)
Mn
N
P
K
Ca Mq
Sawdust Poultry
Manure Compost
0.86
0.
65 0.61
1.42 0.16
159
Paper-Poultry
Manure Compost
1.46
1 .
35 1.32
2.20 0.16
153
Particle
>10 mm 10-2.0
Size Distribution (Percent)
mm 2.0-1.0 mm 1.0-.25 mm <0.
.25 mm
Sawdust-Poultry
Manure Compost
7.0
52
18
18
5
Paper-Poultry
Manure Compost
1.0
38
39
20
27
Other Characteristics
Bulk
Acidity Density
(pH) (q/cc)
CEC
(meq/lOOq )
Water Holding
Capacity
(ml/q)
C: N
ratio
Sawdust-Poultry
Manure Compost
8-9
0.280
67
3.71
18-40:1
Paper-Poultry
Manure Compost
8-9
0.310
52
3.32
ND*
*Not determined
66
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of established lawns and flower beds. Compost could be used to increase
grass growth on lawns, and, at high applications around ornamental shrubs and
in flower beds could reduce weed growth. Sawdust-poultry manure compost was
applied to established lawn grasses to determine its effect as a surface
mulch with respect to dry weight production, N uptake, and regrowth of the
grass after clipping. All compost treatments increased total dry weight pro-
duction (Table 11), N concentration, and total N yield (Table 12) when com-
pared to the control plots. The 1.1, 2.3, and 4.5 tonnes/ha treatments in-
creased total dry weight production 45, 57, and 25 percent respectively and
total N accumulation by 81, 103, and 68 percent respectively. Dry matter
yield of the 2.3 tonnes/ ha compost treatment was 9.1 percent greater than
the 1.1 tonnes/ha treatment and 26 percent greater than the 4.5 tonnes/ha
treatment. The total N yield of the 2.3 tonnes/ha treatment was also 12 and
21 percent greater than the total N yield from the 1.1 and the 4.5 tonnes/ha
treatments, respectively. Recovery and regrowth after harvest were also in-
creased by compost treatments.
Although all compost treatments increased grass yields, there were only
small differences among yields of the treated plots at the first harvest.
Subsequent harvests indicated that regrowth patterns differed with compost
treatment. The highest compost level demonstrated the poorest regrowth of
the treated plots and was only 16 percent greater than the control plots at
the final harvest. The second harvest indicated that the 2.3 tonnes/ha
treatment promoted more rapid growth than the 1.1 tonnes/ha treatment. The
2.3 tonnes/ha treatment sustained a high rate of growth until the third har-
vest while the 1.1 tonnes/ha required thirty days longer to promote the same
yield. The final harvest for the two lower compost treatments were essen-
tial ly equal (Table 11).
The N concentration in the 4.5 tonnes/ha treatment indicated that some
factor other than nutrient supply and uptake may have been reducing yields.
The low bulk density (0.28 g/cm^) of sawdust-poultry manure compost requires
thick layers of compost at high application rates. Short bladed grasses,
growing close to the surface of the soil, such as burmudagrass, would have to
grow through the compost layer for optimum photosynthesis to occur. Compost
depth and frequent close clipping appear to reduce burmudagrass growth. The
effect of sawdust-poultry manure compost surface application on established
burmudagrass lawns is a function of the rate of application. A maximum
threshold of application exists for promoting growth (2.3 tonnes/ha), and a
minimum threshold exists for reducing growth (4.5 tonnes/ha) under the con-
ditions of this experiment (Table 12). These thresholds should vary with the
variety of grass, type of compost, and frequency of harvest.
Sawdust-Pountry Manure Compost Applications to Wheat, Millet, and Tomatoes in
the Greenhouse
An ideal solution to animal waste disposal is one which utilizes the
wastes generated as a nutrient source to grow the feed necessary for a sub-
sequent animal production operation. A continuous re-cycling of nutrients
may be established with a minimum potential for adverse environmental effects.
Wheat and millet, two grasses employed in the greenhouse study, can be uti-
lised as forage or feed in an integrated animal production-land-waste
67
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TABLE 11
DRY WEIGHT PRODUCTION OF THREE HARVESTS
OF
LAWN GRASSES AT VARIOUS RATES
OF
SAWDUST
-POULTRY MANURE COMPOST APPLIED AS A
SURFACE MULCH
Compost
Harvest
Total Dry Wt.
Treatment
1 2 3
(Tonnes/ha)
(Mean Dry Wt. Grams/Plot)
(Grams/Plot)
0
97 137 165
399
1.1
152 188 239
579
2.3
144 236 246
626
4.5
141 166 191
498
TABLE 12
NITROGEN UPTAKE
BY LAWN GRASSES
AT VARIOUS RATES
OF SAWDUST-POULTRY
MANURE COMPOST
APPLIED AS A SURFACE
MULCH
Compost
Mean Nitrogen
Total Nitrogen
Treatment
Concentration
Uptake
(Tonnes/ha)
(% Dry Wt.)
(mq N/plot)
0
2.0
8.0
1.1
2.5
14.5
2.3
2.6
16.3
4.5
2.7
13.4
68
-------
disposal system.
Tomatoes were selected as an alternative to this integrated system. The
waste generated could be used to grow a crop which will not be recycled
through the animal but will effectively remove nutrients from the waste and
produce a crop of high market value. The returns from the sale of the crop
could be used to support an animal production operation or the returns could
cover the cost of waste disposal by composting.
All three crops employed in the greenhouse study are grown in the South-
east and are intended as model crops for demonstrating the feasibility of
land disposal of animal waste. The greenhouse phase was initiated to indi-
cate suitable rates of compost application to soil and crops to be utilized
for field evaluation of the compost. Decisions such as the amounts of com-
post needed for field experiments and field plot designs were determined from
the greenhouse study.
Certain conditions existing in the greenhouse limited the degree of ap-
plicability of the greenhouse study to field conditions. They included: (1)
pot size (4.5 1) limited the amount of total nutrients for a given treatment
and also limited the soil volume for root exploitation; (2) the experiment
was conducted from mid-August to mid-November, a time of reduced radiant
energy, hence reduced photosynthesis; and (3) a short term experiment (90
days) decreased the potential for maximum growth. All of these restrictions
tend to reduce the potential for maximum plant growth.
Dry weight response patterns were similar for the three crops (Figure
24). The general pattern consists of increasing dry weight production with
increasing compost levels up to 112 or 224 tonnes of compost per hectare with
a decrease beyond these levels. The magnitude of the dry weight response is
related to differences in plant population per pot and individual growth
characteristics of the crop plants. Millet and wheat plant populations were
50 plants per pot while the tomato population was one plant per pot.
Both grasses exhibited greater response at lower compost levels when
compared to the tomatoes (the slope of the curve is greater for these two
crops at the lower levels). This indicates that the grasses may be more ef-
ficient at lower compost or lower nutrient levels than are the tomatoes. The
wheat and millet had equal plant populations per pot yet the millet produced
a much greater dry weight. The growth characteristics of these two grasses
were different. During the 90 day growth period, the millet proceeded
through sequential stages of growth from germination to grain initiation.
The wheat did not follow this sequence but rather produced only vegetative
growth. This growth consisted of large numbers of branches and massive
tillering and appeared very succulent and had a low degree of turgidity. The
wheat growth response may have resulted from the fact that it was a winter
wheat but was planted similar to a spring wheat. Without the cold treatment
to which it would normally be subjected, the wheat exhibited this forage-
type growth pattern.
69
-------
o
p-
70
a>
Q.
iA
E
a
6 0
o>
Tomato
Wheat
<
LlJ
2 0
I 0 0 %
COMPOST
448
22, 4
COMPOST TREATMENTS (Tonnes/ha)
Figure 24.
Dry weight yields of millet, tomato, and wheat tops in response to
sawdust-poultry manure compost and soil mixtures
-------
Although 112 to 224 tonnes/ha of compost produced maximum dry weight
production, there was a decrease beyond these levels. Both the 448 tonnes/ha
and the 100 percent compost treatments exhibited a significant decrease in
dry weight production; at the 5 percent level of significance for all crops.
The following measurements were taken from the tomato crop to determine the
causes for the reduction in dry weight yield at compost levels beyond 112 and
224 tonnes/ha: (1) concentration of nutrients in plant tissue; (2) total
nutrient uptake (Table 13); and soil chemical test levels (Tables 14 and 15).
At the higher compost levels the K uptake increased and Ca uptake
leveled (Table 13). This is probably due to complementary ion effect and is
well documented in the literature. However, this factor is not limiting
since the Ca content is within the range for adequate growth (Friis-Nielsen,
1969; Ward, 1964). The Ca content increased with increasing compost and was
equal in the 224 and 448 tonnes/ha treatment and the 100 percent compost
treatments. None of the cations were deficient or toxic to tomato growth.
Total uptake of N and P exhibited no significant differences among the three
highest compost levels (Table 13). Therefore, it can be concluded that nu-
trients were not limiting nor present in toxic amounts within the plants.
The residual soil test levels (soil test levels at the end of the growth
period) were examined for possible limiting factors in the tomato dry weight
production. There was no significant difference in soil acidity (pH) among
the three highest compost treatments. However, the pH value of these treat-
ments was significantly higher than the 112 tonnes/ha treatment. This would
indicate that nutrient availability was higher in the highest treatments.
This should cause an increase rather than a decrease in dry weight produc-
tion of tomatoes. It can be concluded that the pH effect did not cause a
decrease in dry weight production.
There was no significant difference in the residual soil test levels
for NOo, NH^, P, or Mn between the two highest compost treatments and the 112
tonnes/ha treatment. Most of these nutrients increased with increasing com-
post level and would tend to increase rather than decrease dry weight pro-
duction of the tomatoes. Both the Ca and Mg soil tests for the two highest
treatments were significantly greater than the 112 tonnes/ha compost treat-
ment. All of the soil nutrient test levels indicate that increasing compost
treatments increase the total amount of nutrients available for growth and
are not present in toxic quantities.
The cation exchange capacity was high in both the highest levels of com-
post. This factor also suggests that greater tomato growth should have oc-
curred at the highest levels of compost.
The soluble salt content was high and about equal in both the highest
treatments. Soluble salts can induce deterimental water relationships for
plant growth. If the soluble salt content is sufficiently high root "burn-
ing" or desiccation may result from water movement out of the roots in re-
sponse to the high osmotic gradient. Plant species differ in their toler-
ance to salt content in the soil. Tomatoes are moderately tolerant. A
conductivity reading of 80-100 mmhos per cm is considered moderate. The
conductivity measurements in the residual soil tests were within this range
71
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TABLE 13
TOTAL NUTRIENT UPTAKE BY TOMATOES IN THE GREENHOUSE
Compost Dry Weight/plant (nig)
Treatment
(Tonnes/ha)
Weight
N
P
K
Ca
Mg
0
12.6
96
38
24
40
1 4
1.12
14.1
109
48
28
49
1 7
2.24
15.9
111
58
36
53
18
5.6
14.6
103
63
34
47
18
11.2
24.6
177
110
69
81
27
22.4
26.5
274
126
71
91
31
112
37.5
333
259
149
167
42
224
49.4
475
336
256
219
42
448
46.3
475
339
262
208
27
100 Percent*
45.4
477
369
343
208
31
.05 3.1 59 31 267 68 24
.01 4.2 80 54 350 93 32
*A11 compost; no soil.
72
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TABLE 14
SOIL TEST LEVELS PRIOR TO SAWDUST-POULTRY
MANURE COMPOST ADDITION
Acidity
(pH) NO? NHd P K Ca Mg Mn CEC O.M. SS^
(kg/ha) (meg/1OOg) (%) (mmho/cm)
5.2
7.8
2.9 83 42 280
20
9 0.9
0.7
4.8
*SS = Soluble salts
TABLE 15
RESIDUAL SOIL TEST: SOIL TEST LEVELS AFTER
SAWDUST-POULTRY MANURE COMPOST ADDITIONS AND GROWING
TOMATOES FOR 90 DAYS
Treatment
Acidity N0„
NH
P
K
Ca
Mq
Mn
CEC
SS*
(Tonnes of
(kg/ha)
(meq/
(mmho/cm)
Compost/ha)
(pH)
100a)
0
5.4
0.00
12.3
107
13.1
233
14.3
12.0
1.8
8.0
1.12
5.5
0.37
7.8
118
11.2
227
40.3
19.0
1.7
9.3
2.24
5.6
0.37
10.1
93
14.2
215
13.8
19.8
1.6
10.0
5.6
5.5
0.37
7.5
94
17.9
209
13.4
19.8
1.7
10.3
11.2
5.7
0.75
10.9
110
22.7
257
18.8
22.1
1.6
11.0
22.4
5.9
0.37
9.0
110
36.6
281
22.4
20.2
1.7
14.0
112
6.3
0.37
5.4
120
156.9
526
60.5
28.0
2.9
31.7
224
6.7
0.75
1.5
120
322.7
992
118.8
28.0
4.8
55.0
448
6.7
0.75
5.4
120
322.7
1363
156.8
29.9
7.3
88.3
100% Compost
6.8
1.87
2.7
120
322.7
1793
268.9
29.1
38.4
88.3
LSD *05
0.13
1.21
14.1
2.9
10.1
171
27.9
5.45
2.0
4.90
.01
0.18
1.65
19.3
31.2
13.7
234
38.1
7.44
2.8
6.68
*SS - Soluble salts.
73
-------
for the two highest treatments arid are significantly greater (p=0.01) than
the 224 tonnes/ha treatment. In greenhouse pots the soluble salt effect is
more pronounced due to the restricted soil volume. The soluble salt remains
in the immediate root zone and could affect root growth, nutrient uptake, and
total dry weight production.
Another possible cause for the decreased growth could be the large pore
space in the soil at the high compost rates. During the initial planting of
the tomatoes, it was difficult to saturate the soil at the high compost
levels. When water was applied, it percolated through the soil very rapidly
and the soil retained little moisture in the upper portion of the pots where
the young tomato roots were located. It was difficult to establish an ade-
quate supply of water in this upper portion of the pots. However, once the
compost was saturated with water and the roots grew enough to reach a zone of
adequate moisture, excellent growth occurred. This delay in initial growth
caused by moisture stress may have been the limiting factor in the higher
compost treatments.
An approximation of the range of crop responses to sawdust-poultry
manure compost was determined in the greenhouse study. These rates consisted
of approximately 11.2 tonnes of compost per hectare for a minimum significant
dry weight response and 224 tonnes for a maximum dry weight response for to-
matoes. No detrimental buildup of nutrient levels was experienced and avail-
ability appeared adequate for tomato production. It was concluded that irri-
gation of the field plots might be necessary to establish an adequate plant
stand at high compost levels.
Sawdust-Poultry Manure Compost Applied to Tomatoes in the Field
Field conditions offer a natural set of environmental conditions and
should provide an accurate measure of the acceptability of utilizing sawdust-
poultry manure compost as a soil amendment and, therefore, as a means of land
disposal of animal waste. The objectives of this phase of the study were to
determine the minimum and maximum tomato response to sawdust-poultry manure
compost and to measure the effects of the compost on the chemical and physi-
cal properties of the soil.
A total of 68 mm of rainfall was recorded during the month of April
until the day of transplanting the tomato seedlings. The rainfall was in-
sufficient to provide adequate soil moisture. Therefore, daily watering of
approximately one liter per plant was necessary to establish 100 percent
plant stands. Moisture stress, as indicated by loss of plant turgidity, was
most apparent in the two highest compost levels.
After the plants became established rainfall was not adequate to promote
optimum plant growth. During this drought period two irrigations of 64 mm of
water each were applied to prevent moisture stress. It became evident, with
rainfall and subsequent irrigation, that once the compost-treated plots were
saturated to field capacity, a reduction of visual symptoms of moisture
stress occurred. Increasing compost levels indicated a higher degree of
plant turgidity when compared to the control plants. Both the field and
greenhouse studies indicated that more water is required to establish optimum
74
-------
water conditions with increasing compost applications. However, once the
compost is saturated there is an increase in the length of time before mois-
ture stress symptoms are exhibited in tomato plants.
„ Crowding of the tomato plants within the plots occurred with the 0.37
m per plant density. This high density effectively shaded out grass and
weed competitors but caused difficulty in the harvesting of the tomato fruit.
Current methods of cultivation employed in the production of indeterminate
tomato varieties suggest 1.5 m row widths with 0.3-0.4 m spacing between
plants. It is also suggested that indeterminate tomato plants be either
pruned to one stem and/or staked or trellised (Banadyga, 1970). This row
width and spacing would give approximately one-half the plant population em-
ployed in this study. Also, no staking, trellising, or pruning practices
were employed. The high plant density was intentionally used both to maxi-
mize yields and to measure nutrient supply from the compost in a high yield
si tuation.
Application of large amounts of fertilizer, especially nitrogenous fer-
tilizer, tends to delay maturity in some crop species. Although the first
harvest of tomatoes occurred 64 days after transplanting, it was not until
July 6 (71 days after transplanting) that all plants were producing mature
fruit. The harvest of July 18 was the initial heavy harvest, and each sub-
sequent harvest also produced large amounts of fruit. The time between
transplanting and initial heavy tomato production was 83 days. The normal
length of growth from seedling to maturity for Marion tomatoes is 82 days
(Banadyga, 1970); therefore, no delay in maturity was apparent. However,
the first few harvests indicated that the controls and lower compost levels
produced a light yield of fruit, approximately one to two weeks prior to the
higher compost levels (45, 335, 448 tonnes/ha). Since this was only a light
yield and not consistent, it is felt that it is not significant in terms of
a delay in maturity. The mean fresh weight of the tomatoes ranged from 92 g
per tomato for the control treatment to 119 g for the 448 tonnes/ha treatment.
No attempt was made to separate the tomato fruit into different grades or to
determine marketable tomatoes. Only total yield data were collected.
The total fresh weight yield and yield per ton of compost are given in
Figure 25. Total tomato yield increased with increasing increments of com-
post to a maximum of 166.8 tonnes of fruit per hectare at the 448 tonnes/ha
compost level. As expected, the lower compost treatments exhibited a greater
increase in yield per tonne of compost; however, the yield per tonne of com-
post was low. At the 448 tonnes/ha compost level the response was still
positive. There was no change in the return per tonne of compost between the
22.4 and 44.8 tonnes/ha level (1.4 tonnes yield per tonne compost). The dif-
ference between yields at the two highest compost levels was 30.9 tonnes/ha,
and there was a 112 tonne difference in amounts of compost applied. An eco-
nomic decision could be made at these levels of compost application to deter-
mine if the value of the total yield increase is sufficient to cover the cost
of the additional compost inputs.
Using the least significant differences (LSD) method, minimum signifi-
cant differences at the 5 percent probability level occurred at the 11.2
tonnes/ha compost treatment. The 22.4 tonnes/ha compost treatment was
75
-------
O TOMATO YIELD
A YIELD / TONNE
2 0 30
COMPOST APPLIED
40
(tonnes / ha )
300
400
Figure 25. Total tomato fresh weight yield and yield per tonne of
sawdust-poultry manure compost in the field
-------
significantly different from the control at the 1 percent probability level.
Therefore, minimum significant response of Marion tomato yield to sawdust-
poultry manure compost occurred at the 11.2 and 22.4 tonnes/ha compost treat-
ments (P = 0.05 and 0.01, respectively). Maximum tomato yield occurred at the
maximum compost treatment (448 tonnes of compost per hectare).
The compost nutrients are present in complex organic forms, and plants
take up nutrients primarily in inorganic forms. Mineralization of the compost
nutrients to simpler inorganic forms must occur before the compost nutrients
are readily available for plant growth. The tomato yields indicate that min-
eralization and, hence, nutrient availability was not a limiting factor for
tomato growth in the highest compost treatment. Examining the initial and
residual soil test levels (Tables 16 and 17), and total nutrient uptake (Table
18), one can see an indication as to the amount of nutrients available during
the growth period. Total available nutrients increased with increasing com-
post levels. As previously mentioned, there was little or no delay in the ma-
turing of the tomato fruit. This is an indirect indication that the rate of
nutrient mineralization was adequate for tomato growth. It can concluded
that, in the highest compost treatment, the rate of nutrient mineralization
was adequate to supply both the amounts of nutrients required and at the time
required for adequate tomato growth. The yields were lower at lower levels
of compost, indicating that total amount of nutrients may have been at least
somewhat growth-1imi ting.
The sum of the total nutrient uptake (Table 18) and the residual soil
test level for available nutrients (Table 17) are a measure of total nutrient
availability. It can be seen from the control plots that these sums are
greater (except for P and Mn) than the initial soil test levels. These soil
test levels represent only available nutrients and not total amounts of nu-
trients present. Data from the control plots indicate that mineralization of
nutrients and/or transfer from unavailable to available forms from the total
nutrient pool in the soil has to occur in order that the sum of nutrient up-
take and residual soil nutrient levels be greater than the initial soil nu-
trient levels. The initial soil test for N indicate 7.5 and 38 kg/ha of
available NO3 and NH4, respectively, yet 204.4 kg of N was available (sum of
uptake and residual available nutrients). This N was available due to the
mineralization of the organic nitrogen.
The area utilized in the field study had been fallow the four preceding
years. The residual organic matter of the soil was 2 percent. At 2 percent
organic matter, the surface 15 cm of the soil will contain approximately
45,000 kg of organic matter per hectare. Assuming an organic matter to N
ratio of 20:1, the total N level in the control plots would be approximately
2250 kg/ha. Only 46 kg of this total N pool were initially available. The
total available N (204 kg) is the sum of total N uptake and residual avail-
able soil N levels. The initial available N substracted from the total
available N represents the amount of N mineralized during the tomato growth
period, and this is about 8 percent of the total.
The amount of total N in the 448 tonnes/ha compost level was approxi-
mately 3800 kg. The available N in the control treatments represent avail-
able N from sources other than the compost. An approximate mineralization of
77
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TABLE 16
INITIAL SOIL TEST: SOIL TEST PRIOR TO ADDING SAWDUST-
POULTRY MANURE COMPOST
Acidity O.M. Available Nutrients (kg/ha)
~(pH) t%T N03 NH4 P K Ca Mg Mn
Mean of 25 samples 5.3 2.0 7.5 38 34 95 716 97 29
TABLE 17
RESIDUAL SOIL TEST: SOIL TEST AFTER ADDING
SAWDUST-POULTRY MANURE COMPOST
Compost Treatment
(Tonnes/ha)
Acidity
Available Nutrients (kg/ha)
(pH)
no3
nh4
P
K
Ca
Mg
Mn
0
5.8
2.3
106
24
114
1023
146
25
5.6
5.8
4.1
52
99
116
1190
145
37
11.2
6.2
2.7
180
84
129
1209
188
30
22.4
6.1
3.2
120
97
148
1330
165
40
44.8
6.3
3.6
206
244
247
1307
359
35
336
6.3
8.5
50
613
385
2160
400
52
448
6.4
8.6
111
736
586
3360
428
55
.05
LSD
.01
0.6
0.8
4.3
5.9
176
246
21
30
169
236
893
1252
758
222
12
17
78
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TABLE 18
TOTAL NUTRIENT UPTAKE AND DRY WEIGHT PRODUCTION IN THE
FIELD OF MARION TOMATOES IN RESPONSE TO SAWDUST-POULTRY MANURE COMPOST
Compost Treatment Dry Wt.
N
P K Ca
Mq
Mn
(Tonnes/ha)
(kg/ha)
0
4093
95
8
102
44
13
0.30
5.6
6357
149
18
165
89
25
0.52
11.2
7003
167
22
203
75
24
0.45
22.4
7546
180
41
197
102
32
0.59
44.8
9818
241
61
355
104
31
0.45
336
11822
308
80
436
91
36
0.97
448
14466
399
103
601
128
44
0.81
79
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compost N in the 488 tonnes/ha compost treatment can be calculated by sub-
tracting the available N in the control treatment from the available N at the
448 tonnes of compost per hectare treatment. This determination in the 448
tonnes/ha compost treatment is 312 kg of available N from the compost which
represents mineralization of 8.2 percent of the total N present in the com-
post. Similar arguments can be made for other nutrients.
Generally, increasing levels of compost increased residual soil test
levels (Table 17). The NH4 levels did not follow this trend. The NH4 levels
were maximum in the 44.8 tonnes/ha compost treatment and decreased beyond
this maximum. This was not expected. The high LSD indicates a large error
term, and this error probably is due to soil sampling and processing tech-
nique. The within-treatment range of NH* values for the 448 tonnes/ha treat-
ment was 22 kg/ha to 269 kg/ha. This wiae variation is probably due to
microsite effect or that the soil samples were sieved through a 2 mm sieve
prior to analysis. Of the compost particles, 59 percent were larger than 2.0
mm in diameter. Exclusion of compost from the sample analysis may have in-
duced this variation. The higher compost levels would have indicated a dis-
proportionate decrease over the lower compost rates.
The acidity decreased with increasing compost levels and was significant-
ly different from the control at the 448 tonnes/ha treatment. The decrease
in acidity was associated with nutrient availability and microbial activity.
The N, Ca, Mg, P, and K availability and microbial activity were enhanced
while the availability of Mn changed only slightly as probably did the other
metallic micronutrients except Mo. Total Mn uptake and residual soil test
levels increased with additions of compost. The amount of Mn present masked
the pH-effect on Mn availability.
The NO3 level at the two highest compost treatments was highly signifi-
cantly different from the control plots. However, both these treatments had
a NO3 level of less than 4 ppm. This is much lower than the maximum stan-
dards set forth by the U. S. Public Health Service of 10 ppm NOg-N for drink-
ing water. The low residual levels of NOg indicate that there is no immedi-
ate danger of NOg pollution of the ground water from the compost.
High levels of compost apparently can be applied to a soil to enhance
productivity. Increased nutrient availability, nutrient uptake, and moisture
holding-capacity resulting from employing sawdust-poultry waste compost as a
soil amendment markedly increase tomato yields. Potential pollution due to
excess levels of NOg were not indicated from high compost applications.
If composting is utilized as a means of animal waste disposal, two other
factors must be considered: (1) nutrient capital distribution - that re-
moved by crop harvest and that returned to the soil as vegetative residue;
and (2) long term build-up of nutrient levels as a potential source of nu-
trient pollution of the ground water.
Tomato growth was separated into vegetative and reproductive parts
(Tables 19, 20, and 21). While the major portion of growth was reporductive
and would be removed from the soil as the crop, the vegetative plant parts
80
-------
TABLE 19
TOTAL DRY WEIGHT PRODUCTION OF TOMATOES IN THE FIELD
IN RESPONSE TO SAWDUST-POULTRY WASTE COMPOST
Compost Treatment
(Tonnes/ha)
Mean Dry Weight
Production of
Tomato Plants
(kg/ha)
Mean Dry Weight
Production of
Tomato Fruit
(kg/ha)
Dry Weight Production
of Plants and Fruit
(kg/ha)
0
1448
2645
4093
5.6
2599
3759
6357
11.2
2648
4356
7003
22.4
3006
4542
7546
44.8
3236
6580
9818
336
3684
8138
11822
448
4463
10003
14466
TABLE 20
NITROGEN REMOVAL FROM SOIL BY TOMATO PLANTS AND FRUIT IN
THE FIELD IN RESPONSE TO SAWDUST-POULTRY WASTE COMPOST
Compost Treatment
Plant N
Fruit N
Total N
Fruit N:
Uptake
Uptake
Uptake
Total
(Tonnes/ha)
(kg/ha)
(kg/ha)
(kg/ha)
N ratio
0
27
69
96
0.72
5.6
48
101
149
0.68
11.2
47
119
166
0.72
22.4
57
123
180
0.68
44.8
63
179
242
0.74
336
72
236
308
0.77
448
95
304
399
0.76
81
-------
TABLE 21
PER PLANT DRY WEIGHT PRODUCTION OF TOMATOES IN THE FIELD
IN RESPONSE TO SAWDUST-POULTRY WASTE COMPOST
Compost
Dry Wt. of Vege-
Dry Wt. Produc-
Total Dry Wt.
Fruit Portion
Treatment
tative Plant
tion of Fruit
Production
of Total Wt.
(Tonnes/ha)
(g/Plant)
(g/Plant)
(g/Plant)
(Percent)
0
54
98
152
64
5.6
98
140
238
58
11.2
97
162
260
62
22.4
112
169
280
60
44.8
120
245
365
67
336
137
303
440
69
448
166
372
538
69
.05
33
46
LSD
.01
46
64
82
-------
would be returned to the soil as residue. Any decision as to the amount of
nutrient removal at a given rate of compost application for a givencrop must
take into consideration the amounts of nutrients recycled by returning plant
residue to the soil.
The uptake of N, P, and four cations are considered in various ways
(Tables 22 and 23). The uptake of both N and P increased with increasing
compost applications but the change in N:P ratio indicates clearly that the P
uptake increased more rapidly than did the N (Table 22). The cations exhib-
ited generally an increase in their concentration (expressed as milli-equi-
valents per gram of plant plus fruit) from the control to the 22.4 tonne
level and then a decrease, indicating some carbohydrate dilution at the high-
est compost levels (Table 23). This is another indication that there were
no problems with high salt levels in the soil.
The total water-holding capacity of the sawdust-poultry manure compost
was 3.2 ml per gram of compost. This characteristic increased the total
water-holding capacity of the soil-compost system. Figure 26 indicates mois-
ture content of the control treatment and the 448 tonnes/ha treatment. Al-
though the 448 tonnes/ha treatment increased total-water-holding capacity by
54 percent, available water was increased by only 10.2 percent (available
water is considered to be the amount of water lost between 0.05 bars and 15
bars tension). There is a five-fold difference between total water-holding
capacity and available water. This results from a portion of the water being
retained by the compost at 15 bars tension. The compost imparts a large
water-holding capacity to the soil and also holds more water at high tensions
than the soil used in this study. Therefore, only a portion of the addition-
al water will be available. A 10.2 percent increase in available water, how-
ever, is a tremendous asset to most mineral soils. Not only will this de-
crease the droughtiness of excessively drained soils but will also reduce
leaching loss from these soils.
The slope of the curve from 0 to 50 cm tension indicates a rapid water
loss. This is a result of the large pore space in the soil-compost mixture
(Figure 26). This large pore space allows rapid infiltration and perme-
ability and thus would decrease the potential for soil erosion. After har-
vesting the tomato plants, it was noted that fine sand had adhered to the
above-ground portions of the tomato plants but much less so at the high com-
post treatments than at the lower levels.
Paper-Poultry Manure Compost Applied to Tomatoes in the Field
Paper was utilized as an alternative carbonaceous material in the com-
posting process. Field plots were established to investigate fresh weight
yield of tomato plants and fruit, nutrient uptake by tomatoes, and soil
chemical properties resulting from the addition of paper-poultry manure com-
post to the soil. Differences in chemical and physical properties between
the sawdust-poultry manure compost and the paper-poultry manure compost re-
sulted in different soil and plant responses.
Rainfall was adequate for tomato growth, and no supplemental irrigation
was necessary. Immediately after transplanting tomato seedlings to the field,
83
-------
TABLE 22
N AND P CONTENT OF TOMATOES: TOTAL UPTAKE FROM SAWDUST-POULTRY
MANURE COMPOST
Total Dry Wt.
N
P
N:P ratio
Compost
Production/plant
Total Uptake
Total Uptake
Total N:
(Tonnes/ha)
(g)
(g)
(g)
Total P
0
152
3.55
0.30
11.83
5.6
236
5.53
0.68
8.13
11.2
260
6.17
0.85
7.26
22.4
280
6.70
1 .53
4.38
44.8
365
8.98
2.26
3.97
336
440
11 .43
2.96
3.86
448
538
14.83
3.84
3.86
TABLE 23
CATION CONTENT OF FIELD-GROWN TOMATOES IN MILLIEQUIVALENTS PER
GRAM OF DRY WEIGHT
Total Dry Wt.
Cation Content
Compost
Production/plant
K
Ca Mq
Mn
(Tonnes/ha)
(g)
(meq/g)
0
152
0.63
0.53
0.27
0.27
5.6
236
0.66
0.69
0.33
0.29
11.2
260
0.74
0.54
0.30
0.23
22.4
280
0.67
0.67
0.35
0.23
44.8
365
0.93
0.53
0.27
0.16
336
440
0.95
0.38
0.25
0.29
448
538
1.03
0.44
0.25
0.20
-------
100
448 tonnes/ho
80
C ONTROL
o
>
.9
o-
60
H
Ui
iLl
tr
3
VI
13.0 ml
0
0.2
0.3
0.4 10
0.1
20
TENSION (bars)
Figure 26. Water holding capacity of soil and soil-compost mixture over
a range of tensions from 0 to 15 bars
85
-------
the plots received an intense rainfall 4.57 cm. This rainfall caused a sur-
face crust to be formed on the 112 tonnes/ha compost treatment. No crust was
observed on any other treatment. At two weeks of growth the plants on the
112 tonnes/ha treatments were noticeably smaller than the border plants sur-
rounding this treatment. This reduced growth was apparent until approximate-
ly 60 days after transplanting. At approximately 60 days the surface crust
was no longer evident. The surface crust probably resulted from the intense
rainfall and the shape of the compost particles. Rain drop impact may have
arranged the plate-like paper compost particles in an overlapping configura-
tion which effectively sealed the soil surface, resulting in decreased aera-
tion and water infiltration. This would decrease aerobic microbiological
activity, creating a detrimental effect on mineralization of compost nutri-
ents and, hence, the availability of nutrients required to maintain adequate
tomato growth.
Total fresh weight yield of tomato fruit and the tonnes of fresh weight
yield per tonne of compost are given in Figure 27. Increasing compost levels
increased fresh weight yield per hectare to a maximum in the 22.4 tonnes com-
post level. The 112 tonnes/ha treatment yield was slightly less than the
22.4 tonnes/ha treatment. Fresh weight yields of 18, 29, 38, 47, and 43
tonnes/ha were realized at the 0, 2.2, 11.2, 22.4, and 112 tonnes of compost
per hectare, respectively. Minimum significant response (p=0.05) occurred at
the 11.2 tonne compost level when compared to the control treatment. Maxi-
mum fresh weight yield was highly significantly different from the control
treatment but was not significantly different from the other compost treat-
ments. The decrease in fresh weight yield at the 112 tonne compost treat-
ment was not significant when compared to the other compost treatments.
The tonnes of fresh weight yield per tonne of compost applied indicated,
as expected, that the efficiency of the compost for increasing tomato yield
decreased with additional increments of compost. The low tonnes of fresh
weight yield per tonne of compost applied at the high rate indicates that
very little yield increase could be expected from higher compost levels. Ad-
ditionally, the data indicate that a further reduction in yield may have oc-
curred at higher compost levels. Fresh weight yield was reduced due to the
experimental conditions under which the tomatoes were grown. The tomatoes
were transplanted to the field one month later than the normal planting time.
A short harvesting period and an early terminal harvest also decreased the
potential for maximum tomato production. Tomatoes were harvested 8 times as
they matured. The 112 tonnes/ha compost treatment had a range of 30-45 per-
cent immature fruit at the terminal harvest. This indicates that the matura-
tion of the high compost treatment was delayed. All treatments would have
had a higher yield if the harvesting period has been extended. The average
size of the tomato fruit was 69 g per fruit in the control treatment and 106
g in the 22.4 tonnes/ha treatment.
The same soil type was utilized in both field studies. The sawdust com-
post and the paper compost plots were located adjacent to each other. The
initial soil test levels are given in Table 16. Nutrient availability can be
measured in terms of total uptake and by examining the residual soil fertili-
ty levels. Table 24 gives the total nutrient uptake by tomato tops and fruit
86
-------
50
o
.c
•
c
c
o
ill
>
<
Z
o
K-
O TOMATO YIELD
A YIE LD / TONNE
5 10 15 20 25 112
COMPOST APPLIED (tonnes/ha)
Figure 27. Total tomato
per tonne of
in the field
fresh weight yield and yield
paper-poultry manure compost
87
-------
TABLE 24
NUTRIENT UPTAKE BY TOMATOES IN THE FIELD AT VARIOUS LEVELS OF
PAPER-POULTRY MANURE COMPOST
A. UPTAKE BY TOMATO PLANT TOPS
Compost Treatment
N
P
K
Ca
Mg
Mn
(Tonnes/ha)
(kq/ha)
0
19
1.7
27
18
6.2
0.07
2.2
31
3.2
63
34
9.2
0.96
11.2
27
2.9
58
36
8.7
0.78
22.4
38
6.5
92
45
11 .4
0.77
112
62
13.3
138
50
13.0
1.22
B. UPTAKE BY TOMATO
FRUITS
Compost Treatment
N
P
K
Ca
Mg
Mn
(Tonnes/ha)
(kq/ha)
0
34
4.5
45
9
2.0
0.02
2.2
45
7.2
71
15
2.9
0.02
11.2
91
11.5
108
18
4.4
0.03
22.4
91
12.0
126
47
5.6
0.08
112
101
13.1
140
21
4.9
0.04
C. TOTAL NUTRIENT UPTAKE BY TOMATO
TOPS AND FRUIT
Compost Treatment
N
P
K
Ca
Mg
Mr.
(Tonnes/ha)
(kq/ha)
0
54
6.2
72
27
8.2
0.09
2.2
76
10.4
133
48
12.1
0.99
11.2
100
14.6
166
54
13.1
0.82
22.4
129
18.5
217
92
17.0
0.85
112
162
26.4
278
72
17.9
1.27
88
-------
at the various compost levels. Nutrient uptake generally increased with in-
creasing compost levels. Total nutrient uptake was maximized at the 112
tonnes/ha compost level except for Ca which decreased slightly at this level.
Maximum yields did not correspond with maximum nutrient uptake. This factor
combined with the number of immature fruit at the terminal harvest for this
treatment indicates that these plants were in a stage of vegetative rather
than reproductive growth. Nutrient availability was not a limiting factor in
the tomato growth. Time of availability of the nutrients may not have corre-
sponded with the maximum nutritional requirements of the plants and, hence,
could have been limiting.
Nutrient uptake by tomato fruit was greater than by the tomato tops for
N, P, and K (Table 24). However, Ca and especially Mg and Mn uptake was
greater in the tomato tops. The nutrients taken up by the tomato tops will
be returned to the soil as plant residue. The amount of nutrients removed
by the tomato fruit is the amount of nutrients permanently removed from the
site. This is the most important consideration in terms of nutrient removal
from the applied animal waste compost. Since N is the chief source of po-
tential pollution from animal waste, the treatment which removes the most N
would result in the maximum decrease in this pollution potential. Thirty
five kilograms of N per hectare were removed in the tomato fruit in the con-
trol treatment while 101 kg were removed in the 112 tonnes/ha treatment. The
net difference of 66 kg of N per hectare can be attributed to the effect of
the compost. It is not possible to state that the additional N actually came
from the compost since some additional mineralization of soil N may have oc-
curred under the influence of the extra available carbon and energy of the
compost.
Residual soil test levels represent the changes in soil chemistry re-
sulting from soil-compost-plant interactions. They represent the amounts of
nutrients that are present in available form but which were not taken up by
the plants during the growth period.
The acidity decreased with increasing compost levels (Table 25). The pH
value at the 11.2 tonnes/ha level was significantly higher (p = 0.05) than
the control treatment. The 22.4 and 112 tonne treatments were even less
acidic and their differences from the control were highly significant. This
rise in pH value in the compost treatments would increase the availability of
all the nutrients analysed except Mn. Since Mn values also increased, it is
evident that the amounts of Mn present overcame the pH effect on its avail-
ability. The activity of bacteria, fungi, and actinomycetes would also be
enhanced by the decreasing acidity. By examining the nutrient levels at the
112 tonne/ha treatment, it can be concluded that the amount of available nu-
trients would not be limiting to tomato growth. The high residual fertility
levels indicate a very high rate of mineralization.
In conclusion, paper-poultry manure compost, at high levels of applica-
tion to soil, under intensive rain fall, may form a surface crust and reduce
plant growth. Some excess available C may be present which would result in
some temporary nutrient immobilization. With a longer and more optimum grow-
ing period more mineralization of compost nutrients would have occurred, more
nutrients would have been absorbed, and higher yields would have been
39
-------
TABLE 25
INITIAL AND RESIDUAL SOIL TEST: SOIL TEST VALUES BEFORE AND AFTER
ADDING PAPER-POULTRY WASTE COMPOST AND GROWING TOMATO CROP
A. INITIAL SOIL TEST VALUES
A c i d i ty NO^ NHL P K Ca Mq Mn
(PH) (k9/.ha) . . ,
Mean of 45 samples 5.8 2.1 40 48 162 1157 146 26
B. RESIDUAL SOIL TEST VALUES
Compost Treatment
Acidity
NO.
nh4
P
K
Ca
Mq
Mn
(Tonnes/ha)
(PH)
O
(kq/ha)
0
5.7
6.7
35
60
144
1003
128
20
2.2
5.8
10.4
38
84
297
1290
137
25
11.2
6.1
5.9
44
159
485
1971
178
21
22.4
6.3
8.2
53
299
699
2598
224
30
112
6.8
2.2
85
968
2187
6003
547
38
.05
0.4
5.3
15
26
271
675
39
13
LSD
.01
0.6
7.6
21
38
394
982
57
19
90
-------
obtained. The higher rates of compost application had a residual nitrate
level of less than 4 ppm which would not be a hazzard either on site or as
a contributor to ground water pollution.
91
-------
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Management and Pollution'Abatement. (Proc. Intl. Symp. Livestock Wastes,
April 19-22, Ohio State Univ.) Publ. ASAE, St. Joseph, Mich. pp. 163-
165.
Wolfe, L. P., Jr. and S. Dunn. 1953. Sawdust composts in soil improvement
I. Plant Soil 4:223-234.
Wylie, J. C. " I960. Composting- I^P.C.G. Isaac (ed.) Waste Treatment.
Proc. Second Symp. Treatment of Waste Waters. Pergamon Press. New
York. pp. 349-366.
95
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TECHNICAL REPORT DATA
(Please read InUruclions on the reverse before completing) ^ ^ ^ ... y
1 . REPORT NO. 2.
EPA-600/2-78-154
3'P tf'
4. TITLE AND SUBTITLE
ANIMAL WASTE COMPOSTING WITH CARBONACEOUS MATERIAL
5. REPORT DATE
September 1978 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTrlOR(S)
William S. Galler, Charles B. Davey, William L. Meyer,
W. N. Reed, Domadar S. Airan
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
North Carolina State University
Raleigh, North Carolina 27650
10. PROGRAM ELEMENT NO.
DC618
11. CONTRACT/GRANT NO.
Grant No. 00270
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory--Cin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: Clarence Clemmons (513) 684-7394
16. ABSTRACT
High rate thermophilic composting of animal wastes with added carbonaceous waste
materials followed by land application has considerable potential as a means of
treatment and useful final disposal of these wastes. The process described in this
report utilizes a mechanically mixed, thoroughly aerated, thermophilic first stage
in which the readily available carbonaceous materials are utilized by bacteria dur-
ing the stabilization of the nitrogenous wastes. This is followed by a curing period
in which the hoilocellulose is partially decomposed principally by fungi. The compost
may then be added to soil.
The testing of the compost's effect of plant growth was done in three phases.
The first phase involved spreading the compost over grass as a top-dressing; the
second was a greenhouse study using tomatoes, wheat, millet, and beans; while the
third was a field test on tomato crops. In all three tests, the compost exhibited
significant beneficial effects. The mulching experiment yielded increases in the
dry weights of grasses of up to 57 percent over the control. The greenhouse experi-
ments showed increases in dry weights of up to 400 percent for tomatoes and wheat
over the control. Field studies, indicated that, both the tomato size and total
yield over the growing season incresed with increasing compost application.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COS ATI I-'icId/Group
Agricultural Wastes
Composts
Field Tests
Organic Wastes
Aerobic composting
Animal wastes
Plant response
Sol id wastes
Themophilic composting
2C
6M
13B
13. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
t
20. SECURITY CLASS (This page)
Unclassified
22.PRICE ! 1/r~
EPA Form 2220-1 (9-73)
vV U.S. GOVERNMENT PRINTING OFFICE: 1978-757-140/1463 Region No. 5-11
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