WATER POLLUTION CONTROL RESEARCH SERIES
13040 DEM 01/71
CHARACTERISTICS OF WASTES FROM
SOUTHWESTERN CATTLE FEEDLOTS
U.S. ENVIRONMENTAL PROTECTION AGENCY
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WATER POLLUTION CONTROL RESEARCH SERIES
The. Water Pollution Control Research Series describes the
results and progress In the control and abatement of pollution
in our Nation's waters. They provide a central source of
information on the research, development, and demonstration
activities in the Environmental Protection Agency, through
inhouse research and grants and contracts with Federal, State,
and local agencies, research institutions, and industrial
organizations.
Inquiries pertaining to Water Pollution Control Research Reports
should be directed to the Head, Publications Branch (Water),
Research Information Division, R&M, Environmental Protection
Agency, Washington, B.C. 20460.
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CHARACTERISTICS OF WASTES FROM SOUTHWESTERN CATTLE FEEDLOTS
by
Texas Tech University
Water Resources Center
Lubbock, Texas 79409
for the
ENVIRONMENTAL PROTECTION AGENCY
Project #13040 DEM
January, 1971
For sale by the Superintendent of Documents. U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.00
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EPA Review Notice
This report has been reviewed by the Environmental Protection
and approved for publication. Approval does not signify
that the contents necessarily reflect the views and policies
of the Environmental Protection Agency nor does mention of
trade names or commercial products constitute endorsement or
recommendation for use.
ii
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ABSTRACT
Research was conducted to determine the characteristics of waste
from Southwestern cattle feedlots. Experimental feedlots located on
the Texas Tech Campus were used in performing the studies. The feed-
lots were generally operated in a manner conforming to normal commer-
cial feeding operations in the area. They were provided with collec-
tion pits that allowed the quantity of runoff to be measured accurately,
and samples of runoff were collected routinely both during rainstorms
and from the collection pits. Manure samples were also collected
routinely for analysis.
Results of the research show that the quantity of runoff per unit
area of concrete-surfaced lots is substantially greater than the quan-
tity per unit area of dirt-surfaced lots, and that the concentrations
of pollutants in concrete lot runoff are substantially higher than
corresponding concentrations in runoff from dirt-surfaced lots.
The quantity of solid waste derived from cattle being fed an all-
concentrate ration is less than half as great as the quantity derived
from cattle being fed a 12 percent roughage ration. Additional studies
showed that all solid waste derived from cattle feeding operations are
readily compostible, although the rate of composting is influenced to
some extent by the type of ration, moisture content of the waste on
the feedlot floor, and other factors.
Agronomic studies indicate that runoff can be used for irrigation
of crops, but extreme caution is required in the application of run-
off to crops to prevent damage to them.
This report was submitted in fulfillment of Project No. 13040
DEM—Rev. under the partial sponsorship of the Environmental Protection
Agency.
iii
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CONTENTS
Page
ABSTRACT in
CONTENTS v
FIGURES viii
TABLES x
CONCLUSIONS 1
RECOMMENDATIONS 3
INTRODUCTION 5
Project Objectives 6
Scope 7
REVIEW OF PREVIOUS WORK 9
Characteristics of Cattle Feedlot Waste 9
Handling and Disposal Methods 10
Land Utilization 10
Anaerobic Digestion 11
Anaerobic Lagoons 11
Aerobic Lagoons 12
Oxidation Ditch 12
Aerobic Composting 12
Complete Treatment 12
Dehydration and/or Incineration 13
Nutrient Recycling 13
European Methods 13
Miscellaneous Methods 13
Implications for the Future 13
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Page
Research Needs 13
STUDIES WITH CONCRETE-SURFACED FEEDLOTS 17
Animal Feeding Studies 17
Experiment I 17
Experiment II 17
Experiment III 20
Results of Feeding Trials 21
Solid Waste Accumulation 21
Runoff From Concrete-Surfaced Feedlots 22
Rainfall-runoff relationships 23
Quality and Quantity Relationships 27
Effect of Slope on Waste Movement 28
STUDIES WITH DIRT-SURFACED FEEDLOTS 29
Animal Feeding Studies 29
Runoff From Dirt-Surfaced Feedlots 31
Quality and Quantity Relationships 34
Interpretation of Results . 35
STUDIES WITH MODIFIED ENVIRONMENT FEEDING FACILITIES 37
Environmental Chamber 37
Anaerobic Treatability Studies 37
Operational Procedures 37
Analyses 40
Seeding 40
Objectives 40
Staged Digestion 40
BOD and COD Reduction 40
vi
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Page
Gas Production and Composition 41
pH 41
Volatile Acids and Alkalinity 45
C-H-N Analyses 45
«
Aerobic Treatability Studies 45
LABORATORY SIMULATION STUDIES 49
Experiments with Percolation Cylinders 49
Experiments with Tilting Table 52
Results 54
RELATED RESEARCH AT TEXAS TECH 69
Composting Studies 69
Research Findings 69
Carbon-Nitrogen Ratio 70
Moisture Content 71
Insect Infestation 71
Oxygen Requirements 71
Drum Stabilization 72
Time for Stabilization 72
Open Air Piles 72
Summary 73
Agronomic Studies 73
ACKNOWLEDGMENTS 75
LITERATURE CITED 77
LIST OF PUBLICATIONS 85
APPENDIX 87
vi i
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FIGURES
Page
FIGURE 1. LAYOUT OF CONCRETE-SURFACED FEEDLOTS
USED ON PROJECT 18
FIGURE 2. PRECIPITATION-RUNOFF RELATIONSHIP FOR
CONCRETE-SURFACED FEEDLOTS ON WHICH
ALL-CONCENTRATE RATIONS WERE FED 24
FIGURE 3. PRECIPITATION-RUNOFF RELATIONSHIP FOR
CONCRETE-SURFACED FEEDLOTS ON WHICH
12 PERCENT ROUGHAGE RATIONS WERE FED 26
FIGURE 4. LAYOUT OF DIRT-SURFACED FEEDLOTS USED
ON PROJECT 30
FIGURE 5. PRECIPITATION-RUNOFF RELATIONSHIP FOR
DIRT-SURFACED FEEDLOTS 33
FIGURE 6. SCHEMATIC SKETCH SHOWING THE ENVIRONMENTAL
CHAMBERS AND ASSOCIATED TREATMENT FACILITIES ... 38
FIGURE 7. SCHEMATIC SKETCH OF THE ANAEROBIC DIGESTION
PROCESS USED FOR CATTLE WASTE 39
FIGURE 8. GAS PRODUCTION AS A FUNCTION OF TIME IN A
TWO-STAGE ANAEROBIC DIGESTER 42
FIGURE 9. PERCENTAGE METHANE AS A FUNCTION OF TIME IN
A TWO-STAGE ANAEROBIC DIGESTER 43
FIGURE 10. pH AS A FUNCTION OF TIME IN A TWO-STAGE
ANAEROBIC DIGESTER 44
FIGURE 11. ALKALINITY AND VOLATILE ACIDS AS FUNCTIONS
OF TIME IN A TWO-STAGE ANAEROBIC DIGESTER 46
FIGURE 12. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF ONE PERCENT AND
PRECIPITATION RATE OF ONE INCH PER HOUR 56
FIGURE 13. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF ONE PERCENT AND
A PRECIPITATION RATE OF TWO INCHES PER HOUR .
FIGURE 14. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF ONE PERCENT AND
A PRECIPITATION RATE OF THREE INCHES PER HOUR
57
58
viii
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FIGURE 15. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF THREE PERCENT
AND A PRECIPITATION RATE OF ONE INCH PER HOUR .
FIGURE 16. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF THREE PERCENT
AND A PRECIPITATION RATE OF TWO INCHES PER HOUR
FIGURE 17. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF THREE PERCENT
AND PRECIPITATION RATE OF THREE INCHES PER HOUR
FIGURE 18. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF SIX PERCENT
AND PRECIPITATION RATE OF ONE INCH PER HOUR . .
FIGURE 19. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF SIX PERCENT
AND PRECIPITATION RATE OF TWO INCHES PER HOUR .
FIGURE 20. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF SIX PERCENT AND
PRECIPITATION RATE OF THREE INCHES PER HOUR . .
FIGURE 21. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF NINE PERCENT
AND PRECIPITATION RATE OF ONE INCH PER HOUR . .
FIGURE 22. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF NINE PERCENT
AND PRECIPITATION RATE OF TWO INCHES PER HOUR .
FIGURE 23. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT
RUNOFF FOR A FEEDLOT SLOPE OF NINE PERCENT
AND PRECIPITATION RATE OF THREE INCHES PER HOUR
59
60
61
62
63
64
65
66
67
IX
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TABLES
RATION COMPOSITION (percent, air-dry basis)
Page
19
TABLE 1.
TABLE 2. MEAN FEEDLOT PERFORMANCE OF STEERS IN
EXPERIMENT I (POUNDS: 173 DAYS)3 19
TABLE 3. MEAN FEEDLOT PERFORMANCE OF HEIFERS IN
EXPERIMENT II (POUNDS: 136 DAYS)9 20
TABLE 4. MEAN FEEDLOT PERFORMANCE OF STEERS IN
EXPERIMENT III (POUNDS: 121 DAYS) 21
TABLE 5. SOLID WASTE ACCUMULATION DURING THE
FEEDING PERIODS 22
TABLE 6. TOTAL PRECIPITATION AND RUNOFF FROM CONCRETE-
SURFACED FEEDLOTS FROM AUGUST 20, 1969
THROUGH OCTOBER 21, 1969. ALL-CONCENTRATE
RATION WAS FED DURING THIS PERIOD 23
TABLE 7. TOTAL PRECIPITATION AND RUNOFF FROM CONCRETE-
SURFACED FEEDLOTS FROM AUGUST 20, 1969
THROUGH OCTOBER 21, 1969. TWELVE PERCENT
ROUGHAGE RATION WAS FED DURING THIS PERIOD .... 25
TABLE 8. CONCENTRATIONS OF POLLUTANTS IN RUNOFF FROM
CONCRETE LOT RESULTING FROM PRECIPITATION
STARTING AT 11:00 P.M. ON AUGUST 24, 1969 27
TABLE 9. CONCENTRATIONS OF POLLUTANTS IN RUNOFF
FROM CONCRETE-SURFACED LOT ON WHICH CATTLE
WERE FED ALL-CONCENTRATE RATION 27
TABLE 10. CONCENTRATIONS OF POLLUTANTS IN RUNOFF FROM
CONCRETE-SURFACED LOT ON WHICH CATTLE WERE
FED ROUGHAGE-CONCENTRATE RATION 28
TABLE 11. MEAN FEEDLOT PERFORMANCE OF STEERS IN
EXPERIMENT I (POUNDS: 173 DAYS)3 29
TABLE 12. TOTAL PRECIPITATION AND RUNOFF FROM DIRT-SURFACED
FEEDLOT FROM AUGUST 20, 1969 THROUGH OCTOBER
21, 1969. ALL-CONCENTRATE RATION WAS FED
DURING THIS PERIOD 31
TABLE 13. TOTAL PRECIPITATION AND RUNOFF FROM DIRT-
SURFACED FEEDLOT FROM AUGUST 20, 1969 THROUGH
OCTOBER 21, 1969. TWELVE PERCENT ROUGHAGE
RATION WAS FED DURING THIS PERIOD 32
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TABLE 14. TOTAL PRECIPITATION AND RUNOFF FROM
CONCRETE AND DIRT-SURFACED FEEDLOTS
FOR THE PERIOD APRIL 11, 1969 THROUGH
JUNE 13, 1969 32
TABLE 15. CONCENTRATIONS OF POLLUTANTS IN RUNOFF
FROM DIRT LOT RESULTING FROM PRECIPITATION
STARTING AT 11:00 P.M. ON AUGUST 24/1969 34
TABLE 16. AVERAGE CONCENTRATIONS OF POLLUTANTS IN
RUNOFF FROM DIRT LOT ON WHICH CATTLE WERE
FED ALL-CONCENTRATE RATION 34
TABLE 17- AVERAGE CONCENTRATIONS OF POLLUTANTS IN
RUNOFF FROM DIRT LOT ON WHICH CATTLE WERE
FED ROUGHAGE-CONCENTRATE RATION 35
TABLE 18. SUMMARY OF AVERAGE RESULTS OBTAINED FROM
A COMPLETELY MIXED TWO STAGE DIGESTER WITH
A CAPACITY OF 30 GALLONS PER STAGE, OPERATING
AT 97° F AND A DAILY FEED RATE OF SIX GALLONS ... 41
TABLE 19. CONCENTRATIONS OF COD IN WATER PERCOLATING
THROUGH DEPTH OF MANURE IN COLUMNS AS
SHOWN (mg/1) 50
TABLE 20. CONCENTRATIONS OF VOLATILE SOLIDS IN WATER
PERCOLATING THROUGH DEPTH OF MANURE IN
COLUMNS AS SHOWN (mg/1) 50
TABLE 21. CONCENTRATIONS OF ALKALINITY IN WATER
PERCOLATING THROUGH DEPTH OF MANURE IN
COLUMNS AS SHOWN (mg/1) 51
TABLE 22. CONCENTRATIONS OF AMMONIA NITROGEN IN WATER
PERCOLATING THROUGH DEPTH OF MANURE IN
COLUMNS AS SHOWN (mg/1) 51
TABLE 23. FEEDLOT SLOPE AND PRECIPITATION RATES
STUDIED IN THE TILTING TABLE EXPERIMENT 55
xi
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CONCLUSIONS
The conclusions contained herein were derived from careful con-
sideration of data obtained in laboratory and field studies. They
are limited by the scope of the project and by the methods used, and
are applicable to the cattle feeding industry of the Southwest. They
may not in all cases apply directly to other regions of the United
States.
1. The concentrations of pollutants in runoff derived from pre-
cipitation on Southwestern cattle feedlots are influenced to
some extent by factors such as ration composition, antecedent
moisture conditions, depth of manure, slope of lot, and den-
sity of cattle, but such variations are of no real signifi-
cance from the standpoint of water quality control. Pollutant
concentrations are in the range of one to more than two orders
of magnitude higher than those normally found in untreated
municipal sewage.
2. Treatment, by conventional anaerobic or aerobic systems, of
runoff derived from precipitation on Southwestern cattle feed-
lots is infeasible because of the very high concentrations of
pollutants in such runoff and, more importantly, because of
the extremely erratic frequency with which runoff occurs. In
no case should this runoff be released to surface water.
3. Concentrations of pollutants in runoff resulting from precipi-
tation on concrete-surfaced lots are two to four times greater
than corresponding concentrations derived from dirt-surfaced
lots.
4. The quantity of solid waste accumulating on the feedlot floor
is a direct function of the fraction of roughage in the fin-
ishing ration. Mean solid waste accumulations of 2.3 pounds
per head per day (dry weight basis) were obtained from cattle
on an all-concentrate ration, 4.4 pounds per head per day
from cattle on a ten percent roughage ration, and 5.0 pounds
per head per day from cattle on a 12 percent roughage ration.
5. The fraction of incident precipitation that runs off concrete
lots is about twice the fraction that runs off dirt-surfaced
lots. Decreased roughage concentration increases the quan-
tity of runoff on concrete-surfaced lots.
6. Stocking rates above 40 square feet per animal on concrete-
surfaced lots do not appear to enhance animal performance.
At this stocking rate, the quantity of runoff per animal is
somewhat less than the corresponding quantity derived from
cattle on dirt-surfaced lots at conventional stocking rates
using the same ration.
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7. Limited feeding trials utilizing a roof to eliminate runoff
showed no apparent beneficial or detrimental effects on cat-
tle performance.
8. Increasing the slope of concrete-surfaced feedlots from 7-1/2
to 15 percent made the lots virtually self-cleaning without
any apparent adverse affect on animal performance.
9. Treatment of accumulated solid wastes from Southwestern cat-
tle feedlots by aerobic composting is technologically feasible
regardless of the type of operation. However, the rate of
composting varies with type of ration, moisture content of
waste, etc.
10. Extreme caution must be exercised in the application of feed-
lot runoff to agricultural crops. Preplant applications
seriously inhibit seed germination and application to seed-
ling crops seriously damages the crops. With proper timing,
limited applications can be made to most well established
crops. Repeated applications of runoff to soil results in a
buildup of Na , Cl~, and other ions in the soil.
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RECOMMENDATIONS
From the literature and by general recognition, the following
recommendations and design criteria are applicable to Southwestern
beef cattle feedlot waste management:
Beef cattle feedlot waste management involves two basic interre-
lated pollutional problems, (a} the management, removal and disposal
of the soTid waste that accumulates on the feedlot surface and (b) the
treatment and disposal of the liquid runoff resulting from precipita-
tion. Disposal of both solid and liquid wastes should be accomplished
in a way that will prevent undue pollution of the environment.
1. All surface water should be prevented from flowing into the
feedlot area. This may be accomplished by use of an appro-
priate system of diversion channels, terraces, or ditches.
2. The feedlot should have a minimum slope to provide surface
drainage. The slope should be uniform to prevent localized
channeling. Each lot should drain directly into a drainage
channel without flowing across adjacent lots.
3. Runoff storage pits should be lined if located in a porous
type soil to prevent possible pollution of underground water.
4. The spreading of runoff water on a porous soil surface
should be limited to light irrigation applications to prevent
movement of pollutants into the soil column.
5. Undiluted runoff should not be applied to soil as a preplant
irrigation, and it should not be applied to seedling plants.
Caution should be used in spreading runoff on any types of
growing crops.
From the results and conclusions of this investigation, these
further management considerations can be recommended.
1. Reducing the roughage content of finishing rations for cattle
from 12 percent to zero would alone eliminate approximately
one-half of the solid waste accumulation on the feedlot sur-
face.
2. The feedlot could be covered to eliminate runoff. No runoff
occurs from roofed feedlots provided that roof drainage does
not flow through the accumulated waste.
3. Frequent cleaning of concrete feedlot surfaces results in a
less polluted runoff provided cleaning takes place before
the lot surface is completely covered with waste. After the
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lot is covered, further accumulation does not materially
affect the quality of runoff.
4. A concrete-surfaced feedlot offers the possibility of de-
creased area for each head of livestock on feed. By reducing
area requirements to 40 or fewer square feet per head, the
quantity of runoff from a feedlot holding a given number of
animals is reduced.
5. Increasing the slope on concrete feedlots to about 15 percent
makes them essentially self-cleaning provided a means is
available for removing the solid waste that accumulates on
the lower side, and provided the lots are not too long.
6. Land disposal is probably the only economically feasible
method of ultimate disposal of solid waste at this time. Con-
sideration should be given to the availability of land for
waste disposal in selecting the feedlot site.
7. Consideration should be given to composting solid waste as a
normal part of the feedlot operation to reduce the land, air,
and water pollution potential of the accumulated waste, and
to reduce the volume of the accumulated waste.
8. It is recommended that further studies be made to determine
the feasibility of utilizing a roof, steeply sloped floors,
slotted floors, and various types of automatic waste handling
systems under actual feeding conditions. It is therefore re-
commended that a highly flexible pilot plant be built to test
these systems and to determine the optimum design of feedlots
for the Southwestern part of the United States.
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INTRODUCTION
The cattle feeding industry studied in this project is located
on the South High Plains Region of Northwest Texas at an altitude
generally in excess of 3000 feet. The South Plains is a segment of
the Llano Estacado bordered on the north by the Canadian River, on
the east by the caprock escarpment, and on the west and southwest by
the Pecos River.
The drainage surface is generally featureless except for small
playas and small stream valleys. The numerous shallow playas that
dot the area fill during periods of precipitation to form small lakes.
A few dry stream valleys of Brazos River tributaries constitute the
only surface water flow from the area.
The climate is semi-arid transitional, ranging from the more
humid climates of the east and south to the desert climates of the
west. The normal precipitation averages about 18 inches per year.
Most of the rain occurs during May, June, and July and during late
August, September, and October when warm moist tropical air from the
Gulf of Mexico flows over the area. Thermal convection flow of this
moisture laden air mass results in moderate to heavy afternoon and
evening thunderstorms. During winter months the occasional light
snow remains on the ground only a short period of time. In general,
precipitation is erratic and ranges from over 40 inches to less than
9 inches per year. Monthly values from 0 to 14 inches have been
recorded.
The normal annual temperature is about 60 degrees Fahrenheit
with a normal daily maximum in July in the nineties, and a normal
daily minimum in January in the twenties. The mean wind speed is
very high since the uniform topography offers little resistance to
surface air flow. The high average rate of air movement and the
generally low humidity result in a high evaporation rate for the
region. The high altitude and generally clear skies allow for a
rapid radiation from the ground surface during nighttime periods.
The rapid cooling of the evening hours and the high solar radiation
of the daylight hours usually provide average diurnal swings of 30
degrees Fahrenheit.
The water supply for nearly all agricultural, municipal, and
industrial consumers is the Ogallala Aquifer which underlays most
of the South High Plains. The Ogallala is a relatively thin aquifer
with a maximum saturated thickness of 350 feet. At present the
water table, on the average, has been drawn down about 100 to 125
feet.
The commercial production of slaughter cattle in the High Plains
of West Texas has increased from about 500,000 head in 1960 to a
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current production of almost four million head per year. This phenom-
enal rise in production has occurred because of the availability of
abundant supplies of both feeder cattle and grain sorghum, and the
realization by local interests that it was uneconomical to ship both
feeder cattle and feed grains out of the area for subsequent conver-
sion of grain into beef. Only two states, Iowa and Nebraska, currently
produce more fed cattle than the High Plains of West Texas, and feedlots
now on the drawing boards for West Texas will soon make this area pre-
eminent in the production of fed beef cattle.
In the early stages of the growth of the feedlot industry in West
Texas, feedlots tended to locate on the few streams in the area.
Tierra Blanca Draw, which runs through the south portion of Hereford,
Texas, was the focal point of much of the initial concentration of
feedlots. More recent practice has been to locate feedlots so that
drainage runs to a playa lake located on the property of the feedlot
owner. This practice has undoubtedly lessened the pollution problem
so far as surface water is concerned, but it has also undoubtedly re-
sulted in an increase in the potential for pollution of groundwater
in the High Plains area.
The water pollution problems associated with cattle feedlot
operations in the High Plains area are not the same as those found in
the Corn Belt of the Midwest. Much of the cattle feeding in the Corn
Belt is located on the individual farm site where it provides supple-
mentary income and converts a portion of the farmer's crop into a
higher priced product. The average number of cattle marketed per
feedlot in the Corn Belt is under 100 head annually, whereas individual
feedlots in Texas market an average of about 1700 per year. Over
13,000 head per feedlot are marketed annually in Arizona.
In addition to differences created by high volumes of waste and
density of deposition, the climatic factors of the High Plains as
related to the characteristics of feedlot wastes are considerably
different from those of the Midwest. The limited rainfall in the
area is concentrated in two short periods during the spring and fall
as previously noted. Short periods of high intensity rainfall result
in high rates of runoff in late spring and early fall. These periods
are followed by long dry periods of low air moisture and little pre-
cipitation. During this time the urine and feces accumulate on the
feedlot surface in a dehydrated form resulting in a waste high in
accumulated salts. Because of rapid dehydration the accumulated
waste exists in a relatively inert form that can be readily converted
almost to its original condition by the simple addition of moisture.
Project Objectives
The overall objective of this study was to plan and conduct
investigations which would determine the characteristics of beef
cattle feedlot wastes in a semi-arid climate.
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More specifically, the objectives were:
A. To determine the quantity and quality of runoff from South-
western beef cattle feedlots.
B. To develop recommendations and design criteria for South-
western beef cattle feedlot waste management control.
Cattle feeding facilities consisting of both dirt and concrete-
surfaced feedlots and controlled environment chambers located on the
Texas Tech University farm were used in the studies. The conven-
tional feedlots were operated in a manner conforming to normal
commercial operating practice of the area. Runoff was collected in
pits according to current recommendations of the Texas Water Quality
Board.
The cattle in the controlled environment facilities were fed an
all-concentrate ration, and the wastes produced by these cattle were
flushed out with water on a daily or every other day basis and col-
lected in a 55 gallon drum located adjacent to the facility. Addi-
tional studies were conducted using a feedlot in which cows were fed
a maintenance ration consisting primarily of silage.
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REVIEW OF PREVIOUS WORK
In the twenty-two major cattle feeding states, fed cattle
marketings have expanded from approximately 12 million head in 1969
to 17 million head in 1964, and to 23.7 million head in 1969. The
growth of this industry has been in feedlots with a capacity of 1,000
head or more. (Western Livestock Marketing Information Project, 1970).
The intensification in numbers of cattle per feedlot has been followed
by numerous situations which have been magnified to the point of
needing new concepts for optimum and efficient management. One of
these areas is the handling and disposal of cattle feedlot waste. The
volume of daily waste accumulation per animal has been observed to
range from as low as 2.3 pounds when feedlot cattle consumed an all-
concentrate finishing ration (Grub et al., 1969) to a reported 8.1
pounds for bovine wastes in general (Okey, Rickles and Taylor, 1969).
McCalla and Viets (1969) stated that 10,000 head of cattle on a feed-
lot produce 260 tons of solid waste and 100 tons of liquid waste daily.
This amounts to a total of 72 pounds per head per day.
The potential pollutional characteristics of animal waste and run-
off water from feedlots have been recorded by Henderson (1962),
TaiganWes (1963), Willrich (1966), and Loehr (1968b). Incidents of
groundwater pollution (Loehr and Agnew, 1967; Loehr, 1968a; Hart et al.,
1970) and fish-kills (Smith and Miner, 1964; U. S. Department of HEW,
1965; U. S. Department of the Interior, 1966; Kansas Forestry, Fish and
Game Commission, 1967) which have been directly attributed to runoff
from livestock feeding operations have been instances of concern. It
is documented (N.R.C., 1966) that the elimination of wastes as a dis-
charge material generally intrudes upon a natural resource or someone's
personal rights.
Characteristics of Cattle Feedlot Waste
Grub et al. (1969) summarized data from various sources which
indicated that the type of ration, size of cattle, concentration of
cattle per pen, slope and surface covering of the lot, depth of accumu-
lation, and moisture content of the waste were some of the major fac-
tors affecting the composition and quantity of cattle feedlot waste.
Gilbertson et al. (1970) found that animal density and surface slope
influenced the characteristics of runoff and solid waste from unpaved
beef feedlots. Several workers have reported data on the quality of
runoff from cattle feedlots, among those being Miner et al. (1966),
Miner, Lipper and Erickson (1967), Loehr (1969b), Grub et al. (1969),
Norton and Hansen (1969), Wells et al. (1969b), and Gilbertson et al.
(1970). These papers varied somewhat with respect to actual numerical
values .reported for many of the parameters, but consistently agreed
that runoff from cattle feedlots was highly concentrated and carried
a high pollution potential.
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Pollution of water usually refers primarily to surface water, but
pollution of groundwater from cattle feedlots seems to be a definite
possibility (Smith, 1965; Stewart et al., 1967; Engberg, 1967; McCalla
and Viets, 1969; Wells et al., 1969). The work of Gilbertson et al.
(1970) indicated movement of pollutants into the soil under unpaved
feedlots, but considerable nitrate movement in the buffer strips be-
tween test lots. Other information would support the concept that
contact surfaces are sealed by a film or slime layer which prevents
seepage of water from feedlot surfaces, ponds, playa lakes, and dikes
into the groundwater supplies (Lehman, Stewart and Mathers, 1970).
Handling and Disposal Methods
Feedlot waste can be partitioned into liquid and solid elements.
The liquid portion is generally observed as a component of the accumu-
lated waste on feedlot surfaces, as runoff during periods of rainfall,
or as the carrier in liquid handling systems. Solid waste can be
found on the feedlot surface, as a suspension in runoff water, as sedi-
ment in retention ponds, or as a suspension in liquid handling systems.
Loehr (1968b) and Jones (1969) have summarized the concepts, methods,
and problems associated with the handling and disposal of animal wastes.
Land Utilization. Application of feedlot waste to the land has
been an accepted and common method of disposal. A general pattern of
feedlot waste and runoff handling and disposal for Southwestern cattle
feedlots is described as follows. Solid waste is often stockpiled
within the cattle pen or in a central storage area near the feedlot.
The material might be spread out to dry prior to stockpiling. The
solid waste is then spread on fields as cultural practices and weather
conditions permit. The waste is turned under or worked into the soil
as soon as possible after spreading to reduce the chance of groundwater
pollution. Runoff water is trapped in retention ponds or dikes, then
pumped into a field irrigation system as a mixture with well water, or
into shallow lagoons or ponds for evaporation. Owens et al. (1969)
discussed the physical and economic relationships of these runoff and
disposal procedures. Wells et al. (1969b) have described the toxic
effects of application of undiluted feedlot runoff to selected crops.
Liquid handling systems for animal waste have evolved with the
development of confined livestock operations. Confined production of
fattening cattle has resulted in the need for critical evaluation of
this system. Okey, Rickles and Taylor (1969) compared the relative
economics of disposal of feedlot waste by selected wet and dry tech-
niques. Their findings indicated that wet systems would be more
expensive than those systems designed to handle solids. Liquid han-
dling of feedlot waste would require adequate holding facilities to
allow greater flexibility in the schedule for spreading (Loehr, 1968b).
Liquid waste systems are generally holding and handling methods, with
disposal of the liquid material by one or more of the methods discussed
later. Data for cattle feeding systems are limited, but the infor-
mation reported for other livestock production units would indicate
10
-------
that disposal of liqujd waste is being accomplished by spraying on
the land with an irrigation system, spreading by flood irrigation,
spreading on the land from bulk tank trailers equipped with a sprayer
system (Loehr, 1968b; Ward anri Jex. 1969; Casler, 1969; Walker and
Pos, 1969; Garold Parks, personal communication), or by application
of the liquid waste under the soil (Reed, 1969).
Detailed information is lacking concerning optimum and maximum
levels of soil application of solid or liquid feedlot waste, the
effects of long-term application upon the soil, necessary land area
per feedlot animal, economics of the method, effects of regional and
seasonal influences, acceptable social relationships, and critical
comparisons with other animal waste disposal systems. Use of this
method seems to be limited to the amount of nitrogen applied per hec-
tare of cultivated land. One report stated that approximately 72 kg
of nitrogen from feeder cattle was the maximum amount per ha (Jones,
1969). Another source (Gray, 1969) illustrated that application rates
of feedlot solid waste varied from as little as five tons per acre per
year to as much as 300 tons per acre per year. Webber and Lane (1969)
reported that two beef animals (weighing 181 to 500 kg) would excrete
64 kg of N in 365 days and would require 0.405 ha as the minimum land
area in continuous corn for the efficient use of added nitrogen from
manure, but only 0.202 ha as the minimum land area in continuous corn
for the maximum application of nitrogen from manure which would not
reduce corn yield or cause water pollution. Wells et al. (1969b) and
Gilbertson et al. (1970) have raised questions concerning possible
toxic levels of certain minerals. Many of the disposal systems to be
mentioned culminate with disposal of residue on the land.
Anaerobic Digestion. The biological degradation efficiency of
this process seems to be dependent upon the type of ration and animal
(Loehr, 1968b). Laboratory studies have shown that loading rates of
45 g to 180 g of total solids per cubic foot have been successful with
beef cattle wastes (Loehr and Agnew, 1967). Jeffrey, Blackman and
Ricketts (1963) and Hart (1963) have demonstrated that beef cattle
wastes can be treated by this method. Gases produced from this system
contain between 50 and 70 percent methane. Field units have generally
not been as successful as laboratory units and this difference has
been atributed to the more complete mixing and more closely controlled
temperatures of laboratory tests (Loehr, 1968b). In some instances,
low temperatures in cold climates have been responsible for failure
and incomplete digestion (U. S. Department of HEW, 1965; Berry, 1966).
This type of treatment of municipal sewage (anaerobic sludge digester)
is one of the most difficult systems to operate (Jones, 1969). The
effluent from this process would generally require further treatment
before release into the environment (Loehr, 1968b).
Anaerobic Lagoons. Loehr (1968b) presented an extensive discus-
sion on this system with reference to waste from animals of all species
and the comments to follow were summarized from his review. Little
11
-------
information has been reported for cattle wastes. The main functions
of anaerobic lagoons are to remove, destroy, and stabilize organic
matter, but not necessarily to purify water. This system is used
mainly for treatment of highly concentrated wastes. Gas and odor pro-
duction are evident near one of the systems. An anaerobic lagoon is
similar in function to a single-stage, unmixed, unheated digester.
Loading rates, pH, temperature, depth of the lagoon, and mixing must
be carefully controlled. In anaerobic lagoons, there is a relatively
solids-free liquid layer above a layer of settled solids. Taiganides
(1968) reported that most anaerobic systems studied and used to date
have yielded disappointing results.
Aerobic Lagoons. Animal wastes have a high oxygen demand,
requiring large surface areas and volumes. For example, a confinement
unit holding 1,000 head of beef cattle would require an oxidation pond
of at least 8 ha (Loehr, 1968b). If mechanical aeration were used,
less land area would be required than with the oxidation pond (Loehr,
19685; Jones, 1969).
Oxidation Ditch. The oxidation or Pasveer ditch has received new
attention with the advent of confined beef cattle feeding facilities.
Forsyth (1965) listed many modifications of the oxidation ditch: con-
tinuous, semicontinuous, batch, and use of side ditches as settling
tanks. Excessive foaming has been reported with animal wastes, but
odors were practically eliminated (Loehr, 1968b; Jones, 1969). Moore,
Larson and Allred (1969) have reported using this method for stabiliz-
ing beef cattle wastes in a cold climate.
Aerobic Composting. The reason for aerobic composting would seem
to be that solid waste from beef cattle feedlots could be stabilized
to a point at which the material would be odorless, insects would no
longer be attracted to the mass, bacteria of purification would no
longer be active, coliform bacteria would no longer be detected, and a
reduction of internal temperature would occur (Taiganides, 1968; Wells
et al., 1969a). After composting, virtually all (Loehr, 1968b) to 80
percent (Wells et al., 1969a) of the dry matter remains for further
disposal, presumably to the land. In addition, provisions would need
to be made for disposal of runoff water. Wiley (1964) reviewed the
operation of three animal waste composting plants, one of which was
windrow composting of the combined manure from 5,500 steers plus the
wastes from a meat packing operation. Wells et al. (1969a) reported
data obtained from studying the effects of feed, management, and cli-
mate upon the composting efficiency of beef cattle waste in open air
piles and in a drum-type digester. Both reports indicated successful
stabilization of wastes by composting with minimum costs involved.
Complete Treatment. Complete treatment of animal wastes would be
required if the final effluent were to be discharged into or adjacent
to surface water. Alternatives for the complete treatment of animal
waste were suggested by Okey, Rickles and Taylor (1969). The high
12
-------
degree of purity required by this means of disposal would be paralleled
by larger and more expensive facilities for treatment (Bernard, 1969).
Dehydration and/or Incineration. Aerobic and anaerobic systems
reduce the pollution characteristics of animal wastes but do little to
reduce the volume of material to be handled. Dehydration and/or in-
cineration is an approach that would dramatically reduce the quantity
of animal waste to be handled and the potential for pollution of water.
The available literature deals with the combustion of poultry wastes.
A discussion of this system was made by Ludington "(1963) for poultry
manure.
Nutrient Recycling. The feeding of animal waste to livestock
offers an interesting approach to waste management. This practice
would utilize waste as a feedstuff, with the concept of materials
reutilization being practiced. Anthony (1970) presented a paper sum-
marizing the use of animal waste as a feed.
European Methods. Extensive reviews of handling and disposal
practices in Europe were published by Allred (1966), Morris (1967), and
Meek, Merrill and Pierce (1969). The systems reportedly used in Europe
were generally based on small numbers of livestock per unit of land and
employed a modification of an aerobic system. Therefore, with the in-
creased concentration of beef cattle in feedlots in the United States,
the value of European experiences may be limited.
Miscellaneous Methods. Loehr (1968b) reviewed miscellaneous
handling practices for animal wastes, such as the addition of chlorine,
lime, or chemical coagulants, or the use of trickling filters. Appli-
cation of these methods to the disposal of cattle feedlot waste would
appear to be of doubtful significance.
Implications for the Future. Biniek (1969) presented a thought-
provoking paper on the question of livestock production versus envi-
ronmental quality. He pointed out that time may be limited to achieve
equitable solutions to environmental pollution and that we must be
adaptive, flexible, and innovative to master the challenge. Loehr
(1968b) outlined some of the pollution hazards associated with live-
stock wastes which must have a solution. Clayton (1969) discussed
animal waste in general and feedlot waste in particular, from the
legislative point of view. He posed significant environmental prob-
lems associated with waste from this industry.
Research Needs. Scalf and Witherow (1969) summarized research
needs for feedlot waste management with an emphasis on the need for
application of present technology and knowledge as a rapid, useful,
and essential step toward future solutions of water quality problems.
They proposed that a suitable method for the management of cattle
feedlot runoff might be a combination of pretreatment in an anaerobic
lagoon, treatment in an oxidation ditch or aerated lagoon, and final
13
-------
disposal on the land. Complete treatment in the aerobic system was
proposed to be given attention in order that stream disposal might be
applicable for the effluent.
A review of current research projects and areas for future
research of beef cattle wastes in the Plains states was prepared by the
Great Plains Agricultural Council (1969). This report recommended
that research efforts be intensified in five areas: air pollution —
from odors, ammonia, dust, and pathogens; land disposal — influence
of extended application of manure upon soil integrity; pollution under
feedyards ~ investigate deep percolation of nitrates, phosphates, and
microorganisms; systems analysis ~ production methods related to dis-
posal techniques, considering parameters of climate, construction,
feed, and possible zoning restrictions or relocation; complete economic
evaluation of current alternatives for waste disposal; and socio-legal
implications -- a well-defined approach to their solution.
Evans (1969) proposed plans for expansion or initiation of feed-
lot waste research in the areas of: microbial, chemical, and organic
pollution of the atmosphere, soils, and surface and underground water
supplies; development of systems for pollution control of runoff water
and subsequent treatment of the contained runoff by aeration, activated
microflora, or by precipitation of colloids; and field investigations
of the effects of heavy manure applications on cropped and uncropped
soils over a period of years. A later report indicated that some of
these studies were being implemented (Evans, 1970).
King (1969) itemized several avenues that warranted research
attention. Some of these not previously mentioned are: the develop-
ment of joint treatment and disposal facilities by several producers
or sufficient treatment to enable the effluent to be handled by muni-
cipal treatment plants; seek potential uses for animal wastes; land
use planning; and development of more detailed information on the
relationship of wastes to agricultural production.
Loehr (1969a) tabulated most of the research areas mentioned, but
with emphasis upon giving attention to the definition of problem areas,
or types of research that were most likely to benefit from accelerated
effort, and the investigation of trade-offs between technical improve-
ments versus their effect upon waste management activities.
Webber and Lane (1969) indicated that before significant progress
will be made in the disposal of animal waste, the nitrogen cycle must
be quantitatively characterized.
Gilbertson (1969) and Hart et al. (1970) postulated from their
findings that economics must be involved with each investigation con-
cerned with pollution control from animal agriculture.
14
-------
New concepts for*the management of feedlot waste are receiving
attention. A two-stage anaerobic digester is being studied as a
refined approach to the treatment of feedlot waste (Wells et al.,
1969b). A system of complete flushing of the concrete surface of a
10,000 head commercial feedlot is being used with disposal of the
effluent in irrigation water for Midland Bermudagrass pasture (Dwight
Pittman, personal communication). Covering feedlots with a roof would
eliminate runoff water, leaving only the solid waste for management.
Use of feedlot waste as a resource material offers a challenging ap-
proach, such as construction material, phosphoric acid treatment for
specialized fertilizer (Lasalle and Launder, 1969), or as a substrate
for single-cell protein production for man and animals (Thayer and
Yang, personal communication). Biodegradation of manure by housefly
larvae with subsequent feeding of the insects as a protein source to
livestock has been investigated with poultry (Miller and Shaw, 1969;
Calvert, Morgan and Martin, 1970).
15
-------
STUDIES WITH CONCRETE-SURFACED FEEDLOTS
Four concrete-surfaced feedlots, each measuring 30 ft by 36 ft
and sloped at 7-1/2 percent in a southeasterly direction along the long
dimension were used in conducting the studies. The concrete surface
had a rough stiff-brush finish.
The four concrete lots were divided into two*drainage systems with
a concrete curbing separating the systems. Total water runoff from
each pair of lots was collected in unlined collection pits immediately
adjacent to the concrete surfacing. Instrumentation was installed to
measure pit volume, to allow for sampling during periods of runoff,
and to measure total precipitation, Figure 1.
Animal Feeding Studies
Three feeding trials were run in order to provide data required by
the project. The feeding trials lasted for 173 days, 136 days, and
121 days, respectively. Approximately 40 days elapsed between the end
of one feeding trial and the beginning of the next in order to provide
time for cleaning the lots, analyzing all data collected, and purchas-
ing and obtaining delivery of a new group of feeder cattle.
While a study of the performance of cattle under various feedlot
management systems was not a part of this project in the strictest
interpretation of the contract, its omission would have tended to have
made any results obtained of questionable value. Throughout the pro-
ject, emphasis was directed toward establishing the characteristics of
wastes and developing economically feasible and workable systems for
waste management, control and treatment of runoff, and solid waste
removal. The data are therefore included in order to put the report
in proper perspective.
Experiment I consisted of feeding 47 steers for 173 days. Mean
initial weight was 525 pounds per steer. The 47 steers were approxi-
mately equally divided among four lots. The steers in two lots were
fed an al1-concentrate ration, and those in the other two were fed a
12 percent roughage ration. Ration compositions used are shown in
Table 1, and the mean performance of the steers is shown in Table 2.
Experiment II utilized 80 heifers in a feeding trial of 136 days
duration. Mean initial weight of the heifers was 475 pounds. Compo-
sition of the ration fed is shown in Table 1. The purposes of this
experiment were to study the effects of cattle density, lot cleanli-
ness, manure moisture content, and roof shelter on the performance of
cattle and on the quantity and characteristics of wastes produced.
17
-------
ROOF
DIKE
COLLECTION
PONDS
/
\
ALLEY
C
o ,
o
FEED
BUNK
c
WATERERS
C
J
7-1/2%
o
en
o
CO
10' 36'
CALICHE LOTS
12'
FIGURE 1. LAYOUT OF CONCRETE-SURFACED FEEDLOTS USED ON PROJECT.
18
-------
TABLE 1. RATION COMPOSITION (percent, air-dry basis)
Experiment I Experiments II & III
Ingredients AT
1 -concen-
trate
12% Rough-
age
10% Roughage
As Fed
Sorghum grain, dry rolled
Cottonseed meal (41%)
Cottonseed hulls
Alfalfa hay, chopped
Beef tallow
Premix T-272
Calcium carbonate
Chemical
Dry matter >
Crude protein
Calcium
Phosphorus
Premix T-272 Composition
Cottonseed meal
Calcium carbonate
Salt
Vitamin A (325,000 lU/g)
Stilbestrol (2 g/lb)
Chlortetracycline (50 g/lb)
90.81
6.00
0.00
0.00
0.00
3.00
0.19
100.00
89.64
11.9
0.80
0.28
74.75
7.25 .
6.00
6.00
3.00
2.75
0.25
100.00
90.03
11.9
0.87
0.32
Amount (Ib)
974.17
600.00
400.00
1.13
20.00
4.70
2,000.00
76.00
7.25
5.00
5.00
3.00
3.75
0.00
100.00
89.87
11.9
0.41
0.37
TABLE 2. MEAN FEEDLOT PERFORMANCE OF STEERS IN EXPERIMENT I (POUNDS:
173 DAYS)a
Treatments
Parameter
Al 1 -concen-
trate
12% Rough-
age
% Difference
Number of steers
Daily gain
Feed consumption
Efficiency (feed/gain)
23
2.47
17.9
7.00
24
2.61
20.0
7.67
5.4
10.5
8.7
No statistical differences among the parameters (P < .05).
19
-------
Before Experiment II was initiated, a sheetiron rocf was placed
over Lot No. 1, Figure 1. Cattle were then placed in Lot No. 1 at a
density of 42 square feet per animal, in Lot No. 4 with a density of
41 square feet per animal, and in Lots 2 and 3 at a density of 84
square feet per animal. Lot No. 2 was kept continuously wet by
periodic sprinkling, and Lot No. 3 was cleaned on a weekly basis. Mean
performance of animals used in this experiment is given in Table 3.
TABLE 3. MEAN FEEDLOT PERFORMANCE OF HEIFERS IN EXPERIMENT II (POUNDS:
136 DAYS)*
Parameter Treatments % Difference
Number of animals
Daily gain
Feed consumption
Efficiency (feed/gain)
Number of animals
Daily gain
Feed consumption
Efficiency (feed/gain)
Number of animals
Daily gain
Feed consumption
Efficiency (feed/gain)
Covered
26
2.62
18.9
7.21
Continuously
Clean
14
2.80
20.2
7.21
Animal Density
il
53
2.63
19.1
7.26
Open
27
2.63
19.3
7.35
Continuously
Wet
13
2.63
18.7
7-11
(square feet/animal)
84
27
2.72
19.6
7.17
2.1
1.9
6.1
7.4
1.4
3.3
2.1
1.2
No statistical differences among the parameters (P < .05).
Experiment III investigated the effects of pen covering, density,
and pen slope on animal performance. For this experiment, pens 1 and
4 (Figure 1) were each divided into two fifteen foot wide pens. The
eastern most side of each pen was then rebuilt to provide a fifteen
percent slope and a finish similar to that on existing lots.
Eighteen steers were put in each side of Lots 1 and 4, and Lots
2 and 3 each contained nine steers. The feeding trial was continued
for 121 days. Mean performance of the steers under different slopes,
densities, and shading conditions is shown in Table 4.
20
-------
TABLE 4. MEAN FEEDLOT, PERFORMANCE OF STEERS IN EXPERIMENT III (POUNDS:
121 DAYS)
Parameter
Treatments
% Difference
Surface Slope6
Number of animals
Daily gain
Feed consumption
Efficiency (feed/gain)
Number of animals
Daily gain
Feed consumption
Efficiency (feed/gain)
7.5%
36
2.64
20.94
7.93
Shading3
Covered
36
2.57
20.79
8.09
Animal Density
15%
36
2.49-
20.50
8.23
Open
36
2.56
20.65
8.07
5.7
2.1
3.6
(square feet/animal)
30 120
Number of animals
Daily gainb
Feed consumption .
Efficiency (feed/gain)
aNo statistical treatment
72
2.57
20.72
8.08
differences among
18
3.03
21.39
7.08
parameters
15.2
3.1
12.4
(P < .05).
"Statistically different (P < .005).
Statistical difference at P < .10.
Results of Feeding Trials
Carcass measurements were taken on the animals in Experiments I
and II. In both studies, no statistical differences (P < .05) were
detected between treatments for the parameters which were monitored.
The increase of animal density to 40 square feet and 30 square
feet per animal resulted in lowered daily gain and efficiency of feed
utilization (P < .005). Feed consumption decreased with increasing
density.
Solid Waste Accumulation on the feedlot surface was affected most
by ration composition, Table 5. Feeding an al1-concentrate finishing
ration to feedlot cattle resulted in 2.3 pounds of dry waste accumu-
lation per head daily. A 12 percent roughage finishing ration resulted
in 5.0 pounds, and a 10 percent roughage ration resulted in 4.4 pounds
of dry waste per animal per day. Both covering the feedlot and con-
tinuously wetting the open pen surface reduced dry waste accumulations.
21
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TABLE 5. SOLID WASTE ACCUMULATION DURING THE FEEDING PERIODS
Experiment I Experiment II, 10% Roughage
Al1-concen-12% Rough-Continuously
Item trate flaggy Covered Open Wet
Number of animals 23 24 26 27 13
Feed dry matter, Ib 60,768 77,110 60,430 64,229 30,723
Waste accumulation
Total pounds 19,110 44,930 29,850 33,610 19,950
Dry matter % 47.0 46.9 48.2 49.0 44.0
Dry matter, Ib 8,982 21,072 14,388 16,469 8,778
Feed:waste ratio,
D.M. basis
Animal days
Square feet/animal
Live weight, Ib
Daily dry matter
Per head, Ib
Per 100 Ib live
weight, Ib
waste
6.S:1
3,950
95
745
3.7:1
4,237
88
775
4.2:1
3,600
42
678
3.9:1
3,672
41
679
3
1
.5:1
,815
84
649
accumulation
2.
0.
3
31
5.
0.
0
65
4
0
.0
.59
4.
0.
5
66
4.
0.
8
74
Per head per square
ft, Ib
0.
024
0.
057
0
.10
0.
10
0.
057
Of the other treatment variables studied in separate feeding
experiments involving 7-1/2 percent slope versus 15 percent slope in
concrete pens, open versus covered pens, dirt versus concrete pen sur-
faces, and continuously clean versus continuously wet concrete surfaces,
none of the comparisons resulted in statistically significant differences
in animal performance, although tendencies might be observed as shown by
the data in Tables 2, 3, and 4.
Runoff From Concrete-Surfaced Feedlots
The precipitation regime during the experimental period in Lubbock,
Texas was typical of the area. Very little precipitation occurred dur-
ing the winter months, approximately 8 inches occurred during the spring
of 1969 and very little occurred during the summer. A near record 18
inches of rain fell during the fall of 1969. Very little rain fell
again during the winter of 1969-1970, and the total rainfall for all of
1970 was only 9 inches. Almost half of this rain occurred during the
tornado of May 11, 1970.
A manual type rain gage was located in the vicinity of the feedlots
to determine the total precipitation for each event. No attempt was
made to establish the rate of precipitation. The total quantity of run-
off from the lots was measured by noting the change in elevation of the
liquid level in the pits before and after the period of precipitation
22
-------
and calculating the total volumetric change as a function of the dif-
ference in liquid level.
Samples of accumulated runoff were taken from the collection ponds
on a weekly basis for analysis. In addition, a number of grab samples
of runoff were taken at 30-minute intervals during runoff-producing
rainfalls. Later, an automatic sampler was installed to collect sam-
ples at 15-minute intervals from one of the lots, but very little
runoff occurred after it was installed.
Rainfall-runoff relationships were found to be influenced by type
of ration fed. The fraction of incident precipitation running off
feedlots on which all-concentrate rations were fed was greater than the
fraction running off lots on which 12 percent roughage ration were fed.
Typical data obtained from lots on which all-concentrate rations were
fed are given in Table 6.
TABLE 6. TOTAL PRECIPITATION AND RUNOFF FROM CONCRETE-SURFACED
FEEDLOTS FROM AUGUST 20, 1969 THROUGH OCTOBER 21, 1969.
ALL-CONCENTRATE RATION WAS FED DURING THIS PERIOD
Date
Rainfall
In.
Retention
In.
Runoff
In.
Runoff
Percent
8-20-69
8-24-69
8-25-69
8-27-69
8-28-69
9-08-69
9-09-69
9-10-69
9-13-69
9-17-69
9-21-69
9-22-69
10-6-69
10-19-69
10-21-69
10-22-69
10-23-69
0.09
1.40
2.29
0.40
0.29
0.20
1.01
0.23
1.38
2.72
1.08
0.83
0.43
0.04
2.86
1.64
1.45
0.09
0.727
0.58
0.185
0.246
0.20
0.398
0.23
0.806
0.572
0.302
0.488
0.427
0.04
0.96
0.754
0.904
0
0.673
1.710
0.215
0.044
0.00
0.612
0.00
0.573
2.15
0.778
0.342
0.003
0.00
1.90
0.386
0.546
0
48.00
74.60
53.80
15.20
0
60.60
0
41.50
79.00
72.00
41.30
0.67
0
66.50
54.00
37.70
Total
18.34
8.308
10.032
56.50
Analysis of all data obtained from these lots yielded the rela-
tionship shown in Figure 2.
Typical data derived from identical lots on which a 12 percent
roughage ration was. fed are presented in Table 7.
23
-------
ro
2.0r-
to
LU
* 1.0
la.
u_
O
o.o
o.o
I
FEEDLOT SLOPE = 7-1/2 %
I
1.0 2.0
PRECIPITATION, P, INCHES
3.0
FIGURE 2. PRECIPITATION-RUNOFF RELATIONSHIP FOR CONCRETE-SURFACED FEEDLOTS ON WHICH ALL-
CONCENTRATE RATIONS WERE FED.
-------
The feed pens from which the data presented In Tables 6 and 7
were derived were identical; each contained the same number of cattle
of the same size, each was thoroughly cleaned before the experiment
started, and each was stocked with cattle on the same day. The only
known variable In the experiment was the ration. One group of cattle
was fed an all-concentrate ration and the other was fed a ration con-
taining 12 percent roughage.
TABLE 7- TOTAL PRECIPITATION AND RUNOFF FROM CONCRETE-SURFACED
FEEDLOTS FROM AUGUST 20, 1969 THROUGH OCTOBER 21, 1969.
TWELVE PERCENT ROUGHAGE RATION WAS FED DURING THIS PERIOD
Date
Rainfall
In.
Retention
In.
Runoff
In.
Runoff
Percent
8-20-69
8-24-69
8-25-69
8-27-69
8-28-69
9-08-69
9-09-69
9-10-69
9-13-69
9-17-69
9-21-69
9-22-69
10-6-69
10-19-69
10-21-69
10-22-69
10-23-69
0.09
1.40
2.29
0.40
0.29
0.20
1.01
0.23
1.38
2.72
1.08
0.83
0.43
0.04
2.86
1.64
1.45
0.09
0.835
/; 0.975
*% 0.40
13 0.29
0.20
0.538
0.23
0.821
0.394
0.625
0,582
0.430
0.040
1.400
1.125
1.368
0.00
0.565
1.315
0.00
0.00
0.00
0.472
0.00
0.559
2.32
0.455
0.248
0.00
0.00
1.460
0.515
0.082
0
40.03
57.50
0
0
0
46.80
0
40.50
85.40
42.00
30.00
0
0
51.00
31.40
0.57
Total
18.34
10.448
7.891
43.00
The analysis of all runoff data collected from the lot on which
the roughage-concentrate ration was fed yielded the relationship shown
in Figure 3.
As noted previously, the quantity of solid waste accumulating in
the lot on which a roughage-concentrate ration was fed was more than
twice as great as the quantity accumulating in the other lot. Dif-
ferences fn retention rates were attributed to the depth of manure
available for storing water, to a difference in water holding capacity
of the wastes resulting from the two types of feed materials, or to a
combination of these and other factors.
25
-------
2.0
CO
LU
CJ
1.0
ro
o
z
0.0
0.0
FEEDLOT SLOPE = 7-1/2 %
I
1.0 2.0
PRECIPITATION, P, INCHES
3.0
FIGURE 3. PRECIPITATION-RUNOFF RELATIONSHIP FOR CONCRETE-SURFACED FEEDLOTS ON WHICH 12 PERCENT
ROUGHAGE RATIONS WERE FED.
-------
Quality and Quantity Relationships
Grab samples of runoff were collected from each pair of lots at
approximately 30-minute intervals during each of several runoff-pro-
ducing precipitation events. Analyses of a typical set of runoff
samples collected from concrete surfaced lots during a storm of August
24, 1969, are presented in Table 8.
TABLE 8. CONCENTRATIONS OF POLLUTANTS IN RUNOFF FROM CONCRETE LOT
RESULTING FROM PRECIPITATION STARTING AT 11:00 P.M. ON
AUGUST 24, 1969
Time of
Collection
PH
BOD
(mg/1 )
COD
(mg/1 )
N03
(mg/1 )
NH3-N
(mg/1 )
ORG-N
(mg/1 )
ALKY
(mg/1 )
11:35
11:58
12:35
2:25
p.m.
p.m.
a.m.
a.m.
6
6
6
6
.60
.80
.65
.80
16,
6,
7,
9,
800
120
40Q
950
48,
20,
22,
23,
000
451
032
316
625
975
1000
900
525
526
485
543
532
315
36
285
2595
1955
2000
1865
These data indicate that the initial runoff contains a higher
concentration of pollutants, particularly BOD and COD, than does sub-
sequent runoff. This difference is not considered to be significant
since the quality of runoff remains very poor, regardless of the dura-
tion of the runoff. This observation was duplicated repeatedly in
samples taken from feedlots while runoff was occurring and experiments
utilizing a tilting table to stimulate a feedlot in the laboratory.
The effects of rations on runoff quality are indicated by data
presented in tables 9 and 10. Values shown in these tables are aver-
ages of several grab samples collected from each lot while runoff was
occurring.
TABLE 9. CONCENTRATIONS OF POLLUTANTS IN RUNOFF FROM CONCRETE-
SURFACED LOT ON WHICH CATTLE WERE FED ALL- CONCENTRATE
Date
PH
BOD COD N03
(mq/1) (mg/1) (mg/1)
NH3-N
(mg/1 )
ORG-N
(mg/1 )
RATION
ALKY
(mg/1 )
8-24-69
8-26-69
9-9-69
9-22-69
10-21-69
10-26-69
11-1-69
6.30
5.90
5.60
6.90
6.35
6.70
7.30
7,355
8,900
10,400
4,424
8,300
12,000
2,395
28,929
38,400
30,230
10,080
20,742
23,000
4,971
1270
280
228
36
386
350
0
340
395
518
460
304
140
120
610
302
797
650
293
235
250
1030
1584
1174
1380
116
236
116
27
-------
TABLE 10. CONCENTRATIONS OF POLLUTANTS IN RUNOFF FROM CONCRETE-
SURFACED LOT ON WHICH CATTLE WERE FED ROUGHAGE-CONCENTRATE
RATION
Date
8-24-69
8-26-69
9-9-69
9-22-69
10-21-69
10-26-69
11-1-69
PH
6.70
6.15
6.62
6.75
6.67
6.85
7.00
BOD
(mg/1 )
10,067
8,500
12,750
5,270
10,250
3,300
5,566
COD
(mg/1)
28,450
32,800
32,172
11,514
20,868
8,400
16,252
N03
(mg/15
875
320
97
22
140
70
0
NHs-N
(mg/1 )
519
515
774
100
406
33
115
ORG-N
(mg/1)
300
384
301
132
114
35
115
ALKY
(mg/1)
2104
2056
2402
1632
170
86
336
The concentrations of pollutants in runoff are relatively indepen-
dent of the type of ration fed as shown in the above two tables. It
is worth noting, however, that if the concentrations were identical,
the total quantity of pollutants contained in runoff from lots on
which al1-concentrate rations were fed would exceed by about 25 percent
the quantity contained in runoff from lots on which roughage-concen-
trate rations were fed because of the increased volume of runoff.
Effect of Slope on Waste Movement
The eastern most halves of Lots 1 and 4 (Figure 1) were modified
to a slope of 15 percent, double the 7-1/2 percent slope of the origi-
nal lots. At this time, Lot 1 had been equipped with a sheet iron
roof. The other steep sloped lot was uncovered.
Cattle were placed in all four lots at equal population densities
and fed for 150 days. No difference in animal performance was noted
as a result of slope during the feeding period, Table 4. The increased
slope affected the movement and final deposition of the waste on the
feedlot surface. On both the covered and uncovered treatments the
waste movement on the 15 percent slope toward the lower-edge of the
slope resulted in less than one inch of waste accumulation on the
upper two-thirds of the lot surface. This was in marked contrast to
the shallower slope where waste movement by action of the animals was
less complete and several inches accumulated on the upper surface.
The fencing along the lower edge of the lot restricted the move-
ment of the waste from the lot. As a result a considerable depth of
manure accumulated on the fence line and prevented further movement of
the waste material. Modifications in the shape and slope of the sur-
face are indicated to remove this blockage. A slotted floor along the
lower edge or a fence design with sufficient clearance between the lot
surface and the lower edge of the fence might facilitate the movement
of the waste out of the animal area.
28
-------
STUDIES WITH DIRT-SURFACED FEEDLOTS
Two dirt-surfaced feedlots, each measuring 80 by 100 feet and
sloped at 2-1/2 percent in a northwesterly direction along the long
dimension were used in conducting the study. The lots were surfaced
with caliche obtained locally and were graded to a uniform slope at
the beginning of the experiment.
«
Each lot drained into a separate collection pit immediately ad-
jacent to the lower end of the lot, Figure 4. Instrumentation was
installed to measure pit volume, to allow for sampling during periods
of runoff, and to measure total precipitation.
Animal Feeding Studies
One feeding trial lasting 173 days was conducted on dirt-surfaced
lots to compare animal performance on concrete and dirt-surfaced lots.
However, the dirt-surfaced lots shown in Figure 4 contained cattle
throughout the period of the project and samples of runoff were rou-
tinely collected from these lots along with the collections from the
concrete lots.
The al1-concentrate and 12 percent roughage rations shown in
Table 1 were fed to 28 steers each in Lots 1 and 2, Figure 4 respec-
tively.
The mean feedlot performance of steers on the dirt lots did not
differ significantly from the performance of the steers on the con-
crete feedlot, Table 11.
It should be noted, however, that the feed/gain efficiency ap-
peared to be somewhat better for steers on dirt lots than for those
on concrete lots.
TABLE 11. MEAN FEEDLOT PERFORMANCE OF STEERS IN EXPERIMENT I (POUNDS:
173 DAYS)a
Treatments % Difference
Dirt Concrete
Number of steers
Daily gain
Feed consumption
Efficiency (feed/gain)
55
2.53
17.6
6.93
47
2.55
19.7
7.54
10.7
8.1
No statistical differences among the parameters (P < .05).
Because of the mixing of manure with the top surface of soil in a
dirt-surfaced feedlot, it was felt that any attempt to measure the
29
-------
CONCRETE
LOTS
o
00
o
oo
CALICHE
WATERERS
d
O
FEED BUNK
2-1/2 %
DIKE
12'
TOO'
ALLEY
-H
FIGURE 4. LAYOUT OF DIRT-SURFACED FEEDLOTS USED ON PROJECT.
30
-------
quantity of solid waste accumulating on the dirt feedlot floor during
one feeding trial would be futile. Therefore, no attempt was made to
measure the total quantity of solid waste that accumulated on this
surface. It is reasonable to assume, however, that on a long term
basis, the quantity to be removed would be very nearly the same as
the quantity to be removed from a concrete-surfaced lot.
Runoff From Dirt-Surfaced Feedlots
*
The method previously described for measuring runoff from con-
crete-surfaced feedlots was also used in determining the quantity of
runoff from dirt-surfaced lots. Dirt-surfaced lots retained a higher
fraction of incident rainfall than concrete-surfaced lots, and this
phenomenon appeared to be relatively independent of the depth of manure
contained on the lots.
Rainfall and runoff occurring during the same period in the fall
of 1969 for which runoff data related to concrete-surfaced lots were
presented in Tables 9 and 10 are shown in Tables 12 and 13.
TABLE 12. TOTAL PRECIPITATION AND RUNOFF FROM DIRT-SURFACED FEEDLOT
FROM AUGUST 20, 1969 THROUGH OCTOBER 21, 1969. ALL-CONCEN-
TRATE RATION WAS FED DURING THIS PERIOD
Date
Rainfall
In.
Retention
In.
Runoff
In.
Runoff
Percent
8-20-69
8-24-69
8-25-69
8-27-69
8-28-69
9-08-69
9-09-69
9-10-69
9-13-69
9-17-69
9-21-69
9-22-69
10-6-69
10-19-69
10-21-69
0.09
1.40
2.29
0.40
0.29
0.20
1.01
0.23
1.38
2.72
1.08
0.83
0.43
0.04
2.86
0.09
0.719
1.87
0.398
0.268
0.20
0.421
0.23
0.93
2.08
0.778
0.318
0.187
0.04
1.975
0.0
0.681
0.42
0.002
0.022
0.00
0.589
0.00
0.45
0.64
0.248
0.512
0.243
0.00
0.885
0
48.7
18.3
0.5
7.58
0
58.4
0
32.6
23.5
27.6
61.7
56.5
0
31.0
Total 18.34 13.598 4.742 25.8
Since the type of ration fed made no significant difference in the
rainfall-runoff relationship for dirt-surfaced lots, all data obtained
from these lots were combined to derive the relationship shown in Figure
o.
31
-------
TABLE 13. TOTAL PRECIPITATION AND RUNOFF FROM DIRT-SURFACED FEEDLOT
FROM AUGUST 20, 1969 THROUGH OCTOBER 21, 1969. TWELVE
PERCENT ROUGHAGE RATION WAS FED DURING THIS PERIOD
Date
Rainfall
In.
Retention
In.
Runoff
In.
Runoff
Percent
8-20-69
8-24-69
8-25-69
8-27-69
8-28-69
9-08-69
9-09-69
9-10-69
9-13-69
9-17-69
9-21-69
9-22-69
10-6-69
10-19-69
10-21-69
Total
0.09
1.40
2.29
0.40
0.29
0.20
1.01
0.23
1.38
2.72
1.08
0.83
0.43
0.04
2.86
18.34
0.09
0.839
1.87
0.398
0.269
0.20
0.476
0.23
1.12
2.11
0.514
0.365
0.43
0.04
2.064
14.102
0.0
0.561
0.423
0.002
0.021
0.00
0.534
0.00
0.26
0.61
0.566
0.465
0.00
0.00
0.796
4.238
0
40.00
18.50
4.50
7.25
0
50.28
0
18.80
22.40
52.40
56.00
0
0
27.80
23.10
Additional comparative data obtained in the spring of 1969 are
presented in Table 14.
TABLE 14. TOTAL PRECIPITATION AND RUNOFF FROM CONCRETE AND DIRT-
SURFACED FEEDLOTS FOR THE PERIOD APRIL 11, 1969 THROUGH
JUNE 13, 1969
Date
Total
Rainfall
In.
Concrete
Lots
7-1/2 Percent Slope
Retained
In.
Runoff
In.
Dirt Lots
2-1/2 Percent
Slope
Retained Runoff
In.
In.
4-11-69
4-12-69
5-2-4-69
5-5-69
5-6-69
5-28-69
6-13-69
0.99
0.62
1.50
1.59
0.45
2.14
1.87
0.29
0.39
0.37
0.45
0.33
0.38
0.41
0.70
0.23
1.13
1.14
0.12
1.76
1.46
0.87
0.55
1.15
1.04
0.45
2.08
1.72
0.12
0.07
0.35
0.55
0
0.06
0.15
The capacity of the dirt lots to retain rainfall was much more
variable than that of the concrete lots. The dirt feedlots retained
approximately three times as much rainfall during the spring as did
32
-------
CO
CO
2.0
in
UJ
u
1.0
0.0
0.0
FEEDLOT SLOPE = 2-1/2 %
\
1.0 2.0
PRECIPITATION, P, INCHES
3.0
FIGURE 5. PRECIPITATION-RUNOFF RELATIONSHIP FOR DIRT-SURFACED FEEDLOTS.
-------
the concrete feedlot. However, this difference was considerably less
during the fall when both the waste and the soil contained high mois-
ture concentrations due to the near-record rains recorded for this
period.
Quality and Quantity Relationships
Grab samples of runoff were collected from each pen at approxi-
mately 30-minute intervals during several rainstorms. These samples
were taken both during the 173 day feeding trial referred to earlier,
and subsequently when the cattle in both pens were being fed 10 percent
roughage rations. Typical results of analyses of a set of grab samples
are shown in Table 15. It will be noted that the concentrations of
pollutants shown in Table 15 are much less than the concentrations
shown in corresponding Table 8.
TABLE 15. CONCENTRATIONS OF POLLUTANTS IN RUNOFF FROM DIRT LOT
RESULTING FROM PRECIPITATION STARTING AT 11:00 P.M. ON
AUGUST 24, 1969
Time of
Collection
PH
BOD COD N03
(mg/1) (mg/1) (mg/D
NH3-N
(mg/1)
ORG-N ALKY
(mg/1) (mg/1)
11:35
11:58
12:35
2:25
p.m.
p.m.
a.m.
a.m.
7
7
7
7
.80
.50
.60
.80
1
2
1
1
,630
,500
,275
,630
5
9
6
11
,450
,781
,240
,650
16
128
132
136
51
98
100
67
27
297
434
44
1002
1092
1238
1620
Tables 16 and 17 show the average concentrations of pollutants in
grab samples taken at 30-minute intervals from the dirt-surfaced lots
in the fall of 1969.
TABLE 16. AVERAGE CONCENTRATIONS OF POLLUTANTS IN RUNOFF FROM
ON WHICH CATTLE WERE FED ALL-CONCENTRATE RATION
Date
PH
BOD COD N03
(mg/1) (mg/1) (mg/1)
NH3-N
(mg/D
ORG-N
(rag/1)
DIRT LOT
ALKY
(mg/T)
8-24-69
8-26-69
9-9-69
9-22-69
10-24-69
11-1-69
7.95
7-15
7.62
7.30
7.35
7.10
1,400
1,350
1,145
1,580
1,390
3,210
5,160
7,212
6,220
4,817
4,042
9,942
163
96
6
62
24
0
48
48
83
75
50
30
118
33
25
20
22
17
955
1602
864
746
70
360
34
-------
TABLE 17. AVERAGE CONCENTRATIONS OF
POLLUTANTS IN RUNOFF FROM DIRT LOT
ON WHICH CATTLE WERE FED ROUGHAGE-CONCENTRATE RATION
Date
PH
BOD
(mg/1)
COD
(mg/1 )
NOo
(mg7l )
NH3-N
(mg/1)
ORG-N
(mg/1)
ALKY
(mg/1)
8-24-69
8-26-69
9-9-69
9-22-69
10-21-69
10-26-69
11-1-69
7.68
7.40
7.70
7.63
7.50
7.45
7.70
1,758
1,010
1,340
1,400
1,620
1,100
2,200
8,280
2,964
6,316
28,000
4,400
8,000
8,795
103
24
3
3
28
0
0
79
77
75
71
85
2
3
200
25
50
40
67
6
117
1238
928
856
1400
99
183
436
The concentrations of organic pollutants in runoff from dirt-sur-
faced feedlots were only about 30 to 40 percent of the corresponding
concentrations in runoff from concrete-surfaced lots. Also, on a unit
area basis, all precipitation that occurred during the project resulted
in about twice as much runoff from concrete-surfaced feedlots as from
dirt-surfaced feedlots. On a unit area basis, the total quantity of
organic pollutants contained in runoff from dirt-surfaced lots was
therefore only about one-sixth as great as the quantity contained in
concrete-feedlot runoff.
Interpretation of Results
The above discussion appears to indicate that dirt-surfaced feed-
lots have a clear advantage over concrete-surfaced lots from the stand-
point of prevention of water pollution. This is not necessarily true.
Stocking rates normally used on concrete-surfaced feedlots are about
two and one-half or three times as great as the rates used on dirt-sur-
faced lots. Hence, the quantity of runoff per animal on concrete-
surfaced lots can be expected to be about two-thirds as great as the
quantity of runoff per animal on dirt-surfaced lots. Also, both the
concentrations of pollutants in runoff and the erratic nature of the
occurrence of runoff from Southwestern cattle feedlots mitigate against
any type of conventional treatment and subsequent release to surface
waters. Either evaporation of liquids or land disposal of liquid
wastes are therefore the only alternatives presently available. For
either of these systems, the concentrations of pollutants in the water
are relatively unimportant.
Because of the lesser quantity of runoff generated per head of
cattle on concrete-surfaced lots, it appears that dirt-surfaced feed-
lots may not be the optimum environment on which to feed cattle for
slaughter.
35
-------
STUDIES WITH MODIFIED ENVIRONMENT FEEDING FACILITIES
Controlled environment chambers were constructed to determine
the effect of climatic conditions on the rate of gain of the cattle,
quantity and quality of waste produced, feed utilization efficiency,
and treatability of the waste.
Environmental Chamber
The chamber shown as 3, Figure 6, measured 12 by 12 feet in plan
with a 7 foot ceiling height. Environmental parameters controlled
were air temperature and humidity, ventilation rate, and light peri-
odicity and intensity. Air temperature was held to 85° F ± 1°, and
air moisture was maintained at 50 percent relative humidity ± 4 per-
cent. A complete change of air in the chamber was provided every
five minutes. The chambers were lighted 24 hours per day using two
100 watt bulbs. Metering devices were installed to measure the water
consumed by the animals as well as that used for flushing. The con-
crete floors were sloped one-eighth inch per foot to a central floor
drai n.
Each chamber housed three steers having an initial average weight
of 587 pounds each. The feed consisted of an all-concentrate ration
with the composition shown in Table 1. Water was available to the
animals at all times from automatic drinking cups.
The floor surface was hosed down on a daily basis using eight
gallons of water per minute at 150 psi pressure. The total water used
per day was between 40 and 48 gallons. On many occasions mechanical
scraping of the floor preceded washing. All of the flushings flowed
by gravity to a 55 gallon capacity sump as shown in Figures 6 and 7.
The sump was located outside the building and contained a submergible
sump pump.
Anaerobic Treatability Studies
A two stage digestion system with a capacity of 30 gallons per
stage was set up adjacent to the controlled environment chamber. A
schematic sketch of the anaerobic system is shown in Figure 7. Both
stages of digestion were maintained at 97° F by means of electrical
heating units side mounted in each digester. Each digester was mixed
continuously by means of a small centrifugal pun.p. Gas production
from each digester was continuously measured by means of a wet test
meter. Samples of the gas in each stage were collected with gas tight
syringes.
Operational Procedures. On a daily basis, when the chamber was
being hosed down the sump pump B^was piped such that the flushings
were continuously circulated in the sump /\. After the environmental
chamber was cleaned, six gallons of digested liquor were withdrawn
37
-------
GAS
AIR
FEED
WATER
u>
00
3
BEEF
CATTLE
BEEF
CATTLE
WASTE
TO FIELD
}•
ENVIRONMENTAL
CHAMBER
SUMP
TANK
PILOT
PLANT
FIGURE 6. SCHEMATIC SKETCH SHOWING THE ENVIRONMENTAL CHAMBERS AND ASSOCIATED
TREATMENT FACILITIES
-------
TO 'STACK
c*>
FROM
ENVIRONMENTAL
CHAMBER
LEGEND
A RECIRCULATORY PIPING
B SUMP TANK
C,D SAMPLING VALVES
E,F HEATING UNITS
G,H PRESSURE CONTROLLERS
I ORSAT
J.K HG MANOMETERS
L,M WET TEST METERS
FIGURE 7. SCHEMATIC SKETCH OF THE ANAEROBIC DIGESTION PROCESS USED FOR CATTLE WASTE.
-------
from Stage 2 and replaced with six gallons of effluent from Stage 1.
Then Stage 1 was fed six gallons of completely mixed flushings. The
pressure in each digester was controlled by means of a mercury ma-
nometer, Q and H. The average pressure was 5.1 in. Hg.
Analyses. Gas samples were analyzed for methane and carbon
dioxide content using an F & M Model 500 Gas Chromatograph. C-H-N
analyses were conducted on a Model 185 Hewlett-Packard C-H-N Analyzer.
The chemical and biochemical tests were performed in accordance with
procedures outlined in "Standard Methods."
Seeding. Each digester was seeded initially with 30 gallons of
digesting feedlot runoff collected from runoff pits adjacent to the
cattle feedlots.
Objectives. There are two basic interrelated pollutional prob-
lems in each feedlot operation, namely, (a) the solid waste that
accumulates on the feedlot floor and its periodic removal, and (b)
the liquid runoff resulting from precipitation that must be treated
and/or disposed of in a manner to prevent undue pollution of the
environment. The primary purpose of this short term study was to
determine the treatability of solid wastes from a modified environ-
mental feeding facility housing three feeder steers using a two stage
anaerobic digester. A summary of the average results obtained in
this study are shown in Table 18.
Staged Digestion. Recent literature dealing with anaerobic di-
gestion methods indicates considerable interest is now being given
to utilization of a two step completely mixed digestion process in
which the first stage allows the acid forming bacteria to produce
such organic acids as acetic, propionic, etc., and the second stage
promotes the methane producing bacteria which use these acids as a
substrate.
BOD and COD Reduction. The mixed waste flushed from the floor
of the environmental chamber using approximately 45 gallons of water
per day had an average BOD concentration of 6500 mg/1 and an average
COD concentration of 13,000 mg/1. At the beginning of the experi-
ment, when the average weight of the animals was 587 pounds each,
the BOD production rate was approximately 0.8 pounds of BOD per ani-
mal per day. With the volume of washwater held constant, the con-
centration of BOD in the flushings increased with the size of the
animals. The maximum rate of production of BOD was 0.9 pounds per
animal per day when the animals weighed approximately 775 pounds
each. Similarly, the COD concentration increased gradually with an
increase in animal size ranging from 11,500 to 13,600 mg/1.
Under the operating conditions described, namely ten-day reten-
tion time, 97° F, and complete mixing, the average BOD and COD reduc-
tions were found to be 58 and 40 percent, respectively. It should
40
-------
also be noted that the majority of the BOD removal was obtained in
Stage 2. Although these percent removals are not satisfactory in
themselves as a means of standard treatment, it is felt that addi-
tional studies should continue especially in optimizing each stage
for such removal.
TABLE 18. SUMMARY OF AVERAGE RESULTS OBTAINED FROM A COMPLETELY
MIXED TWO STAGE DIGESTER WITH A CAPACITY OF 30 GALLONS
PER STAGE, OPERATING AT 97° F AND A DAILY FEED RATE OF
SIX GALLONS
Gas Production, Stage 1, STP 4.3 ft?/day/ft? capacity
Stage 2, STP 2.82 ftVday/ftJ capacity
CHA, Stage 1, STP 53%
* Stage 2,'STP 72%
C:N, Feed 16.2
After 10 days digestion 9.4
pH, Feed 7.3
Stage 1 6.3
Stage 2 7.1
Volatile Acids, Stage 1 2,990 mg/1
Stage 2 1,030 mg/1
Alkalinity, Feed 2,100 mg/1
Stage 1 3,750 mg/1
Stage 2 4,700 mg/1
Average 5 day BOD, Feed 6,900 mg/1
After 10 days digestion 2,900 rag/1
Average COD, Feed 13,000 mg/1
After 10 days digestion 7,800 mg/1
Gas Production and Composition. The daily gas production at
standard temperature and pressure (STP) per stage as a function of
days of operation is shown in Figure 8. The average daily cubic feet
of gas per cubic foot of capacity in Stage 1 was slightly more than
two times that for Stage 2, namely 4.3 ft3/ft3 versus 2.8 ft3/ft3,
respectively. Figure 9 shows that the average methane concentration
in Stage 2 was 35 percent greater than in Stage 1, 72 percent versus
53 percent, respectively. These two values tend to give credence to
the concept of an acid forming stage followed by a methane bacteria
stage. The overall digestion process produced 5.7 ft3 Cfy per ani-
mal per day measured at standard conditions.
2H_. Figure 10 shows the variation of pH in each stage during
the 55 day period." It is interesting to note that the pH in each
41
-------
ro
Q.
O
CO
Li_
CO
U.
*
Q_
to
Q
§
Q-
CO
CD
>-
5.0^-
n 4.0
2.0
1.0
10
LEGEND
NOTE: DIGESTER CAPACITY PER STAGE
4.0 FT3
o
-0 STAGE 1
Q-
STAGE 2
I
I
I
15
20 25 30
DAYS OF OPERATION
35
40
45
50
FIGURE 8. GAS PRODUCTION AS A FUNCTION OF TIME IN A TWO-STAGE ANAEROBIC DIGESTER.
-------
-p.
co
80
70
60
50
40
0
10
LEQEND
STAGE 1
Q Q STAGE 2
I
I
I
15
20 25 30
DAYS OF OPERATION
35
40
45
50
FIGURE 9. PERCENTAGE METHANE AS A FUNCTION OF TIME IN A TWO-STAGE ANAEROBIC DIGESTER.
-------
8.0
7.5
7.0
6.5
6.0
LEGEND
O-
•O STAGE 1
-Q STAGE 2
NOTE: FEED pH = 7.3
DIGESTION TEMPERATURE = 97°F
0
10
15
20
25
30
35
40
45
50
FIGURE 10. pH AS A FUNCTION OF TIME IN A TWO-STAGE ANAEROBIC DIGESTER.
-------
stage remained relatively uniform after an acclimation period of ap-
proximately 20 days. No chemicals were added for pH control during
the experiment. The average pH of Stage 1 was 6.3 whereas Stage 2
had an average pH of 7.1, indicating the possibility of an initial
acid forming stage. The pH of the mixed flushings was 7.3, and it
changed very little throughout the experiment.
t
Volatile Acids and Alkalinity. Figure 11 shows the relation-
ship of volatile acids and alkalinity in each stage during the 55
day study. The specific interaction between volatile acids and al-
kalinity is not apparent from these data, although it can be noted
that the alkalinity was always in excess of the volatile acid con-
centration. It is also interesting to note that the volatile acids
concentration in Stage 1 was considerably higher than Stage 2, which
is again indicative of an acid forming stage. The relatively high
values of alkalinity come from the high carbonate content present in
the all-concentrate ration shown in Table 1.
C-H-N Analyses. Several samples of the mixed flushings as well
as the effluent from Stage 2 were analyzed for carbon, hydrogen, and
nitrogen content. The average carbon to nitrogen ratio for the mixed
flushings was 16.2 and the C:N ratio of the effluent was 9.2.
The carbon to nitrogen ratio of the feed indicated that this
material is compostible. It should also be noted that there was a
considerable amount of carbonaceous material remaining after ten
days of digestion. The high COD values obtained for the effluent
also substantiate this observation.
Aerobic Treatability Studies. Warburg Respirometer studies
were conducted using flushings from the environmental chambers and
runoff resulting from precipitation. The BOD of the flushings from
the environmental chamber as determined by Warburg Respirometer
studies averaged about 6,500 mg/1, about 15 percent more than the
five day BOD as determined by the conventional dilution method.
The 37° C reaction rate constant for waste flushed from the
controlled environment chamber was found to be very nearly 0.5 per
day. This relatively high rate suggested that the wastes could be
stabilized rather quickly by conventional aerobic treatment processes,
but this did not prove to be the case in bench-scale laboratory
studies.
Respirpmeter studies were also conducted using runoff resulting ,
from precipitation on conventional feedlots. In general, the results'
obtained tended to be-erratic and inconclusive. For example, total
oxygen consumed in a 24^hour period tended to increase with increas-
ing dilutions of the sample, indicating either that toxic or inhibi-
tory elements were initially present in the waste or were produced by
the microorganisms degrading the waste. This finding confirmed re-
sults of an experiment in which a bench-scale activated sludge unit
45
-------
5000
CO
4000
3000
LEGEND
ft STAGE 1
Q Q STAGE 2
23
LU
o
4000
3000
2000
1000
0
10
15
20 25 30
DAYS OF OPERATION
35
40
45
50
FIGURE 11. ALKALINITY AND VOLATILE ACIDS AS FUNCTIONS OF TIME IN A TWO-STAGE ANAEROBIC
DIGESTER.
-------
was utilized for treatment of similar runoff. In this experiment
a 24-hour detention time in the unit resulted in a BOD reduction of
only about 20 percent. Extended aeration studies of the waste at
the conclusion of the experiment indicated that an extremely long
aeration period of approximately 60 days would be required for effec-
tive stabilization of the waste.
47
-------
LABORATORY SIMULATION STUDIES
Because of the extremely erratic nature of natural precipitation
that occurs in the Southwest in general, a considerable amount of
attention was devoted to characterization of feedlot runoff by labora-
tory simulations.
Two types of studies were performed. First,-a series of 12-inch
diameter plastic pipe cylinders were fitted with screens over the
bottom ends. Samples of manure were placed in the cylinders, and water
was sprinkled on the manure to determine the concentration of pollu-
tants in leachates, and the variation of concentration with quantity
of leachate. Second, a simulated feedlot surface in the form of a
tilting table was constructed and equipped with a sprinkler system de-
signed to apply simulated rainfall over a wide range of intensities.
Experiments with Percolation Cylinders
Several 12-inch diameter plastic pipe cylinders were equipped
with screened openings on the lower end as described earlier. Arrange-
ments were made for catching and measuring the quantity of water per-
colating through the cylinders, and a sprinkler device was designed to
apply water to the cylinders at a uniform rate of one-inch per hour.
In-piace density measurements of manure derived from all-concen-
trate, silage, and alfalfa hay-concentrate rations were then made.
The quantity of manure required to provide two-inch, four-inch, and
six-inch layers of manure in the 12-inch diameter cylinders were then
calculated. Manure was collected at random from different feedlot
surfaces and brought into the laboratory. Enough was weighed out in
each case to provide either two, four, or six inches of manure in the
cylinder, and this amount was placed in the cylinder and tamped down
to the pre-determined density.
The sprinkler was then started and operated for several hours at
an application rate of one-inch per hour. As water started percolating
through the cylinder, it was separated into increments of one inch of
percolated water. That is, the first inch percolating through the
column was placed in one sample container, the second inch in another,
and so on. Four inches of leachate were thus collected from each
cylinder. Each sample was then analyzed to determine its concentration
of total, volatile, and suspended solids, COD, BOD, ammonia nitrogen,
nitrate nitrogen, organic nitrogen, and alkalinity. Some typical re-
sults derived from this experiment are shown in Tables 19 through 22.
Data in the above four tables corroborate and extend data gath-
ered from the field in that they indicate that a very small depth of
manure of the feedlot surface contains enough pollutants to pollute
grossly any quantity of rainfall that is likely to occur. For exam-
ple, the concentrations of pollutants contained in the first inch of
49
-------
TABLE 19. CONCENTRATIONS OF COD IN WATER PERCOLATING THROUGH DEPTH
OF MANURE IN COLUMNS AS SHOWN (mg/1)
Quantity
of
Leachate
(in.)
Depth
of
Manure
(in.)
Ration From Which Manure Derived
Al 1 -Concentrate
m
Al f al fa-Concentrate
Silage2
1
2
3
4
1
2
3
4
1
2
3
4
2
2
2
2
4
4
4
4
6
6
6
6
27,000
15,800
10,200
3,800
21 ,200
18,500
15,800
13,700
22,800
21 ,600
21,100
21 ,800
13,600
8,300
6,700
4,900
14,900
11,600
9,100
8,400
19,200
14,300
12,000
9,400
5,000
2,300
980
200
7,900
4,700
2,700
980
7,500
5,700
10,500
2,800
Ration composition same as shown in Table 1, Experiment I, except
that chopped alfalfa substituted for cottonseed hulls.
2
Manure collected from feedlot on which cows were fed a maintenance
ration consisting primarily of silage.
TABLE 20. CONCENTRATIONS OF VOLATILE SOLIDS IN WATER PERCOLATING
THROUGH DEPTH OF MANURE IN COLUMNS AS SHOWN (mg/1)
Quantity
of
Leachate
(in.)
Depth
of
Manure
(in.)
Ration From Which Manure Derived
Al 1 -Concentrate
i
Al f al fa-Concentrate
?
Silage*
1
2
3
4
1
2
3
4
1
2
3
4
2
2
2
2
4
4
4
4
6
6
6
6
21 ,300
14,400
12,200
-
23,400
17,700
14,200
12,800
29,500
22,700
20,700
26,600
13,400
4,700
3,500
3,100
2,700
9,100
5,500
6,600
12,000
11,300
11,400
8,900
4,400
1,600
1,050
750
5,500
2,900
1,950
1,300
6,100
3,500
8,200
2,900
Nation composition same as shown in Table 1, Experiment I, except that
chopped alfalfa substituted for cottonseed hulls.
Manure collected from feedlot on which cows were fed a maintenance
ration consisting primarily of silage.
50
-------
TABLE 21. CONCENTRATIONS OF ALKALINITY IN WATER PERCOLATING THROUGH
DEPTH OF MANURE IN COLUMNS AS SHOWN (mg/1)
Quantity
of
Leachate
(in.)
Depth
of
Manure
(in.)
Ration From Which Manure Derived
Al 1 -Concentrate
i
Al f al fa-Concentrate
-------
water percolating through a quantity of manure were apparently indepen-
dent of the total depth of manure. Also, the concentrations of pollu-
tants contained in the first inch of water percolating through the
manure agreed reasonably well with the average concentrations shown in
Table 8. Most of these latter concentrations were average concentra-
tions for less than one inch of runoff.
The above data make it apparent that, regardless of the quantity
of runoff involved, far more than 99 percent of most pollutants would
have to be removed from the runoff from normal feedlot operations be-
fore such runoff could be discharged to a water course without serious
adverse effect on that water course. This is particularly true in the
Southwestern region of the U. S. where existing water courses tend to
be wet weather streams only.
Experiments with Tilting Table
A feedlot model measuring 12 ft by 4 ft was constructed. This
box was mounted on a fulcrum to allow it to be tilted to any desired
slope along the long dimension. One end of the table was slotted
horizontally with one-half inch slots which extended the width of the
table. These slots, fitted with covered half-round metal gutters were
located 2, 6, and 18 inches below the top of the table. One-inch gal-
vanized pipe was used to construct simple drains from each slot to
calibrated vessels provided to capture the water running off. The
end of the table away from the slots was equipped with a hydraulic
jack which was used to vary the slope of the table and to support its
heavy end.
A sprinkler system was installed approximately six feet above the
table to provide simulated rainfall at any desired rate. The sprin-
kler system was equipped with a rotometer to measure accurately the
rate of flow to the spray nozzles. The City of Lubbock water system
served as the source of supply to the sprinklers.
The box provided a means for placing various depths of different
types of soil and various depths of manure from any source in a simu-
lated feedlot condition, then applying any desired rate of rainfall on
any desired slope and collecting and analyzing the runoff from the
surface, from the manure-soil interface, and from a reasonable distance
below the manure soil interface. It was expected that the experiment
would provide a valuable insight into the rate at which pollutants
move downward through the soil zone, the effectiveness of the organic
barrier that has been postulated by several investigators as a deter-
rent to percolation of water through a feedlot floor, and an indica-
tion of the effect of slope on runoff quality.
A mixture of top soil and caliche, similar to that used as a sur-
facing material on feedlots in the Texas High Plains, was used as a
base material on the tilting table. Samples of in-situ feedlot sur-
facing materials were collected from feedlots on the Texas Tech campus
52
-------
to determine the apparent density. The quantity of base material
required to fill the table to a depth of 12 inches was then calculated,
weighed, and compacted onto the table.
The manure used for experimentation was collected from feedlots
on which cattle were fed a ration identical to that shown in Table 1,
Experiments II and III.
Manure was placed directly on the base material in a layer four
inches thick for two runs, and two inches thick for the third run. The
slope of the table was maintained at three percent for all three runs.
The precipitation rate used for the first run was 1.5 inches per hour,
and one inch per hour for the second and third runs. Runoff samples
were collected every half hour over the one hour test period for the
first run and over the first three hours of the second run. Subse-
quent samples on the second run were collected at four hour intervals
for the last eight hours. Samples were collected at eight hour inter-
vals for the third run. The length of the test period for the second
run was 25.5 hours, and the length of the test period for the third
run was 24 hours.
At the termination of each run, the manure and base material were
examined for moisture content. Visual examination and moisture analy-
ses were utilized for making these examinations.
Upon completion of the first series of runs, the caliche surface
was cleared of manure and a two inch layer of commercial mortar sand
was placed to form an interface or drainage layer between the caliche
and the organic waste.
Two tests were then conducted using manure collected from the
feedlots, in chunks, placed upon the sand. In the first of these runs,
chunks of ten percent roughage manure six inches square, and two inches
thick were placed to form a two inch layer of manure. The layer of
manure, which was not compacted extensively, contained many small cre-
vices. A feedlot slope of three percent was used in conjunction with
a precipitation rate of one inch per hour. Runoff samples were col-
lected at ten hour intervals over the 24 hour test period beginning
four hours after start up. The surface runoff rate was measured at
the end of the run. After the test period, samples of the subsurface
manure were inspected visually.
For the next run, manure was collected from cattle on a dirt-
surfaced feedlot where a ration containing 15 percent roughage was
being fed. The chunks of manure, in approximately ten inch squares
and one to six inches thick, were placed on the sand to form a manure
layer one to six inches thick. Cracks in the manure layer, after
limited compaction, varied in size from one inch down to small crevices.
The feedlot slope used in this experiment was three percent, and the
precipitation rate used was one inch per hour. Runoff samples were
collected at seven hour intervals for the 22.5 hour test period. The
53
-------
surface runoff rate was measured at the end of the run. After the
test period, the manure was inspected visually.
The eroded manure and standing water were removed following each
run, and feedlot manure was added as needed to maintain a high mois-
ture content in the manure and a non-eroded surface. Indentations
were made in the manure surface before each run by manually pressing
boots into the manure surface at random intervals. Precipitation rates
tested were one, two, and three inches per hour. Feedlot slopes tested
were one, three, six, and nine percent. The duration of each run at
each slope and precipitation rate was two hours. The runoff rate was
measured during each run to ascertain water losses and to check roto-
meter accuracy.
On each run, the first sample collected was the first runoff to
appear. Thereafter, samples were collected at 50-minute intervals
during the.first hour for the one inch per hour precipitation rate.
For the precipitation rates of two and three inches per hour, samples
were collected every ten minutes for the first half hour. Samples
were collected every half hour for the remaining 1.5 hours.
The data collected from the simulated feedlot runoff experiments
were plotted on rectangular coordinates and a curve was visually fitted
to the data points. Each of the analyzed characteristics was plotted
against time with a maximum of three characteristics plotted per chart.
These graphs were categorized and analyzed first for the effects of
feedlot slope at each precipitation rate and then for the effects of
precipitation rate at each feedlot slope.
Results
A feedlot slope of three percent and a precipitation rate of 1.5
inches per hour were used in making a one hour run. Only surface run-
off occurred during the run. Visual inspection of subsurface manure
and of base material after precipitation indicated a negligible amount
of water had infiltrated through the manure.
Tests were then conducted on a feedlot slope of three percent and
a precipitation rate of one inch per hour. The effects of manure depth
and extended precipitation on water infiltration through the manure
were studied during the first run of this test. The second run tested
infiltration through four inches of manure for a 25.5 hour precipita-
tion period. The third run of 24 hours tested infiltration through a
two inch layer of manure. Before the second run, manure samples con-
tained 54 percent moisture and before the third run, manure samples
contained 55 percent moisture. Subsurface manure samples were col-
lected at the termination of each run. Samples contained 55 percent
moisture after the second run, and 57 percent moisture after the third
run. Visual examination of the base material again indicated a negli-
gible quantity of water had infiltrated through the manure.
54
-------
The next two runs Explored the effects of compaction and of
roughage content of rations on infiltration rates. The manure applied
to the table contained cracks and open spaces which penetrated the
entire depth of the manure. At the end of each 24 hour run, during
which only surface runoff occurred, the cracks and open spaces were
sealed with manure. The surface runoff rate was measured at the end
of the run and in both cases it equaled the precipitation rate. Again,
visual inspection of the manure indicated that a negligible quantity
of water had infiltrated through the manure pack.
The testing procedure was continued through a total of 12 runs
over a period of approximately three months. Slopes and precipitation
rates investigated are shown in Table 23.
TABLE 23. FEEDLOT SLOPE AND PRECIPITATION RATES STUDIED IN THE
TILTING TABLE EXPERIMENT
Surface Slope (Percent) Precipitation Rate (Inches Per Hour)
1
1
1
3
3
3
6
6
6
9
9
9
1
2
3
1
2
3
1
2
3
1
2
3
Data obtained in these experiments indicated that the concentra-
tion of pollutants in feedlot runoff is highly independent of both
feedlot slope and precipitation rate. The pattern of a high concen-
tration of pollutants in the initial runoff followed by a leveling off
of concentration after about 30 minutes was repeatedly observed in
samples obtained from concrete feedlots during precipitation. However,
it will be noted that concentrations of pollutants in the runoff from
the tilting table were generally almost an order of magnitude less than
the concentrations found in runoff from actual feedlots. The reason
for this large discrepancy is not known, but it is believed to be
largely influenced by the mixing action of cattle hooves as the cattle
move about on the feedlot surface during rainfall. This same animal
action also probably accounts for the much greater penetration of pre-
cipitation through the manure pack on an actual feedlot than was ob-
served in this series of experiments.
Typical results obtained in these experiments are plotted in
Figures 12 through 23.
55
-------
6000
5000
4000
3000
Ixl
O
O
2000
1000
0
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
30 60
TIME, MINUTES
90
120
FIGURE 12. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF ONE PERCENT AND PRECIPITATION
RATE OF ONE INCH PER HOUR.
56
-------
6000
5000
4000
o
t—«
i
t? 3000
o
o
2000
1000
0
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
30 60
TIME, MINUTES
120
FIGURE 13. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF ONE PERCENT AND A PRECIPITATION
RATE OF TWO INCHES PER HOUR.
57
-------
6000
5000
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
4000
C 3000
o
CJ
2000
1000
0
60
TIME, MINUTES
FIGURE 14. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF ONE PERCENT AND A PRECIPITATION
RATE OF THREE INCHES PER HOUR.
58
-------
6000
5000
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
4000
o
3000
o
o
o
2000
1000
0
0
60
TIME, MINUTES
90
120
FIGURE 15. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF THREE PERCENT AND A PRECIPITATION
RATE OF ONE INCH PER HOUR.
59
-------
6000
5000
4000
~ 3000
o
o
2000
1000
0
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
60
TIME, MINUTES
FIGURE 16. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF THREE PERCENT AND A PRECIPITATION
RATE OF TWO INCHES PER HOUR.
60
-------
6000
5000
4000
C 3000
Ul
O
2000
1000
0
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
30 60
TIME, MINUTES
90
FIGURE 17. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF THREE PERCENT AND PRECIPITATION
RATE OF THREE INCHES PER HOUR.
61
-------
6000
5000
4000
o
i—i
i
C 3000
2000
1000
0
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
30 60
TIME, MINUTES
FIGURE 18. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF SIX PERCENT AND PRECIPITATION
RATE OF ONE INCH PER HOUR.
62
-------
6000
5000
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS ;.
A COD
4000
o
i—i
§
~ 3000
o
i
2000
1000
0
60
TIME, MINUTES
90
120
FIGURE 19. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF SIX PERCENT AND PRECIPITATION
RATE OF TWO INCHES PER HOUR.
63
-------
6000
5000
4000
CEF
•k
O
t— i
i
UJ
O
O
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
3000
2000
1000
0
60
TIME, MINUTES
FIGURE 20. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF SIX PERCENT AND PRECIPITATION
RATE OF THREE INCHES PER HOUR.
64
-------
6000
5000
4000
3000
o
§
2000
1000
a
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
30 60
TIME, MINUTES
90
120
FIGURE 21. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF NINE PERCENT AND PRECIPITATION
RATE OF ONE INCH PER HOUR.
65
-------
6000
5000
4000
C 3000
o
o
2000
1000
0
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
60
TIME, MINUTES
90
120
FIGURE 22. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF NINE PERCENT AND PRECIPITATION
RATE OF TWO INCHES PER HOUR.
66
-------
6000
5000
4000
(IT
o
t—I
i
o
o
3000
2000
1000
0
D ALKALINITY
O VOLATILE SUSPENDED
SOLIDS
A COD
30 60
TIME, MINUTES
90
FIGURE 23. POLLUTANT CONCENTRATIONS IN SIMULATED FEEDLOT RUNOFF
FOR A FEEDLOT SLOPE OF NINE PERCENT AND PRECIPITATION
RATE OF THREE INCHES PER HOUR.
67
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RELATED RESEARCH AT TEXAS TECH
Composting Studies
In an attempt to study possible means of stabilizing beef cattle
feedlot solid waste, a three and a half year aerobic composting re-
search project was initiated at Texas Tech University and funded by
the Farmstead Engineering, Livestock Engineering and Farm Structures
Research Branch, AERD, ARS, USDA.
The study fs being conducted in the vicinity of Lubbock, Texas,
using accumulated waste collected from'commercial and research beef
cattle feedlots during different times of the year to determine the
effects of climate on the compostibility of the solid waste material.
Waste has also been collected from cows fed various commercial ra-
tions and maintained on different management systems involving open
and covered lots, paved and unpaved surfaces, and different popula-
tion densities. Some of the collected waste was allowed to form a
normal moisture balance with the atmosphere while other samples were
taken from lots in which the accumulated feedlot waste was kept con-
tinuously moist.
Research involving the aerobic stabilization of solid material
was conducted in specially designed drum digesters and in open air
piles. In both cases, physical, chemical, and biological data were
collected during the digestion periods. Each container was construc-
ted from a fifty-five gallon drum mounted to allow rotation about
the cylindrical axis. An air distribution system was installed to
inject metered temperature- and humidity-controlled air into the test
sample. Heat transfer from the drum was limited by a blanket insula-
tion about the drum surface. The drums were located in a controlled
environment room. Temperature within the mass was continuously re-
corded and exhaust gas samples were periodically taken from each
digester.
Composting in piles was conducted in the open. The piles were
varied in size and shape to establish the effects of the physical
dimensions on the composting process.
Research Findings
All beef cattle feedlot waste materials from all lot surfaces,
feeds, and management systems were found to be composttble to a final
uniform state, although the rate of composting and the condition of
the material during the composting process varied greatly. Consider-
able variation existed in initial physical, chemical, and biological
characteristics of the waste as collected from the feedlot surface.
This variation was the result of the differences in feed, population
densities, cltmatic conditions, and waste management during the period
of accumulation.-
69
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Feed types studied ranged from all-concentrate to high rough-
age content feeds. All types stabilized readily, although the rate
of stabilization was greater with high roughage content than with
all-concentrate feeds. Two factors seem to be involved: the par-
ticle size and the C/N ratio. The uniformly small-sized particles
of all-concentrate feeds possessed a higher degree of compaction and
a smaller void ratio. In addition, the material readily caked to
form lumps which restricted the flow of air through the mass. As
a result of the limited oxygen supply, areas within the all-concen-
trate waste became anaerobic. Waste materials containing larger
organic particles were less compact and optimum air movement was
obtained more easily. As a result, the entire mass remained aerobic
and biological activity continued at a higher level.
Carbon-Nitrogen Ratio
The C/N ratio of the accumulated waste varied from 35 to 9
according to feed type, degree of stabilization, and climatic con-
ditions during accumulation. These factors were interrelated and
specific effects of each have not been determined. In all cases
tested, waste material with both high and low C/N ratios were suc-
cessfully stabilized, although the rate of composting and the tem-
perature of the mass varied considerably. Little difference in
composting rate was noted when the C/N ratio was above 30. When the
C/N ratio ranged below 25, the rate of stabilization was consider-
ably slower. In some cases, up to two months were required for the
internal temperature of the composting mass to drop to within 5° C
of the ambient temperature. This compared with a composting time
of two to four weeks for waste with more nearly optimum C/N ranges.
The rate of loss of carbon and of nitrogen varied during com-
posting. Carbon loss appeared to take place during the entire
process while nitrogen loss as ammonia gas occurred mostly during
the early stages of stabilization when the temperature of the mass
was at its peak. Since these rates varied, the C/N ratio first in-
creased during the early stages of composting then later decreased
as the release rate of ammonia diminished.
Partial stabilization of moist accumulated waste on the feedlot
surface was evident during warm weather periods. This biological
decomposition of waste during the accumulation period resulted in
a reduction of composting time and composting temperatures. When
waste accumulated in a dry state during cold or hot weather, little
stabilization was evident and the full composting cycle was required.
Waste accumulated during cold weather retained the biological vigor
of fresh manure even when it remained moist on the feedlot floor.
The means by which the waste was kept moist on the lot did not
materially affect the stabilization during the accumulation period.
High moisture content waste was obtained by natural rainfall, by
artificial sprinkling, or by maintaining a high animal population
70
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density on the lot. In either case the degree of stabilization was
the same provided the depth of accumulated waste was equal. During
wet weather the waste remained drier on the roofed lots than on un-
covered lots, but at high animal population densities little dif-
ference was noted in the composting time.
Moisture Content
On a wet weight basis a moisture content of at least 30% was
required for aerobic composting. Limited composting was evident at
lower moisture levels, but at a greatly reduced biological activity
rate and at lower temperatures. At moisture levels in excess of
50% in high concentrate feeds and in excess of 60% in high roughage
feeds, a reduction of the rate of stabilization was noted. This
probably was the result of the reduction of void spaces within the
mass and the partial oxygen starvation of the aerobic organisms.
Insect Infestation
The moist waste as collected from beef feedlots was an extremely
attractive material for flies. The attraction seemed to increase
during the very early stages of composting until the temperature of
the mass exceeded 50° C for over 24 hours. During the later stages
of composting no fly attraction or activity was noted. The high
temperatures of aerobic stabilization killed the larvae and eggs in
the mass and no live larvae were found after composting.
Oxygen Requirements
The oxygen requirements necessary for aerobic stabilization
varied with the rate of biological activity, being greatest during
the early stages of composting when the temperature of the mass was
highest. Oxygen requirements dropped sharply later in the compost-
ing process.
When the air supply rate per 100 pounds of manure exceeded three
liters per minute, the temperature of the mass dropped and the rate
of composting decreased. This seemingly was the result of excessive
cooling by the supply air. At air supply rates below 1.5 liters per
minute, the rate of composting decreased due to oxygen starvation.
The optimum supply rate for the peak composting period ranged between
1.5 and 3 liters per minute per 100 pounds of organic material. Dur-
ing the later stages of composting, the oxygen requirements decreased
with the biological activity level. Maximum biological activity was
also noted when the oxygen level in the exhaust gases ranged from 10
to 12%. Below 5% oxygen a sharp reduction in heat production was
noted and the time for stabilization was considerably lengthened.
Above 12% oxygen excessive cooling and dehydration occurred. Par-
ticle size also affected the rate and degree of stabilization. When
dense lumps of waste exceeded 1 inch in diameter, aerobic stabiliza-
tion occurred around the surface while the center of the lump remained
anaerobic.
71
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Drum Stabilization
Several problems were encountered during preliminary aerobic
digestion trails. The first involved the system used to supply
oxygen to the aerobic digestion process. This air, supplied by a
compressor, had a low moisture content and caused considerable evap-
orative cooling to take place within the mass. With this excessive
cooling, thermophylic digestion was not established. A modification
in the supply system to saturate and heat the injected air resulted
in a rapid biological start in the composting process reaching full
thermophylic activity within 24 hours.
Air was injected into the organic mass through a perforated
pipe located on the bottom of the drum extending along a line paral-
lel to the cylindrical axis. The air tended to channel upward through
the waste, to supply air unevenly, and to create areas of varying
bacterial activity. The drums were rotated to provide uniform air
distribution and to blend the areas of uneven temperatures. Continu-
ous mixing caused the organic particles to adhere and form large
balls and rolls of slightly compacted waste. Balling occurred at
moisture levels above 50% on most waste materials tested. When mix-
ing was limited to five revolutions twice daily, no balling occurred
and no reduction of activity was noted. Waste from high-roughage
feeds had less tendency to ball than that from low-roughage high-
concentrate feeds.
In the low-roughage waste, air readily channeled at moisture
levels in excess of 45%. This channeling was found to develop within
an hour of mixing and resulted in an uneven distribution of air
through the mass.
Time for Stabilization
The organic waste expended its ability to maintain high tem-
perature digestion in about ten days under the most nearly ideal con-
ditions. The heat produced by bacterial action during this time
period caused the temperature to rise to an early peak and then to
decrease gradually to within 5° C of the ambient air, forming a
classical composting curve. During the composting cycle the average
decreases in volume and weight of dry matter were 24% and 32%, re-
spectively. The total weight of potassium and potash remained con-
stant, but increased per unit dry matter. Nitrogen was lost as
ammonia gas early in the digestion process, but on a unit dry matter
basis its concentration increased slightly during the composting
period.
Open Air Piles
Waste was composted in open air piles throughout the year. Man-
agement was critical during dry weather since the outer layer of the
72
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pile dehydrated rapidly. The addition of water was required at mixing
to maintain a moisture level of over 40 percent.
Mixing of the piled organic mass served to control the infesta-
tion of the fly larvae at the surface during the early stages of
composting by killing the fly larvae and eggs in the high temperatures
of the pile interior.
Mixing of the piles also introduced oxygen to the interior of
the pile and mixed the areas of varying biological activities. Com-
posting required considerably more time in open air piles than in
controlled digesters since the stabilization process did not progress
uniformly. In both digester and open air piles, the final product of
biological digestion by composting was similar.
Summary
The organic stabilization of beef feedlot waste by composting is
a feasible process. Organic beef feedlot waste is compostible in
either specially designed digesters or in exposed open air piles, to
a biologically stable organic product, free from noxious odors and
insect infestation. Stabilized waste can be stored in a wet or dry
state without danger of heating, attracting insects, or causing nox-
ious odors. The time of stabilization depends on the type of origi-
nal feed material, the condition of the waste at the start of the
composting period, and the management of the composting process. Com-
posting requires skilled management to obtain satisfactory results.
Agronomic Studies
The primary objective of the agronomic research was to determine
the usefulness of cattle feedlot runoff for crop production.
The runoff materials used in these studies came from both dirt
and concrete-surfaced feedlots.
Runoff was also obtained from differing slopes of dirt-surfaced
lots. Runoff used resulted from both natural rainfall and artificial
flushing or washing. These runoff materials were used in studies in
growth rooms either directly as they came from the catch pits or di-
luted with water, on cotton, grain sorghum, wheat, barley, rye, soy-
beans, and bermuda grass, all commonly grown crops in the irrigated
area of West Texas. Original treatments ranged from two to eight
surface inches, either biweekly or weekly, in an attempt to determine
the upper limit of feedlot runoff that could be used in crop produc-
tion. Results of these studies indicated that plant species vary
greatly in the amount of feedlot runoff they can tolerate. Bermuda
grass was the most tolerant, grain sorghum the next most tolerant,
small seeded winter annuals relatively intolerant, cotton intolerant,
and soybeans very intolerant. The germinating and tender seedling
stages of field crops were shown'to be most susceptible to damage.
73
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Runoff from concrete lots appeared to be about twice as damag-
ing as runoff from dirt lots. Crop damage was positively correlated
with type of ration on dirt-surfaced lots. Seven weekly applications
of two surface inches of runoff from a dirt surface feedlot applied
weekly increased bermuda grass growth by 17 percent, decreased grain
sorghum growth by 60 percent and decreased wheat growth by 72 percent.
A similar treatment with concrete-surfaced feedlot runoff decreased
bermuda grass growth by 70 percent, decreased grain sorghum growth
by 88 percent, and decreased wheat growth by 99 percent plus.
In germination tests six surface inches of dirt feedlot runoff
applied over a three week period reduced grain sorghum germination
by 25 percent, reduced cotton germination by 33 percent, and reduced
wheat germination by 30 percent, whereas six surface inches of con-
crete feedlot runoff applied over the same period of time reduced
grain sorghum germination by 75 percent. Studies under field condi-
tions and undisturbed soil tended to confirm the basic finding noted
in small plots and in growth rooms.
Biweekly application of two surface inches of feedlot runoff
applied to well established cotton and grain sorghum that are five
to six weeks old does not appear to be so damaging. In some in-
stances, it can be beneficial in crop growth, and single applications
of up to four surface inches of feedlot runoff can be beneficial to
crop growth if applied to well established crops. Soil analyses for
soluble salt, sodium, and chloride, indicate that these minerals are
accumulating in the top 24 inches of soil profile.
On soils receiving seven biweekly applications of two surface
inches of runoff from concrete feedlots, soluble salts in the top
30 inches increased 3,321 pounds per acre, from 7,989 pounds to
11,310 pounds. Sodium increased 805 pounds per acre. Nitrate ni-
trogen increased somewhat but was highly variable depending upon
crop growth and time of sampling.
In summary, livestock feedlot runoff offers potential as a
resource to be used for crop production. It should not be applied
in large quantities to soil immediately before planting nor to ten-
der seedlings. It can be applied to established crops if care is
taken as to amounts, source, and crop species.
74
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ACKNOWLEDGMENTS
The support by the Environmental Protection Agency of the re-
search on which this report is based is hereby gratefully acknowl-
edged. The Animal Science Department of Texas Tech University also
contributed substantially to the project and this contribution is
most sincerely appreciated.
Some of the data presented in the report were obtained from a
parallel study funded by the Farmstead Engineering, Livestock Engi-
neering and Farm Structures Research Branch, ERD, ARS, USDA. This
support is also sincerely appreciated and is hereby gratefully ac-
knowledged.
The Texas Water Quality Board has provided continuing support
for the agronomic studies which are summarized in the report, and its
support is most sincerely appreciated.
The support of all three agencies, which made possible better
coordinated total effort than would otherwise have been possible, has
improved the effectiveness of the entire research program, and the
willingness of all three agencies to become involved in such a coop-
erative program is most commendable.
The assistance of Mr. Marion R. Scalf, Project Officer for EPA,
in expediting the work and in reviewing the manuscript promptly is
sincerely appreciated.
The research performed by Donald L. Spraggins, John Malouf, Dong
Soo Whang, Leonard Keeton, D. W. Keeling, and J. L. Winstead, all
graduate students at Texas Tech University, was of material benefit to
the completion of the project, as was the very capable and willing
assistance of Mr. Carl Carter, Technician in the Department of Agricul-
tural Engineering.
Finally, the patience and skill of Mrs. Raynell Keller in typing
and assembling the final manuscript are most sincerely appreciated.
Texas Tech University
Dan M. Wells, Director,Water Resources Center
Robert C. A!bin, Associate Professor:, Department of Animal Science
Walter Grub, Associate Professor, Department of Agricultural Engi-
neering
Eugene A. Coleman, Associate Professor, Department of Agronomy
George. F. Meenaghan, Professor and Chairman, Department of Chemical
Engineering.
75
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PUBLICATIONS
Grub, Walter, Albin, R. C., Wells, D. M., and Wheaton, R. Z., "The
Economic and Engineering Feasibility Analysis of Cattle Feedlot
Runoff Pollution Control", Report to the Texas and Southwestern
Cattle Raisers Association and Coordinating Board, Texas Col-
leges and Universities System, (23 pp.), February, 1968.
4
Grub, Walter, Albin, R. C., Wells, D. M., and Owens, T. R., "Feedlot
Design and Management for Pollution Control", Proceedings, 1968
Beef Cattle Conference, April, 1968, Lubbock, Texas.
Grub, Walter, Albin, R. C., Wells, D. M., and Wheaton, R. Z., "The
Effect of Feed, Design, and Management on the Control of Pollu-
tion from Beef Cattle Feedlots", Agricultural Animal Waste Con-
ference, Cornell University, Syracuse, New York, January, 1969.
Wells, D. M., Grub, Walter, Albin, R. C., and Wheaton, R. Z., "Aerobic
Decomposition of Solid Wastes from Cattle Feedlots", Agricultural
Animal Waste Conference, Cornell University, Syracuse, New York,
January, 1969.
Owens, T. R., Wells, D. M., Grub, Walter, Albin, R. C., Coleman, Eugene,
"Some Physical and Economic Aspects of Water Pollution Control
for Cattle Feedlot Runoff", WPCF 42nd Annual Conference, Dallas,
Texas, October, 1969.
Wells, D. M., Grub, Walter, Albin, R. C., Meenaghan, G. F., and Coleman,
Eugene, "Characteristics of Runoff from Southwestern Cattle
Feedlots", Texas Section, ASCE Fall Meeting, Lubbock, Texas,
October, 1969.
Wells, D. M., Coleman, Eugene, Grub, Walter, Albin, R. C. and Meenaghan,
G. F., Cattle Feedlot Pollution Study, Interim Report No. 1 to
Texas Water Quality Board, Austin, Texas, (34 pp.), November, 1969.
Grub, Walter, Wells, D. M., Coleman, Eugene, Albin, R. C. and Meenaghan,
G. F., "Handling Beef Cattle Waste", Proceedings of Southern
Agricultural Workers Conference 66th Meeting, Memphis, Tennessee,
February, 1970.
Wells, D. M., Grub, Walter, Albin, R. C., Meenaghan, G. F., and Coleman,
Eugene, "Control of Water Pollution from Southwestern Cattle
Feedlots", Fifth International Conference on Water Pollution
Research, San Francisco, California, July, 1970.
Meenaghan, G. F., Wells, D. M., Albin, R. C., and Grub, Walter, "Gas
Production from Beef Cattle Wastes", 1970 Winter Meeting Ameri-
can Society of Agricultural Engineers, Chicago, Illinois, Decem-
ber, 1970.
85
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Keeton, Leonard L., Wells, D. M., Grub, Walter, Meenaghan, G. F., and
Albin, R. C., "Effects of Manure Depth on Runoff from Southwestern
Cattle Feedlots", 1970 Winter Meeting, American Society of
Agricultural Engineers, Chicago, Illinois, December, 1970.
Albin, R. C., "Handling and Disposal of Cattle Feedlot Wastes", Sym-
posium on Animal Waste Management, Annual Meeting, American
Society of Animal Science, August, 1970, University, Park, Pa.
In Press, Journal Animal Science.
Albin, R. C., "Feedlot Waste Management Systems", Proceedings, 1970
Beef Cattle Conference, October, 1970, Lubbock, Texas.
86
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APPENDIX A
Analytical Procedures
Procedures detailed in Standard Methods for the Examination of
Mater and Wastewater. USPHA, AWWA, WPCF, 12th Edition, were used for
the routine analysis of runoff samples. However, in order to improve
accuracy and repeatability of results, one modification was adopted.
This modification consisted of breaking off approximately two milli-
meters of the end of volumetric pipettes used in measuring samples.
This procedure increased the bore of the pipette substantially and
permitted passage of the larger particles that were commonly found in
runoff without substantially changing the volume of liquid contained
in the pipette. This procedure was particularly important in obtaining
repeatable results with BOD and COD tests, and was of less importance
in obtaining repeatability of other tests.
Procedures recommended by the manufacturer were followed carefully
in analyzing samples on the Hewlett-Packard CHN Analyzer.
8T
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I 1 Accession Number
w
j Subject Field & Group
05 B
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
£ Organization
Lubbock, Texas
Title
Characteristics of Wastes from Southwestern Cattle Feedlots
1 Q Authors)
Wells,
Albin,
/•>_.. k i
Dan M.
R. C.
1-1 4->%».
16
21
Project Designation
EPA, WQO Grant No. 13040 DEM
01/71
Note
Coleman, Eugene A.
Meenaghan, G. F.
22
Citation
23
Descriptors (Starred First)
*Runoff, *Livestock, Characteristics, *Cattle Feedlots
95 Identifiers (Starred First)
*Southwestern Cattle Feedlots, *Quality of Runoff
Abstract
Research was conducted on the experimental feedlots in Lubbock, Texas, to determine
the characteristics of wastes from Southwestern cattle feedlots. The feedlots were
generally operated in a manner conforming to normal commercial feeding operations in the
area. They were provided with collection pits and allowed the quantity of runoff to be
measured accurately, and samples of runoff were collected routinely both during rainstorms
and from the collection pits. Manure samples were also collected routinely for analysis.
Results of the research show that the quantity of runoff per unit area of concrete-
surfaced lots is substantially greater than the quantity per unit area of dirt-surfaced
lots, and that the concentrations of pollutants in concrete-lot runoff are substantially
higher than corresponding concentrations in runoff from dirt-surfaced lots.
The quantity of solid waste derived from cattle being fed an all-concentrate ration
is less than half as great as the quantity derived from cattle being fed a 12 percent
roughage ration. Additional studies showed that all solid waste derived from cattle feeding
operations are readily compostible, although the rate of composting is influenced to some
extent by the type of ration, moisture content of the waste on the feedlot floor, and
other factors. Agronomic studies indicate that runoff can be used for irrigation of crops,
but extreme caution is required in the application of runoff to crops to prevent damage
to them.
Abstractor
Dan M. Wells
Institution
Texas Tech University Water Resources Center
WR:I02 (REV. JULY 198B)
WRSIC
SEND. WITH COPY OF DOCUMENT. TOl WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 20240
* OPO: 1870-389-930
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