s>EPA
United States
Environmental Protection
Agency
Municipal Environmental Research EPA-600/8-80-033
Laboratory August 1 980
Cincinnati OH 45268
Research and Development
Compendium on
Solid Waste
Management by
Vermicomposting
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the "SPECIAL" REPORTS series. This series is
reserved for reports targeted to meet the technical information needs of specific
user groups. The series includes problem-oriented reports, research application
reports, and executive summary documents. Examples include.state-of-the-art
analyses, technology assessments, design manuals, user manuals, and reports
on the results of major research and development efforts.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/8-80-033
August 1980
COMPENDIUM ON
SOLID WASTE MANAGEMENT
BY VERMICOMPOSTING
by
Camp Dresser & McKee, Inc.
Boston, Massachusetts 02108
Contract No. 68-03-2803
Project Officer
Laura A. Ringenbach
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publi-
cation. Approval does not signify that the contents necessarily reflect
the view and policies of the U.S. Environmental Protection Agency, nor
does mention of trade names or commercial products constitute endorsement
or recommendations for use.
ii
-------
FOREWORD
The U.S. Environmental Protection Agency was created because of
increasing public and government concern about the dangers of pollution
to the health and welfare of the American people. Noxious air, foul
water, and spoiled land are tragic testimonies to the deterioration of
our natural environment. The complexity of that environment and the
interplay of its components require a concentrated and integrated attack
on the problem.
Research and development is that necessary first step in problem
solution; it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems to prevent, treat, and
manage wastewater and solid and hazardous waste pollutant discharges from
municipal and community sources, to preserve and treat public drinking
water supplies, and to minimize the adverse economic, social, health, and
aesthetic effects of pollution. This publication is one of the products
of that research and provides a most vital communications link between
the researchers and the user community.
This report provides an engineering and scientific assessment of munici-
pal solid waste management by vermicomposting. Vermicomposting is the
conversion of waste materials by earthworm consumption to castings which
may be used as a soil amendment.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
-------
ABSTRACT
Vermicomposting -- the conversion of organic matter that occurs as earth-
worms feed on waste materials -- has been proposed as a method of
managing municipal solid wastes. Some species of earthworms (Eisem's
foetida and Lumbricus rubellus) can consume wastes and expel the remains
as castings. The casting have properties that make them a desirable soil
amendment.
Vermicomposting of municipal solid wastes has been attempted only in the
last five years and there are presently no full-scale operations. This
report assesses the technical and economic feasibility of vermicomposting
and is based on several pi lot-scale studies conducted by private
entrepreneurs.
The assessment is based on examining facilities and costs for a municipal
operation serving (1) a community of 50,000 persons and (2) a community
of about 500,000 persons. Vermicomposting is compared to three other
methods of solid waste management: sanitary landfill, windrow com-
posting, and combustion. Vermicomposting was estimated to cost about $24
to $32 per ton of waste processed. This cost is high compared to most
other available methods. Additionally, the market for earthworm castings
is not established. Since total process costs, including revenue from
sale of products, are central considerations in the selection of a pre-
ferred solid waste management option, the typical communities examined in
this report have available to them technologies which are more attractive
than vermicomposting.
IV
-------
CONTENTS
Foreword
Abstract
Tables
Figures
Acknowledgments
Section 1. EXECUTIVE SUMMARY AND RECOMMENDATIONS
m
iv
vii
vii
viii
1
Section 2. THE VERMICOMPOSTING PROCESS
Purpose of Study
Background
Definition of Vermicomposting
History of Vermicomposting
Current Status
Biological Information
Earthworm Species Used in Vermicomposting
Conditions of Culture
Physical and Chemical Changes During Vermi-
composting
5
5
5
5
6
8
8
8
12
14
Section 3. FACILITIES REQUIRED FOR VERMICOMPOSTING
Results of Ogden, Utah»Vermicomposting Pilot Program
Selected Facility Capacity
Design Criteria and Materials Balance
Description of Preprocessing Facilities
Description of Storage Facilities
Description of Vermicomposting and Residue
Disposal Facilities
Section 4. ECONOMICS OF VERMICOMPOSTING
Basis of Costs
Costs of Vermicomposting
15
15
18
19
21
23
23
26
26
26
-------
Preprocessing Costs
Vermicomposting Costs
Residue Disposal Costs
Potential Product Revenues
Total Vermicomposting Costs
Comparison with Alternative Methods of Municipal
Solid Waste Management
Landfill Disposal
Combustion in Modular Combustion Units
Windrow Composting
„ Summary of Alternatives1 Costs
Economics of Vermicomposting a Portion of the
Wastes of a 1,200-tpd RDF Facility
26
28
28
31
33
33
33
33
36
38
39
Section 5. VERMICOMPOSTING PRODUCTS AND PRODUCT MARKETING
Introduction
Worms Castings as a Product
Agricultural Value
Anticipated Market Development
Earthworms as a Product
Recreational Market
Inoculation of Soils
Fertilizer or Soil Supplement
Worm Stock for Vermiculturists
Animal Feed or Human Nutrition
Market Prospects
42
42
42
43
43
45
45
46
46
47
48
50
Section 6. ENVIRONMENTAL AND PUBLIC HEALTH ASPECTS OF VERMI-
COMPOSTING
Potential On-Site Problems
Site Runoff and Leachate
Disease Vectors
Safety
Odors
Potential Risks in Dispersal of Products
Toxic Substances and Heavy Metals
Pathogens
Summary
REFERENCES
vt
51
51
51
52
52
52
53
53
54
55
56
-------
TABLES
Number Page
1 Biological Data on Four Species of Lumbricid Worms 11
2 Costs of Preprocessing for a 100-tpd Vermicomposting
Facility 27
3 Costs of Vermicomposting for a 100-tpd Vermicomposting
Facility 29
4 Costs of Residue Disposal for a 100-tpd Vermicomposting
Facility 30
5 Total Costs of Vermicomposting Municipal Solid Wastes
for a 100-tpd Facility 32
6 Costs of Landfill ing Municipal Solid Wastes for a
100-tpd Facility 34
7 Costs of Combustion of Municipal Solid Wastes in Modular
Combustion Units (MCUs) for a 100-tpd Facility 35
8 Costs of Windrow Composting for a 100-tpd Facility 37
9 Cost Difference for Diverting 100 tpd to Vermicomposting
from a 1200-tpd RDF Facility 40
10 Composition of Eisenia foetida 48
11 Ami no Acid Analyses of High-Protein Meals 49
FIGURES
Number Page
1 Ogden, Utah, Vermicomposting pilot facility 16
2 Rotary screening device 16
3 ' Solid waste residue ^
4 Vermicomposting materials balance 20
5 Vermicomposting materials balance 2^
6 Vermicomposting facilities 22
vii
-------
ACKNOWLEDGMENTS
The "Compendium of Solid Waste Management by Vermicomposting" was pre-
pared under the direction of Mr. Paul W. Prendiville, officer-in-charge,
and Dr. Albert B. Pincince, project manager. Principal investigators
were Mr. John F- Donovan (project engineer), Mr. John E. Bates, Mr. Ira
D. Cohen, Mr. Thomas A. Duffield, and Mr. David F. Young.
EPA project officer was Ms. Laura A. Ringenbach, who provided valuable
direction and guidance.
viii
-------
SECTION 1
EXECUTIVE SUMMARY AND RECOMMENDATIONS
This report provides an engineering and scientific assessment of munici-
pal solid waste management by vermicomposting. The study was carried out
as a work effort (WE-1) under Contract No. 68-03-2803, U.S. Environmental
Protection Agency, Municipal Environmental Research Laboratory. The
investigation combined review of pertinent technical and non-technical
(both domestic and foreign) literature, written and telephone contact
with representatives of the vermiculture industry and researchers in the
field, and visits to Ogden, Utah, where vermicomposting is being pilot
tested, and the State University of New York in Syracuse, where research
on vermicomposting is being conducted.
Vermicomposting is the conversion of the biodegradable portion of munici-
pal solid wastes by earthworm consumption. Some species of earthworms
(Eisenia foetida and Lumbricus rubellus) can consume these wastes and
expel the remains as castings. The castings have properties that make
them a desirable soil amendment.
Vermicomposting of municipal solid wastes has been attempted only in the
last five years. While there are currently no full-scale municipal or
private operations, vermicomposting of other wastes (e.g., sludge, dairy
manure, and food processing wastes) is being carried out successfully at
several installations. This report focuses only on the vermicomposting
of municipal solid wastes.
At Ogden, Utah, vermicomposting has been tested on approximately 10 tons
of shredded wastes, from which ferrous metals had been removed. The
wastes were placed in shallow windrows covering about 800 sq ft,
moistened, and allowed to compost for a few weeks. Earthworms were then
added at a rate of about 1.5 to 2.0 Ib/sq ft. During the next month,
additional wastes were added on top of the windrows; in all, the wastes
remained in the windrows for about a four-month period, with a calculated
area loading rate of approximately four tons of waste per acre per day.
During this time some of the material was converted by the earthworms to
castings. A screen was used to separate earthworms from castings and
residue, with the intention of using recovered earthworms as stock for
any new windrows, using castings as soils amendment, and landfilling the
residue. Out of a given weight of municipal solid waste received,
approximately one-third is converted to castings.
-------
Based on the results in Ogden, we analyzed the measures required to
upgrade and expand the operation to full-scale, and to develop operating
parameters and probable costs for the full-scale operation. The full-
scale facilities analyzed would process wastes from, respectively, a com-
munity of about 50,000 residents, generating 100 tpd of solid waste, and
a community of about 500,000, generating 1,200 tpd of solid waste.
The 50,000-person community is intended to be representative of all com-
munities up to that size. Since facilities for smaller communities would
require similar equipment -- but without the economies of scale obtained
at the 50,000-person level -- it is safe to assume that if vermicom-
posting were found uneconomical for facilities serving a 50,000-person
community, it would be uneconomical also for facilities in an operation
of smaller sca-le. Comparable waste-management alternatives for a com-
munity of 50,000 would include landfill ing, combustion in modular com-
bustion units (MCUs) with sale of the steam produced in MCU boilers, and
windrow composting.
Facilities for vermicomposting in the 50,000-person community would con-
sist of equipment and structures for preprocessing the solid wastes, ver-
mi compost ing, and residual disposal. Components of preprocessing would
include a receiving area, a primary shredder capable of reducing particle
size to a nominal 4 to 6 inches, equipment for magnetic ferrous separa-
tion, and storage facilities.
For the facility serving a population of 50,000, costs and land require-
ments of vermicomposting and comparable processes are as follows:
Area Required for
20-year Project
Cost per Ton ($) (acres)
Vermicomposting 24 to 32 63
Windrow Composting 24 to 28 61
Modular Combustion Units 15 20
Landfill ing 6 112
These costs and area requirements indicate that vermicomposting is far
costlier than the land-intensive practice of landfill disposal.
Vermicomposting requires considerably more land (including 38 acres of a
sanitary landfill) and is more expensive than combustion of solid waste
with energy recovery in MCUs. Costs and land area requirements of ver-
micomposting and windrow composting are very similar. Since availability
of land and total process costs are central considerations in selecting
among solid-waste management alternatives, the typical community of
50,000 residents has available to it technologies which are more attrac-
tive than vermicomposting.
For the community of 500,000 persons, representing a major metropolitan
area, it was assumed that vermicomposting techniques would be applied to
only 100 tpd of the total 1,200-tpd waste stream. The remainder of the
wastes would be processed and burned to produce steam and electricity.
-------
In this case, because the vermicomposting operation would receive
shredded wastes with ferrous metals removed, only facilities for ver-
micomposting and residue disposal would be required.
Vermicomposting a portion of the 1,200-tpd waste steam would be more
expensive than other alternatives available to a municipality of 500,000.
Production and combustion of RDF, combined with vermicomposting, would
cost about $450,000 more annually than production and combustion of RDF
alone; the increased cost is due primarily to loss of revenues from sale
of steam and electricity.
Vermicomposting shares with other solid-waste management alternatives the
structural and operating constraints imposed to avoid contamination of
surface waters and groundwater by uncontrolled runoff and leachate, to
secure against disease vectors, and to control odors.
Vermicomposting cannot claim an established or projected market for its
products -- worms and worm castings. Worms used in Vermicomposting do
not make ideal baitworms for sportfishing, and this constitutes the sole
recognized market for worms. Castings, while apparently a useful soil
amendment with attractive aesthetic and handling properties, are produced
in quantity by vermiculturists who serve established, but highly
limited, speciality markets. Also, any product obtained through ver-
micomposting of municipal solid waste could potentially be restricted by
public-health considerations. Although public health concerns have not
been documented, any pathogenic organisms and toxics wastes in the muni-
cipal solid waste consumed by the earthworms will be present in the
castings. Further research is required in this area, and in the area of
Vermicomposting of more readily degradable wastes -- such as certain
types of agricultural and industrial wastes and municipal wastewater
sludges — that do not require expensive preprocessing before the ver-
mi compost ing process is begun.
Municipal solid waste Vermicomposting has apparent advantages and disad-
vantages over other waste management methods. Some of the advantages
are:
o Recovery and recycling of the organic fraction of solid waste as
earthworm castings.
o Reduced land area requirements for processing and disposal com-
pared to the commonly used sanitary landfill operation.
Some of the major disadvantages-are:
o Expensive shredding of wastes required before Vermicomposting.
o High capital and operating costs compared to other available
methods.
-------
o An unknown market for the earthworm castings.
o Potential public health and environmental concerns in dispersal of
castings.
-------
SECTION 2
THE VERMICOMPOSTING PROCESS
PURPOSE OF STUDY
This "Compendium on Solid Waste Management by Vermicomposting" is an
engineering and scientific feasibility study of vermicomposting as a
means of converting municipal refuse to a usable soils amendment. The
report contains:
o Discussion of the state-of-the-art of vermicomposting of municipal
solid waste
o Engineering analysis of the technical and economic aspects of
vermicomposting
o Recommendations as to the applicability of vermicomposting to pre-
sent and future solid waste management needs.
Work was carried out as a work effort (WE-1) under Contract No. 68-03-
2803, U.S. Environmental Protection Agency (EPA), Office of Research and
Development, Municipal Environmental Research Laboratory. Under the same
contract a similar study was conducted on vermicomposting of municipal
wastewater sludge (1).
The investigation combined review of pertinent technical and nontechnical
literature, extensive written and telephone contact with numerous repre-
sentatives of the vermiculture industry and researchers in the field, and
a visit to a site where vermicomposting research is being conducted.
Literature references were obtained through contacts with individuals
working in the field, as well as through a computer-based literature
search of related entries in the following data bases: AGRICOLA, BIOSIS
PREVIEWS, COMPENDEX, EPB, NTIS, POLLUTION ABSTRACTS, and SSIE CURRENT
RESEARCH.
BACKGROUND
Definition of Vermicomposting
Vermicomposting is the degradation of organic wastes by earthworm con-
sumption. Some species of earthworm (Eisenia foetida and Lumbricus
rebellus) thrive in managed conditions on a diet and substrate composed
almost entirely of organic matter. They feed on the wastes, consume a
-------
portion of the organic matter and expel the remains as feces, or
castings. If conditions are suitable, they will multiply. There is
insufficient information to warrant speculation on whether the worms will
increase or decrease in number when degrading solid wastes, however.
A portion of the wastes is usually not biodegradable and simply remains
after processing as residue for disposal. Municipal solid wastes contain
a high percentage of wastes that cannot be consumed by earthworms. The
ratio of wastes that cannot be converted to castings would decrease if
municipal wastes were separated at the source.
This report focuses on wastes normally collected by a municipality
without a source'separation program.
After the worms have fed on the waste and converted it into castings,
they are usually separated from the castings. Worms can be recycled into
new vermicomposting beds or, possibly, marketed in some form. Castings,
once dried, have properties which might make them a desirable soils
amendment. The end products of vermicomposting, therefore, are worms,
castings, and solid-waste residue.
History of Vermicomposting
The role of earthworms in nature has been recognized since ancient times
and was studied extensively by the biologist Charles Darwin in the late
19th century. Despite this awareness, and despite the fact that success-
ful culture of earthworms need involve no new technology, the practices
of raising worms (vermiculture) and using them for waste management
(vermicomposting) have not been advanced until recently.
There are now numerous individuals, gardeners and entrepreneurs raising
worms in a soil/peat/manure bedding in indoor bins or outdoor plots; most
of those practicing vermiculture depend heavily on the baitworm market to
realize some income from the business.
Only since 1970 has the vermicomposting of wastes (including municipal
solid waste) been attempted at any more than barnyard scale. Pioneering
efforts commonly mentioned in the literature (2, 3) include a demonstra-
tion project at Hollands Landing, Ontario (Canada), which was begun in
1970 and has since been operated under private ownership. A pilot-scale,
one-time demonstration of vermicomposting municipal solid waste (MSW),
was conducted in 1975 at Ontario, California. Neither operation was con-
ducted under the controlled conditions that would yield reliable engi-
neering design parameters. The Hollands Landing facility has
vermicompasted small amounts of manure, food-processing wastes, and
sludge (Klauck, personal communication); the Ontario, California, project
involved the vermicomposting of municipal refuse in a program jointly
conducted by the City and North American Bait Farms Inc. The short dura-
tion project involved a total of 10 tons of mixed municipal refuse, which
was hand-picked to remove glass, metal, plastics, and rubber. The
remaining 9 tons were windrowed adjacent to established earthworm beds at
-------
a wormbreeding farm. Reportedly, consumption of organics was 90-percent
complete in 68 days. Only castings, bulky materials such as tree limbs,
and inorganic residues remained.
In a later experiment at the same facility, a shredded and air-classified
organic fraction of municipal solid waste was transported from a local
resource-recovery facility. Reportedly, consumption of the wastes was
faster and more complete than in the earlier experiments, even though the
process was hampered by large quantities of plastic present in the waste
and by very dry conditions resulting from the windrow's direct exposure
to sunlight. No documentation is available on the amount of castings
produced during the Ontario tests or their ultimate use.
Another demonstration of solid-waste vermicomposting was carried out in
1978-79 by the American Earthworm Company (AEC) in Florida (Wesley
Logue, personal communication). This project involved vermicomposting,
over a 12- to 18-month period, about 500 tons of municipal solid
waste. Wastes were trucked to a 1-acre vermicomposting facility in
Sanford, Florida, where cans, large objects, and newsprint were removed
by hand. The remainder was fed to a hammermill shredder, which reduced
the wastes to a 3-in particle size. The shredded waste was placed in
windrows about 6 in deep, which were irrigated to increase moisture.
Moisture levels achieved and other pertinent data are not known. AEC
used approximately one tone of earthworms in the vermicomposting opera-
tion. Reportedly, some of the finished castings, which contained glass,
were utilized by a local nursery. The facility is no longer in opera-
tion.
Other work has been carried out in Japan, where some pulp and food pro-
cessing industrialists have turned to vermicomposting techniques for
management of sludges and waste byproducts (4). Information was obtained
through two sources in the vermiculture industry: AOKA SANGYO CO, LTD
and TOYOHIRA SEIDEN K06YO CO. The AOKA SANGYO CO. reports they have
three 1,000-ton-per-month plants processing wastes from pulp and food
processing companies (Shizuro Aobuchi, personal communication). The
operation appears to be labor-intensive, and the economics appear to
depend heavily on disposal fees paid by the industry. Reportedly about
400 tons of casting and 10 tons of earthworms are produced per month.
The earthworms are freeze-dried and sold as fish feed. Worm castings are
also sold.
The TOYOHIRA SEIDEN KOGYO CO. reports that rice plant straw, municipal
sludge, 'sawdust, paper-making wastes, food-processing wastes and manure
are vermicomposted (Katsumi Yamaguchi, personal communication). They
estimate that about 20 private companies with monthly capacities of 2,000
to 3,000 tons are in operation. An additional 3,000 individuals may be
vermicomposting 5 to 50 tons of wastes per month. However, these esti-
mates are only approximate as the enterprises are not well-organized.
In Europe, no commercial-scale vermicomposting operations have been
reported in the literature. A demonstration facility was recently
established in Modena, Italy, however (Carla Chiesi, personal
-------
communication). Reportedly, a screened and composted municipal refuse is
fed to Eisena foetida. In several other European countries, university
laboratory research in waste vermicomposting is underway (5) (6).
Current Status
There is currently only one facility vermicomposting municipal solid
wastes alone. That facility, in Ogden, Utah, at the Weber County Refuse
Disposal Facility, is operated by Teledyne National, with Roger E. Gaddie
of Annelidic Consumption Systems, Inc. (ASC) acting as a consultant on
vermicomposting.
In August 1979, the vermicomposting of a small portion of the County's
shredded wastes was begun. Some 23 tons of wastes were processed during
the next several months. A description of the operation, including an
estimate of waste-conversion rates and feasibility is presented in Section 3.
A vermicomposting operation in Ridgefield, Washington has used dairy
manure, cannery wastes, paper mill sludge, municipal wastewater sludge
and municipal refuse (I). The facility, operated by American Organic
Farms, Inc., has recently received an experimental permit from the local
Health Department to vermicompost the light fraction of source-separated
garbage from a voluntary residential cross-section of Clark County,
Washington. The material is ground when received on site and distributed
on windrows which are also receiving liquid sewage sludge.
BIOLOGICAL INFORMATION
Earthworm Species Used in Vermicomposting
Only two species of earthworms -- Eisenia foetida and Lumbricus rubellus
-- are commonly mentioned in the literature as suitable for use in waste-
vermicomposting operations. Researchers have focused almost exclusively
on the vermicomposting performance of these two species, which often
share the common name of red worm. Other species have reportedly been
utilized in pilot-scale studies, including Lumbricus terrestris (7) —
the nightcrawler -- and Allolobpphora calignosa (2) -- the field worm,
and these same species often will invade the lower reaches of composting
windrows (8), but comparative discussions of their survival and perfor-
mance in vermicomposting are not available. Recently, some interest has
been shown in the so-called "African nightcrawler," Eudrilus eugeniae,
but this worm requires near-tropical conditions of culture, and its per-
formance in vermicomposting has been explored only in laboratory-scale
studies (9, 10).
Not surprisingly, the two worms which appear best suited to the con-
ditions of culture in vermicomposting occur in nature in enriched organic
substrates. Both are small- to mid-sized earthworms classified by biolo-
8
-------
gists among the lumbricids (Family Lumbricidae). They are pigmented
surface-dwellers, found in nature in the upper 8 cm of the soil surface.
Their surface-dwelling habit is not a coincidence: in nature, fresh
organic matter is concentrated in the upper soil layers.
The distribution of E. foetida and L. rubellus in nature tends to be
highly localized, as opposed to the widespread distribution of larger
earthworm species that inhabit stable agricultural lands, fields, and
woods. The "vermicomposting species" cannot thrive in unenriched
environments; they require concentrations of organic matter. Conversely,
the larger "agricultural species" -- such as the nightcrawler and field
worm -- breed more slowly, adjust poorly to the managed conditions of ver-
micomposting, and cannot tolerate the temperature increases which can
accompany bacterial decomposition of organic matter (8).
E. foetida is commonly known as the brandling worm (also red worm, red
wiggler, manure worm, red-gold hybrid (8)). A relatively small worm of
4 to 8 mm diameter and 100 mm in length (8, 11), it is found in nature only
in areas of high organic concentration -- in decaying logs, compost heaps,
dung heaps. The brandling worm cannot, in fact, survive for long in
average soils containing a greater proportion of mineral matter.
Two other characteristics distinguish E. foetida from most other earth-
worm species. E. foetida can tolerate somewhat higher temperatures than
can most of the subsurface, burrowing species (12). This enables E.
foetida to survive and feed in a compost heap sooner after the completion
of its active, heating phase than can the other species (except L.
rubellus). E. foetida is also more prolific than most other worms; it is
the only cultivated species known to produce, on the average, more than
one viable offspring per egg capsule (or cocoon).
L. rubellus (red worm, red wiggler, hybrid red worm, English red, Georgia
red, California red) is similar in habit to E. foetida; it is found
naturally in stream banks, organic leaf litter, and under dung pats in
agricultural fields. Like E. foetida, this red worm breeds rapidly and
has a relatively short development time to sexual maturity. Both L.
rubel1 us and E. foetida can be found through all levels of a stabilized
compost heap, whereas larger agricultural species are generally found
only in the lower parts of the heap.
Table 1 presents vital biological data on E. foetida and L. rubellus,
along with data on two non-vermicomposting species, L. terrestris and
A. caliginosa, for comparative purposes. (From this point on in the
report, references to "earthworms" should be taken to mean E. foetida and
L. rubellus, unless otherwise specified.)
It is evident, from the table, that data gaps exist in some areas and
that conflicts in data obscure true values in others. Some of the data
conflicts can undoubtedly be attributed to differences in experimental
techniques and to the fact that some observations were obtained in the
field and others in controlled conditions favorable to growth. In the
field, the period of growth is markedly affected by conditions existing
-------
when growth began. Sound experimental techniques will one day resolve
these discrepancies and fill in other gaps in the knowledge of earthworm
biology as it applies to vermicomposting.
Like all other earthworms, E. foetida and L. rubellus are hermaphroditic,
each individual worm possessing both male and female sex organs.
Reproduction normally occurs through copulation and cross-fertilization,
following which each of the mated pair can produce cocoons (oothecae)
containing one to 20 fertilized ova. Production of cocoons and emergence
of offspring in these species are summarized in Table 1.
The resistant cocoons, tiny and roughly lemon-shaped, are usually depo-
sited near the surface of the ground, except in dry weather when they are
left at deepen levels. After an incubation period that varies with cli-
matic conditions, the cocoons hatch. Young earthworms, white and only a
few millimeters in length on emerging from a cocoon, gain their adult
pigmentation within a day. Assuming favorable conditions, they will grow
to sexual maturity within several weeks of emergence, although much
depends on temperature, season, and conditions of culture.
Mature individuals are easily distinguished by the presence of a cli-
tellum, the pale- or dark-colored swollen band, somewhat behind the geni-
tal pores. (The clitellum secretes the fibrous cocoon, and clitellar
gland cells produce a nutritive albuminous fluid contained in this
cocoon.) The worms usually continue to grow in size for several months
after completing their sexual development.
Cocoon production, development and growth are much affected by seasonal
climatic conditions. Cocoon production for L. rubellus, for example, is
greatest in the months from June through September (8), and falls off
directly with decreasing soil temperatures (we have not seen any
discussion on whether it may also reflect an endogenous rhythm).
Although, theoretically, earthworms living in controlled conditions might
be capable of extremely high rates of population growth -- with popula-
tion doubling times of only a few days (13) — most vermiculturists
assume population doubling times of 60 to 90 days (8, 14). It is not
known what generation times can be expected under the controlled, but
periodically disturbed, conditions of vermicomposting.
In temperate zones, the seasons of greatest developmental activity are
the spring and fall. Earthworms will enter a quiescent state (or
diapause) when conditions are hot and dry, or very cold. Under such con-
ditions, production of cocoons is ceased, and worm growth and development
are slowed. Cold weather also lengthens the incubation period for
cocoons. Cocoons produced during cold-weather months generally will not
hatch until spring. Relatively little earthworm growth occurs in summer
and winter, and individuals that emerge from cocoons in the height of
summer can take up to twice as long to reach full development as those
that emerge in autumn or spring.
10
-------
Table 1
BIOLOGICAL DATA ON FOUR SPECIES OF LUMBRICID WORMS
Vermi composting Species
Characteristic
Common name
Eisenia foetlda
. Brandling worm (red worm,
Lumbricus rubellus
. Red worm
Non-Verm1compost1ng Species
Lumbricus terrestrls
. Night crawler
Allolobophora callglnosa
. Field worm
Color
Size of adult worms
Height
No. of cocoons/year
manure worm)
. Brown and buff bands
. 4-8 mm diameter,
50-100 mm length
: 2-3 mg at hatching
, 0.4 g average adult
. Up to 2.4 g in controlled
conditions
. 11 (field conditions)
. Up to 100 1n controlled
conditions
Reddish brown
4 mm diameter,
70-150 mm length
79-106
Brown violet
8 mm diameter,
80-300 mm length
Average 5.0 g
Low
Rose or brown red
4 mm diameter,
40-200 mm length
. 27
Size of cocoons
Incubation period
No. of worms hatched/
cocoon
Development to
maturity
Llfespan
. 3.87 mm x 3.17 mm
. 3 weeks (25°C)
. 11 weeks (field)
. 1.6 - 3.6 mean, varied
seasonally
. Average of 2.6 (and up to
6) among those that hatched--
21.5* did not hatch
. 5-9 weeks (under controlled .
conditions, 18-28°C)
. 47-74 weeks (field)
. 4-1/2 years (protected)
3.18 mm x 2.76 mm
16 weeks (field)
Usually 1-2
37 weeks (field)
*
. 5.97 mm x 4.69 mm
*
. Usually 1-2
. 52 weeks (field)
. 6 years (protected)
*
. 19 weeks
. Usually
. 55 weeks
. Long
1-2
(field)
^Information not found
-------
In general, conditions of heat and drought are more dangerous to earth-
worms than those of wet and cold. For example, some worms have been
shown to survive weeks of immersion in water, provided the water is kept
aerated. Cocoons, however, can survive extremes of hot and cold within
the range of normal climatic conditions.
In the field, average lifespans of £. foetida range from one to three years
(11). E_. foetida reportedly have lived for more than four years in con-
trolled laboratory conditions. Among possible natural hazards, in addi-
tion to temperature and moisture extremes, are internal parasites (some
microorganisms, platyhelminth worms, rotifers, nematodes and fly larvae)
and predators (many birds, badgers, hedgehogs, moles, some snakes, cer-
tain beetles and their larvae, centipedes, and a few species each of car-
nivorous slugs, leeches and flatworms). In a municipal solid waste vermi-
composting facility in Sanford, Florida, birds were found to be a problem
(Wesley Logue, personal communication). But at the facility visited dur-
ing this study (Ogden, Utah), there was not a predator problem.
Conditions of Culture
While details on the biology of earthworms seem scant or somewhat contra-
dictory, the practical experience of worm breeders, worm farmers, and
researchers has built a relatively consistent body of information on
optimum conditions for supporting a worm population.
Temperatures --
Worms exhibit a fairly complex response to changes in temperature. In
general, conditions that promote the most rapid feeding and conversion of
waste to castings are found in the temperature range of 13°C to 22°C,
averaged from results obtained by most workers. Both JE. foetida and L_.
rubellus will prefer substrate temperatures within this moderate range,
but the upper limit of temperature preference is somewhat lower for L
rubel1 us at 18°C. These moderate temperatures represent practical cri-
teria for design and operation of vermicomposting systems.
At soil temperatures below 10°C, worms' feeding activity is described as
greatly-reduced to nonexistent (7); below 4°C, production of cocoons and
development of young earthworms cease (11), Worms will tend to hibernate
and migrate to deeper layers of the windrow or into the soil for protec-
tion. Worms can become acclimated during the fall months to the temper-
atures they will encounter at deeper substrate levels in the winter, but
they cannot survive in freezing temperatures.
At temperatures above the optimum range, up to 25°C to 27°C, the worms' per-
formance depends in part on their acclimation to the higher temperatures.
Worms raised from hatching to adulthood under controlled conditions at 25°C
have been shown to feed and grow well, and to develop and reproduce at rates
faster than worms raised at lower temperatures or in the field (8, 15).
For worms not acclimated to higher temperatures, activity is significantly
reduced at 25°C, and there may be loss-of-weight and mortality (7, 16).
12
-------
The unfavorable effect on worms of high (25°C and above) temperatures is
not entirely a direct effect. Warm temperatures also support accelerated
chemical and microbial activities in the substrate; the increased micro-
bial activity tends to use up available oxygen, to the worm's detriment
(7). These temperature studies were conducted mostly with sludge as feed;
none were conducted with municipal solid waste.
pH -
Earthworms generally prefer neutral soils (2), and both E_. foetida and _L.
rubellus find their optimum environment at pH 7.0 to 8.0, neutral to
mildly alkaline (8). Worms will avoid acid soils of pH less than 4.5,
and prolonged exposure to such soils acts as a violent contact poison
with lethal effects (11).
Minor increases in acidity caused by addition of fresh wastes to the vermi-
composting bed will be neutralized by the worms' intestinal secretions and
excreted ammonia (11). Operators can also control acidity by adding lime
(17) or limestone flour (13), as necessary.
Moisture Content --
In nature, the greatest number of worms will be found in the soils of 12 to
30 percent moisture (8). In vermicomposting, the optimum range of moisture
content has been reported at 50 to 90 percent. Above 80 percent moisture,
conditions of poor oxygen transfer might interfere with the worms' feeding.
Municipal solid waste has a moisture content ranging from 20 to 40 per-
cent. Periodic irrigation is required to increase the moisture content.
The worms' feeding rate apparently is independent of moisture content, as
long as a threshold value of moisture (50 percent) is present (18).
Aeration --
Earthworms have no specialized respiratory organs; oxygen diffuses in
through skin layers of the body wall, and carbon dioxide diffuses out.
Earthworms are sensitive to anaerobic conditions. Their respiration rates
are depressed in the presence of low oxygen concentrations — by 55 to 65
percent, for example, in the presence of oxygen at one-fourth its normal
partial pressure (11). Feeding activity might be reduced under these sub-
optimal conditions (15). E_. foetida have been reported to migrate en masse
from a water-saturated substrate in which oxygen is being depleted, or in
which carbon dioxide or hydrogen sulfide is accumulating. The situation
is made'more critical by oxygen requirements that may increase by a factor
of 10 as temperatures increase from 9°C to 27°C (11).
In the vermicomposting operation, aeration requirements can be met by (1)
mechanically turning or tilling the beds at regular intervals, (2) maxi-
mizing surface area in the piles by keeping the windrows shallow, (3)
protecting against bed saturation by enclosing the vermicomposting fa-
cility, and (4) maintaining temperatures within the optimum range for feed-
13
-------
ing by heating or cooling enclosed facilities. Some researchers argue
against mechanical turning, both because it can cause trauma to the worms
and because it can redisperse castings into the substrate, which may pro-
duce toxic effects in the worms (15).
Nitrogen and Other Substrate Minerals --
Earthworms reportedly thrive in a medium of 9 to 15 percent protein (17).
Fresh bovine feces contain about 14 to 15 percent protein (17), sludge can
vary from 12 to 38 percent protein, and unsorted mixed municipal refuse
might contain only about 4 percent protein, depending on sources (19). A
low to moderate carbon-to-nitrogen (C:N) ratio is considered desirable,
with worms showing maximal weight gain in the C:N range of 15:1 to 35:1
(20). Only the most biodegradable fractions of municipal solid waste —
such as yard wastes and food wastes -- fall into this optimum range; un-
sorted mixed municipal refuse will have a C:N ratio on the order of 50:1
(19).
At Johnson City, Tennessee, refuse with an initial C:N ratio of between 40
and 50 was reduced to between 28 and 35 during six weeks of composting (21).
The vermicomposting operation envisioned in this report allows for com-
posting of several weeks' duration prior to the addition of earthworms.
Therefore, the vermicomposting operator should be testing for the C:N ratio
of the wastes and make an attempt to keep the ratio low. "One possible
method is the addition of a nitrogen source such as sludge or manure to the
solid waste.
PHYSICAL AND CHEMICAL CHANGES DURING VERMICOMPOSTING
As the worms eat and digest waste, they expel the digested material as
castings. The large particles and irregular shapes of wastes are reduced
by the worms to much smaller particles of relatively uniform shape and
size.
In fact, when dry, castings have the appearance of sand pebbles of roughly
oblong shape, with approximate dimensions of 0.55 mm in diameter and
1.00 mm in length (22). Their odor is that of fresh earth or compost and
is not noticeable unless an effort is made to smell the castings close up.
Worms secrete a mucus membrane around the castings (15). It is theorized
that the membrane might serve to protect the worms from their own feces;
castings are generally toxic to the species of worm which produces them.
An additional benefit of the membrane formation process might be that
castings are kept separate from each other, thereby increasing the exposure
of the castings; surfaces to air.
14
-------
SECTION 3
FACILITIES REQUIRED FOR VERMICOMPOSTING
RESULTS OF OGDEN, UTAH, VERMICOMPOSTING PILOT PROGRAM
As noted in Section 2, the vermicomposting pilot facility being operated
at the Weber County Refuse Disposal Facility in Ogden, Utah, by Annelidic
Consumption Systems, Inc., is the only currently operating vermicom-
posting facility in the United States exclusively utilizing municipal
solid waste.
At the Weber County Refuse Disposal Facility, which is operated by
Teledyne National, about 350 tpd of mixed, residential and commercial
wastes are burned. Before combustion, the wastes are shredded to a nomi-
nal size of 6 to 8 in., and ferrous metals are removed by a magnetic
pulley.
In early August 1979, operators at the Weber County Facility used front-
end loaders to transfer approximately 47 cubic yards of shredded waste to
three windrows in an area prepared for a sanitary landfill operation
(Figure 1). Based on a field measured density of approximately 240 Ib/cu
yd, about 5.6 tons of wastes were windrowed. The windrows, each
measuring 20 to 35 ft long and about 9 ft wide, were spaced 10 ft apart.
The maximum depth of each windrow was approximately 3 ft. The windrows
were watered to increase the moisture content.
After several days, temperatures began to increase in the windrows due to
bacterial breakdown of organic matter (composting). If composting had been
carried out properly, temperatures of 50° to 60°C should have been
attained. The elevated temperatures continued through 27 August; windrow
temperatures on that day were measured at about 32°C. During this period
it is unlikely that aerobic thermophilic composting was achieved.
Apparently, temperatures in the windrows would have dropped more rapidly
had the'wastes been kept sufficiently moist by facility operators. Once
windrows were wet down on 27 August, temperatures dropped to 24°C — within
the range at which vermicomposting can begin. At this point, some 1,450 Ib
of earthworms were applied to the windrows. The worms reportedly infil-
trated the windrows within a day.
On three occasions during the next 35-day period, 1-ft increments of
shredded and unshredded wastes were added to the top of each windrow.
About 36 cu yd (4.4 tons) were added during this period; in all, a total
of 83 cu yd (and 10 tons) of solid wastes were vermicomposted. For the
next 2 1/2 months, the earthworms converted the wastes to castings.
15
-------
Figure 1. (left) Ogden, Utah, vermlcompost-
ing pilot facility
Figure 2. (left) Rotary screening device
Figure 3. (above) Solid waste residue
-------
On 31 October 1979, four additional windrows were constructed between
existing windrows. The new windrows contained about 13 tons of solid
wastes and occupied about 1,050 sq ft. No new earthworms were added to
these windrows. Some of the earthworms migrated from the first three
windrows to the second set of windrows in search of more attractive food
sources.
COM engineers were on-site when facility workers began harvesting por-
tions of the first three windrows on 14 December 1979, 100 days after
earthworms were first added and about 130 days after wastes were first
windrowed. In the judgment of Ronald E. Gaddie of Annelidic Consumption
Systems, Inc., 90 percent of the wastes had been converted at this point.
Based on the screening results obtained later, however, a much lower per-
centage had been converted.
Harvesting was accomplished using an inclined cylindrical, rotating
screen driven by a small motor, a type of device commonly used in ver-
miculture (Figure 2). In normal operation, this type of screen sepa-
rates castings (which fall through the screen) from earthworms and residual
solid waste (which travel the length of the screen and are discharged).
Because of the large amount of plastic in the waste stream, however, and
perhaps because not all wastes had been shredded properly prior to
windrowing, the harvesting screen did not work very well. It was
apparent that less than 50 percent of the material fed to the device was
screened out as castings. Most of the material either had to be removed
by hand from the front of the machine, which clogged repeatedly, or was
discharged through the length of the harvester as residue. Very few
earthworms were separated. Figures 2 also shows the castings recovered
and the residue discharged. Figure 3 is a closeup of the discharge end of
the screen.
To determine the physical facilities required for composting, COM esti-
mated the rate of waste conversion at the Ogden pilot facility. In the
literature, estimates of worms' performance in vermicomposting vary
widely. Entrepreneurs working in the vermiculture industry routinely
report that worms will consume one-half to twice their weight in waste each
day. To provide a rational basis for the design of facilities, we calcu-
lated a consumption rate based on the experience at Ogden.
At-Ogden, 10 tons of wastes were processed during a 110-day period using
1,450 Ib of earthworms. This time does not include 3 weeks of thermophilic
composting prior to the introduction of earthworms, even though this preli-
minary composting is essential in order to maintain optimum temperatures
during vermicomposting. The calculated conversion rate of vermicomposting
at Ogden is, therefore, about 0.13 Ib waste processed/lb of earthworms per
day.
Area requirements for vermicomposting are determined from the ratio of the
weight of earthworms utilized per unit of area. At Ogden, 1,450 Ib of
earthworms were applied to about 800 ft of windrows. The resulting ratio
of 1.8 Ib/sq ft compares with ratios used in vermicomposting of wastewater
sludge (0.4 to 2.3 Ib/sq ft).
17
-------
Based on the conversion rate (0.13 Ib wastes/lb earthworms per day) and
area requirements (1.8 Ib earthworms/sq ft of wastes) observed at Ogden, a
loading rate of 0.23 Ib/sq ft per day is calculated. Stated another way,
each ton/day of waste requires about 0.2 acre, plus about 20 percent to
allow for composting before worm addition. In practice, earthworms would
be added to an initial set of windrows. After 130 days, new windrows would
be constructed between the existing windrows. This allows the earthworms
originally added to the first set to migrate to the second set of windrows.
Then the initial set of windrows are removed and screened. In this way,
the land is used in 130-day cycles and earthworms are reused.
ACS speculates that under more favorable climatic conditions, and/or with
an earthworm that is acclimated to solid wastes, only 70 days would be
required for conversion (Gaddie, personal communication). If this were so,
only 0.13 acre would be required for each ton/day of municipal wastes.
Additional research could establish the time required for conversion under
various loading and climatic conditions.
SELECTED FACILITY CAPACITY
For this report, COM examined a hypothetical small facility and large
facility. The small facility was defined as one receiving 100 tons per
day of wastes, 6 days per week, representing the total mixed residen-
tial and commercial wastes of a municipality of about 50,000 persons.
Bulky items such as "white goods" (large household appliances) and demo-
lition wastes would be managed by separate collection. For a facility of
this size, three other candidate waste processing techniques would be (1)
sanitary landfill, (2) incineration of wastes in a modular combustion
unit (MCU), a technique becoming economically attractive for small- and
medium-sized communities with a large and stable market for the recovered
energy and (3) windrow composting.
The large facility would receive 1,200 tpd of wastes, 6 days per week,
representing residential and commercial wastes generated in a city or
metropolitan area of about one-half million persons.
Area requirements for windrows alone, in the 1,200-tpd facility, would
total 250 acres. Dedication of this much land to the vermicomposting pro-
cess is inconceivable and mechanization (for example in silos) has not been
demonstrated. In this report, therefore, it is assumed that the municipa-
lity would already have in operation a 1,200-tpd facility converting solid
waste to refuse-derived fuel (RDF) and recovering steam energy from inci-
neration of the RDF. Only a small portion (92 tpd) of the shredded wastes
would be diverted to the vermicomposting facility. This diversion would
allow for production of humus material for local use. The fact that the
necessary preprocessing would have been completed as part of an existing
processing train would be expected to make the economics of vermicomposting
as attractive as possible for a facility of this size.
18
-------
Technical criteria and costs for vermicomposting facilities serving com-
munities of population 50,000 and 500,000, respectively, are developed as
follows.
DESIGN CRITERIA AND MATERIALS BALANCE
Figure 4 presents a materials balance adapted from Gaddie for a waste
stream from which a large portion (36 percent) would have been removed
before vermicomposting. Substances removed would include paper, glass,
aluminum, ferrous metals, and other items (23). Of the 64 tpd of solid
waste to be vermicomposted, about 18 tpd would be ultimately landfilled.
Of the remaining 46 tpd, about 70 percent (33 tpd) would be converted to
castings, and 30 percent (13 tpd) would be volatilized or account for
reduction in moisture.
Figure 5 shows a materials balance for a waste stream exposed only to
processes of shredding and ferrous removal prior to vermicomposting. In
this case, approximately 92 tpd of the total received would go to ver-
micomposting. The remaining 8 tpd would consist of ferrous material recov-
ered for sale. Actual percent ferrous recoverable may range between 6
and 10 percent, depending on local waste composition and facility design
and operation. The vermicomposting facility would also receive the 92 tpd
of shredded and ferrous wastes removed from the 1,200 tpd facility.
Of the 92 tpd diverted to vermicomposting, about 31 tpd ~ including glass,
rubber and wood wastes — would be landfilled. The amount of castings pro-
duced would be 70 percent of the remaining portion, or 43 tpd. The other
30 percent (18 tpd) would be volatilized or account for reduction in
moisture.
It is important to note that none of the above estimates has been verified
at actual demonstration facilities. The rotary screening operation at
Ogden has not yielded the quantities of castings used for this report. As
noted above, however, much of the work at Ogden has been carried out at
less than optimum conditions and with some unshredded wastes present. The
materials balance is optimistic in order to provide the most favorable eco-
nomic analysis.
To determine the area required for vermicomposting, the assumptions pre-
sented in Section 2 are followed. Total residence time would be 110 days,
resulting in a loading rate of 0.23 Ib waste/sq ft per day. An additional
20 perceht is added to the area to provide space for preliminary com-
posting. For a daily average loading of 92 tpd, the windrow area require-
ment would be 22 acres; a total of 23 acres of land has been allocated for
windrowing to account for an access road.
19
-------
MOISTURE LOSS
AND
VOLATILIZED
SOLIDS
IOOT
PAPER,
GLASS,
IRON,
ETC.
FIGURE 4. VERMICOMPOSTING MATERIALS BALANCE
( BASED ON ESTIMATES DEVELOPED BYANNELIDIC CONSUMPTION SYSTEMS, INC.)
MOISTURE LOSS
AND
VOLATILIZED
SOLIDS
I >
IOOT
IRON
FIGURES. VERMICOMPOSTING MATERIALS BALANCE
20
-------
DESCRIPTION OF PREPROCESSING FACILITIES
Preprocessing facilities can be subdivided into units for receiving,
shredding, magnetic separation, and storage of solid wastes. Figure 6
shows preprocessing, vermicomposting and residue disposal facilities for
the 100-tpd facility. For the 1,200-tpd facility, separate preprocessing
would not be required and shredded wastes would be introduced directly to
the windrows.
For a 100-tpd facility, only ferrous removal and shredding could be econo-
mically justified. Aluminum recovery may or may not be justified, but its
exclusion from this analysis will not affect the cost of vermicomposting
relative to other methods. Further preprocessing, including (1) the mecha-
nical removal of glass and paper and (2) fine or secondary shredding, is
not economically feasible at a small facility. These assumptions are based
on the findings of recent solid waste management studies (24, 25, 26). The
steps of preprocessing described below apply only to the 100-tpd facility
serving a community of 50,000, because preprocessing for the 1,200-tpd RDF
facility with a 100-tpd vermicomposting side operation is completed in con-
version of the total waste stream to RDF.
Receiving --
Collection and transfer of municipal solid waste would terminate at a
receiving building, where refuse would enter the preprocessing system.
There, the transfer-haul trucks would tip their solid waste onto the floor,
where a front-end loader would stockpile it into the center of the
building. Large bulky items, such as tree stumps and white goods, would be
sorted out of the process stream by front-end loader, prior to dumping onto
conveyors. Hand-sorting could be performed during the conveyor stage to
eliminate a large portion of other unprocessable items. Refuse then would
pass into the shredder building.
Shredding --
A shredder reduces volume by about 50 to 70 percent. Depending on initial
moisture content, however, only about 7 percent of the initial weight may
be lost (27). In reducing refuse to a relatively small and uniform size,
the shredder tends to make refuse more homogeneous. This facilitates
further Dandling, sorting and processing of the wastes and, in the case of
incineration modes of disposal, produces a fuel product with more highly
predictable combustion properties. Particle size of the product could be
varied to meet the requirements of vermicomposting. A shredder would be
expected to reduce refuse to a nominal 4- to 6-inch size.
Annual maintenance costs for the shredder and building would be high in
comparison to other equipment, due in part to the relatively frequent
occurrence of damaging explosions.
21
-------
PRE-
PROCESSING
RECEIVING
SHREDDING MAGNETIC STORAGE
SEPARATION
TRANSFER
ro
ro
VERMI-
COMPOSTING
RESIDUE
DISPOSAL
WINDROWING
TRANSFER
LANDFILLING
SCREENING
FIGURES. VERMICOMPOSTING FACILITIES
-------
According to an industry report (28), significant explosions can be
expected at a solid waste shredding facility on the average of four times
per year. One of these explosions can statistically be expected to cause
major damage to the facility.
Magnetic Separation —
The magnetic properties of iron and steel make ferrous recovery one of the
easiest materials-separation processes to implement in solid-waste manage-
ment. Three basic types of magnetic separators have been used successfully
in recovering ferrous items from shredded refuse: drum magnets, single
magnet-belt separators, and multiple magnet-belt separators. These magnets
are usually suspended over the end of a conveyor which carries shredded
solid wastes. As the wastes pass by or under the magnet, ferrous metals
are picked up and thrown or diverted into a separate stream.
Magnetic separation may be accomplished at any of several different
points in a resource-recovery facility: usually following shredding but
before density/size classification. The technique can also be used to
separate potentially marketable post-incineration scrap from incinerator
residue. The specific point to perform magnetic separation and the type
of magnet used depend upon the particular market specifications, the
market location for the ferrous scrap, and requirements of other separa-
tion processes. The recovered ferrous metals may then be sold to second-
ary material markets to help offset the capital and operating costs for
processing.
DESCRIPTION OF STORAGE FACILITIES
In the smaller facility (100 tpd), the shredded product would be bunkered
in a passive, three-walled tipping floor arrangement. The waste would
then be fed to trucks by front-end loader and transported to the ver-
micomposting facility.
For the larger, 1,200-tpd RDF facility, the processed waste (RDF) would
pass from the shredder building via conveyor to a storage bin. This faci-
lity would incorporate live bottom hoppers to feed conveyors which, in
turn, would feed semi-suspension boilers or transfer-haul vehicles. Prior
to reaching the storage bin, approximately 92 tpd of processed waste would
be redirected via a reversable conveyor that would feed into trucks dedi-
cated to' hauling the processed waste to the vermicomposting facility.
The storage bin would have a 2-day storage capacity to handle the incoming
wastes during vermicomposting and/or incinerator down-time.
DESCRIPTION OF VERMICOMPOSTING AND RESIDUE DISPOSAL FACILITIES
Shredded wastes with ferrous material removed would be discharged to bunker
storage or directly to trucks destined for the vermicomposting facility.
23
-------
The 92-tpd remaining after removal of ferrous material would yield a volume
of about 900 cu yd/day at a density of approximately 200 Ib/cu yd. Wastes
would be recovered from the bunker by a 3-cu yd capacity front-end loader
and placed in a 16-cu yd capacity dump truck.
Figure 6 shows the major steps in vermicomposting: windrowing and
screening. Shredded wastes would be trucked to nearby windrows and spread
by a second smaller loader. This method would be less expensive than uti-
lization of loaders alone because of the distance and time required to tra-
vel to the windrows in a typical operation.
One possible site arrangement would be a configuration approximately 1,000
ft square. About 95 500-ft-long windrows could be accommodated on each
side of a central access aisle. Each windrow would be 10 ft wide and 3 ft
deep. Initially, wastes would be windrowed in every other row. About
three 500-ft windrows would be constructed daily, and, during the first
month after earthworm addition, three additional top-dressings of wastes
would be applied to each windrow, as at Ogden. After one-half of the total
area for windrows was constructed, shredded wastes would be windrowed on
the alternate rows. The site would be equipped with a sprinkler system for
initial moistening of the windrows to achieve the proper moisture content.
Based on pilot-plant experience, earthworms would be added to one-half of
the windrows (480,000 sq ft) at a rate of 1.8 Ib/sq ft; a total of approxi-
mately 430 tons of earthworms would be required for this initial earthworm
addition. Earthworms recovered during harvesting would be reused for new
windrow construction. Several researchers ((23) and J. McClarran, per-
sonal communication) have suggested that excess earthworms could be pro-
duced during vermicomposting, but more research is needed to determine the
rates at which earthworms will breed under conditions of vermicomposting.
In order to reduce capital costs, several vermicomposting operators have
suggested that only one-fourth to one-third of the total required stock
might be purchased initially, with the process phased into full operation
over a period of several months as excess earthworms are produced. For
this report, we have assumed that one-half of the total area would be
stocked with purchased earthworms because of the lack of data on earthworm
production during vermicomposting. Even if minimal costs were included for
earthworm purchase, the net costs of vermicomposting would be relatively
unchanged with respect to other alternatives.
After a total residence time of 130 days, the wastes would be recovered
from the windrows by a front-end loader. At this point, nearly all the
biodegradable portion that can be converted by earthworms would have been
consumed. Approximately 450 cu yd (74 tons) of material would be removed
daily. The wastes would be transported by front-end loader to a movable
surge hopper located above a central collecting conveyor, which would
move material to the screening area.
Two rotary harvesting screens, each approximately 6 ft in diameter and 12
ft long, would be employed; one screen would serve as a standby. The
screens would be fed directly by the variable-speed conveyor. Castings
would fall through the screen to a product storage pile. The operation
24
-------
could be expected to produce approximately 300 cu yd (43 tons) of castings
per day. Residual waste would be discharged at the low end of the inclined
screen to a conveyor, which would remove the material to another storage
pile. These wastes -- totalling about 150 cu yd, or 31 tons of residue per
day — could then be recovered by a front-end loader and trucked to the
landfill.
The harvesting screen would also be able to collect earthworms for reuse.
The compacted residue volume would be about 19 acre-ft per year. Based on
a total lift of about 10 ft, about two acres of landfill would be required
each year. For the 20-yr planning period considered in this report, a 38-
acre landfill site would be required. The site might be developed in 5- to
10-acre modules.
25
-------
SECTION 4
ECONOMICS OF VERMICOMPOSTING
BASIS OF COSTS
In this section, costs are estimated for a vernricomposting facility based
on requirements developed in Section 3. All costs, which are based on
Spring 1980 prices, include total capital costs, amortized capital costs
and annual operating costs. The net cost for each alternative is expressed
in total annual dollars, including credit for revenues, and in terms of
cost per ton processed. Cost per ton is based on processing 31,200 tons of
municipal solid waste per year (100 tpd, 6 day/wk operation).
Capital costs are amortized at a 7 percent interest rate over a 20-yr
planning period, according to EPA cost-effectiveness analysis guidelines.
Structures are assumed to have a service life of 20 yr, equipment a service
life of 10 yr. Land was assumed to have a salvage value after 20 yr equal
to the purchase price. Land costs were taken as $5,000/acre, but this will
vary considerably from site-to-site with much higher costs in urban areas.
COSTS OF VERMICOMPOSTING
The costs of vermicomposting can be divided into three components: prepro-
cessing, vermicomposting, and residue disposal. As was noted in Section 3,
of the 100 tpd received at a facility, about 92 tpd would be vermicom-
posted, and, of this, about 31 tpd would remain as residue requiring land-
fill disposal. The same costs are used for the 92 tpd routed to
vermicomposting for the 1,200-tpd facility.
Preprocessing Costs
Table 2 shows the costs of preprocessing. Site acquisition (two acres) and
site development (including utilities) would total about $220,000. Three
buildings (receiving, shredding and storage) would cost about $730,000.
Equipment costs would be $845,000, with the shredder accounting for about
one-half of the costs. Total costs are approximately $1,800,000, or about
$206,000 on an equivalent-annual-cost basis.
26
-------
Table 2
COSTS OF PREPROCESSING FOR A 100-TPD VERMICOMPOSTING FACILITY
Service
Capital Costs Cost Life
Site Acquisition & Development $160,000
Utilities 60,000 20
Structures:
Receiving 270,000
Shredding 260,000
Storage 200,000
730,000 20
Equipment:
Apron Feed
Conveyor 280,000
Shredder 430,000
Ferrous Magnet 45,000
Ferrous Conveyor 15,000
Front End Loader 75,000
850,000 10
Total (Rounded) 1,800,000
Operating Costs
Labor
Maintenance
Power
Fuel
Subtotal (Rounded)
Total (Rounded) $1,800,000
Amortization Annual
Factor Cost
0.070 $ 11,000
0.094 6,000
0.094 69,000
0.142 120,000
$210,000
123,000
70,000
33,000
15,000
$240,000
$450,000
27
-------
Operating costs include labor, maintenance, power, and fuel. Labor costs
are based on six employees: a supervisor, a loader operator, a mechanic
and three laborers. Maintenance costs include periodic major overhaul and
repair of facilities to account for expected shredder explosions. Power
costs include operation of conveyors, the shredder, lighting and HVAC and
are based on $0.05/kWh. Fuel (diesel and oil) costs for the front-end
loader are based on January 1980 prices. Total annual operating costs are
$240,000.
Total annual costs, including amortized capital, are about $450,000.
Vermicomposting Costs
The costs of vermicomposting facilities are shown in Table 3. Total land
area requirements for vermicomposting are 23 acres. Costs for land and
site development total $20,000/acre, including grading and drainage facili-
ties. Equipment costs for vermicomposting, at $545,000, include stationary
and mobile materials-handling equipment, an irrigation system, and two
rotary screens for product harvesting.
In order initially to stock 50 percent of all windrows at 1.8 Ib/sq ft, 430
tons of earthworms would be required. Earthworm prices generally range
between $2 and $3 per pound. At an average of $2.50/1b, a total capital
investment of $2,150,000 is required.
Vermicomposting entrepreneurs have suggested that earthworms would have a
resale value at the end of the 20-yr project life equal to or exceeding the
initial purchase price. Therefore, capital cost estimates should be based
on the differential between initial purchase price and final sale price, or
about $0.50/lb. Because the market for worms bred in a municipal solid
waste vermicomposting operation is unknown, however, we have used the
$2.50/1b estimate.
Total capital costs for vermicomposting are $3,150,000, or an equivalent
annual cost of about $310,000. Operating costs include labor, maintenance
and utilities. Six persons would be required to operate a 100-tpd ver-
micomposting facility: a supervisor, screen operator, two loader operators
and two truck drivers. Total labor costs are $129,000. Maintenance of
equipment is about $16,000/yr. Utility costs ($67,000) include fuel for
loaders and trucks, power for conveyors and pumps, and water for irriga-
tion. Total operating costs are about $210,000.
Total annual costs for the vermicomposting facilities, including amortized
capital, are about $520,000.
Residue Disposal Costs
Costs for residue disposal in a landfill are shown in Table 4. As was pre-
sented earlier, about 19 acre-ft per year of residue is generated at a 100-
tpd vermicomposting facility. Based on a 20-year planning period, and
28
-------
Table 3
COSTS OF VERMICOMPOSTING FOR A 100-TPD VERMICOMPOSTING FACILITY
Capital Costs
Cost
Site Acquisition & Development $460,000
Equipment:
Conveyors $300,000
Screens (2) 30,000
Irrigation System 15,000
Front End Loader 75,000
Front End Loader 25,000
Dump Trucks (2) 100.000
Service Amortization
Life Factor
0.070
Earthworm Stock
Total (Rounded)
Operating Costs
Labor
Maintenance
Utilities
Subtotal (Rounded)
Total (Rounded)
545,000
2.150,000
$3,150,000
10
20
0.142
0.094
Annual
Cost
$ 32,000
$3,150,000
77,000
202,000
$310,000
129,000
16,000
67,000
$210,000
$520,000
29
-------
Table 4
COSTS OF RESIDUE DISPOSAL FOR A 100-TPD VERMICOMPOSTING FACILITY
Service Amortization Annual
Capital Costs Cost Life Factor Cost
Site Acquisition $190,000 - 0.070 $13,000
Site Development 310,000 20 0.094 29,000
Equipment 75,000 10 0.142 11,000
Total (Rounded) $575,000 $50,000
Operating Costs
Labor 22,000
Fuel 15,000
Maintenance 5,000
Subtotal (Rounded) $40,000
Total (Rounded) $575,000 $90,000
30
-------
10-ft lift available, a 38-acre site is, therefore, required. Initial site
acquisition cost is $190,000. Although site development cost is based here
on the total 38 acres, the site development would, in actual practice,
occur in 5- to 10-acre increments throughout the life of the project.
A truck loader costing about $150,000 is required for the landfill opera-
tion. For this report, we have used one-half of the total estimated capi-
tal and operating costs, because the loader would only be utilized for
disposal of vermicomposting residues about 50 percent of the time. We have
assumed that the remainder of available loader time could be dedicated to
another municipal function. Total capital costs for residue disposal are
$575,000, or about $53,000/yr taking into account varying service lines.
Annual operating costs for the landfill operation include labor ($22,000),
fuel for equipment ($15,000) and maintenance ($5,000). Total operating
costs are $42,000.
Total annual costs for residue disposal, including amortized capital costs,
are $95,000.
Table 5 presents a summary of the total costs of vermicomposting including
preprocessing, vermicomposting and residue disposal. Total capital costs
for a 100-tpd facility are $5,525,000, or an equivalent annual cost of
$1,065,000. Based on processing 31,200 tons of municipal solid waste per
year, the unit cost is $34/ton. This is a disposal cost. It does not
include the collection costs that are normally incurred by a municipality.
Potential Product Revenues
Net costs include the credit for revenues generated by the sale of ferrous
metals and earthworm castings. Based on spring 1980 secondary-materials
market prices reported in Iron Age Magazine Journal, ferrous metals can be
sold for $30 to $50/ton assuming minimal transportation costs. Assuming
recovery of 2,500 tons/yr, the revenue is between $75,000 to $125,000.
There are no known markets for the sale of earthworm castings derived from
municipal solid waste. There are some operations involving the sale of
horticultural potting mixes that are composed, in part, of castings pro-
duced from the vermicomposting of manure and other nonmunicipal wastes.
Earthworm castings might be compared with some validity to compost, which
is usually given away or sold for less than $5/ton. Earthworm castings
cannot' be compared to dried sludge products such as Milorganite, which have
much higher nitrogen and phosphorus contents.
Several vermicomposting operators and researchers have suggested potential
market prices. Gaddie has suggested that earthworm castings produced from
municipal solid waste would be sold for $28/ton. Ervin, in an economic
evaluation of a vermicomposting operation in Florida, has suggested a sale
price of $15/ton (29). For this report, we have used a range of $0 to
$15/ton, reflecting the lack of marketing experience. Based on 13,400 tons
of castings recovered per year, annual revenues are $0 to $200,000.
31
-------
Table 5
TOTAL COSTS OF VERMICOMPOSTING MUNICIPAL SOLID WASTES FOR
A 100-TPD FACILITY
Preprocessing Facilities
Vermicomposting Facilities
Residue Disposal
Subtotal (Rounded)
Revenue:
Ferrous Metals
Earthworm Castings
Net Cost (Rounded)
Cost Per Ton
Capital
$1,800,000
3,150,000
575,000
$5,500,000
Annual
$450,000
520,000
90,000
$1,060,000
75,000-125,000
0-200,000
$5,500,000 $1,000,000-750,000
$32 - $24
32
-------
Total Vermicomposting Costs
Total costs of vermicomposting 100 tpd of municipal solid waste, taking
into account potential product revenues, are about $750,000 to $l,000,000/yr
or approximately $24 to $32/ton processed.
Gaddie has estimated total conversion time at 70 days, rather than the
110 days used in this report. To examine the sensitivity of this design
parameter on costs, the costs of vermicomposting were also calculated
assuming a requirement for only about 65 percent of the area used pre-
viously. Under these conditions, total annual costs for vermicomposting
might decrease from $520,000 to about $400,000, reducing the net cost
after revenues to $20 to $28/ton.
COMPARISON WITH ALTERNATIVE METHODS OF MUNICIPAL SOLID WASTE MANAGEMENT
Landfill Disposal
For a municipality of 50,000, the most common method of solid-waste manage-
ment is a sanitary landfill. Table 6 shows the estimated costs of land-
filling. Site acquisition costs are $560,000, based on 112 acres at
$5,000/acre. Total site development costs are $760,000 and are based on a
20-yr site life. Equipment requirements are $150,000 for a track loader.
The equivalent annual cost of $21,000 takes into account a 10-yr service
life and purchase of a second loader in 10 yr. Total capital costs are
about $1,500,000, or about $130,000/yr.
Operating costs include labor, fuel and utilities. Two operators are
required for the landfill operation. Fuel costs are based on an average
loader operation of 7 hr/day, 312 days per year. Total operating costs are
about $60,000.
Total annual costs for landfilling are about $190,000, or $6 per ton pro-
cessed.
Combustion in Modular Combustion Units
Another method of solid-waste management for small communities is com-
bustion in modular combustion units (MCUs). Costs are presented in Table
7. Site acquisition is based on four acres for the MCU facility and 16
acres for the landfill required for ash disposal. Approximately $410,000
is required to develop the MCU and landfill sites. The MCU structure,
including receiving building, costs $1,350,000. Costs for the modular com-
bustion unit are $2,110,000 and include the boiler, feedwater treatment
equipment and the steam supply line. Landfill equipment includes a track
loader ($150,000) and haul truck ($50,000). Total capital costs are about
$4,200,000, or an equivalent annual cost of $400,000.
33
-------
Table 6
COSTS OF LANDFILLING MUNICIPAL SOLID WASTES FOR A
100-TPD FACILITY*
Capital Costs
Site Acquisition
Site Development
Equipment
Cost
$560,000
760,000
150,000
Service
Life
_
20
10
Amortization
Factor
0.070
0.094
0.142
Annual
Cost
$39,000
71,000
21,000
Subtotal (Rounded)
$1,500,000
$130,000
Operating Costs
Labor
Fuel
Utilities
Maintenance
Subtotal (Rounded)
Total (Rounded) $1,470,000
Cost Per Ton (Rounded)
30,000
20,000
2,000
10,000
$60,000
$190,000
$6.00
*Reference 24, 25, 26
34
-------
Table 7
COSTS OF COMBUSTION OF MUNICIPAL SOLID WASTES IN
MODULAR COMBUSTION UNITS (MCUs) FOR A 100-TPD FACILITY*
Capital Costs
Site Acquisition
MCU Site Development
Landfill Site Development
MCU Structure
MCU
Landfill Equipment
Subtotal (Rounded)
Operating Costs
Labor
Fuel
Utilities
Maintenance
Subtotal (Rounded)
Total
Revenue from Sale of Steam
Net Cost
Cost Per Ton (Rounded)
Service Amortization Annual
Cost Life Factor Cost
$ 100,000 - 0.070 $ 7,000
220,000 20 0.094 21,000
190,000 20 0.094 18,000
1,350,000 20 0.094 127,000
2,110,000 20 0.094 200,000
200,000 10 0.142 28,000
$4,200,000 $400,000
240,000
80,000
25,000
35,000
$380,000
$4,200,000 $780,000
$300,000
$480,000
$15.00
*Reference: 28
35
-------
Operating costs include labor, fuel, utilities and maintenance. Total
labor costs are $240,000 and based on two-shift operation of the MCU
facility (11 persons) and labor for the landfill operation (one person).
Fuel costs are $60,000 for combustion and $20,000 for landfill equipment.
Utility costs, including power and water, are $25,000. Maintenance of
the MCU and equipment for hauling and landfilling ash costs approximately
$35,000/yr.
Total operating costs are $38ti,000/yr, or $780,000 including amortized
capital costs.
An MCU unit would probably not be used without a long-term market for
steam. Revenues from sale of steam produced in the MCU is based on 9
million BTUs per ton of refuse and 5,500 Ib of steam produced per ton
burned. Annual steam sales of $300,000 are based on availability of an
adjacent steam market.
Total system costs, including credit for revenues, are $480,000 per year,
or approximately $15/ton.
Windrow Composting
Although technically proven, commercial composting operations have not been
economically attractive in the United States. During the 1950s and 1960s,
there were about 20 solid waste composting facilities in operation (30).
Nearly all were closed because of high operating costs. For this report,
the costs of composting are based on .the windrow method, which was operated
successfully for several years by the U.S. Public Health Service at Johnson
City, Tennessee.
The typical composting facility includes three components: preprocessing,
composting, and landfill ing of solid waste residue. The solid waste is
received, shredded, and then separated by either an air classifier or trom-
mel screen. This scheme is based on an EPA report evaluating small-scale
and low technology resource recovery study (31). The heavy fraction is
conveyed to .ferrous removal and the residue is landfilled. The light frac-
tion is windrowed for about eight weeks in a 4-acre composting area. The
loading rate is about 12.5 tons/acre/day. A windrow composting machine is
used to periodically turn the windrows. A 2-week curing step follows com-
posting. About one additional acre of land is required for curing. The
compost produced is a humus-like material which can enhance the quality of
soil.
Table 8 shows the estimated costs for a 100-tpd windrow composting faci-
lity. Site acquisition and development costs are^about $1,250,000 and
include area for a preprocessing facility, a 5-acre paved facility and develop-
ment of a landfill. Landfill development costs are slightly higher for
composting compared to vermicomposting because more residue is produced (42
tpd versus 31 tpd). Costs for structures ($800,000) are for preprocessing
facilities and include areas for receiving, shredding, separation and
36
-------
Table 8
COSTS OF WINDROW COMPOSTING FOR A 100-TPD FACILITY
Service Amortization Annual
Capital Costs Cost Life Factor Cost
Site Acquisition
and Development $1,250,000 - 0.07 $ 88,000
Structures 800,000 20 0.094 75,000
Equipment 1,600,000 10 0.142 227,000
Totals (Rounded) $3,700,000 $390,000
Operating Costs
Labor 300,000
Maintenance 110,000
Power 40,000
Fuel 100,000
Sub-Total 550,000
Totals (Rounded) $3,700,000 $940,000
Revenue
Ferris Metals 75 - 125,000
Compost 0 - 80,000
Net Cost (Rounded) $3,700,000 $74,000 - $870,000
Cost per Ton (Rounded) $24 - $28
37
-------
ferrous removal; they are about the same as for vermicomposting. Equipment
costs are the same as for vermicomposting with the addition of a separation
device and a mobil composting machine. Total equipment costs are
$1,600,000. Total capital costs are approximately $3,700,000, or an
equivalent annual cost of $390,000.
Operating costs include labor, maintenance, power and fuel. Labor costs
are approximately $300,000/yr and include preprocessing, composting and
landfill ing. Maintenance and fuel costs are for operating the prepro-
cessing equipment and mobil equipment such as loaders and trucks. Power
costs are principally for operation of the preprocessing equipment and
total about $40,000. Total annual operating costs are $550,000.
Total annual costs including amortized capital plus operation are $940,000.
Expected revenues for a composting facility are for sale of ferrous metals
and compost. Based on the assumptions presented earlier, the annual reve-
nue for ferrous metals is between $75,000 and $125,000. Reliable estimates
do not exist for the selling price of a compost product. For this report,
the value of the compost has been set at a range of $0 to $5/ton, or
approximately its value as a topsoil substitute. Based on a production of
about 16,000 ton/yr, the revenue could be up to $80,000/yr. Net costs for
composting are $740,000 to $870,000/day, or approximately $24 to $28/ton
processed.
Summary of Alternatives' Costs
Unit costs for management of 100 tpd of municipal solid waste are sum-
marized below:
Method Approximate net cost ($/ton)
Sanitary Landfill 6
Modular Combustion Unit 15
Windrow Composting 24-28
Vermicomposting 24-32
For municipalities with sufficient available, appropriate land, a sanitary
landfill is the most economical method of solid-waste management. Windrow
composting was found to cost about the same as vermicomposting. In this
analysis, modular combustion units were found to cost 2 1/2 times as much
as a landfill. Where landfill sites are difficult to obtain and where an
energy market exists, however, an MCU might be selected.
Based on this analysis, vermicomposting is not competitive with the other
two methods of solid-waste management. Even with the maximum projected
market for recovered products, the cost of vermicomposting is four times
38
-------
the cost of landfill ing. Vermicomposting becomes competitive with other
methods only when a shredded waste is available at no cost to the opera-
tor. In that case, the cost of vermicomposting and residue disposal would
be about $9 to $17 per ton.
ECONOMICS OF VERMICOMPOSTING A PORTION OF THE WASTES OF A 1,200-TPD RDF
FACILITY
We have considered vermicomposting as a potential alternative in solid-
waste management for a metropolitan area of 500,000 persons. To make the
alternative as attractive as is reasonable, we have assumed that the muni-
cipality already owns and operates a facility that is producing refuse-
derived fuel from some 1,200 tpd of solid waste and burning the total
amount of RDF- Vermicomposting would be conducted as a side operation of
100 tpd of the total 1,200-tpd waste stream.
The 1,200-tpd combustion facility, including RDF preparation, would have
a net annual cost of $7,600,000, or about $20/ton processed. This net
cost includes a credit for energy recovery in the form of electricity,
steam and ferrous metals. The facility would require location in a large
urban area due to the quantity of refuse required, while also requiring a
large and reliable energy and materials market.
In Table 9, we show the cost difference for vermicomposting obtained when
100 tpd of the total waste stream is diverted to vermicomposting (as
before, ferrous recovery would have removed some 8 tpd of the diverted
wastes, leaving 92 tpd of processed wastes for vermicomposting). Capital
costs for site acquisition, combustion and energy recovery, and residue
disposal would remain the same, since the full 1,200-tpd processing capa-
city is assumed to have been constructed and in operation. An additional
$100,000 would be required in order to install conveyors in the prepro-
cessing area to divert the 100 tpd to vermicomposting.
Capital costs of the 100-tpd (92-tpd actual) vermicomposting operation are
$3,150,000, as shown in Table 3. The total increase in capital costs above
that of a 1,200-tpd RDF facility is $3,250,000, or about $325,000/yr.
Operating costs associated with preprocessing remain the same, since the
total waste stream of 1,200 tpd would be subjected to preprocessing.
Combustion costs would decrease by $280,000, however, since only 1,100 tpd
would be combusted. Residue-disposal costs would remain approximately the
same. Vermicomposting operating costs as shown in Table 3 are $210,000.
The net operating costs for vermicomposting would be $70,000 less than for
the full 1,200-tpd combustion facility.
Including amortized capital costs, increased annual costs, resulting from
the vermicomposting side operation, would total about $255,000.
39
-------
Table 9
COST DIFFERENCE FOR DIVERTING 100 TPD TO VERMICOMPOSTING
FROM A 1,200-TPD RDF FACILITY
Capital Costs
Site Acquisition
Preprocessing RDF
Combustion and Energy Recovery
Residue Disposal
Vermi composting
Subtotal
Operating Costs
Preprocessing RDF
Combustion and Energy Recovery
Residue Disposal
Vermi composting
Cost Difference Annual Cost Difference
0 0
$ 100,000 $ 14,000
0 0
0 0
3,150,000 310,000
$3,250,000 $324,000
0
(-)280,000
0
210,000
Subtotal (-)$70,000
Total $254,000
Revenue: (Sale of castings and ferrous
metals for diverted wastes) (-)$325,000
(Loss of electricity, steam and ferrous
revenues in RDF Facility) $510,000
Net Total Increase In Costs For Vermicomposting $439,000
40
-------
Revenues from sales of products should also be considered, however. As was
shown in Table 5, sales of castings and ferrous metals associated with the
100-tpd composting system might total $325,000/yr. At the same time,
however, yearly revenues of $510,000 from sale of steam and electricity
generated at the RDF facility would be lost because of the diversion of 100
tpd to vermicomposting.
Considering total costs and revenues, a combination of combustion and ver-
mi compost ing would cost about $440,000 more per year than combustion alone.
A municipality owning a large RDF facility would not find it economical to
build and operate a parallel or back-up vermicomposting facility.
41
-------
SECTION 5
VERMICOMPOSTING PRODUCTS AND PRODUCT MARKETING
INTRODUCTION
Successful techniques of vermiculture, including vertni compost ing, produce
castings and earthworms. Potential markets exist for both products; it
has been suggested that income derived from the sale of vermicomposting
byproducts can help to offset process costs.
Markets for earthworms can be divided between markets for live earthworms
(bait for sports fishing, agricultural uses) and those for dried or pro-
cessed earthworms (soil additive, animal feed, high-protein diet supplement
for humans). Castings have been marketed successfully as a component in
potting mixes for horticulture and have been distributed in bulk for land
application.
Recognition of the growth of vermiculture among private entrepreneurs
prompted the California State Legislature in 1978 to define vermiculture
byproducts as an agricultural commodity entitled to the market promotion
and safeguards and product-research provisions contained in the California
Agricultural Code under the Marketing Act of 1937. Specifically, the
legislation states that vermiculture, commercial processing, packaging,
sale and use of its byproducts is considered a branch of the state agri-
culture industry. Consumer safeguards include state regulations governing
contracts, establishing requirements for sellers, and allowing purchasers
to cancel orders for any reason within three business days. The California
Farm Bureau has taken an active role in development and support of ver-
miculture enterprises, through conduct of discussion on industry research
and regulations (J.W. Field, State of California Department of Food and
Agriculture, personal communication).
Similar legislation was enacted in 1979 in the State of Washington.
Several states have used their securities laws and consumer divisions to
regulate the sale of earthworms as breeding stocks. The federal government
has no specific vermiculture regulations.
WORM CASTINGS AS A PRODUCT
Castings have obvious agricultural and horticultural appeal, representing,
as they do, a natural, "organic" soil amendment with attractive structural
properties and low-order plant nutrient values. The castings have a
42
-------
favorable appearance: they lack the offensive odor of wastes (although
they might not be entirely odor-free), and, when sifted and dry, they are
granular, 0.5 to 2.5 mm in diameter, and of a brownish-gray color.
Passage of organics through the earthworm's gut significantly alters the
physical structure of the material. Large particles are broken down into
numerous smaller particles, with a resultant enormous increase in surface
area (18). As a result of the increase in surface area, any remaining
odor-producing sulffdes are completely oxidized, microbial respiration
is accelerated by a factor of 3, and Salmonella bacteria are destroyed at
a higher rate (15, 22).
Remarkable claims have been made for some characteristics of worm castings,
including greatly accelerated humification and formation of water-stable
aggregates. Results of more rigorous research show, however, that these
characteristics pertain more to castings produced by such species as
Lumbricus terrestris and Allolobophora Tonga than to those produced by ver-
micomposting worms.
Agricultural Value
Castings can act beneficially as a slow-release, low-order nitrogen fer-
tilizer. The actual suitability of castings for agricultural use,
however, depends on the composition of the original waste. For example,
castings derived from an aged, anaerobic, wastewater-treatment plant
sludge in San Jose, California, were found by an independent laboratory to
be acceptable for use as a soil amendment in terms of nutrients and sali-
nity, sodium and pH values, but excesses of boron and, possibly, of
phosphorus rendered the material unsuitable for direct use as a planting
soil (32). Analysis of castings derived from a wide variety of feeds
showed most contained amounts of sodium or other salts that would be
detrimental to plant growth (33). To date, no specific analysis is
available for castings derived from vermicomposting of municipal solid
wastes.
Although castings are not generally suitable for use as a sole-source
planting medium, mixture of castings with other materials can yield an
acceptable potting soil. The laboratory analyzing the San Jose product
recommended that castings be incorporated into top layers of agricultural
soils, in bulk, or be mixed in specified proportions with sphagnum peat
moss, Perlite, potassium nitrate, calcium carbonate lime, and iron
sulfate for use as a potting soil, provided that concentrations of heavy
metals were found to lie within acceptable ranges. Other worm growers
have used different mixes; for example, a 1:1:1 mix of castings, peat
moss and Perlite (34).
Anticipated Market Development
The existing or potential markets for castings include:
43
-------
o Use as an ingredient in potting mixtures
o Sale or distribution as an organic soil amendment
o Sale as an organic fertilizer.
The first of these markets has some potential, at least on a local or
regional level. Castings-based potting soils have been successfully
marketed in some areas of the United States, including California,
Washington, Colorado and Ohio. The castings are usually derived from ver-
micomposting dairy manure. Consumers have, in fact, shown themselves to be
willing to pay a small premium for potting soils that contain earthworm
castings, apparently because of good growing performance obtained through
use of the product. These operations are very small, however, and there
are no available estimates of the volume of castings sold.
The second market is bulk sale or distribution of castings as an agri-
cultural soils' amendment. Competition here would be represented by com-
post products offered for land application. The advantages of castings
over these other products lie in their benign odor and appearance and uni-
form quality, all of which are consistent with characteristics of other
non-sludge fertilizers and amendments currently used in agriculture.
The third market, sale as an organic fertilizer, is not a particularly
viable one. In this case, the costs of production are relatively high as
compared to those for other fertilizers containing the same or a greater
amount of nutrients. In addition, the sale of castings as fertilizer
might be constrained by state regulations that define fertilizers in
terms of nutrient value. (Arizona, for example, requires that soil addi-
tives sold as fertilizer have a nitrogen content of at least 4 percent.
The material is also subject to a tax of $0.20/dry ton.) Castings derived
from wastes have a nitrogen (N) content about equal to the original waste
material N content. For wastewater sludge this may vary from 3 to 5 per-
cent. For municipal solid waste the nitrogen content would be below 1
percent.
Whether sold as a fertilizer or soil amendment or distributed in bulk for
application to public lands or farmlands, castings must satisfy the same
criteria as other wastes that are proposed for land application (35).
Passage of wastes through the earthworm's gut and its subsequent minerali-
zation increase the concentrations of heavy metals or other constituents
that might be present in the original wastes. Some of these metals may be
accumulated by organisms in the food chain to levels that might be harmful
to humans. The waste source must not, therefore, be heavily contaminated
by potentially toxic substances. The federal regulations differentiate
between crops for human consumption and non-food chain uses, such as use on
ornamentals. Most concentrations of heavy metals should not present a
problem with application to ornamentals.
44
-------
EARTHWORMS AS A PRODUCT
According to a report prepared by the University of California Cooperative
Extension, "the major use of earthworms today is as bait for freshwater
sport fishing...Some worms are also sold to home and organic gardening
enthusiasts for soil improvement and composting of organic refuse" (36).
Entrepreneurs in the vermiculture industry have made claims for a virtually
unlimited market serving the following sectors:
o Sport fishing (36)
o Inoculation of horticultural (14) or agricultural soils or
reclaimed lands (8, 13)
o Fertilizer or soil supplement (37)
o Animal feed (38)
o Worm stock for vermiculturists (8, 13)
o Human nutrition (14, 39).
Of these market sectors, the only "large stable market" for vermicul-
turists, at present, involves sale of baitworms (40). The remaining sec-
tors must be described as speculative, at best. For vermicomposting
operations, additional constraints operate, as discussed below.
Recreational Market
L. rube!1 us and E. foetida are reported to be satisfactory baitworms, but
both are rather small— particularly when raised under high-density con-
ditions of composting — and so are rather difficult to handle. Some
anglers consider nightcrawlers -- not a "domesticated" species -- to be
superior baitworms (8, 41), due primarily to their larger size.
Nationally, the market for worms used as bait by sport fishermen has been
estimated variously at $5 million (McNelly, personal communication), $26
million (8), $50 million (41, 42), and $80 million (13). The U.S. Depart-
ment of Agriculture (USDA) has made no objective analysis or projection
of the baitworm market, nor has it played any role in regulating or pro-
moting the market (Mr. J. Schwartz, USDA, Beltsville, Maryland, personal
communication).
It is difficult to make a valid analysis of the market, because much of
the local demand is filled by youthful entrepreneurs selling collected
nightcrawlers at roadside stands and by small-scale growers. Other
segments of this market are handled through mail order by large-scale
growers and wholesalers selling in bulk to retail outlets such as bait
shops, tackle shops and fishing resorts.
45
-------
Retail prices for baitworms range from $1.25 per hundred to $0.50 per
dozen, depending on area and the local supply of baitworms. Some retail
enterprises reportedly rely on vending machines placed in strategic loca-
tions near fishing centers (13).
The University of California Cooperative Extension notes that on occasion
the established "local markets have become saturated" by the entry of new
worm growers into the business (40).
Beyond the constraint posed by lack of market capacity, distribution of
live earthworms that have been raised in wastes could pose public health
hazards through exposure of buyers to pathogens contained in or on the
worms' bodies or in the substrate. Although this problem might be solved
by keeping market-ready worms in a clean substrate for a period of time
prior to sale (as is done in shellfish depuration), the added cost of
this step, even if feasible, would affect the competitiveness of the
waste-raised worms in the baitworm market. No studies are available that
indicate the level of pathogenic organisms in earthworms raised in wastes.
Inoculation of Soils
The USDA is on record with the view that earthworms are indicators -- and
not agents — of good agricultural soil. The University of California
does not recommend use of earthworms for soil improvement "because we do
not know of research data which substantiate claims sometimes made for
this" (40). And, although industry sources claim this market "is so
large and varied that it is almost impossible to list and discuss," these
sources are unable to give even an approximation of its value (13).
Even if a market were available, the demand could not be addressed by a
vermicomposting operation. The vermicomposting species E. foetida and L.
rubellus are suited only to life in soils containing a very high percentage
of organic material. Placed in agricultural soils, these worms are unli-
kely to survive more than one season (8); their activity during this season
is unlikely to improve plant growth (43). Incorporation of both substrate
and worms into farm soils might provide a sufficient organic base to extend
the worms' useful lifespan somewhat, but this practice would be subject to
the same regulatory constraints as apply to land application of any waste.
Since the worms would provide no benefit that could not be provided by
indigenous populations of the same or different species, the higher cost
and management requirements for implanting worms would appear to be
unjustified.
Fertilizer or Soil Supplement
It has been projected that conversion by worms of the nation's 16 million
tons of wastewater sludge and 120 million tons of municipal refuse produced
annually would yield a byproduct of dehydrated earthworms totaling 150,000
tons of 10-percent nitrogen material (37). The economics of the worm
market, however, argue against the use of dried worms as a high-nitrogen
46
-------
fertilizer or soil additive. Worms are currently selling at approximately
$2.50/lb, wholesale. As worms are more than 80-percent water by weight,
more than 5 Ib of live worms would be required to produce 1 Ib of
dehydrated worms. A 5-lb bag of 10-1-1 fertilizer from dried earthworms
would cost the wholesaler $62.50. Even in poor market conditions, ver-
miculturists can find more realistic -- if limited -- markets in sale of
live worms to other breeders, organic gardeners, and sport fishermen.
As for the vermicomposting operation, it seems unlikely that worms would
be available in such excess as to justify wasting of worm stock for use
as a nitrogen additive.
Worm Stock for Vermiculturists
Vermiculturists consider this market to be second only to the fishbait
market in its potential (8, 13). Assuredly, it is a market that has served
some entrepreneurs well; however, some practices in this market have been
legally questionable and have cast a shadow on the larger industry. "Buy-
back" arrangements, in which large distributors sell starter packages to
home growers with agreement to purchase all worms produced, have often been
violated, resulting in large financial losses to buyers and the shutting
down of worm-distribution operations in several states (including Florida,
Oregon, Wisconsin, Colorado, and California). Buy-back agreements with
fixed-price guarantees (sometimes referred to as "binning") are subject to
regulation by the U.S. Securities and Exchange Commission (13).
Earthworm stock is not a viable market for other vermicomposting opera-
tions, due in part to the potential transmission of disease by pathogenic
bacteria and viruses adsorbed onto worms that are raised in wastes.
Although the magnitude of this problem has not been documented, some have
speculated that the sale of cocoons, rather than live worms, might be
feasible (44, 45). Potential advantages of this approach include the light
weight, longevity under proper storage, and relative hardiness of cocoons
(as compared to earthworms) and the possibility that external surfaces of
cocoons could be disinfected by low heat or air drying without harming the
developing worms inside. These techniques have not been developed,
however, and they may or may not be needed for earthworms raised in munici-
pal solid wastes.
No reliable estimate has been made of market potential for the sale of
either worms or cocoons to other growers, although those in the industry
claim tha.t demand exceeds supply.
Typical 1974 prices (13) are as follows:
o Breeder stock — $6.50 to $18 per 1,000 with discounts up to 80
percent in quantities of 50,000 or over
o Bed-run (mixed sizes) stock — $5.50 to $12 per 1,000 with discounts
up to 80 percent in quantities of 25,000 and over
47
-------
o Established beds — $100 to $300 each with no contractual (buy-
back) agreement, $350 to $600 each with a contractual agreement.
These prices appear to be in line with current prices. No reliable ana-
lysis has been made of market potential; there is a likelihood that entry
of a few major new cocoon or worm suppliers would swamp the market and
might drastically reduce prices.
Animal Feed or Human Nutrition
The composition of E. foetida is high in protein, as shown in Table 10. A
comparative analysis of amino-acid composition in worm meal and commercial-
grade meat meal and fish meal, as shown in Table 11, indicates that "the
earthworm product has a relatively high level of the essential amino acids,
particularly the important sulphur-containing ones (cysteine and
methionine)" (39).
Table 10
COMPOSITION OF EISENIA FOETIDA*
Dry matter (%) 20-25
Composition of dry matter
(worm meal)
Crude protein (% Kjeldahl
Nx6.25) 62-64
True protein (%) 60-61
Fat (%) 7-10
Ash (%) 8-10
Calcium (%) 0.55
Phosphorus (%) 1.00
Gross Energy (Kcal/Kg) 3900-4100
from Reference 39
-------
Table 11
AMINO ACID ANALYSES (%) OF HIGH-PROTEIN MEALS*
Arginine"!"
Cysteine
Glycine
Histidine"*"
Isoleucine"!"
Leucine"1"
Lysine^
Methionine"!"
Phenylalaninei"
Serine
Threoninei"
Tyrosine
Valine"1"
Crude protein
Worm
Meal
4.1
2.3
2.9
1.6
2.6
4.8
4.3
2.2
2.3
2.9
3.0
1.4
3.0
61.0
Meat
Meal
3.5
1.1
7.1
1.0
1.3
3.5
3.1
1.5
2.2
2.2
1.8
1.3
2.2
51.0
Fish
Meal
3.9
0.8
4.4
1.5
3.6
5.1
6.4
1.8
2.6
_
2.8
1.8
3.5
60.9
*From Reference 39
"•"Essential ami no acids in nutrition, as higher vertebrates
cannot synthesize these from nitrogen sources.
Worm meal can be prepared by washing worms clean and then freeze-drying
or low-temperature hot-air drying the worms (39). Two University of
Georgia researchers have found that dried earthworm meal was palatable to
domestic cats (17). Earthworm meal has been compared to meat meal in
small-scale feeding experiments on broiler chickens, and to meat meal and
a commercial preparation in an experiment with weanling pigs. In both
cases, animals raised on worm meal showed no ill effects and, in fact,
grew as rapidly as those raised on the more conventional diets. In addi-
tion, the broilers gained weight as rapidly on the worm-meal diet while
consuming 13 percent less food (39). To date, there has been no federal
regulation of earthworm meal.
Those in the vermiculture industry who have investigated this market (44)
report that, in order to be competitive, worm meal must be priced in or
near the range of $0.10/lb (1979 prices for meat and bone meal) to $0.17/lb
(for fish meal). Current wholesale worm prices are two orders of magnitude
higher.
The USDA reports no current use of worm meal as a feed product, either for
livestock or for pet food. The University of California Cooperative
Extension, in its 1978 investigation of worm markets (40), could identify
no markets for use as animal feed. The California Department of Fish and
49
-------
Game reported to the Extension that fish farmers use pelleted food — and
not earthworms — to feed fish. In the literature, at least one vermicom-
posting operation in Japan is providing worm meal to fish farmers. Other
sources of protein meal, including soybeans, are known to be less expensive
than worm meal (13).
The same market constraints as are reported for other uses of live worms
apply to the feed market. The presence of pathogens in the waste substrate
and adsorbed onto the surface of the worms, the accumulation or con-
centration of certain heavy metals in worm body tissue, and the fact that
earthworms are known intermediate hosts and passive agents in transmission
of parasites to poultry, swine and small mammals (11) — all make it essen-
tial that distribution, sale and use of waste-raised earthworms be regu-
lated and monitored. Steps used in processing of worm products could
control transmission of biological agents, but only source-control measures
and limits on worm residence time in wastes could prevent excessive accumu-
lation of heavy metals in worm tissues.
MARKET PROSPECTS
Most markets that have been proposed for castings and worms appear to be
severely limited by lack of market demand and by potential public-health
considerations that must be addressed in distributing any waste-derived
product. The nutrient value of castings, however, and their aesthetic and
handling characteristics make them a desirable agricultural soils amend-
ment. Provided that the waste from which the castings are derived is rela-
tively "clean" in terms of heavy metals and other toxics and provided that
pathogen removal can be demonstrated (or developed) as part of the ver-
micomposting process, castings have the potential of filling local or
regional demand for a low-order fertilizer and soils amendment. The
material could be mixed with other potting materials for sale as a planting
medium, bagged for wholesale distribution, or stockpiled for pickup by
local gardeners and farmers.
Although prospects are undefined for product income offsetting production
costs, this market would serve, at the very least, to reduce a
municipality's current costs for disposal of municipal solid wastes.
50
-------
SECTION 6
ENVIRONMENTAL AND PUBLIC HEALTH
ASPECTS OF VERMICOMPOSTING
There are two major areas of concern in the selection of vermicomposting as a
municipal solid waste management technique: potential on-site problems at
the vermicomposting facilities, and potential risks in the use of vermicom-
posting products.
POTENTIAL ON-SITE PROBLEMS
A vermicomposting facility must comply with Environmental Protection Agency
"Criteria for Classification of Solid Waste Disposal Facilities and Prac-
tices," regulations that were issued in September 1979 as an implementation
of Subtitle D of the Resource Conservation and Recovery Act (RCRA). The
regulations contain criteria for determining what solid-waste practices pose
potential adverse effects on health or the environment. Impacts on flood-
plains, endangered species, surface waters, groundwater, food-chain croplands,
disease, and safety are discussed; several of these factors are of importance
in assessing the environmental and public-health aspects of vermicomposting.
Site Runoff and Leachate
Possible site runoff and leachate pose threats to both surface and ground-
waters. In order to protect off-site surface waters, rainfall runoff
should be diverted around the site by means of a simple drainage system.
On-site runoff should be collected for discharge to sewers or be stored in
holding tanks or ponds for later disposal to sewers or for separate treat-
ment. The magnitude of on-site runoff can be controlled by limiting irri-
gation to the minimum required.
Most precipitation will be absorbed by the windrows of relatively dry muni-
cipal solid*waste; in fact, wastes can be expected to have a moisture con-
tent of about 30 percent and so need to be moistened to about 50 to 60
percent to initiate composting. Up to 15,000 gal/day of water may be
required for irrigation at a 100-tpd facility.
Another major concern is prevention of the infiltration of polluting
nutrients or toxic materials into groundwater supplies. The RCRC regula-
tion prohibits any contaminant levels in groundwater that exceed the
51
-------
National Interim Primary Drinking Water Regulation standards, which include
inorganic and organic chemicals, coliform bacteria and radioactivity.
Leachate can be controlled either by selecting a facility site that is
underlain by an impervious soil layer or by installing an underlying imper-
vious layer of soil or synthetic material.
Disease Vectors
A vermicomposting facility should be designed to minimize the on-site
population of rodents, flies and mosquitoes capable of transmitting
disease to humans. At the facility visited during this study, disease vec-
tors were not a problem and have not reported to be a problem at other
installations.
Adult flies and fly larvae and pupae are brought into the facility with
the solid waste. However, temperatures reached during the thermophilic com-
posting phase are lethal to fly larvae and eggs (46). A properly operated
vermicomposting operation would be preceeded by a period of windrow com-
posting.
Protective fences have been used at some sludge vermicomposting facili-
ties to prevent predation by ground squirrels, moles, armadillos and
birds, all of which eat worms. One vermicomposting operator notes that
small animals have caused no severe problems at his operation, despite
the fact that it is located near a wildlife sanctuary (47).
Although birds have not been cited as a problem at most vermicomposting faci-
lities, it seems likely that at a large facility (as at most landfill
sites) their population would increase. Some earthworm loss might be
expected.
Safety
Safety is of concern to both the public-at-large and to on-site workers.
The RCRA regulations require that entry to the facility be controlled in
order to minimize the exposure of the public to hazards of heavy equip-
ment and exposed wastes.
Safety hazards to facility operating personnel will be similar to safety
plans applicable to other municipal solid waste disposal facilities and can
be reduced through proper training, use of safety equipment, and other
practices. At a vermicomposting facility, the greatest hazard is in
preprocessing equipment and where mobil equipment is being operated.
Odors
Vermicompost!ng operations require aerobic — and, therefore, relatively
odor-free -- conditions. The use of vermicomposting techniques that hasten
conversion of waste into castings will virtually eliminate any odor
52
-------
nuisance; castings have no objectionable odor and apparently will not
develop odors even when stored for a period of time under adverse con-
ditions. In a test directed by the Texas Department of Water Resources
and conducted by the Angelina & Neches River Authority of Texas, worm
castings were sealed in an air-tight jar and maintained at 70°F. At the
end of seven days, the seal was broken, and tests were made for the pre-
sence of odors, hydrogen sulfide, and other indications of anaerobic con-
ditions. The test report states that the only odor detected was a moist
earthy smell. There were no indications of hydrogen sulfide or anaerobic
conditions (48). No other odor tests on castings have been reported in the
literature.
POTENTIAL RISKS IN DISPERSAL OF PRODUCTS
As discussed previously, the vermicomposting operation yields two products
-- castings and worms — for which there are potential markets. Some of
these potential markets are constrained by limits on demand, and others, by
environmental problems that might result from increased dispersal and
application of waste-derived products. Of primary concern among these
potential environmental problems are the toxic substances and pathogenic
microorganisms that can be present in municipal solid waste. Typical muni-
cipal solid waste would be expected to contain between 15 and 20 percent
food wastes by weight (49). Most substances of a public health concern
would originate in these wastes.
Toxic Substances and Heavy Metals
Use of worm castings as an agricultural soils amendment, landscape "top
dressing", or potting soil ingredient represents the most viable poten-
tial market for a vermicomposting product. Because the castings are
derived from wastes, however, there exists a potential for contamination
of the product by heavy metals, chlorinated hydrocarbons and other toxic
substances. If dispersal is to non-food chain crops the health hazard
would be reduced.
It is not clear whether earthworm consumption changes the availability of
metals to plants. According to research reported in Edwards and Lofty
(11), the (plant) availability of lead and zinc (and calcium) is increased
by worm activity, but Neuhauser has stated that conversion of aerobic
sludge to castings neither increased nor decreased plant-available cadmium,
copper, nickel, lead and zinc (50). Worms apparently are quite capable of
concentrating some heavy metals -- such as cadmium -- to levels high enough
to be toxic to birds or small mammals preying on them (51, 52).
Most researchers have found that worms fed sludge accumulate the following
heavy metals: cadmium (50, 51, 52, 53, 54), copper (51, 55), nickel (52),
mercury (56), zinc (51, 52, 53, 57, 58), and lead (52, 53, 57, 58).
Whether this concentration actually occurs in worms feeding on solid waste
under conditions of vermicomposting has yet to be determined. Apparently,
much depends on the worms' residence time in the substrate, on the water
solubility of the metal in the substrate, and on the level of the metal in
the substrate.
-------
In addition to heavy metals, a number of other toxic substances can be
accumulated or concentrated in worm tissues. Among them are the organ-
ochlorine insecticides such as DDT. It is not known to what degree, if
at all, the process of vermicomposting hastens degradation of these per-
sistent substances.
Uptake of pesticides by earthworms has been reported to the following
levels (11):
DDT and residues 8.0 to 10.6 x soil levels
Aldrin 3.3 x soil levels
Endrin 3.6 x soil levels
Heptachlor 3.0 x soil levels
Chlordane 4.0 x soil levels
The worms' uptake of DDT is relatively rapid; at a concentration of 1 ppm
in the substrate, worms will reach background levels within nine weeks
(11). Organophosphorus insecticides, such as parathion, do not appear to be
concentrated by worms (11).
No studies are available on accumulation of substances during vermicom-
posting of municipal solid waste. The results of the sludge studies show
the general direction, but because solid waste is expected to have lower
concentrations of these substances, the potential risk in dispersal of the
product is likely to be much lower.
Pathogens
Municipal solid wastes undergo a composting phase before the wastes
are vermicomposted. Studies of municipal refuse composting at Johnson
City, Tennessee, showed a significant reduction in coliform bacteria
levels. However, significant regrowth occurred when temperatures dropped
during the last stages of composting. Regrowth might also occur during
the relatively moist and aerobic conditions during vermicomposting.
No studies are available on the pathogens before and after vermicomposting
of municipal solid wastes, however, the Texas Department of Health found no
Salmonella in sludge-derived castings or in live earthworms used in a
Shelbyville vermicomposting operation. At one time, the Shelbyville faci-
lity was vermicomposting raw sludge obtained from the Center, Texas,
wastewater treatment facility (48).
Since very little is known about pathogens remaining in castings, it might
be necessary to establish specific conditions of vermicomposting such as
maintenance of a defined "curing" period for castings, before the castings
could be used.
Several vermicomposting operators have suggested that castings might also
be sterilized by steam treatment, open-flame heating, or exposure to 100
percent methyl bromide gas, but the efficacy of any of these methods is not
known.
54
-------
SUMMARY
Potential on-site problems in vermicomposting include runoff and leachate,
the presence of disease vectors, odors, and worker safety. None of these
problems should be present in a well-designed and operated vermicomposting
facility.
It is likely that vermicomposting facilities will rely on sale of castings
to offset a portion of operating costs. There is a risk associated with
the dispersal of castings which may contain heavy metals and pathogens.
The presence of these substances and organisms has been documented for
castings derived from municipal wastewater sludge. No data is available
for solid waste vermicomposting, however. The relative hazard to public
health needs to be documented.
55
-------
REFERENCES
1. Camp Dresser & McKee Inc. 1980. Engineering assessment of ver-
micomposting municipal wastewater sludges, Municipal Environmental
Research Laboratory, Office of Research and Development, U.S.
Environmental Protection Agency, Cincinnati, Ohio (in press).
2. Carmody, F.X. 1978. Vermicomposting: An assessment of the state
of the art as of May, 1978.
3. Gaddie, R.E., Sr., and D.E. Douglas. 1977. Earthworms for ecology
and profit, Vol II. Bookworm Publishing Company, Ontario, CA.
4. New York Times. Sept. 1977. Japanese industrialists and farmers
look to earthworms for help.
5. Gaff, 0. 1980. Preliminary experiments of vermicomposting of dif-
ferent waste materials using Eudrilus eugem'ae Kinberg. Proceedings
of Research Needs Workshop on the Role of Earthworms in the
Stabilization of Organic Residues. 1980.
6. Hunta, V. 1980. Results of preliminary experiments culturing
Eisenia foetida on different types of sewage sludge, animal and
human excreta mixed with low nitrogen organic materials.
Proceedings of Research Needs Workshop on the Role of Earthworms in
the Stabilization of Organic Residues.
7. Hartenstein, R. 1978. The most important problem in sludge manage-
ment as seen by a biologist. Conf. Proc. on utilization of soil
organisms in sludge management. State University of New York (SUNY)
Coll. of Environm. Sci. Forestry, Syracuse, NY.
8. Minnich, J. 1977. The earthworm book. Rodale Press, Emmaus, PA.
372 pp.
9. Kaplan, D.L., R. Hartenstein, and E.F. Neuhauser. Coprophagic rela-
tions among the earthworms Eisenia foetida, Eudrilus eugem'ae and
Amynthas spp. SUNY Coll. of Environm. Sci. Forestry. Syracuse, NY.
In press.
10. Neuhauser, E.F., D.L. Kaplan and R. Hartenstein. Life history of
the earthworm Eudrilus eugem'ae. SUNY Coll. of Environm. Sci.
Forestry. Syracuse, NY. In Review.
11. Edwards, C.A., and J.R. Lofty. 1977. Biology of earthworms.
Chapman and Hall Ltd., London. 333 pp.
56
-------
12. Minnich, J., M. Hunt and the editors of "Organic Gardening" maga-
zine. 1979. The Rodale guide to composting. Rodale Press, Inc.,
Emmaus, PA. 405 pp.
13. Gaddie, R.E., and D.E. Douglas, 1977. Vol. I. Earthworms for eco-
logy and profit. Bookworm Publishing Company, Ontario, CA.
14. McNelly, J. 1979. Planet Earthworms, Inc. Automated vermicom-
posting system for municipal - solid waste disposal. Application to
U.S. Department of Energy Region VIII Appropriate Technology Small
Grants Program.
15. Hartenstein, R., E.F. Neuhauser, and D.L. Kaplan. A progress report
on the potential use of earthworms in sludge management. SUNY Coll.
of Environm. Sci. Forestry, Syracuse, NY. In press.
16. Mitchell, M.J. 1978. Role of invertebrates and microorganisms in
sludge decomposition. Conf. Proc. on utilization of soil organisms
in sludge management. SUNY Coll. of Environm. Sci. Forestry,
Syracuse, NY.
17. Fosgate, O.T. and M.R. Babb. 1972. Biodegradation of animal waste
by Lumbricus terrestris. Journal of Dairy Science, Vol. 5, No. 5.
18. Mitchell, M.J., R.M. Mulligan, R. Hartenstein, and E.F. Neuhauser.
1977. Conversion of sludges into "topsoils" by earthworms. Compost
Sci., Vol. 18, No. 4.
19. Niessen, W.R. (Principal Investigator). 1970. Systems study of air
pollution from municipal incineration. The division of process
control engineering, National Air Pollution Control Administration,
U.S. Department of Health, Education and Wei-fare. Arthur D. Little,
Inc., Cambridge, MA, March 1970.
20. Neuhauser, E.F., D.L. Kaplan, M.R. Malecki and R. Hartenstein.
Materials supportive of weight gain by the earthworm Eisem'a foetida
in waste conversion systems. SUNY Coll. of Environm. Sci. Forestry,
Syracuse, NY. In press.
21. U.S. Environmental Protection Agency. 1971. Composting of
municipal solid wastes in the United States. SW-47r. Washington, DC.
22. Hartenstein, R., A.L. Leaf, E.F. Neuhauser, D.H. Bickelhaupt and F.
Hartenstein. 1979. Physiochemical changes accompanying the conver-
sion of activated sludge into castings by the earthworm. SUNY Coll.
of Environm. Sci. Forestry, Syracuse, NY.
23. Grobecker, D.W. (for Annelidic Consumption Systems, Inc.). 1978. A
feasibility study: The earthworm conversion of municipal solid
waste. Bookworm Publishing Company, Ontario, CA.
57
-------
24. Camp Dresser & McKee Inc. 1977. Selection and evaluation of alter-
native sanitary landfill sites in La Plata County.
25. Camp Dresser & McKee Inc. 1977. Des Moines Metropolitan Area Solid
Waste Agency, Des Moines, Iowa - Solid waste management plan.
26. Camp Dresser & McKee Inc. Vol. I., Data base report - Oakland
County, Michigan - Resource recovery phase IA. In press.
27. Savage, G.M., and G.R. Shiflett. Processing equipment for resource
recovery systems - ill-field test evaluation of shredders. U.S.
Environmental Protection Agency, Municipal Environmental Research
Laboratory, Office of Research and Development, Cincinnati, OH.
28. Camp Dresser & McKee Inc. 1979. Final draft report - Lamprey Solid
Waste Cooperative - MCU incineration and energy recovery facility
preliminary design report.
29. Ervin, J.W. 1978. A cost analysis of the use of earthworms to
digest shredded residential solid waste. Prepared for American
Earthworm Company, Sanford, FL.
30. U.S. Environmental Protection Agency. 1971. Composting of munici-
pal solid wastes in the United States. Office of Solid Waste
Management Programs.
31. SCS Engineers. 1979. Smasll-scale and low technology resource reco-
very study. U.S. Environmental Protection Agency.
32. Collier Worm Ranch. 1978. Agricultural suitability analysis. Soil
and Plant Laboratory, Inc.
33. Stark, N., P. Pawlowski, and S. Bodmer. 1978. Quality of earthworm
castings and the use of compost on arid soils. Conf. Proc. on util-
ization of soil organisms in sludge management. SUNY Coll. of
Environm. Sci. Forestry, Syracuse, NY.
34. Kluin, G. 1978. Castings: A horticulture blue-ribbon winner. The
Vermiculture Journal. Vol. 1., No. 1.
35. U.S. Environmental Protection Agency. September 13, 1979. Criteria
for classification of solid waste disposal facilities and practices;
final, interim final, and proposed regu-lations. Federal Register,
40 CFR Part 257.
36. Black, J.H., R.M. Hawthorne, and J.P. Martin. 1977. Earthworm:
biology and production. Division of Agricultural Sciences,
University of California.
37. Hall, S.I. 1978. Vermology: A viable alternative for better world
management. The Vermiculture Journal, Vol. 1, No. 1.
58
-------
38. Sabine, J.R. 1978. The nutritive value of earthworm meal. Conf.
Proc. on utilization of soil organisms in sludge management. SUNY
Coll. of Environm. Sci. Forestry, Syracuse, NY.
39. Sabine, J.R. 1978. Earthworms: A new form of proteins. The
Vermiculture Journal. Vol. 1, No. 1.
40. Nelson, L. Jr. 1978. Earthworm Enterprises in California.
University of California Cooperative Extension.
41. Gilbert, B. August 1979. They crawl by night. Sports Illustrated.
42. Scaglione, C. February 18, 1979. Breeder builds army of pollution
fighters. San Diego Union, San Diego, CA.
43. Martin, J.P., J.H. Black, and R.M. Hawthorne. 1977. Earthworm
biology and production. University of California, Div. of
Agricultural Sciences, leaflet 2828.
44. McNelly, J. 1977. Wormglenn: An organic waste recycling center.
Planet Earth Worms. Louisville, CO.
45. American Organic. 1979. Birth of a new agricultural industry: the
worm rancher.
46. Gotaas, H.B. 1956. Composting: Sanitary disposal and reclamation
of organic wastes. World Health Organization Monograph Series No.
31, Geneva, Switzerland. 205 pp.
47. Collier, J. 1978. Conversion of municipal wastewater treatment
plant residual sludges into earthworm castings for use as topsoil.
First Annual Report to NSF. NSF Grant ENV77-16832.
48. Texas Department of Health, letter to City of Lufkin City Manager.
October 7, 1977; Angelina & Neches River Authority, letter to City
of Lufkin City Manager, December 18, 1978.
49. Smith, F.A. 1978. Post-consumer residential and commercial waste
generated and amounts recycled. U.S. Environmental Protection
Agency. Washington, DC - Unpublished data
50. Neuhauser, E.F. 1978. The utilization of earthworms in solid waste
management. Conf. Proc. on utilization of soil organisms in sludge
management. SUNY Coll. of Environm. Sci. Forestry, Syracuse, NY.
51. Helmke, P.A., W.P. Robarge, R.L. Korotev, and P.J. Schomberg. 1979.
Effects of soil-applied sewage sludge on concentrations of elements
in earthworms. J. Environ. Qual., Vol. 8, No. 3.
52. Moreau, J.P- 1977. Effects of municipal sewage effluent irrigation
on the trace metal content of earthworms. A thesis, SUNY Coll. of
Environm. Sci. Forestry, Syracuse, NY.
59
-------
53. Van Hook, R.I. 1974. Cadmium, lead and zinc distribution between
earthworms and soils: Potentials for biological accumulation.
Bull, of Environm. Contain, and Toxicology. Vol. 12, No. 4.
54. France, V.P. 1979. The vermiculture industry today. Arete
Vermicomp, Inc., Canton, OH.
55. Hartenstein, R., A.L. Leaf, E.F. Neuhauser, and D.H. Bickelhaupt.
Composition of the earthworm Eisem'a foetida and assimilation of
fifteen elements from sludge during growth. SUNY Coll. of Environm.
Sci. Forestry, Syracuse, NY. In review.
56. Bull, K.R., R.D. Roberts, M.J. Inskip, and G.T. Goodman. 1977.
Mercury concentrations in soil, grass, earthworms and small mammals
near an industrial emission source. Environm. Pollut. Vol. 12.
57. Ireland, M.P- 1976. Excretion of lead, zinc and calcium by the
earthworm Dendrobaena rubida living in soil contaminated with zinc
and lead. Soil Biology and Biochemistry Vol. 8, No. 5.
58. Ireland, M.P. 1975. The effect of the earthworm Dendrobaena rubida
on the solubility of lead, zinc and calcium in heavy metal con-
taminated soil in Wales. Journal of Soil Science, Vol. 26, No. 3.
60
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/8-80-033
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
COMPENDIUM ON SOLID WASTE MANAGEMENT BY
VERMICOMPOSTING
5. REPORT DATE , .
August 1980 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Camp Dresser & McKee, Inc.
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
tamp Dresser & McKee, Inc.
One Center Plaza
Boston, Massachusetts 02108
10. PROGRAM ELEMENT NO.
73D1C, SOS IB, Task R2.12
11. CONTRACT/GRANT NO.
Contract No. 68-03-2803
12. SPONSORING AGENCY NAME AND ADDRESS
(14. SPONSORING AGENCY CODE
Municipal Environmental Research Laboratory—Cin. .OH Final Report
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: L.A. Ringenbach (513) 684-7871
See EPA Report, "Engineering Assessment of Vermicomposting Municipal
Wastewater Sludges" (in Preparation.)
.BSTRACT
Vermicomposting of municipal solid wastes has been attempted only in the last
five years and there are presently no full-scale operations. This report assesses
the technical and economic feasibility of vermicomposting and is based on several
pilot-scale studies conducted by private entrepreneurs.
The assessment is based on examining facilities and costs for a municipal operation
serving (1) a community of 50,000 persons and (2) a community of about 500,000
persons. Vermicomposting is compared to three other methods of solid waste
management: sanitary landfill, windrow composting, and combustion. Vermi-
composting was estimated to cost about $24 to $32 per ton of waste processed.
This cost is high compared to most other available methods. Additionally, the
market for earthworm castings is not established. Since total process costs,
including revenue from sale of products, are central considerations in the
selection of a preferred solid waste management option, the typical communities
examined in this report have available to them technologies which are more
attractive than vermicomposting.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Refuse Disposal
Earthworms
Composting
Economics
Annelida
Feasibility
Municipal Solid Waste
Disposal
Resource Recovery
Vermicomposting
MSW Processing
Annelida
Technical/Economics
13B
68C
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
69
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
61
I U.S. SOVHW1IS1T rawnK OFMS: <9«-6S?-l&S/«04t
------- |