United States
                         Environmental Protection
                         Biosolids Technology Fact Sheet
                         Use of Composting for Biosolids Management
Composting is one of several methods for treating
biosolids to create a marketable end product that is
easy to handle, store, and use. The end product is
usually a Class A, humus-like material without
detectable levels of pathogens that can be applied as
a soil conditioner and fertilizer to gardens, food and
feed crops, and rangelands. This compost provides
large quantities of organic matter and  nutrients
(such  as nitrogen  and potassium) to the soil,
improves soil  texture,  and  elevates soil  cation
exchange capacity (an indication of the soil's ability
to hold nutrients),  all characteristics of a good
organic fertilizer. Biosolids compost is safe to use
and generally has a high degree of acceptability by
the public.  Thus, it competes well with other bulk
and bagged products available  to homeowners,
landscapers, farmers, and ranchers.

Three methods of composting wastewater residuals
into biosolids are common. Each method involves
mixing dewatered wastewater solids with a bulking
agent to provide carbon and increase porosity. The
resulting  mixture is piled or placed in a vessel
where microbial activity causes the temperature of
the mixture to rise during the "active composting"
period.  The specific temperatures that must be
achieved and maintained for successful composting
vary based on the  method and use of the end
product.  After active composting, the material is
cured and  distributed.   The three commonly
employed composting methods are described in the
following paragraphs. A fourth  method (static
pile)  is   not  recommended for  composting
wastewater solids based on a lack of operational

Aerated   Static  Pile  -  Dewatered  cake  is
mechanically  mixed  with a  bulking agent and
stacked into long piles over a bed of pipes through
which air is transferred to the composting material.
After active composting, as the pile is starting to
cool down, the material is moved into a curing pile.
                                 Yard Trimmings,
                             Source-separated organics,
                                  or Mixed MSW
                 Blanket of
             Finished Compost
                6-12 inches
                                                    Aeration Pipe
         Odor Filter

Source: Hickman, 1999.


The bulking agent is often reused in this composting
method and may be screened before or after curing
so that it can be reused.

Windrow - Dewatered wastewater solids are mixed
with bulking agent and piled in long rows. Because
there is no piping to supply air to the piles, they are
mechanically turned  to  increase the amount  of
oxygen. This periodic mixing is essential to move
outer  surfaces  of material inward  so they are
subjected to the higher temperatures deeper in the
pile.  A number of turning devices are available,
including:  (1)  drums  and  belts  powered  by
agricultural equipment and pushed or pulled through
the composting pile; and (2) self-propelled models
that straddle the composting pile.  As with aerated
static  pile composting, the material is moved into
curing piles after active composting. Several rows
may be laced into a larger pile for curing. Figure 2
shows a typical windrow operation.
Source: Parsons, 2002.


In-Vessel - A mixture of dewatered wastewater
solids and bulking agent is fed into a silo, tunnel,
channel,  or vessel.  Augers, conveyors, rams, or
other devices are used to aerate, mix, and move the
product through the vessel to the discharge point.
Air is  generally blown into the mixture.  After
active composting, the finished product is usually
stored  in a  pile  for additional  curing  prior to
distribution.  A typical composting vessel is shown
in Figure 3. This technology is discussed in greater
detail   in  the   fact  sheet  entitled  In-Vessel
 Source: Parsons, 2002.


Composting ofBiosolids (EPA 832-F-00-061).

All three composting methods require the use of
bulking agents, but the type of agent varies. Wood
chips, saw dust, and shredded tires are commonly
used, but many other materials are suitable.  The
U.S  Composting  Council  lists  the following
materials as suitable for use as  bulking agents:

      Agricultural by-products, such as  manure
       and bedding from various animals, animal
       mortalities, and crop residues.

      Yard trimmings, including grass clippings,
       leaves, weeds, stumps, twigs, tree prunings,
       Christmas trees,  and  other  vegetative
       matter from land clearing activities.

       Food by-products, including damaged fruits
       and vegetables, coffee grounds,  peanut
       hulls, egg shells, and fish residues.

       Industrial   by-products   from   wood
       processing,   forestry,  brewery   and
       pharmaceutical operations.  Paper goods,

       paper mill residues,  and  biodegradable
       packaging materials are also used.

       Municipal solid waste.

If municipal solid waste is used in compost, it is put
through a mechanical separation process prior to its
use to remove  non-biodegradable  items such as
glass, plastics and certain paper  goods (USCC,

The length of time biosolids are composted at a
specific temperature is important in determining the
eventual use of the compost end product. 40 CFR
Part 503, Standards for  the  Use and Disposal of
Sewage Sludge  (Part  503) defines time  and
temperature requirements for both Class A and
Class B products (Table 1).  The production of a
Class B product is not always economically justified
since the product cannot be used without restrictions
and the  additional  expense to reach Class A
requirements can be marginal.

       TABLE 1 PART 503 TIME AND
Regulatory Requirements
 Class A   Aerated static pile or in-vessel:
           55 C for at least 3 days
           Windrow: 55 C for at least 15
           days with 5 turns

 Class B   40 C or higher for five days during
           which temperature exceed 55 C
 	for at least four hours	
 Source:  40 CFR Part 503.
If the compost process conforms with the time and
temperature requirements to produce  a Class  A
product and the maximum pollutant levels of Part
503 are met, the material is considered "Exceptional
Quality" (EQ) biosolids. If used in accordance with
sound agronomic and horticultural practices, an EQ
biosolids product can be sold in bags or bulk and
can be used in household gardens without additional
regulatory  controls.  Class A  and EQ biosolids
typically have greater marketing success than Class
B biosolids. Control of industrial waste streams to
wastewater treatment plants (through pretreatment
programs) greatly reduces the presence of metals in
pre-processed  wastewater residuals,   enabling
compost to meet the stringent EQ standards of Part

If the compost produced is Class B, it can be used
at agronomic sites with no public  contact,  with
additional site restrictions. Class A biosolids can
be used in home gardens with public contact and
no  site  restrictions.  Consistent and predictable
product quality  is  a key factor  affecting the
marketability of compost (U.S.  EPA,  1994).
Successful marketing depends  on a  consistent
product quality.

Stability is an important characteristic  of a good
quality compost.  Stability is defined as the level of
biological activity in the compost and is measured
as oxygen uptake or carbon dioxide production.
Oxygen uptake  rates  of 50 to  80 mg/L are
indicative of  a  stable product with  minimal
potential for self-heating, malodor generation,  or
regrowth of pathogen populations. Stability is also
indicated  by  temperature  decline,  ammonia
concentrations, chemical oxygen demand (COD),
number of insect eggs, change in odor, and change
in redox potential (Haug, 1993).

Stable   compost  consumes  little  nitrogen and
oxygen  and  generates  little  carbon  dioxide.
Unstable compost consumes nitrogen and oxygen
and  generates  heat, carbon  dioxide, and water
vapor.   Therefore, when unstable compost  is
applied  to soil, it removes nitrogen from the soil,
causing  a  nitrogen  deficiency  that  can be
detrimental to plant growth  and survival.   In
addition,  if not  aerated  and stored  properly,
unstable  compost  can  emit  nuisance   odors
(Epstein, 1998, Garcia,  1991).


The physical characteristics  of most biosolids
allow for their successful composting.  However,
many characteristics (including moisture content,
volatile solids  content, carbon content, nitrogen
content, and bulk density) will impact  design
decisions  for  the composting  method.   Both
digested and raw solids can be composted, but

some degree of digestion (or similar stabilization) is
desirable to reduce the potential for generation of
foul odors from the composting operation.  This is
particularly  important for aerated static pile and
windrow operations.  Carbon and nitrogen content
of the wastewater solids must be balanced against
that  of the  bulking  agent to  achieve  a suitable
carbon to nitrogen ratio of between 25 and 35 parts
carbon to one part nitrogen.

Site characteristics make composting more suitable
for some wastewater treatment plants than  others.
An adequate buffer zone from neighboring residents
is  desirable to reduce  the potential for nuisance
complaints.  In urban  and suburban settings, in-
vessel technology may be more suitable than other
composting technologies  because  the  in-vessel
method allows for containment and treatment of air
to  remove odors before release. The requirement
for a relatively small amount of land also increases
the applicability of in-vessel composting in these

Another important consideration before selecting
the technology to be used for composting  is the
availability  of adequate and  suitable manpower.
Composting is typically labor-intensive for  the
following reasons:

       Bulking agents must be added.

       Turning, monitoring,  or process control is

      Feed  and finished material(s)  must  be
       moved with mechanical equipment.

       Storage piles must be maintained for curing
       and distribution.

      Bulking agents recovery adds another step.

Finally, proximity to the markets for the resulting
compost is desirable, although the usefulness of the
final product in home gardening and commercial
operations generally makes the material marketable
in  urban as well as rural areas.  This is especially
true for good quality material that does not emit foul

Biosolids composting has grown in popularity for
the following reasons (WEF, 1995):

       Lack of availability of landfill space for
       solids disposal.

      Composting economics are more favorable
       when landfill tipping fees escalate.

       Emphasis on beneficial  reuse at federal,
       state, and local levels.

      Ease  of  storage, handling,  and  use  of
       composted product.

       Addition  of biosolids compost  to soil
       increases the soil's phosphorus, potassium,
       nitrogen,  and organic carbon content.

Composted biosolids can also be used in various
land  applications.     Compost   mixed  with
appropriate additives creates a material useful in
wetland and  mine land restoration.   The high
organic matter content and low nitrogen  content
common in compost provides a strong organic
substrate that mimics  wetland  soils,  prevents
overloading of nitrogen, and adsorbs ammonium to
prevent transport to adjacent surface waters (Peot,
1998).   Compost  amended  strip-mine  spoils
produce a sustainable cover of appropriate grasses,
in contrast  to inorganic-only amendments which
seldom provide such a good or sustainable cover
(Sopper, 1993).

Compost-enriched  soil  can also  help  suppress
diseases and ward off pests.  These beneficial uses
of compost can help growers save money, reduce
use of pesticides, and conserve natural resources.
Compost also plays a role in bioremediation of
hazardous sites and pollution prevention. Compost
has proven effective in degrading or altering many
types of contaminants, such as wood-preservatives,
solvents, heavy metals, pesticides,  petroleum
products, and explosives. Some municipalities are
using compost to filter stormwater runoff before it
is discharged to remove  hazardous  chemicals
picked up when  stormwater flows over surfaces
such as roads, parking lots, and lawns. Additional

uses for compost include soil  mulch for erosion
control, silviculture crop establishment, and sod
production media (U.S. EPA, 1997a).

Limitations of biosolids composting may include:

      Odor production at the composting site.

      Survival and presence of primary pathogens
       in the product.

       Dispersion of secondary pathogens such as
       Aspergillus Jumigatus,  particulate matter,
       other airborne allergens.

       Lack of consistency in product quality with
       reference to metals, stability, and maturity.

Odors  from a  composting  operation  can  be a
nuisance and a potential irritant.  Offensive  odors
from composting sites are the  primary source of
public opposition to composting and have led to the
closing  of  several   otherwise   well-operated
composting facilities. Although research shows that
biosolids odors may not pose a health threat,  odors
from processing facilities have decreased public
support for biosolids recycling  programs (Toffey,
1999).   Many  experts in  the  field of biosolids
recycling  believe that biosolids generating and
processing facilities have an ethical responsibility to
control odors and  protect  nearby residents from
exposure to malodor.

Composting odors are  caused by ammonia, amine,
sulfur-based compounds, fatty acids, aromatics, and
hydrocarbons (such as terpenes) from  the  wood
products used as bulking agents (Walker, 1992). A
properly designed composting plant, such as the one
shown in Figure 4, operated at a  high positive redox
potential  (highly aerobic) will reduce, but not
necessarily eliminate,  odors and  odor  causing
compounds during the first 10 to 14 days of the
process (Epstein,  1998).   Control of  odors is
addressed in further detail in the fact sheet entitled
Odor Management in Biosolids Management (EPA

In addition to odors,  other bioaerosols, such as
pathogens, endotoxins, and various volatile organic
compounds, must also  be controlled. Biofilters are
often used to control  odors, but the biofilters
themselves can give off bioaerosols.

Pathogens, such as bacteria, viruses, and parasites
(helminth and protozoa), are present in untreated
wastewater  residuals.   These organisms can
potentially invade a normal, healthy human being
and produce illness  or debilitation.  Composting
reduces  bacterial  and   viral  pathogens   to
non-detectable levels if the temperature  of the
compost is maintained at greater than 55 C for  15
days  or  more.     Additionally,  it has  been
demonstrated that viruses and helminth ova do not
regrow after thermal inactivation (Hay, 1996).

Regrowth of Salmonella sp. in composted biosolids
is  a  concern,  although  research  shows that
salmonellae reach a quick  peak during regrowth,
then die off. Composting is not a sterilization
process  and a   properly  composted  product
maintains  an active  population  of beneficial
microorganisms   that   compete   against the
pathogenic members.   Under some conditions,
explosive regrowth of pathogenic microorganisms
is possible. A stabilized product with strict control
Source: Parsons, 2002.


of  post-composting handling  and  addition  of
amendments  coupled with four to  six weeks of
storage will mitigate Salmonella regrowth (Hay,

Compost workers may be exposed to a common
fungus known as Aspergillusfumigatus, endotoxins,
or other  allergens.   A. fumigatus is common in
decaying organic matter and soil.  Inhalation of its
airborne spores causes skin rashes and burning eyes.
While healthy  individuals  may not be affected,
immunocompromised individuals may be  at risk.
The spores of A. fumigatus are ubiquitous and the
low risk of exposure is  not  a significant health
concern.   However, spore  counts at composting
facilities are  high, and the risk of operators  and
persons  handling  composted  biosolids   being
exposed to these spores is also high (Epstein, 1998).
Inhalation of spores, particulates, and other matter
can be reduced or prevented by:

       Wearing masks and other protective devices.

       Equipping front end loaders with filters or
       air conditioners.

       Thoroughly ventilating composting  halls.

       Installing biofilters or other odor scrubbing
       systems in composting halls (Epstein 1998).

Organic dust (such  as pollen) is another nuisance
that must be  controlled at composting operations.
These contaminants are  primarily  a  concern to
workers  at the composting  facilities  and  are
generally not present in quantities that would cause
reactions in most individuals that are not exposed
outside of the facilities.

Environmental Impact

Potential environmental impacts may result from
both composting operations and use of the compost
Composting Process

Dust and airborne particles from a composting
operation may affect air quality.  The impact to
adjacent  areas  may  need to be mitigated  and

To protect area ecology and water quality, run-off
from application sites must be controlled.   The
potential nitrogen and phosphorus rich run-off (or
leachate) can cause algal growth in surface water
and  render groundwater  unfit   for   human

Land Application of Compost Products

Excess nitrogen is detrimental to soil, plants, and
water,  so care must be taken  when  choosing
application sites, selecting plant/crop types,  and
calculating the agronomic rate for biosolids land
application.   It should be  noted that the most
plant-available  form  of nitrogen in biosolids
(ammonium ion (NH4+)) is  converted to nitrate
(NO3") by the composting process. Improper use of
biosolids can result in the contamination  of water
resources with leached nitrogen, because nitrate is
more mobile than ammonium, and is taken up less
easily by plants. However, applying compost in
accordance with the  Part 503 Regulations poses
little risk to the  environment  or public health
(Fermante, 1997). In fact, the use of compost can
have a positive impact on  the  environment in
addition  to the soil improving characteristics
previously discussed.  Reduced dependence on
inorganic fertilizers  can significantly  decrease
nitrate contamination of ground and surface waters
often associated with use of inorganic fertilizers.


Composting  is a  viable, beneficial  option in
biosolids management.  It is a proven method for
pathogen  reduction  and results in a  valuable
product.  According to a 1998 survey in Biocycle,
The Journal of Composting and Recycling,  274
biosolids composting facilities were operating in
the United States (Goldstein, 1999).  Nearly 50
additional facilities  were in various  stages of
planning,  design,  and construction.   A large

number of these facilities (over 40 percent) use the
aerated static pile composting method.

Since 1984, EPA has encouraged the beneficial use
of wastewater  residuals through formal policy
statements.   The  implementation  of Part 503
enhanced the acceptance of biosolids as a resource
by standardizing metal and pathogen concentrations.
Moreover, Part 503 officially identifies composting
as a method to control pathogens and reduce vector

Discussions  of the  specific performance factors of
the three primary composting methods are provided

Aerated static  pile systems  are adaptable and
flexible to bulking agents  and production rates.
Aerated static pile is mechanically simple, thus with
lower  maintenance  than   other  cost  method.
Conversely,   this  configuration  can  be  labor
intensive and may produce nuisance odors and dust.
Cover, negative aeration, chemically scrubbing, or
use of a well-maintained biofilter may be required
to minimize off-site odor migration. The popularity
of the aerated static pile method is based on the ease
of design  and operation and lower capital costs
associated with facility construction.  Selection of
an appropriate method requires an assessment of the
physical   facility,  process  considerations,  and
operation and maintenance costs (WEF, 1995).

Windrow composting is adaptable,  flexible and
relatively  mechanically  simple.   However,  the
windrow configuration requires a large area and can
result in release of malodor, dust, and other airborne
particles  to  the  environment  during  natural
processing, ventilation, and windrow turning.

In-vessel systems  are less adaptable and flexible
compared with aerated static  pile and windrow
systems. However, in-vessel composting requires a
smaller area.  Because the reactor is completely
enclosed, the potential for odor and the need for
controls is increased.  Due to the greater complexity
of in-vessel  mechanical  systems, trouble can  be
encountered meeting peak flows,  breakdowns are
more frequent,  and repairs are more difficult and
costly. Failure of aeration devices, under- designed
aeration systems, or  lack of  a back-up  aeration
method may cause large quantities of product to
become anaerobic,  and therefore,  unacceptable.
Often the compost residence time in in-vessel
composting systems is inadequate to produce a
stable product, particularly where the depth of the
composting mass is great, (e.g., more than 3 m [10
feet]) and mixing does not occur.  In addition,
bridging sometimes occurs within these  systems.
Finally, depending  upon  the  configuration  and
direction of air flow, the worker environment can
be very hostile.  However, in-vessel composting
requires a smaller area and generates relatively
little dust outside the facility.

Table 2 compares the three methods and highlights
key features of each.


The capital costs of aerated static pile or windrow
configuration  may  be  lower  than  in-vessel
composting  configurations, but  costs  increase
markedly when cover is required to control odors.
More highly  mechanized  in-vessel systems are
often more costly to construct, but tend to be less
labor intensive.   On the  other  hand, in-vessel
systems tend to be less flexible in their ability to
adapt to changing  properties of  biosolids  and
bulking agent feedstocks.

Capital  costs  of in-vessel systems range from
$33,000 to $83,000 per dry metric ton ($30,000 to
$75,000 per dry ton) per day processing capacity.
A typical  aerated  static  pile   facility  costs
approximately $33,000 per dry metric ton ($30,000
per  dry ton)  per  day  of  processing  capacity
(Harkness, 1994; U.S. EPA, 1989).

Typical operation and maintenance (O&M) costs
for in-vessel systems range from $150 per dry ton
per day to greater than $200 per dry ton per day.
Aerated static  pile O&M costs average $150 per
dry ton per day (Harkness, 1994; U.S. EPA, 1989).
 Costs for windrow systems fall between the costs
for in-vessel and aerated static pile.  The selling
price for compost ranges from $5 to $10 per cubic
yard or $10 to $20 per ton.  Some facilities allow
landscapers and homeowners to pick up  compost
for little or no charge.

 Aerated Static Pile
  Highly affected by weather (can
  be lessened by covering, but at
  increased cost)

  Extensive operating history both
  small and large scale

  Large volume of bulking agent
  required, leading to large volume
  of material to handle at each
  stage (including final distribution)

  Adaptable to changes in biosolids
  and bulking agent characteristics
 Wide-ranging capital cost

 Moderate labor requirements

 Large land area required

 Large volumes of air to be treated
 for odor control
  Moderately dependent on
  mechanical equipment

  Moderate energy requirement
Highly affected by weather (can
be lessened by covering, but at
increased cost)

Proven technology on small scale
Large volume of bulking agent
required, leading to large volume
of material to handle at each
stage (including final distribution)

Adaptable to changes in biosolids
and bulking  agent characteristics
Low capital costs

Labor intensive

Large land area required

High potential for odor generation
during turning; difficult to
capture/contain air for treatment

Minimally dependent on
mechanical equipment

Low energy requirements	
Only slightly affected by weather
Relatively short operating history
compared to other methods

High biosolids to bulking agent
ratio so less volume of material to
handle at each stage
Sensitive to changes in
characteristics of biosolids and
bulking agents

High capital costs

Not labor intensive

Small land area adequate

Small volume of process air that is
more easily captured for treatment

Highly dependent on mechanical

Moderate energy requirement
 Source: Parsons, 2002.

Other Related Fact Sheets

In-Vessel Composting of Biosolids
EPA 832-F-00-061
September 2000

Odor Management in Biosolids Management
EPA 832-F-00-067
September 2000

Centrifuge Thickening and Dewatering
EPA 832-F-00-053
September 2000
Belt Filter Press
EPA 832-F-00-057
September 2000
                 Other EPA  Fact  Sheets can  be found  at the
                 following web address:


                 1.     40 Code of Federal Regulations, Part 503,
                        Standards for the Use and  Disposal of
                        Sewage Sludge.

                 2.     Benedict, A.H., E. Epstein, and J. Alpert,
                        1987.  Composting Municipal Sludge: A
                        Technology    Evaluation.
                        EPA/600/2-87/021,  Water   Engineering
                        Research Laboratory, Office  of Research
                        and  Development, U.S.  Environmental
                        Protection Agency, Cincinnati, Ohio.

                 3.     Burkhardt, J.W., W.M. Miller, and M.
                        Azad, 1993.   "Biosolids Application to

      Rangelands."   Water  Environment and    16.
      Technology, 5(5):68-71.

4.     Epstein, E.,  1998. Design and Operations
      of Composting Facilities:  Public Health
      Aspect, http://www.rdptech.com/tchl5.htm,
      accessed 2002.

5.     Fermante, Jon V. and Meggan Janes, 1997.    17.
      "Managing  Biosolids   Through
      Composting."  Pollution   Engineering,

6.     Garcia,  C.,  T. Hernandez, and F. Costa,
      1991. "The Influence of Composting on the
      Fertilizing Value of an Aerobic Sewage    18.
      Sludge." Plant and Soil, 136:269-272.

7.     Harkness, G.E, C.C. Reed, C.J. Voss, C.I.
      Kunihiro,  1994. "Composting in the Magic
      Kingdom."    Water Environment  and
      Technology, 6(8): 64-67.
8.     Haug, R. T., 1993.  The Practical Handbook
      of Compost Engineering. Lewis Publishers,
      Boca Raton, FL

9.     Hay, J.C., 1996. "Pathogen Destruction and
      Biosolids Composting." BioCycle, Journal
      of Waste Recycling, 37(6):67-72.
10.    Hickman  Jr.,  H.  Lanier,   1999.   The    21.
      Principles  of  Integrated  Solid  Waste
      Management.   American  Academy  of
      Environmental Engineers, Annapolis, MD.

11.    Millner, P.O., et al., 1994.   "Bioaerosols
      Associated with Composting Facilities."
      Compost Science and Utilization 2:No.4,    22.
      Autumn 1994.

14.    Nevada   Division   of  Environmental
      Protection, 1995.   Program Statement:
      Biosolids  Reuse and Domestic Sewage
      Sludge Disposal. Bureau of Water Pollution    23.
      Control. Ver. 2.1.

15.    Parsons, 2002. Various materials.
Peot, C., 1998. "Compost Use in Wetland
Restoration:   Design   for   Success."
published  in  proceedings  of The  12th
Annual  Residuals   and  Biosolids
Management  Conference.     Water
Environment   Federation,  Alexandria,

Roe, N.E., P.J.  Stoffella, and D. Graetz,
1997. "Composts from Various Municipal
Solid Waste Feedstocks Affect Vegetable
Crops,  Part I: Emergence and Seedling
Growth." Journal of the American Society
of Horticultural Science, 122(3 ): 427-43 2.

Roe, N.E., P.J.  Stoffella, and D. Graetz,
1997. "Composts from Various Municipal
Solid Waste Feedstocks Affect Vegetable
Crops,  Part II: Growth,  Yields, and Fruit
Quality." Journal of the American Society
of Horticultural Science, 122(3):433-437.

Sopper, W.E., 1993. Municipal Sludge Use
In Land Reclamation.  Lewis Publishers,
Boca Raton, Florida.

United States  Composting Council, 2000.
Field  Guide  to Compost  Use.    U.S.
Composting Council,  Hauppauge, New

U.S. EPA,  1985.   Technology Transfer
Seminar Publication for Composting of
Municipal  Wastewater   Sludges.
EPA/625/4-85/014. U.S. EPA Center for
Environmental  Research  Information,
Cincinnati, Ohio.

U.S. EPA,  1989.   Summary Report for
In-Vessel   Composting  of  Municipal
Wastewater Sludge.  EPA/625/8-89/016.
U.S.  EPA Center for  Environmental
Research Information, Cincinnati, Ohio.

U.S.   EPA,   1992.      Environmental
Regulations and Technology Manual for
Control  of  Pathogens  and   Vector
Attraction   in   Sewage   Sludge.
EPA/625/R-92/013.  Office of Research

       and Development, U.S. EPA, Washington,

24.    U.S.  EPA,   1994.    Composting  Yard
       Trimmings and Municipal  Solid  Waste.
       EPA/530-R-94-003.  Office of Solid Waste
       and  Emergency  Response,  U.S.  EPA,
       Washington, D.C.

25.    U.S. EPA,  1997a.   Innovative Uses of
       Compost: Disease Control for Plants and
       Animals.  EPA/530-F-97-044.   Office of
       Solid Waste and Emergency Response, U.S.
       EPA, Washington, D.C.

26.    U.S. EPA,  1997b.   Innovative Uses of
       Compost: Bioremediation and Pollution
       Prevention.  EPA/530-F-97-042. Office of
       Solid Waste and Emergency Response, U.S.
       EPA, Washington, D.C.

27.    Walker,  John M.,  1992.   "Control of
       Composting  Odors."     Science   and
       Engineering  of  Composting:  Design,
       Environmental,   Microbiological   and
       Utilization Aspects.   Published by Ohio
       Agricultural  Research and  Development
       Center,  Ohio State  University, Wooster,

28.    Water   Environment  Federation,   1995.
       Wastewater  Residuals  Stabilization.
       Manual   of Practice  FD-9.    Water
       Environment  Federation,  Alexandria,

29.    Williams, T., R.A. Boyette, E.  Epstein, S.
       Plett, and C. Poe., 1996.   "The Big and
       Small of Biosolids Composting." BioCycle,
       Journal of Waste Recycling, 37(4):62-69.

Chuck Murray
Chief of Plant Operations
Washington Suburban Sanitation Commission
14501 Sweitzer Lane
Laurel, Maryland 20707

R. Tim Haug
Deputy City Engineer, Wastewater
Dept. of Public Works, Bureau of Engineering
650 South Spring Street, Suite 200
Los Angeles, California 90014-1911

United States Composting Council
200 Parkway Drive South, Suite 310
Hauppauge, New York 11788

John Walker, PhD
Mail Code 4204
1200 Pennsylvania Avenue, NW
Washington, DC 20460

The  mention of trade names  or commercial
products  does not constitute  endorsement or
recommendation for use by the U. S. Environmental
Protection Agency.

               Office of Water
             EPA 832-F-02-024
              September 2002

       For more information contact:

       Municipal Technology Branch
       U.S. EPA
       Mail Code 4204M
        1200 Pennsylvania Ave, NW
       Washington, D.C. 20460
                                                                 * 2002 *
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