United States Environmental Protection Agency   
Solid Waste and Emergency Response (5306W)  
EPA530-F-97-042  
October 1997  
http://www.epa.gov  


        INNOVATIVE USES OF COMPOST BIOREMEDIATION 
                AND POLLUTION PREVENTION  

     Each year agricultural effluents, industrial residues,
and industrial accidents contaminate surface waters, soils,
air, streams, and reservoirs. A new compost technology,
known as compost bioremediation, is currently being used to
restore contaminated soils, manage stormwater, control
odors, and degrade volatile organic compounds (VOCs).

     Compost bioremediation refers to the use of a
biological system of micro-organisms in a mature, cured
compost to sequester or break down contaminants in water or
soil. Micro-organisms consume contaminants in soils, ground
and surface waters, and air. The contaminants are digested,
metabolized, and transformed into humus and inert
byproducts, such as carbon dioxide, water, and salts.
Compost bioremediation has proven effective in degrading or
altering many types of contaminants, such as chlorinated and
nonchlorinated hydrocarbons, woodpreserving chemicals,
solvents, heavy metals, pesticides, petroleum products, and
explosives. Compost used in bioremediation is referred to as
"tailored" or "designed" compost in that it is specially
made to treat specific contaminants at specific sites.

     The ultimate goal in any remediation project is to
return the site to its precontamination condition, which
often includes revegetation to stabilize the treated soil.
In addition to reducing contaminant levels, compost advances
this goal by facilitating plant growth. In this role,
compost provides soil conditioning and also provides
nutrients to a wide variety of vegetation.


SOIL BIOREMEDIATION

Heavy Metal Contamination 

     Dr. Rufus Chaney, a senior research agronomist at the
U.S. Department of Agriculture, is an expert in the use of
compost methods to remediate metal-contaminated sites. In
1979, at a denuded site near the Burle Palmerton zinc
smelter facility in Palmerton, Pennsylvania, Dr. Chaney
began a remediation project to revitalize 4 square miles of
barren soil that had been contaminated with heavy metals.

     Researchers planted Merlin Red Fescue, a metal-tolerant
grass, in lime fertilizer and compost made from a mixture of
municipal wastewater treatment sludge and coal fly ash. The
remediation effort was successful, and the area now supports
a growth of Merlin Red Fescue and Kentucky Bluegrass.

     Chaney has also investigated the use of compost to
bioremediate soils contaminated by lead and other heavy
metals at both urban and rural sites. In Bowie, Maryland,
for example, he found a high percentage of lead in soils
adjacent to houses painted with lead-based paint. To
determine the effectiveness of compost in reducing the
bioavailablility of the lead in these soils, Chaney fed both
the contaminated soils and contaminated soils mixed with
compost to laboratory rats. While both compost and soil
bound the lead, thereby reducing its bioavailability, the
compost-treated soil was more effective than untreated soil.
In fact, the rats exhibited no toxic effects from the
lead-contaminated soil mixed with compost, while rats fed
the untreated soil exhibited some toxic effects.

     In another study, Dr. Lee Daniels and P.D. Schroeder of
Virginia Polytechnic Institute, Blacksburg, Virginia,
remediated a barren site contaminated with sand tailings and
slimes from a heavy mineral mining plant. The application of
yard waste compost revitalized the soil for agricultural
use. The compost was applied at the rates of 20 tons per
acre for corn production and 120 tons per acre for a peanut
crop.


Organic Contaminants 

     Dr. Michael Cole, an expert in the degradation of
organic contaminants in soil, remediated soil containing
3,000 parts-per-million (ppm) of Dicamba herbicide to
nondetectable levels in 50 days. Cole mixed wood chips and
mature compost into soil to make the combined substrate 10
percent (by volume) compost and wood chips and 90 percent
contaminated soil. According to Dr. Cole, Dicamba does
eventually degrade in nonamended soil; however, that process
takes years instead of days. In addition to speeding up the
bioremediation process, use of compost can also save money.
Traditional remediation by landfilling and incineration can
cost up to five times more than bioremediation by composting
technology.

     According to Dr. Cole, compost bioremediation, more
than any other soil cleanup technique, results in an
enriched soil end product and leaves the earth in better
condition than before it was contaminated.


Petroleum Hydrocarbon Contamination 

     Soil at the Seymour Johnson Air Force Base near
Goldsboro, North Carolina, is contaminated as a result of
frequent jet fuel spills and the excavation of underground
oil storage tanks (USTs). Remediation of several sites on
the base is an ongoing project since materials are
continually loaded or removed from USTs, and jets are
continually refueled. The base deals with a variety of
petroleum contaminants, including gasoline, kerosene, fuel
oil, jet fuel, hydraulic fluid, and motor oil.

     In 1994, the base implemented a bioremediation process
using compost made from yard trimmings and turkey manure.
Prior remediation efforts at Seymour involved hauling the
contaminated soil to a brick manufacturer where it was
incinerated at high temperatures. Compared to the costs of
hauling, incinerating, and purchasing clean soil,
bioremediation with compost saved the base $133,000 in the
first year of operation. Compost bioremediation also has
resulted in faster cleanups, since projects are completed in
weeks instead of months.

     The remediation process at Seymour includes spreading
compost on a 50- by 200-foot unused asphalt runway, applying
the contaminated soil, then another layer of compost.
Workers top off the pile with turkey manure. Fungi in the
compost produce a substance that breaks down petroleum
hydrocarbons, enabling bacteria in the compost to metabolize
them. Cleanup managers determine the ratio of soil to
compost to manure, based on soil type, contaminant level,
and the characteristics of the contaminants present. A
typical ratio consists of 75 percent contaminated soil, 20
percent compost, and 5 percent turkey manure. A mechanical
compost turner mixes the layers to keep the piles aerated.
After mixing, a vinyl-coated nylon tarp covers the piles to
protect them from wind and rain, and to maintain the proper
moisture and temperature for optimal microbial growth.


STORMWATER MANAGEMENT

     Stormwater runoff is excess water not absorbed by soil
after heavy rains. It flows over surfaces such as roads,
parking lots, building roofs, driveways, lawns, and gardens.
On its journey to larger bodies of water (streams, lakes,
and rivers), municipal and industrial stormwater can carry a
wide range of potentially harmful environmental
contaminants, such as metals, oil and grease, pesticides,
and fertilizers. These types of contaminants pollute rural
water, damage recreational and commercial fisheries, and
degrade the beauty of affected waterways, among other
things.

     Stormwater runoff must be treated before it is
discharged into water to meet the U.S. Environmental
Protection Agency's National Pollutant Discharge Elimination
System regulations. To comply, some municipalities and
industries are turning to solutions that involve compost
technology instead of more expensive traditional treatment
methods, such as vegetated filter strips or grassy swales
(phytoremediation) and holding ponds. These traditional
methods require much larger tracts of land than methods
utilizing compost and are limited in their removal of
contaminants. In one industrial area, for example, a
traditional holding pond required 3.5 acres and cost
$45,000, while a compost stormwater system, designed to
handle the same amount of runoff, required only 0.5 acre,
required less maintenance, and cost $17,300.


Compost Stormwater Filters 

     The compost stormwater filter (CSF), one type of
bioremediator, is a large cement box with three baffles to
allow water to flow inside. The CSF is designed to remove
floating debris, surface scum, chemical contaminants, and
sediment from stormwater by allowing it to pass through
layers of specially tailored compost. The porous structure
of the compost filters the physical debris while it degrades
the chemical contaminants. Scum baffles along the side of
the unit trap large floating debris and surface films.


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                           Graphic
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     This innovative stormwater filtration and
bioremediation system uses a relatively small volume of
specially tailored compost made from leaves. The compost is
formulated to remove over 90 percent of all solids, 85
percent of oil and grease, and between 82 to 98 percent of
heavy metals from stormwater runoff. A CSF typically has low
operating and maintenance costs and has the ability to treat
large volumes of water up to 8 cubic feet per second. When
the compost filter is no longer effective, it can be
removed, tested, recomposted to further remove any
contaminants, and used in other compost applications, such
as daily landfill cover since the metals are bound by the
compost.


DISPOSAL OF VOCS AND ODOR CONTROL

     Compost bioremediation technologies also have been
developed to remove VOCs that cause disagreeable or harmful
odors in air. The removal process involves passing the
contaminated air through a patented, tailored compost. The
compost functions as an organic medium containing
micro-organisms that digest the organic, odor-causing
compounds. Industrial facilities have made use of this
compost technology to remove VOCs at the 99 percent level.

     Billions of aerosol cans are manufactured and used
annually in the United States in households, businesses, and
industry. Many of these cans carry residues of paints,
lubricants, solvents, cleaners, and other products
containing VOCs. Disposing of used aerosol cans represents a
significant expenditure, both to the communities that
collect them through household hazardous waste programs and
to the businesses and industry that generate, handle, treat,
or store these wastes.


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             Biofiltration vs. Bioremediation 

     Biofiltration implies physically separating
     particles based on their sizes. Bioremediation, by
     contrast, implies a biochemical change as
     contaminants or pollutants are metabolized by
     micro-organisms and broken down into harmless,
     stable constituents, such as carbon dioxide,
     water, and salts.
************************************************************


     Activated carbon is one technology that traditionally
has been employed to treat these cans prior to disposal.
Canisters of carbon are used to physically adsorb VOCs from
the cans. Activated carbon, however, does not destroy the
VOCs, but merely stores them. Thus, once the carbon
canisters become saturated, they, in turn, must be disposed
of. This adsorbtive compost technology is more suitable for
some types of VOC-containing products than is activated
carbon, which is a poor adsorber of acetone.

     Vapor-phase biofilters using compost are gaining
increasing attention as an alternative technology for
treating aerosol cans. This growth is due, in part, to the
high cost of conventional treatment and disposal methods, as
well as to new regulations concerning VOC emissions from
hazardous waste storage tanks and containers. Unlike
conventional VOC control technologies, such as activated
carbon, biofilters actually break down hazardous
contaminants into harmless products. They also offer low
capital, life-cycle, and operating costs and require minimal
maintenance and energy. The energy required to power a 100
cfm airflow unit, according to the manufacturer, is rated at
20 amps. At 8 cents per kilowatt hour, the cost of the
requisite electricity is estimated at $1.80 per day.
Additionally, according to one manufacturer, vapor-phase
biofilters maintain a consistent VOC removal efficiency of
99.6 percent, even when exposed to heavy or uneven surges of
toxics.


Control of Composting Odors

     Rockland County, New York, recently announced
construction of a composting facility with America's first
large, industrial-sized, odor-control bioremediation system.
The enclosed 55,000-square-foot facility will be fitted with
a compost filtration system that can process 82,000 cubic
feet of air per minute. The air will be treated using
ammonia scrubbers, then forced into an enclosure stacked
with compost and other organic materials that function
together as an air filtration system. The system binds
odorous compounds, which the micro-organisms in the compost
then degrade. This system has allowed the Rockland County
Authority to obtain a contractual guarantee of no detectable
odor at or beyond the site property line from the contractor
awarded the design, construction, and operating contract.


Biofilters in Municipal Use

     By converting its disposal operation from strictly
landfilling to one that utilizes a vapor-phase biofilter,
the Metro Central Household Hazardous Waste collection
facility in Portland, Oregon, saved nearly $47,000 in
hazardous waste disposal costs over an 18-month period. The
facility used vapor-phase biofilters to remediate over
38,000 aerosol cans. As a result, it lowered its disposal
costs from $505 per loose-packed drum to $265 per drum (from
$2.35 per can to $1.30), since the cans were no longer
hazardous and did not need to be handled as such.


************************************************************
                Vapor-Phase Biofiltration 

          One application of biofiltration technology
     involves placing punctured cans, contaminated
     rags, or other items in the lower chamber of the
     biofilter. Next, the entire unit is heated to
     vaporize the contaminants. A small amount of air
     is then injected into the system to draw the now
     gaseous contaminants through two separate layers
     of a compost-rich biomatrix. The bulk of the
     contaminants are absorbed by the biomatrix at the
     first level, where most of the microbial activity
     takes place. The upper level serves as a surge
     control layer (to treat heavy or uneven surges of
     VOCs). Micro-organisms living in the biomatrix
     metabolize the absorbed organics as food,
     converting the pollutants into carbon dioxide and
     water vapor.
************************************************************


************************************************************
Benefits and Disadvantages of Using Vapor-Phase Biofilters

     Benefits

     *    Low capital costs
     *    Low operating costs
     *    Limited energy and maintenance requirements
     *    High reliability
     *    Consistent pollutant removal
     *    Consistent destruction rates
     *    No hazardous combustion-related byproducts
     *    Destroys VOCs, and thus does not require
          secondary disposal (unlike activated carbon)

     Disadvantages

     *    Requires consistent loadings
     *    Requires more square footage of space than
          conventional disposal methods
************************************************************


References

Cole, M.A., X. Liu, and L. Zhang. 1995. Effect of compost
addition on pesticide degradation in planted soils. In
Bioremediation of recalcitrant organics. Edited by R.E.
Hinchee, D.B. Anderson, and R.E. Hoeppel. Columbus: Battelle
Press.

Chaney, R.L., and J.A. Ryan. 1994. Risk based standards for
arsenic, lead, and cadmium on urban soils. Frankfort:
Dechema.

Chaney, R.L. et al. Phytoremediation potential of Thlaspi
caerulescens and bladder campion for zinc-and-cadmium-
contaminated soil. Journal of Environmental Quality. 23:
1151-1157.

Fordham, Wayne. 1995. Yard trimmings composting in the Air
Force. Biocycle. 36: 44.

Garland, G.A., T.A. Grist, and R.E. Green. 1995. The compost
story: From soil enrichment to pollution remediation.
Biocycle. 36: 53-56.

Schroeder, Philip D. 1997. Restoration of prime farm land
disturbed by mineral sand mining in the upper coastal plains
of Virginia. Master's Thesis, Virginia Tech.

Stewart, W.C., and R.R. Thom. 1997. Test results and
economics of using an innovative, high-rate, vapor-phase
biofilter in industrial applications. Portland. Typeset.

Stewart, W.C. 1994. Compost stormwater filter engineering
system. Environmental Excellence Award and Innovator of the
Year Award Presented by the Association of Washington State
Business. Mimeographed.


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