U.S. Environmental Protection Agency
nvironmental Technology Verification ~*
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www.epa.gov/etv
Environmental and Sustainable Technology Evaluation (ESTE)
Manure Treatment by Anaerobic Digester Technology to
Recover Energy and Reduce Pollutants
June 2007
Impact Statement
Anaerobic digestion of animal manures at large scale animal feeding operations has the
potential to reduce waste loads, control microorganisms, and generate energy and salable
products. Any or all of these potentials can benefit agriculture in the United States because
waste management at large scale feeding operations has become an issue of importance to local
communities. Verification of the performance of digesters will help to develop and broaden the
appeal of digesters to more farms.
Background
The U.S. Environmental Protection Agency's Office of Research and Development (EPA-
ORD) supports Environmental and Sustainable Technology Evaluation (ESTE) to facilitate the
development and commercialization of innovative technologies through performance
verification and information transfer. In part, ESTE is intended to increase the relevance of
Environmental Technology Verification (ETV) program (www.epa.gov/etv) projects to U.S.
EPA program offices and regional offices. These performance verifications will serve the
public by demonstrating performance of commercial technologies in operation. Stringent
quality control measures will be taken to gain credible performance data. Potential customers
will be able to refer to reports of verification to help make decisions regarding purchase and use
of these technologies.
Large scale animal feeding operations commonly known as concentrated animal feeding
operations (CAFOs) generate very large quantities of manure. Most of the manure is spread on
farm land both as a fertilizer and as a disposal mechanism. The major problems associated with
manure relate to odor production and nutrient content. Many soils of the US are overloaded
with phosphorus and adding more from animal manure only makes the problem worse.
Similarly, large scale operations have the potential for generating odors that degrade the quality
of life in nearby areas. There are also questions about the transport of pathogenic organisms
and harmful gases such as hydrogen sulfide from large scale animal waste facilities. Anaerobic
digesters operate in the absence of oxygen and can not be open to the atmosphere. In the
process, degradable organic matter is converted to methane and carbon dioxide. The methane
can be recovered and used to power generators or water heaters on the farm to reduce the
farm's dependence on fossil fuel generated electricity. In most cases, a good digester can
provide enough methane to generate excess electricity that can be sold to the grid, further
reducing the cost of operating a digester. After the digestion process is completed the residual
material has much less odor potential and is reduced in total mass. This material can be further
composted or dried for other uses, thereby making better overall use of the material. Further
processing of the liquid waste stream can recover phosphorus, preventing application of excess
phosphorus to farm fields. These factors can combine to make anaerobic digestion of animal
waste an attractive waste management practice.
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Objective
The objective of this project is to verify the performance of an anaerobic digester in use on a
large scale farm. The work planned will examine several reactor performance parameters.
Reduction of organic solids, methane generation, energy generation, and reduction of
potentially pathogenic microorganisms are included in the measurements planned.
Study Description
Sample collection and analysis will be conducted in accordance with the procedures identified
in the approved Test/QA plan. No less than 12 or no more than 52 sample events will be
performed. The parameters of interest include but are not limited to influent and effluent
analysis of the waste stream for total solids, volatile solids, pH, nitrogen, phosphorus, fecal
coliforms, Escherichia coli, COD, and gas production from the reactor. Gas analysis may be
done to provide gas quality estimation. The content of methane, CO2 and H2S may be
measured. Evaluation of generator performance will be conducted. QA audits will be included
in this part of the work. Planned QA audits will occur before starting the sampling, at the
midpoint and at the end of the sample collection and analysis period. The test site and the
analytical laboratory(ies) will be audited.
An ETV report and verification statement of the evaluation of the anaerobic digester will be
completed after the data are analyzed statistically for the report and statement. A draft report
and statement will be produced for review by the stakeholders group and the QA office.
Comments from the reviewers will be addressed in the final report and statement. Writing the
final report and statement will entail a description of the work performed, a description of the
digester operation, samples analyzed, analytical results, statistical analysis, and estimates of the
value of the methane produced in the digester. The value of the gas produced can be derived
from electrical energy generated during operation and calculation of the cost of an equivalent
amount of natural gas supplied by a natural gas utility. The ETV report and verification
statement will detail operation and maintenance requirements of the system and energy
requirements of the system. The ETV report and verification statement should also estimate
the quantity of phosphorus reduction obtained and how this will impact the ability to land apply
digester waste.
Status
The digester to be evaluated has been selected and a contractor to conduct the sample
collection, analysis, and report writing has been chosen. The actual sample collection should
begin in late June or early July.
Next Step
A conference call with stakeholders, digester operator, and contractor will be convened prior to
beginning sample collection. The plan will be reviewed and final concurrences gathered for the
work.
Contact: John R. Haines, Ph.D.
USEPA-NRMRL
26 W. M.L. King Dr.
Cincinnati, OH 45268
Phone:(513)569-7446
Email: Haines.John@epa.gov
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