SIERRA CLUB
GUIDANCE: METHANE DIGESTERS AND CONCENTRATED ANIMAL FEEDING OPERATION (CAFO )
WASTE (Oct 20, 2004)
INTRODUCTION:
The use of methane digesters
to produce energy from animal manure may have a role in addressing environmental
problems and meeting energy needs, but the Sierra Club opposes public subsidies
to such energy generation at large concentrated animal feeding operations
(CAFOs) because of the environmental and social damage associated with them: polluting
our waters and our air; excessive use of antibiotics and hormones; mistreatment
of animals; and harming rural communities and small farms.
METHANE
DIGESTERS: WHAT ARE THEY?
Methane digesters are anaerobic (low or no oxygen) chambers
which facilitate the breakdown of manure by anaerobic bacteria with the release
of methane and other gases as a byproduct of their metabolism, ammonia, nitrogen,
hydrogen sulfide, and sulfur dioxide. Methane can be burned directly
in stoves or burners, to heat the digester, and it can be converted to electricity.
There are several different types of systems but all commercially available
systems are expensive to install and require manure from a large number of
animals to operate. (Fulhage et al. 1993)
IS THERE A ROLE FOR METHANE DIGESTERS ON SMALL FARMS?
The purpose of this policy
is to address the use of methane digesters to handle animal waste generated
by concentrated animal feeding operations (CAFOs), as that term is used in
the Clean Water Act. However, it is
also necessary to consider the use of methane digesters on farms with livestock
that are not CAFOs. This may include
farms with large numbers of animal units but with enough pasture (the animals
go to the feed) so that it is not
an “animal feeding operation” (AFO – the feed is brought to the animal). It may also include farm operation where the
animals are confined but where the number of animal units is below the regulatory
definition of a CAFO. The Sierra Club
believes that large farms with sufficient pasture are unlikely candidates
for methane digesters. Therefore,
this policy will use the term “small farms” to describe farms that are not
CAFOs.
There is some evidence
that methane digesters can offer significant manure management benefits for
small farm operations (U.S. EPA Office of Air and Radiation, Spring 2002). Digesters
can substantially reduce odor and releases of methane, a powerful global-warming
gas; can convert nitrogen into ammonium, a form more available to plants and
less likely to be carried away with runoff when the remaining waste solids
are land-applied; can reduce fly infestation; and can reduce the oxygen-depletion
capacity of the remaining waste although the liquid waste does still
require additional treatment prior to release.
On the other hand,
the land application of manure is the most environmentally responsible method
of manure management where there is sufficient land to insure that manure
application will not exceed soil absorption capacity and crop and pasture
nutrient needs and where the land application practices do not cause a nuisance.
Therefore, the Sierra Club will consider the role of methane digesters on
small farms as requiring a case-by-case evaluation. The use of public money to subsidize methane digesters
on small farms requires public participation, community support, transparency
and accountability.
DO DIGESTERS MITIGATE THE ENVIRONMENTAL IMPACTS OF CAFOS?
CAFO waste streams
are so large and contaminated that methane digesters mitigate only a small
fraction of their environmental damage. Equipment costs (U.S.
EPA Office of Air and Radiation, Winter 2002) and maintenance for conversion
to energy are high. The biogas must have ammonia, moisture, and particulate
pollution (dust) removed, and then be compressed. It requires additional cleaning if it is to be
sent into a natural gas pipeline.
Most environmental damage caused
by CAFOs, however, remains unabated. Excess nutrients which run off from waste
lagoons or land-applied waste residuals suffocate the life out of our waters.
The volume of solid waste remaining is not significantly diminished and requires
proper disposal (Iowa State University et al. 2002). The solid waste is often
land applied as "fertilizer" or "soil conditioner" but
can pose problems because anaerobic digestion does not remove antibiotics
and heavy metals passed by dosed swine and poultry. In addition,
although pathogen numbers decrease, the decrease may be ephemeral as the pathogens
regrow (Gibbs et al. 1997). Numerous studies have demonstrated that
these toxic and pathogenic contaminants are entering the environment in substantial
concentrations (Giger et al. 2003, Huang et al. 2001, Kolpin et al. 2002,
Union of Concerned Scientists et al. 2002). Further, digesters pose a risk
of explosion and create both nitrogenous and sulfurous gases which may be
emitted. In sum, the potential for methane digesters to
partially mitigate some of the extensive and pervasive damage caused by CAFOs
does not justify the use of this technology as a basis to support the development
of new CAFOs. Existing CAFOs may reduce
the problems they are currently causing by use of methane digesters.
However, they should be installed at the cost of the CAFO
owner and not from public subsidy.
HOW CAN THIS TECHNOLOGY BE UTILIZED
ON SMALLER FARMS?
While focusing primarily on serving
CAFOs, the joint US EPA - USDS - DOE AgStar program and a number of commercial
providers have assisted in the development and installation of digesters
on smaller farms. Where methane digesters are able to operate
on small, non-CAFO operations where antibiotic use is limited to treatment
of disease rather than to promote faster weight gain, where animals are free
of growth hormones, and where toxic and pathogenic byproducts of the digesters
are controlled, there is a potential for methane digesters to provide beneficial
waste treatment. In such situations we should seriously consider supporting
smaller farms which are working towards adopting these potentially sustainable
practices by ensuring that they have fair access to methane digester technology.
HOW ARE METHANE
DIGESTERS REGULATED?
The federal AgStar program is aimed
at reducing greenhouse gases and providing energy while protecting the environment.
AgStar has developed interim standards, presently voluntary, for the
construction and operation of several types of manure digesters. (USDA-NRCS
Biogas Interim Standards). Though these federal standards require
compliance with local and state regulations, the adequacy and thoroughness
of local and state regulations varies substantially across the nation and
some states do not address digester operations at all (Iowa State University
et al. 2002). This is not enough environmental protection. The
Sierra Club wants the standards to become mandatory, inspections to be routine,
and enforcement to be effective. We want testing and limits protective of
natural resources, human health, and human quality of life to be set for metals,
antibiotics, hormones, pathogens, odor-producing and air borne compounds,
and other pollutants released from digester effluent, residual sludge,
solid waste fertilizer, and other byproducts of both CAFOs and methane digesters.
SHOULD CAFO-DERIVED METHANE GAS BE INCLUDED
IN A RENEWABLE ENERGY PORTFOLIO?
NO. A fuel that
damages the environment is not "renewable". The
anaerobic decomposition of CAFO manure, like the decomposition of garbage
in landfills, and waste-burning incinerators, is symptomatic of inefficient
waste treatment, treatment necessitated by inefficient, wasteful industries,
practices, and processes. The Sierra Club favors conservation of materials
and energy, energy efficiency in processes and operations, and the recycling
of materials over the thermal destruction of materials for their energy
content. Small farms which utilize land sufficient to support the number
of animals being raised can be operated so that the land, air, and water
are not degraded and the waste can be recycled into the soil rather than
accumulating and decomposing via the methane-generating anaerobic process.
CAFO waste lagoons and landfills release heat, a waste of thermal energy
and methane, a waste of chemical energy. Capturing energy from
these processes reduces some of the environmental damage associated with these
wasteful and inefficient systems but it doesn't move us towards a clean, renewable
energy future which must be built upon conservation, efficiency, and material
recycling.
SHOULD DIGESTERS BE SUBSIDIZED?
Subsidies for energy production from
digesters have become a frequent provision in energy legislation. Some fossil
fuel use may be displaced by methane digesters but it is a small amount. Similarly,
some global warming gas emissions are reduced by the use of digesters
but CAFOs are a minor contributor overall (U.S. EPA, April 2004).
The benefits of methane digesters in terms of energy policy are small
so subsidies for CAFO digesters are not consistent with good energy policy.
The fuel for digesters is primarily CAFO manure, a waste which depletes
and degrades natural resources. In evaluating whether a subsidy under
consideration might be supportable, one must consider whether the subsidy
would produce greater environmental gains if applied, for instance,
to a clean, renewable energy source.
For forward-thinking
energy policy, we have to take a broader perspective. A public
subsidy of $200,000 in public money
could provide about 50% of the funding necessary for a digester which could
collect the methane generated by the water-flushed manure of 1,000 dairy cows,
methane which would be burned for energy and would emit pollutants into
the atmosphere. That same funding could pay for the installation of
wind turbines which would supplant fossil fuel burning on that same farm
without emitting air pollutants. That same funding could subsidize smaller
dairy farms which generate dry manure rather than water-flushed manure; dry
manure generates only minimal amounts of methane. As citizens, it is
our responsibility to "do the math" and to ensure that we are looking
towards long-term solutions, not just short-term fixes.
DO WE SUPPORT LEGISLATION PROMOTING DIGESTERS?
Many states are now considering legislation
which promotes renewable energy and includes methane digesters as a potential
source for such energy. The Sierra Club prefers clean, renewable energy sources
over CAFO waste so legislation should be evaluated to ensure that support
for clean renewable fuels is strong. We also want to ensure that when methane
digester energy is included in legislation, it's impacts are adequately regulated
and small farms are provided with fair access to the technology and to the
energy grids which permit the sale of the energy. Smaller farms may require
additional access and provisions to allow them effective and fair access.
SHOULD WE SUPPORT OR OPPOSE NEW DIGESTERS IN OUR OWN COMMUNITIES?
The Sierra Club opposes
the development of new CAFOs, and, therefore opposes new CAFOs with methane
digesters because the problems of CAFOS will greatly out weigh the potential
benefits of methane digesters. However,
communities with existing CAFOs face a different situation.
In these communities, the decision will be a local, case-by-case decision.
Local, state, and federal environmental laws should be in place to protect
public health and the environment from the impacts of CAFOs. Existing
CAFO owners must comply with all these laws and must have invested in the
technologies needed to eliminate all forms of pollution.
Sierra Club groups
and communities should work together to analyze and decide on a case-by-case
basis whether the good results of installing a methane digester at a local
facility outweigh the bad. Methane digesters can provide substantial relief
from the odor and flies which plague nearby homes and communities (Pain et
al. 1990, Wilkie 2000) as well as providing some reduction in greenhouse
gases and supplanting of fossil fuel use (Martin 2003, US EPA Office of Air
and Radiation 2003). Their emissions, however, must be controlled and safe
operation ensured. The Club can assist communities by assuring that
the public participation process is robust, that all relevant information
is made available to the public, and that federal, state, and local environmental
regulations will fully protect the environment and permit requirements will
be met and enforced.
Fulhage, Charles, Sievers D, Fischer JR (1993)
Generating Methane Gas from Manure. University of Missouri Extension Publication
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Gibbs RA, Hu CJ, Ho GE, Unkiovich I (1997) Regrowth of faecal coliforms and salmonellae
in stored biosolids and soil amended with biosolids. Water Sci Technol 35(11-12):269-275.
Giger W, Alder
AC, Golet EM, Kohler HE, McArdell CS, Molnar E, Siegrist H, Suter MJF. (2003)
Occurrence and fate of antibiotics as trace contaminants in wastewaters, sewage
sludges, and surface waters. Chimia 57(9): 485-491.
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of Potential Antibiotic Contaminants in Water and Preliminary Occurrence Analysis.
Water Resources Update120:30-40
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Study Group (2002) Iowa Concentrated Animal Feeding Operations
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E. Michael Thurman;Steven D. Zaugg; Larry B. Barber ;Herbert T. Buxton (2002) Pharmaceuticals, Hormones,
and Other Organic Wastewater Contaminants in U.S. Streams, 1999-2000: A National
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Union of Concerned Scientists. August 2, 2000 Letter to US EPA Assistant Administrator
Charles Fox "Limit Vital Antibiotics in Factory Farm Effluent" Signed
by Sierra Club and other organizations.
U. S, EPA - April 2004. INVENTORY OF U.S.
GREENHOUSE GAS EMISSIONS AND SINKS: 1990-2002.
Wisconsin Department of Natural Resources, "Frequently
Asked Questions - Concentrated Animal Feeding Operations"
http://dnr.wi.gov/org/water/wm/nps/ag/faq_cafo.htm#q1
Wilkie, Anne (2000)
Anaerobic Digestion: Holistic Bioprocessing of Animal Manures. Proceedings of the Animal Residuals Management
Conference, p.1-12. Water Environment Federation, Alexandria, Virginia, 2000.
<http://molecol.ifas.ufl.edu/images/wilkie1.pdf>