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Managing Manure To Improve Air and Water Quality
Marcel Aillery, Noel Gollehon, Robert Johansson, Jonathan
Kaplan, Nigel Key, and Marc Ribaudo
Economic Research Report No. (ERR-9), September 2005
U.S. environmental laws tend to focus on a single environmental
medium (e.g., Clean Water Act, Clean Air Act, and Endangered
Species Act). When a single pollution source can simultaneously
affect more than one environmental medium, a single-medium approach
to pollution control can confound policymakers concerned with
economic efficiency. An uncoordinated set of policies that independently
address different pollution issues can result in unnecessary
and unanticipated economic and environmental costs.
Animal agriculture is facing just this situation. Animal agriculture
produces a variety of pollutants, including organic matter,
urea, ammonia, nitrous oxide, phosphorus, methane, carbon dioxide,
pathogens, antibiotics, and hormones. Regulations to restrict
animal farm emissions to the water might inadvertently increase
emissions to the air, and vice versa.
What Is the Issue?
In 2003, EPA introduced revised Clean Water Act regulations
to better protect surface waters from nutrients from concentrated
animal feeding operations (CAFOs). When applying manure to crop
or pasture land (the primary disposal method), CAFOs now must
follow a nutrient management plan that specifies a manure application
rate that minimizes the threat to water quality. The cost to
farmers of meeting this requirement can be relatively high,
primarily from moving manure to an adequate land base. A logical
response by producers operating under a nitrogenbased plan might
be to reduce the nitrogen content of manure spread on fields
by enabling nitrogen to volatilize into the atmosphere from
uncovered lagoons or by applying animal waste to land without
incorporating it into the soil. But doing so also releases ammonia
emissions into the air. As animal feeding operations are the
primary source of ammonia in the United States, air quality
regulations might require some States to regulate ammonia emissions
from animal feeding operations.
What Did the Study Find?
Air and water quality regulations would be most cost effective
if implemented simultaneously. This would allow farmers to select
the most appropriate mix of practices that satisfy environmental
quality goals while maximizing net returns. If environmental
policies are uncoordinated, farmers may have to make costly
changes to practices more than once before both environmental
goals can be met.
To meet a water quality goal, farmers tend to use practices
that increase ammonia emissions to the air. Similarly, the practices
used to meet an air quality goal would tend to increase nitrogen
losses from fields to ground and surface waters. Meeting both
air and water quality goals would likely cost more than meeting
either air or water goals.
Depending on how the air quality regulations are applied, this
could have two impacts on CAFOs and water quality. First, farms
identified as CAFOs might need to increase the amount of land
on which they spread manure in order to continue to meet nutrient
application standards. This could be particularly costly in
a region where animal concentrations are high and cropland available
for spreading manure is relatively scarce. For example, requiring
CAFOs in the Chesapeake Bay watershed to control ammonia emissions
would increase producer costs of land- applying manure by $4
million per year. Failure to account for these costs when developing
an ammonia regulation could lead to the false conclusion that
the policy is efficient.
Second, an uncoordinated approach could reduce water quality.
If ammonia reductions were required of both CAFOs and smaller
farms, the water quality benefits from the regulations restricting
CAFOs’ nitrogen emissions might be diluted by increased
nutrient applications on the smaller farms, which have no such
nitrogen restrictions. In the Chesapeake Bay watershed, for
example, the nutrient content of manure produced on farms not
covered by a nitrogen application standard would more than double
if ammonia restrictions were applied to all animal feeding operations.
This would increase the risk of nitrogen runoff into the Chesapeake
Bay.
Anticipating the different forms and pathways that nitrogen
takes can keep air quality and water quality policies from working
at cross purposes. Then, true solutions—like diet manipulation
(to reduce the amount of nitrogen excreted by animals) or industrial
uses of manure—might become clearer.
How Was the Study Conducted?
The study used three separate but related analyses to capture
the full range of economic decisions (and consequences) that
result from farmers’ meeting environmental regulations.
Data from the 1998 Agricultural Resources Management Survey
of hog producers were used to estimate the tradeoffs that occur
at the farm level when policies are designed to address pollutant
flows to one environmental medium without considering flows
to another medium. The broader impacts of coordinated policies,
including the welfare impacts on both producers and consumers
and regional shifts in production, were examined with a national
model of the agriculture sector that tracks nitrogen losses
to the environment. A case study of the Chesapeake Bay watershed
was used to demonstrate the problems that hypothetical ammonia
reductions would have for farms meeting the CAFO regulations
in a region where land for spreading manure is relatively scarce,
and for resource managers trying to reduce nitrogen loads.
At the heart of all three analyses are nitrogen loss coefficients
that are derived from a mass-balance accounting of nitrogen
in manure. These were obtained from EPA, and enabled us to estimate
tradeoffs in nitrogen losses to the air and nitrogen applied
to land as different manure management practices are employed.
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