The estimated usable amount of manure produced by confined animals in the United States is more than 61 million tons per year. According to a recent report by the Council for Agricultural Science and Technology (CAST), a leading agricultural science consortium, this figure is increasing. And as animal concentration and farm proximity to residential areas also increase, concerns will grow about the management of such waste.
“If it’s properly distributed and used on productive cropland, manure could decrease commercial fertilizer costs significantly and help industry grow in many parts of the country,” states Dr. Alan L. Sutton of the Purdue University Department of Animal Science, and cochair of the CAST task force report Integrated Animal Waste Management. “Total potential manure fertilizer value from all livestock and poultry production nationally would be around $3.4 billion per year.”
On a nationwide basis, an average of 15% of nitrogen, an essential plant nutrient usually purchased as commercial fertilizer, could be replaced through the use of animal manure. Approximately 42% of crop phosphorus also could be supplied in this way.
Ground Water Concerns
The primary ground water pollutant associated with livestock manure management is nitrate-nitrogen. But this will not reach ground water if earthen feedlots are managed properly. A complete seal beneath the feedlot results from the excretion of salts in manure and from compaction by livestock hooves.
“If, however, the feedlot is abandoned or grossly understocked,” warns report cochair Dr. Jim F. Power of the University of Nebraska USDA-ARS, “Nitrate production and leaching to ground water can occur. To prevent such leaching from lagoons and pits, many states now require impermeable structures incorporating concrete, plastic liners, bentonite sealers, or other sources of clay.”
Animal Feed Concerns
The feeding of animal manures as a source of low-cost nutrients is not a new practice. Early farmers allowed swine access to cattleyards. But the FDA has challenged scientists to demonstrate both the safety of feeding animals processed manures and the safety of the food product derived from these animals.
It has been shown that processing methods like heat, acid treatment, fermentation, and chemical additions can eliminate from feedstuffs derived from animal excreta all the biological agents of concern. Antibiotics pose no health hazards to animals consuming the processed excreta or to humans consuming the products of animals subject to a 15-day withdrawal. And pesticides do not accumulate in manure.
To ensure safe feeding of processed manures, feeding management guidelines have been developed. In the United States, the only documented incidence of a health hazard to animals fed processed manures occurred in sheep, which are especially sensitive to copper in the diet. No hazard to humans has been recorded.
Methods exist to control water pollution and odor nuisance from manure. But because acceptable control often requires substantial investment with little or no economic benefit, producers often have resisted adopting the necessary technology.
Typically, public policies forcing farms to control pollution without compensating them for additional costs result in the exit of many farms–especially small ones–from the industry. Another result is that farms increase in size and intensity. Either outcome can have negative effects on local communities.
“As a result of legislation and case law,” states Sutton, “the access of livestock producers to the funds needed to comply with new regulations may be affected. First, lenders may become liable when they manage or acquire title to real estate. So they may stop lending to livestock facilities with the potential to decrease water quality or to cause odor. Second, credit supply may be affected if the lender knows that judgments obtained by the government for environmental damage will affect repayment ability. Finally, the cost of regulatory compliance affects financial strength overall, and thus borrowing capacity generally.”
One survey indicated that 62.5% of surveyed lenders had rejected loan applications and that 45% had discontinued certain types of loans because of environmental liability concerns.
Partly to limit administration costs, U.S. soil and water conservation policy has stressed subsidies along with technical assistance and education regarding agricultural practices. From 1984 to 1990, the USDA Agricultural Conservation Program spent nearly $1 billion to control erosion, to conserve water, and to improve water quality. Approximately $40 million of this total went to animal manure management.
As a result of legislation, states have adopted or currently are adopting regulations involving permits or approvals of manure management systems and nutrient management plans for livestock operations. But because regulations can be costly to administer, economic incentives often are advocated when practical. Taxes on emissions, like subsidies for emission reductions, are less costly to administer than regulations. Taxes and subsidies also provide direct incentives for the development of new emission-control techniques.
According to Power, “In areas where voluntary efforts are being sought, mandatory regulations of practices and other management restrictions might yet be enforced if these efforts fail. And most agree it’s appropriate to establish and enforce regulations and penalties in the case of willful mismanagement.”
Given current prices, manure’s primary benefit for producers is as a nutrient source for crops. But substantial price increases for livestock feed ingredients or for fossil fuels could increase demand for livestock manure as a feed ingredient or as an energy source.
Animal manures can be subjected to various heating processes producing, among other things, industrial petrochemicals. Although these products can be used for fuel or can be processed for production of carbon black, synthetic rubber, printing ink, and other products, they generally are not economical. Animal manures also can be used as a nutrient source in the production of yeasts and algae, which in turn can be used as animal feed ingredients although–again–not economically.
Regulatory and Research Recommendations
“Regulatory policies should be based on scientific evidence and on the latest technologies,” states Sutton. “Scientifically based monitoring practices are needed to determine whether practices meant to meet water-quality standards are effective. Watersheds need to be analyzed, and environmental controls should be implemented with practical, site-specific solutions.”
According to the CAST report, water-quality research, particularly that focusing on agriculture’s effect on watersheds, and air-quality (odor) research both are critical. But manure management research funding from all sectors has decreased significantly since the early 1970s.
The CAST report lists six research areas likely to yield positive environmental benefits. These areas are (1) modification of animal diets, (2) development or improvement of manure treatment processes, (3) nutrient control and utilization of manures in soil-cropping systems, (4) reduction and control of odor, (5) economic analyses of manure systems alternatives, and (6) development of and economic incentives for new technologies using processed manures and further processed products.
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