Animal Waste Management and the Environment:
Background for Current Issues Environment: (contd.)

98-451

CONTENTS FOR THIS SECTION

Waste from Animal Agriculture

Manure as an agricultural asset
Waste disposal options
Disposal problems

Public Health and Environmental Concerns

List of Boxes
Box 1. Farm Runoff in California
Box 2. Animal Agriculture and Odor Problems

List of Tables:
Table 2. Manure Produced by Livestock
Table 3: Number of Counties where Nutrients Available from Manure Exceed 100% of Crop System Need

Waste from Animal Agriculture

Animal wastes are predominately solid and liquid manures, although they also include used bed(.e.g., spilled feed, dead animals, and a variety of other substances. Manure production is estimated to be almost 112 million tons (dry matter) annually.12 Production varies not only with the animal type, but also with such factors as feed ration, health, animal age, and climate. Trends in the livestock sector such as increased animal confinement (rather than pasturing) and improved feeds have increased the amount of manure produced per animal and changed the composition. The larger volume per animal combined with concentration of more animals at a site compounds storage and disposal difficulties for the farmer. Retention and disposal of manure is the basis of many animal agriculture conflicts.

Animal waste contains nutrients, including nitrogen, phosphorus, and potassium. Nutrients can be valuable for crops, but they can cause water quality problems because of their oxygen-demanding characteristics. Waste can also contain organic solids, trace heavy metals, salts, bacteria, viruses, other microorganisms, and sediments. While effects of these contents on water quality have received most of the attention, there is growing interest in air borne transportation and deposition of pollutants as well. Nutrients have been the focus of interest, as interested parties argue about the benefits they can provide and the environmental problems they can cause.

Animal types, equalized by weight, yield different volumes of manure and different amounts of nutrients. The NRCS has estimated the amount of manure produced on an animal unit equivalent basis for various livestock sectors, as well as the nutrient content of that manure (see Table 2). This comparison shows that the waste management challenges are not the same for all types of livestock.

Table 2. Manure Produced by Livestock (lbs. per day/1OOO lb. animal unit)

Source: NRCS/RCA Issue Brief 7. Animal Manure Management. Dec.1995.

Animal waste is substantial. Comparisons of human community equivalents with the waste that herds or flocks of animals produce are illustrative. For example, the manure produced by a dairy milking 200 cows contains as much nitrogen as the sewage of a community with 5,000 to 10,000 residents, or the litter removed annually from a broiler house with 22,000 birds contains as much phosphorus as the sewage from a community of 6,000 people, according to the USDA's Natural Resources Conservation Service (NRCS).13

Considerable disagreement exists over how to characterize the volume of animal waste in human terms. For example, in congressional testimony on April 2, the National Pork Producers Council witness stated that cattle, swine, and poultry feeding operations produce the equivalent of about 700 pounds of collectable manure per person per year, and contrasted that figure with other estimates of up to 10,000 pounds per person. He then stated that for every pound of nitrogen produced by pigs, 2 pounds are piped into surface waters by public and industrial waste water treatment facilities, and 4 pounds are released into the atmosphere, primarily by internal combustion engines. 14 This is one of many areas in the animal waste management debate where various interests use different data to measure conditions. From origin to disposal, farmers may manage manure and related wastes in many different ways, depending on the characteristics of the farm operation and the physical conditions of the farm. Waste management systems usually include several components. Manure may be collected at temporary storage facilities until it can be treated or utilized. Common storage facilities include stacks, ponds, and tanks. Waste may be treated in many ways to convert it to a more useful resource, usually by concentrating the beneficial constituents and decreasing the total volume.

Lagoons are the most common treatment facility. In a lagoon, the manure undergoes continuous anaerobic decomposition. Failure of lagoons and the resulting waste spills have brought much of the recent critical attention to animal agriculture, and some have called for phasing out lagoons. Other types of treatment facilities include composters, solid separators, and settling basins. Holding capacities of storage and treatment facilities are recommended based on the estimated time period the anticipated volume of waste may have to be retained. For example, waste should not be spread while the ground is frozen, or it will be washed into surface waters, so farms in locations where winters are long need a greater storage capacity. The management process ends when the waste is transferred and used. The most common use, by far, is to spread it across the farm fields as a soil amendment and a nutrient supplement. How it is spread may have important environmental implications; for example, spray irrigation has been associated with environmental problems in some situations, while cultivation into the soil generally minimizes the potential for such problems.

Not all the manure produced by livestock can be collected so that its disposal can be managed. The 1996 Council for Agricultural Science and Technology (CAST) study estimates that almost 62 million tons, 55% of the total, can be collected. Much of the remainder is directly deposited in range and pastures. In discussing possible environmental harm from livestock wastes, whether the magnitude of the problem should be based on the total amount produced, or just the amount that is collectable, is subject to dispute. Some in industry say that collectable amounts are most important, since waste at confined feeding operations is collectable, and farmers can manage the disposal of these wastes to lessen environmental impact. Others say that all waste, including that which is deposited on pastureland, has potential for environmental harm.

Manure as an agricultural asset. Manure can be a valuable asset for agriculture, generally as a supplement to or partial substitute for commercial fertilizers. This value can best be determined when manure is considered in the broader context of overall nutrient management. Manure nutrient values, however, vary considerably and any supply of manure must be assessed for determining application rates. Fertilizer, by contrast, has consistent content, with that information supplied by the manufacturer. Also, nutrients from manure are not all immediately available. Guidelines on the rate of release have been developed for nitrogen, based on the source and form of the manure. NRCS (and probably others) have developed national design standards for many aspects of managing manure, and state regulations are being developed and implemented in a growing number of locations as well (see discussion below of State Programs and Legislative Activities).

A better way to view manure is as a soil amendment that improves many of the physical and chemical properties, as well as the nutrient values of soil by adding organic material and improving soil structure and the ability to hold water and retain nutrients. These benefits are of considerable value. CAST reports in its 1996 study of animal waste management can supply an average of 15% of the nitrogen and 42% of the phosphorus needed by crops. The study states that the total potential value of manure as fertilizer approaches $3.4 billion annually. This figure does not include the economic benefits of improved soil quality, decreased runoff and soil erosion potential, and improved soil moisture, or offsetting costs associated with processing, transportation, and management.

Waste disposal options. Many options exist for disposing of animal waste, but spreading has always been and remains the preferred option throughout the farm community. If all the collectable animal waste could be added evenly to all farmland to help meet crop nutrient requirements, there would be no waste disposal problem. An analogy is rainfall-if the total volume of rain fell equally across the country and evenly throughout the year, supplies would exceed demand. Because it does not, the country has developed extensive public works projects to hold and distribute water in a volume and pattern that meets various demands.

Animal waste also accumulates unequally across the country, far more unequally than rainfall. The NRCS explored this disparity in a recent study that used simulations to examine "the degree to which nutrients in manure from confined livestock operations could potentially satisfy crop nutrient requirements" if all manure was used on crops. The study compared crop nutrient uptake and removal with nutrients available from manure in each of the 3,056 counties in the contiguous United States for three crop systems. Results are shown in Table 3.

Table 3: Number of Counties where Nutrients Available from Manure
Exceed 100% of Crop System Need

Source: NRCS. Nutrients Available from Livestock Manure Relative to Crop Growth Requirements. February 1998.8 p. plus maps and appendices. Resource Assessment and Strategic Planning Working Paper 98-1.

Alternatives for disposing of manure other than by land application are receiving increased attention. Many of these options has some promise in some situations, but none can be viewed as a "silver bullet" that can solve most problems in most locations, and many of these have large initial investment costs. The constituents and moisture content of the manure are important qualities in determining which disposal techniques to use. Shipping costs constrain many options because manure is of low economic value on a volume or weight basis, so it is uneconomic to ship it long distances unless the waste can be concentrated so as to decrease the volume or increase the value. Scientists have looked at ways to increase the value, while economists have prepared scenarios of the maximum shipping distances, given more specific characteristics.

Options under study include composting, burning, and biotech changes to feed that alter the characteristics of the waste.15 Composting uses microorganisms to turn wastes into relatively stable and odorless material that can be used or sold as a soil amendment. Burning can be used to generate energy, but there are limitations. For example, one ton of poultry litter contains about the same amount of energy as 80 gallons of home heating oil, but has the same volume as about 500 gallons. The residue of burned manure is about 10% of the original volume, and contains little of the original nitrogen and sulfur but most of the phosphorus that was initially present. A biochemical change that has received considerable attention is adding phytase (an enzyme) to feed. It has been shown to remove 25% to 40% of the phosphorus and 10% of the nitrogen excreted by causing the animals to use nutrients more efficiently. Phytase does have a cost and must be added to feed. Still other options include converting the waste to fuel and energy, using industrial processes to convert the waste to other useful products, and using it as a feed supplement.

There are some significant success stories of manure management on farms for many of the options to using manure as a soil amendment. Ideas that go beyond these successes for managing animal wastes abound; examples that have been publicized recently are based on using duck week or zebra mussels. But each approach is hard to apply widely because of some combination of physical limitations, high costs, lack of knowledge or management skills by the producer, unfamiliar or untested technologies, and a host of other factors. The costs and difficulties of storing and handling may be the most common constraints for these options.

Disposal problems. Even when farmers control adequate land, proper disposal in ways that will benefit crops and not harm the environment can still be a problem. The manure must be assessed for its nutrient value, then transported to the site, and spread at the proper amounts; each of these steps is an expense for farmers. (If these steps are not taken, any harm that results to the environment has costs, but mainly for the affected public and not necessarily for the individual farmers.) Inherent in these activities is a proper understanding of the value of manure. This understanding can reduce the risk of contaminating surface and ground water.

Producers often determine application rates based on crop needs for nitrogen. But if application rates supply the needed nitrogen, in some instances the amount of phosphorus or potassium will be excessive, especially after several successive years of application. Phosphorus buildup is thought by some scientists to be a source of conditions that led to the pfisteria problems in Chesapeake Bay. (See Box 6, page 1). The National Research Council has stated that "the use of phosphorus as the criterion for determining manure loading rates may be appropriate, particularly in regions containing surface waters where accelerated eutrophication can occur. "16

The simulation data in Table 3 from the NRCS study indicate there is the potential for excessive nutrients in some locations. This report includes maps showing these counties for each simulation. However, the analysis does not convey a precise picture since county boundaries are not barriers to moving nutrients, nor is all cropland available for manure disposal, nor are any of the separate crop systems used on all cropland in any county. The definition of what is in excess will depend on the actual crops grown. Also, this data set is a snapshot that does not indicate change over time. An important conclusion of this study is that counties with a nitrogen excess have excess phosphorus as well, while the reverse is not necessarily true. While these data are about potential rather than actual nutrient amounts, and do not account for the ways that nutrients might be managed or used in alternative ways, the analysis does indicate where problems are most likely to arise. Those counties are largely concentrated in the southern tier of states from the Carolinas to California, with a few counties with excess phosphorus in the upper Midwest, western Nebraska, and eastern Colorado -- a pattern that is similar to the distribution of animal inventories and the largest farms.

Disposal has become more difficult for producers because of two converging trends within the livestock industry: (1) operations are larger which means that there is more waste at a single site; and (2) less land is under the control of these operators. For example, the largest 1% of the beef feedlots produce 71% of the fed beef, but control only 2% of the cropland on fed beef farms, while the smallest 92% of feedlots produce only 10% of the total but control 75% of the cropland.17 These relationships between herd size and available land suggest that many of the largest farms lack the capacity to manage their manure on the land under their direct control. These difficulties have been compounded by increased concerns about water quality and other problems that may originate with intense and concentrated livestock farms.

Livestock waste problems have led to some stricter environmental regulations and the threat of more to come. Agricultural interests argue that these should be unnecessary because it is in the farmers' own interest to maintain a healthy environment. They also argue that the largest farms should have the capital and knowledge to effectively adopt appropriate waste management technologies. But operators of smaller farms, though likely to pose smaller problems, may be less likely to have the knowledge and the capital, and at least one analyst has argued that federal farm program assistance should be targeted to help this segment of the farm population. According to a recent review of the livestock sector in Agricultural Outlook, evidence suggests livestock producers have improved their environmental protection efforts. Based on experiences in North Carolina, where concentration has occurred rapidly, a large portion of violations were found to occur on smaller livestock operations.18 An explanation for such a pattern of violations is probably tied to some combination of economic opportunities, management skills, knowledge and training, and age and condition of facilities.

Manure management problems appear less substantial in this country than in some parts of Europe, especially the low countries. The process of recognition and response there merits review for possible lessons as the United States tries to explore options for addressing this problem. For example, the Netherlands has taken aggressive action to address manure management. 19 Phosphorus saturation is generally believed to be the most serious problem. Programs to stabilize manure production and application started in 1987, and since 1991, manure application rates have been declining. The Dutch policy goal is to reach an equilibrium fertilization rate by 2010, when the supply of nutrients from manure plus fertilizer are to be in balance with crop utilization and other losses. Programs designed for the characteristics of each region are important to this effort. Legislation that would impose fines on farmers for excess nutrient levels in the soil was being considered as this article was being prepared, and the authors of the article concluded that most producers would rather pay the fines for small exceedances rather risk lowering their crop production.

Public Health and Environmental Concerns

According to limited data submitted by states and compiled by (EPA), agriculture is now the leading source of water quality impairments in United States rivers and lakes, affecting 60% of impaired river miles and 50% of impaired lake acres. In estuaries, agriculture affects 34% of impaired acres and is the third largest source behind urban runoff and municipal wastewater treatment plant discharges.20 Feedlots are estimated to be the principal source of 16% of waters impaired by agricultural practices; they are the third leading agricultural source of water pollution, after nonirrigated crops and irrigated crop production.

Animal feeding operations have been shown to cause significant environmental and public health problems, including nutrient enrichment of surface and ground waters, contamination of drinking water supplies, fish kills, and odors. Animal waste, if not properly managed, can be transported by water over the surface of agricultural land to nearby lakes and streams. There, the nutrients in animal waste can reduce the oxygen content of the water, leading to algae blooms, fish kills, and threats to other wildlife.Solids deposited in water bodies can accelerate eutrophication by releasing nutrients over extended periods. Leaching from manure storage lagoons and percolation through the soil of fields sprayed with animal waste has resulted in nutrient contamination of groundwater resources.

Although animal waste is not the only source of pathogens in surface waters, it has been responsible for shellfish contamination in some coastal waters. Closure of shellfish beds and recreational beaches can be necessitated by high fecal coliform counts, both from animal waste runoff and discharge of improperly treated sewage. Animal diseases also can be transmitted to humans through contact with animal feces.

Catastrophic events, such as spills from livestock waste lagoons, have occurred in nearly every state; one of the most famous was in North Carolina in 1995. (See Box 5, page 29) A recent incident of fish kills that occurred in Maryland coastal waters in 1997 was attributed by some scientists, at least in part, to nutrients in poultry wastes discharged into the affected waters that stimulated a toxic microbe, pfiesteria piscicidal.(See Box 6, page 31). 21

Atmospheric deposition of nitrogen from animal operations is also an environmental concern. This occurs when nitrogen in liquid waste is volatilized as ammonia nitrogen (NH3) from anaerobic (oxygen-deprived) lagoons, causing ammonia to evaporate. Volatilization also occurs after land application. Once in the atmosphere, it is converted to forms which are redeposited within 50-100 miles on land or in surface waters. These forms of nitrogen are water-soluble, meaning the nitrogen can adversely affect water quality much like nitrogen fertilizer if it enters a stream as direct surface runoff Data from some locations is beginning to demonstrate the dimensions of this problem. For example, in North Carolina, where concentration and numbers of livestock have increased dramatically, data indicate that ammonia emissions in 995 from swine operations, mainly in the southeast portion of the state, were 50% of the state total of nitrogen oxides-nitrogen emissions from either point sources or highway mobile sources.22

Agriculture's perspective on public health and environmental concerns points out that most farmers are diligent stewards of the environment, since they directly experience adverse impacts on water and air quality, much as their neighbors do. Part of the problem is perceptions. For example, odor that may bother neighbors who are not involved in livestock agriculture may be viewed as an acceptable side effect (if recognized at all) by livestock producers. Like their non-farming neighbors and critics of animal agriculture operations, most are concerned with identifying operators whether big or small whose activities do not fully protect existing resources. However, for many farmers, the loss of agricultural nutrients in runoff (beyond nutrient amounts needed for crop production) is not a consideration that they typically take into account in their operations. In part, this may occur if they lack information about what amounts of nutrients (manure and fertilizer) are needed by plants and thus may assume that using more is preferable to using less. Farmers become concerned with off-site impacts which affect them economically, i.e., if the farmer is fined for a spill or is forced to install manure management equipment.

ENDNOTES

12 Council for Agricultural Science and Technology. Integrated Animal Waste Management Task Force Report no. 128, Nov. 1996:17.

13 Natural Resources Conservation Service. Animal Manure Management. NRC S/RCA Issue Brief 7, Dec. 1995. No pagination.

14 Testimony of Jim Moseley, Representing the National Pork Producers Council before the Senate Committee on Agriculture, Nutrition, and Forestry, April 2, 1998: 7.

15 Information in this paragraph is taken largely from presentations at a forum on phosphorus and water quality on November 3, 1997, convened by Representatives Wayne Gilchrest and Charlie Stenhoim. These options were discussed in the context of poultry waste, and its possible contribution to pfisteria problems in some drainages along the eastern shore of Chesapeake Bay,

16 National Research Council, Board on Agriculture. Soil and Water Quality: An Agenda.for Agriculture. (1993): 407.

17 Leston, David, and Noel Gollehon. "Confined animal production and the manure problem. Choices. Third Quarter, 1996:19.

18 USDA, Economic Research Service."Livestock manure: foe or fertilizer." Agricultural Outlook. June 1996: 35

19 Information in this paragraph is summarized from: Van der Molen, Diederik T., Auke Breeuwsma and Paul C. Boers. "Agricultural Nutrient losses to surface waters in the Netherlands: impact, strategies, and perspectives." Journal of Environmental Quality. Vol. 27(19998): 4-11.

20 U. S. Environmental Protection Agency. National Water Quality Inventory:1994 Report to Congress. EPA841-R-95-005. Dec.1995. These water quality data are limited, because they represent only conditions in waters assessed by states but do not include all water bodies. For this report, states surveyed 17% of river miles, 42% of lake acres, and 78% of estuaries. Nevertheless, EPA believes that the data point to a major, continuing water pollution problem coming from agricultural sources of all types - crop and pastureland, rangeland and concentrated animal operations. The data should be used with caution.

21 For additional information, see CRS Report 97-1047 ENR, Pfiesteria and Related Harmful Blooms: Natural Resource and Human Health Concerns.

22 Aneja, Viney P., George C. Murray, James Southerland. "Atmospheric nitrogen compounds: emissions, transport, transformation, deposition, and assessment." EM vol.4, April 1998: 22-25.