Swine Environmental Issues: Snowballing Legislation and Manure Management – Where Are We Headed?

During the past two decades pork production in the US has grown in numbers only slightly. However, there has been a shift in both where these animals are grown and how they are grown. There is still a high concentration in the traditional midwestern cornbelt, but there has been rapid growth in the southeast, especially North Carolina.

Most animals today are raised in specialized confinement housing facilities designed as environmental growth chambers. This presents both an environmental improvement over the era of animals in mudlots with uncontrolled odors, runoff, and parasites, but at the same time a challenge of dealing with concentrated accumulations of manure in a sustainable manner. The industry is becoming increasingly integrated where private landowners contract with a company to provide the land, facilities, utilities and labor in return for a fee to finish the company’s animals to market weight.

As a result farms tend to be larger, less diverse, and more densely centered around the company’s support facilities such as feed mills, processing plants, and sow farrowing and breeding farms. This article will tend to focus on some environmental issues, regulatory trends and alternative research underway as a result of these shifts in pork production practices.

Issues surrounding animal agriculture

ATMOSPHERIC EMISSIONS

One of the primary environmental drivers in the US regarding pork production has been the ‘odor as a nuisance’ issue. Much of the early debate centered around this one issue. Emerging issues have more recently focused on other atmospheric emissions, primarily ammonia and methane and their greenhouse effect.

Odor
To enforce odor management regulations developed around standards, three things must become more standardized with universal acceptance through additional research and collaboration: (1) odor measurement, (2) air sampling, and (3) odor standards. Research to date has relied on olfactometry panels for odor measurement. There is still a lack of scientific consensus regarding standardization of measurement methods. Regardless, olfactometry for use as an odor enforcement tool is cumbersome, laborious, and costly.An alternative currently under research and development is an electronic or ‘artificial nose’. This method would conceivably be simpler to use in the field and would remove the human bias.

Any odor measurement is no better than the sampling method used: (1) when do I take the sample?, (2) where do I take the sample?, and (3) how do I take the sample? Finally, after odor monitoring technologies have been agreed upon, there is the question of odor standards: (1) how much odor is acceptable?, (2) how much is too much?

Ammonia
Ammonia emissions have been of utmost concern in European countries for several years. Only recently has it received the same level of attention in the US, largely because of a lower density of livestock production and the lack of scientific data to document the degree of ammonia emission, and more importantly, the impact of the emissions upon the environment. Some areas of low-density production still are not concerned about ammonia impact. Other high-density production areas are engaged in research documenting the levels of ammonia release from livestock farms, the impact of this release on the environment and development of models to predict releases and impact.

Methane
Methane and its accompanying greenhouse effects are of interest both with regard to animal gastrointestinal emissions and with regard to its release from manure storage and lagoon surfaces.

WATER QUALITY

The predominance of professional opinion is that the livestock industry has not and is not causing a widespread national water quality problem. Highly publicized local events and problems, however, have focused much attention, regulation, research and educational effort on minimizing these local problems. Manure spills, local climatic changes, and fish kills have spawned much debate as to the cause and extent of agriculture’s contributions to these problems. Regulations to tighten the standards associated with manure management and educational programs in the form of required operator training are now standard fare for livestock producers in order to prevent some of the events of the past from reoccurring.

NITROGEN

Nutrient assessments of high density livestock regions such as eastern North Carolina have indicated that some counties have approached a saturation level of nutrients for crop fertilization from livestock and poultry manure alone. These areas do not yet coincide with the watershed within the state that is having the most water quality problems, but they are not viewed as sustainable if a proliferation of new livestock farms continues in those same areas.

PHOSPHORUS, COPPER AND ZINC

Mineral elements such as phosphorus, copper, and zinc, all of which are essential elements of animal diets and for plant growth, have long been thought to be tied up in the soil when land-applied via manure and therefore relatively harmless. Current research is focusing on soil’s finite ability to tie up these elements, however. When phosphorus moves into surface waters either from surface runoff through erosion or through subsurface flow it becomes a primary contributor to surface water eutrophication. Copper and zinc added to animal rations in excess of amounts needed tend to accumulate in soils where manure is applied and can accumulate to levels toxic to plant growth. Apparently substantially lower quantities in the diets could achieve the same purpose with regard to digestibility, health and performance and reduce the amount excreted in the manure.

PATHOGENS

This country has the safest food supply in the world. However, each time there is an E. coli or salmonella incident, more attention is focused on more intense treatment and handling of livestock manures and wastewater and especially diseased animals. Treatment systems in the future will need to focus more attention on those processes which minimize pathogenic organisms.

INDUSTRY STRUCTURE

Many special agendas tend to get rolled into one large ‘environmental’ debate about pork production. One of these issues is whether the industry should remain as small ‘independent family farms’ with all the nostalgia typically associated with them or should it take the same track as other businesses in today’s society and become consolidated and integrated into contract production. Regardless of our opinions, a world with an ever-increasing population and finite land resources will need to rely on a more specialized food production system.

CITIZEN INPUT

With our increasing population, more people wish to ‘live in the country’ in a rural setting. This increasing mix of farm and non-farm residents inevitably precipitates conflict over local environmental issues. Since livestock production is on the increase in many of these areas, citizens are demanding more local input into the siting and management of these facilities. This brings about more local regulation and zoning making it increasingly expensive and complex to site a new or expand an existing livestock farm. One is reminded at this point of the adage that ‘all politics are local’. Ironically, increased regulation will fall hardest on the small farms that a segment of the citizen activist groups are trying to save.

Farm regulations, now and in the future

Environmental regulations relating to livestock producing farms have to date been written primarily at the state government level.Varying regulations among states have been a contributing factor to shifts in growth of the swine industry to states with less or ineffective regulation. Future regulation will shift to national rules to level the playing field and require all states to adhere to a more uniform set of standards. The following is a snapshot of what most hog producers are facing now or are going to face in the future regarding environmental regulation in the US. Some attempts will be made to make these regulations progressive with the largest farms facing more restrictive rules, but all farms, regardless of size, will be regulated to one extent or another.

REGISTRATION

Farms producing livestock will be required to be registered with the appropriate state regulatory authority. This will allow states to develop a complete inventory of where farms are located and the density of farms in a specific locale. Cumulative impact of livestock farms within a county, watershed, or other planning jurisdiction can then be determined.

SITING

A comprehensive site evaluation should be performed before the permitting process of a new or expanding farm may proceed. This site evaluation will focus on proximity to adjacent land uses, e.g., distance to neighbors, public use areas, environmentally sensitive areas (streams, lakes, wetlands, wells, floodplains, sinkholes, archeological or historically important sites) and endangered species. Minimum setback distances from environmentally sensitive areas will be considered for production buildings, manure storage and treatment, and land application of any wastes. An evaluation of soil type will be considered to determine suitability of the soils for earthen manure storage and treatment to protect groundwater, depth to the groundwater table, geology, soil fertility and realistic crop productivity for manure nutrient utilization. Land availability to properly utilize the nutrients at agronomic rates projected from the size of the planned operation including any future growth in animal numbers is an essential part of the siting evaluation.

PUBLIC PARTICIPATION

Much of the opposition to growth of swine production currently centers on the lack of participation in the planning process by local citizens.As a result, county governments are adopting local ordinances which are more stringent than state rules including, but not limited to, zoning of animal agriculture. Public notice will become a part of the permitting process to allow concerns of adjacent landowners and local citizens to be raised and questions to be answered about the planning, construction, and permitting of new or expanded facilities.

DESIGN AND CONSTRUCTION OVERSIGHT

Each new manure or wastewater handling, treatment or storage facility should meet the engineering standards and specifications consistent with those provided by the Natural Resources Conservation Service or by a registered professional engineer. Not only should the plans and design meet accepted engineering standards, but day-to-day construction should also be overseen by qualified professionals. This supervision by qualified and certified professionals reduces the risk of failure or contamination and helps to ensure that the facility is constructed according to its design.

MANURE MANAGEMENT PLANS

Each farm should develop a comprehensive manure management plan. This plan would include: number and steady-state live weight of animals on the farm existing or planned, amount of manure or wastewater and nutrients generated, type and design plans of collection, containment, and treatment systems, amount of land, type of crops, realistic yield expectations, soil sampling analyses, manure analyses, amount of land and nutrient application rates based on the most limiting nutrient (usually nitrogen or phosphorus), manure storage liquid level management, type of application equipment with calibration procedures to meet the soil hydraulic application rate, site maps, and setbacks from environmentally sensitive areas.

ODOR MANAGEMENT PLANS

Until there is scientific consensus on odor monitoring and standards, odor regulations will focus on a list of enforceable, implementable solutions for odor management. One state requires a farm to develop a farm-specific checklist of management practices from a menu of proven, cost-effective best management practices that can be implemented to reduce odors. Upon inspection the farm is judged in compliance if all of the practices on that checklist are being maintained.

MORTALITY MANAGEMENT PLANS

All farms must properly dispose of dead animal carcasses within 24 hours or within the response time required by state law. The method of disposal must be described, i.e., burial, pit disposal, incineration, rendering, or composting. All federal and state oversight requirements must be met to prevent spread of disease.

EMERGENCY RESPONSE

All farms should prepare and keep visibly posted an emergency response and action plan. Even the best designed and managed facilities are subject to accidents or weather-related events that can lead to spills. Planning ahead to manage these emergencies can avoid environmental damage. Farm employees should be trained to know what sequence of events to follow to minimize this damage.

RECORD KEEPING

Each farm should keep comprehensive records of management practices that help to protect the environment such as facility operation, manure management, nutrient application and utilization and emergency response actions. These records should be easily accessible to inspectors and should be kept for at least three years for the producer’s protection in case of future conflicts or disputes.

OPERATOR TRAINING AND CERTIFICATION

Pork producers and contractors should follow the lead of other industries and good businessmen by properly training employees to operate and manage the manure and wastewater management facilities.Acertain number of hours of operator training should be required such that upon successful completion, the operator-in-charge would then be certified to manage the waste management facilities and to supervise other farm workers to do likewise. To remain certified and stay up-to-date a specified number of continuing education credits would be required.

MANURE STORAGE AND TREATMENT CLOSURE PLANS

Whenever a farm ceases operation or plans to abandon a manure storage or treatment facility, a proper closure plan or procedure should be required. Usually this closure requires all manure, wastewater and biosolids to be removed and properly disposed of in accordance with Natural Resources Conservation Service standards. A program for new and expanded farms should be developed to provide assurances of financial responsibility sufficient to meet the cost of closure.

PERMITTING

All farms will be required to be permitted at the state level either through a general or individual permit. This permit will include consideration of all of the above-mentioned items. The farm will no longer be able to legally operate without a permit or under a state blanket permit which does not provide up-front protection against environmental damage.

INSPECTIONS AND ENFORCEMENT

Inspection of each farm will be required periodically by the appropriate state authority. Some states are already requiring annual or semi-annual inspections. This inspection will validate that the farm is operating in compliance with their permit.Willful or negligent mismanagement may result in permit revocation, fines or farm closure. The inspection framework may include a ‘bad actor’ clause with disincentives for a producer with a history of violations.

FINANCIALAND TECHNICAL ASSISTANCE

Federal and state legislatures and agencies should strive to provide financial and technical assistance programs to pork producers to adopt practices needed to comply with an ever-increasing and changing set of environmental regulations.

Manure treatment alternatives

ISSUES

The same question asked for decades is still appropriate, ‘Should manure be considered a resource or waste?’ The answer depends considerably on the land base available, soil fertility, realistic crop yield expectation and topography. If adequate land is available to utilize the manure nutrients at agronomic rates to grow a crop profitably, then nutrient conservation in a concentrated slurry with minimal water addition is preferred. Areas where animals are grown on minimal land with low soil fertility have two challenges: (1) imported feedstuffs and nutrients into those areas, and (2) treating or reducing the nutrients unused by the animal to a level where they can be sustainably applied to the available land without detrimental environmental impact. Alternative manure treatment systems researched since the 1960s have proven to be quite expensive.

Are the manure treatment systems expected only for stabilization of the organics and nutrient reduction for nuisance control and environmental protection, or are they expected to produce stable by-products for profit off-farm? Much research is underway to convert organic manures into usable by-products; however, markets for these by-products must be established, or else existing markets may be saturated quickly.

Should manure from animal production facilities be treated on-farm or in centralized multi-farm treatment systems? From the standpoint of reducing the per-farm costs of treatment and hiring more skilled operators, centralized treatment would be preferred. However, collection and transportation costs from farm to treatment plant have to date proven insurmountable because of the dispersed nature of most farms in the US. The predominance of professional opinion indicates that treatment and utilization of farm-generated manures and by-products for the foreseeable future will be at the farm level.

As treatment systems become more sophisticated, specialized and complex, operator skills and training will also have to keep pace. Current farm managers will have to be trained and certified to operate technologically advanced systems for which they have no background. These alternative systems will require much greater attention than current systems to consistently and reliably perform at an acceptable level.

METHODS TO REDUCE MANURE IMPACT

The following areas within the swine farm production system are currently being studied closely as alternatives to reduce manure production, nutrient content, nuisances and other environmental impact.

Manipulation of the animal diet
During the last three decades, animal genetics and ration formulation have improved swine feed conversion efficiencies from 5 lb feed per pound of gain to 2.5 lb feed per pound of gain. This improvement means less feed required and less manure produced by a given number of animals. Current US and European research also indicates considerable progress to be made by manipulating the diet formulation. The use of enzymes such as phytase for increased conversion efficiency of phosphorus can reduce the excretion of this nutrient by as much as 40%. Similarly, altering amino acid content of the diet has reduced manure ammonia emissions while supplementing lysine to a low-protein diet has reduced total nitrogen excretion by 30–40% without a decrease in animal performance. More attention should be given to the role of wet-dry feeders to reduce feed wastage and improved drinking waterers which reduce the amount of fresh water spillage and consequently the pressure on the manure treatment, storage and handling systems. This dietary manipulation holds much promise for reducing the manure management challenges pork producers are facing.

Production facility design
There is no substitute for good housekeeping and sanitation within a swine production barn to maintain a clean, dry and comfortable growing environment for the animals. Slotted floors help to separate the manure from the animals quickly and with a minimum of labor. Manure and liquids are collected in a shallow pit underneath the slotted floor. Manure should be removed from this pit as frequently and regularly as possible. Some European pit floor designs allow for the liquids to be drained and handled separately from the solids. Solids are then removed with mechanical scrapers. These scrapers still leave a film of manure on the floor that when combined with the urine between scrape events generates gases and odors in the building. In warmer regions of the US where lagoon effluent can be recycled, the pit floors are either flushed several times daily or drained and recharged with new lagoon liquid on a weekly basis. The environment within the building is significantly improved using this pit cleaning technology.

Ventilation systems can drastically affect the in-house environment of a production facility for both animals and workers. Ventilation should bring in fresh air to the building while removing the moisture from animal respiration and the dusts and gases from the building. Control of these potential pollutants inside the building means less will be removed to the outside environment by the ventilation system.Wet-dry feeders, feeder tank covers, and pelleted feed supplemented with fat help to control dusts in the building. High airflow ventilation systems such as tunnel ventilation which bring all of the air through the animal growing space have the advantage of cooling the animals during heat stress periods, but are not as good for cold weather ventilation or exhausting the gases from the manure pit without effects on the animals and workers. High airflows also limit the biotreatment of the exhausted air outside the building. Underfloor ventilation where part of the building ventilation air is exhausted from underneath the slotted floor from the pit vicinity creates a better growing and working environment. The exhausted air with underfloor ventilation is more concentrated but lends itself to biotreatment because of lower airflow rates.

Treatment of exhaust
High airflow ventilation systems create a plume of exhausted air which can travel some distance downwind. Dust particles in this exhaust air plume are known carriers of odor. If this plume of exhausted air is directed over lagoons or manure storage facilities after leaving the building, the plume may pick up even more odor. Therefore, locating buildings on the landscape in relation to prevailing wind directions and with respect to distance from neighbors along with the location and direction of exhaust air can help significantly to reduce production facility nuisance factors.

Biotreatment of building ventilation exhaust can take the form of biofiltration, biomass filters, or wet scrubbing or washing walls. Biofilters consist of a bed of porous organic material such as wood chips, sawdust, or compost which serves to filter the dust particles from the exhaust air and to microbially transform or remove some of the volatile organic compounds which cause odors. Biofilters have proven to be very expensive and maintenance intensive. Biomass filters are a series of hanging baffles of an organic material such as crop residue within an enclosed area. Exhausted air is directed onto these baffles where dust particles are physically trapped and odorous compounds are microbially transformed.Wet scrubbing walls are porous material similar to an evaporative cooling pad which is wetted and through which all building ventilation exhaust air is passed. Windbreak walls are physical barriers downwind of the exhaust fans which reduce the velocity of the exhausted air allowing the plume to be broken up and dispersed.

Manure treatment
Manure treatment processes can consist of single techniques to meet a specific objective or a train of processes for complete stabilization of the manure and wastewater. Value-added by-products are a means of recovering some or allof the costs of advanced treatment. These treatment processes can either apply to single farms or be applied to several farms at a central processing facility.

Problems with centralized treatment include transportation costs of raw swine manure which is usually collected in a high-moisture state and market development for the stabilized by-products. The following is a partial list of some of the more promising treatment or pre-treatment techniques that have been or are currently undergoing research and development:

Solids separation. Removing organic solids from liquids allows the solids to either be transported farther for land application or processed and stabilized for off-farm marketing and use while the liquids can be treated and handled at lower costs. Mechanical, stationary, or rotary screens usually remove up to 30% of the total solids of manures with high liquid content yielding a moderately dry product, while gravity settling basins can remove upwards of 50% of the total solids but at a higher moisture content.

Enhanced phosphorus recovery. Addition of chemical or organic polymer flocculating agents to liquid manures can enhance the solids and phosphorus recovery from liquid manures by up to 90% yielding a phosphorus-rich biosolid material.

Compost; vermicompost. Separated manure solids mixed with a carbon source such as sawdust, poultry litter, peanut hulls, shredded newsprint, etc. can be conventionally composted for stabilization and marketing off-farm. Recent efforts at using earthworms to stabilize a mixture of manure solids and sawdust yielding a marketable vermicompost by-product have been quite successful.

Pelletizing; extrusion. Separated manure solids have also been mixed with other by-products or value-adding ingredients, then heated and pelletized or extruded into stable or marketable by-products.

Biological treatment.Wastewater has been successful treated and stabilized prior to land application by aerobic microbial treatment (lagooning, extended aeration, activated sludge) to remove the odor potential. Nitrogen can be transformed and reduced to relatively harmless nitrogen gas by sequencing batch reactors alternating between aerobic nitrification and anoxic denitrification. These processes remain relatively expensive and need additional research and development to be viable for on-farm manure processing.

Photosynthetic treatment. Natural aerobic treatment processes which utilize sunlight or artificial light sources to stimulate photosynthesis are being researched to use algae, duckweed, water hyacinths or other aquatic vegetation to remove nutrients from wastewater. This harvested aquatic vegetation when further processed and dried can be incorporated into feedstuffs to reduce
the amount of imported nutrients into a nutrient-rich watershed. More research and development is needed on the harvesting, processing and incorporation of these aquatic plants into animal diets.

Storage facility design. Standards have been upgraded to prevent leakage of manure and wastewater storage systems into the groundwater or emission of greenhouse gases into the atmosphere. Earthen storage facilities and lagoons in most states now have to meet a seepage rate of 10–7 cm/sec or less. Properly installed synthetic membranes or compacted clay liners are being used to meet this standard. Above-ground earthen storages or fabricated tanks are required in high water table areas along the coast or in porous soils and geologic formations. Roofs over compost sheds are increasingly being required for rainwater exclusion, which also increases quality control of the composting process. Covers are being studied for exclusion of rainwater from earthen storages and lagoons, particularly in high rainfall areas of the US. Biocovers of floating straw, crop residue, leka rock, and other organic materials are being researched for covering the contents of slurry tanks to reduce the odor emission.

By-product utilization
The most obvious use of manure nutrients and organics to date has been to apply them to cropland or forages as organic fertilizer.With increasing farm sizes and numbers, however, other uses must be and are being developed. Value-added by-products will be needed for off-farm marketing to offset transportation costs and avoid nuisance-related resistance to their usage. Composting separated manure solids with other farm or community by-products for use as soil amendments or organic fertilizers provides a valuable outlet for land-limited farms as well as a service to a community having trouble disposing of shredded paper, yard waste, leaves, wood chips, etc. Separated solids when properly processed can be a cheap and safe protein supplement to ruminant feeds. Biogas from anaerobic digestors and covered lagoons provides an alternative fuel source to operate boilers for heating hot water or providing space heat, and for internal combustion engines or fuel cells to co-generate electricity.

Water quality protection
Whole farm nutrient management planning is increasingly required to minimize nutrient losses off-site into adjacent water sources. Maximum use of natural and improved riparian buffers along stream edges can lessen the impact of both surface runoff and subsurface flow from land application fields to surface waters. This riparian buffer is usually a combination of native trees and planted grass strips. Constructed wetlands help maintain water quality by providing tertiary treatment of secondary-treated swine wastewater and by storing some of the conserved nutrients and transforming some of the nitrogen into nitrogen gas from land application field runoff.

SELECTED REFERENCES

Barker, J.C. and J.P. Zublena. 1995. Swine production –Waste management and utilization. In: Waste Management and Utilization in Food Production and Processing, (L.L. Boersma and I.P. Murarka, cochairs), Task Force Report No. 124, Council for Agricultural Science and Technology, Ames, IA. pp. 42–54.

Burton, C.H. 1997. Manure Management: Treatment Strategies for Sustainable Agriculture. Silsoe Research Institute, Wrest Park, Silsoe, Bedford, UK.

Sutton, A.L. and J.F. Power (cochairs). 1996. Integrated AnimalWaste Management. Task Force Report No. 128, Council for Agricultural Science and Technology, Ames, IA. p. 87.

North Carolina Agricultural Research Service Animal and Poultry Waste Management Center Website address: http://www2.ncsu.edu/ncsu/cals/waste_mgt/

North Carolina Cooperative Extension Service Water Quality and Waste Management Fact Sheets Website address: http://www.ces.ncsu.edu/resources/water

Author: JAMES C. BARKER
Biological and Agricultural Engineering Department, North Carolina State University, Raleigh, North Carolina, USA

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