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Value Added Products From Poultry Wastes: Alternatives to Land Application |
Poultry on the Delmarva Peninsula
The poultry industry on the Delmarva Peninsula annually produces about 700 million broiler chickens and 800,000 wet tons of poultry litter (PL, mixture of animal manure and wood chips or shavings). Currently, the only economically feasible use for PL is land application as a nutrient source for the approximately 800,000 acres of grain and vegetable crops on the Peninsula. Given the intensively concentrated nature of the poultry industry, PL in localized areas is often produced in excess of the amount of cropland available for land application. This situation is exacerbated by the economic infeasibility of transporting PL more than a few miles, the excessive levels of P in many Delaware soils from years of PL and fertilizer application, and the rapid urbanization and subsequent loss of cropland in poultry producing areas. The subsequent result is often the over-application of PL nutrients, especially nitrogen (N) and phosphorus (P), to cropland. Concerns about the environmental impacts of excess N and P on soil, water, and air quality have created an interest in identifying economically profitable end-uses for PL other than land application. To ensure the long-term sustainability of the Delmarva poultry industry and minimize the social and environmental impacts of poultry production, it is necessary to maximize land application efficiency through new or innovative practices and to identify and implement uses for PL other than land application. This fact sheet provides an overview of some PL uses that have been considered in other U.S. states and European countries.
Maximizing Land Application Efficiency
Composting: Composting is a waste management method where the organic components of a solid waste are biologically decomposed under controlled conditions (e.g., moisture, oxygen, temperature, pH) to a form that can be handled, stored, or land applied without adverse environmental effects. Composting is commonly accomplished by piling the waste in windrows and aerating it with periodic turning or the use of bins with forced aeration. The process can decrease PL volume and odor, destroy pathogens and weed seeds, and improve the quality of the PL as a soil amendment. Most nutrient contents in compost would be greater than in raw PL due to a loss of PL mass (Table 1). A key exception is N, which usually decreases due to ammonia volatilization losses during composting. Overall, compost is an excellent soil amendment for its ability to increase organic matter and slowly supply plant nutrients.
Table 1. Physical and chemical properties of raw and composted poultry litter (Henry
and White, 1993).
Fractionating: Poultry litter is an economically viable fertilizer for many crops. However, the cost of transporting PL from an intensive poultry producing area to an area where fertilizer nutrients are needed typically exceeds the value of the nutrients in the PL. One way to increase the nutrient value of PL and decrease the amount that must be land applied to meet crop needs is to fractionate the PL by sieving it into a fine fraction consisting of manure, spilled feed, and fine sawdust, a medium fraction consisting of small wood chips and sawdust, and a coarse fraction consisting of large wood shavings, wood chips, and conglomerate clods. The fine fraction has a greater N content and subsequent nutrient value than raw PL, and could therefore be land applied in lower quantities to meet crop needs (Table 2).
Table 2. Physical and chemical properties of raw and fractionated poultry litter
(Ndewga et al., 1991).
The medium fraction, once processed to eliminate pathogens, could be reused as bedding in poultry houses. This could decrease bedding costs and the quantity of PL requiring disposal by as much as 50%. Finally, the coarse fraction could be used as a mulch in agricultural systems such as vegetable production, in composts for horticultural uses, or as a fuel in wood heating systems.
Alternatives to Land Application
Compost Products: When the compost process described above is complete, the finished material can be distributed "as is" for land application or be processed into marketable products. Processed compost could be used in many different land application situations, such as agronomic crop production, vegetable production, turf farms, greenhouses and nurseries, home and commercial landscaping, and land reclamation or remediation projects (e.g., highways, landfills). Compost can be combined with inorganic nutrients and/or pesticides and pelleted to serve as a fertilizer source, or pelleted and mixed into animal feed rations. Compost can also be incorporated as an ingredient in synthetic topsoils or potting media.
Animal Feeds: Because PL contains undigested feed, metabolic products from microbial synthesis, true proteins, and nutrients, it can potentially be used as a feedstuff in the diets of cattle, sheep, poultry, and swine. Due to its high moisture content and possible pathogens and contaminants, PL must be dried and sterilized before incorporation into animal rations. Drying can be accomplished by sun drying, steam heating, roasting, or drum drying; and sterilization can be accomplished by heating, pelleting, chemical treatment, or ensiling. There are several possibilities for increasing the true protein content of PL including biodegradation, the use of natural living organisms to breakdown animal excreta, fermentation, aerobic digestion, oxidation ditch processing, and algae culture.
Bio-Energy Production: Poultry litter has a gross energy value close to that of wood and about half that of coal. Therefore, PL has potential as a fuel to produce energy. In England, a broiler production operation uses the PL it generates as a boiler fuel to heat its seven broiler houses. The system has eliminated the need to purchase off-farm heating fuel. The subsequent energy savings incurred are enough to cover the cost of the heating system in 12 to 15 months. The ash that remains after PL combustion is high in phosphorus and potassium and is sold as a fertilizer to further generate income. Also in England, PL is used as the primary fuel source to generate electricity at a small to medium scale power plant. The plant has been on line 98% of the time since 1992 and currently generates 12.7 MW of electricity. This is enough to power about 13,000 homes.
Anaerobic digestion of organic wastes produces biogas, which is approximately 60% methane (CH4) and 38% carbon dioxide (CO2). The remaining 2% is water vapor, ammonia (NH3), and hydrogen sulfide (H2S). Methane can be directly burned for heat or serve as a fuel for internal combustion engines. Digester effluent could be used as a fertilizer or feed supplement for animals. Although PL is not well suited to anaerobic digestion because of its physical and chemical characteristics, researchers have reported successful digestion operations with a net energy production of 60% to 75% of gross output. However, difficulties during mixing, screening, pumping, and plumbing, formation of scum, grit accumulation, and other operational problems have also been reported. Biogas production is economically justifiable when systems operate at capacity, which can be difficult for smaller facilities (e.g., individual farms). Given this, the economic viability of biogas generation from PL requires in-depth, site-specific planning.
Conclusions
Implementing economically and environmentally sound poultry waste management practices is a challenge facing the Delmarva poultry industry. Accomplishing this will likely require farm, state, and regional waste management plans that focus on options beyond maximizing land application efficiency, such as developing an infrastructure to use wastes in manners such as those described in this fact sheet. Because the socio-economic aspects associated with alternative waste uses are complex, a coordinated, state-wide effort is most likely to be successful in formulating plans that use poultry wastes in manners that ensure both environmental quality and the long-term sustainability of the Delmarva poultry industry.
References
Dagnall, S.P. 1992. Poultry litter as a fuel in the UK: A review. Proceedings of the 1992 Incineration Conference. Albuquerque, NM. May 11-15, 1992.
Henry, S.T. and R.K. White. 1993. Composting broiler litter from two management systems. Trans. ASAE. 36:199-209.
Narrod, C.A., R. Reynells, and H. Wells. 1994. Potential options for poultry waste utilization: A focus on the Delmarva Peninsula. In Environmentally Sound Agriculture. ASAE. St. Joseph, MI.
Ndewga, P.M., S.A. Thompson, and W.C. Merka. 1991. Fractionation of poultry litter for enhanced utilization. Trans. ASAE. 34:992-997.
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