Summary.An increase in the number and concentration of integrated livestock and poultry operations in the United States presents a greater challenge of efficient and environmentally sound management of animal waste. A co-firing technology for coal and broiler litter (BL) to generate power may provide a simplified disposal method for BL. A first step in developing such a technology is to analyze and understand the properties of BL as a fuel source. In this study, ultimate and proximate analyses were performed on excreted broiler manure (EM), cleanout litter (CL), dried and ground litter (DL), coal, and a 90:10 blend of coal and CL (C90:DL10) to determine BL fuel quality and characteristics. The results showed that BL fuels were higher in nitrogen, sulfur, and ash but lower in heating values than those for coal. The ash composition of EM and CL indicated that these fuels are likely to cause fouling and corrosion in a boiler burner due to greater concentration of ash and its higher volatile oxides composition as compared to coal. The 90:10 blend (C90:DL10) exhibited fuel quality and cost ($/GJ) similar to coal. Further testing of BL fuels in a small-scale boiler burner is necessary to assess fouling and corrosion potential along with combustion efficiencies and pollutant emissions of these fuels.
Keywords. Broiler Litter, coal, combustion, energy, fuel properties, heating value
Introduction
The number and concentration of integrated livestock and poultry operations has increased dramatically in the United States, presenting greater challenges for the efficient and environmentally sound management of animal waste. Broiler producers under contract from poultry integrators raise broiler chicken in houses that may contain flocks of 10,000 to 30,000 birds per house. On average, each house produces 5 to 6 flocks per year. Poultry broiler production in the USA has increased dramatically, with total broiler meat production increasing from nearly 5 billion lbs (2.27 billion kg) in 1961 to more than 40 billion lbs (18.2 billion kg) produced by 8.4 billion birds in 2001.
Texas ranked sixth in the nation, with an estimated total production of 566 million broilers in 2001 (UDSA, 2002). Manure excreted by the birds is mixed with feathers, feed, water, and bedding material, such as saw dust, rice, or peanut hulls. With an average litter production of 1.25 tons (1.14 metric tons) per 1,000 birds sold (NRAES, 1999), more than 700,000 tons of broiler litter (BL) was produced in Texas in 2001. Although some BL is used as supplemental feed for cattle (McCaskey, 1995), most of the stockpiled or cleaned-out litter is land-applied as a fertilizer source for crops and pastures.
The use and disposal of BL is a problem for poultry-growing areas where soils exhibit high levels of phosphorus (P). If BL is applied repeatedly at rates above the nutrient intake of plants, the potential for nitrogen (N) and P pollution of surface and ground water increases (Beauchemin et. al, 1996). Also, because of the bulkiness of BL, transportation costs to distant crop and pasture lands may be economically prohibitive. If it is stockpiled on the farm for longer periods, excessive odors and ammonia emissions from wetting and drying of BL exposed to precipitation are a concern. Providing extra storage space and cover for stock piling BL on farm is also costly.
An alternative solution to applying BL on land may be to use it as a fuel source for power generation. Researchers have summarized various technologies that use feedlot (beef cattle) biomass as a fuel energy source (Annamalai et al., 1987 and Sweeten et al., 1986). However, efficient combustion of animal waste has had limited success because of its higher ash and moisture contents and other product inconsistencies as compared to coal and natural gas.
Our research project involves a co-firing technology to use BL and coal for power generation. BL will be used as fuel by mixing it with coal in a 90:10 (Coal:BL) blend and firing it in existing coal-fired combustion devices. The high temperatures produced by the coal will result in the complete combustion of the biomass. The long-term goal of this study is to develop an animal biomass and coal co-firing technology. This paper presents information on physical and chemical properties of BL fuel, a comparison of BL properties with excreted broiler manure and coal, and an economic analysis of transporting BL to coal power generation plants in an 8-county area of east central Texas.
Conclusions
Based on these findings, further testing of BL fuels in a small-scale boiler burner is necessary to assess fouling and corrosion potential along with combustion efficiencies of these fuels.
For more information on this project, please contact:
Saqib Mukhtar
Mukhtar@tamu.edu
979-458-1019
303-B Scoates Hall
2117, TAMU
College Station, Texas 77843-2117
USA.
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