Using Broiler Litter as an Energy Source: Energy Content and Ash Composition

Abstract

Broiler farms produce large amounts of litter that is typically spread on nearby cropland or is sold to other farmers for use as a fertilizer substitute. Burning litter biomass to provide energy for space heating in broiler houses or for off-site electric generation has been viewed as an attractive alternative to land application and a source of renewable energy. A large litter sample was obtained from a commercial broiler farm following clean-out to evaluate the energy content, ash yield, and characteristics of ash following combustion. Litter ash was evaluated as a possible lime substitute and fertilizer. The energy content of the broiler litter was 14,425 kJ/kgDM and had an ash content of 24.7% dry basis. Broiler litter ash contained large amounts of Ca and a pH of 11.6, however the calcium carbonate equivalency (CCE) was only 32.4% on a dry basis. It was determined that broiler litter ash should not be used as a liming agent since it would result in excessive application of P2O5, K2O, Cu, Zn, and Na. Small applications of litter ash, on the order of 2 t/ha or less, can provide the P or K needs of a crop and can serve as a source of key micronutrients without application of large amounts of Zn, Cu, or Na. A 1-MW litter fueled electric power plant would provide enough P2O5 in litter ash to fertilize only 1600 ha at a rate of 100 kg P2O5/ha. It was also estimated that only 59% of the electrical generating capacity would be available for use by the distribution system over and above the electricity required by the broiler houses that supply litter to the plant. The amount of litter produced on broiler farms is theoretically adequate to provide enough heat to eliminate the purchase of propane for space heating but is limited by heating system efficiency. The amount of land needed to accommodate the ash from an on-farm litter furnace was estimated to be about 20 ha per broiler house. Many technical and economic obstacles need to be overcome to see large scale use of litter as a source of biomass fuel.