Fluidized bed combustion of poultry litter at farm-scale: Environmental impacts using a life cycle approach

Abstract

Combustion can concentrate phosphorus (P) from poultry litter into an ash product that is easier to transport for land application. This was the first life cycle assessment (LCA) study to investigate the efficacy and sustainability of a fluidized bed combustion (FBC) system using poultry litter to heat poultry houses and produce electricity, in the United States, to replace liquid propane gas (LPG) and natural gas (NG) use. The ‘Baseline scenario’ used results from a 16-month FBC monitoring study, and an ‘Improved scenario’ based on an increased biomass feed rate (0.246 tons/h), increased run-time (6720 h/y), and net positive electricity production. In the Baseline scenario, climate change potential was 32% and 44% lower than use of LPG and NG, respectively, for poultry house heating, but the low electricity production from the FBC system resulted in net electricity import and lower sustainability compared to LPG use in 12 of the 18 impact categories. The Improved scenario had 48–98% less environmental impacts than the Baseline scenario in the 18 categories. The sensitivity analysis showed that a 10% change in the electricity input for FBC operation resulted in the highest average change (4.8%) in the 18 impact categories, indicating the necessity of a net positive electrical energy output from the FBC unit for increased sustainability. The results also highlighted the impact of the replacement heating fuel type, as replacing NG through poultry litter combustion had a greater impact than replacement of LPG.