Environmental benefits of using turkey litter as a fuel instead of a fertiliser

Abstract

There is an increased interest in the use of poultry litter as fuel by the relevant industries. Hence the environmental impacts of using turkey litter as fuel to generate electricity instead of using litter as fertilizer were systematically analysed for the first time. For this purpose, a systems modelling-based life cycle assessment approach was used, with data obtained directly from the UK turkey industry. Impacts were calculated per 1000 kg turkey live weight produced at the farm gate (functional unit). The avoided burdens method was used to quantify the effects of the alternative litter use. Differences in the environmental impacts between the two litter use scenarios resulted from the combined effect of the following sub-processes: the loss of nitrogen as a crop fertiliser, the transport for collecting litter and distributing the ash as a phosphorus and potassium fertiliser, displacement of electricity generation by a combined cycle gas turbine, specific trace gas emissions from combustion and the loss of soil carbon from the reduced organic matter supply to arable soils. The results showed that there are substantial environmental benefits from using turkey litter as a fuel to generate electricity rather than using it directly as a fertiliser with reductions in burdens of cumulative primary energy demand (14%), eutrophication potential (55%) and acidification potential (70%). The reduction in acidification and eutrophication potentials were mainly associated with reduced ammonia emissions from the storage and land spreading of the litter. Reductions in greenhouse gas emissions were small (3%) because losses of soil carbon as a result of not applying litter to land partially counteracted the benefits of reduced fossil energy use. Small increases in nitrogen oxides, volatile organic carbon, particulate matter below 10 μm aerodynamic diameter and dioxin emissions were found, although only nitrogen oxides were especially linked to combustion. Despite its potential benefits, stringent management, monitoring and regulation of biomass fuelled power production is still needed, given the potential hazards of local high emissions. Although turkey litter was analysed in this study, similar results can be expected for broiler litter use as a fuel, as long as geographical conditions are similar.