Valorisation of Poultry Litter: A socio-environmental costbenefit comparison of traditional land application and anaerobic digestion

Traditional land application of poultry litter (PL) as a fertiliser has led to numerous environmental issues, including eutrophication and soil acidification. An alternative valorisation option is, therefore, sought. Anaerobic digestion (AD) of PL is an emerging field that shows promise and benefits from both energy and fertiliser production. This study aimed to compare the economic, environmental, and social costs and benefits of land application and AD of PL using a modified economic life cycle assessment (LCA) approach. Using economic data from literature and industry reports, a model for each method was created to calculate key economic markers, including net present value (NPV). LCA was incorporated into the model with the environmental emissions of each method being calculated for Global Warming Potential (GWP), Acidification Potential (AP), Freshwater Eutrophication (FE), Photochemical Ozone Potential (POP), and Particulate Matter Formation Potential (PMFP) impact categories. The social value of these impact categories was applied to the emissions data to calculate a socio-environmental cost (or benefit) for each method. Using Monte Carlo simulation, the model shows that AD performs worse when focusing purely on the economic category with an NPV of £707.17 per tonne of PL, compared to £1838.36 per tonne for land application of fresh PL. However, when factoring in the environmental costs, both methods generated a negative NPV. However, AD is shown to be less environmentally damaging than direct land application with an NPV of -£1354.17 per tonne of PL compared to -£5788.34 for direct land application. Furthermore, the model showed that it is possible to optimise the AD process to generate a positive economic and socio environmental NPV, through operational control of biogas and energy production. Further research is needed in this area to determine the optimal parameters to operate a PL mono-digestion AD process for economic and socioenvironmental gain.