Life cycle analysis of anaerobic digestion processes of poultry litter

Abstract

This article presents results of life-cycle assessment of anaerobic digestion processes of poultry litter (PL) preceded or not by thermal pretreatment (autohydrolysis). For this, the environmental impact categories, greenhouse gas (GHG) emissions, eutrophication, and soil acidification were evaluated using the ReCiPe Midpoint (H) method. Based on primary data provided by a partner company, life-cycle inventories were constructed for three forms of poultry waste management: i. disposal of in natura PL into the soil, which is the commonly used management technique; ii. anaerobic digestion of in natura PL; and iii. thermal pre-treatment by autohydrolysis of PL before its anaerobic digestion. It is concluded that anaerobic digestion of PL reduces GHG emissions compared to the “business as usual” scenario of soil disposal. The use of digestate (liquid fraction generated by PL anaerobic digestion) as soil fertilizer would result in avoided GHG emissions of 34%, while thermal pre-treatment by autohydrolysis of PL prior to its anaerobic digestion would result in a slightly lower reduction (27%) in GHG. Anaerobic digestion of in natura PL would also reduce the eutrophication potential by 98.2% (kg eq PO4-3/t litter) and the acidification potential by 98.4% (kg eq SO2/t litter) compared to its soil disposal. These results show that anaerobic digestion is a more sustainable way to manage PL than its environmental discharge.