Emission of greenhouse gases from home aerobic composting, anaerobic digestion and vermicomposting of household wastes in Brisbane (Australia)

Abstract

This study investigated greenhouse gas (GHG) emissions from three different home waste treatment methods in Brisbane, Australia. Gas samples were taken monthly from 34 backyard composting bins from January to April 2009. Averaged over the study period, the aerobic composting bins released lower amounts of CH4 (2.2 mg m-2 h-1) than the anaerobic digestion bins (9.5 mg m-2 h-1) and the vermicomposting bins (4.8 mg m-2 h-1). The vermicomposting bins had lower N2O emission rates (1.2 mg m-2 h-1) than the others (1.5-1.6 mg m-2 h-1). Total GHG emissions including both N2O and CH4 were 463, 504 and 694 mg CO2-e m-2 h-1 for vermicomposting, aerobic composting and anaerobic digestion, respectively, with N2O contributing >80% in the total budget. The GHG emissions varied substantially with time and were regulated by temperature, moisture content and the waste properties, indicating the potential to mitigate GHG emission through proper management of the composting systems. In comparison with other mainstream municipal waste management options including centralized composting and anaerobic digestion facilities, landfilling and incineration, home composting has the potential to reduce GHG emissions through both lower on-site emissions and the minimal need for transportation and processing. On account of the lower cost, the present results suggest that home composting provides an effective and feasible supplementary waste management method to a centralized facility in particular for cities with lower population density such as the Australian cities.