Biogas from source separated organic waste within a circular and life cycle perspective. A case study in Ontario, Canada

The appropriate transformation and valorisation of biogas offers environmental and economic opportunities in a future with restrictions upon fossil-based fuels and materials. The LCA method was used to quantify and compare the potential environmental impacts of an AD plant incorporating biogas co-generation and upgrading options, namely AD-CHP and AD-RNG. Using an average Anaerobic Digestion facility in Ontario, Canada, modelled after real facilities, as a case study, electricity and steel were identified as potential hotspot input materials carrying a disproportionate environmental burden for biogas production. With a system expansion approach, the biogas was subsequently utilized to produce (1) both heat and electricity using a Combined Heat and Power (CHP) system, or (2) upgraded to renewable natural gas (also called biomethane) through chemical amine scrubbing, respectively. In comparing the biogas co-generation and upgrading options, the AD-CHP alternative resulted in a lesser environmental load, two times lower when compared to the AD-RNG biomethane recovery option. Furthermore, the avoided burden of producing fossil-based electricity, natural gas, and chemical fertilizer was analyzed and compared against their renewable counterparts. Significant reductions in emissions and in the depletion of fossil fuels were achieved, thus confirming the positive efforts of diverting organic waste from landfills to reduce organic waste disposal impacts and improve the management of organic waste. The analysis has provided useful insights to bioenergy project developers, policy makers and the scientific community regarding the processing of source separated organic waste, biogas production, and its upgrading alternatives in a circular economy perspective.