Comparative Life Cycle Assessment of Food Waste Management Systems: An Evaluation of a Novel Anaerobic Digestion Technology

Abstract

Resource recovery has the potential to capture energy and nutrients from municipal organic wastes and convert them to useful products while reducing environmental impacts. We developed a novel two-phase anaerobic dynamic membrane bioreactor (AnDMBR) that can achieve a high overall methane yield at a low hydraulic retention time to increase energy recovery from food waste and sewage sludge. We utilizedlife cycle assessment to evaluate the environmental impacts of the novel two-phase system in comparison to conventional food waste and sewage sludge management optionsin the United States. Co-management of food and sewage sludge waste streams throughco-digestion was shown to maximize energy recovery and hada net global warming benefit, while minimizing other environmental impacts. The net impacts of anaerobic digestion(AD)systems weremost sensitive to the background electric grid mix, as the benefits of displacing grid electricity with electricity produced from biogas decline when fossil fuel sources are replaced with renewableenergy sources like solar and wind. Upgrading biogas to renewable natural gasto displace the use of fossil natural gas for other energy requirements that are difficult to decarbonize may sustain the environmental benefits of utilizing AD to producebiogas from municipal organic waste streams in the long-term.