Emissions associated with the management of household organic waste, from collection to recovery and disposal: A bottom-up approach for Sydney and surrounding areas, Australia

Abstract

Recent advances in waste management policies and initiatives world-wide have placed greater focus on the potential greenhouse gas emissions-avoidance that can be achieved via sustainable waste management practices. In New South Wales, Australia, household organic waste has been identified as a problematic stream that through better management, could lead to better environmental outcomes and reduced emissions. However, emissions associated with waste management are poorly characterised in Australia, obscuring decision making around optimal pathways that can maximise landfill diversion and minimise emissions. This study addresses this data limitation by estimating and analysing the emissions associated with household organic waste management. The approach applied route optimisation to estimate emissions from points of collection (weekly and fortnightly) to recovery at composting facilities and disposal at landfills, as well as mass balance modelling to estimate direct and indirect emissions associated with windrow composting and mechanical biological treatment. Landfill gas modelling was also used to estimate lifetime emissions from disposal, as well as potential avoided emissions through recovery. Results for the Greater Sydney and surrounding area show total gross greenhouse gas emissions of approximately 390,100 tCO2-e, and balanced by approximately 145,600 tCO2-e of emissions avoidance through landfill diversion. The average net emissions intensity of jurisdictions in the study area was approximately 133 kgCO2-e/t of waste diverted; or 423 kgCO2-e/t of waste managed. Emissions intensity was highest for the mixed waste collection stream, where diversion pathways are limited; and lowest where separate food collection and mechanical biological treatment was employed. Findings indicate that greater separation of food waste from the mixed stream to dedicated food waste collection will result in the greatest improvements in both emissions intensity and landfill diversion.