Evaluation of Green Waste Management Impacts on GHG Emissions Alternative Daily Cover Compared with Composting

摘要

Green waste is a key component of California's solid waste stream and so is an important target for effective waste diversion. The California Integrated Waste Management Board (CIWMB) reports that about 15 million cubic yards of organics comprised largely of green waste are diverted annually in California. The diverted organics are principally used as compost and mulch in agricultural and urban green areas. In California, one of the most popular alternative waste diversion options is the use of green waste as landfill alternative daily cover (ADC). Green waste ADC reduces the need for importing clean daily cover soil and so helps conserve limited landfill volume. However when landfilled, green waste can generate methane, an important greenhouse gas (GHG), and so may be regarded as environmentally inferior to green waste composting.rnThis study uses GHG emissions estimated from life-cycle inventory methodology to compare green waste ADC and composting alternatives. A United States Environmental Protection Agency (USEPA) based life-cycle inventory methodology was developed that considers differences in transport, material handling, green waste emissions, capture and management, energy impacts, and carbon sequestration. The ADC analysis addresses the range of conditions at landfills particular to California landfills including the extent of gas recovery, the gas collection efficiency and methane energy recovery.rnThis study supports the reported benefits of composting but also shows that green waste ADC can actually be more beneficial in reducing GHG emissions when compared to the composting of green waste. This result indicates the importance of site-specific environmental analysis when considering organics management options.rnIn this study, details of the life-cycle GHG inventory analyses are provided. Results of the comparison between the two green waste management options are presented. The significance and implications of this study are discussed.