Economic and environmental impacts of an integrated-state anaerobic digestion system to produce compressed natural gas from organic wastes and energy crops

Anaerobic Digestion (AD) is a well-developed sustainable technology to convert organic waste streams and energy crops to produce renewable gaseous biofuels, while recycling nutrients and mitigating greenhouse gas emissions. In this study, the environmental and economic impacts of an integrated-state AD technology (i-AD) producing Compressed Natural Gas (noted as BioCNG) were investigated from dairy-manure, food-wastes, and miscanthus biomass feedstocks, and compared with that of stand-alone liquid-state (LS-AD) and solid-state (SS-AD) AD technologies. A coupled life-cycle assessment and techno-economic analysis (LCA‐TEA) approach was used to estimate the Global Warming Potential (GWP) and the Minimum Selling Price (MSP) of BioCNG ‒ a renewable alternative to fossil-CNG. The results illustrated that the Fossil Energy Ratios (FERs) for BioCNG were between 2.3 and 3.3 in the increasing order as LS‐AD