Feasibility and pilot study of coupled anaerobic digester and pyrolyzer for co-processing organic waste to renewable natural gas and biochar

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Anaerobic digestion (AD) technologies can produce carbon-neutral renewable natural gas (RNG) that significantly decarbonizes the energy system and reduces GHG emissions. Additional benefits include reducing local atmosphere pollution from animal waste storage and land spreading, maximizing the value of biomass waste and producing organic fertilizers from digestate to reduce the overall cost of RNG production. There are some small-scale facilities in British Columbia for anaerobic digestion of agricultural waste and urban source-separated organics for biogas production. However, to deploy AD system broadly for the production of RNG in large quantity at large scale to meet the government's RNG blending target, several challenges still need to be overcome to improve the AD system efficiency in treating various organic waste feedstock, reduce carbon footprint, and better manage the waste digestate streams. Integrated AD-pyrolysis system was a relatively new approach to increase the stability of AD reactor and biogas production, and it has shown a great promise in increasing the overall energy conversion from 33-50% of single AD reactor to more than 80% in the combined AD-pyrolysis system. Majority of studies to date have been performed in components in laboratory or small pilot units without integration. We propose to systematically evaluate the feasibility of an integrated anaerobic digestion and microwave pyrolysis system based on environmental and techno-economic analyses and the test of a small pilot AD reactor and a microwave-assisted fluidized bed pyrolysis reactor. The focus is on the AD reactor performance for co-digestion of crop residues, yard waste, food waste and animal waste with the addition of pyrolysis aqueous liquid (APL) and biochar, microwave catalytic pyrolysis of solids digestate for biochar production and the optimization of biochar properties as an additive to the AD reactor to improve AD performance and for other applications. The overall objective of this project is to provide stakeholders an AD+pyrolysis technology to meet the renewable natural gas blending demands and greenhouse gas emissions reduction targets in British Columbia and Canada.