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6233696 
Book/Book Chapter 
Chapter 9 - GHG Emissions From Biomethane Gas-to-Grid Injection via Anaerobic Digestion 
Adams, P 
2018 
Academic Press 
Greenhouse Gas Balances of Bioenergy Systems 
141-158 
Biomethane is a versatile fuel produced via anaerobic digestion (AD) and applied to several end-uses. Farm-derived feedstocks offer a large potential biomass resource which can be used to produce biomethane. Farm wastes and residues such as manures and slurries are abundant and existing management options include direct spreading to land which can increase emissions. AD provides farms with on-site waste management that produces both organic fertilizer and biogas. Due to the seasonality and lower biogas yields of residues, crop silage is commonly used to increase energy outputs and improve the economics. This chapter evaluates the potential GHG emissions from the different stages of biomethane production including feedstock supply, anaerobic digestion, and biogas upgrading. GHG assessments of farm-derived biomethane show a wide range of results due to the feedstock type, management of the facility, and technology configuration. Farm wastes can result in negative emissions with AD if the counterfactual of traditional management is considered. Crop silage tends to have much higher GHG balance with the use of N-fertilizer, the dominant emission source. Fugitive methane emissions from biogas production and upgrading can reduce the GHG benefits of AD, so well-operated facilities are important. This chapter aims to provide the reader with an overview of the key considerations when conducting a GHG assessment of biomethane production. 
Anaerobic digestion; Biomethane; Fugitive methane; Greenhouse gas; Land use; Methane; Sustainability 
Thornley, Patricia