Biomass sustainability criteria: greenhouse gas accounting issues for biogas and biomethane facilities

Biomass sustainability criteria were introduced in the UK following the EU Renewable Energy Directive. Criteria are now applicable to solid biomass and biogas, however because it is not mandatory criteria can be adapted by member states with the risk of different interpretation. Operators are required to report greenhouse gas (GHG) emissions for every MJ of energy produced. This paper provides a rigorous analysis of the current GHG emissions accounting methodology for biogas facilities to assess expected compliance for producers. This research uses data from operating CHP and biomethane facilities to calculate GHG emissions using the existing methodology and Government calculator. Results show that whilst many biogas facilities will meet GHG thresholds, as presently defined by Government, several operators may not comply due to methodological uncertainties and chosen operating practices. Several GHG accounting issues are identified which need to be addressed so the biogas industry achieves its reporting obligations and is represented objectively with other bioenergy technologies. Significant methodological issues are highlighted; including consignment definition, mass balance allocation, measurement of fugitive methane emissions, accounting for digestate co-products, fossil fuel comparators, and other accounting problems. Recommendations are made to help address the GHG accounting issues for policy makers and the biogas industry.