Large-scale development of biogas production in France: Improved climate benefits over the long term compared to biomass burial

Numerous studies have highlighted anaerobic digestion's (AD) role in mitigating greenhouse gas (GHG) emissions, but no one has thoroughly considered its long-term soil organic carbon effects nor compared these emissions to the most frequent alternative biomass use, i.e. soil burial. Using a spatially explicit modelling approach combining an anaerobic digestion and a soil carbon model, we assessed the long-term impact on GHG net emissions of agricultural biomass AD vs. direct soil burial at the national scale of France. We found that AD more efficiently mitigated GHG net emissions than direct burial, primarily through fossil fuel substitution and lowered manure storage emissions. Interestingly, we found that while AD initially reduced soil carbon storage compared to direct burial, both usages converged in the long-term. Biogas grid injection could save 10.8 Mt. CO_{2 eq}/year at the national scale of France, potentially reaching 17.1 Mt. CO_{2 eq}/year with widespread cover crops (amounting to respectively 2.6 and 4.1 % of national GHG emissions). This study provides valuable perspectives for fostering sustainable development within the AD sector as well as a methodology that can be adapted to diverse agricultural and geographical contexts.