Energy cover crops for biogas production increase soil organic carbon stocks: A modeling approach

• Published in: Global change biology. Bioenergy 2023-02, Vol.15 (2), p.224-238
• Main Authors: Levavasseur, Florent, Kouakou, Patrice K., Constantin, Julie, Cresson, Romain, Ferchaud, Fabien, Girault, Romain, Jean‐Baptiste, Vincent, Lagrange, Hélène, Marsac, Sylvain, Pellerin, Sylvain, Houot, Sabine
• Format: Article
• Language: English
• Subjects: Agricultural practices; Alternative energy sources; AMG; Anaerobic digestion; arable crops; Barley; Biogas; Biomass; Biomass energy production; Carbon; Case studies; Climate change; Corn; cover crop; Cover crops; Crop production; Crops; Food production; France; modeling; Organic carbon; Organic fertilizers; Organic soils; Parameter modification; Production increases; Renewable energy; SOC; Soils; Sorghum; Soybeans; Sys‐Metha; Wheat
• ISSN: 1757-1693; 1757-1707
• DOI: 10.1111/gcbb.13018

Energy cover crops for biogas production through anaerobic digestion (AD) are inserted between two primary crops. They replace either bare soil or nonharvested cover crops, and their management is usually intensified to produce more biomass. They allow the production of renewable energy as well as digestate, used as an organic fertilizer, without directly competing with food production. Because of the increased biomass production and export and of the return of a digested biomass to the soil, the impact of energy cover crops on soil organic carbon (SOC) is questioned. The objective of this paper was to study the difference in SOC stocks induced by the introduction of energy cover crops for AD coupled with the application of the resulting amount of digestate. We used the AD model Sys‐Metha combined with the soil C model AMG to simulate SOC stocks for 13 case studies in France, with scenarios comparing different intercrop management practices, with or without cover crops, harvested or not. Our results indicated that the higher biomass production of energy cover crops (from 6.7 to 11.1 t DM ha−1) in comparison with nonharvested cover crops (2 t DM ha−1) or bare soil led to higher humified C input (belowground input and digestate), despite the high C fraction exported in AD. This resulted in an increase in SOC stocks in comparison with nonharvested cover crops or bare soil (from 0.01 to 0.12 t C ha−1 year−1 over 30 years). The uncertainties in the model parameters did not modify these results. However, in the case of equal biomass production between energy cover crops and nonharvested cover crops, SOC stocks would be lower with energy cover crops. Résumé Les cultures intermédiaires à vocation énergétique (CIVE) pour la production de biogaz par méthanisation sont insérées entre deux cultures principales. Elles remplacent soit le sol nu, soit des cultures intermédiaires non récoltées. Leur gestion est généralement intensifiée pour produire davantage de biomasse. La méthanisation des CIVE permet la production d’énergie renouvelable ainsi que de digestat, utilisé comme engrais organique, sans entrer directement en concurrence avec la production alimentaire. En raison de l’augmentation de la production et de l’exportation de biomasse et du retour au sol d’une biomasse digérée, l’impact des CIVE sur le carbone organique du sol (SOC) est questionné. L’objectif de cet article était d’étudier la différence de stocks de carbone organique du sol induite par l’introductio