Carbon Balance And Economics: Trade-Offs Or Synergies In The Case Of Anaerobic Digestion Of Cereal Straw?

Summary

Straw is known to crucially contribute to the carbon supply of arable soils, essential for long-term soil fertility and productivity. However, straw also has become an important commodity for material or energetic utilization. A complete straw removal from the field may threaten carbon reproductive capacities and soil fertility. In anaerobic digestion, the carbon is partially returned to the field via digestate, potentially avoiding negative priming effects of carbon depletion or nitrogen immobilization by the wide C:N-ratio of undigested straw. The article at hand evaluates the anaerobic digestion of straw compared to leaving it on the field with regard to carbon dynamics and economic performance in stockless organic farming systems based on scenarios for different soil-climate conditions in Germany. Assuming justified yield increases by integrating a spatio-temporal flexible fertilizer (biogas digestate) into stockless organic farm systems, both carbon stocks as well as economic revenues may be improved, regardless of soil or climatic conditions and despite higher logistic costs. Thus, straw removal, subsequent anaerobic digestion as well as return of biogas digestates may be able to contribute to both preserving soil functions as well as economic sustainability.