Enhancing biomethane production by biochar addition during anaerobic digestion is economically unprofitable.

The societal demand for biomethane production by anaerobic digestion of waste and biomass is rapidly growing to build a circular economy, yet actual efficiency is limited. Biochar addition has been technically shown to enhance methane yields in general, but economics are unknown so far. Here, we evaluated the profitability of adding biochar into orange peel waste using the method of the discounted cash flow. We also studied biochar prices and incentives for biomethane production. Results indicate that adding biochar decreases 17 times the overall economy of the process. This decline is explained by high current prices of biochar. To reach profitability, subsidies should be higher than 20 Eur per MWh of biomethane. [ABSTRACT FROM AUTHOR]