The influence of electrolytic hydrogen provision degree in the process integrated with biomass gasification, power-to-gas and biomethanation: A techno-economic assessment

The syngas produced from biomass gasification is a great potential energy resource, which can well be utilized to produce biomethane via syngas biomethanation. Integrated with power-to-gas, it can be a promising technology to provide long term energy storage and increase the flexibility of electricity production. This study first established a novel model of the process integrated with biomass gasification, power-to-gas and biomethanation and considered the recovery of heat and by-products. Then, the techno-economic performance of five scenarios was assessed where different amounts of electrolytic hydrogen were provided to achieve the residual carbon conversion proportion of 0, 25 %, 50 %, 75 % and 100 %, respectively. With the increase of hydrogen provision, the biomethane yield rises linearly from 219.94 Nm3 t−1 to 442.46 Nm3 t−1, and the cold gas efficiency rises from 39.64 % to 44.94 %. The expansion of electrolysis scale also increases the total capital investment from 127.37 MCNY to 203.49 MCNY, and the operating costs from 25.62 MCNY year−1 to 43.21 MCNY year−1. The purchased equipment cost proportion of the electrolysis section has finally increased to 31.95 %. However, power-to-gas reduces the biomethane minimum selling price from 12.54 CNY Nm−3 to 10.35 CNY Nm−3. That means the costs of implementing electrolysis are compensated by the higher biomethane productivity obtained when the power-to-gas electricity price is below 0.39 CNY kWh−1. According to the sensitivity analysis, the market competitiveness of biomethane can be further enhanced by reducing costs of investment and raw materials, as well as receiving policy subsidies.