Feasibility study on combining anaerobic digestion and biomass gasification to increase the production of biomethane

• Anaerobic digestion and biomass gasification are integrated.
• The novel concept can produce much more biomethane.
• The novel concept can improve the exergy efficiency.
• The novel concept demonstrates a big potential of income increase.

There is a rapid growing interest in using biomethane as fuel for transport applications. A new concept is proposed to combine anaerobic digestion and biomass gasification to produce biomethane. H2 is separated from the syngas generated by biomass gasification in a membrane system, and then is used to upgrade raw biogas from anaerobic digestion. Simulations have been conducted based on the real operation data of one full scale biogas plant and one full scale biomass gasification plant in order to investigate the feasibility of the new concept. Results show that although less power and heat are generated compared to the gasification plant, which results in a lower overall efficiency, much more biomethane can be produced than the biogas plant; and the new concept can achieve a higher exergy efficiency. Due to the increasing price of biomethane, the novel concept demonstrates a big potential of income increase. For example, at a biomethane price of 12.74SEK/kg, the annual income can be increased by 5.3% compared to the total income of the biogas and gasification plant.