Modeling the water scrubbing process and energy requirements for CO2 capture to upgrade biogas to biomethane

Water scrubbing is the most widely used technology for removing CO2 from biogas and landfill gas. This work developed a rate-based mass transfer model of the CO2–water system for upgrading biogas in a packed bed absorption column. The simulated results showed good agreement with both a pilot-scale plant operating at 10 bar, and a large-scale biogas upgrading plant operating at atmospheric pressure. The calculated energy requirement for the absorption column to upgrade biogas to 98% CH4 (0.23 kWh Nm–3, or 4.2% of the input biogas) is a significantly closer approximation to the measured value (0.26 kWh Nm–3, or 4.8% of the input biogas) than has previously been reported in the literature. The model allows for improved design of CO2 capture and biogas upgrading operations and can also be a useful tool for more detailed cost–benefit analysis of the technology.