Amine scrubber upgrading

An amine scrubber takes carbon dioxide out of the biogas into a solvent. The biogas is not compressed to drive the separation. The columns, the solvent circuit, and the equipment that regenerates the solvent are why the capital cost is higher than a cascade or a membrane skid. The operating cost is lower, because the plant is not paying to compress every cubic metre the way a membrane train does.

The solvent is regenerated and reused. The carbon dioxide leaves at that step. Hydrogen sulfide is not left for the column to discover; it is removed first. See hydrogen sulfide scrubbers. The methane-rich gas can go on to injection or to bio-LNG. Hydrogen biomethanisation is the route that converts the carbon dioxide into methane instead of scrubbing it out.

See biomethane upgrading.