Asahi Kasei has a long track record in catalyst development and gas separation technologies. Based on this technological foundation, the company has developed a system that separates CO2 and methane from biogas using the optimum combination of a special pressure vacuum swing adsorption (PVSA) process technology and a novel zeolite as an adsorbent. This unique configuration removes CO2 from biogas to obtain biomethane with high purity and high yield. A zeolite is a crystalline aluminosilicate having regular pores and cavities controlled on the order of angstroms (ten-millionths of a millimeter) with a specific surface area of several hundred square meters per gram.
To verify the performance and operational stability of this system under actual operating conditions, Asahi Kasei has conducted a demonstration trial using a portion of biogas generated from sewage sludge at the Kojima Sewage Treatment Plant in Kurashiki City, Okayama Prefecture, since February 2025.
In the purification of biomethane, there tends to be a trade-off between high purity and high yield; achieving both together has been a significant technical challenge. The first course of this demonstration was performed with continuous operation for a period of one month. The biomethane obtained was confirmed to be over 97% pure, suitable for use as fuel by feeding into a natural gas pipeline injection or as CNG. A high yield of over 99.5% was also confirmed, indicating successful achievement of both high purity and high yield performance.
