On-site demonstration trial on CO₂ separation/recovery utilizing zeolites

Asahi Kasei and Kurashiki City held a grand opening ceremony on February 4, 2025, for a biogas purification system (the System) in Kurashiki, Okayama Prefecture, Japan. The System uses Asahi Kasei’s CO₂ separation/recovery technology utilizing zeolites installed at a sewage treatment plant. The goal of this collaboration is to evaluate and demonstrate the performance of the System.

Asahi Kasei and Kurashiki City concluded a comprehensive partnership agreement for the realization of carbon neutrality in society on September 15, 2022. Advancing the demonstration trial for decarbonization is one of the provisions of the partnership.

The System separates CO₂ and methane from biogas using the optimum combination of a special zeolite as adsorbent that selectively adsorbs CO₂ and a special pressure vacuum swing adsorption (PVSA) process technology. The zeolite is a crystalline aluminosilicate having regular channels (pores) controlled on the order of angstroms (ten-millionths of a millimeter) and cavities (voids) with a specific surface area exceeding several hundred square meters per gram. Asahi Kasei’s PVSA process technology, which separates specific gases by changes in pressure, enables the removal of CO₂ from biogas to refine high-purity methane gas (biomethane) at a high recovery rate.

Biogas from sewage sludge, garbage, etc., consists of approximately 60% methane and 40% CO₂. While the use of biogas as a carbon-neutral fuel is rapidly expanding, it is also a source of biomethane as a substitute for natural gas in Europe, the U.S., and other regions.¹

The flow of biogasification and biogas upgrading/purification to high-purity methane

In Kurashiki City, electricity is generated using biogas derived from sewage sludge at the Kojima Sewage Treatment Plant. The System will use a portion of this biogas for the demonstration trial. Furthermore, if the CO₂ separated by this System is utilized and/or stored, it would achieve carbon capture, utilization, and storage (CCUS), which is carbon negative. In the demonstration trial, the separated methane is returned and used as fuel to generate electricity for effective utilization of the biogas.

Biogasification flow at the Kojima Sewage Treatment Plant in Kurashiki City, and the demonstration trial using the System

The demonstration trial at the Kojima Sewage Treatment Plant began in February 2025. Asahi Kasei is responsible for the design, installation, and operation of the System, as well as evaluating and demonstrating its performance, while Kurashiki City supplies biogas generated from sewage sludge in addition to providing the site for the trial.

Commercialization of the System is expected around 2027 following additional trials in countries or regions where biogas purification is performed.

“We are excited to start the on-site demonstration trial of a biogas purification system using Asahi Kasei’s zeolite and PVSA process technology,” says Osamu Matsuzaki, Senior Executive Officer of Asahi Kasei and Senior General Manager of Corporate Research & Development. “As the next step, by expanding co-creation partnerships globally, we will accelerate the advancement and practical implementation of this outstanding technology that can reduce environmental impacts, contributing to sustainability for the world.”

• ¹Please refer to the following webpages
  International Energy Agency | Special section: Biogas and biomethane
  https://www.iea.org/reports/renewables-2023/special-section-biogas-and-biomethane
  European Commission | Biomethane
  https://energy.ec.europa.eu/topics/renewable-energy/bioenergy/biomethane_en