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Asahi Kasei to construct biogas purification system at sewage treatment plant in Kurashiki, Okayama, Japan – demonstration trial on CO2 separation/recovery utilizing zeolite

Düsseldorf, Germany, September 15, 2022 – Asahi Kasei and Kurashiki City today concluded an agreement to hold a trial to evaluate and demonstrate the performance of a biogas purification system (the System) at a sewage treatment plant in the city. Earlier in the day, the Mizushima Works of Asahi Kasei’s Production Center and Kurashiki City concluded a comprehensive partnership agreement for the realization of carbon neutrality in society. Advancing the demonstration trial for decarbonization is one of the provisions of the partnership.

The System refines high-purity methane gas (biomethane) by removing CO2 from biogas utilizing Asahi Kasei’s newly developed adsorbent, K-GIS zeolite, which selectively adsorbs CO2. Unlike conventional adsorbents which adsorb methane together with CO2, K-GIS zeolite adsorbs almost no methane. This enables the System to efficiently separate and recover high-purity methane while recovering high-purity CO2.

Figure 1: Crystal structure of the new adsorbent, K-GIS zeolite – the size of cavities in the crystal is slightly larger than the CO2 molecule, which allows CO2 to enter the crystal and be adsorbed while larger molecules such as methane are excluded.

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 and the U.S.

Figure 2: The flow of biogas – high-purity methane refinement is conducted mainly in Europe.

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. If biomethane production using the System is combined with carbon capture and utilization or storage (CCUS), the cycle would be carbon negative. In the demonstration trial, the separated gases are recombined to biogas as fuel for generating electricity.

Figure 3: Biogas flow at the Kojima Sewage Treatment Plant in Kurashiki City, and the demonstration trial using the System.


Fabrication of equipment in November 2022
Start of installation in May 2023
Start of operation at the end of 2023


Kojima Sewage Treatment Plant, Kurashiki, Okayama Prefecture, Japan

Standort: Kläranlage Kojima, Kurashiki, Präfektur Okayama, Japan, Kojima Sewage Treatment Plant

Roles of participants:

  • Asahi Kasei will design, install, and operate the System, and evaluate and demonstrate its performance
  • Kurashiki City will provide biogas generated from sewage sludge and the site for the demonstration trial

Commercialization of the System is expected around 2025 or 2026 following additional trials in countries or regions where biogas purification is performed. The technology will also be applied to CO2 separation and recovery from gases other than biogas. The Asahi Kasei Group contributes to life and living for people around the world. It is expected that commercialization of the CO2 adsorbent and the biogas purification system based on original technology will help society to effectively utilize clean environmental energy.

About the Asahi Kasei Corporation
The Asahi Kasei Group contributes to life and living for people around the world. Since its foundation in 1922 with ammonia and cellulose fiber businesses, Asahi Kasei has consistently grown through the proactive transformation of its business portfolio to meet the evolving needs of every age. With more than 46,000 employees around the world, the company contributes to a sustainable society by providing solutions to the world’s challenges through its three business sectors of Material, Homes, and Health Care. Its Materials sector, comprised of Environmental Solutions, Mobility & Industrial, and Life Innovation, includes a wide array of products from battery separators and biodegradable textiles to engineering plastics and sound solutions.

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Asahi Kasei is also dedicated to sustainability initiatives and is contributing to reaching a carbon neutral society by 2050. To learn more, visit

North America Media Inquiries
ATTN: Jonathan Todd
Asahi Kasei America, Inc.

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ATTN: Sebastian Schmidt
Asahi Kasei Europe GmbH