♻️ What if every sewage treatment plant could become a power station?

Toray Industries has successfully demonstrated its "all-carbon CO2 separation membrane" at a sewage treatment facility in Osaka Prefecture, Japan. With a remarkable 70% reduction in dehumidification costs, biogas power generation is becoming economically viable like never before.

What Is Biogas Power Generation?

Biogas power generation uses methane gas produced through anaerobic fermentation of organic waste like food scraps and sewage sludge as fuel. It transforms waste into energy without relying on fossil fuels, making it a promising technology for building a circular economy.

Japan has approximately 1,500 sewage treatment plants, and about 80% of sewage sludge consists of organic matter. According to Japan's Ministry of Land, Infrastructure, Transport and Tourism, the energy potential of sewage sludge, when converted to heat value, is equivalent to roughly 1.6 times the annual electricity consumption of all sewage treatment plants nationwide. In other words, proper utilization could transform these facilities from energy consumers into energy producers.

However, as of 2022, only about 26% of sewage sludge is being converted to energy. The primary barrier has been the high cost of biogas purification.

The Challenge with Conventional Technology

Biogas contains not only methane (the fuel component) but also CO2 and significant amounts of moisture. Purifying this gas to a level suitable for power generation requires removing these impurities.

Conventional membrane separation technologies using polymer membranes or zeolite membranes have a critical weakness: their separation performance deteriorates significantly when exposed to moisture. This meant that before purifying biogas, operators needed to remove moisture using adsorbent-based dehumidification equipment. This pre-treatment process led to larger facilities and increased costs.

As a result, despite understanding the environmental benefits, many municipalities and companies abandoned biogas projects due to economic barriers.

Toray's Innovation Changes the Game

Toray's all-carbon CO2 separation membrane addresses this challenge at its core. Since announcing the foundational technology in 2021, the company has continuously refined it for practical application.

The membrane's key feature is its composition entirely of carbon fiber, making it impervious to moisture damage. It consists of a two-layer structure: a hollow fiber porous carbon fiber support with a diameter of less than 300 micrometers, coated with a thin carbon separation layer just a few micrometers thick.

Since CO2 and methane have different molecular sizes, passing mixed gas through a membrane with appropriately sized pores allows selective separation—like a molecular sieve. CO2 has a molecular diameter of 0.330 nanometers while methane measures 0.380 nanometers. The membrane exploits this tiny difference for selective separation.

In January 2026, Toray announced successful demonstration at a biogas production facility in an Osaka Prefecture sewage treatment plant, confirming simultaneous removal of CO2 and moisture. Testing verified approximately 70% reduction in dehumidification costs compared to conventional technology.

Technical Advantages and Future Prospects

Beyond cost reduction, this membrane offers several important advantages.

First, it enables compact equipment design. The hollow fibers are extremely thin and flexible, allowing high-density packing. Compared to conventional inorganic CO2 separation membrane modules, it achieves up to five times the CO2 permeation volume in the same space.

Second, the fibers can be continuously produced using methods similar to standard fiber manufacturing, lowering barriers to mass production. Toray plans to operate a pilot facility at its Shiga site by fiscal 2025 and aims for commercialization by fiscal 2026, targeting sales of 10 billion yen (approximately $67 million) by 2035.

Furthermore, this technology shows promise beyond biogas purification. Applications include natural gas refinement and CO2 separation and capture from industrial exhaust gases (CCUS).

Impact on Japan's Biogas Utilization

This technological demonstration carries significant implications for Japan's energy policy. The government has set targets to increase sewage sludge energy utilization rates by 2030, and biogas power generation expansion is essential to achieving them.

For municipalities and companies that previously wanted to adopt biogas but abandoned plans due to high costs, a 70% cost reduction could prompt reconsideration of biogas power as a realistic option. If all 1,500 sewage treatment plants across Japan functioned as small-scale power stations, a distributed regional energy supply network could emerge.

Additionally, since this development received support from NEDO (Japan's New Energy and Industrial Technology Development Organization), widespread adoption could contribute meaningfully to Japan's carbon neutrality goals. Experts suggest it could particularly improve the economics of "biomass-derived fuel conversion" projects under Japan's J-Credit system.

When a Nuisance Becomes a Resource

Toray is trying to pry open biogas power's toughest barrier—cost—with the properties of a material. And a path is emerging to turn sewage, an unavoidable byproduct of daily life, into an energy resource.

The one-year long-term demonstration is still running. Depending on how it goes, treatment plants across Japan could shift from being facilities that consume electricity to ones that generate it.

Japan's push to draw energy from sewage sludge is now underway. In your country, how is energy recovery from sewage or biomass waste progressing?

References