♻️ What if every sewage treatment plant could also be a power station? Toray Industries has demonstrated its "all-carbon CO2 separation membrane" purifying biogas at a sewage treatment facility in Osaka Prefecture. Cost has long been what stopped biogas power generation; a 70% cut in dehumidification costs changes that arithmetic.

Turning Waste into Methane

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 had about 2,200 sewage treatment plants as of the end of fiscal 2022, and the organic content of sewage sludge is conventionally reckoned at 80%. According to Japan's Ministry of Land, Infrastructure, Transport and Tourism, the total energy in that organic matter comes to roughly 12 billion kWh a year in heat terms, about 1.6 times the annual electricity consumption of all sewage treatment plants nationwide. Used properly, these facilities could shift from energy consumers to energy producers.

As of fiscal 2022, however, only about 26% of the organic matter in sewage sludge was being used for energy. The main barrier has been the 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 using polymer or zeolite membranes has a critical weakness: separation performance falls off sharply on contact with moisture. Operators therefore had to dry the gas first with adsorbent-based dehumidification equipment, a pre-treatment step that enlarged the plant and drove up 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 correctly sized pores separates them like a molecular sieve. CO2 has a molecular diameter of 0.330 nanometers, methane 0.380. The membrane works off that tiny gap.

On January 9, 2026, Toray announced it had demonstrated simultaneous removal of CO2 and moisture at a biogas production facility inside an Osaka Prefecture sewage treatment plant. Against existing membrane separation technology, dehumidification costs came down by roughly 70%. Simplifying the moisture-removal step also makes the purification plant itself more compact.

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 produced continuously using methods similar to standard fiber manufacturing, lowering the barrier to mass production. Toray has installed a pilot facility at its Shiga plant in Otsu to establish those production methods, and aims to commercialize the CO2 separation membrane element during fiscal 2026, targeting sales of 10 billion yen (roughly $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

The government has set targets to raise the share of sewage sludge used for energy, and expanding biogas power generation is essential to meeting them.

For municipalities and companies that wanted biogas but dropped the idea on cost, a 70% reduction could be reason to look again. If all 2,200 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?

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