廃棄物から直接再生可能天然ガスを生成する技術を開発（Researchers develop method to make renewable natural gas directly from waste）

2026-04-21 ワシントン州立大学（WSU）

As part of the project, the team used a novel bacterial strain to upgrade the biogas in a reactor, converting carbon dioxide with hydrogen into methane or renewable natural gas (photo courtesy of WSU).

＜関連情報＞

• https://news.wsu.edu/press-release/2026/04/21/researchers-develop-method-to-make-renewable-natural-gas-directly-from-waste/
• https://www.sciencedirect.com/science/article/pii/S1385894726013902?ref=pdf_download&fr=RR-2&rr=9dd718732be47669

高度前処理・嫌気性消化技術（APAD）による下水汚泥の嫌気性消化から再生可能な天然ガスへの変換の改善：パイロット試験 Improving anaerobic digestion of sewage sludge to renewable natural gas by the Advanced Pretreatment & Anaerobic Digestion technology (APAD): Pilot testing

Birgitte K. Ahring, Fuad Ale Enriquez, Muhammad Usman Khan, Peter Valdez, Francesca Pierobon, Timothy E. Seiple, Richard Garrison
Chemical Engineering Journal  Available online: 9 February 2026
DOI:https://doi.org/10.1016/j.cej.2026.173931

Highlights

• APAD process boosts carbon conversion efficiency to 83%.
• RNG output increased by 200% with integrated APAD process.
• Advanced pretreatment slashes sludge treatment costs by nearly 50%.
• Biogas upgrading via M. wolfeii BSEL cuts CO₂ to ≤3%.
• Process enables a sustainable path for wastewater decarbonization.

Abstract

Conventional anaerobic digestion (AD) of sewage sludge in wastewater treatment facilities suffers from low carbon conversion efficiency (CCE ≤ 40%) and requires costly CO₂ removal for injection of the produced CH₄ into the natural gas grid. To address these limitations, we developed the Advanced Pretreatment and Anaerobic Digestion (APAD) process. This integrates Advanced Wet Oxidation & Steam Explosion (AWOEx) pretreatment of residual sludge after conventional AD, followed by biogas upgradation using a novel methanogenic strain, Methanothermobacter wolfeii BSEL, converting CO₂ with H₂ into CH₄ or RNG (renewable natural gas). Pilot-scale results demonstrated that AWOEx pretreatment achieved a CCE of 62% for the residual sludge, 68% higher than the conventional AD process. The CH₄ production was further increased by 79%. Subsequent biogas upgrading in a trickling bed reactor with H₂ further enhanced total methane output by 100% and resulted in a final CO₂ concentration of ≤3%. The integrated APAD process achieved a remarkable overall CCE of 83%, resulting in a 200% increase in RNG output when compared to conventional AD. Techno-economic analysis revealed that AWOEx pretreatment alone reduced sludge treatment costs from $494 to $253 per ton of dry solids. The complete APAD process incurred a higher cost of treatment of $530 per ton, driven by prices of bottled H₂. The process did, however, show gains in energy recovery and decarbonization. Renewable H₂, which may reduce in price in the near future, can positively improve the economics of biogas upgrading for the APAD process.