Development of Biomethanation Technology for Utilization of Unused CO₂ in Biogas

Overview

Biomethanation is the technology of producing methane from carbon dioxide and hydrogen through the action of microorganisms.

Osaka Gas is working on technology development to produce e-methane from carbon dioxide in biogas produced by methane fermentation and green hydrogen.¹

1. Hydrogen produced without emitting CO₂ in the production process, typically using renewable energy

Background

In recent years, methane fermentation has been attracting attention as a carbon-neutral energy source because it allows recovery in the form of biogas from waste, containing 60% methane and 40% carbon dioxide.

While methane in biogas can be used to produce thermal energy, carbon dioxide accounting for 40% cannot be used as it is. Osaka Gas focused on biomethanation as a way to utilize this unused carbon dioxide.

Biomethanation Programs of Osaka Gas

Since November 2022, Osaka Gas has been conducting a field test² on biomethanation using biogas generated at a sewage treatment plant, jointly with Kyoto University, NJS Co., Ltd., and the municipal government of Osaka.

This field test uses a small-scale test facility newly constructed at the Ebie Sewage Treatment Plant in Osaka.

In fiscal 2022, sewage sludge and hydrogen were fed into the test facility, biogas was produced from the sewage sludge under the same conditions as those of the sewage treatment plant, and biomethanation was performed to synthesize e-methane from CO₂ contained in the biogas and hydrogen, using microorganisms.³

In fiscal 2023, a verification will be conducted to increase the volume of biogas generated, by feeding lactic acid, a decomposition product of waste bioplastics, into the test facility.

We will proceed with the verification of biomethanation that will not affect the biogasification of sewage sludge, aiming for future full-scale introduction.

2. Technology under development is tested using equipment in an environment that simulates actual usage conditions.

3. The method of performing both biogasification and methanation in the same equipment is called the “in-situ method.” This method can use existing biogasification equipment at the sewage treatment plant, eliminating the need for new methanation equipment and making it easy to introduce.