ENTERPRISE FUTURE
O-ta & G-ko’s surprise visit
O-ta & G-ko
  • Executive Reasearcher Energy Technology Laboratories Hisao Ohnishi, Dr., Science.
  • O-ta An intellectually curious, energetic but gentle, simple-hearted dog
  • G-ko An eco-friendly, energy-saving and convenience-loving cat

Substantially eliminating the emissions of CO2!

O-ta

G-ko, it was nice to learn about the positive vision to realize carbon neutrality in the previous issue!

G-ko

I have no idea what it is in the first place.

Hi! I’m Hisao Ohnishi, in charge of technology development. G-ko, don't worry! First, I will explain methanation.

Ohnishi

City gas consists mainly of methane (CH4). At present, the Daigas Group uses natural gas as the raw material. Methanation is the technology to produce methane by using hydrogen (H2) and carbon dioxide (CO2) instead of natural gas.

O-ta

What difference does it make compared to the use of natural gas?

Ohnishi

In methanation, CO2 emitted from factories is reused. CO2 is generated again when city gas derived from methanation is used for combustion. However, the amount of CO2 emitted by combustion is the same as the amount of CO2 captured to produce city gas. In other words, CO2 emissions are offset. The concept is as shown in this animated video.

O-ta & G-ko
O-ta

The emissions are net zero. This means that the CO2 emissions are substantially eliminated!

Ohnishi

Exactly! This technology is expected to contribute to “carbon neutrality,” which the Japanese government aims to achieve. Even if the gas production method changes, the gas supply equipment, such as gas holders for storing gas and gas conduits, as well as household gas equipment, can be used without modification. Customers can continue to use gas as before and achieve carbon neutrality efficiently.

G-ko

I continue to use gas as before, and carbon neutrality is achieved without knowing it! I love this idea.

Methanation is just like photosynthesis of plants!?

O-ta

In the previous issue, we learned that the Daigas Group has an “innovative” methanation technology.

Ohnishi

I’m glad you remembered it! Methanation technology has been developed by other companies. Methane (CH4) is produced through reaction of CO2 and hydrogen (H2), which is derived from electrolysis of water (H2O) using renewable electricity. This is a two-step synthesis method. It can be illustrated as shown below.

conventional methanationO-taG-ko

Ohnishi

Obviously, conventional methanation is also effective enough to achieve carbon neutrality. The Daigas Group has proposed to the World Exposition Association(*) that methanation technology to convert CO2 components contained in biogas derived from garbage into methane be demonstrated at EXPO 2025 Osaka, Kansai, Japan.
* Japan Association for the 2025 World Exposition

Demonstration of biogas methanation using kitchen waste

G-ko

It’s a great idea to use garbage. But “innovative” methanation technology is more incredible, isn’t it?

Ohnishi

Yes, it is called SOEC methanation. SOEC is the abbreviation for solid oxide electrolysis cell. The SOEC methanation system consists of an SOEC electrolyzer and a methane synthesizer. Take a look at this animated video.

O-ta & G-ko
Ohnishi

First, CO2 and steam (H2O), which is generated by heating water, are fed into the SOEC electrolyzer. When renewable electricity is applied, oxygen (O2) is removed by electrolysis. As a result, carbon monoxide (CO) and hydrogen (H2) are produced. When they are fed into the methane synthesizer, they are bonded over the catalyst that promotes reaction and then decomposed into methane (CH4) and water (H2O). Methane is used as the raw material of city gas, and water is recycled. Heat is generated during reaction in the methane synthesizer. This heat of reaction can be effectively used to heat water in the boiler.

O-ta

The mechanism is well designed! Applying energy to CO2 and water ... I know this resembles something else.

Ohnishi

Yes, it’s similar to photosynthesis of plants. CO2 and water are used as raw materials. When solar energy is added, glucose and carbohydrates, which are raw materials of fuel, and oxygen are produced. The final product is different, but the mechanism and the function to effectively use CO2 are similar.

Innovative methanation technology achieves high efficiency!

G-ko

So, what’s so innovative about SOEC?

Ohnishi

I was waiting for this question! In conventional methanation, heat generated when producing hydrogen or methane had to be discarded due to the nature of the reaction. Thus, the efficiency of converting renewable electricity into methane was low at 55 to 60%. In SOEC methanation, the SOEC electrolyzer can perform electrolysis with high efficiency, and the methane synthesizer can effectively use the generated heat. Thus, the conversion efficiency is expected to reach 85 to 90%.

O-ta

I get it! Methane can be produced more efficiently. This reduces the amount of electricity required! It’s innovative indeed.

Ohnishi

In fact, the Daigas Group has been working on R&D to further improve SOEC methanation.

G-ko

You are developing a more advanced technology.

Ohnishi

Yes, please look forward to the technological development of the Daigas Group in the future!

I hope you will enjoy the next time, too!

O-ta

Thank you, Dr. Ohnishi! It was an exciting story!

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