CO2 compression facility under demonstration test in Mikasa City, Hokkaido
"I want to revitalize the town that was once a shining coal mine." Kensaku Saijo, Mayor of Mikasa City, Hokkaido, said: A demonstration experiment of the "Mikasa Model" technology, which extracts hydrogen and gas from underground coal and buries the generated carbon dioxide (CO2) underground, began in August.
The carbon dioxide produced during the gas production process is pumped underground. It is absorbed by the mine water and unmined coal that flows through the mining site and is confined underground. Furthermore, the slime-like slurry material is sent underground and reacted with CO2 to fix it.
The former Hokutan Horonai Coal Mine, which is the stage of the demonstration experiment, is the first modern coal mine in Hokkaido and the place where the railway was born in Hokkaido. Mining began in 1879, and a government-operated railway was built connecting present-day Temiya, Otaru City with Horonai, Mikasa City. The mine was closed in 1989 due to the spread of oil after the war.
There is a coal mining site about 400 meters underground. The mountain-shaped strata can prevent CO2 from being released to the ground, and there are roads to access the test site. In the demonstration experiment, we succeeded in injecting 40 tons of slurry and "microbubble water", which is 30 tons of water dissolved with CO2.
Mayor Saijo called out to specially appointed professor Kenichi Itakura of Muroran Institute of Technology, and joint research began in 2011. Although there were various problems such as gas leakage to the ground surface, groundwater contamination, and dealing with the complex geological structure of coal in Hokkaido, they were able to establish a gasification technology that is safe and has a low environmental impact.
First, oxygen is fed into the coal seam and burned to produce combustible gases including hydrogen and carbon monoxide. By separating and refining the hydrogen contained in the gas, 89 kilograms per ton of coal is extracted.
According to Mikasa City, coal reserves in the city are estimated to be about 750 million tons. There are many undeveloped coal mines, and the potential for creating an energy industry through gasification, hydrogen production, and CO2 storage is high.
In 2009, it was adopted as a research project by the New Energy and Industrial Technology Development Organization (NEDO). We investigate the possibility of using hydrogen refined by underground gasification of coal and combustion of woody biomass. The company aims to put the technology into practical use in fiscal 2030 at the earliest after conducting demonstration tests.
Companies have high expectations for the project to revive the coal mining town. In the corporate version of the hometown tax donation, 100 million yen was donated by Z Holdings affiliate Yahoo, and a total of 13.6 million yen was donated by six companies, including Tokyo Gas Engineering Solutions (Tokyo, Minato), a subsidiary of Tokyo Gas.
Mikasa City, known as a coal mining town, peaked at 63,360 in 1960 and has since declined in population. By 2022, the number will fall below 8,000. A decarbonization strategy is one of the solutions. In 2013, the Mikasa City Regional New Energy Vision was formulated, and in 2021, it declared a zero-carbon city. In addition to the underground gasification of coal, the effective utilization of forests as biomass resources will be hastened.
Mikasa City prospered as a coal mining town (Courtesy of Mikasa City Museum)
The city of Yubari, also a coal mining town, has been conducting demonstration experiments since 2017 on the use of coalbed methane gas contained in coalbeds, but has given up on commercialization due to unprofitability.
According to the NPO Underground Resource Innovation Network (Sapporo City), unused coal in Hokkaido is about 14.8 billion tons. The "Mikasa Model" has the potential to bring about evolution in mining cities around the world.
