Carbon Dioxide, the Main Culprit of Global Warming, can be Absorbed Using Sewage | FRIDAY DIGITAL

Carbon Dioxide, the Main Culprit of Global Warming, can be Absorbed Using Sewage

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Using “electricity-producing bacteria” in sewage to absorb carbon dioxide.

In order to curb global warming, various technologies are being developed to achieve carbon neutrality by the year 2050. One such technology is the use of sewage to capture and immobilize carbon dioxide gas.

“Demonstration tests have already been completed, and we are moving toward practical application,” says Professor Daisuke Sano of Tohoku University.

The reduction of greenhouse gas emissions is an urgent issue. Carbon dioxide accounts for about 90% of Japan’s total emissions.

According to Professor Sano’s profile, his specialty is water and sewage engineering. It says that during the corona epidemic, he once measured corona viruses from sewage and predicted infection in that area. His research seems to have nothing to do with carbon dioxide.

“The sewage industry has been conducting research on the recovery of methane generated at sewage treatment plants and its use in power generation.”


The microorganisms are ‘electricity-producing bacteria’. In the absence of oxygen, they are known to breathe through electrodes, passing electricity to electrodes, and if the electrons are collected properly, an electricity generating device can be created.

Professor Sano’s focus was on the fact that alkaline water is produced when the electrons produced by the bacteria are collected at the electrodes. Carbon dioxide is easily soluble in alkaline solutions. He thought that carbon dioxide could be absorbed with alkaline water.

“The chemical reaction that occurs produces bicarbonate ions, which can be collected and reused in water purification.”

Generally, an alkaline solution must be prepared to absorb carbon dioxide, and its disposal is also costly. With this device, there is no need to purchase alkaline solution and no need to dispose of it. In addition, the water becomes clean, making it a device that kills three or four birds with one stone.

Carbon Dioxide Absorption distribution in households in the future, however it costs 30,000 yen.

Many companies are currently conducting research on carbon dioxide absorption, but the equipment is huge and costly. Is Professor Sano’s device also huge?

“No, it is about 15 x 15 x 10 cm.”

How much does one unit cost?

“About 30,000 yen.”

Thirty thousand yen!

The device itself is extremely simple, requiring only electrodes to be inserted into the sludge containing the electro-producing bacteria. When installed at a sewage treatment plant, about 10 units need to be connected together, but that still costs 300,000 yen. The device cannot eliminate the carbon dioxide emitted from sewage treatment plants, but it can recover about 10% of the carbon dioxide emitted per person per day from sewage treatment.


Currently, there are 2,200 sewage treatment plants in Japan. Even if the recovery rate is only 10%, the amount of carbon dioxide that would be recovered if all sewage treatment plants were equipped with the system would be nothing to scoff at. In the future, it is possible to further improve the performance and increase the recovery rate.

Japan’s greenhouse gas emissions in fiscal 2020 totaled 1.044 billion tons. The industrial sector, such as factories, emits the largest amount of carbon dioxide, followed by the transportation sector, such as automobiles, commerce and services, and business establishments, with the residential sector coming in fourth. While the industrial and transportation sectors have been decreasing their emissions year by year, the household sector has been on an upward trend since 2019, accounting for about 16% of total emissions.

Japan has won the “Fossil Prize,” an annual award given to countries that are reluctant to take action against global warming. Prime Minister Kishida has listed “global warming countermeasures” as one of the key policies of his new capitalism.

Reducing carbon dioxide emissions from households is also an important measure to combat global warming.

Professor Sano’s device is small, since households also produce wastewater, this device could be used in homes.

“At sewage treatment plants, the water is flowing, so the generated bicarbonate ions can be naturally discharged, but for use at home, the problem is how to collect the bicarbonate ions.”


“But someday.” says Professor Sano.

“Large-scale devices are needed for places that emit large amounts of carbon dioxide, such as power plants and factories, but I think this device will be useful in homes and other places. In the future, we would like to make the device usable in various places, such as apartment buildings and shopping malls, so that it can absorb carbon dioxide widely and shallowly.”

Once the household version is completed, the government should definitely distribute it to each household.  

Daisuke Sano, Professor, Graduate School of Engineering, Tohoku University. In addition to research on atmospheric carbon dioxide capture technology using microbial fuel cells, he has developed technology for predicting sewer pipe deterioration using microorganisms in sewage, assessed the risk of waterborne diseases caused by pathogens such as norovirus, evaluated the potential for drug resistance gene transmission in the water environment, evaluated the potential for abnormal algal blooms in water sources, and conducted research on the early detection of infectious diseases. and the development of technology to utilize sewage water quality for the early detection of infectious disease outbreaks.

A researcher in Sano’s lab assembling a carbon dioxide capture device, which is truly compact at 15 x 15 x 10 cm. When multiple units are installed at a sewage treatment plant, 10% of the carbon dioxide per person per day emitted by sewage treatment is recovered (PHOTO: courtesy of Professor Daisuke Sano).
Although the existence of the electricity-producing bacteria was known among experts, the idea that it could be used for carbon dioxide capture came to Professor Sano because he always tries to ‘have a different point of view from others.’ Under his teachings, students continue to conduct experiments in his laboratory (PHOTO: Courtesy of Professor Daisuke Sano).
  • Interview and text by Izumi Nakagawa

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