carbon capture and storageCCS) involves stripping carbon dioxide from emissions, compressing it into a “supercritical fluid,” and then pumping it deep underground into porous, rocky reservoirs, where it would, in theory, remain buried. Potential carbon storage sites include depleted oil and gas fields and highly saline aquifers.
Although CCS technology has been around for decades, it has not been widely adopted. This is partly due to the high cost of building insulation plants, but it is also due to lingering questions about how well the process actually works. Over long periods, a small amount of carbon dioxide leakage can become large, and where storage sites are below the sea floor, the leak can have profound effects on marine life.
Merely spotting leaks is difficult and expensive. Monitoring of CO2 capture and storage usually relies on heavy seismic equipment installed on trucks or ships. The device sends strong vibrations in the earth’s crust and analyzes the sound waves that are reflected.
Because of the high cost, these systems can only be used for limited periods of time. “In the traditional system, monitoring is intermittent,” he said. Takeshi TsujiProfessor of Engineering, University of Tokyo. “It’s hard to get seismic data continuously.”
However, Japan’s ambition to explore the solar system may have led to a breakthrough to carbon storage here on Earth. A team from the University of Tokyo and Kyushu University, led by Tsuji, has developed a lightweight system, the Portable Active Seismic Source (PASS), designed to be carried aboard Mars and a lunar probe that may also detect carbon leaks at isolation sites. The scientists published their results in seismic search messages Last month.
The PASS, which is only 10 centimeters long, creates vibrations by means of a rotating wheel mounted with an off-center weight. Due to the device’s small size, the vibrations it produces are relatively weak, but the team uses software to “stack” hundreds of signals, greatly amplifying the transmission.
Stacked seismic signals are able to penetrate more than 800 meters underground. CCS wells must be this deep to maintain CO2 pressure. In theory, arrays of PASS boxes could be deployed over these sites, allowing geologists to monitor carbon leaks. “This system is very cheap, and it is constantly generating, so we will be able to monitor constantly,” Tsuji said.
PASS funds can help Japan achieve its ambitious goal of being carbon neutral by 2050. As part of this goal, the country plans to isolate up to 240 million tons of carbon dioxide annually in hundreds of wells, mostly offshore.
Toro Sano A geophysicist at JX Nippon Oil & Gas Exploration, a Japanese company that has plans to integrate CCS into its operations. He said PASS’s small size and low cost make it ideal for long-term monitoring of confinement sites. He said, “We have to monitor not only the injection period, but also after the site is closed – maybe for 10, 20 or even 50 years.” He said ongoing monitoring is also important for managing public perception about the safety of carbon sequestration sites.
Although some critics accuse Japan of pursuing carbon storage as a way to continue extracting and burning fossil fuels while still achieving their net zero carbon goals, the United Nations’ Intergovernmental Panel on Climate Change considers carbon capture and storage essential to curbing global warming. According to the most recent Climate Change Reportthere are more than enough potential carbon storage sites on Earth to contain all the carbon dioxide needed to limit warming to 1.5°C, but the technology’s deployment is currently well below what is needed to reach that goal.
– Bill Morris, science writer