From renewable energy, fuel cells and electric vehicles to energy-efficient home appliances, people have found ways to reduce greenhouse gas emissions to mitigate climate change.
One technology expected to play a key role in curtailing emissions is carbon dioxide capture and storage, commonly known as CCS.
The process entails separating and collecting carbon dioxide, including exhaust emitted from thermal power plants, and injecting it into deep underground storage cavities so the carbon dioxide won’t be released into the atmosphere.
Hundreds of millions of tons of carbon dioxide could potentially be buried underground, but the technology is still in the experimental stage in Japan. At this point it’s both extremely costly and not an easy sell to a nervous, earthquake-wary public, preventing its widespread introduction.
Yet experts stress that CCS is essential if the world hopes to get serious about curbing greenhouse gas emissions.
“The costs are steep, but carbon dioxide emissions must be reduced,” said Japan CCS Co. President Shoichi Ishii.
Established in 2008, Tokyo-based Japan CCS is funded by regional utilities, oil firms, engineering companies and trading houses as part of an industrywide effort to promote underground carbon dioxide storage.
The CCS process starts with capturing carbon dioxide from exhaust gases, such as thermal power plant emissions, that include other substances like oxygen and nitrogen. There are several ways to separate carbon dioxide, but the most common one is to absorb the gases in an amine solution. Heating this solution renders the carbon dioxide into a highly pure state.
Once extracted, the pure carbon dioxide, now in a “supercritical” gas-liquid state, is transported to locations where it can be injected through pipes into the ground to a targeted geological layer more than 1,000 meters down.
The injected carbon dioxide is initially lighter than water so it floats to the top of the underground formations but stays there because it can’t permeate upper layers of densely packed rock and soil, just like deep underground oil deposits that are unable to seep to the surface even if they are floating atop groundwater and being pushed against the roofs of sunken cavities.
In a process that will take hundreds of years, the carbon dioxide dissolves into its underlying salt water or flows into tiny cracks in rocks to become mineralized.
At the government’s request, Japan CCS has been carrying out an experiment in Tomakomai, Hokkaido. Starting in 2016, it plans to inject 100,000 tons of carbon dioxide underground per year at the site over a three-year period, with the goal of achieving practical use of the technique by 2020.
The CCS approach is costly, offering little economic incentive for private-sector firms seeking to eke out a profit unless they are under government contract.
The Kyoto-based Research Institute of Innovative Technology for the Earth (RITE), which studies environmental issues, estimates it would cost about ¥7,300 to store 1 ton of carbon dioxide via the CCS method.
According to figures from the Environment Ministry, Japan emitted about 1.3 billion tons of carbon dioxide in fiscal 2012. It would thus cost about ¥950 billion to store just 10 percent of that level of annual output, under RITE’s estimate.
Among the emitters that could potentially have the financial heft to utilize carbon dioxide capture and storage are large-scale facilities like thermal plants and factories.
RITE believes Japan has the capacity to store 150 billion tons of carbon dioxide underground.
Advocates say that the world has seen the dramatic, and harmful, impact of global warming in recent years and thus should not consider the pursuit of the CCS process an extra financial burden.
“Nobody thinks of (their municipal) garbage collection service as (an unnecessary) expense. It is funded by tax money. People welcome the service because they don’t want garbage piling up at their home,” said Kozo Sato, a professor at the University of Tokyo and an expert on the CCS approach.
The world won’t get serious about reducing carbon dioxide emissions unless people regard the gas as household garbage that has to be hauled away, Sato said.
If humankind chooses to take no effective steps to reduce carbon dioxide emissions and accepts global warming as inevitable, CCS would be unnecessary and the world should focus on coming up with defenses against the consequences of climate change, he said.
But at least for now, the world is aiming to cut greenhouse gas emissions.
The International Energy Agency has estimated that CCS is expected to account for 19 percent of global carbon dioxide reductions in 2050.
Sato argues that if the world intends to cut emissions, CCS is the path to follow.
The technology has been in practical use overseas for years, so it’s a matter of how serious people get about promoting CCS, he said.
Also, the public must be on board, experts say, noting that people living near planned storage sites must be convinced they are living in a safe environment.
People in Tomakomai were initially worried that the CCS experiment would be dangerous, Ishii said.
“Many people are unfamiliar with CCS and thus conjure up notions of radioactivity or carbon monoxide,” he said.
But Japan CCS eventually gained the community’s acceptance and relations are now good.
Another concern is that injecting carbon dioxide underground could cause earthquakes.
Ziqiu Xue, chief researcher at RITE, said it is true that injecting carbon dioxide underground could cause small-scale shaking episodes, but “they are very small. Humans feel (an) earthquake when it is about magnitude 3, but those (caused by CCS) are smaller than magnitude 1 (and are not felt by humans),” he said.
There have been no reported large-scale earthquakes induced by CCS projects anywhere in the world, he said.
Shaking occurs when the carbon dioxide is injected into the targeted layer and bonds that hold grains of sand together are broken due to the change in pressure, Xue said.
But the energy created from a carbon dioxide injection is small amount compared with the massive amount that would be required to trigger a large-scale temblor or other tectonic upheaval, he said.
Some people may also worry about the consequences should a massive amount of stored carbon dioxide somehow escape to the surface, because such a high concentration could cause carbon dioxide poisoning and have other harmful effects.
To prevent this, Ishii said it is critical to choose a site and geological layer that can definitely trap carbon dioxide underground, and strict monitoring will be essential so that operators can quickly take measures if they detect leaks.
Sato of the University of Tokyo meanwhile said storing carbon dioxide underground is not so extraordinary.
“Natural gas found underground contains carbon dioxide. This is common,” he said, adding that the carbon dioxide found in the Natuna gas field in the South China Sea is about 70 percent pure.
This section features new technologies that are still under research and development but are expected to hit the market in coming years.