Carbon Capture & Sequestration is an approach of climate change mitigation and adaptation which involves the capture of released CO2 and injection deep underground. Currently, when fossil fuels are burnt, the carbon dioxide is released into the atmospheres where it can remain for 300-1000 years. Therefore, CCS provides an opportunity for large scale mitigation. This takes place in 3 main stages:
1. Carbon dioxide is separated from power station emissions
There are 3 types of separation processes: post-combustion, pre-combustion and oxy-fuel combustion.
2. The gas is compressed and transported by pipeline to storage
After it is captured, the CO2 needs to be transported to the storage stations. Nowadays, pipelines are the most common method of transportation. These pipelines are already built into the U.S infrastructure and are placed everywhere from underground to underwater. The pipelines can transport CO2 as solid, liquid or gas with the most cost-effective state being gaseous. The CO2 needs to be pure, free of hydrogen sulphide and dry, otherwise, it will corrode the pipelines and make them more prone to leaks which are especially hard to spot as CO2 is odourless and colourless. The CO2 is compressed to high pressure and is then pushed through the pipes to its final destination.
3. CO2 is injected into sources underground or underwater for storage
After the CO2 is transported, it then has to be stored. Contrary to popular belief, the carbon dioxide is not stored in huge tanks or landfills, rather in 2 places, underground and underwater. Experts have predicted that our planet can store up to 10 trillion tonnes of carbon dioxide, allowing for 100 years of storage of all human-created emissions.
Underground storage is done by injecting the CO2 into porous rocks below the earth's surface. These natural reservoirs have rocks above which form a seal, keeping the gas safely contained underground. Other forms of underground storage involve storing CO2 in volcanic rock, which converts the basalt into limestone. In addition to underground storage, undersea storage is also a viable option but must be released at depths below 3500 meters where it will compress into material that will stay on the seafloor. However, ocean storage is still a raw option and is due for further testing due to possible marine risks and re-release into the atmosphere.
So where are we now?
Carbon Capture & Sequestration could make a big difference to the size of anthropogenic (man-made) carbon store with an estimation to reduce coal-fired power stations by up to 90% and provide up to half of the world's carbon mitigation until 2100. So then the question arises, why are we not doing more of it?
The stumbling block with carbon sequestration is the overwhelming price point, as seen by the cancellation of pilot projects in the UK due to costs rising over 1 billion USD. This is due to the high complexity of the technology used in the process, which is still being developed and researched. Right now, we cannot expect this to be an immediate fix; it is only being tested in a select few power stations and still needs a lot of research and development, so the chances of it improving our emissions right now are slim. Questions also arise about the effectiveness of it: how certain are we that the CO2 will stay underground and won't rise back to the surface? Furthermore, the process of trapping and liquefying the carbon dioxide from power plant emissions requires significantly more amounts of electrical power, requiring up to 40% more coal, therefore leading to a rise in energy use in the short term.
Carbon Capture and Sequestration is far from an immediate solution with many kinks still being worked out, but the potential it has is immense and cannot be ignored.
Comments