Carbon capture and storage (CCS) is a suite of technologies that can help us tackle climate change. It involves capturing the climate-warming CO2 released when we burn fossil fuels for energy, transporting it, and permanently storing it deep underground in geological formations.
Once it has been captured, the CO2 is pumped underground using pipelines or specially-adapted ships. Several large CCS projects around the world are already in operation.
Why CCS?
Carbon capture and storage is a crucial technology for mitigating climate change. It can be used to reduce CO2 emissions from industrial processes and power generation and store them underground in secure geological formations.
CCS technologies can be combined with renewable energy sources to provide “negative emissions” technologies – that remove more carbon dioxide from the air than they emit. These include bioenergy with CCS (BECCS), where plants like forests and grasses remove carbon dioxide from the atmosphere through photosynthesis, and waste-to-energy and direct air capture technologies.
It can also be used alongside fossil fuels, to reduce the environmental impacts of burning them – for example reducing upstream emissions associated with mining and transporting coal and gas, as well as fugitive methane emissions from pipelines and power stations. Capture and storage is already in use in a number of power plants and other industrial facilities, and the need for this technology to mitigate climate change is growing.
Capturing CO2
A suite of technologies known as carbon capture and storage (or CCUS for short) helps us to reduce CO2 emissions from fossil fuel power plants. These processes separate the CO2 from exhaust gases and then store it underground, permanently.
CCS can be used at a range of emission sources, from power plants and factories to oil refineries and fertiliser plants. Various different techniques can be used to capture the CO2, including post-combustion capture, where a solvent is added to the fuel; oxygen fuel combustion, where fossil fuels are burned with pure oxygen; and direct air capture, where huge fans funnel air into plants that remove the CO2.
The captured CO2 gas is then compressed into a liquid-like state and transported by pipeline to a geological site for storage. Most sites are old oil or natural gas fields or deep saline formations, which have been used to store oil, natural gas and salty water for millions of years.
Transportation
Most CCS strategies involve transporting the climate-warming CO2 from coal- and gas-fired power plants to geologic formations for permanent storage. This can be a dangerous and complicated process – and it requires lots of energy.
In addition to lowering carbon emissions, the CO2 stored underground could be used to produce more electricity. Specifically, the CO2 can be pressurized into a supercritical fluid that transfers heat more efficiently and takes less energy to compress than steam. This fluid could be used to drive power generation turbines, generating more clean energy.
It’s also possible that captured CO2 could be transported by ship. Currently, this is only an experimental technology, but the International Maritime Organization (IMO) has begun to develop a regulatory framework for onboard carbon capture and storage systems.
Storage
Carbon capture and storage – or CCS – is one way to reduce emissions from power plants and industrial processes. It involves capturing CO2, transporting it, and storing it permanently in geological formations.
Carbon dioxide has to be stored in order to prevent it from being released back into the atmosphere, where it contributes to climate change. Most CCS strategies involve storing the carbon dioxide deep underground.
This involves pumping the captured CO2 into pre-existing oil or gas reservoirs, unmineable coal seams or saline aquifers. We work to develop tools that can help us better assess the environmental fitness of these geologic sites and ensure they are safe for storage.
We also support the development of onboard CCS systems to allow ships to remove CO2 directly from their exhaust. This would be a significant step toward a low-carbon future. Ultimately, though, this kind of technology should only be used as an interim solution to reduce greenhouse gases while we transition to renewable energy sources.