Carbon capture and storage (CCS, also sometimes seen as carbon capture and sequestration) is the collection of carbon dioxide (CO2) for storage as a gas or as a different form of carbon after separating out the oxygen.
Among greenhouse gasses, CO2 is the most significant contributor to the greenhouse effect, due not only to its abundance in the environment but also to its interaction with methane. CCS is promoted as a means of reducing the accumulation of CO2 in the atmosphere and mitigating its effect on global warming.
Carbon may be captured at the source of a high CO2 output such as smoke stacks in various industries and carbon-based power plants. Carbon can also be removed from ambient air anywhere in the environment with direct air capture (DAC) technologies.
At a source point of carbon output, such as a smoke stack, the associated thermal energy (heat) may be used in the capture process or diverted for use as an alternative heat source. Most often with this method of capture, carbon is merely stored where it is protected from release into the air, usually underground or under the sea. However, leakage is a potential concern in most methods of carbon sequestration.
Captured CO2 or extracted carbon can also be used in various ways, in which case the process involved is known as carbon capture and reuse (CCR) or carbon capture and utilization (CCU). The effectiveness of that approach depends on the use in question, because in some cases -- such as agricultural use -- the CO2 is eventually released into the environment in any case.
Opponents of the technologies maintain that the energy sector's focus should be on renewable resources rather than fossil fuels. Their fear is that carbon capture, whether for storage or reuse, might legitimize continued reliance on fossil fuels and result in further damage to the environment.