CDR describes techniques that remove CO₂ from the atmosphere and store it. If the CO₂ collected is to be effectively and permanently removed from circulation, permanent storage options, know as carbon sinks, need to be found. So far, neither economically viable nor ecologically sustainable techniques have been found, although these would be essential in order to meet the 1.5 °C target.
While CO₂ is also permanently stored via CO₂ sequestration (CCS), it is not filtered from the atmosphere but taken directly from the exhaust gases of power plants or industrial processes and stored on site. These techniques are, however, also view critically in terms of sustainability and profitability.
But research into these techniques continues to be pushed as the later the goal is achieved, zero net emission the higher the negative emissions will need to be. .
Sources: IPCC 2018 Special Report 15; Mark Jacobsen (Energy and Environmental Science 2, 2009)