To avoid the worst predicted effects of climate change, climate experts say we need to not only reduce our greenhouse gas emissions, but also remove and sequester carbon that’s already been released in the atmosphere.

  There are more or less natural ways to do this — we can plant more trees, tweak farm soil to absorb more carbon, or spread green sand on beaches. Or we can pull carbon from the atmosphere using huge machines, known as direct air capture (DAC) technologies.

Direct air Capture

  DAC systems typically use fans to pull in air from the atmosphere. The carbon in it then reacts with and binds to a chemical in the system. Heat can then be applied to the chemical to release the carbon for storage or reuse, and the rest of the material is returned to capture more CO2.

  Unlike forests, farms, or beaches, CO2 removal facilities do not have any geographical constraints — the amount of carbon in the....