Carbon 'capture' climate tech is booming, and confusing

economictimes.indiatimes.com:

carbon dioxide emissions — 41 billion tonnes in 2022 — has thrust once-marginal options for capping or reducing CO2 in the atmosphere to centre stage in climate policy and investment. Carbon capture and storage (CCS) and direct air capture (DAC) are both complex industrial processes that isolate CO2 but these newly booming technologies are fundamentally different and often conflated.

Here's a primer on what they are and how they differ.What is carbon capture? CCS syphons off CO2 from the exhaust, or flue gas, of fossil fuel-fired power plants as well as heavy industry. The exhaust from a coal-fired power plant is about 12 percent CO2, while in steel and cement production it is typically double that.

Unlike CCS, which by itself only prevents additional carbon dioxide from entering the atmosphere, DAC extracts CO2 molecules already there. Crucially, this makes DAC a «negative emissions» technology.

It can therefore generate credits for companies seeking to offset their greenhouse gas output — but only if the captured CO2 is permanently stored underground, such as in depleted oil and gas reservoirs or in saline aquifers. The concentration of carbon dioxide in ambient air is only 420 parts per million (about 0.04 percent), so corralling CO2 using DAC is far more energy intensive.

Once isolated using either CCS or DAC, CO2 can be used to make products such as building materials or «green» aviation fuel, though some of that CO2 will seep back into the air. «If the CO2 is utilised, then it is not removal,» said Oliver Geden, a senior fellow at the German Institute for International Security Affairs.State of play The fossil fuel industry has been using CCS since the 1970s but not to prevent CO2 from leaching into the atmosphere.