Carbon dioxide removal, and why it matters

WHAT IS CARBON DIOXIDE REMOVAL (CDR)

* CDR involves capturing carbon dioxide (C02) from the atmosphere and storing it long-term on land, in the ocean, in geological formations or in products such as timber

* The idea is to keep captured CO2 locked up for decades to millennia, buying the world more time to cut emissions that are warming the planet

* It's not a silver bullet for climate change, but is seen as a weapon that can be deployed in the transition towards net zero emissions

* But few countries have explicit strategies to scale up CDR

HOW CDR CAN AID THE CLIMATE CHANGE FIGHT:

* CDR can battle climate change in three ways

* The obvious way is by reducing net emissions - literally taking a gas that traps heat out of the atmosphere and locking it up securely in some other form

* Secondly, the world will buy more time to transition to net zero if CDR is done at scale

* Thirdly, if the world overshoots the Paris climate pact's ambition to limit warming to well below 2C, it will help reduce CO2 back to safe levels

EXISTING AND EMERGING METHODS:

* There are lots of different ways to suck CO2 out of the atmosphere, some proven, some new and uncertain

* The most widespread method is planting trees, which take up CO2 through photosynthesis and convert the carbon to wood as they grow

* Another is soil carbon storage, or carbon farming. It involves managing land, particularly farmland, in ways that help soil absorb and hold more carbon

* One way farmers can encourage soil carbon storage is by planting crops that don't die off every year and grow deep roots, or moving to no-till farming to help soil hold onto carbon

* There are many emerging CDR methods, including burning organic agricultural and forestry wastes to make a charcoal-like substance called biochar

* Biochar securely locks up the carbon in that waste and when used on farms can help soil retain water and nutrients, boosting crop production

* Another emerging method is direct air capture - emerging technologies that extract CO2 directly from the atmosphere, allowing it to be permanently stored in deep geological formations, for example