Carbon removal is going to be super critical in making progress on The Climate Crisis. It's an important tool in limiting climate change, even if it's not a silver bullet without large emissions reductions.
But WTAF is it?
At the highest level, carbon dioxide removal (CDR for short) is anything that takes carbon dioxide and equivalent* emissions out of the atmosphere and stores them somewhere for a period of time.
Drawing down and locking these emissions away is called sequestration*. The amount of time they'll be sequested is called permanance*, and whether this is extra to normal cycles that would happen anyway is called additionality*. Another consideration for the solution is any co-benefits* it creates, for example if a nature based carbon removal project also rejuvenates a habitat or ecosystem.
There are sort-of three groups of carbon removal solutions. Those that are found in the wider natural world that we can utilise and the others are technologies that we invent and implement, either to increase the effectiveness of nature or new techniques.
Each solution varies in terms of the amount of carbon it can sequester, how permanent it is (as well as how verifiable and additonal the sequestration is).
Before we jump in it's important to mention that carbon removal is not a silver bullet. While there's lots we know how to do that is effective in removing emissions, at present we simply emit too much. As we reduce emissions it will increase the effectiveness and importance of carbon removal solutions to limit climate change. Carbon removal is an important tool when combined with large scale decarbonization*.
Righty-ho, let's go!
Nature Based Carbon Removal
Yep, these are any processes that happen out in the big wide, beautiful world that naturally suck carbon dioxide out of the atmosphere and store it in some way for a period of time.
For example, good old trees use carbon dioxide to grow and lock it away while the tree is alive. That's why you'll often see people talking about planting a boat-load of more trees. It's an important tool, and is comparatively cheap, so it's absolutely a key thing we should do more of, and at a huge scale. Both reforestation* as well as afforestation*.
One challenge is it's not that permanent - the carbon is only locked up while the tree is alive and is released when it dies. In addition, depending on the species it can take around a decade for a new tree to start removing more carbon that it emits. In addition, if the tree burns down or doesn't make it to the age when it absorbs more, then effectively no emissions have been removed by planting it.
Also no, we can't simply plant enough trees to offset the high level of present global annual emissions. There isn't enough land on the planet to plant enough trees. We pump that much out at present.
Old growth forests - those that have been around for hundreds if not thousands are years are equally important to protect from deforestation, as they are carbon sinks* (as well as incredible ecosystems).
Another example is storing emissions in the ocean by growing more plants like kelp or mangroves. At present the oceans have naturally sequested about half of humans carbon emissions, keeping them out of the atmosphere so they can't add to continued global warming (though they will become less effective if we keep pumping out so much every year).
Technology Based Carbon Removal
There's now an emerging array of new technologies designed specifically to remove or capture emissions from the atmosphere (or just before they would have been released).
For example, Direct Air Capture* (DAC) which separates carbon dioxide in the air using fans and a chemical process to then inject the carbon into rocks deep underground, effectively storing it forever.
Or by collecting and injecting organic waste - which would have otherwise decomposed and released emissions - deep underground where it can't escape into the atmosphere.
These technologies are early and not anywhere close to the scale we need to make a dent in the 50 billion tonnes of emissions humans pump out each year. They need investment and time to mature.
As we massively reduce our annual emissions over the coming years (hopefully), and increase the scale of these removal technologies they may become helpful tools in limiting climate change.
This said, it'll likely be much cheaper and quicker to reduce a load of emissions, while we invest in developing and scaling this new tech to use for the emissions we find hard to stop pumping out.
Tech-enabled Nature Based Carbon Removal
This one is a bit of a mixed bucket. Most folks lump everything into the two groups - nature based and technological - though we want to make a slight distinction here. There's a gray area where humans are enhancing nature based carbon removal to increase the amount of emissions that are sequested.
For example, this might include humans using technology to support increased draw down of carbon into rocks and soil, locking it away through a natural process, with the support of human intervention to speed it up from its normal pace and scale.
Want to find out more?
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Climate Buzzword Dictionary
Carbon dioxide and equivalents - bundle of main greenhouse gases - carbon dioxide, methane & nitrous oxide. Abrev. CO2e
Emissions - the creation and release of Greenhouse gases into the atmosphere
Greenhouse gases - abbreviated to GHG. 98% made up of Carbon Dioxide, Methane or Nitrous Oxide. Gases that trap heat in the atmosphere
Sequestration - when CO2e is taken out of the air and locked away in a carbon sink
Permanance - when talking about carbon removal it means the amount of time emissions are locked away and out of the atmosphere. Depending on the solution, it varies between a decade or more, to thousands of years to potentially forever
Additionality - when talking about carbon removal it's how much of that solution is extra to what would have happened normally, without that solution being used
Co-benefits - when talking about carbon removal, for example, it could be if a nature based carbon removal project also rejuvenates a habitat or ecosystem
Decarbonization - disconnect all the things humanity does from creating and releasing carbon emissions. The process to stop emitting Carbon Dioxide into the atmosphere
Direct Air Capture - technology to take carbon out of the air
Reforestation - planting trees in an area that has been deforested that had trees there before
Afforestation - planting trees in an area that hasn't had trees there before
Carbon Sink - places in nature that absorb carbon and lock it away for the long term, so it's not in the atmosphere, for example oceans and forests