What Are Carbon Removal Technologies - Are they effective?

Written by
February 22, 2024
5 min read

Global carbon emissions continue to rise, inflaming global temperatures and driving increasingly extreme weather conditions from wildfires to floods. One of the solutions becoming increasingly popular among both the government and businesses is carbon removal. As the name suggests this involves removing the carbon we have already placed in the atmosphere through things such as transportation which will produce approximately 7.3 billion metric tons of CO2 in 2020 or electricity production which accounts for 25% of all total carbon emissions.

Carbon removal is done via two broad methods:-

  1. Natural
  2. Artificial

Both are done with the one main goal in mind; keeping the global temperature rise below 1.5 degrees celsius above pre industrial levels.

Natural methods of carbon removal include;

  1. Tree planting
  2. Ocean sinks

Tree Planting

Forests are known as carbon sinks, which means they can remove CO2 from the atmosphere and store it, they can absorb up to a net of 7.6 billion metric tonnes of CO2 a year. The carbon sequestration is done via photosynthesis, the trees absorb the CO2 and store it in their leaves, trunks and roots. 48% of the carbon is also stored in the leaf litter and soil of the forest, this all contributes to making forests the largest component of atmospheric carbon that is absorbed by land. A study calculated that forests have the potential to absorb half of the excess carbon dioxide being produced by humans making them one of the most effective tools to reduce the CO2 overflow.

In order to enhance the carbon storing power of trees which have been destroyed for cattle or other CO2 producing industrial activities we can reforest or “afforest” (which means planting trees in places where there weren’t any before). There are many organizations, such as SKOOT which enable businesses to remove carbon via tree planting.

The amazon rainforest is one the world’s biggest carbon sinks

Ocean Sinks

Ocean sinks are a second example of a natural carbon sink, which are believed to currently absorb between 30 and 50% of all CO2 produced through the burning of fossil fuels.

Phytoplankton are the main reason the ocean is one of the biggest carbon sinks. These microscopic marine algae and bacteria play a huge role in the world’s carbon cycle - absorbing about as much carbon as all the plants and trees on land combined. Kelp forests also play a key role in ocean carbon sequestration, through photosynthesis kelp absorbs CO2 into its tissue. They grow incredibly fast, as much as half a meter per day meaning that they have the capacity to store as much as 200 million tons of CO2 per year. Other water systems too such as seagrass and algae are great at removing carbon, and humans can help preserve and restore these water ecosystems and organizations such as UNEP are already campaigning for changes.

A number of ocean based carbon removal concepts are being undertaken such as large scale kelp and seaweed farms. Alongside a hybrid of natural and technological removal, but they are all at the very early stages of development and need more research, funding and pilot testing to determine whether they are worth any investment. These ideas include running electric current through seawater to help extract CO2 or sprinkling phosphorus, nitrogen or iron on the ocean surface to speed photosynthesis to increase the oceans capacity to store dissolved bicarbonate. With time it is possible that ocean focused carbon removal ideas will be magnified.

Ocean forests absorb CO2

Whilst it would be wonderful to solely rely on natural methods of carbon removal there are not enough trees or water ecosystems to account for all of our emissions and we cannot restore destroyed forests and wetlands at a quick enough pace therefore we have to implement artificial methods.

The artificial or technological methods or carbon removal include;

  1. Direct air capture
  2. Carbon mineralization  

Direct Air Capture

Direct air capture is the process of chemically drawing the CO2 out of the atmosphere and then injecting it deep into underground geological formations. The carbon captured can also be combined with water before it is pumped into the ground, where it will then react with the stone to form stone, the carbon is sequestered within this stone for thousands of years. This technology can be used to create carbon negative consumer products, such as Sky Diamonds where the carbon is removed from the atmosphere, liquified and purified to create a carbon negative diamond. This technology removes CO2 from the atmosphere on a planetary scale and stores it in a permanent way. However, at the moment direct air capture is an expensive and energy intensive process with a 2018 study estimating that it would cost between $94 and $232 per ton of CO2.

Carbon mineralisation

Carbon Mineralisation is the process by which carbon dioxide becomes a solid mineral, such as a carbonate. Naturally it takes place very slowly over thousands and thousands of years, and takes place when certain rocks are exposed to CO2. The carbon becomes fixed in its new solid form and cannot escape back into the atmosphere, if this process can be sped up it could become a crucial carbon removal technology.

There are two main types of carbon mineralisation, the injection of carbon dioxide deep into rock formations which is what takes place in direct air capture or mineralising carbon with exposed rocks at the surface. The second method is probably the most useful, as much faster methods are being developed to do this include moving air (filled with CO2) through large mine tailings with exposed rocks or having mineralisation sites near industrial processes so that the carbon can be captured before it enters the atmosphere.  

 Carbon is captured in the rocks

These are just a few of the main methods that can be used to remove carbon from our atmosphere, they still require immense amounts of funding, testing and improving but more money is being pumped into these industries as the carbon issue worsens and it is hopeful that the technology will be perfected relatively soon. There are solutions to climate change and they should be harnessed.  

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Written by
February 22, 2024
5 min read