Get serious about removing carbon dioxide

Perhaps the easiest way to remove carbon dioxide from the atmosphere is to manage forests so that they absorb more carbon. But there are other ways, like capturing carbon right out of the air and then storing it deep underground or in the form of mineral deposits. Perhaps little known is that climate change models that describe potential ways to mitigate the risks of climate change usually assume that carbon dioxide removal will increase dramatically and that this will be an important part of any final decision. The Smith School of Entrepreneurship and the Environment at the University of Oxford provides an overview of science, politics and public opinion in “Carbon Removal Status Report2023. Lead Contributors: Stephen M. Smith, Oliver Geden, Jan S. Minks, and Gregory F. Nemeth.

Here is a chart showing the different carbon dioxide removal approaches in the first column and the way they work in the second column. The third column, labeled “TRL”, stands for “Technological Readiness Level”, ranging from theoretically possible (1) to operational readiness (9). The last two columns show the approximate cost of carbon removal if the technology is developed on a large scale. and the potential amount of carbon it can remove (measured in gigatonnes of CO2).

Broadly speaking, they can be divided into three categories of how carbon is stored.

Biological storage (on land and in the oceans). While annual plants do not store carbon for long periods of time, trees can store it for decades, centuries or more. Soils and wetlands are another store of carbon derived from compounds secreted by roots and dead plants. In the oceans, aquatic biomass can sink to the ocean floor and become marine sediment. Carbon can be stored in these ecosystems for a long time, especially if carefully managed to reduce
Product storage. Many carbon based products do not provide long shelf life. However, building materials and biochar (a carbon-rich material made by heating biomass in an oxygen-limited environment) can store carbon for decades or more. These carbon-based products can be obtained by converting harvested biomass (in the case of biochar and wood in construction), from concentrated CO2 streams, or even from ambient air CO2 (in the case of aggregates).
geochemical repository. Concentrated CO2 can be stored in geological formations using depleted oil and gas fields or saline aquifers, or reactive minerals such as basalt. Geochemical capture leads directly to long-term storage of CO2 as carbonate minerals or bicarbonates in the ocean.

The report emphasizes that it is extremely unlikely that removing carbon dioxide alone can solve problems with atmospheric carbon levels. The idea is that it can complement other efforts. After all, all fossil fuel reduction approaches only reduce the rate at which carbon is added to the atmosphere, while the effect of removing carbon dioxide is actually to lower pre-existing levels of carbon to lower levels than would otherwise be the case. case. achieve. The report claims:

Virtually all scenarios that limit warming to 1.5°C or 2°C require “new” CDRs such as BECCS, biochar, DACCS and enhanced rock weathering. However, only a small fraction (0.002 GtCO2 per year) of the current CDR results from new CDR methods. Closing the CDR gap requires a rapid rise in new CDRs. On average across scenarios, new CDRs increase 30-fold by 2030 (up to about 540 in some scenarios) and 1300-fold (up to about 4900 in some scenarios) by mid-century. However, no country has yet committed to scaling up new CDRs by 2030 as part of its national contribution, and few countries have so far published proposals to scale up new CDRs by 2050.

Indeed, when looking at the amount of carbon dioxide removal, more than 99% is from reforestation, and about 0.1% is from the newer forms of carbon dioxide removal listed in the table.

Another key point is that if even some of these technologies are to work at scale, a lot of innovation and learning by doing will be required over a long period of time. Unless countries start a wide range of carbon dioxide removal pilot projects soon, in 2-3 decades there will not be the necessary knowledge base for large-scale use of carbon dioxide removal. And, again, all major climate change mitigation scenarios involve the assumption that this technology will become mature and workable. Without technologies to remove carbon dioxide, the already very difficult task of combating rising levels of atmospheric carbon becomes much more difficult.