Reduce our greenhouse gas emissions to limit global warming, but not only. In their report published Monday, April 4, scientists from the IPCC (Intergovernmental Panel on Climate Change) indicate that techniques for removing CO2 of the atmosphere were now “essential” to limit warming to 1.5°C or 2°C by 2100.
→ READ. IPCC report: how to change our lifestyles to lower our emissions
Even a drastic reduction in greenhouse gas emissions would leave some residual emissions “difficult to eliminate”. At the same time, the CO2 emitted accumulates permanently in the atmosphere. “We have emitted so much that we will now have to compensate”, explains Chris Bataille, associate researcher at IDDRI (Institute for Sustainable Development and International Relations) and co-author of the report. Until then, carbon absorption techniques were mainly perceived as decoys intended to delay climate mobilization.
Additional forest cover
What options are on the table? To stay below the 1.5°C mark, the scenarios studied by the IPCC plan to develop an additional forest cover of 322 million hectares by 2050, an area equivalent to that of India. In comparison, more than 420 million hectares of forest have been lost due to deforestation between 1990 and 2020. Other solutions offer great reduction potential, while being accessible at moderate cost: restoration of ecosystems that absorb CO2 (grasslands, mangroves), or even storing carbon directly in the soil, thanks to certain agricultural practices.
The Giec is also interested in longer-term technological solutions that make it possible to directly capture CO2 into the atmosphere and then inject it deep into the ground. “Unlike nature-based solutions, these have the advantage of being permanent”, explains Chris Bataille. Because the absorption effect of forests can be reversed in the event of fire, just as droughts can affect grasslands.
Stored in basements
In terms of technology, the most studied option in the scientific literature bears the name of “bioenergy with carbon capture and storage”. In summary, crops are planted; they absorb CO2 from the atmosphere through the natural process of photosynthesis; then are burned to provide energy. Instead of being released into the atmosphere, CO2 released is captured through a chemical process and then injected into the soil.
Another potential solution is to build technological facilities that directly capture CO2 present in the air, like a big vacuum cleaner. Like the option above, it is stored in basements. About ten units exist today throughout the world. The potential is uncertain: the largest unit, installed in Iceland, now takes a year to absorb what humanity emits in a few seconds.
This does not deter investors. Climeworks, the Swiss company that owns this facility, raised 650 million euros the day after the publication of the report. “It should be remembered that the IPCC does not recommend this or that solution, says Chris Bataille. It shows the solutions available to decision-makers and their implications. »
→ INVESTIGATION. Fight against global warming: the bet of CO2 capture
Thus the authors point out that these two technologies are potentially expensive and present risks. For bioenergy, the bulk is in the competition for land. In the case of CO capture2 directly in the air, one of the risks is to have the opposite effect: to emit more than it is absorbed, because of the energy necessary to carry out the operation.
Capturing industrial emissions
These solutions should not be confused with carbon capture and storage (CCS) technologies, which operate according to the same logic but capture emissions directly from an industrial or electricity production unit. “In 2050, these techniques will be needed to reduce residual emissions from cement and chemical production, which cannot be completely eliminated, unlike the steelmaking process”says Chris Bataille.
Nevertheless, the report specifies that the CCS does not make it possible to capture “all” carbon dioxide emissions from an industrial facility. And that it therefore comes after other measures (use of carbon-free energy, energy or materials efficiency). Primarily, therefore, it is the reduction of emissions that must be targeted. The report specifies “than a greater attenuation of demand” (i.e. our uses and consumptions) will involve “less dependency” to carbon removal.
A reduction in emissions necessary in parallel
Between 2010 and 2019, greenhouse gas emissions averaged 56 gigatonnes per year. They have increased by an average of 2.1% each year. In comparison, replanting forests and restoring ecosystems offers an annual reduction potential of around 3 gigatonnes per year, by 2030.
The IPCC thus estimates that in order to hope to keep global warming below 1.5°C or 2°CCO emissions2 will have to reach a maximum before 2025 and then decline rapidly. Warming below 2°C implies a reduction of at least a quarter by 2030.