Reducing our greenhouse gas emissions to limit global warming, but not alone. In their report published on Monday 4 April, the scientists at 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 we can change our lifestyle to reduce our emissions
Even a drastic reduction in greenhouse gas emissions would produce some residual emissions “hard to eliminate”† At the same time, the CO2 emitted permanently accumulates in the atmosphere. “We have emitted so much that we 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 had mainly been seen as decoys intended to slow down climate mobilization.
Extra forest cover
What options are on the table? To stay below 1.5°C, the scenarios studied by the IPCC plan to develop an additional 322 million hectares of forest by 2050, an area equivalent to that of India. By comparison, more than 420 million hectares of forest were lost to deforestation between 1990 and 2020. Other solutions offer great reduction potential and are accessible at a moderate price: restoring ecosystems that absorb CO2 (grasslands, mangroves), or even by storing carbon directly in the soil, thanks to certain agricultural practices.
De Giec is also interested in longer-term technological solutions that allow CO . to catch immediately2 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 during fire, just as droughts can affect grasslands.
Stored in cellars
In terms of technology, the most studied option in the scientific literature bears the name: “bioenergy with carbon capture and storage”† In summary, crops are being planted; they absorb CO2 of the atmosphere through the natural process of photosynthesis; are then burned to provide energy. Instead of being released into the atmosphere, CO2 that is released is collected via a chemical process and then injected into the soil.
Another possible solution is to build technological facilities that contain CO . catch immediately2 present in the air, like a large vacuum cleaner. Like the above option, it is stored in cellars. About ten units exist around the world today. The potential is uncertain: the largest unit, installed in Iceland, now takes a year to absorb what humanity radiates in seconds.
Opposite effect
This does not deter investors. Climeworks, the Swiss company that owns this facility, raised 650 million euros the day after the report was published. “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. †
→ RESEARCH. Fighting global warming: the gamble of CO2 capture
Thus, the authors point out that these two technologies are potentially expensive and carry risks. Most of it competes for land for bioenergy. In the case of CO capture2 directly into the air, one of the risks is the opposite effect: emitting more than it is absorbed, due to the energy required to perform the operation.
Capture industrial emissions
These solutions should not be confused with carbon capture and storage (CCS) technologies, which work according to the same logic, but capture the emissions directly from an industrial or power-generating unit. “By 2050, these techniques are needed to reduce residual emissions from cement and chemical production, which, unlike the steel production process, cannot be completely eliminated”says Chris Bataille.
Nevertheless, the report specifies that the CCS does not allow recording “all” carbon dioxide emissions from an industrial facility. And that it comes after other measures (use of carbon-free energy, energy or material efficiency). It is therefore primarily the reduction of emissions that must be pursued. The report specifies: “than a greater decrease in demand” (ie our use and consumption) will include: “less dependency” to carbon removal.
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A reduction in emissions that are needed in parallel
Between 2010 and 2019, greenhouse gas emissions averaged 56 gigatons per year. They have increased by an average of 2.1% each year. By comparison, replanting forests and restoring ecosystems offers an annual reduction potential of about 3 gigatons per year by 2030.
Thus, the IPCC estimates that in hopes of keeping global warming below 1.5°C or 2°C,CO emissions2 should reach a maximum before 2025 and then decline rapidly. Warming below 2°C implies a reduction of at least a quarter by 2030.
