Reduce greenhouse gas emissions to reduce global warming, but not only. In their report published on Monday, April 4, scientists from the IPCC (the Intergovernmental Panel on Climate Change) note that carbon dioxide removal technologies2 From the atmosphere now “Basic” To limit warming to 1.5°C or 2°C by 2100.
→ Read. IPCC report: How are we changing our lifestyles to reduce our emissions
Even a significant reduction in greenhouse gas emissions would leave some residual emissions ‘Difficult to eradicate’. At the same time, CO2 permanently emitted into the atmosphere. “We released a lot of what we will now have to make up for.”, explains Chris Patay, associate researcher at IDDRI (Institute for Sustainable Development and International Relations) and co-author of the report. Until then, carbon sequestration techniques had been seen primarily as hoaxes intended to delay climate mobilization.
additional forest cover
What are the options on the table? To stay below the 1.5°C mark, the scenarios considered by the IPCC plan to develop an additional 322 million hectares of forest cover by 2050, an area the size of India. In comparison, more than 420 million hectares of forest were lost due to deforestation between 1990 and 2020. Other solutions offer significant reduction potential, while being accessible at moderate cost: restoring CO2-absorbing ecosystems.2 (grasslands, mangroves), or even storing carbon directly in the soil, thanks to some agricultural practices.
Giec is also interested in long-term technological solutions that make it possible to capture CO2 directly2 into the atmosphere and then injected deeply into the ground. “Unlike nature-based solutions, these are permanent”Chris Patay explains. Because the effect of forest uptake can be reversed in the event of a fire, just as drought 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 short, crops are grown; They absorb carbon dioxide2 from the atmosphere through the natural process of photosynthesis; It is then burned to provide energy. Instead of being released into the atmosphere, CO . is released2 It is captured through a chemical process and then injected into the soil.
Another possible solution is to build technological facilities that directly capture carbon dioxide2 Present in the air, like a large vacuum cleaner. Like the above option, it is stored in cellars. About ten units exist today all over the world. The possibilities are 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. The Swiss company, Climeworks, which owns the facility, raised 650 million euros the day after the report was published. “It must be remembered that the IPCC does not recommend this or that solution, Chris Patay says. Explains solutions available to decision makers and their effects. »
→ investigation. Fighting global warming: the bet on capturing carbon dioxide
Thus the authors point out that these two technologies are potentially expensive and pose risks. For bioenergy, the bulk of it competes for land. In the case of capturing carbon dioxide2 Directly in the air, it is dangerous to have the opposite effect: to release more than is absorbed, due to the energy required to perform the procedure.
industrial emissions capture
These solutions should not be confused with carbon capture and storage (CCS) technologies, which work on the same logic but capture emissions directly from an industrial unit or electricity production unit. “In 2050, these technologies will be needed to reduce residual emissions from cement and chemical production, which, unlike the steelmaking process, cannot be completely eliminated.”says Chris Patay.
However, the report specifies that the CSC does not make it possible to capture “everyone” Carbon dioxide emissions from an industrial facility. It therefore comes after other measures (the use of carbon-free energy, or energy-efficient or materials). Thus, emission reduction must be targeted in the first place. Define the report “Of greater attenuation of demand” (i.e. our uses and consumption) will include “less dependency” to remove carbon.
The need to reduce emissions in parallel
Between 2010 and 2019, the average greenhouse gas emissions are 56 gigatons per year. It has increased at a rate of 2.1% every year. In comparison, reforestation and ecosystem restoration offers an annual reduction potential of about 3 gigatons per year, by 2030.
The IPCC therefore estimates this in order to hope to keep global warming below 1.5°C or 2°C.carbon dioxide emissions2 It should reach its maximum before 2025 and then decline rapidly. Warming of less than 2°C would mean a reduction of at least a quarter by 2030.