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In addition to rapidly reducing the carbon dioxide we, humans, release into the atmosphere in huge quantities, recent scientific assessments of climate change have all suggested that reducing emissions would not be enough to prevent rising temperatures from rising. 1.5 or 2 degrees Celsius. .
The Intergovernmental Panel on Climate Change and Others have all stated that the extraction of CO2 in the air would be necessary if we wanted to curve the rising curve of temperatures before the end of the century.
These ideas are controversial, some considering them as a distraction from the pressing activity of limiting CO2 emissions.
- "Step forward" to suck CO2 from the air
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But a new assessment from the US National Academies of Science, Engineering and Medicine indicates that some of these "negative-emission technologies" are ready to be deployed, on a large scale, right now.
The authors point out the fact that the US Congress recently passed the 45Q tax rule, which provides a $ 50 tax credit for every tonne of CO2 captured and stored. Thus, their study highlights some available technologies between $ 20 and $ 100 per ton.
1- Coastal blue carbon
This report indicates that there is a strong potential for increasing the amount of carbon stored in live plants and sediments found in swamps located near the seashore and in the vicinity of estuaries. They include mangroves, tidal areas and seagrass beds.
Together, these wetlands contain the highest carbon stocks per unit area of all ecosystems.
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Mangroves like these constitute an important reservoir of carbon
The study of national academies indicates that by creating new wetlands and restoring and protecting these peripheral areas, it is possible to more than double the current rate of carbon extracted from the atmosphere.
In addition, the study indicates that it is a relatively inexpensive option, in which carbon can be captured for around $ 20 per tonne.
The disadvantages, however, are that these coastal ecosystems are among the most endangered areas of the planet, with an estimated destruction of 340,000 to 980,000 hectares each year.
When you degrade these areas, instead of absorbing CO2, they become an important source of gas.
Another problem is that the rise of the seas in the world could overwhelm and destroy the swamps. Another restriction is that there is simply not enough coastal areas.
"Although coastal engineering is very expensive, coastal blue carbon is probably the least expensive option we have," said Professor Stephen Pacala, of Princeton University, who said chaired the report.
"The problem is that the total capacity is not so great."
2 – Plant trees
Global deforestation has been an important factor in increasing carbon emissions. Researchers therefore feel that planting new trees or restoring lost areas is a simple and inexpensive technology that could be developing at this time.
One of the problems, however, is that while researchers understand very well which trees are the best to cultivate for timber harvesting, they are less knowledgeable about the selection of trees primarily for carbon removal from the atmosphere.
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Planting trees on degraded lands is considered important for carbon removal
Almost all countries have started tree planting as an inexpensive way of reducing carbon – the report says this is very useful as long as trees are planted on degraded land.
"The problem is that when you try to scale up, you start competing with land for food production," said Dr. Phil Renforth of Cardiff University, UK, who considered the report.
"So, there will definitely be a need for other things in this space too."
The report says that this can also be done for $ 20 per ton of CO2, or less. The study also calls for more research to develop crops that absorb and sequester more carbon in soils.
3 – Forest Management
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Forest management can have a significant impact on the amount of carbon that they store
In addition to planting more trees, the report says we need to manage our existing forests to remove more carbon. This can also be done for less than $ 20 per ton of CO2.
Techniques may include rapid replenishment of forests after disturbances such as fires. They may also involve lengthening the age of the forest during harvest.
A crucial step would be to increase the amount of wood used in long-lived wood products and to limit the amount of biomass burned in power plants.
4 – Agricultural practices
The report says that simple changes in the way farmers manage their land can be an effective and inexpensive way to remove carbon from the air.
This includes planting cover crops when fields are not used for commercial cultivation. It means cultivating crops with reduced tillage and involving the addition of a material called biochar, a type of charcoal made from plant material, to the soil.
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Make biochar in a pit, which can help soils store more carbon
"Changing farm management practices has tremendous benefits in terms of soil and water fertility, but there are challenges ahead," said Kelly Levin, World Resources Institute's expert on carbon removal.
"This includes the question of how permanent this carbon retention is.There is always a challenge of scale.If these practices really mean something, you have to implement them. on a very large surface. "
According to the report, this is a more expensive option, between $ 20 and $ 100 per tonne of CO2.
5 – Biomass energy with carbon capture and storage (BECCS)
The idea of BECCS is to grow energy crops that absorb carbon, which is then burned to produce electricity, while emitted CO2 is captured and buried permanently in the soil.
BECCS has been fired by many people because of the huge amount of land that would be needed, accounting for up to 40% of the world's cropland, according to some studies.
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Crops such as willow can be grown to be burned as an energy source with emissions captured and stored underground
But this new report indicates that BECCS can make the difference and at a reasonable cost – between $ 20 and $ 100 per tonne.
According to BECCS, simply feeding BECCS from waste could eliminate up to 5 billion tonnes of CO2 from the air – that's a considerable amount, but it would be a huge logistical challenge because it would have to be collected and deliver all agricultural, forestry and economically available products. municipal waste.
"If you have dedicated bioenergy crops that dislodge other land uses, such as forests or farms, the production of food and fiber would be reduced and you could increase commodity prices." and actually cause biodiversity loss and ecosystem services, "said Kelly Levin of WRI.
"BECCS must be done very carefully."
What other ideas does the report examine?
The study also takes into account the direct capture of CO2 and the mineralization of carbon in the air.
Direct capture in the air involves the use of machines equipped with chemicals capable of absorbing carbon. To date, a few start-up projects, such as Climeworks in Switzerland and Carbon Engineering in Canada, have shown that this can be done, even if costs remain high.
The mineralization of carbon involves the exposure of rocks, including basalt, that react with carbon dioxide that becomes trapped, turning into mineral in the pores of the stone. This has been done successfully in Iceland, although the technique remains expensive.
"There could be major new weapons," said Professor Pacala.
"There is a good chance that less than $ 100 per tonne for direct air capture can be developed within 10 years, there is a high probability that this will happen, no guarantee but high probability."
What will be the effectiveness of these ideas?
The report states that current technologies costing less than $ 100 per tonne can be safely scaled and stored large amounts of carbon, but much less than is needed to avoid dangerous climate change.
To meet the Paris agreement on global warming – about 20 billion tons of CO2 will have to be removed from the atmosphere every year by 2100. The technologies evaluated in the report would eliminate " significantly less than 10 billion tonnes of CO2 ".
If we develop cheap CO2 removal technology, will people not continue to use fossil fuels?
The report recognizes that there is a significant "moral hazard" here.
"If you present the sounding sirens of negative emissions, does this lessen humanity's willingness to invest in the mitigation measures needed to reduce emissions? This is a concern we discussed at every meeting, "said Professor Pacala.
"We are an academy committee and our job is to offer the public all the options that we offer – and I guarantee you that the larger the portfolio of tools we can use will be, the easier the job will be and the lower the temperature increase that humanity will endure.
"Our job is to present this opportunity to the public with a clear understanding that this moral hazard exists."
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