Nature has equipped the Earth with several giant “sponges”, or carbon sinks, that can help humans fight climate change. These natural sponges, as well as those made by humans, can absorb carbon and effectively remove it from the atmosphere.
But what does this act of science fiction really involve? And how much will it actually take – and cost – to make a difference and slow down climate change?
Sabine Fuss has been looking for these answers for two years. An economist in Berlin, Fuss heads a research group at the Mercator Research Institute on Global Commons and Climate Change and was part of the first Intergovernmental Panel on Climate Change (IPCC) – created by the United Nations to assess science, the risks and impacts of global warming. After the 2018 panel report and the new Paris Agreement target of keeping global warming at 2.7 degrees Fahrenheit (1.5 degrees Celsius) or less, Fuss was tasked with carbon elimination strategies were the most promising and feasible.
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Afforestation and reforestation – planting or replanting forests, respectively – are well-known natural carbon sinks. A large number of trees can sequester greenhouse gas, carbon dioxide (CO2) from the atmosphere for photosynthesis, a chemical reaction that uses energy from the sun to convert carbon dioxide and water into sugar and oxygen. According to a 2019 study in the journal Scienceplantation 1 trillion trees could store about 225 billion tonnes (205 billion metric tonnes) of carbon, or about two-thirds of the carbon that humans have released into the atmosphere since the start of the Industrial Revolution.
Managing farmland is another natural approach to removing carbon that is relatively low risk and is already being tested, according to Jane Zelikova, terrestrial ecologist and chief scientist at Carbon180, a nonprofit advocating strategies removal of carbon in the U.S. Practices such as rotational grazing, reduced tillage, and crop rotation increase carbon input through photosynthesis, and this carbon is ultimately stored in root tissues which decompose in ground. The National Academy of Sciences found that carbon storage in soil was enough to offset up to 10% of the United States’ annual net emissions – or roughly 632 million tonnes (574 million tonnes) of CO2 – Low cost.
But nature-based carbon removal, like planting and replanting forests, can conflict with other policy goals, like food production, Fuss said. On a larger scale, these strategies require a lot of land, often land already in use.
That’s why more technological approaches to removing carbon are crucial, they say. With direct air capture and carbon storage, for example, a chemical process extracts carbon dioxide from the air and binds it to filters. When the filter is heated, the CO2 can be captured and then injected underground. There are currently 15 direct air collection plants in the world, according to the International Energy Agency. There is also bioenergy with carbon capture. With this method, plants and trees are cultivated, creating a carbon sink, and then organic matter is burned to produce heat or fuel known as bioenergy. During combustion, carbon emissions are captured and stored underground. Another trick of carbon capture involves mineralization; in this process, the rocks are crushed to increase the surfaces available to chemically react and crystallize the CO2. Then, the mineralized CO2 is stored underground.
However, none of these technologies have been implemented on a large scale. They are extremely expensive, with estimates as high as $ 400 per ton of CO2 eliminated, and each still requires a lot of research and support before being deployed. But the United States is a good example of how a mix of carbon removal solutions might work together, Zelikova said: Land management could be used in the agricultural Midwest; basaltic rocks of the Pacific Northwest are ideal for mineralization; and the southwestern oil fields are already equipped with the right technology and skilled workers for underground carbon storage, she said.
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Ultimately, each country will need to build its own unique portfolio of CO2 phase-out strategies as no single intervention will be successful on its own. “If we were to exclusively increase one of them, it would be a disaster,” Fuss said. “It would use a lot of land or be prohibitively expensive.” His research has shown that afforestation and reforestation will be more productive in tropical regions, while differences in solar radiation in more northern latitudes with more albedo (reflection of light in space) mean that these countries will have probably more likely to invest in more technological interventions. , such as carbon capture and biomass extraction.
The need to deploy these solutions is imminent. The overall carbon budget, the amount of CO2 humans can emit before the global temperature rises 2.7 F (1.5 C) above pre-industrial levels, is around 300 gigatons of CO2, Fuss said.
“In recent years we have emitted 40 gigatonnes,” she said. In other words, there are only a few years left in this budget. A recent study in the journal Scientific reports suggests that it might be too late to wait, even in a few years, if we are to achieve the target set in the Paris Agreement. Based on their climate model, the authors predict that even if we stop emitting greenhouse gases altogether, “global temperatures will be 3 C [5.4 F] warmer and sea level 3 meters [10 feet] 2,500 higher from 1850. “To reverse the effects of climate change, 33 gigatonnes of existing greenhouse gases must be removed this year and every year in the future,” the researchers said.
The reality, however, is that these approaches are not ready and there is no consensus on how to pay for them. There is consensus among scientists on the next step: we must stop new emissions immediately. But, “since emissions are integrated into our daily lives and our infrastructure,” Fuss said, “[carbon] the kidnapping comes more to the fore. “
Originally posted on Live Science.
