Carbon capture focuses on trapping CO2 emissions at their source. Carbon sequestration deals with the long-term storage of that captured carbon.
The processes seem to offer great potential in the fight against climate change, working together to reduce the amount of CO2 in the atmosphere.
This confidence is reflected in policies like the EU’s Net-Zero Industry Act and Carbon Removal Certification Framework, the Inflation Reduction Act in the US and the £22 billion in funding for carbon capture and storage projects just announced in the UK.
Are they feasible solutions at scale? Current capture levels remain a very small fraction of global emissions, while there are question marks over soil carbon sequestration claims, with uncertainty in the science of how soils store and release carbon.
But we don’t have the luxury to discard these options, according to some scientists.
In one study, just published in Nature Food, researchers at the International Institute for Applied Systems Analysis (IIASA) in Vienna, Austria, explored the potential of carbon sequestration on farmland to combat climate change. These practices hold great potential for reducing global warming while reducing economy wide mitigation costs, they conclude.
To help absorb carbon dioxide from the air and store it in the soil or in plants on their farms, the study details how farmers can use techniques such a planting cover crops, using biochar (a type of charcoal made from organic waste), or practicing agroforestry (planting trees alongside crops or pastures), to turn their agricultural land into a carbon sink.
The study results indicate that by 2050, these agricultural practices could reduce as much greenhouse gas emissions as planting new forests, particularly in regions like sub-Saharan Africa and South America.
Carbon sequestration on agricultural land is not only important for climate change mitigation efforts, the research claims, but can also enhance agricultural productivity and resilience to climate change, and could help the agriculture, forestry, and land use sectors achieve net zero emissions globally by 2050 at costs between US$80 and $120 per tonne of CO2 equivalent.
“These efforts would not only cut overall economy-wide emission reduction costs when compared to a 1.5°C scenario without agricultural carbon sequestration practices, but also reduce losses of global economic output by 0.6% by mid-century under a climate stabilization scenario aiming to limit warming to 1.5°C,” notes study coauthor Andrey Lessa Derci Augustynczik, a researcher at IIASA.
“In addition, farmers could earn substantial income from these activities – up to $235 billion by 2050 – if they receive financial incentives for every additional tonne of CO2 stored in soils and biomass at a projected greenhouse gas price of $160 per tonne of CO2 equivalent in 2050.”
Carbon capture ‘not expanding fast enough’
Another study led by Chalmers University of Technology in Sweden and the University of Bergen in Norway, just published in Nature Climate Change, claims that large expansion of carbon capture and storage is necessary to fulfil the Paris Climate Agreement.
But the researchers warn the technology is not expanding fast enough to meet the 2°C target and even with major efforts it is unlikely to expand fast enough for the 1.5°C target.
The idea behind carbon capture and storage (CCS) technology is to capture carbon dioxide then store it deep underground. Some applications of CCS, such as bioenergy with CCS and direct air capture and storage actually lead to negative emissions, essentially “reversing” emissions from burning fossil fuels. CCS technologies play an important role in many climate mitigation strategies including net-zero targets. However, the current use is negligible.
“CCS is an important technology for achieving negative emissions and also essential for reducing carbon emissions from some of the most carbon-intensive industries,” says Jessica Jewell, associate professor at Chalmers University of Technology in Sweden. “Yet our results show that major efforts are needed to bridge the gap between the demonstration projects in place today and the massive deployment we need to mitigate climate change.”
Decrease in failure rates required
If all of today’s plans are realised, the researchers add, by 2030, CCS capacity would be eight times what it is today. But there are still doubts whether this capacity could achieve the CCS market’s ambitious aims.
“About 15 years ago, during another wave of interest in CCS, planned projects failed at a rate of almost 90%,” says Tsimafei Kazlou, PhD candidate at University of Bergen, Norway, and first author of the study. “If historic failure rates continue, capacity in 2030 will be at most twice what it is today which would be insufficient for climate targets.”
There are “obviously many challenges” not only with regard Measurement, Reporting, and Verification (MRV), adds Stefan Frank, a senior researcher at the IIASA.
But they must be explored and pursued, he believes, given the need for rapid emission reductions and given that there is no single one silver-bullet.
“We don’t have the luxury to discard these options but should rather use all the technologies that we have currently at hands and try to put them in practise. Besides, these agricultural CO2 sequestration options are interesting also from a climate change adaptation and resilience perspective.”
