Carbon is the Jekyll and Hyde of the periodic table — part angel, part devil. Sometimes called the "giver of life," carbon forms the structure of every cell in our bodies and most of the stuff we eat, use and treasure, from vitamins to violins, doughnuts to diamonds. Carbon was critical to the evolution of the universe 14 billion years ago, and it’s just as vital for the technologies of the future.
Carbon dioxide is equally critical to the atmosphere. It traps the sun’s heat, and without it our planet would be impossibly cold. But human activities — principally burning fossil fuels — have increased CO2 levels by around 50 percent, from 270 parts per million (ppm) at the dawn of the Industrial Revolution to 415 ppm today. The last time atmospheric CO2 levels were this high was more than 3 million years ago. What concerns scientists is the acceleration in emissions, which over the past 60 years has been about 100 times faster than previous natural increases, such as at the end of the last ice age.
Steering the planet onto a 1.5C pathway
Since the Paris Agreement in 2015, the idea of a pathway limiting global warming to 1.5 degrees Celsius above pre-industrial levels has become paramount. To have even a chance of hitting this target, global greenhouse gas (GHG) emissions need to peak by 2025 at the latest and be reduced by 43 percent by 2030, achieving net zero no later than 2050. The great majority of these reductions must come from decarbonizing our industries, agriculture and lifestyles. The net-zero standard of the respected Science Based Targets initiative, for example, calls on companies to decarbonize 90 percent of their value chains by 2050.
But despite efforts to decarbonize human activities, "carbon dioxide removal," or CDR, will play a vital role, for three reasons. First, it is extremely difficult to fully decarbonize some essential but "hard to abate" industrial sectors, such as long-range aviation, cement and steel. Second, the Earth system itself is emitting more greenhouse gases as global warming continues to increase. Third, we need to undo legacy emissions from the past, as well as remove present and future unabated emissions to prevent an otherwise likely overshoot of the 1.5 degrees C target.
We cannot afford to wait and see if CDR will be necessary. We must start building the necessary capacity right now to actively remove CO2 from the atmosphere, in parallel with — not instead of — doubling down on decarbonization efforts. According to the Intergovernmental Panel on Climate Change (IPCC): CDR "is a key element in scenarios likely to limit warming to 2 [degrees] C or lower, regardless of whether global emissions reach near-zero, net-zero or net-negative levels."
Put simply: The way the world is currently heading with CO2 mitigation, we are unlikely to reach global net zero by 2050 and limit global warming to 1.5 degrees C, without scaling up CDR technologies to deliver billions of metric tons of removals every year.
So many ways to remove CO2, but we need tech as well as nature
Carbon dioxide can be removed from the atmosphere by natural, technological or hybrid processes. Planting billions of trees and restoring peatlands are natural climate solutions that absorb CO2 while bringing many ecosystem benefits, such as enhancing biodiversity and rainfall, while reducing air and water pollution. However, while nature-based solutions are vital, ecosystems such as forests remain vulnerable to wildfires and degradation, threatening their capacity to lock away carbon indefinitely. Scalability is also a challenge as afforestation, for example, can compete with agriculture and other land uses.
Technological processes aim to tackle the issue of permanent carbon removal by capturing and storing CO2 indefinitely, usually in the form of solid minerals or in rock layers deep underground. The leading technologies are direct air capture with carbon storage (DACCS) and bioenergy with carbon capture and storage (BECCS).
DACCS uses banks of fans (powered by fossil-free energy, of course) to suck air into industrial structures where a range of chemical filters can be deployed to trap CO2 molecules. The filter material is then regenerated to release pure CO2 that can be buried deep underground. A pioneer of DACCS, Carbon Engineering, is building a facility in the oil- and gas-rich Permian Basin in west Texas that is expected to capture 1 million metric tons of CO2 a year — roughly equivalent to the absorption capacity of 40 million trees — when it becomes operational in 2024.
BECCS is a process that captures and stores CO2 emitted by power plants that convert biomass into heat, electricity or liquid or gas fuels. BECCS can process many types of "feedstock," including residues from forestry and agriculture, algae and energy crops. The process of capturing CO2 from the air has already taken place via the photosynthesis necessary for the biomass to grow. But to be carbon negative, it’s vital that the carbon footprint of growing, harvesting, transporting and processing these feedstocks doesn’t outweigh the volume of carbon the biomass itself had removed during its lifetime of growth. There are other concerns with BECCS, too — growing large amounts of dedicated bioenergy crops could convert existing forests and farmland, which in turn may threaten food and water security, displace communities, release carbon stored in trees and soils, and threaten biodiversity.
A new BECCS plant in Sweden, planned by Stockholm Exergi, is designed to address some of the technology’s drawbacks and prove it’s possible to provide a city with heating and electricity while removing CO2 from the atmosphere. To create heat and power, the plant will burn residues from forestry, sawmills, and pulp and paper production. The biomass is locally sourced, minimizing its carbon footprint. The CO2 emitted during combustion will be captured, compressed and cooled into liquid form, then injected into deep rock layers beneath the North Sea where it will further stabilize over time. Carbon Engineering believes the plant has the potential to capture 800,000 metric tons of CO2 per year — more than Stockholm’s entire annual road traffic emissions.
Carbon capture and storage technologies also hold out the tantalizing prospect of "sustainable carbon." Take aviation, for example. At this time, there’s no way around burning hydrocarbons to achieve the power density required for long-distance flight. But a DACCS or BECCS plant can create a closed loop by pulling carbon out of the air to be reused as a feedstock to produce synthetic kerosene. This process, known as "power-to-liquids" sustainable aviation fuel (PtL SAF) could cut aviation emissions by up to 90 percent. A similar process could be used to make low-carbon e-methanol for shipping.
Several hybrid CDR technologies — part nature, part technology — show promise. "Enhanced weathering," for example, involves spreading finely ground silicate rock onto land or sea surfaces to enhance carbon absorption. Another process uses biochar, a type of carbon made from any organic matter heated in the absence of oxygen. When added to soil, biochar can store carbon for durations ranging from decades to millennia. It brings added benefits, : By improving the soil's nutrient and moisture retention capacity, biochar helps reduce the need for fertilizers and prevents water runoff, thereby restoring agricultural productivity to marginal soils.
Scale matters, so does permanence
The World Economic Forum’s First Movers Coalition which aims to accelerate the decarbonization of seven "hard-to-abate" industrial sectors that account for 30 percent of global emissions, includes CDR as one of its core goals. The First Movers Coalition calls on its members to commit to remove at least 50,000 metric tons, or $25 million worth of carbon removals by 2030 — "in addition to maximal direct emissions reduction efforts."
The coalition has set the bar very high. First, any CDR approach must be permanent — capturing and storing carbon for over 1,000 years. Second, it must be scalable — solutions that can potentially store at least 1 million metric tons (1 megatonne, or 1Mt) of carbon by 2030 and 1 billion metric tons (1 gigatonne, or 1Gt) by 2050. Two other critical criteria are cost and verification.
Scale matters. A recent report by the Energy Transitions Commission on how CDR can help keep 1.5C alive has estimated roughly how much CDR might be needed: "To neutralize the impact of the likely carbon budget overshoot ahead of mid-century, our scenarios suggest a need for at least 70-225 Gt CO2 of cumulative removals between now and 2050." That’s between 2.5 billion and 8 billion metric tons of CDR every year.
So how do current CDR technologies measure up against these tough standards?
DACCS and BECCS each have the potential to capture 5 billion metric tons (5 Gt) of carbon per year and store it for over 1,000 years, plus they are easy processes to verify. But they’re very expensive, costing $110-270 per metric ton for BECCS and $600 or more per metric ton for DACCS.
Biochar and enhanced weathering, although less mature as technologies, could potentially each deliver 3-4 Gt annually at a cost of just $50-160 per metric today. But while enhanced weathering will probably pass the permanence test, most current biochar methods can only guarantee storage for up to 500 years. Nevertheless, the First Movers Coalition is encouraging its members to get behind all four emerging CDR technologies.
Kick-starting market demand for CDR
As with many innovations, progress comes down to hard cash. CDR lacks a market to drive it forwards. It makes seemingly no sense to pay a DACCS plant $600 to remove one metric ton of CO2 when you can spend $30 per metric ton on a nature-based alternative. Yet, over the mid to long term, we badly need these emerging technologies to remove CO2 at the scale and permanence our planet requires. So, someone has to make the first move and kick-start the market.
Global reinsurer Swiss Re has helped shape the challenge thrown down by the First Movers Coalition for each member to commit to at least 50,000 metric tons, or $25 million of durable and scalable net carbon removal by 2030. Swiss Re is one of five founders of the NextGen CDR Facility, a buyers’ club committed to the purchase of over 1 million metric tons of verified CO2 removals by 2025. The aim is to dramatically scale up CDR technologies such as DACCS and BECCS and to catalyze the market for high-quality carbon removals.
Demonstrating market demand sends a vital signal to innovators to scale up to the next level. Each iteration of their nascent technology steps up supply by around tenfold, creating a risk that demand won’t keep pace. So the First Movers Coalition’s goal is find sufficient CDR buyers to make the technologies bankable. In anticipation of future economies of scale, NextGen has promised its participants to cap the average cost of CO2 removed through the facility at $200 per metric ton.
Even so, this is a hefty price. Some scale-up will happen through voluntary carbon markets, but it’s unlikely we can reach metric gigatons of carbon removals by 2050 without regulatory intervention. President Joe Biden has given the industry a big boost with his recent Inflation Reduction Act. Part of the $369 billion of public money committed to the climate includes a subsidy of $130-180 per metric ton of CO2 removal. This is one of many steps governments can take to motivate the trillion-dollar fossil fuel industry to transition into a trillion-dollar carbon management industry, in line with global climate protection goals.