The most recent report by the world’s top climate scientists was alarmingly clear: If we are to avoid the most calamitous consequences of warming our planet, we must get as good at taking carbon dioxide out of the atmosphere as we’ve been at putting it in. Even if solar panels and wind turbines sprout like mushrooms, reaching “net-zero” is going to require capturing large amounts of emissions from activities that are hard to decarbonize, like making cement. Holding temperatures down will also require vacuuming huge amounts of carbon out of the air. The challenge is that current technology for both these tasks is a long, long way from being able to reach these goals.
1. How big is the problem?
In a projection by the International Energy Agency (IEA) of a pathway to net-zero emissions by 2050, about 7.6 billion metric tons (or gigatons) would still need to be eliminated annually, a figure equal to about a fifth of current emissions. And depending on how quickly net-zero is reached, limiting warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) above mid-19th century levels could mean removing anywhere between 100 billion tons of carbon and 1 trillion tons by 2100. That last figure would mean sucking up all the carbon that has been emitted this century, and then some.
2. Couldn’t we just plant a gazillion trees?
Everyone likes the idea of planting trees to pull carbon from the air through photosynthesis. Reforestation and other such “natural climate solutions” could produce 37% of the cuts needed by 2030 to put the world on track to meet the goals of the 2015 Paris Agreement, according to a 2017 estimate. But that much tree-planting would likely require high-quality land three times the size of India. And meanwhile, we can’t seem to protect the forests we already have, in the Amazon and elsewhere.
3. What are the main options?
Two methods, known as carbon capture and storage (CCS), and direct air capture (DAC). Capture-and-storage has gotten most of the attention so far, largely because it’s been promoted by the fossil fuel industry as the thing that will solve its emissions problems. If you remember hearing the phrase “clean coal,” it was likely a reference to a CCS plant – or, more likely, an idea of one rather than something that actually existed.
4. How does CCS work?
Think of a vacuum cleaner set on top of a smokestack. That is, CCS involves collecting CO₂ as it’s being emitted by a big source of pollution – by generators burning fossil fuel to make electricity or by factories or other industrial facilities – then sending it for use elsewhere or for storage deep underground. The technology dates back to the 1970s, when oil companies in the U.S. realized that pushing carbon dioxide into aging oil wells would allow them to squeeze out a bit of extra oil. As a side effect, the carbon remained trapped in the surrounding rock. Then in the 1990s, as climate became more of a public concern, Norwegian oil giant Equinor ASA began sinking CO₂ in saline reservoirs so it could avoid paying a carbon tax. Ever since, CCS has been discussed as a way to limit the damage caused by fossil fuels without having to abandon them.
5. What’s the challenge for CCS?
The cost. Since 2010, dozens of projects have been shelved because the technology was too expensive. After nearly 50 years of commercial use, there are only about two dozen large-scale facilities that have CCS; altogether, they capture roughly 40 million tons of carbon annually, or about 0.1% of global emissions. CCS is also opposed by many climate activists. They say energy companies are using the prospect of CCS to slow the transition to an all-renewables economy.
6. What’s the case for CCS?
Some stark climate math. Since some crucial industries such as steel and cement production rely on carbon-based chemical processes or temperatures that are hard to reach except by burning carbon, climate scientists and many governments, businesses and investors have come to assume that CCS will be an inevitable part of getting to zero.
7. What is the private sector doing?
Betting on that inevitability: Since the start of 2020, governments and industry have committed more than $25 billion for CCS projects, according to the IEA. U.S. energy and chemical companies led by Exxon Mobil Corp. have proposed building a $100 billion CCS hub to capture emissions from the cluster of refineries in and around Houston. They say the project could capture store 50 million tons of carbon a year by 2030 and double that amount by 2040, an amount equal to 22 million cars driven for a year – but only, they say, if the government provides sufficient subsidies. Even that is a drop in the bucket of what might eventually be built. In a 2018 report, Royal Dutch Shell Plc suggested that we’d need 10,000 large-scale CCS facilities by 2070 to meet the 2C goal.
8. What are governments doing?
An infrastructure bill signed by President Joe Biden includes $3.5 billion to expand CCS programs. A tax credit for carbon capture was recently expanded from $20 a ton to $50 a ton to make such projects more financially rewarding. Biden’s proposed Build Back Better legislation would raise that to $85 per ton for projects that capture 75% of their carbon emissions, a provision that some environmentalists complain could steer billions of dollars to coal plants. In the U.K., the Netherlands and Norway, national governments plan to spend about $5.6 billion to support large-scale projects to capture carbon emissions from industrial sites and store the gas under the North Sea. Rapidly rising carbon prices in Europe are also making the technology increasingly attractive. China is counting on CCS to help meet its 2060 net-zero goal, but currently the country has only a few small-scale pilot projects.
9. What is direct air capture?
If CCS is a vacuum cleaner on a smokestack, DAC is one set out in the open air. Cleaning up carbon this way is a much harder task: While nearly one-fifth of the gas going up a coal-burning plant’s smokestack is carbon dioxide, the atmosphere is only about 0.04% carbon.
10. How does it work?
Research labs and startups are developing competing methods to capture carbon through a variety of chemical reactions. (One of carbon’s notable characteristics is the ease with which it binds to other materials.) In some cases, the product is recycled for commercial purposes into such products as industrial chemicals or plastics. In others it’s stored beneath the ground, as with CCS.
11. What are its prospects?
This is an industry that’s barely into infancy. The world’s largest functioning direct air capture plant, which will take 4,000 tons annually from the air and store it geologically, just came online in Iceland in September. That just about doubled the world’s previous DAC capacity. It’s also equal only to the annual emissions of 250 average U.S. citizens. And right now DAC is prohibitively expensive: Sucking up carbon at the Iceland plant costs about $600 per ton – compared with a late November price of 75 euros ($85) on the EU’s market for a permit to emit a ton of carbon. For it to be a useful climate remedy rather than a pipe dream, costs either have to come way down or the world has to decide it’s willing to spend trillions of dollars adjusting the atmosphere.
12. What are governments doing?
The new U.S. infrastructure law includes $3.5 billion for carbon removal projects. The Biden administration also announced a “moonshot” program to speed innovation in DAC with a goal of getting costs below $100 a ton. The EU in November set a goal of removing 5 million tons of carbon from the atmosphere annually by 2030. It was an early backer of Swiss startup Climeworks AG, which built the Iceland plant. The U.K. government is spending 100 million pounds ($135 million) to support early-stage direct air capture technologies. It expects the technology will need to be scaled up in the late 2020s and early 2030s to help hit the country’s target of reaching net-zero emissions by 2050. Elon Musk and his foundation have put up $100 million for an XPrize carbon capture award, and Bill Gates, working with the EU, has raised hundreds of millions of dollars to support four young industries, including carbon capture.
13. Are there other alternatives?
Yes, though none of them have yet been shown to be more practical than CCS or DAC, and some come with greater risks or unknowns.
• Bioenergy with carbon capture and storage (BECCS): First, plants are grown that absorb carbon. Then that biomass is burned to generate power. Those emissions are captured and buried, making for a carbon-negative power system. As with reforestation, massive amounts of high-quality land would be needed.
• Soil carbon sequestration: Making changes to agricultural practices, including increased use of cover crops and restoration of grasslands, could increase the amount of carbon that’s stored in the ground.
• Enhanced weathering: Silicate minerals, such as basalt, absorb carbon when exposed to air. Some scientists have proposed that grinding such stones to powder and spreading it over large areas could speed that process. Crushing and spreading the stone may involve large outlays of energy, but increased crop yields could be one benefit.
• Ocean fertilization: In theory, adding iron to ocean waters could promote the growth of plants that can absorb carbon and store it on the seabed. In practice, there have been worries about side effects and whether it would even work.
• The International Panel on Climate Change’s chapter on carbon capture in its August 2021 report.
• The International Energy Agency’s website on carbon capture, and a report on its role in reaching net-zero by 2050.
• A Bloomberg News article on environmentalists’ opposition to carbon capture provisions in the U.S. infrastructure bill, and a letter from a group of scientists calling carbon capture an obstacle to a clean energy transition.
• A Bloomberg News feature on the world’s largest direct air capture plant, in Iceland.
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