The Techonomy 2019 conference has the theme, “Reset and Restore.” That urgently includes climate action. This article was produced in tandem with the conference.

Many people believe that if we all just drove electric cars, used LED lightbulbs, and even did things like sail across the ocean rather than fly, the resulting reduction in pollution could somehow stop global warming. Unfortunately, it isn’t true. Yes, the world has to radically reduce emissions of carbon dioxide (CO2) and other global warming gasses. But to avoid planetary catastrophe, we also must remove a vast amount of CO2 that’s already in our atmosphere.

The United Nations’ Intergovernmental Panel on Climate Change (IPCC) says average global temperatures cannot be allowed to exceed, at the very most, 2 degrees centigrade above the average that prevailed before industrialization. If possible, the increase shouldn’t exceed 1.5 degrees. Otherwise, we face even more violent weather, damaging wildfires, rising sea levels, water scarcity, an unstable food supply, and who knows what other horrors. And here is a key but little-discussed passage from an important 2018 IPCC report: “All pathways that limit global warming to 1.5°C with limited or no overshoot project the use of carbon dioxide removal (CDR).” Note the word–“all.”


“We’ve got to keep temperature rise to 1.5 degrees, and that can’t be done without carbon removal,” summarizes James Mulligan, who works fulltime on this issue at the World Resources Institute (WRI), a large global non-profit focused on natural resource sustainability. Adds Leslie Jones, a vice president and climate expert at the Environmental Defense Fund (EDF): “The National Academy of Sciences has concluded that if we’re going to have a fighting chance to limit warming to 1.5 or even 2 degrees, we’ll have to do two things–aggressively slash greenhouse gas emissions and deploy carbon removal, both natural approaches and emerging technologies.”

Containing emissions will be all the more challenging given the world’s other needs. The United Nations’ 17 Sustainable Development Goals for 2030 articulate many things we must achieve for a fairer, healthier world. Goal number 13 is “Climate Action.” But other goals demand economic inclusion and societal health. Those can’t be achieved without ongoing economic growth, particularly in developing countries that were excluded from the industrial world’s 20th century accumulation of wealth. The legitimate demands of previously excluded people will thus place more pressure on global atmospheric CO2.

Warming gasses are still getting worse in the atmosphere, but it won’t be enough to make them stop, go down, or even disappear. We literally have to suck them up. Neutral is not enough. To meet the 1.5 degree target, says the EDF’s Jones, “We need to reach net zero greenhouse gas emissions by 2050, and keep that trend line going down to net negative.” Already 60 nations have committed themselves to “net zero” emissions, including Britain, France, and Germany. Eliminating all CO2 emissions will almost certainly be impossible. (There’s little near-term likelihood of electric airliners, for example.) So we’ll need rapid progress in CDR just to get to “net zero,” and far more to go “net negative.” Here’s the bottom line: carbon removal at large scale is indispensable for maintaining a livable earth.


An impressive range of CDR approaches are being developed. Some are simple. Others are esoteric and technologically challenging. Yet none are being pursued aggressively enough. In hopes that might change, here are some possibilities:

1. Planting Trees

The most promising and easiest-to-implement CDR methods all involve something quite basic–growing more plants. No current technology can compete with photosynthesis as an efficient way of capturing CO2. Plants are made from it. For years, people buying “carbon offsets” to salve their guilt for airline trips or other CO2-generating indulgences have paid for someone somewhere to plant trees. They are ideal “carbon sinks,” as are shrubs and even algae and seaweed in oceans. We all need to plant more plants, more places, every chance we get. Says the World Resources Institute’s Mulligan: “There are a lot of roadsides and suburban areas that shouldn’t have had the trees removed in the first place.” The only reason not to plant more trees is if doing so displaces farmland otherwise needed to grow food.

But recent calculations suggest enormous potential impact if we plant more. A July study in Science Magazine projected that planting a trillion trees could sequester more than 200 billion tons of carbon, enough to make a major dent in warming gasses. (Humans emit between 30-40 billion tons of CO2 each year.) While other scientists questioned the report’s methodology, it has helped raise awareness about planting more trees.

Many large-scale efforts to plant trees are already underway. Amazon (the company), for example, has committed to spending $100 million on reforestation in coming years, as part of a pledge to produce “net zero” carbon by 2040. India has recently planted over 2 billion trees, and Ethiopia has a project underway to plant 4 billion in 2019. Forest cover has declined from one-third of Ethiopia’s land in 1900 to less than 4% today.

2. Reforming Agriculture

While forestland has potential to sequester considerable carbon, the world’s 3.6 billion acres of agricultural lands could be an even bigger opportunity. If farming can become more carbon-conscious, vast amounts of CO2 might be stored in the soil by this, the world’s largest industry–$3.5 trillion in annual revenues. Again, the key is simple: grow more plants. Among practices farmers can change: stop tilling fields (it kills plants and releases carbon); plant “cover crops,” especially legumes, on the same fields in off seasons; and eliminate or reduce use of chemical fertilizers, which pollute waterways, emit warming gasses, and require fuel-burning trucks to transport.

One ambitious effort to move in this direction is the Terraton Initiative, a spin-off from Boston startup Indigo Ag. The initiative was set up as a separate public benefit corporation, along with another related non-profit group to advance the project’s scientific, technical, and policy goals. “The soil beneath our feet [can] absorb one trillion tons of atmospheric carbon,” a marketing document proclaims. Terraton aims to develop a system by which farmers get paid for climate-friendly techniques via carbon credits, purchased by individuals or companies. Says Indigo Ag CEO David Perry: “Ideally you’ll be able to buy credits and link them all the way back to the specific farmer who changed their practices.” Again, skeptical analysts have questioned the “trillion ton” calculation, but encouraging farmers to change is pragmatic. For one thing, farmers are increasingly alert to the climate crisis, as rapidly-changing weather brings droughts, floods, and fires.


This project merits attention in part for the financial might that buttresses it. Indigo Ag is among the world’s most highly-funded startups, having raised $700 million. It aims to systemically restructure agriculture through a wide range of reforms. It makes microbial substitutes for fossil-fuel-based fertilizers; owns a global satellite network to track growing conditions and farm data; has developed an online platform for U.S. farmers to sell products outside of the traditional “commodity” system, encouraging them to grow more profitable specialty crops; transports and stores grain; and deploys data analytics to help farmers be more energy- and resource-efficient. The Terraton Initiative along with its related non-profit, says Indigo Ag’s Perry, “will provide incentives for all the things we’re trying to get farmers to do.”

3. Bioenergy With Carbon Capture and Storage

No matter how well we control carbon emissions, we still need to generate energy, and in many cases use fuel. Bioenergy with Carbon Capture and Storage (BECCS) piggybacks on how plants remove atmospheric carbon, by burning them for energy while capturing the carbon. Then the CO2 is stored or sequestered. The process aims to be carbon negative, even as it generates energy. Though it is more costly than most other forms of energy generation, five BECCS facilities are already operating in the U.S. and Canada, collectively capturing 1.5 million tons of CO2 annually. (More are planned in both Japan and Europe.) The largest is an Archer Daniels Midland ethanol plant in Decatur, Illinois, which injects the captured CO2 underground. While BECCS has momentum, it also has many detractors. Some worry, for example, that land devoted to bioenergy will compete with that for crops, raising food costs.

4. Direct Air Capture Technologies

This is sci-fi CDR. At least three companies are now building giant machines that pull ordinary air through solvent-filled chambers. The solvents bind with CO2 to extract it from the air. The result is heated to release concentrated CO2, which is either sequestered, usually underground, or re-used to make fuel or other products. The U.S. Congress recently allocated $60 million for research, with bipartisan support.

The cost to extract one ton of CO2 using such machines has dropped from about $600 in 2011 to $300 now, and could get as low as $100, according to a recent report by the National Academy of Sciences. While that would still be high, it compares favorably to other methods of sequestering carbon. Carbon Engineering, one prominent such startup, uses the extracted carbon to create fuel–in effect, making energy out of the air. The Canadian company has attracted money from Bill Gates and Chevron, among others.

5. Enhanced Carbon Mineralization

Many rocks react with CO2 and fix it into a solid, especially rocks found in the earth’s mantle, miles below the surface. This is an appealing and possibly inexpensive way to reduce atmospheric concentrations, but introducing air to rock is not easy. In a few places, like Oman, such rock is exposed already.

One possibility is injecting concentrated CO2 into the earth to where the rocks are found, or mining the rock and grinding it up so it can “weather.” Either way, the CO2 is permanently removed from the atmosphere. This contrasts with many other forms of carbon removal, which risk eventually releasing CO2 back into the air. Trees, for example, may capture carbon, but only until somebody decides to cut them down and burn them.

6. Carbon-capturing Cement

There are innumerable other innovative ideas emerging to remove atmospheric carbon. One, for example, is making cement with CO2 instead of water. Not only does it capture and solidify carbon, but the process requires significantly less energy than conventional cement. This could be a big deal since the vast worldwide cement industry produces as much as 8% of total CO2 emissions. Solidia Technologies, based in Piscataway, New Jersey, is making great progress. Investors include BASF, BP, VC firm Kleiner Perkins, and Sun Microsystems co-founder Bill Joy.

The obstacles to capturing carbon at scale are many. The biggest is cost. Without economic incentives, almost none of the promising efforts described here are likely to take off. We need government-enforced carbon taxes and/or carbon-credit trading mechanisms (often called “cap and trade”).

Meanwhile, many environmentalists have long considered even talk of such measures as a near-criminal distraction from what they consider more urgent efforts to reduce emissions. A letter sent in early 2019 to members of Congress by more than 600 environmental groups called carbon capture an unsavory “corporate scheme.” Signers included Greenpeace USA, Friends of the Earth US, and the politically-influential Sunrise Movement.

But despite the skepticism of anti-corporate climate purists, we have no choice. And it might work. As I finished interviewing World Resources Institute’s Mulligan, I said to him, “Carbon capture suggests that for all our ineptitude thus far, we may still have a chance to meet the IPCC targets.”

“If I didn’t think that,” he replied, “I’d be building a bunker.”