Yves here. As readers may have inferred, I am prejudiced against various climate change free lunches, where carbon generators act as if there are forms of techno-whizzery penance that will wash away their climate change sins. Biomass is on this list. I am nevertheless running this post because it is useful to understand what it is purported to do. Biomass could make a difference at the margin, but I would not bet on more than that.
By Ramin Skibba (@raminskibba), an astrophysicist turned science writer and freelance journalist who is based in the Bay Area. He has written for WIRED, The Atlantic, Slate, Scientific American, and Nature, among other publications. Originally published at Undark
On April 11, a small company called Graphyte began pumping out beige bricks, somewhat the consistency of particle board, from its new plant in Pine Bluff, Arkansas. The bricks don’t look like much, but they come with a lofty goal: to help stop climate change.
Graphyte, a startup backed by billionaire Bill Gates’ Breakthrough Energy Ventures, will bury its bricks deep underground, trapping carbon there. The company bills it as the largest carbon dioxide removal project in the world.
Scientists have long warned of the dire threat posed by global warming. It’s gotten so bad though that the long-sought mitigation, cutting carbon dioxide emissions from every sector of the economy, might not be enough of a fix. To stave off the worst — including large swaths of the Earth exposed to severe heat waves, water scarcity, and crop failures — some experts say there is a deep need to remove previously emitted carbon, too. And that can be done anywhere on Earth — even in places not known for climate-friendly policies, like Arkansas.
Graphyte aims to store carbon that would otherwise be released from plant material as it burns or decomposes at a competitive sub-$100 per metric ton, and it wants to open new operations as soon as possible, single-handedly removing tens of thousands of tons of carbon annually, said Barclay Rogers, the company’s founder and CEO. Nevertheless, that’s nowhere near the amount of carbon that will have to be removed to register as a blip in global carbon emissions. “I’m worried about our scale of deployment,” he said. “I think we need to get serious fast.”
Hundreds of carbon removal startups have popped up over the past few years, but the fledgling industry has made little progress so far. That leads to the inevitable question: Could Graphyte and companies like it actually play a major role in combating climate change? And will a popular business model among these companies, inviting other companies to voluntarily buy “carbon credits” for those buried bricks, actually work?
Whether carbon emissions are cut to begin with, or pulled out of the atmosphere after they’ve already been let loose, climate scientists stress that there is no time to waste. The clock began ticking years ago, with the arrival of unprecedented fires and floods, superstorms, and intense droughts around the world. But carbon removal, as it’s currently envisioned, also poses additional sociological, economic, and ethical questions. Skeptics, for instance, say it could discourage more pressing efforts on cutting carbon emissions, leaving some experts wondering whether it will even work at all.
Still, the Intergovernmental Panel on Climate Change, the world’s forefront group of climate experts, is counting on carbon removal technology to dramatically scale up. If the industry is to make a difference, experimentation and research and development should be done quickly, within the next few years, said Gregory Nemet, professor of public affairs who studies low-carbon innovation at the University of Wisconsin-Madison. “Then after that is the time to really start going big and scaling up so that it becomes climate relevant,” he added. “Scale-up is a big challenge.”
At Graphyte’s Arkansas facility, called Loblolly after a regional pine tree, chugging machinery takes unwanted wood and plant matter and casts it into 3-by-4-by-6-inch bricks — slightly larger than the red bricks used to build houses. Graphyte’s bricks are mostly made of carbon compounds, and they’re made so that they don’t decompose while they’re stored underground in former gravel mines, thereby preventing the emission of some greenhouse gases.
The technologies at Graphyte’s new processing facility are fairly simple. Front-end loaders at the plant feed biomass, like wood chips from nearby sawmills and rice hulls from rice production processing, into a series of machines, which direct the tiny biomass bits through a machine called a hammer mill, to reduce them down to a uniform particle size; through a rotary dryer about the length of a tractor trailer; and then into a briquettor to crush them into dense bricks.
The bricks are then encapsulated in film which, in addition to the low moisture of the materials inside, prevent the bricks from rotting and keep the greenhouse gases stowed away. The uniform bricks each contain the equivalent of about 1.8 kilograms, or nearly 4 pounds, of carbon dioxide. The bricks will be stored at a former gravel mine — pending regulatory approval by state environmental authorities — where they will sit undisturbed for centuries. In that distant future, were some of the film and other barriers to break down, some of the carbon could return to the environment. By then, Nemet said, if carbon dioxide levels in the atmosphere have returned to pre-industrial amounts, humanity may no longer need a carbon removal industry.
After being dried, sawdust at Graphyte’s facility is transported on a conveyor belt. The rotary dryer, about the length of a tractor trailer, is seen in the background. Visual: Courtesy of Graphyte
Once pressed, the bricks are fed through a machine that encapsulates them in a thin film, which helps prevent rotting, thus locking the plant material’s carbon away. Graphyte aims to ramp up to a full capacity that would churn out around 90,000 bricks every day. Visual: Courtesy of Graphyte
Graphyte’s plant can so far store 15,000 metric tons of carbon annually, but the company aims to ramp up to a full capacity of 50,000 tons annually, which means churning out around 90,000 bricks every day.
According to consensus climate projections, humanity might need carbon removal until 2100 or later, but the company said it could keep the facility, as well as planned ones, running for decades without exhausting biomass sources.
“One of the nice things about our process, about carbon casting, is that it’s what we like to call biomass agnostic, meaning we don’t really care what type of biomass,” said Hannah Murnen, Graphyte’s chief technology officer. “Because we’re simply drying, densifying, and encapsulating, it doesn’t need to be a particular ash content or heating level or anything like that.” With the company’s current suppliers in Arkansas, she added, it already has up to half a million tons of biomass to work with every year.
People have researched carbon removal since at least the 1990s. But in the last couple of years, hype has ramped up and startups have popped up, in part due to a boost in funding.
Part of this recent shift may have come from the 2015 Paris climate agreement’s call to prevent global temperatures from rising by more than 1.5 Celsius, or temporarily overshooting it and then cooling down to safer levels, said David Keith, head of the Climate Systems Engineering initiative at the University of Chicago and lead author of a special IPCC report on carbon storage. An influential 2018 IPCC report laid out this scenario, which gave carbon removal a larger role than in others. “I think that did help to drive the talk about carbon removal,” he said, because at that point, startups and government agencies began arguing for 10 gigatons of carbon removal by 2050.
Researchers and companies are exploring several approaches, and each has pros and cons. Biomass carbon removal, like that at Graphyte, is relatively cheap and easy, and can store carbon indefinitely; the facilities involved can also have low carbon footprints.
Other biomass techniques are under development. Among them is a project by the startup Vaulted Deep, which has funding from Frontier, an initiative backed by major technology companies including Stripe, Alphabet, and Meta. Vaulted Deep’s idea is to inject a slurry of biomass, including different material than used by Graphyte, such as carbon-rich sewage and manure, into empty salt caverns of central Kansas. The caverns would store carbon that would have otherwise returned to the environment and released carbon dioxide and methane.
Their technology involves pumping through fissures in the ground and squirting the carbon-rich material thousands of feet down, beneath a rock layer that should be impermeable for centuries. “We use the same geologies that have kept hydrocarbons underground for millions of years,” said Julia Reichelstein, the company’s cofounder and CEO. Vaulted Deep staff describe it as similar to fracking, but without toxic chemical additives and without inducing earthquakes. Reichelstein said they plan to remove 30,000 tons of carbon over the next year, by May 2025. They’re endeavoring to soon expand and build more such facilities elsewhere in North America.
Other biomass efforts require less technology, such as reforestation — planting millions or more trees — and they’re also simple to deploy. Still, the method can be difficult to measure and monitor, and the storage can be vulnerable if, say, a wildfire wipes out a dedicated forest.
There are other approaches, too, each with different trade-offs. One such approach, called enhanced rock weathering, involves spreading finely ground silicate rocks, like basalt, on the ground or the ocean, which absorb carbon dioxide from the air as they weather in the rain. Here, side effects could include the erosion of silicate minerals into ecosystems or crops, in addition to the energy cost of mining, crushing, and transporting the rocks.
There are also contraptions that directly suck carbon dioxide from the atmosphere, which use chemical reactions to trap carbon dioxide from the air and release it in liquid or solid forms for storage or for other uses. Proponents point out that this has the benefit of removing greenhouse gases directly out of the air, where they’re currently warming the planet, and relevant research and development has received considerable commercial and government support, including tax incentives in the 2022 Inflation Reduction Act. But so far, the technology remains much too expensive, costing hundreds of dollars per ton, according to Sinéad Crotty, the director of the nonprofit Carbon Containment Lab.
There are other downsides. Some direct air capture technology, for instance, uses considerable amounts of water and energy. Researchers have also proposed various ways of extracting carbon dioxide from oceans, such as the California-based Equatic, which runs an electric current through seawater, separating it into hydrogen and oxygen and taking out the CO2, which is then stored as calcium carbonate. Such approaches remain hypothetical for now, as they’re at the research and development stage, or with a few pilot programs in the works.
Each approach comes with its own strengths, risks, and economics, making them difficult to compare, Crotty said. Ultimately though, she added, for any proposed response to the climate crisis, it comes down to one question: “Where is the lowest-hanging fruit where you can have the largest impact on climate as quickly as possible?”
If there are truly climate benefits from carbon removal projects, the proof will be slow to emerge. Even if one thousand large carbon removal facilities sprang up around the globe in an instant, it could take decades before they make a dent in global temperatures. “Carbon removal works well if you do it for a long time, but it’s not good for short-term cooling,” Keith said. That’s why, if humanity goes full bore into carbon removal, it has to be accompanied with aggressive, across-the-board emissions cutting right now, he argues.
Regardless of climate actions taken, annual global average temperature will likely reach 1.5 degrees Celsius above pre-industrial levels soon, possibly within the next five years. Then, depending on the world’s climate progress, it could subsequently exceed the dangerous 2-degree threshold in the 2040s, according to the IPCC’s 2023 report. If policymakers and the fossil fuel industry continue business as usual, even 2.5 degrees isn’t far off, coming as soon as a decade later. The majority of hundreds of climate scientists involved in IPCC reports expect global warming to reach 2.5 degrees or worse, according to a recent survey by The Guardian.
Or perhaps, industry leaders and policymakers will defy those bleak expectations. In a best-case scenario, temperatures could peak before reaching that 2-degree mark, but clearly such a shift means substantial economy — and industry-wide changes in a rather short time.
For this to play out, massively cutting carbon emissions across almost all industries is necessary but not sufficient, Keith said. Companies would need to converge on a few dominant designs — which may or may not look like what Graphyte and Vaulted Deep are doing — while relevant policies and regulations get worked out, said Nemet, the University of Wisconsin-Madison public affairs and low-carbon technologies researcher. This scenario would involve scaling up the industry to make up for some 10 to 15 percent of global carbon reductions, he said. But that would mean growing the industry’s impact by around 30 to 40 percent annually, every year, for the next quarter century.
That’s almost unprecedented, but the explosion of other nascent industries — including the solar and wind energy projects over the past two decades and the rapid growth of electric vehicles over the past few years — show that a massive expansion is possible, Nemet said.
Not everyone’s convinced by the hype. A brief report released by a United Nations panel last year had a mostly negative assessment of engineering-based carbon removal approaches, stating that they’re “technologically and economically unproven, especially at scale, and pose unknown environmental and social risks.”
The same panel gave much better marks to natural, or land-based carbon removal activities like reforestation and agroforestry, which incorporates trees in agricultural land use. Based on IPCC reports and other research, the U.N. experts state that those approaches have already been shown to be proven, safe, and cost-effective with economic, environmental, and social benefits.
These land-based approaches could quickly reach the necessary scale, and the techniques could account for 2.6 billion tons of annual carbon reductions by 2030, according to a 2017 study by Nature Conservancy researchers. Advocates of the approach include Campbell Moore, The Nature Conservancy’s managing director of carbon markets. “Most of nature’s made of carbon, more or less. Your average tree is going to be about 70 percent composed of carbon,” he said. “Through reforestation, protecting forests that are in danger, and improving the way we manage not just forests but also grasslands, wetlands, and agricultural lands, we can sequester and store additional carbon in the biomass of plants around the world.”
But land-based approaches haven’t received as much attention as engineering or technology-based approaches in recent years, for multiple reasons. The effectively permanent storage of carbon that companies like Graphyte and Vaulted Deep claim to provide is a major advantage, while a forest or grassland might burn in a fire tomorrow, as all those no-longer-stored greenhouse gases go up in flames.
The precise amount of carbon is easily measured — for Graphyte, it’s brick by brick — but a carbon accounting for natural climate solutions, like reducing deforestation, is no simple endeavor. Furthermore, many of those engineering-based activities have the support of prominent Silicon Valley and Wall Street figures, who stand to profit if the carbon removal industry flourishes, while the benefits of nature-based activities are scattered across the Global South, Campbell said.
Despite the challenges and the initial costs, carbon removal startups and their backers are plowing ahead, hoping that the industry can make a major impact. Estimates suggest that technology-based carbon removal outfits extracted anywhere from 10,000 to more than a million tons of carbon dioxide in 2023, compared to more than 37 billion tons of global emissions. Within a few years, Graphyte would need to expand, open new facilities, and find reliable customers, while removing the equivalent of hundreds of thousands of tons of carbon dioxide annually. And many, many of its peers would have to do the same.
For the formative industry to actually matter to global climate change, it will have to remove up to 10 billion tons every year in the not-too-distant future. Since companies are now at the scale of just tens of thousands per year, the industry is nowhere close to reaching even a tiny fraction of that extremely ambitious target, according to the State of Carbon Dioxide Removal report, released on June 4 by an international team of researchers that includes Nemet. Even at today’s early stage, those researchers found, there’s already a gap between proposed levels of carbon removal and what’s needed to meet the Paris Agreement temperature goal.
In order to make things work economically, the carbon removal industry is relying on the market for carbon credits. For decades, that market has been based on carbon offsets, where companies and individuals seek to offset their own carbon emissions by paying to fund forest protection projects and other climate-friendly initiatives around the world. The idea is that each ton of carbon emitted by a particular plane flight, for instance, can be counterbalanced by a ton of carbon saved by a particular forest, and carbon offset groups have sought to be the intermediaries arranging that balance.
But carbon offset projects have a poor record, and examples of their failures abound.
A 2023 study in Science was particularly revealing about the impacts of carbon offsets. The authors examined 27 forest projects in South American countries, central African countries, and Cambodia. The researchers compared each forest to reference areas that were not protected, and they used remote sensing by satellites to track forest cover. They came to a damning conclusion: Most projects did not significantly reduce deforestation at all — and thus had negligible impact on carbon removal. For the minority that did, they reduced much less than they claimed.
“I definitely still believe that forests can be part of the solution for mitigating climate change,” said Erin Sills, a North Carolina State University forest economist and study coauthor. But, she added, buyers in the carbon credit market can’t definitively claim that they’ve offset their carbon emissions.
Assessments like this have accumulated, leading to widespread critiques of carbon offsets and to more demand for clearly measurable and accountable carbon removal projects — a demand that companies like Graphyte and Vaulted Deep seek to satisfy with their engineering-based approaches. Many of these companies launch through a major initial investment, such as by Stripe-subsidiary Frontier or Bill Gates’s Breakthrough Energy Ventures or by the federal government’s Bipartisan Infrastructure Law. After that seed funding dries up, the companies transition to a business model based on carbon credits, in the hopes of selling enough credits to continue operating and quickly scale up. In Vaulted’s case, Frontier, along with Rubicon Carbon, count among the company’s first carbon credit customers, rather than seed funders. Advocates like Graphyte’s Rogers want to ensure the market for carbon removal credits avoids the problems and scandals that have plagued the carbon offset market.
The U.S. Department of Energy has stated a goal of seeing carbon credit prices below $100 per metric ton. That number has become a commonly used threshold, Crotty said. At the same time, she added, companies need to be able to clearly and precisely measure and report how much carbon they’re storing.
The market is built on the conceit that companies won’t simply continue carbon-guzzling business as usual while paying for a few credits, but will instead voluntarily decarbonize what they can and use carbon credits for what they can’t decarbonize, Moore said.
He pointed to a study last October by Ecosystem Marketplace, a Washington D.C.-based nonprofit, which found that companies engaged in the voluntary carbon market are 1.8 times more likely to be decarbonizing than their peers and investing three times more money in their internal decarbonization. “The specter of greenwashing that we’re all worried about, at a system level, is not a huge concern today,” he said. Still, the industry needs “very clear rules” so that it doesn’t become a problem as the market grows, he added.
Some suggested rules have begun to emerge, Moore said, such as the international Voluntary Carbon Markets Integrity Initiative, or VCMI, which proposes guidelines, such as for reporting carbon credits and progress toward decarbonization. The U.S. Department of Energy has guidelines for recipients of its grants as well, including accounting for environmental justice concerns, so that carbon removal projects don’t adversely affect communities living in the area. The Biden administration also announced new guidelines at the end of May to support “high-integrity” voluntary carbon markets and to ensure that they “drive ambitious and credible climate action and generate economic opportunity.” These include monitoring, measurement, reporting, and verification protocols on the supply side, so that one credit really means a metric ton of carbon removed. On the demand side, credit purchasers should publicly disclose the kind of credits they’ve bought and which ones are retired credits, where the benefits have taken place, to prevent double-counting.
None of the guidelines are binding or enforceable, however, and other experts like Keith believe much more will be needed. “I think all this voluntary stuff and companies claiming to be green is basically greenwashing crap,” he said. For a better model, he cites the Clean Air Act, developed during the rise of the environmental movement in the 1960s and ’70s, as that law forced companies to reduce their air pollution emissions, such as of nitrogen dioxide and carbon monoxide. But most greenhouse gas emissions were not among them.
An even bigger question looms over carbon removal efforts, which some researchers refer to as a “moral hazard” — the worry that all this attention and investment in a technofix could discourage people from the hard decarbonization work that needs to happen throughout the energy sector, transportation, agriculture, and other industries.
“Maybe voters or governments will back off on cutting emissions if there seem to be alternatives? I think the answer to that is that it might be true. It’s a real concern,” Keith said. “But I do not believe it is an ethically sound reason not to work on these things.”
For example, he cites an argument that some people drive more dangerously when they have seat belts and airbags, but that’s not a justification for not equipping cars with them. Endeavoring to drive safely — and to decarbonize industries — needs to be the focus, but airbags and seat belts are important too, and they’re still saving lives.
That gives Sinéad Crotty, the Carbon Containment Lab researcher, optimism, as she surveys the industry. Approaches like Graphyte’s nondescript beige blocks seem to be effective at preventing greenhouse gasses that would otherwise go into the atmosphere, and there seem to be multiple sustainable sources for such biomass too, she argues. And since carbon credit-purchasing companies actually do seem to be making some, albeit slow, progress toward net-zero, it means there’s indeed demand for locking away tons and tons of carbon to get humanity on a path toward limited global warming.
“My feeling is that the next five years will be important for building credibility, separating the bogus from the high-quality credits, and that’s the time when we will see what demand there actually is,” she said. “But right now we’re still building it.”
