Part of the climate challenge isn’t just the transition to things like renewable energy and electric cars—it’s also about dealing with the oversupply of CO2 that’s already in the Earth’s atmosphere. By the middle of the century, by one estimate, the world may need to be pulling 10 billion metric tons of carbon dioxide from the atmosphere every year to be able to meet the goals of the Paris climate agreement. By the end of the century, that number could double to 20 billion tons per year.
That’s sparked the growth of “negative emissions” technology. Direct air capture startups, with machines that pull CO2 from the air, are being backed by companies like United Airlines. Capitalizing on trees’ ability to function as natural carbon capture machines, Reddit’s former CEO is now running a company that restores forests on degraded land (and recently raised $30 million in a Series A round of funding). Dozens of other companies are experimenting with farming seaweed, regenerative agriculture, and techniques like spreading crushed rock on the ground. And in the Bay Area, a company called Living Carbon is engineering trees that can capture and store more carbon than typical trees. The startup recently completed a stint at the prestigious tech accelerator Y Combinator.
“Planting trees alone is definitely helpful,” says Patrick Mellor, cofounder and chief technology officer at Living Carbon. “But any way that we can improve the total drawdown of carbon dioxide from photosynthesis, and also improve retention of that carbon, are ways to quite greatly increase the total drawdown potential of trees.”
If a forest can sequester more carbon than it otherwise would have, it also can help with the challenge of finding enough land for planting trees without competing with other uses such as agriculture. “What can you do so instead of planting 1 trillion trees, you only have to plant, you know, 500 billion?” says Maddie Hall, the company’s cofounder and CEO. “Then you have a lot more acreage available for other things.”
The company plans to share more details about the technology later in the year, but it builds on previous research, including years of work from other scientists looking at how to enhance photosynthesis in other plants. Donald Ort, a scientist at the University of Illinois, “has been working for years with various collaborators to see if we can tweak photosynthesis,” says Steve Strauss, a professor of forest biotechnology at Oregon State University who is advising the startup and collaborating on research. “It is really hard to do. It’s a result of millions of dollars and decades of work trying to do this in a way where you do more good than harm, and most of the experiments have failed, because it’s really hard. Nature, of course, has been trying to do this for thousands of years, so you’re trying to improve on that.” (The potential harm, Strauss says, is that the trees might be more susceptible to stress and thus less healthy.)
Ort’s team focuses on tobacco, and in experiments has found that tweaking an enzyme in the plant could make it grow as much as 40% bigger than ordinary tobacco plants. For food crops, this type of photosynthesis hack could potentially help meet increased demand for food as the global population grows. For a tree, faster growth means that it can take up more CO2. Living Carbon is also developing a second innovation for the trees that slows the rate that the tree decomposes; the process will enable trees to take up copper and nickel, which act as fungicides. (Fungi speed the decomposition of wood, leading to loss of CO2.)
Planted at a large scale, the trees could make a difference. “If we could increase the drawdown potential of managed forests by 20% to 30%, and we can also increase the [CO2] retention by some similar value to that, we have made a large difference in terms of the total possible drawdown from those forests,” Mellor contends. “Improved photosynthesis, deployed in managed forests at a large scale, has the potential to get additional gigatons of drawdown over the current quantities.”
As has been the case with other genetically engineered plants, Living Carbon’s trees may face some challenges gaining acceptance. The company’s process, at least for some trees, means that the U.S. Department of Agriculture won’t designate the trees as GMOs; the USDA only regulates plants modified with so-called plant pests. But the Forest Stewardship Council, which certifies forests as “responsibly” managed and doesn’t allow any genetically modified trees in the forests it approves, may classify the trees differently. (Hall and Mellor wouldn’t comment on this, saying that they’re focused on their research efforts at the moment; they also note that the type of tree that they’re working with now, a poplar-aspen hybrid, can only reproduce via cuttings, and doesn’t produce pollen that could spread elsewhere, one of the issues that anti-GMO activists sometimes raise.)
Strauss argues that prevailing attitudes about genetic engineering are holding back other innovations that could also be critical now, such as helping trees survive changing conditions because of the climate crisis. “Why is the United States of America so retrograde when it comes to biotech?” he asks. “Given the challenges, we should be testing heat tolerance in trees in the ground as we get hotter and hotter. And drought tolerance. There’s all kinds of promising genes that we could be testing and essentially almost none of that’s going on.” The U.S. government should be funding this research, he says—not just Silicon Valley.
Correction: This article has been updated to note that the trees can produce seeds, they cannot produce pollen to fertilize those seeds.