Living Carbon: Photosynthesis-Enhanced Trees
Why and how to engineer trees; climate biotech business strategy
Welcome (back) to The Century of Biology! This newsletter explores data, companies, and ideas from the frontier of biology. You can subscribe for free to have the next post delivered to your inbox:
During my summer hiatus, I made a lot of progress on my research, and started to lay the foundation for what will follow. I’ll be excited to share more on both fronts in the coming months.
For now, let’s celebrate the autumnal equinox with a story about the power of plants.
Enjoy! 🧬
As the Chief of Staff at OpenAI, Maddie Hall learned an important lesson firsthand: a small team of mission-driven researchers can turn science fiction into science fact on an extremely short timescale.
For decades, AI was a backwater academic discipline thought to be chasing a pipe dream—until it wasn’t. Now it’s a major driver of the economy.
Maddie remembers a colleague recommending her Profiles of the Future by Arthur C. Clarke. Written by a prolific science fiction author with an uncanny track record of future predictions—including telecommunication satellites and the Internet, to name a few—the book was an exercise in thinking big. It was also a reminder that even the best futurists didn’t see everything coming.
Observing the company’s rapid internal progress, Maddie constructed a new prediction problem for herself. Assume ubiquitous AI. What extremely important problems still wouldn’t be solved?
Probably messy problems rooted in the physical world. And which of these problems might have existential consequences if it remains unsolved?
Climate change.
After exhaustively researching options for making a planetary scale impact on atmospheric carbon levels, Maddie settled on her approach: engineering biology.
So in 2019, Maddie left OpenAI and co-founded Living Carbon, Public Benefit Corporation (PBC). In just five years, Living Carbon has developed photosynthesis-enhanced trees using biotechnology, planted hundreds of thousands of trees in four different states in the U.S., built out an experienced carbon project development team, and raised over $36M from leading investors including Temasek, Lowercarbon Capital, Toyota Ventures, Day One Ventures, and Felicis Ventures.1
Let’s explore why they are doing this, how they are doing it, and how the business model of a climate biotech works in practice.
A Journey Into Deep Time
In 2024, artificial neural networks (ANNs) need little introduction. They are the core algorithmic unit underpinning self-driving cars and AI chatbots. But twenty years ago, the idea that ANNs would be a promising path towards developing learning machines was obvious to few very people. Yann LeCun was one of them.
One of the core tenets of LeCun’s belief in ANNs was a simple existence proof: biological organisms—including humans—use neural networks to learn new things every day. If we could scale computational versions of these types of “deep” networks, they should be able to learn increasingly rich representations of the world.
He was right. In 2018, he shared the Turing Award with Yoshua Bengio and Geoffrey Hinton for his contributions to deep learning. But even at this stage, few people truly internalized the importance of continuing to massively expand the scale of these networks.
OpenAI emerged as one of the teams most zealously committed to this idea. For years, they had been pouring an outsized portion of their resources into compute for training bigger and bigger neural networks. As the size grew, performance continued to improve. Just think of the difference between the first GPT in 2018—which was interesting but not particularly useful—and GPT-4, which can solve challenging engineering problems with very minimal prompting.
OpenAI was able to make this non-obvious investment because they are a research-first company. Their first breakout product came years after their inception. Before they rocketed past $3B in revenue, they had a simpler selling point to prospective researchers: a mission.
Researchers could choose between staying in academia and testing new ideas at a small scale, joining a company to work on an applied machine learning team, or joining an industrial research lab like OpenAI that was entirely dedicated to achieving the full vision of Artificial General Intelligence (AGI).
Many of the most talented researchers in the field—who were also the biggest believers in the vision of AGI—chose the latter. The centrality of this massive vision played an important role in achieving early talent density and justifying continued R&D investment.
Maddie took this to heart. She observed a parallel in a different field: plant biotechnology. Academic scientists were achieving amazing results using synthetic biology to rewire photosynthetic pathways in plants, but their work would never be translated out of field trials. Companies that were pursuing translational work were mainly large corporations plugging away at making better crops.
What if there was a “third place” for the most talented plant biotechnologists to work on their actual mission? The type of place where they could do their life’s work. Where the most cutting-edge techniques could be used to mitigate the looming climate crisis.
Living Carbon was founded to be this third place.
Much like LeCun’s early research, the company is based on an existence proof. But it isn’t based on something that can be directly observed. It requires a journey backwards into Deep Time—a central obsession of Patrick Mellor, Maddie’s co-founder.
The story starts 4.5 billion years ago (4.5G) at the Earth’s formation:
A billion years after the Earth was hit by a protoplanet the size of Mars—ultimately forming the Moon and establishing tides in the ocean—the first major terraforming event occurred: Evolution gave rise to the first photosynthetic microbes.
The result was extreme. These microbes pumped out enormous volumes of oxygen as a byproduct of photosynthesis, which eliminated nearly all anaerobic life forms. The oxygen also converted methane into CO2, which is worse at blocking heat from escaping the atmosphere.
This triggered our planet’s first ice age. All because of photosynthesis.
Across several billion more years, the Earth’s climate continued to be shaped by evolutionary advances in photosynthesis. The emergence of seaweed froze the entire planet. Photosynthesis. Organisms emerged to eat the seaweed. Terrestrial plants emerge and trigger another ice age. Photosynthesis. Again and again.
Living Carbon draws the following conclusion:
“Every major ice age over geological history has been triggered by an evolution in photosynthesis.”
So, what is the plan of action?
Starting with fire and leading to our industrial revolution, humans are the first species to release carbon stored outside our bodies over deep time, as only volcanic eruptions have before. However, unlike a volcano, we have the capacity to do something about it. We could be the first organism to intentionally rebalance the effects of our own success.
We can learn from deep time how every major ice age has been triggered by plants. The current crisis can lead humans to work with plants to accelerate photosynthesis, sequester carbon, and preserve the biosphere on which we both depend.
If we do this successfully, we will be the first species on Earth to intentionally instantiate metabolism on a planetary scale.
AGI is a really big vision.
But so is rebalancing our climate by engineering another major evolutionary event for photosynthesis.
And so far, the vision seems to be resonating. I asked their Chief Science Officer, biotech veteran Yumin Tao, why he joined. He told me, “If I could finish my career making this type of impact on the climate, it would be incredible.”
Living Carbon has recruited a scientific team full of PhD plant scientists, ecologists, and synthetic biologists with decades of experience in the domains needed to tackle this problem.
Let’s explore their early results.
Tree Engineering
Photosynthesis is absolutely miraculous. It is a process carried out by genetically encoded nano-scale machines that organisms—microbes and plants—use to convert light and atmospheric carbon into organic matter that can fuel their growth.
Collectively, terrestrial and oceanic photosynthetic organisms convert over 100 billion tons of carbon into biomass every year.2 Every year!
This is worth restating. Biomass is the direct consequence of atmospheric carbon capture.
In theory, if we could double the speed of this process, we’d be doubling the amount of carbon that photosynthetic organisms are sucking out of the atmosphere.
A lot of research has gone into accelerating photosynthesis—primarily motivated by accelerating crop growth. One of the major strategies has been to increase the efficiency of the RuBisCO enzyme, which is responsible for catalyzing the reaction that fixes CO2. RuBisCO is the most abundant enzyme on the planet, but it’s also one of the slowest.
Tinkering with RuBisCO has proved to be a daunting challenge. Evolution has been trying this for billions of years and hasn’t had much luck either.
In 2019, researchers from the University of Illinois published promising results based on an alternative strategy. Instead of worrying about RuBisCO’s catalytic efficiency, the goal was to circumvent photorespiration—where the enzyme binds to oxygen rather than CO2—which emits CO2 (and uses energy) rather than accumulating it.
Testing a variety of approaches, the group from Illinois identified an alternative pathway (AP3) that consisted of two genes and one RNAi molecule in total. The two genes encode enzymes that convert the byproduct (glycolate) back into C02 inside of the chloroplast. The RNAi, on the other hand, blocks the transporter (PLGG1) that shuttles glycolate out of the chloroplast.
The idea is to convert unwanted byproducts back into CO2—all inside of the chloroplast—giving RuBisCO another chance to fix carbon.
In field trials, this pathway increased the biomass of tobacco crops by 28% and increased photosynthetic yields (measured by starch accumulation) by more than 40%.
Instead of crops, what if we could achieve the same type of photosynthesis enhancement in trees? Sticking to our earlier logic, any new reforestation effort would be removing 40% more CO2 from the atmosphere!
This is what Living Carbon set out to do—and it seems to be working.
Only three years after being founded, the company posted a preprint on bioRxiv describing the creation of poplar trees engineered to bypass photorespiration. Some of the engineered trees accumulated up to 53% more biomass in growth room experiments—an even bigger increase than previous efforts. A year later, the paper was accepted in Forestry.
The results are fairly easy to interpret: the engineered trees get bigger faster!
One major question about these results was how well they would stand up in field experiments—the plant science equivalent of translating in vitro pre-clinical results into actual demonstrable benefits. So far, that is going well too. They’ve launched multiple field trials in different locations, and their collaborators have already seen positive results in the field. Living Carbon will have more exciting news to share on this front soon.
Another major question is whether faster growing trees directly correlate with durable carbon sequestration. Nature operates with cycles. Plants draw down carbon, but their respiration—and ultimately, death—causes a lot of that same carbon to end up back in the atmosphere. This is called the fast carbon cycle.
Reducing respiration should make Living Carbon’s trees tip this cycle towards more carbon capture than emission, but they aren’t stopping there. In parallel, Living Carbon is engineering trees capable of accumulating an order of magnitude more copper through their roots. Copper helps to block fungal infections and slows down wood decay—ideally lengthening the time carbon remains captured.
But ultimately, these two traits are just the start. Living Carbon is a platform company. The scientific team has built out the capabilities to identify traits, develop genetic constructs (now focused on gene-editing technologies), transform a wide variety of plant species, and to quickly move from the greenhouse into the field.
Let’s recap. Inspired by her time at OpenAI, Maddie co-founded a research-centric company focused on a massive mission. The goal was to attract the talent and resources necessary to compress the time needed to solve a hard problem. In three years, Living Carbon genetically engineered a tree that accumulates over 50% more biomass.
That’s an exciting start. But like OpenAI, the company is growing a viable commercial organization around its research-centric core.
In other words, getting this right will require a marriage of tree engineering and financial engineering.
Financial Engineering
Sometimes capitalism is portrayed as a mindless sprawling machine that destroys Nature while siphoning wealth into the hands of a select few. But this is a caricature. In reality, it’s just a collective story that we tell each other to collaborate. When the story causes problems, we can change it. It’s not easy, but it’s possible.
This is what carbon credits aim to do.
One problem with capitalism is that it’s hard to measure and price in negative externalities. Try drawing the exact causal link between an oil refinery and the specific economic consequences of its emissions in the future.
Proponents of carbon credits argue we should use financial engineering—specifically, the development of new financial instruments and markets—to solve this problem. Carbon credits are a mechanism for people and corporations to invest in projects that offset emissions through the reduction, avoidance, or removal of carbon.
Starting new markets and measuring offsets are both hard problems. Last year, a team of journalists reported that more than 90% of carbon offsets large companies are purchasing to prevent deforestation are effectively worthless. In response to the study, a scientist at Oxford made the following point: “The challenge isn’t around measuring carbon stocks; it’s about reliably forecasting the future.”
How much of an impact does not cutting down a tree actually make?
As carbon markets continue to grow and develop better standards, we need new categories of interventions with more directly measurable benefits. This is what Living Carbon hopes to deliver.
Rather than preventing deforestation, Living Carbon focuses on reforestation efforts, specifically on land that has been degraded and is sitting idle. With their enhanced trees, they aim to convert decimated land—like old mining sites in Ohio—into rapidly growing forests demonstrably sucking carbon out of the atmosphere.
Achieving this is a two-sided problem. In the middle, there is Living Carbon’s growing suite of enhanced trees and their field team capable of delivering “Projects as a Service” (PaaS).
One one side, there are landowners. The pitch to the owners is that instead of donating their land to a trust or investing in reforestation themselves, Living Carbon will convert their idle acres into a valuable resource, generating meaningful revenue per acre annually.
On the other side, there are corporations looking for more effective carbon offsets to purchase. The pitch to the companies is that Living Carbon’s reforestation projects will produce high quality removal offsets that can be directly measured and verified.
To repeatably establish these types of projects, the company has built out a commercial team with backgrounds in project development, carbon markets, and real estate. Each project produces three types of revenue:
Carbon credits
Seedling sales
Contract value for PaaS
Part of what’s unique about Living Carbon is how quickly they’ve put this strategy into action. They’ve raced past other GMO tree projects in terms of real-world data collection, becoming the first group to plant multi-site, multi-year field trials of genetically modified trees last year.
If some of the large-scale projects they are currently negotiating come into fruition, Living Carbon could become one of the early leaders in the carbon market.
But there’s another commercial benefit for Living Carbon: trees have value beyond carbon markets. Unlike most of synthetic biology—where engineered organisms are used to produce products like chemicals or proteins—their engineered organisms are the product.
As Maddie puts it, “At the end of the day, we are selling biomass.”
This biomass can be monetized via carbon markets, where the sole purpose of the trees is to sequester carbon. Fast-growing trees capable of growing on previously idle land is also of obvious interest to timber companies. Woody biomass can also be sold as feedstock to producers of biomass-based electricity and sustainable aviation fuels (SAF).
So the business model generalizes to:
Biomass (sold for carbon credits, timber, feedstock for SAF, etc.)
Seedling sales
Contract value for PaaS
Given how nascent carbon markets are, this offers them flexibility to expand their business in multiple directions.
To make all of this work, the team sweats the details of their techno-economic analyses. They are exploring new corporate structures—much like hub and spoke biotechs—to finance the upfront costs of their project with loans rather than venture dollars.
As Maddie told me, “We don’t want to just be a feel good climate startup.” The goal is to build a real business that makes a planetary scale impact on the climate.
Achieving an impact on this scale will require fast-growing trees, and a fast-growing business to sustain the research and mission.
Over two years ago now, I wrote an essay entitled Viriditas, outlining why I care so much about biotechnology. Part of my argument was that we need to remember that AGI won’t solve all of our problems:
Perhaps it is myopic, but there is something special about biological life. About the prospect of more green, wet planets in the universe. The chaos and complexity of evolved cellular machinery. I’m arguing that if AGI is a rocket ship with any chance of launching sentient life into the Cosmos, something deeply important and beautiful would be missing if it weren’t launching biological organisms.
The digital realm is increasingly created unconsciously. Most code may soon be written by unconscious AI agents. As a programmer, I’m still working to adjust to this new reality. Imagine a future where AI realtors and lawyers negotiate with each other, and AI stock pickers reach out to their AI brokers.
Many wonder and worry: where will I be in this AI future? Where will my meaning and value come from?
People that are feeling this way should consider looking where Maddie looked: the physical world. Achieving the type of verdant and abundant future most people really want will require a modern renaissance of artisanship and engineering in the world of atoms.
This future will require real human blood, sweat, and tears—supplemented by AI advances—and continued progress in bioengineering.
Part of what I find compelling about Living Carbon is that the innovation is equal parts scientific and cultural. The company is founded around a mission that puts biologists—and the trees they engineer—at center stage in the story we tell ourselves about the future.
They are forcing the issue. If we want our planet to remain hospitable to humans, we need to start planting seeds of change now.
Thanks for reading this essay about Living Carbon’s efforts to rebalance our planet’s carbon cycle with plants.
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Until next time! 🧬
Not all of the planted trees are genetically engineered. The company has planted 12 species in their forests, including a percentage of their engineered poplars to serve as multi-year, multi-site field trials. The goal is to increase the percentage of engineered trees planted over time as they accumulate more evidence in the field.
Interesting read, and the science behind it is really cool, but this project totally overlooks the importance of conserving biodiversity. Reforestation is awesome, but planting monocultures instead of native species would surely impact the local ecology. I think synthetic biology should be used to reduce the space humans need for a good quality of life, giving as much land back to the planet as possible. If we've got disused sites, we should be rewilding them/letting them naturally regenerate.
Super hopeful article! How do these trees allow for biodiversity?