Part of the climate challenge isn\u2019t just the transition to things like renewable energy and electric cars\u2014it\u2019s also about dealing with the oversupply of CO2 that\u2019s already in the Earth\u2019s atmosphere. By the middle of the century, by one estimate, the world may need to be pulling 10 billion<\/a> 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.<\/p>\n\n\n\n That\u2019s sparked the growth of \u201cnegative emissions\u201d technology. Direct air capture<\/a> startups, with machines that pull CO2 from the air, are being backed by companies like United Airlines<\/a>. Capitalizing on trees\u2019 ability to function as natural carbon capture machines, Reddit\u2019s former CEO is now running a company that restores forests<\/a> on degraded land (and recently raised $30 million in a Series A round of funding). Dozens of other companies are experimenting with farming seaweed<\/a>, regenerative agriculture<\/a>, and techniques like spreading crushed rock on the ground<\/a>. And in the Bay Area, a company called Living Carbon<\/a> 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.<\/p>\n\n\n\n \u201cPlanting trees alone is definitely helpful,\u201d says Patrick Mellor, cofounder and chief technology officer at Living Carbon. \u201cBut 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.\u201d<\/p>\n\n\n\n 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. \u201cWhat can you do so instead of planting 1 trillion trees, you only have to plant, you know, 500 billion?\u201d says Maddie Hall, the company\u2019s cofounder and CEO. \u201cThen you have a lot more acreage available for other things.\u201d<\/p>\n\n\n\n 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, \u201chas been working for years with various collaborators to see if we can tweak photosynthesis,\u201d says Steve Strauss, a professor of forest biotechnology at Oregon State University who is advising the startup and collaborating on research. \u201cIt is really hard to do. It\u2019s 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\u2019s really hard. Nature, of course, has been trying to do this for thousands of years, so you\u2019re trying to improve on that.\u201d (The potential harm, Strauss says, is that the trees might be more susceptible to stress and thus less healthy.)<\/p>\n\n\n\n Ort\u2019s 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<\/a> 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.)<\/p>\n\n\n\n Planted at a large scale, the trees could make a difference. \u201cIf 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,\u201d Mellor contends. \u201cImproved photosynthesis, deployed in managed forests at a large scale, has the potential to get additional gigatons of drawdown over the current quantities.\u201d<\/p>\n\n\n\n