The invention of synthetic fertilizer made it possible to feed billions of people. It also caused some unintended problems: Making fertilizer from fossil fuels is now responsible for more than 20% of agriculture’s huge carbon footprint, and fertilizer that washes off fields pollutes water and causes dead zones in the ocean.
Synthetic fertilizer factories use large amounts of energy and require a supply of natural gas, which they use to make ammonia, another form of nitrogen. Kula Bio, a startup that spun out of research at Harvard, recently raised $50 million to help bring an alternative product to market—fertilizer that uses microbes, instead of fossil fuels, to give plants the nitrogen they need to grow quickly. “It’s bacteria that is naturally occurring, and it has the capability to grab nitrogen from the air,” says Bill Brady, founding CEO and director of Kula Bio.
Ordinarily, the bacteria that Kula Bio uses would only live for hours. But Kula uses a process developed by Harvard energy professor Daniel Nocera to make them live for more than two weeks so they can capture far more nitrogen for crops. The company starts by growing the microbes in a bioreactor, so as many as possible are in a liter of its fertilizer, feeding them a nutritional mix. Then it cuts off the food source. “Because they’re under stress and they sense that they don’t have any more food, they start to store and hoard energy,” Brady says. “So they grab carbon, hydrogen, and oxygen and start to produce this energy-storing material in their cell structure.” That helps the microbes last in the field.
Farmers spray the mix onto crops in the same way they’d use synthetic fertilizer. The typical process can cause fertilizer to run off fields because farmers spray large amounts at once, and plants can’t use all of it; if it rains, fertilizer ends up washing into nearby streams and rivers. But the microbes produce nitrogen on demand. “As they sense a deficit of nitrogen in the soil around them, the mechanism to fix nitrogen will kick in,” he says. “When they sent an abundance of nitrogen around them, they will shut down that mechanism.”
The microbes also capture carbon, and when they die, that carbon stays in the soil, helping make the soil healthier. That also helps the product’s carbon footprint: The company hasn’t completed a lifecycle analysis yet, but Brady says that it’s likely to be carbon neutral or even carbon negative. It can be used anywhere, on any crop, unlike a product from another startup, Pivot Bio, which tailors microbes for particular plants. Kula is also getting organic certification so it can be used on organic farms.
The product can replace up to 80% of a farm’s use of synthetic fertilizer now, and eventually should be able to replace it fully. For now, a farmer who applies fertilizer twice a year might spray once with Kula Bio, and once with synthetic fertilizer. The company has run trials on several farms, and says that it’s a realistic change for farmers to make.
“When we started the company, we contacted 600 farmers,” Brady says. “We got a lot of feedback on the product and the idea, and the farmers told us three things. Number one, I’m not going to pay you any more money. Number two, I’m not going to change my practices. And number three, I’m not going to spend a lot of money on new capital equipment, right? So we love your idea, we would love to use it. But you know, let’s be clear, you got to fit in those parameters. And so we designed the product based on that.”
The startup is scaling up to begin manufacturing, which will happen in a decentralized way near farmers, in part because the product doesn’t have a long shelf life. Ultimately, Brady believes that it will be possible to completely replace synthetic fertilizer. “Farmers will do it if it works, and if it’s cost competitive,” he says. “They will do it because it helps them and helps their biggest asset, which is their soil.”