These probiotics for plants help farms suck up extra carbon dioxide

On thousands of acres of orange groves in Florida, farmers are adding beneficial fungi and bacteria to the soil, which makes the oranges grow bigger and sweeter–and makes the soil suck up enough extra CO2 so that each acre offsets the emissions from a passenger car. Call it probiotics for soil.

“Agricultural soils are one of the world’s largest carbon sinks,” says Paul Zorner, CEO of Locus Agricultural Solutions, the startup that makes the particular combination of probiotics in use on the farms. “If they’re treated right, you’re going to absorb a lot of carbon dioxide out of the atmosphere.”

Unlike the ocean, which has absorbed the brunt of human emissions so far–becoming more acidic and hotter and threatening marine life as that happens–soil can benefit from extra carbon. “Soil is the exact opposite,” Zorner says. “Soil actually enriches its productivity when you’re sequestering carbon, and so the soil and crop and ultimately the growers benefit by sucking as much CO2 from the atmosphere to the plant into the soil as possible.”
When plants take up CO2 during photosynthesis, creating sugar that they use for growth, they also release sugars through their roots, attracting microbes. Healthy soil is full of these microbes, which then keep the carbon in the ground. But conventional farming–including the overapplication of chemical fertilizer–has destroyed the microbial balance. Adding “probiotics” helps restore it.

Other companies also sell microbes, though Locus is selling a particular combination (Trichoderma harzianum, a beneficial fungus, and Bacillus amyloliquefaciens, a beneficial bacteria) and using a unique production system that delivers the microbes fresh and at a high density. “We decided to create what I often refer to as a microbrewery for agriculture, where we build facilities that are local,” Zorner says.
The facilities are smaller than a beer brewery; the fermentation devices are small, and in a space roughly the size of a conference room, the company can produce enough of its product for 30,000 acres of farms a month. The microbes are applied while the field is irrigated or just spread on the surface. The first production system is in Cleveland, though the company plans to begin building them locally near farms across the country. “One of the key features of this local microbrewery is we can actually optimize for local conditions–soil type, crop, temperature, a whole variety of things–where we can work with individual growers to better understand how to solve their specific problems, as opposed to just having one product that would be used the same, regardless of where in the country you’re trying to operate,” he says. Eventually, it could also be produced in parts of the developing world. “It’s a system that could be shipped in a boxcar and set up relatively easily, as long as you have a basic power source.”

The company started working in Florida, where it’s currently being used on 32,000 acres, because of the particular challenges of citrus growers, who have been struggling with massive drops in production due to citrus diseases and hurricanes. The product, called “Rhizolizer,” increases production; on one 38-acre orange grove where the company tested it last year, the grove saw a 14% increase in yields by weight. Other tests showed that it increases “brix,” a measure of sweetness, in fruit like oranges and strawberries. For farmers, the immediate benefit may be better sales. But there are longer-term benefits for the climate. In another 2018 test at a different Florida orange grove, the part of the farm treated with the product took up an extra 4.38 metric tons of CO2 per acre. Farmers could eventually be paid in the form of carbon credits for making the change; Locus is working on the first steps to try to make it possible to sell this service in carbon markets.
“I think people are really waking up to the fact that agricultural soils really are a remarkable part of the solution [to climate change],” says Zorner. “We need to empower growers to do this.”