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How a biofriendly fertilizer could offer a greener way to grow plants

Invented in 2018, the biofriendly fertilizer relies on an engineered cyanobacteria called Xanthobacter autotrophicus. The invention incorporates years of research, going back to Nocera’s artificial leaf technology, which splits water to make hydrogen and oxygen, performing photosynthesis better than any leaf.

The new treatment uses the hydrogen from water splitting and combines it with nitrogen in air to produce ammonia, which plants can absorb into their roots. Since inorganic and organic fertilizers often give plants more nitrogen and phosphorous than they can use at one time, the excess gets washed away. But the biofertilizer stays safe within the plants’ roots, stored for future use.

The innovation has another ecofriendly trick: The bacteria absorb carbon dioxide from the air. “Using the new biofertilizer methods across the U.S., we could remove significant amounts of COper year by sequestering the carbon in the soil,” Dogutan said.

With the help of the Office of Technology Development, Nocera, Pamela Silver, the Elliot T. and Onie H. Adams Professor of Biochemistry and Systems Biology at Harvard Medical School, and Xiaowen Feng, a former member of her lab, founded a company called Kula Bio, which arranged a first field test off campus. Marching toward commercialization, Kula Bio hopes its product will replace all synthetic nitrogen fertilizers — those responsible for high levels of runoff and CO2 emissions — with a low-cost organic biofertilizer.

On campus, with funding from the PAIF, Dogutan and her team will perform large-scale tests of the fertilizer from winter 2020 through the following fall. But, with an earlier grant from the Campus Sustainability Innovation Fund, she has already planted two small test plots. In one, she and Daniel Loh, a Ph.D. student in the Department of Chemistry at the Graduate School of Arts and Sciences and a member of the Nocera Lab, cleared two parking spot-size gardens with a two-foot grass buffer between. Loh planted radishes, turnips, and spinach in each. Then, every week, he fertilized one with 100 milliliters of the engineered cyanobacteria mixed with waterand sprayed it over the plants. The other plot got just as much water, without the bacteria.

From April to August, Loh and undergraduate researchers Ellen Deng and Lauren Church monitored the plants and collected data. Loh’s measurements showed that not only did the biofertilizer help his plants grow larger than those in the unfertilized plot, the bacteria did not leech into the surrounding plants. “Nutrients are taken up by plants before they can diffuse large distances,” he said.

With the data collection complete, Loh ate his research: He harvested and shared his vegetables with the entire Nocera group.

Next, Deng wants to plant pink roses, her favorite flower. Gilly hopes to use the biofertilizer in campus rain gardens, which are designed by undergraduate students to better absorb rain water and prevent pooling. “Every year, the new first-years who come in are more and more passionate about environmental causes,” Gilly said. “They’re an ever-growing force of sustainability.”

Over the next year, Dogutan and Harvard’s landscaping services will replace organic fertilizer with the biofertilizer on areas across Harvard’s Cambridge campus — the size of the plots only depends on how much of the new treatment they can get from Kula Bio, which is donating it. The more, the better, Dogutan said. More data will help her and the team hone their product for widescale use.

“This is still very new research,” Dogutan said. “We are still trying to figure out the details: the loading, the sequence, maybe we need to design the bacteria in a different way.” Once they do, they hope to encourage all Harvard campuses to consider switching to the biofertilizer as a way to improve the University’s commitment to sustainability and eventually to win wider acceptance and perhaps end “dead zones.”

“We have to do something because, really, we’re destroying the world,” Dogutan said. “Coming to work every day is great, but what is our higher purpose? It’s not just sending those emails. The higher purpose, at least for me, is giving back to the Harvard community the best way that I can.”

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