These lab-grown plants can clean up polluted land from heavy metals

When Franklin Keck harvested his first crop of lab-grown brassica plants two years into his PhD at Imperial College London, he realised he was onto something.

He had planted them in soil contaminated with zinc about a month earlier, and as he measured the quantity of metal present in the plants, he noticed they had accumulated three to five times the amount typically absorbed by the wild type.

“The levels of zinc needed to reach dietary toxicity are quite small, so I went large,” Keck says. “And it worked.”

Keck chose plants in the cabbage and mustard family because of their weed status across the northern hemisphere, which indicates greater adaptability. He then selected a species of bacteria commonly found in the same habitat and genetically modified it to enhance plant growth, metal binding capability and more.

By pairing the two, he found, the metal hyper-accumulating plants thrived.

Now a startup looking to provide a cheaper and more sustainable alternative for real estate developers to clean up brownfield sites and increase the value of contaminated land, PhytoMines aims to eventually cure land polluted by coal power plants, mining sites, nuclear fission operations and other industrial activities, making it newly usable for agriculture and human living.

“Chernobyl or Fukushima are some of the sites we’d like to target in the future,” Keck says. “So far, my data shows that I can accumulate zinc, nickel and strontium, but I think the list is going to expand — to cobalt, lithium, cesium and more.”

Keck can rely on a technology developed by one of his PhD supervisors to separate metals from plant tissue once harvested — for recycling or adequate disposal.

​​The plant biomass can be recycled to make textiles or bioethanol, for example, while the mined nickel can be reused to power electric vehicle batteries, zinc could make alloys for construction, and strontium, a byproduct of nuclear fission, can be permanently removed from radioactive soil.

“If we could plant our seeds on the Chernobyl site, I believe we could potentially make that land usable again over a few years and eventually even grow food there,” Keck says.

His plants’ life cycle is currently two to three months, and depending on the level of pollution, it can take multiple cycles to clean up land — anywhere from six to 18 months.

Unlike competitors, PhytoMines has genetically modified the bacteria living inside the plant rather than the plant itself, and this is important for two reasons: it allows Keck to use the same process to harvest a wide range of heavy metals and also avoid any potential side effects on the wider ecosystem caused by genetically modified tissue — such as a leaf — falling off the plant.

“This way I can control for the spread of non-natural genes into the environment,” says Keck, who’s currently exploring ways to programme the PhytoMines’ bacteria to be entirely dependent upon the plant, so that if it were to leave it, it would die immediately.

Keck joined Conception X Cohort 6 during PhytoMines’ early days to learn how to build a successful startup as a PhD founder. Over the past nine months, the core idea hasn’t changed. What’s changed is his trajectory.

“My ideas for where the market we’re going to address is have shifted,” Keck says. “Before, I thought it would be the whole world. Through Conception X, I realised I could start small and get access — then fuel up from there.”

Keck is one of our Cohort 6 Demo Day finalists. Register here to watch PhytoMines pitch on stage on Thursday 23 November from 3.30pm.