It’s not such an outlandish vision, according to a group of researchers: in a recent research perspective, they explain that the potential to grow plants in total darkness already exists and is being put to the test.
Usually, plants grow through photosynthesis, where sunlight triggers a chemical reaction that enables the plant to turn atmospheric carbon dioxide and water into glucose, which becomes their growth-powering energy source. Photosynthesizing plants use a specific metabolic pathway that requires sunlight to make this energy.
In the new perspective, the researchers explore a replacement for this process called ‘electro-agriculture’, whereby instead of leaves, solar panels capture the sun’s energy, using it to power electrolysis, a chemical reaction that transforms CO2 and water into another energy-rich molecule called acetate, which is then fed to plants. This process depends on a different metabolic pathway that does not require sunlight as the trigger, which is why acetate production can occur in the dark.
A few organisms can naturally grow ‘heterotrophically’—in darkness—by making acetate as their main food source, including some mushroom-producing fungi, yeast, and some types of green algae. But the team of researchers see potential beyond these, because of an interesting quirk in plants: it turns out that they all have the ability to make acetate before they emerge from the soil, when their seeds are still germinating in the dark.
This metabolic circuit gets switched off in adulthood, when plants trade acetate for glucose production fuelled by sunlight. But crucially, the acetate-making machinery remains intact.
That’s what inspired the researchers to explore the potential of electro-agriculture: they make the case that with some careful genetic engineering, acetate-production could be switched back on in adult plants. That remains a huge technical challenge, but they’re working on it, with early research showing some promising results in lettuce, rice, canola, pepper, and tomato crops that are being trained to consume acetate instead of glucose, according to Robert Jinkerson, associate professor in chemical and environmental engineering at the University of California, Riverside, and lead researcher on the paper.
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If this ability can be transferred to other crops, the researchers expect that electro-agriculture could decouple farming from the land at large scales. They envision tall warehouses, roofs stacked with solar panels that power the electrolysis in the floors below, producing a steady supply of acetate that’s fed through a hydroponic solution to the crops growing within.
Recent studies looking at acetate uptake in plants has shown that electro-agriculture is four times more efficient at converting solar energy into food than conventional photosynthesis. A plant burger produced through electro-agriculture would be over 200 times more energy-efficient than a beef burger, compared to a plant-based burger farmed using photosynthesis, which would be 50 times more energy-efficient than beef.
Beyond energy-efficiency, the most striking appeal of electro-agricultural is the monumental amount of land it could save, says Jinkerson and team. If all food in the US was produced using this approach, total land usage for farming would go down by 88%—from 1.2 billion acres to just 0.14. That freed land could be devoted to rewilding, in principle allowing “both ecological restoration and natural carbon sequestration at a massive scale,” they say.
It could also provide a temporary use for industrial emissions: if all the CO2 emitted by US industrial plants was captured to feed into electro-ag plants, hypothetically that could produce 56% of the food currently consumed in the US. (Though the researchers caution that efforts to decarbonize industry mean that farms shouldn’t necessarily rely on this source.)
Other big benefits to a closed and controlled agricultural system include the fact that fertilizers in the hydroponic supply can stay in rotation, making their use more efficient and limiting their escape into the surrounding environment. That could reduce eutrophication by 70-90%, the researchers calculate. The concept would also have real-world appeal for indoor farms right now, where growing plants in darkness could cut the intense energy use needed to keep plants well-lit and sufficiently cooled.
Looking further into the future, by enabling food production independent of the elements, electro-agriculture could bring farms to literal deserts; to places where food can’t grow but is needed most in the world, the research team explains.
Despite all this promise, electro-agriculture is still largely at a hypothetical stage, and there are big scientific leaps still needed to make it work well enough, and at scale, to bring down the costs of production compared to those of conventional farms. That could still be decades off. Yet, it would be a mistake to overlook its potential at this early stage, the team is keen to say.
“Electro-ag is a radical reconception of the global food system that offers meaningful progress toward resolving both climate change and world hunger,” they write. “This technology presents an opportunity to reinvent agriculture from the ground up.”
