Photosynthesis has evolved in plants for millions of years to turn water, carbon dioxide, and energy from sunlight into plant biomass and the foods we eat. This process, however, is very inefficient, with only about 1% of the energy found in sunlight ending up in the plant. Scientists at UC Riverside and the University of Delaware have found a way to bypass the need for biological photosynthesis and create food independent of sunlight using artificial photosynthesis.
The research, published in Nature Food, uses a two-step electrocatalytic process to convert carbon dioxide, electricity, and water into acetate, the form of the main ingredient of vinegar. Food-producing organisms then grow into the dark to consume acetate. Combined with solar panels to generate electricity to power electrocatalysis, this hybrid organic-inorganic system can increase the conversion efficiency of sunlight into food, up to 18 times more efficient for some foods.
“With our approach we seek to identify a new way of producing food that can break through the limits commonly imposed by biological photosynthesis,” said corresponding author Robert Jinkerson, a UC Riverside assistant professor of chemical and environmental engineering.
In order to integrate all the components of the system together, the output of the electrolyzer was optimized to support the growth of food-producing organisms. Electrolyzers are devices that use electricity to convert raw materials like carbon dioxide into useful molecules and products. The amount of acetate was produced while the amount of salt used was reduced, resulting in the highest levels of acetate ever produced in an electrolyzer to date.
“Using a state-of-the-art two-step tandem CO2 electrolysis setup developed in our laboratory, we were able to achieve a high selectivity toward acetate that could not be accessed through conventional CO2 electrolysis routes,” said corresponding author Feng Jiao at University of Delaware.
Experiments have shown that a wide range of food-producing organisms can grow in the dark directly on the acetate-rich electrolyzer output, including green algae, yeast, and fungal mycelium that produce mushrooms. Producing algae with this technology is almost fourfold more energy efficient than growing it photosynthetically. Yeast production is about 18-fold more energy efficient than how it is typically cultivated using sugar extracted from corn.
“We were able to grow food-producing organisms without any contribution from biological photosynthesis. Typically, these organisms are cultivated on sugars derived from plants or inputs derived from petroleum – which is a biological photosynthesis of a product that took place years ago. This technology is a more efficient method of turning solar energy into food, as compared to food production that relies on biological photosynthesis, “said Elizabeth Hann, a doctoral candidate in the Jinkerson Lab and co-lead author of the study.
The potential for employing this technology to grow crop plants was also investigated. Cowpea, tomato, tomato, rice, canola, and green pea were all able to utilize carbon from acetate when cultivated in the dark.
“We found that a wide range of crops could take the acetate we provided and build it into one of the major molecular building blocks for organism needs to grow and thrive. With some breeding and engineering that we are currently working on, we may be able to grow crops with acetate as an additional energy source to boost crop yields, “said Marcus Harland-Dunaway, a doctoral candidate in the Jinkerson Lab and co-lead author. the study.
By liberating agriculture from complete dependence on the sun, artificial photosynthesis opens the door to countless possibilities for growing food under increasingly difficult conditions imposed by anthropogenic climate change. Drought, floods, and reduced land availability would be less of a threat to global food security if crops and humans grew less resource-intensive, controlled environments. Crops could also grow in cities and other areas currently unsuitable for agriculture, and even provide food for future space explorers.
“Using artificial photosynthesis approaches to produce food could shift a paradigm for how we feed people. By increasing the efficiency of food production, less land is needed, lessening the impact agriculture has on the environment. And for non-traditional environments in agriculture, like outer space, increased energy efficiency could help feed more crew members with less inputs, “said Jinkerson.
This approach to food production was submitted to NASA’s Deep Space Food Challenge where it was a Phase I winner. The Deep Space Food Challenge is an international competition where prizes are awarded to teams to create novel and game-changing food technologies that require minimal inputs and maximize safe, nutritious, and palatable food outputs for long-term space missions.
“Imagine someday giant vessels growing tomato plants in the dark and on Mars — how much easier would it be for future Martians?” said co-author Martha Orozco-Cordenas, Director of the UC Riverside Plant Transformation Research Center.
Andres Narvaez, Dang Le, and Sean Overa also contributed to the research. The open-access paper, “A hybrid inorganic-biological artificial photosynthesis system for energy-efficient food production,” is available here.
The research was supported by the Translational Research Institute for Space Health (TRISH) through NASA (NNX16AO69A), the Foundation for Food and Agriculture Research (FFAR), the Link Foundation, the US National Science Foundation, and the US Department of Energy. The content of this publication is solely the responsibility of the authors and does not necessarily represent the official views of the Foundation for Food and Agriculture Research.
Header photo: Plants are grown in complete darkness in an acetate medium produced in an electrolyzer that replaces biological photosynthesis. (Marcus Harland-Dunaway / UCR)