Photosynthesis has evolved in plants for millions of years to convert water, carbon dioxide, and energy from sunlight into plant biomass and the foods we eat. However, this process is very inefficient, as only about 1% of the energy in sunlight ends up in the plant. Scientists at the University of California Riverside and the University of Delaware have found a way to completely 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 main ingredient form of vinegar. Then food-producing organisms consume acetate in the dark to grow. Combined with solar panels to generate electricity to power electrical stimulation, this organic-inorganic hybrid system can increase the efficiency of converting sunlight into food, up to 18 times more efficient for some foods.
“With our approach, we sought to identify a new method of food production that could go beyond the limits typically imposed by biological photosynthesis,” said corresponding author Robert Jenkinson, an assistant professor of chemical and environmental engineering at the University of California, Riverside.
In order to integrate all components of the system together, the output of the electrolyzer is optimized to support the growth of food-producing organisms. Electrolyzers are devices that use electricity to convert raw materials such as carbon dioxide into useful molecules and products. The amount of acetate produced was increased while the amount of salt used was reduced, resulting in the highest levels of acetate ever produced in the electrolyzer to date.
“Using the latest two-step carbon dioxide electrolysis setup developed in our laboratory, we were able to achieve high selectivity toward acetate that is not accessible by conventional carbon dioxide electrolysis methods,” said corresponding author Feng Jiao at the university. Delaware.
Experiments have shown that a wide range of food-producing organisms can be grown in the dark directly on the output of an acetate-rich electrolyzer, including green algae, yeast, and the fungus-producing fungi. Algae production with this technique is four times more energy efficient than photosynthesis. Yeast production is about 18 times more energy efficient than the way it is typically grown using sugar from corn.
“We were able to grow food-producing organisms without any contributions from biological photosynthesis. Typically, these organisms are grown on plant-derived sugars or petroleum-derived inputs — the product of biological photosynthesis that occurred millions of years ago,” said Elizabeth Hahn, a student PhD in Jenckerson’s lab and co-lead author of the study, said the technology is a more efficient way to convert solar energy into food, compared to food production that relies on biological photosynthesis.
The possibility of using this technology to grow crop plants has also been investigated. Cowpeas, tomatoes, tobacco, rice, canola, and green peas were able to benefit from carbon from acetate when grown in the dark.
“We found that a wide variety of crops can take the acetate we introduced and build it into the key molecular building blocks an organism needs to grow and thrive,” said Marcus Harland-Donaway, a doctoral candidate in Jenckerson’s lab and co-lead author of the study.
By freeing agriculture from its complete dependence on the sun, artificial photosynthesis opens the door to endless possibilities for growing food under the increasingly challenging conditions imposed by anthropogenic climate change. Droughts, floods, and reduced availability of land would be less of a threat to global food security if human and animal crops were grown in less resource-intensive and controlled environments. Crops can also be grown in cities and other areas that are not currently suitable for agriculture, and even provide food for future space explorers.
“Using artificial photosynthesis approaches to food production could be a paradigm shift for how we feed people. By increasing the efficiency of food production, less land is needed, and the impact of agriculture on the environment is reduced. For farming in non-traditional environments, such as outer space, the Increased energy efficiency could help feed more crew members with fewer inputs,” Jenkerson said.
This approach to food production was submitted to NASA’s Deep Space Food Challenge where it was the first stage winner. The Deep Space Food Challenge is an international competition in which prizes are awarded to teams for inventing new, game-changing food technologies that require minimal inputs and maximizing safe, nutritious and acceptable food output for long-duration space missions.
“Imagine one day giant ships growing tomato plants in the dark and on Mars – how easy would that be on Mars in the future?” Co-author Martha Orozco Cardenas, director of the Plant Transformation Research Center at the University of California, Riverside, said.
Andrés Narváez, Dang Lu, and Sean Ofira also contributed to the research. The open-access paper, “Hybrid Inorganic and 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 Food and Agriculture Research Foundation (FFAR), the Link Foundation, the US National Science Foundation, and the US Department of Energy. The content of this publication is the sole responsibility of the authors and does not necessarily represent the official views of the Food and Agriculture Research Foundation.
Banner photo: Plants grow in complete darkness in an acetate medium produced in an electrolyzer that replaces biological photosynthesis. (Marcus Harland-Dunway/UCR)