At the end of this very inefficient process, only 1% of the energy in sunlight passes to the plant. UC Riverside and University of Delaware scientists have found a way to completely eliminate the need for biological photosynthesis and create sunlight-independent food 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 component of vinegar. Food-producing organisms then consume acetate in the dark to grow. This hybrid organic-inorganic system, when combined with solar panels to generate the electricity to power the electrocatalysis, could make 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 way of producing food that could transcend the limits normally imposed by biological photosynthesis," said Robert Jinkerson, assistant professor of chemical and environmental engineering at UC Riverside.
To bring 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 such as carbon dioxide into useful molecules and products. The amount of acetate produced was increased while the amount of salt used was reduced, achieving the highest levels of acetate ever produced in an electrolyzer.
"Using the state-of-the-art two-stage tandem CO2 electrolysis setup developed in our lab, we were able to achieve a high selectivity towards acetate that was inaccessible through conventional CO2 electrolysis pathways," said co-author Feng Jiao of the University of Delaware. Experiments showed that a wide variety of food-producing organisms, including green algae, yeasts, and fungus-producing fungal mycelium, can be grown directly in the dark at the output of acetate-rich electrolyzers. Growing algae with this technology saves about four times more energy than growing algae photosynthetically. Yeast production is approximately 18 times more energy efficient than when grown using sugar typically extracted from corn.
Elizabeth Hann, PhD candidate at Jinkerson Labs and co-author of the study; “We have been able to grow food-producing organisms without any contribution from biological photosynthesis. Typically, these organisms are grown on sugars from plants or inputs from petroleum, a product of biological photosynthesis that took place millions of years ago. This technology converts solar energy into food compared to food production based on biological photosynthesis. It is a more efficient method of converting.” says.
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When the potential of this technology in plant cultivation is investigated; cowpea, tomato, tobacco, rice, canola and green peas were found to be able to use carbon from acetate when grown in the dark.
Marcus Harland-Dunaway, PhD candidate at Jinkerson Labs and co-author of the study, said, "We've found that a wide variety of crops can take the acetate that we provide and put it into the major molecular building blocks an organism needs for growth and development. We're now working on improving crop yields with some breeding and engineering work." We can grow crops with acetate as an additional energy source." says.
Artificial photosynthesis frees agriculture from total reliance on the sun, opening the door to countless possibilities for growing food under increasingly difficult conditions brought on by anthropogenic climate change. Droughts, floods and declining land availability will pose less of a threat to global food security as crops for humans and animals are grown in controlled environments that use fewer resources. Crops are currently grown in cities and areas unsuitable for agriculture and could even provide food for future space explorers.
According to Jinkerson; “Using artificial photosynthesis approaches to produce food could be a paradigm shift in how we feed humans. By increasing the efficiency of food production, less land is needed and agriculture's impact on the environment is reduced. Increased energy efficiency for agriculture in non-traditional environments such as space means more energy with less input. can help feed more crew members"
This approach to food production was submitted to NASA's Deep Space Food Challenge, where it won stage one. The Deep Space Food Challenge is an international competition where awards are given to teams for creating new and game-changing food technologies that maximize the output of safe, nutritious and delicious food that requires minimal input for long-duration space missions.
Co-author Martha Orozco-Cárdenas, director of the UC Riverside Plant Transformation Research Center; “Imagine giant ships growing tomato plants in the dark and on Mars one day – how easy would that be for future Martians?” says.