Friday, August 12, 2022

Producing food without sunshine using artificial Photosynthesis

Imagine someday giant vessels growing tomato plants in the dark and on Mars.

Growing global food demand is currently facing a major constraint of efficient energy conversion using photosynthesis. Photosynthesis has evolved in plants for millions of years to turn water, carbon dioxide, and the energy from sunlight into plant biomass and the foods we eat.

Most crop plants can convert sunlight and CO2 into plant biomass at an energy conversion efficiency of only ~1% or less. Large tracts of land are thus required for crop cultivation to capture the requisite solar energy to provide food for humanity.

Recent breeding and genetic engineering efforts to increase photosynthetic efficiency have yielded only select gains in a limited number of food crops.

Now, scientists at UC Riverside and the University of Delaware have found a way to bypass the need for biological photosynthesis altogether and create food independent of sunlight by 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 component of vinegar.

“Here we describe the development of a hybrid inorganic–biological system for food production. A two-step electrochemical process converts CO2 to acetate, which serves as a carbon and energy source for algae, yeast, mushroom-producing fungus, lettuce, rice, cowpea, green pea, canola, tomato, pepper, tobacco, and Arabidopsis. Coupling this system of carbon fixation to photovoltaics offers an alternative, more energy-efficient approach to food production.” Study mentions.

Food-producing organisms consume acetate in the dark to grow. Combined with solar panels to generate electricity to power the electrocatalysis, this hybrid organic-inorganic system could increase the conversion efficiency of sunlight into food, which is almost up to 18 times more efficient for some foods.

“With our approach, we sought to identify a new way of producing food that could break through the limits normally 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 produced was increased while the amount of salt used was decreased, 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 towards acetate that cannot be accessed through conventional CO2 electrolysis routes,” said corresponding author Feng Jiao at the University of Delaware.

“We were able to grow food-producing organisms without any contributions from biological photosynthesis. Typically, these organisms are cultivated on sugars derived from plants or inputs derived from petroleum—which is a product of biological photosynthesis that took place millions of 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.

“We found that a wide range of crops could take the acetate we provided and build it into the major molecular building blocks an organism needs to grow and thrive. With some breeding and engineering that we are currently working on we might be able to grow crops with acetate as an extra energy source to boost crop yields,” said Marcus Harland-Dunaway, a doctoral candidate in the Jinkerson Lab and co-lead author of the study.

Futuristic view:

  1. Liberating agriculture from complete dependence on the sun.
  2. Artificial photosynthesis opens the door to countless possibilities for growing food under the increasingly difficult conditions imposed by anthropogenic climate change.
  3.  Drought, floods, and reduced land availability would be less of a threat to global food security if crops for humans and animals grew in less resource-intensive, controlled environments. Crops could also be grown in cities and other areas currently unsuitable for agriculture, and even provide food for future space explorers.

Recognition received by the study:

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-duration space missions.

“Imagine someday giant vessels growing tomato plants in the dark and on Mars—how much easier would that be for future Martians?” said co-author Martha Orozco-Cárdenas, director of the UC Riverside Plant Transformation Research Center.

Journal Reference

  1. Elizabeth C. Hann, Sean Overa, Marcus Harland-Dunaway, Andrés F. Narvaez, Dang N. Le, Martha L. Orozco-Cárdenas, Feng Jiao & Robert E. Jinkerson; A hybrid inorganic–biological artificial photosynthesis system for energy-efficient food production. Nature Food, 3, 461–471 (2022) DOI: 10.1038/s43016-022-00530-x
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