in science fiction film pitch dark (Now streaming on Peacock!), interplanetary travelers encounter creatures that spend their entire lives in the dark. While there are certainly creatures who never see the Sun and live and die, this is far from ideal. Our entire food web, with a few exceptions – such as hydrothermal vents – is built on a foundation of sunlight.
Plants take in sunlight to convert water, carbon dioxide and minerals into oxygen and sugars. Herbivores then eat those plants, turning them into more complex proteins and fats. Non-vegetarians eat those ingredients and convert them into them, etc. Eventually, they die, and their constituent parts break down into minerals which then play a role in the growth of more plants, and the cycle continues. But it all starts with sunlight.
Despite the ubiquity and success of plants throughout the Earth’s surface, they are actually very incapable of converting sunlight into energy. On average, plants capture only about 1% of sunlight and convert it into energy for growth. After all, evolution is only as efficient as it is necessary to survive. One consequence of this inefficiency is that crop plants require more land than is theoretically necessary to grow. If they were better able to capture the sunlight that hits them, they could hypothetically be grown on a smaller solar footprint.
Scientists at the University of California, Riverside and colleagues set out to find out whether they could do this by bypassing natural photosynthesis altogether and feeding the plants on artificially derived acetate. Their findings were published in the journal nature food,
To test their idea, they kept several different food crops, including algae, yeast and mushroom-bearing fungi, in the dark, blocking any exposure to sunlight. Normally, this would be a recipe for death, but plants don’t really need sunlight to live and grow. They only need those bi-products that help in permeating sunlight.
Using a two-stage electrolyzer with silver and copper catalysts in solution, the scientists succeeded in reducing CO 2 to acetate. The first stage of the electrolyzer converts CO2 into CO. The second step converted it to acetate, either in the form of sodium or potassium acetate.
The entire system was powered by solar panels, meaning that sunlight was still used, but at a much higher efficiency and without direct exposure to light from the plants. The acetate was then fed to the plants in the hope that they could grow. Not only did they grow, but they grew at rates not seen with natural photosynthesis. Algae grown using this method were about four times more efficient than normal while yeast grew at about 18 times the normal rate.
The team submitted its way to grow food for NASA’s Deep Space Food Challenge—a competition that seeks new ways to grow food for future space missions—and it was a Phase I winner. Using electricity, whether from the Sun or through other sources, to synthesize acetate and grow food without direct exposure to light has some obvious implications for the future of space travel, but it also has applications at home.
Because food crops grown this way do not require direct exposure to light and are more efficient, foods can be grown in areas that are generally unsuitable for agriculture. In addition, they can be grown with less impact on land resources, reducing the anthropogenic cost of food production as our population continues to grow and the consequences of climate change continue.
It also provides some hope for our continued existence when and if some catastrophic event forces humanity to flee underground for our survival. At least our dark underground cities would have chips of algae. Delicious.
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