Every year, the state of Florida throws out nearly 400,000 tons of tomato waste.
The sludge is a mixture of damaged or worm-eaten tomatoes as well as unwanted skin and seeds from processed products like ketchup. It goes into landfills where it can produce dangerous methane gas, or ends up in waste water.
A group of researchers at South Dakota School of Mines & Technology has found a way to treat the problematic waste and turn it into something useful: electricity.
How does a tomato become power? The researchers have developed a special microbial fuel cell to process the waste and turn it into electricity. It uses bacteria to break down the organic material in the tomato waste, oxidizing it and generating an electrical charge. The process also neutralizes the waste so that it no longer emits greenhouse gases.
Asa waste water treatment or a renewable energy source, the concept wouldn’t have much appeal. But accomplishing both things at once could make tomato power a viable option for agricultural communities like Immokalee, the tomato farming community in Florida that produces the bulk of the state’s tomato waste.
“My hope for this kind of thing is that it can be used in rural areas where you have a lot of agricultural waste and you don’t necessarily have access to a power supply, particularly in the developing world,” said Alexander Fogg, who started the project.
The research is currently being led by Namita Shrestha and other scientists under professor Venkataramana Gadhamshetty. The entire process takes a few weeks to complete, and the power output from the tomatoes begins to die off after 10 to 14 days.
It’s a potentially expensive way to process waste, but generating electricity would make it more economically viable. That combination might appeal to cities, which usually shoulder the responsibility for processing agricultural waste.
This kind of approach could work for other kinds of food waste as well, but researchers found that tomatoes contain some micro-nutrients that make it especially successful.
That annual 400,000 tons of tomato waste could potentially generate enough electricity to power Disney World for 90 days, according to the researcher’s calculations. Right now it’s still a small scale endeavor. The team’s current design only generates 0.3 watts of electricity for each 10 milligrams of tomato byproduct. But they’re working to improve the design and expect to quickly scale up.
Turning agricultural food waste into a power source is unlikely to ever become as big as something like solar or wind energy. But by solving two problems at once, it has the potential to find a niche over the next decade.
At the end of the process there is still tomato. The waste looks the same to the human eye, but it has been fundamentally changed. The chemical content of the tomato bits has been broken down and treated, meaning no more greenhouse gas emissions. It’s just red, harmless sludge that maybe helped power a light bulb somewhere.