Turning potatoes into batteries is a typical science activity for students. Potatoes, especially when soaked overnight in water, contain electrolytes which are essential in batteries. The potato battery itself doesn't last much long.

Aside from potatoes, what else could be turned into an alternative source of electricity? The answer: tomatoes.

A group of scientists in Florida are currently developing a biological fuel cell that uses waste or damaged tomatoes to produce electricity. It's definitely more complicated than making batteries out of potatoes.

Treatment Process

Florida considers tomatoes as a key crop, and the state generates about 396,000 tons of tomato waste annually.

However, the state lacks a good treatment process, said study researcher Professor Venkataramana Gadhamshetty.

Gadhamshetty said they wanted to find a way to treat tomato waste because it causes several problems. When dumped in landfills, tomato waste produces a powerful greenhouse gas called methane. When dumped in bodies of water, tomato waste can create major water treatment problems.

So the team developed a microbial electrochemical cell which can exploit tomato waste and allow it to generate electric current.

"We have found that spoiled and damaged tomatoes left over from harvest can be a particularly powerful source of energy when used in a biological or microbial electrochemical cell," said study co-author Namita Shrestha.

How does it happen? Shrestha said microbial electrochemical cells use bacteria to break down and oxidize organic material in tomato waste.

The oxidation process is triggered by the bacteria's interaction with tomato waste. It then releases electrons which are captured in the fuel cell. This becomes the source of electricity.

Theoretically, with this new method, the volume of tomato waste in Florida can power Disney Land for 90 days. Additionally, Shrestha said the process contributes in purifying the tomato-contaminated solid waste and preventing it from leeching into water supplies.

The "Secret" Ingredient

Researchers found that the natural lycopene found in tomatoes is a strong mediator that encourages the generation of electricity.

Gadhamshetty said common biotechnological applications perform better when using pure chemicals and not waste. But he and his colleagues found that the electrical performance from tomato waste was equal or better than using pure chemicals.

"These wastes can be a rich source of indigenous redox mediators and carbon, as well as electrons," added Gadhamshetty.

The power output from the microbial electrochemical cell still only generates a small power output. About 10 milligrams of tomato waste results to 0.3 watts.

Still, with further research and an expected scale up, the power output could rise by several orders of magnitude, researchers added.

Photo: David Huang | Flickr