New cell generates electricity from waste tomatoes

Scientists, including one of Indian-origin, are developing a biological-based fuel cell that uses damaged or waste tomatoes to produce electricity.
"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 Namita Shrestha, South Dakota School of Mines and Technology.
"The process also helps purify the tomato-contaminated solid waste and associated waste water," Shrestha said.
Tomatoes are a key crop in Florida, said Venkataramana Gadhamshetty, professor at South Dakota School of Mines and Technology.
Florida generates 396,000 tonnes of tomato waste every year, but lacks a good treatment process, said Gadhamshetty who began the research at Florida Gulf Coast University.

"We wanted to find a way to treat this waste that, when dumped in landfills, can produce methane - a powerful greenhouse gas - and when dumped in water bodies, can create major water treatment problems," he said.

The team developed a microbial electrochemical cell that can exploit tomato waste to generate electric current.
"Microbial electrochemical cells use bacteria to break down and oxidise organic material in defective tomatoes," Shrestha said.
The oxidation process, triggered by the bacteria interacting with tomato waste, releases electrons that are captured in the fuel cell and become a source of electricity.
The natural lycopene pigment in tomatoes, the researchers have found, is an excellent mediator to encourage the generation of electrical charges from the damaged fruits.

"Typical biotechnological applications require, or at least perform better, when using pure chemicals, compared to wastes," Gadhamshetty said.
"However, we found that electrical performance using defective tomatoes was equal or better than using pure substrates. These wastes can be a rich source of indigenous redox mediators and carbon, as well as electrons," he said.
At the moment, the power output from their device is quite small - 10 milligrammes of tomato waste can result in 0.3 watts of electricity.
However, the researchers said that with an expected scale up and more research, electrical output could be increased by several orders of magnitude.

According to researchers, there is theoretically enough tomato waste generated in Florida each year to meet Disney World's electricity demand for 90 days, using an optimised biological fuel cell.
They plan to improve the cell by determining which of its parts - electrode, electricity-producing bacteria, biological film, wiring - are resisting the flow of electricity.