Harvesting fruits and vegetables is an imperfect process. Even when using the most efficient methods, farms end up with damaged fruit and fruit that has over ripened. That waste produce becomes just that, waste. A large commercial farm will have tons of waste fruit and vegetables every year. In Florida, where tomatoes grow practically year-round, there are 396,000 tons of waste tomatoes every year.
Researchers from the South Dakota School of Mines & Technology, Princeton University and Florida Gulf Coast University have teamed up to demonstrate that all of those damaged tomatoes need not go to waste -- they can generate electricity. The team has developed a microbial electrochemical cell that can use tomato waste 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,” says Namita Shrestha, a graduate student working on the project. “The process also helps purify the tomato-contaminated solid waste and associated waste water.”
The huge amount of tomato waste has created a waste treatment issue in Florida. Either the waste goes to landfills where it produces methane or it's dumped into a body of water where it then becomes a major water treatment issue. Using the waste in the fuel cell keeps it out of landfills and water and the breakdown of the tomatoes is instead harnessed to generate electricity.
The bacteria in the fuel cell trigger an oxidation process that releases electrons which are captured by the fuel cell and become a source of electricity. The tomatoes have proven to be a potent energy source. The natural lycopene in the tomatoes acts as a mediator to encourage electricity generation and the researchers say that while waste material usually performs poorly compared to pure chemicals in fuel cells, the waste tomatoes perform just as well or better.
In their first trials, the power output is small at just 0.3 watts of electricity per 10 milligrams of tomato waste, but they say that with more research and tweaking to improve the electricity generation, in addition to scaling up, the output should increase by several orders of magnitude. In fact, they believe that there is enough tomato waste in Florida every year to meet Disney World's electricity demand for 90 days.
The researchers presented their work last week at the National Meeting & Exposition of the American Chemical Society.