A lot of the food that we produce, buy and make goes untouched. Instead of just chucking it in a trash can and shipping leftover grub and scraps to a landfill, conservationists have turned to composting as one way to reduce some wear and tear on our planet. Recently, energy producers are also getting into the game, turning to food waste as an alternative source of power. And now, new research shows how tomatoes that are rejected by stores as too damaged to sell may have another use: creating electricity and becoming literal power plants.
Unused tomatoes release electrons that can be harnessed into a fuel cell and later generate electric juice, according to a team of researchers from Florida and South Dakota, who presented their findings today at a meeting of the American Chemical Society. That's because lycopene — the pigment and phytochemical that gives tomatoes their ruby red hue — is a surprisingly effective generator of sorts that helps the fruit manufacture electric charges.
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"We wanted to find a way to treat this waste that, when dumped in landfills, can produce methane — a powerful greenhouse gas," says professor Venkataramana Gadhamshetty, whose lab conducted the research, "and when dumped in water bodies, can create major water treatment problems."
The researchers used a microbial electrochemical cell to kick start oxidation in tomatoes left over from Florida harvests. Tomatoes, like other fruits, shed electrons as they are exposed to air over time. The bacteria speeds this process.
The team then captured the electrons in a fuel cell to generate at least a little bit of power: 0.3 watts of electricity from 10 milligrams of tomato waste. If they can optimize the process and scale up, the researchers say there's enough annual tomato waste produced in Florida alone to power Disney World for three months.
Gadhamshetty notes the waste aspect of the tomatoes is particularly important. "Typical biotechnological applications require, or at least perform better, when using pure chemicals, compared to wastes," he says. "However, we found that electrical performance using defective tomatoes was equal or better than using pure substrates.
The reject tomatoes — turned down by supermarkets for reasons like worm injuries, freezing traces and growth cracks — join other leftover foods, like bread, dairy products and even beer finding second lives as energy creators. A program in Oakland, California, for example, plucks food from public sewage waste and converts it into energy in a process called anaerobic digestion. The brains behind the effort use bacteria to break down waste sludge and create a methane gas that can be harnessed into a heating element or electricity.
For environmentalists, it's a fine alternative to lugging all those scraps over to the landfill. Food waste and other trash that isn't exposed to oxygen eventually emits greenhouse gases. Those gases trap heat in the atmosphere and are the main culprits behind global warming.
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