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Bacteria can turn rotting food into renewable energy

An anaerobic digester is a sealed tank filled with bacteria that works on edible scraps and produce a gas called biogas. Image: Shutterstock

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3 menit membaca Nov. 27, 2013

In an era of climate change, rising ocean temperatures and extreme weather, scientists are searching for solutions to global fluctuations — and one might be right under their noses.

According to a story on ThinkProgress, an inventive recycling procedure that has been used on farms for years could be repurposed and help cool off the planet. Instead of processing cow manure, the procedure would process rotting food.

The tool for the task is an anaerobic digester, a sealed tank filled with bacteria that operates like the stomach of a cow. Anaerobic digesters have earned the nickname “optimized cow stomachs” by the American Biogas Council’s Patrick Serfass.

Here’s how they work: When waste matter is shoveled inside the tank, the bacteria go to work on the edible scraps and produce a gas called biogas. Biogas can be transformed into a renewable form of natural gas, processed into vehicle fuel, and combusted to produce electricity, Serfass said.

Solids separated during the process are used as compost or field fertilizer.

“Just like a cow, you get a solid, a liquid, and a gas after digestion,” he said.

The anaerobic digestion of half of America’s food waste would produce “enough electricity … to power 2.5 million homes for a year,” according to the EPA.

Anaerobic digesters also would alleviate the amount of methane in landfills, an important thing to consider because methane gas is 34 times more damaging to the atmosphere than carbon dioxide, according to the Intergovernmental Panel on Climate Change.

Education and awareness of anaerobic digesters is in order, as Americans are more apt to recycle their soup cans and milk jugs than they are their banana peels and apple cores.

“In the ‘80s and ‘90s, Americans started to get serious about recycling,” said Eric Goldstein of the Natural Resources Defense Council. “But that paper, glass, metal, and plastic that we so carefully keep out of the trashcan only accounts for about one-third of the total waste stream. And because we don’t do it perfectly, we only actually keep about one-quarter of our trash out of landfills. I don’t think most people realize that when they toss take-out in the trash, they are contributing to climate change.”

While European countries far surpass America in their food recycling, more than 150 U.S. cities are following suit, said Neil Seldman of the Waste to Wealth Program at the Institute for Local Self Reliance. The cities include New York, Portland, San Antonio, San Francisco, and Seattle.

“Anaerobic digestion is going to just explode in the Northeast and Bay Area in the next few years,” Seldman said. “In these crowded urban areas, it costs at least $100 for every ton of trash you have hauled away. It just makes sense to deal with it locally and get value from your waste.”

Some states have put in place requirements that organic-waste generators such as fast-food joints, grocery stores, and restaurants send their trash to a recycling facility for anaerobic digestion. Vermont started the trend in 2012.

“The leadership of these states is a big deal,” Serfass said “Although the technology is straightforward, an anaerobic digester isn’t cheap to build. If we want companies to be willing to invest in the infrastructure, it certainly helps them to know that they will have a constant stream of food waste coming their way for years to come.”