Sustainability | Ecotrope

Food Waste Can Be Turned Into Energy, Too

Ecotrope | Jan. 18, 2013 3:23 a.m. | Updated: Feb. 19, 2013 1:27 p.m.

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What are the trade-offs between composting food waste and putting it in a methane digester that produces electricity?

What are the trade-offs between composting food waste and putting it in a methane digester that produces electricity?

Last week, a new report released the news that 30 to 50 percent of the world’s food is wasted. Food waste makes up 18 percent of the waste currently going into landfills in the U.S., according to the Environmental Protection Agency.

Uneaten food doesn’t have to be a total waste, as Portland has learned over the past year through its curbside composting program.

Composting turns food scraps into fertilizer so it doesn’t rot in a landfill and produce methane, a greenhouse gas that’s 23 times more potent than carbon dioxide. But it’s stinky business. The facility composting a large portion of Portland’s food scraps is in a high-stakes fight to continue operating as odor complaints from neighbors stack up.

There is an alternative to composting food waste. You can put it in a methane digester and use the resulting gas to make electricity (though it can be stinky, too.) The EPA says if half of the food waste in the U.S. went into methane digesters, it would generate enough electricity to power 2.5 million homes.

Quite a few dairy farms use methane digesters for cow manure, and wastewater treatment plants use them for processing sewage. But this year JC Biomethane is building Oregon’s first non-farm digester for food waste and yard debris in Junction City. Columbia Biogas is working on a similar concept for Portland.

According to JC Biomethane project spokesman Dean Foor, the tank shape and mixing technology are different for digesters handling food waste, but the basic biology is the same: Anaerobic bacteria eat organic material and create methane that can be burned to make electricity.

The waste JC Biomethane will be taking in would otherwise be composted, but Foor says the methane digester actually releases fewer greenhouse gas emissions than composting, which emits nitrous oxides.

In addition to producing methane, the digester in Junction City will produce enough compost tea to offset a thousand acres of fertilizers made from fossil fuels.

However, burning methane for electricity does produce some air pollution.

Anaerobic digestion of food waste is fairly common in Europe and it’s gaining traction in the U.S. as more cities opt to add food scraps to their existing digesters at wastewater treatment facilities. Do you see a downside to making energy from food waste instead of composting it?

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