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Used Coffee Grounds Could Capture Potent Methane Emissions

ByAllison EckNOVA NextNOVA Next

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Here’s another good reason to keep brewing that morning joe.

A new

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study published in the journal Nanotechnology reports that used coffee grounds—the ones you dispose after plunging your French press or removing a coffee filter—have the ability to store methane, a powerful greenhouse gas that traps heat from the sun and contributes to climate change.

Methane is much more potent than its sister greenhouse gas, carbon dioxide. In fact, in 2013, the IPCC Fifth Assessment Report determined that a methane emission has 34 times the effect on temperature compared to a carbon dioxide emission of the same mass over the following 100 years (though this number varies ).

The waste from this could help reduce climate change.

Natural gas leaks contribute to the problem of mass methane emissions, as do many other industries that support our global economies—so scientists are trying to find ways to store it. Carbon-based materials are often cheaper, lighter, and safer than the gas cylinders that typically store methane at precariously high atmospheric levels. So postdoctoral fellow Christian Kemp and his colleagues at Ulsan National Institute of Science and Technology decided to make some coffee grounds, which have a carbon-to-nitrogen ratio of about 20 to 1.

Here’s Nathan Collins, writing for Pacific Standard:

They next stirred those grounds into a mix of water and potassium hydroxide, better known as lye, which they then dried and heated at temperatures between 700˚C and 900˚C. This produced activated carbon—the same stuff used in water filters and deodorizers. (Above 900ºC, their equipment mysteriously disintegrated, possibly because it came into contact with molten lye, the researchers note.) Finally, the team rinsed their sample in water to remove the lye.

The team then set out to see how much methane they could force into this sample of their activated carbon. Their results: about 70 grams of methane per kilogram of activated carbon, at roughly 14 percent of the pressure of a typical compressed natural gas tank—considerably less than Department of Energy’s 2000 objective of 238 grams of methane per kilogram of carbon at the same pressure.

Using this method, the authors of the study note that treated coffee grounds can store up to 7% of their weight in methane. It’s clearly far less than higher-tech solutions, but it’s also significantly cheaper, the authors claim. Plus, the source is only limited by our demand for coffee, which at times can seem limitless. The biggest challenge may simply be collecting the grounds, though gathering them from just a few large coffee chains could go a long way.