Methane is far more damaging as a greenhouse gas than carbon dioxide—25 times more so. The gas, which is produced by decomposing organic materials in the absence of air, not only traps heat efficiently but is also a health and safety hazard because it's so concentrated in landfills. About half of the landfills in the US collect and burn methane, mitigating the danger but still contributing to atmospheric methane and carbon dioxide levels. Animal manure decomposition on farms is the main contributor of methane emissions in agriculture.
Repurposing that wasted gas is the focus of a new study published in the journal Environmental Progress and Sustainable Energy by chemical engineers from Michigan Technological University. Specifically, they examined the carbon footprint of anaerobic digestion—composting organics without air—which can be used to redirect methane into a usable energy source.
"We found that bio-methane produced through anaerobic digestion emits far less than its fossil natural gas equivalent," says Sharath Ankathi, the paper's lead author and a PhD student at Michigan Tech. Studying each product's carbon footprint is a way to assess its social, environmental and economic impact—in other words how sustainable it is—which Ankathi says is "defined as helping current generations without compromising their needs or the needs of future generations."