The damaging greenhouse gas methane produced by manure and food waste in landfills could be harnessed as an energy source to minimize fossil fuel use and reduce landfill emissions.
Methane emissions account for 11 per cent of U.S. greenhouse gas emissions. Around half of all landfill sites in America collect and burn methane.
Animal manure decomposition on farms is one of the main contributors of methane emissions.
Now, a study has considered how to repurpose the wasted gas. Chemical engineers from Michigan Technological University examined the carbon footprint of anaerobic digestion, or composting organics without air, which can 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,” commented study lead author Sharath Ankathi in a statement.
The research team focused on a case study of a biogas facility in Colorado using a life cycle assessment, which can determine an activity’s environmental impact.
They dug into the plant’s organic waste and assessed the process that turns food waste from restaurants in Denver and manure from dairy farms near the facility into bio-methane.
Bacteria were used to break down the solids and liquids in the waste without allowing them to come into contact with oxygen.
The end products are a liquid digestate, which can be used for fertilizer or industrial processes, and bio-methane, which can be used like natural gas.
The team found that bio-methane produced from all available food waste and dairy manure in the U.S. annually would offset about .74 per cent of annual natural gas demand. The challenge to mitigate more is still big, according to the researchers.
Photo credit: Alan Levine/ CC BY 2.0