A truck dumps Cornell dining hall food waste at the university’s composting facility in March 2017. (Source: Robert Barker/University Photography)Considering that food waste is taking up a large percentage of landfills in the United States, researchers in a Cornell University-led study are detailing how to turn food waste into green energy using two different processes in the journal Bioresource Technology.
"Food waste should have a high value. We're treating it as a resource, and we're making marketable products out of it," said lead author Roy Posmanik, a postdoctoral researcher. "Food waste is still carbon — a lot of carbon."
The joint process first involves extracting all of the energy from food waste by pressure cooking the waste to create crude bio oil, eventually refining that oil into biofuel — a process called, hydrothermal liquefaction.
The second process involves anaerobically digesting the remaining food waste using microbes, which converts the waste into methane that can be used to create large amounts of heat and electricity.
"If you used just anaerobic digestion, you would wait weeks to turn the food waste into energy," said Posmanik, who works in both the laboratories of co-authors Jeff Tester, professor of chemical and biochemical engineering, and Lars Angenent, professor of biological and environmental engineering. "The aqueous product from hydrothermal processing is much better for bugs in anaerobic digestion than using the raw biomass directly. Combining hydrothermal processing and anaerobic digestion is more efficient and faster. We're talking about minutes in hydrothermal liquefaction and a few days in an anaerobic digester."
"We must reduce the amount of stuff we landfill, and we must reduce our carbon footprint. If we don't have to extract oil out of the ground to run cars or if we're using anaerobic digestion to make green electricity, we're enhancing energy and food security."
