The University of Idaho Civil Engineering program has developed a system to turn cow manure into biodegradable plastic.
Erik Coats, associate professor of Civil Engineering, is now in the process of completing the system with his research team. He said he ultimately hopes to commercialize the technology once it’s finished. However, he doesn’t see this as an overall replacement for the plastic currently used.
“If we look at all the plastic we use globally and we look at all of the organic waste that would be available to us to make plastic, we could never make enough plastic to completely displace,” Coats said. “But, the market is growing for these bio-plastics so there’s definitely a need out there.”
Coats said the system begins when manure is placed in a tank and fermented, producing organic acids. Once removed from the fermenter, what is left is manure solids, but also a lot of water.
“We separate the two. We get the solids and we get the water,” Coats said. “The solids go to an anaerobic digester.”
Anaerobic digestion is a process in which organic solids are placed in a tank held at a constant temperature. The solids will eventually degrade to produce methane.
Then the organic acid-filled water is fed to naturally occurring soil bacteria. When fed too much, the bacteria will consume it, but because they don’t need so much, they’ll polymerize it and store it as carbon molecules.
“If you think about it — if we, as humans, had large meals all the time, our body wouldn’t be able to consume all that food, so we’d store it all as fat,” Coats said. “So we’re treating the bacteria the same way, but they store the organic acids as these carbon molecules.”
Once the bacteria has stored all of the carbon, Coats and his team capture the carbon, and the plastic is formed.
“The carbon the bacteria store essentially is plastic,” Coats said.
The bacteria used are harvested at the wastewater treatment plant.
“They’re just natural, soil-dwelling bacteria. I could literally get them from the dirt,” Coats said. “That’s what’s really cool — there are hundreds of species that are known to produce our plastic.”
The scale model, located at the UI Dairy, can produce two to five pounds of plastic per day.
Coats is busy writing proposals, mentoring students and doing paperwork, so he widely credits his research team and UI support for making the project successful.
“Unfortunately I don’t get to spend a lot of time in the lab, so a lot of the research nowadays is constructed by the graduate students,” he said.
Coats also credits the Idaho Dairyman’s Foundation, the National Science Foundation and the United States Department of Agriculture for their generous financial assistance to the project.
Aaron Bharucha can be reached at email@example.com