Used coffee grounds could be turned into coffee cups

PhD student Dominik Kopp has developed a method to turn coffee grounds into lactic acid, which can then be used to produce biodegradable plastics for use in disposable coffee cups.

“Australians consume six billion cups of coffee every year, and the coffee grounds used to make these coffees are used only once and then discarded,” said Kopp, who is based at Macquarie University.

“In Sydney alone, over 920 cafes and coffee shops produced nearly 3000 tonnes of waste coffee grounds every year. 93% of this waste ends up in landfill, where it produces greenhouse gases that contribute to global warming.”

The good news is that 50% of coffee grounds are made up of sugars, which are ideal candidates to convert into valuable bio-based chemicals, or chemicals derived from plant- or animal-based feedstocks rather than crude oil. This means they are of particular interest to Kopp’s colleagues at Macquarie’s Sunna Lab, which is using the rapidly growing field of synthetic biology to address biotechnology and biomedical challenges.

“Our group is looking for new ways to convert biowaste — whether that be agricultural, garden, paper or commercial food waste — into valuable raw materials that can be used to produce high-value compounds in more environmentally friendly ways,” said Associate Professor Anwar Sunna, Kopp’s supervisor and head of the Sunna Lab.

Kopp sourced coffee grounds from one of the coffee shops on Macquarie’s campus and took them back to the lab, where he and his team assembled a synthetic pathway to convert the most abundant sugar in the coffee grounds — mannose — into lactic acid. The team’s method was inspired by a metabolic pathway that is thought to exist in an evolutionarily ancient organism, which lives in hot and extremely acidic environments.

“Lactic acid can be used in the production of biodegradable plastics, offering a more sustainable and environmentally friendly alternative to fossil fuel-derived plastics,” Kopp said. “You could use such plastics to make anything from plastic coffee cups to yoghurt containers to compost bags to sutures in medicine.”

Macquarie University PhD student Dominik Kopp.

Kopp presented his research as a poster at the 18th European Congress on Biotechnology in July, and was awarded the INOFEA Early Career Award for Applied Biocatalysis or Nanobiotechnology for his efforts. His next step will be to further refine the conversion pathway and improve the yield of lactic acid as he finishes his PhD.

“I think my project is one of many interesting approaches on how to use synthetic biology in a responsible manner for the development of a more sustainable and greener industry that doesn’t rely on crude oil,” he said.

“The simple idea that we are converting waste into a valuable and sustainable product is extremely exciting!”

Image credit: ©stock.adobe.com/au/amenic181