Another possible use for coffee grounds: Biodegradable plastic
We've been hearing more and more about eco-friendly biodegradable plastics, made from cellulose nanofibers. Although those fibers are typically harvested from wood waste, new research shows that they could also be obtained from mega-plentiful used coffee grounds.
Cellulose is the most abundant organic compound on Earth. Among other places, it's found in the cell walls of plants – it's what allows plant leaves and stems to be as strong as they are.
Coffee grounds also aren't exactly in short supply, with the International Coffee Organization estimating that over 6 million tons (5.4 million tonnes) are produced worldwide annually. Some of them are composted, while others may someday be put to use in substances such as carbon capture materials, biofuels, or road materials. That said, for now at least, most coffee grounds still end up being dumped in landfills.
Led by Assoc. Prof. Izuru Kawamura, scientists at Yokohama National University decided to see if the waste product could instead be used as a source of cellulose nanofibers. Coffee grounds certainly showed promise, as approximately half of their weight and volume is made up of cellulose.
The researchers utilized a previously-developed process known as catalytic oxidation, in which a catalyst was used to oxidize the ground beans' cell walls. When the resulting cellulose nanofibers were analyzed, they were found to have a desirable uniform structure. They also integrated well with polyvinyl alcohol, which is a polymer used in the production of biodegradable plastics – and the scientists already have an idea for what one of the first coffee-plastic products might be.
"Now, more and more restaurants and cafes have been banned from using single-use straws," says Kawamura. "Following that movement, we aim to make a transparent disposal coffee cup and straw with an additive comprising cellulose nanofibers from spent coffee grounds."
A paper on the research was recently published in the journal Cellulose.