Study trials coffee grounds as plastic packaging

A new study has revealed how spent coffee grounds can be made into biodegradable films — that could one day offer an alternative to plastic.

Over the past few years, Srinivas Janaswamy, associate professor in South Dakota State University’s Department of Dairy and Food Science, has focused his research on creating biodegradable alternatives to plastic, often from agricultural byproducts. Previously, Janaswamy has prepared films from the cellulose-rich peels of avocados and corn stover.

Spent coffee grounds were chosen as the source material for Janaswamy’s latest project for few different reasons. First, spent coffee grounds are widely available with millions of tons produced annually.

While most end up in landfills, some are used for other things, such as gardening. While this may seem like an environmentally conscious move, Janaswamy said it actually can cause environmental problems.

“Generally, we discard the coffee ground grounds after we make our coffee,” Janaswamy said. “Some of us use them for compositing, gardening and other things. Ironically, such a process demands high amounts of oxygen and releases a good amount of methane, which contributes to global warming.”

Second, as emerging economies begin adding chain coffee shops the amount of spent coffee grounds will only increase. Using this otherwise unused resource for biodegradable films is a sustainable and economical solution to the plastic crisis.

Finally, spent coffee grounds contain lignocellulosic fibers, the material needed to make the films.

Coffee into film

To prepare the films, the research team first extracted lignocellulosic fibers from the spent coffee grounds. A green chemical modification process was then deployed to make the film more suitable for packaging.

The resulting films were able to biodegrade within 45 days in the soil while also having high tensile strength. Further, the films also had some unique properties of which researchers took note.

“Interestingly, these films could block significant amounts of UV radiation and display antioxidant properties,” Janaswamy said. “I sincerely believe this research outcome opens up new applications for spent coffee grounds.”

While this should still be considered “stage one” of turning spent coffee grounds into films, the results from this study showed significant promise.

“The potential for plastic-replacing films from the widely discarded but plentiful and sustainable spent coffee grounds remain unscathed and exciting toward value creation,” Janaswamy said.

Sajal Bhattarai, an SDSU graduate and a doctoral candidate at Purdue University, collaborated with Janaswamy on the research.

The study, titled Biodegradable, UV-blocking, and antioxidant films from lignocellulosic fibers of spent coffee grounds, was published in the International Journal of Biological Macromolecules. The U.S. Department of Agriculture’s National Institute of Food and Agriculture provided funding for the project.