Researchers brew up biodegradable plastic alternative using discarded coffee grounds

26 Sep 2023 --- South Dakota State University, US, has used spent coffee grounds (SCG) to create biodegradable plastic for food and pharmaceutical packaging applications.

The films were characterized for their color, thickness, moisture content, tensile strength, elongation at break, water vapor permeability, transmittance of electromagnetic radiation and antioxidant properties. 

In their research, the scientists criticize the harmful effects of plastic packaging and the amount of SCG disposed of in the environment.

“We extracted lignocellulosic residue from SCG’s and prepared films. Our films are strong, biodegrade in the soil within 45 days at 30% soil moisture and possess properties comparable to plastic films,” Srinivas Janaswamy, from the Department of Dairy and Food Science at South Dakota State University, tells Packaging Insights.

“Our films can be used for packaging films. Also, our films block UV and IR radiation and display antioxidant properties, suggesting their use in food, pharmaceutical and other applications.”

Plastic replacement
Around 8 million metric tons of coffee grounds are discarded annually after beverage preparation.

“Disposing of such a mammoth amount of spent coffee grounds poses environmental challenges due to their intrinsic ability to contribute significant amounts of GHG like carbon dioxide and methane.”

Over two million cups of coffee are consumed at a global scale daily, generating coffee ground waste. The study highlights the plastic replacement films’ tensile strength and ability to biodegrade in the soil. The biodegradability and water vapor permeability decreased with increased salt content in the ground. SCG extract films “significantly” block UV and IR radiation.

Janaswamy tells us that the research aims to develop films that could replace plastic films to address the plastic issues that society is facing.

The researchers describe the film as “a promising, economical and [environmentally] sustainable route to produce strong biodegradable films to replace petrochemical plastics and thus is an attractive contribution to the circular bioeconomy.”

“We have been using several upcycled feedstocks such as agricultural biomass, fruit peels (avocado and banana), grasses and spent coffee grounds. In this set, we focused on spent coffee grounds due to their importance,” says Janaswamy.

Use for packaging
The South Dakota State University researcher emphasizes that plastic items are typically made of non-renewable and fossil-based materials, and the availability of these natural resources is finite, with their continuous extraction being unsustainable.

“Plastic degradation takes over several hundred years, and during this process, the production of microplastics and nanoplastics contributes to environmental contamination and damage. In addition, plastic contamination in food products and its possible health implications are also mounting and alarming,” asserts Janaswamy. 

“Consequently, plastic alternatives are in need, and the packaging industry would be the first to gain the advantage due to its abundant use of plastic products.”

Janaswamy says the researchers are in the process of scaling up the film. “Our research uses green and recyclable chemicals. Thus, scaling up our research protocol is feasible.”

“SCG forms a[n environmentally] sustainable source of lignocellulose for the design and development of plastic replacing films and other products. I believe the plastic industry would adopt our viable, simple and scalable solution to mitigate the plastic perils while creating value-addition for biowaste.”

By Sabine Waldeck