14 December 2023

Here’s how U.S. native prairie grass can be turned into bioplastics


Researchers at South Dakota State University have made biodegradable bioplastic films from switchgrass, a weed capable of reaching significant heights that is widespread in North America’s grasslands

by Matteo Cavallito


The native grass of the American prairies can be used to produce biodegradable bioplastics. This is supported by a study by South Dakota State University. The investigation, led by Srinivas Janaswamy, an associate professor in the Department of Dairy and Food Sciences at the same university, paves the way for possible new environmentally friendly production.

Janaswamy’s work, says a statement from South Dakota State, is “on the leading edge of bioplastic development.” In recent years, the researcher “has demonstrated how biodegradable films can be successfully created from a variety of agriculture byproducts, including avocado peels and spent coffee grounds.”

A resource on American soil

The research focused on the properties of switchgrass (Panicum virgatum), a weed capable of reaching significant heights that is widespread in the prairies of North America. Here, the statement points out, this particular plant species “grows abundantly and in a variety of different climates, making it a valuable resource for soil conservation.”

Its defining characteristic is its high concentration (58 percent of its composition) of lignocellulosic matter, which is composed of cellulose, hemicellulose and lignin. The researchers extracted this material by placing it in a zinc chloride solution and then filtering, washing and drying it. The resulting residue was used to create the films. Which, according to the scientists , turned out to be of excellent quality.

Films biodegrade in 40 days

“The films have been characterized for color, transparency, thickness, moisture, water solubility, water absorption, water vapor permeability, tensile strength, elongation, and soil biodegradation,” the study states. . Analysis of their degradation capacity in soil also returned positive results.

The same films, in particular, “biodegrade completely within 40 days at 30% soil moisture.”

The study, in short, “open up a new window of opportunities to design and develop reusable, recyclable, and compostable films from underutilized, inexpensive, and abundant agricultural biomass contributing to the circular bioeconomy in a friendly and sustainable manner.” And generating additional income for farmers.

Stima delle quantità annue di plastica utilizzata nei terreni agricoli mondiali divise per tipologie di prodotto. FONTE: Assessment of Agricultural plastics and their sustainability. FAO, 2021

Estimated annual amounts of plastic used in global agricultural land divided by product type. SOURCE: Assessment of Agricultural plastics and their sustainability. FAO, 2021

Bioplastics are also decisive for agriculture

The importance of bioplastics has long been recognized. Researchers, in particular, pay special attention to all possible uses of the resource, in industry as well as in everyday life. Particular emphasis, then, has unsurprisingly been placed on uses in agriculture where, to date, traditional plastics continue to hold considerable sway as evidenced by the widespread use of polyethylene mulching films.

In recent months, research by California Polytechnic State University showed that U.S. farms, in particular, generate about 390,000 tons of plastic waste each year, with these plastics sheets contributing significantly. According to FAO, global demand for plastic films for agricultural use (greenhouses, mulching, and silage) will increase by 50 percent from 2018-2030. Increasing from 6.1 to 9.5 million tons.