Making clear biodegradable film from crop residue

Making a transparent, biodegradable film from crop residue and native grasses—that is the goal that South Dakota State University assistant professor of dairy and food science Srinivas Janaswamy is pursuing through a three-year, $481,618 U.S. Department of Agriculture grant. What he is doing will benefit farmers as well as the environment.

“We are extracting cellulose fraction from renewable agricultural residues and then solubilizing it to make strong, biodegradable films,” said Janaswamy, who is also a South Dakota Agricultural Experiment Station researcher. Using the nation’s abundant supply of agriculture biomass to create biodegradable products that can replace petroleum-based plastics will reduce the impact these packaging materials have on the environment and generate extra income for farmers.

Janaswamy is developing processes to extract cellulose fraction from corn stover and soybean biomass, wheat and oat straw, as well as switchgrass and prairie cordgrass through the National Institute of Food and Agriculture project. His team also includes lecturer Michael Twedt of SDSU’s Department of Mechanical Engineering and senior research scientist Madhav Yadav of the USDA Agricultural Research Center in Wyndmoor, Pennsylvania. Data generated from a North Central Regional Sun Grant Center project helped Janaswamy secure the USDA funding.

Farmers are baling corn stalks and leaves for livestock feed and bedding and then leaving the rest in the field to improve soil health. “Both are important,” said Janaswamy, but he sees the possibility of gaining additional profit by using a fraction of the corn residue for biodegradable plastics.

Assuming a ton of corn stover is worth $83, based on its value as livestock feed, and using a conservative yield estimate of 1 ton of corn stover per acre, a farmer could generate roughly $33,000 of additional revenue by selling 40% of the corn stover from a 1,000-acre cornfield, while reserving 30% for livestock and 30% for soil health. “Instead of putting all eggs in one basket, distributing them could be more advantageous, not only to address plastic pollution issues, but also to gain extra dollars,” Janaswamy said.

Improving process

The plant biomass consists of three components—cellulose, hemicellulose and lignin. In previous Sun Grant research, the extraction process produced biodegradable film from cellulose extract from corn stover that was gray due to the presence of lignin.

Through the new project, which began in November, Janaswamy reported, “We have been able to remove the lignin and get a pure, white cellulose material from corn stover,” he said. Doctoral student Shafaet Ahmed and master’s students Mominul Hoque and Sajal Bhattarai are also working on the project.

In addition, SDSU agronomy major Jake Larsen of Sioux Falls contributed to the project this summer through the Research Experience for Undergraduates. “Dr. ‘Jana’ provided me with a pulpy cellulose mixture (made from corn stover) and a process, which he anticipated would make a substance close to cardboard,” Larsen said. However, the process produced white cellulose granules from which the research team made a clear film.

“The process turned out better than I expected,” Janaswamy said.

Addressing different feedstock

Now, the team is applying the extraction process to other agricultural byproducts and native grasses. However, the feedstock composition varies, meaning the cellulose fraction process has to be adjusted for each type of feedstock.

“There is not just one solution—they will all be different,” Janaswamy said. In addition, the properties of the films will likely vary based on feedstock type.

“Once we extract cellulose from each feedstock type, we will compare the properties of the films,” he continued.

The films should have three attributes. They should be strong enough to resist tearing, transparent so manufacturers can add any color they wish, and biodegradable. “When you put them into the soil, they should disappear over time–30 to 60 days is the goal,” Janaswamy said.

Once the researchers are able to accomplish these goals, they will go back to the extraction steps and make sure the whole process is economical.