U of G team trying to develop biodegradable agriculture plastics

Research at the University of Guelph aims to perfect a biodegradable film that could eliminate the need to find a recycling market or contribute to landfill waste for plastic bunk silo covers and horticultural mulch.

The work is being led by associate professor of engineering Dr. Erica Pensini with collaboration from Prof. Alejandro Marangoni in the food science department. The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) has provided funding, as have Beef Farmers of Ontario and Dairy Farmers of Ontario.

Why it matters: The development of effective biodegradable options for agricultural plastics has potential to significantly decrease a farm’s environmental footprint.

Pensini began her on-farm experiments in 2020 using corn oil combined with an oxidizing agent and water to create a spray-on product applied on a small scale to portions of bunk silos. The corn-derived product proved impractical because it attracted hungry rodents.

“It smells like pizza,” she joked recently when telling Farmtario about her work.

In 2021, they tested other readily obtained edible oils including canola and peanut. They have also been working on applications for vegetable production as a soil-heating and soil-cleansing mulch. These oils have passed the vermin test, but no one type has emerged as the front-runner.

So far, all work has been done with a spray-on product, which pleases some participating farmers. But others expressed interest in a pre-fabricated covering or mulching film similar to non-biodegradable plastic products already on the market. Pensini says the team hopes to explore the pre-fab version this year.

The oxidizing agent — the most effective so far has been oleic acid — serves to harden the biofilm once it is exposed to air. In on-farm trials, Pensini’s team typically mixes the oil with water, adds concentrated vinegar to initiate a solidifying reaction (similar to adding vinegar to milk to create sour milk), then adds the oxidizing agent.

For the spray-on version in the team’s small-scale trials, common hand-held sprayers have worked well.

Pensini noted there are biodegradable plastics already on the market, but not for the agricultural applications she’s exploring. These plastics are derived from biological-based, renewable materials but they typically have to be processed under controlled conditions to fully biodegrade. You can’t put them in a compost pile or solid manure pile and have them break down.

The product being trialed by the U of G team is biodegradable under less controlled conditions. And it’s harmless to cows if they eat it.

In addition, a lot of biodegradable plastics provide full or sometimes only partial resistance to moisture for a short time but soon break down enough that silage or soil would be exposed to moisture and air. The biodegradable films her team is working on, she explains, must remain impermeable for an entire season or perhaps longer.

She compares creating a biodegradable product similar to an apple core versus a product like a walnut shell. “If you created something like an apple core, it wouldn’t be very useful.”

Pensini expects the final product will differ from what farmers use now, so there will be an adjustment period if the biodegradable film is commercialized. During last year’s testing, using the spray-on product on different farms, it was clear the product will retain a wet look for some time after application.

“We’re trying to speed up the drying process so it is impermeable right away,” Pensini said, but the wet product’s appearance may take longer to change.

She predicts that prices for nonbiodegradable plastics will rise as countries around the world increase their participation in programs aimed at lowering carbon footprints.

“Plastics are not priced properly,” to reflect the true environmental costs of their production, she said.

“What is considered cheap now… isn’t going to be cheap or even possible to produce in the future. There are going to be some very big changes like what we’ve never seen before,” she said, meaning bio-based alternatives to oil-dependent products will become more attractive in all sectors, including agriculture.

Farmers interested in having biodegradable agricultural plastic tested on their farms can contact Erica Pensini by email or at 519-824-4120, ext. 56746.