Dairy farmers support research into ag plastic alternatives

As Canada continues down the path of phasing out single-use plastic, agriculture must find replacements for everything from bale wrap and silage bags to semen straws and more.

A research team at the University of Guelph, led by Dr. Erica Pensini, is working on finding those alternatives, with funding from Dairy Farmers of Ontario.

Agricultural plastics often contain contaminants that make them harder to recycle, but even if they didn’t, plastics recycling overall isn’t as effective as it could be. Only nine per cent of Canada’s annual plastic waste production is recycled, with the rest going into landfill, waste-to-energy facilities or into the environment, noted Pensini during a recent webinar hosted by Livestock Research Innovation Corporation (LRIC).

Pensini and her team have been exploring different options, starting with a versatile and simple-to-work-with corn protein called Zein. Tested as a spray-on film, it dried rapidly and although it prevented erosion and run-off in the lab, it was less successful in the field. That’s because its tortilla chip-like flavour is also extremely appealing to rodents. 

Adding linseed or tung oil kept the rodents away but also created a rigid bioplastic that can be mixed with natural fibres to make plant pots. It wasn’t flexible enough, however, so researchers mixed it with cutin, a component found in tomato and grape skins. Although this created a water-repellent coating – with the added benefit of repurposing a food processing waste product – the product was hard to make and didn’t meet the level of stretchiness needed for applications like bale wrap. 

This led Pensini’s team to consider using vegetable oils like linseed or soybean oil as the base for a spray-on film but on-farm tests with hay revealed the liquid penetrated the layers and farmer feedback showed interest in a prefabricated film instead of a spray-on product. The resulting modification, although bendy enough for mulch or silage wrap, still wasn’t stretchy enough to be a suitable substitute for conventional bale wrap. 

“So, we mixed epoxidized soybean oil, used citric acid as a hardener, added oleic acid to make it stretchier, and cured it in an oven,” Pensini says. “It’s the best one we have so far in performance. It is flexible and stretchy, but it would need to be fabricated in a dedicated facility.” 

As a next step, the team will be introducing fibres   from crop by-products in an effort to both upcycle agricultural waste products and make them into useful solutions for agricultural applications and lower the cost of alternative plastics. They’ll also be experimenting with other fatty acids to see if they can be used in place of citric or oleic acids to further enhance the new material’s properties. 

According to Pensini, the need to find commercial partners is also important, but conventional plastics will either need to start being phased out or become more expensive before bio-based alternatives will come into widespread production and use.