From citrus fruit peels to used cooking oils, organic waste is the key ingredient to producing sustainable plastics.
Quick, what’s the first thing that comes to mind when you hear the word “polymer”? For many, it would be plastics.
Since they were developed in the early 20th century, plastics have woven their way into every facet of modern life. From your toothbrush bristles to your pyjamas and your smartphone, plastic is ubiquitous and essential to almost every moment of our 21st-century existence.
There lies the problem: our well-being has become intimately connected with synthetic polymers that are largely based on oil, a non-renewable resource whose waste products cause severe environmental damage. According to the United Nations Environment Programme, more than 299 million tonnes of plastic were produced worldwide in 2013 alone, costing more than $13 billion in damage to our shared marine ecosystems. Less than one-tenth of the plastic we use—in our cars, computers, food packaging, clothing and paint—is recycled.
Is there a way out of this mess we have created? “Absolutely,” insists Marc Dubé, professor and vice-dean (research) in the Faculty of Engineering. “The key is to remember that while petroleum-based plastics are polymers, polymers don’t have to be petroleum-based plastics!”
Nature is in fact filled with naturally occurring polymers, from the polymers of nucleotides that make up our DNA to the polymers of saccharides (polysaccharides) that form the cellulose of trees and other green plants.
In the pursuit of more environmentally friendly alternatives to petroleum- based polymers, Dubé has applied the lens of green chemistry to his three decades of experience in chemical engineering to focus on turning organic wastes into useful, sustainable polymers. From citrus fruit peels to wood waste and used cooking oils, Dubé’s sustainable polymer reaction engineering research group is transforming biomass waste into almost limitless options for greener polymers.
The challenge is to synthesize new polymers from renewable materials and to design sustainable polymerization processes that are more hydrophilic, or water-loving. Petroleum-based polymers tend to be hydrophobic, which is one reason why they don’t break down easily.
“The key ingredients are renewable monomers such as glycerol from cooking oil, limonene from citrus peels and other natural derivatives that replace petroleum-based monomers,” explains Dubé, recipient of the 2017 G.S. Glinski Award for Excellence in Research from the Faculty of Engineering. “I want to make useful polymers more efficient while using less energy, and eliminate leaching of toxic chemicals when they are retired to the landfill. Then we will really be heading into a greener future.”
Dubé is in a unique position to tackle the sustainable polymer challenge systematically and holistically as he can look at it from both a polymer chemistry and a polymer engineering angle.
“There is not a single approach for the transformation of polymerization processes into more sustainable ones,” he says, “but rather a coordination of several steps can result in an environmentally friendly polymerization process.”
From water-absorbing hydrogels used in baby diapers to antibacterial bioadhesives for surgery to “smart” polymers that can respond to electrical signals, Dubé’s research group is spearheading sustainable polymer innovation in Canada and finding cleaner ways to make a group of products we can’t live without.
by Sean Rushton