Without suitable disposal facilities, compostable plastics are just regular garbage

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Anastasia Elias is an associate dean of research and professor of chemical and materials engineering at the University of Alberta.

Plastics get a bad rap. We have all seen pictures of plastic bags stuck to turtles or piles of plastic waste strewn across a beach. A few years ago, I visited an exhibit at the Vancouver Aquarium featuring plastic waste that author and artist Douglas Coupland had collected from the shores of Haida Gwaii. Small found objects – including toothbrushes, pens and empty tubes – lined the walls of the exhibit, while larger items bobbed in a 50,000-litre tub of water in the centre of the room. After touring the exhibit, I sat down with my family to eat lunch in the cafeteria – salad in a plastic container, with a label indicating that the plastic was, in fact, biodegradable. It seemed like a good compromise on the surface, but as an engineer, it raised a question for me: Is biodegradable plastic really a help to the environment?

Plastics have improved our quality of life immeasurably. They help our food stay fresher longer, and transporting food products and other goods wrapped in lightweight plastics, rather than heavier materials, can reduce not only shipping costs but also the associated CO2 emissions. Plastics also keep things clean while being cheap to produce and convenient for use. In a way, they are just too good – since only around 9 per cent of plastics are actually recycled, we are amassing piles of plastic waste.

To address this problem, Canada recently announced a ban on single-use plastics, which gradually comes into effect in December. Ideally, this policy would work to drastically reduce the prevalence of single-use plastics – which is something we should strive for – but practically speaking, this is difficult to achieve. Engineers have wondered how we can capture the convenience of plastics with alternative materials that won’t leave the same mark on the environment – one candidate is compostable plastic, which breaks down at the end of its lifetime. It’s an enticing vision: You could still order a smoothie in an “eco-friendly” to-go cup, and then toss the cup in the compost after use, where oxygen-breathing (aerobic) bacteria will break the cup down into nutrient-rich soil and CO­2.

There is a problem, though: Your cup may be labelled “compostable,” but unfortunately you can’t just toss it into any compost bin. In both Canada and the United States, in order to meet the requirements to label a material as compostable, it must degrade within a certain amount of time in industrial composting conditions. However, most industrial composting facilities (including those across Canada) don’t even accept compostable plastics; they prefer lawn clippings and food waste, which break down more quickly and – unlike compostable plastics – don’t need to be shredded first. Moreover, for workers in these facilities, screening out plastics would be more challenging if some plastics are allowed but not others. This is the reason that most compostable materials simply end up in landfills where, like food waste, paper and other organic material, they will gradually be broken down by anaerobic bacteria, releasing more harmful methane (CH4) in addition to CO2.

There are strong similarities between compostable packaging and recyclable packaging. Just as printing “recyclable” on a container does not mean that it will actually get recycled, printing “compostable” on a container does not ensure that it will be composted. One of the main drivers of low recycling rates is a lack of demand: It is often easier to just produce new materials rather than to collect, sort, clean and reprocess the old ones. Likewise, it is generally easier to throw things in the garbage than sort them for composting. There are a few exceptions in the recycling sphere: Notably, our system of levying deposits on beverage containers has motivated consumers to sort these materials and return them to depots, resulting in high rates of recycling for these items. Recently, driven in part by public demand, a number of Canadian companies have pledged to ensure their plastics are made of 30-per-cent recycled content by 2025; this expanded market should drive the development of recycling facilities to divert materials that could otherwise end up in landfills.

To get the intended benefits of compostable plastic materials, we need to start building the industrial composting facilities required to process these items in cities across Canada. We must also incentivize producers and consumers to make use of these facilities. Currently, there is a disconnect between material production and disposal – producers and users might be moving toward greater adoption of compostable plastic, but responsibility for waste management lies with local governments who don’t necessarily have the means to dispose of it properly.

One way to quickly make a major impact could be to require large companies who label their packaging as “compostable” to also provide a suitable means of disposal. Fast-food outlets are responsible for a significant amount of plastic waste; requiring or incentivizing these companies to collect and process their waste in a responsible manner could make a significant dent in this problem, while also driving infrastructure development for composting. Small communities, universities, shopping malls and other entities that have some control over their waste streams could implement their own industrial composting systems as well; there is even a variety of small-scale (i.e. barrel-sized to trailer-sized) industrial composting systems available that automate the process.

Scientists and engineers are making tremendous progress in developing new solutions to address the challenges of plastics, including developing new processes to produce biodegradable plastics, designing improved methods and materials for recycling, and engineering production techniques and equipment that help accelerate the degradation of biodegradable materials. Now it is up to us, as a society, to make the decision to implement these innovations on a scale that can positively affect our environment.

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