In the lead-up to phase 1 of Canada’s single-use plastic ban later this year, a lot of confusion has surfaced about which things are ‘compostable’, and which things are not.

Most of the confusion has to do with bioplastics, which are (in their current formulation) made from a plant-sourced compostable product known as Polylactic Acid, or PLA (acide polylactique).

 

Here are some of the questions we’ve encountered recently:

 

‘Are PLA Products Really Compostable?’

Even though many PLA products have been third-party certified as compostable, some folks still seem unsure. Having faced a lot of greenwashing over the years, a healthy skepticism is more important than ever! But when people begin to doubt that a certified compostable product is truly compostable, we have to ask: ‘Just what’s going on here?’

The confusion seems to stem from unclear messaging from municipalities as to what is accepted in their organic waste collection program. In addition to this, consumers have heard reports of compostable plastics winding up in landfill, and have in some cases concluded that PLA is not compostable. This, of course, is not the case at all. 

To understand what’s going on it’s essential to know more about where organic waste bins go for treatment once they are collected. This can be a tricky task, as the answer seems to differ everywhere -- and can in fact even differ from zone to zone inside of the same city!

Here’s an easy rule of thumb: If your city sends organic waste straight to a composting facility, chances are that PLA is accepted in your community’s organic waste collection. If the organic waste goes to an Anaerobic facility first for a process known as Biomethanization, chances are that either your city states that PLA is not accepted, or they neglect to mention PLA in their messaging at all.

One way or the other: Yes, PLA really is compostable. It was made to be composted, and when composted, breaks down into carbon, hydrogen, and several other non-toxic byproducts. Some PLA products (like our compostable mailers) are now even certified for home composting in Europe, while most require the heat of a commercial or ‘industrial’ compost pile to break down. 

It gets tricky though, if the organic waste collected in municipal programs make other stops along the way - before it arrives at the compost site.

 

‘How does municipal composting work?’

Organic waste that is diverted from landfill must be sent for processing, and the design and technique used in their facilities can vary.

Many municipalities have opted directly for composting, a model of resource management that is pretty straightforward: The organic waste collected from businesses and residences is turned into compost, which is used to restore and maintain agricultural soils.

Throughout the composting process, the combination of temperature, humidity, and microbes work together to break PLA down into carbon, hydrogen, and several other non-toxic byproducts.

This is the process that allows PLA to be tested and certified as compostable.

 

If PLA is compostable, why do some cities say they don’t accept it in their collection? 

Some larger municipalities have chosen to include a stage in their process in which Anaerobic Digestion systems are used to force the production of methane from the organics prior to composting. The methane produced is captured, treated, sold as a type of renewable natural gas - a treatment strategy known as ‘Biomethanization’.

When Biomethanization was first introduced as a treatment strategy, there were suggestions that composting may no longer be necessary. It was proposed at that time that the organic material that remained at the end of the methane extraction - known as ‘digestate’ - could be applied directly to agricultural fields as a benign by-product.

Studies quickly showed that such a practice would not lead to positive environmental outcomes, so compost facilities were drawn back into organic waste treatment strategies as a secondary stage that would treat the digestate.

In certain municipalities, therefore, organic waste first goes to a Biomethanization facility, after which the resulting digestate is sent - post methane-extraction - to a compost facility, where the material is then made safe for use in agriculture.

If ever there were still to be a PLA product contained in the digestate upon its arrival to the compost site, the process of composting this organic material would still break the PLA down into carbon, hydrogen, and other non-toxic by-products. In such a scenario, the PLA would have been composted, and would still meet the requirements of being certified compostable. 

However, because AD facilities use equipment that is not generally designed to handle items that ‘behave like plastic’, PLA is considered a contaminant in the Biomethanization process. This has led municipalities that use this process to prohibit PLA in their organic waste collection programs.

 

What’s the solution?

In spite of its shortcomings -- (which we’ll get to soon) -- PLA products continue to occupy a pivotal role in the development of bioplastics, which will both allow the capture of greater amounts of food waste, and also reduce the use of petroleum plastics.

At the same time, capturing methane gas from organic waste presents a compelling case for reducing fossil fuel use to generate electricity. Is there a cost-effective adjustment that could be made to municipal treatment strategies so that both technologies may continue their development and contribute to the quest for sustainable consumption and best practices?

We are certain to soon find out, as international expertise and discourse continues to build in these areas.

 

How do I compost PLA products where I live?

Compostable.ca was developed as a project of Compost Montreal, a best-practices organic waste collection company that continues to collect and compost PLA every day. In addition to Compost Montreal, there are many other collection companies across the country that accept PLA products for composting.

In the coming months we will provide more information about collection and composting options for PLA across the country. We invite you to get in touch with us if you’d like to know more about what your community does to treat its organics once they’re collected.

And if you know of other collection companies that collect PLA for composting that you’d like everyone to know about, we’d love to hear from you!