Solid Waste & Recycling


Compostable plastic bags enter the market

Iremember as a youngster flipping through my father's Popular Mechanics magazines and every once in a while seeing the cars of the future. Gleaming, sleek and spaceship-like, the cars ran on electrici...

Iremember as a youngster flipping through my father’s Popular Mechanics magazines and every once in a while seeing the cars of the future. Gleaming, sleek and spaceship-like, the cars ran on electricity, some without wheels; everybody had Jetson hairstyles and aluminium foil clothes. Like the mini-Ice Age forecasts made at about the same time, we’re still waiting. Some things just take time.

Compostable plastics (bags) have a similar history, yet it appears that the convergence of promise and technical reality is truly upon us. When large companies like Glad enter the scene, it’s clear that promise and potential have been converted into the marketplace.

The critical hurdle of a scientifically-defensible certification program was traversed some years ago by the Biodegradable Product’s Institute (BPI) ( Its certification program and seal is the current go-to program for Canadian municipalities and provinces. More recently, the Bureau de Normalisation (BNQ) — part of the Standards Council of Canada (SCC) — developed a Canadian protocol.

The BNQ’s compostable plastic pags protocol essentially takes the same approach as the BPI process and includes metal concentration requirements (which have been adopted by the BPI). This “Canadianization” of an existing process has led to two high quality (but essentially identical) certification programs. Manufacturers have to get their products certified twice. The similarity of the two programs suggests that one common North America-wide certification program would suffice.

The promise of this product — a truly “compostable” bag -took a long time to materialize because of the many different types of “degradable” plastics that have been developed. They have “sciencey” names like oxo-degradable, photodegradable, water soluble and even biodegradable. Even though these types of plastics may eventually degrade, they have no place in a composting system because they take too long to break down and/or they introduce lingering contamination into the compost.

Because ordinary people aren’t all that “sciencey” they get pretty confused and everything that sounds like it breaks down or is “green” is all the same to them. It’s key and critical that a degradable plastic be compostable. In simplest terms, this type of plastic must compost (i. e., break down from the actions of compost bacteria) during the normal composting process, and leave no residue prior to product sale.

GTA experience and initatives

The advent of the City of Toronto’s source separated organics (SSO) composting program introduced the concept of allowing liners to be used in the kitchen containers used to collect SSO in the household. The thinking was that this would stimulate participation and increase the capture rate of SSO. York Region followed suit and essentially mimicked Toronto’s program.

The programs, while successful from a participation and capture rate point of view, generate a considerable amount of (mostly plastic) residue. This non-degradable plastic can be removed and the SSO can produce good quality compost. However, the 20 to 30 per cent contamination rate may have given other municipalities pause as they developed their SSO programs. To the east and west, municipalities have introduced SSO composting programs that do not allow non-degradable plastic bags. Most of these municipalities have allowed for the use of “compostable” plastic liners.

The Region of Peel has a fully launched and operational composting program. Only the use of BPI-certified compostable plastic bags (and paper bags) is allowed in this program. It has taken a concerted effort to wean residents out of using ordinary plastic bags.

“We used a phased approach to help our residents understand what types of bags are and are not acceptable,” says Dave Gordon, Peel’s Manager of Waste Planning. This included an extensive awareness campaign. The Region delivered plenty of “carrots” — collecting carts with plastic bags but informing and educating residents with stickers and sample compostable bag product. Eventually the “stick” appeared and carts with non-compostable plastic bags were no longer collected and stickered (even if they contained carrots!).

“There was a long education process,” continues Gordon. “Initially a lot of calls came to the call centre but eventually these subsided.

“We’ve noticed a difference at our processing facility and we are not seeing much plastic. We currently estimate that only 5-10 per cent of residents continue to use non-compostable plastic bags, down from an estimated 35 per cent.”

The trend for municipalities has very clearly shifted to ban non-compostable plastic bags and to allow BPI certified compostable bags in composting programs.

The frustration with products masquerading as compostable led to a cooperative initiative by Peel, Halton, Durham and Niagara Regions as well as the City of Hamilton to form the “Joint Municipal Initiative for Compostable Liner Bags-Organics Recycling Programs.” This work culminated in a February 2008 letter to retailers requesting that they stock certified compostable liner bags in their stores and that these liner bags be BPI certified.

It seems that compostable plastic bags have become a permanent fixture in composting programs after a rather arduous journey. They offer some members of the public the extra convenience they need to participate in their SSO program. There is nothing magic here. They hold the waste just like a regular garbage bag, but then, at just the right time (hopefully) they disappear.

Paul van der Werf is president of 2cg Inc. in London, Ontario. Contact Paul


The trend for municipalities has very clearly shifted to ban noncompostable plastic bags and to allow BPI certified compostable bags in composting programs.

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