The Risks of Single Use Plastic Alternatives

CC BY 2.0. Ana M., winner NOAA Marine Debris Program Art Contest

As the war on plastic heats up, both users of convenient disposables and suppliers of plastic products are looking for alternatives. But could the substitutes be worse?

In spite of the number of people (and companies) saying "no straw please," global plastic manufacturers are enjoying a booming business, with growth rates of 3.9% in 2017, 4.0% in 2016 and 3.5% in 2015. In 2016, the worldwide market reached 335 million tons worth of plastic materials and other plastics (not including some plastic fibers). In some cases, plastics remain beneficial: their reduced weight and technical properties make them the best choice for their purpose. Plastics may even benefit the environment - think lighter cars = less fuel consumption for example.

But increasing publicity of the ocean "smog" and other devastating effects of plastic waste, and continued pressure from major companies will drive demand for equally convenient and not too costly alternatives. The easy choice is new forms of plastics that promise to conveniently disappear after use.

Plastic alternative 1: Biodegradable plastic

Biodegradable plastic sounds like a win-win. We get all the convenience and return the waste to the earth after use. But don't get lured in by the Utopian promise of this concept.

Biodegradable plastics typically consist of starch or fiber based polymers, using corn, potatoes, or soy as raw materials. They are biodegradable according to a standardized test method in which materials are tended in a moist, warm, and aerobic environment. If they break down 60% or more in 180 days, they pass. But these test conditions in no way represent the end life of most single use plastics. In litter or landfills, this plastic stays around for a long time.

Even worse, these plastics put the entire compost system at risk. Incomplete degradation can result in residuals that contaminate the compost, making it unsuitable to be reused for its fertilizing value. And even if the degradation is complete, these bags break down to just carbon dioxide (released to the air) and water. Unlike compost of natural vegetable wastes, there is no nutrition there to return to the soil.

Finally, more biodegradable plastic is required to serve the same purpose as conventional plastics, because these new polymers lack the same strength. For example, if a supplier wants to ensure the groceries don't break their bag, they need to produce bags with thicker walls.

Plastic alternative 2: Plastic with additives promoting break down

The most common of these products goes under the names oxo-degradable plastic or oxo-biodegradable plastic. Hydro-biodegradable and thermo-biodegradable plastics operate on similar principles. These plastics contain additives that are activated by environmental conditions (oxygen, moisture, or heat) and react to break up the long polymer molecule chains. It is the length of polymers that make them so difficult for microorganisms to eat, so once the molecules are broken into smaller pieces, normal biodegradation processes can take over.

But the additives that break down plastics at their end of life are precisely those additives that should not be returned to the recycling stream. To make matters worse, consumers have a hard time differentiating normal plastic that can be recycled from alternative plastics that can lower the quality of the recycling stream output.

These alternative, more biodegradable plastics may be appropriate for specific purposes, but they should not be simply plugged in as a replacement for conventional plastic. And where they are put to use, there needs to be provisions to mark the special type of plastic for separation and ensure the availability of an appropriate recycling stream.

The bottom line is: if we don't want to live in a a sea of plastic waste, we need to make smart and sustainable decisions about how to substitute the single use plastics so prevalent in modern life. There is no easy way out on this one.