In my last post regarding the long-term viability of bio-based polymers, I touched on some of the primary concerns we face regarding the rise of plastics labeled as “biodegradable.” It’s an important component of this broad discussion, and one that has become increasingly relevant in an increasingly sustainability-driven product market.

For consumers, understanding what biodegradable really means is crucial to making sustainable purchasing and disposal decisions. Needless to say, marketers and advertisers have confounded this issue, making many consumers believe that the plastic products they are purchasing are more eco-friendly than they really are. I’d like to take this opportunity to address some of this confusion, along with some of the biggest problems biodegradable plastics bring to the table today.

The Word “Biodegradability”

Biodegradability is not so much defined by where the material comes sourced from, but by the composition of the material itself. Today, the consumer products market is dominated by durable petroleum-derived plastics, typically those identified by resin identification numbers 1 through 7. Generally speaking (as each has its own material strengths and weaknesses), these plastics are synthesized because of their versatility and strength, and because they are resistant to natural weathering — a necessity in many products and in product packaging. This holds true for many of the bio-based polymers we currently use as well.

These desirable traits result in highly refined plastics with long, complex polymer chains that are extremely resistant to natural degradation (such as by microorganisms). As this is the case, most of the plastics on the market today are simply not biodegradable, even those sourced from renewable biomass.

How Biodegradable Are Biodegradable Plastics, Really?

But what about the plastics that are labelled by manufacturers as being biodegradable? Here is where most of the confusion arises, as claims of biodegradability are not usually followed by explicit instructions on how to properly make these plastics biodegrade, or how readily biodegradable the plastics really are.

For example, polylactic acid (PLA) is one of the most common so-called “biodegradable” bioplastics used today. PLA is made from corn, so one might assume it biodegrades just like a corn stalk would if left in the environment. Obviously this isn’t the case — only if PLA is exposed to the right temperature and moisture conditions (such as in an industrial composter) will it degrade in any reasonable amount of time. A backyard compost pile just simply wouldn’t cut it.

Bioplastics are often conflated with biodegradability simply due to the fact that they are sourced from renewable biomass. In fact, most of the “green” plastics on the market are not readily biodegradable. Most require processing in an industrial composting facility where the temperature, moisture and exposure to UV light can be strictly regulated. Even in such a facility, some biodegradable plastics can take up to a year to be fully processed. Can you see how the label “biodegradable” is a bit misleading?

Even if the biodegradability of the plastic itself was not a problem, our present recycling, composting and waste-collection infrastructure is inadequately prepared to properly manage more biodegradable plastic. In 2012, the 3,100 composting programs across the U.S. composted 21 million tons of organic waste, while nearly 50 million tons of it still ended up landfilled. There are also only about 150 curbside collection programs for organics (also known as Source-Separated Organics) in this country, and only 100-200 industrial composting facilities. Without seriously bolstering our processing capabilities for biodegradable polymer (and biodegradable/compostable material in general), we’d simply be generating more waste for our landfills and incinerators.

The Future of Biodegradable Plastic

When all is said and done, biodegradable plastic still only makes sense in very limited, short-term circumstances. The reason is simple: Why spend the energy and resources producing highly refined biodegradable plastic polymers, only to completely sacrifice them later through composting or natural biodegradation? As a short-term strategy to reduce waste in markets such as India, it makes some sense; as a long-term strategy to offset our unsustainable dependence on petroleum-derived plastics, it makes no sense.

What the average consumer should take from this conversation is that biodegradable plastics are not the eco-friendly, sustainable alternatives they are often marketed as. Durable bioplastics that can be recycled have far more realistic long-term viability, as we can continue reusing the complex polymers instead of letting them degrade in a compost pile.

Part Three: Why Durable Bioplastics, Not Biodegradable, May Be the Answer ...