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The Push for Bioplastics and the Myth of Biodegradability
January 7, 2015
This is the first of a three-part series by TerraCycle CEO Tom Szaky that examines the benefits, risks, misconceptions and long-term viability of bioplastics.
Since the relatively recent rise in conscious consumerism, bioplastics — plastics made from biomass such as plants and algae – have been receiving significant attention. With the bioplastic market projected to grow in the next few years, many are pointing to plant-derived plastic alternatives as the ultimate solution to our unsustainable dependence on fossil fuel-based plastics. But one particular type of bioplastic has recently mobilized a torrent of misinformation, misplaced optimism and confusion: plastics labeled “biodegradable.”
To be clear, most plastics on the market made from fossil fuels are not realistically biodegradable. To actually be biodegradable, a material has to be capable of decomposing naturally through exposure to microorganisms. Some petroleum polymers can be combined with biodegradable additives or other materials to facilitate degradation, but they represent a small portion of the global market. Petroleum-derived plastics don’t exist in nature, and as such there are no microorganisms naturally predisposed to facilitating decomposition (without the help of additives).
Bioplastics are not always biodegradable either, which can be another source of confusion for consumers. For example, Coca-Cola’s PlantBottle simply replaces 30 percent of the ethanol in their normal polyethylene terephthalate (PET) plastic bottle with 30 percent plant-derived ethanol. This means the bottle is still considered PET and can be recycled even though it’s made with some plant material, but it still won’t biodegrade.
Then there are biodegradable bioplastics, one of the most common today being polylactic acid (PLA). Made from corn biomass, PLA does indeed biodegrade into water and carbon dioxide … in the right conditions. High humidity and high temperatures are required to degrade plastics such as PLA, meaning that a PLA cup or bag will only biodegrade with certainty in an industrial composting facility, not your average backyard compost pile. It won’t biodegrade at all buried in a landfill, where it will sit for hundreds or thousands of years like any other piece of plastic waste. Of course, marketers don’t make this clear on the package, and consumers purchase products they believe are more sustainable than they really are.
A Case for Bioplastics
Even with these biodegradability concerns put aside, the large-scale adoption of bioplastics could be great for many reasons. First and foremost is the fact that the required raw materials are renewable; the supply of corn, sugarcane, algae and other bioplastic feedstocks are only as finite as our cultivation capacity, and the plastics industry could finally emancipate itself from its dependence on fossil fuels. Growing feedstock also does not create an energy imbalance when done sustainably, meaning more energy can be derived from the feedstock than is spent cultivating it. If the resulting bioplastic is durable and is recycled, the entire process is incredibly sustainable.
Coca-Cola’s PlantBottle is a good example of how we could do bioplastics correctly given the appropriate infrastructure. Since the bottles are still technically PET plastic, they can be regularly recycled, which preserves the complex polymer instead of resigning it to a landfill where it would sit forever, useless. Assuming we can improve the existing recycling infrastructure, replacing virgin plastic with durable bioplastics in this fashion could drastically reduce the overall demand for virgin polymer.
Why We Need to Be Cautious
Bioplastics bring a wealth of new issues we will have to seriously consider moving forward. First, completely offsetting demand for petroleum-derived plastics with plant-derived bioplastics would require tens of millions additional hectares of agricultural space. Unless we colonize another habitable planet with arable land or significantly reduce our consumption of plastic, this would require seizing farmland already cultivated for food production. The demand for more farmland could even catalyze further deforestation or forest fragmentation, especially in already-threatened rainforest regions such as South America, where the tropical climate is necessary to grow feedstock such as sugarcane.
Even if all the above points weren’t of concern, we still don’t have the proper recycling infrastructure for a higher volume of bioplastic. For example, if a PLA bottle or container finds its way into a consumer’s blue bin, it can contaminate the recycling stream and render the contaminated plastic useless. And forget about actually recycling bioplastics today — as of now, there are no large-scale or standardized bioplastic recycling systems in existence.
Bioplastics Could Be Great
Bioplastics have the potential to be a truly sustainable replacement for petroleum-derived plastics, but only if we do it right. Even if we could limit deforestation and rainforest fragmentation, limit disruption to food production and improve our recycling infrastructure, the only way bioplastics can be a truly sustainable (and long-term) alternative to petroleum plastics is by massively reducing consumption. And as for biodegradable bioplastics — they will never be the ultimate solution some companies claim they can be, regardless of how well the material degrades in a compost pile. Only in limited markets, such as in developing countries with a lot of organic landfill waste, do biodegradable plastics make sense (short-term) at all.