Last Updated: Jul 5, 2021
Our planet is awash with plastic. Since the 1950s, we've produced more than 8.3 billion metric tonnes of plastic globally. And about 60% of it has never gone away. Plastic waste is especially threatening to our oceans, where it traps marine life or kills when ingested. And it's getting worse: A 2020 study by the Pew Charitable Trust estimated that by 2040, plastic released into the oceans will triple to nearly 32 million tons a year. Plastic also damages our environment in ways we can't see. The manufacturing and even the recycling of plastics add tons of CO2 into the air. Most plastics are petroleum-based, continuing our reliance on fossil fuels.
All this has fueled interest in "bioplastics" that use little or no fossil fuels and which – in the best circumstances – will decompose when we're done using them. Research into these products is promising. But the cradle-to-grave journey of that water bottle, or plastic toothbrush, or take-out container is complicated. Unless or until we find a way to dispose of bioplastics wholly and safely, they're unlikely to be the silver-bullet answer to plastic pollution that they're marketed to be. What's more, promoting materials with many of the same bad characteristics as synthetic plastics can distract consumers from the more effective practice of reducing the use of disposable items.
The materials we commonly call "plastic" include various synthetic polymers created by linking together chains of carbon-based units known as monomers. Whether a plastic is hard or soft or flexible or brittle depends on its structure and the types of monomers it contains. Synthetic polymers are typically petroleum-based and highly durable, causing them to remain in the environment for tens to hundreds of years. It's their best attribute and also their worst.
Bio-based plastics, or "bioplastics," are made partly or entirely from biologically sourced materials, which are typically renewable. They may also include some of the same petrochemicals found in synthetic plastics or be structurally identical to them. Some will last just as long in the environment as the petroleum-based plastics they were meant to replace. An example is a bio-PET (polyethylene terephthalate), used for water bottles and packaging.
The environmental benefits of bioplastics depend on what they're made of, how they're made, and how long they remain in the environment. One central argument for bioplastics and other bio-based materials is that their manufacture relies less on fossil fuels than wholly synthetic plastics. That's one reason the US Department of Agriculture promotes their use under its BioPreferred program, which identifies products composed of at least 25% biological materials.
Many of the benefits of bioplastics come with strings attached. Critics of bioplastics derived from food crops like corn or soybeans, for example, argue that their use in plastics diverts these crops from the food supply. They also point out that raising plants for bioplastics poses the same environmental hazards as large-scale agriculture, including pesticides and herbicides. To counter these criticisms, some bioplastic manufacturers use agricultural waste in their plastics. This approach not only puts waste to work but also provides an additional revenue stream for farmers.
Like traditional plastics, the manufacture and shipping of bioplastic products use energy and fossil fuels, even if they themselves are not petroleum-based. And like conventional plastic, bioplastics designed as single-use products eventually end up in the waste stream. And that's where things can get complicated.
Just because a material is made with plants doesn't mean it will return to the soil the way a fallen log in the forest does. To do this, a material – even a bioplastic – has to be specifically engineered to be biodegradable. You can think of it this way: "bioplastic" describes what a material is, and "biodegradable" or "compostable" describes what that material does (or is supposed to do).
Whether plant- or petroleum-based, "Biodegradable" plastics are engineered to be broken down by microbes into carbon dioxide, water, and biomass without exposure to oxygen. The amount of time it takes for a material to biodegrade can vary greatly. So a material could be technically "biodegradable" yet last in the environment for years. Environmental conditions, including temperature, moisture, light, and the presence of specific microorganisms, also influence biodegradability. Some bioplastics do not degrade fully, breaking down into microplastics that are just as harmful as the original material. For example, oxo-biodegradable plastics, which are infused with metal salts to accelerate decomposition, break down into fragments that may contain cobalt, a toxic metal.
Some bioplastics are labeled "compostable." Compostable material (like leaves piled in a yard) degrade in the presence of heat, moisture, and microorganisms into carbon dioxide, water, inorganic compounds and biomass that can be used to enrich soil. Something that's compostable breaks down at the same rate as the elements it is composted with and leaves no toxic residue.
But you can't toss that bioplastic fork on your backyard compost pile and expect it to go away. Even products that have legitimately earned the designation of "compostable" based on government-accepted standards (such as the American Society for Testing and Materials Standards D6400 and D6868) are compostable only in commercial facilities. There are no standard tests at this time to ensure your bioplastic fork is suitable for home composting.
To dispose of these products correctly, check with your local refuse and recycling operation to see it offers composting services. You may also be able to contract independently with a residential composting service that will accept these items along with food scraps and other compostable debris.
Lack of composting facilities and lack of knowledge on the part of consumers means that many compostable bioplastics end up in landfills and incinerators. But the good news is that if widely adopted, commercial composting could reduce the trash sent to landfills and incinerators in the US by 30%, according to the US Public Interest Research Group. And suppose the nutrient-rich biomass it produces is used for agriculture. That would mean that it can reduce the use of chemical fertilizers as well.
The US Federal Trade Commission has issued guidelines for labeling products as "biodegradable" or "compostable." Under these "Green Guides," manufacturers must have scientific evidence that something labeled "compostable" will break down into usable compost in the same amount of time as the materials it's composted with. It should also indicate if commercial composting is necessary and that these facilities may not be available in all areas. Similarly, a product labeled "degradable" needs scientific evidence that the entire product or package will "completely break down and return to nature" within a year. Items typically destined for landfills, incinerators, or recycling facilities should not carry these claims. Canada's Competition Bureau has similar guidelines that also require clarity and substantiation of green claims.
The seal of the Biodegradable Products Institute indicates third-party certification that a product meets standards for composting at a commercial composting facility. Its labeling guidelines also suggest that products carry disclaimers such as "Commercially Compostable Only," or "Facilities May Not Exist in Your Area," to reinforce that they are not designed for home composting.
Some bioplastics can be recycled along with petroleum-based plastics; others cannot. But confusion over labeling means many end up at facilities designed for recyclable plastics, where they can lower the end product's quality. New sorting systems, such as those that use near-infrared technology, may make it easier to identifying bioplastics in the recycling stream. Still, for now, the practicality of recycling them (along with many other kinds of plastic) remains a challenge. Check to see if your recycler accepts plastics with the Resin Identification Code 7 (the number inside the recycling triangle printed on packages), a generic catch-all into which bioplastics fall.
The two most common bioplastics on the market are PLA (polylactic acid) and PHA (polyhydroxyalkanoate). PLA stems from plant sugars and starches, such as those found in corn or sugar cane. PHA comes from microorganisms that react with organic materials. Though both are more expensive than synthetic plastics, PLA is much cheaper than PHA and is used for disposable cutlery and packaging. PHA is also used for packaging, as a coating for the inside of paper cups, and in medical applications.
Bioplastics currently account for only about 1 percent of all plastics. Their market share is expected to grow from $8.3 billion in 2020 to $26 billion in 2027. Non-biodegradable plastics make up more than half of the bioplastics on the market today. That is unlikely to change until new research or regulations yield new materials that don't linger in the environment. Until then, bioplastics will remain at best a partial solution – less polluting than petrochemical plastics, but not quite the environmental answer we've all been waiting for.
We will be following this In-Depth Guide on bioplastics with an article on what cool and innovative steps brands are taking to lessen their reliance on plastic and packaging in general - stay tuned!
Debra Judge Silber is a Connecticut-based journalist who writes on home design with an eye toward practices that support our health and our planet. She is a former editor at This Old House, Fine Homebuilding and Inspired House, and has written for a number of other publications.