What are bioplastics, and can they solve our pollution problem?

Polymers from plants may not offer a perfect alternative

The plastic products that we can hardly live without have a dirty secret: More than 99 percent are made from fossil fuels. One solution to our petroleum-fueled pollution problem could be using less harmful ingredients in our everyday products. Bioplastics, which are materials made from already mass-produced plants like corn and soy, could replace the conventional varieties that fill our daily lives, and could prove easier to break down and compost.

But in reality, nature-based plastics may not live up to their lofty promises—and it’ll take major policy and industry shifts to wean us off petroleum-based plastics.

What are bioplastics?

Bioplastics, also known as biobased polymers, are plastic-like materials made from plants like corn, sugarcane, wheat, and potatoes. They can also be made from recycled food waste, like banana peels and coffee grounds. They’re therefore often (but not always) biodegradable, meaning that they can be broken down by living organisms like bacteria and fungi.1 Bioplastics can be used for similar applications to their petroleum-derived counterparts, such as packaging, cutlery, electronics, and medical equipment.

The term bioplastics, however, can be misleading. The word is sometimes applied to fossil fuel-based plastics that are advertised as biodegradable, such as the polybutylene adipate terephthalate (PBAT) often used to make packaging and cutlery. These materials don’t count as bioplastics because they aren’t actually made from natural, renewable sources.

Bioplastics emerged around a century ago, when Henry Ford experimented with car parts made from ingredients like soybeans and wheat in the 1940s. But it wasn’t until the last decade that they started popping up in widely used consumer products, including Coca-Cola bottles, as well as the straws, to-go containers, and disposable cups

They’ve also been slowly making their way into fields such as medicine, agriculture, and electronics. Since the early aughts, carmakers have even added some bioplastic—take Mazda’s 2007 announcement of what it called the world’s first plant-fiber based “biofabric” for vehicle interiors. A decade later, Toyota incorporated starch- and castor oil-derived plastic into its navigation system screens.

Right now, bioplastics only make up less than 1% of global plastic production, in part due to high production costs and technical limitations.23 But regulators have a lofty vision for bioplastics: This past March, President Joe Biden announced his aim to replace more than 90 percent of plastics with nature-based materials over the next 20 years.

To bring more bioplastics to the masses, researchers have been looking into ways to make them tougher and more durable while simultaneously easier to compost or recycle—which is no easy feat.4

How are bioplastics made?

Bioplastics are generally made with the help of chemical reactions by enzymes or processed with heat or machinery, explains Atanu Biswas, a chemist at the National Center for Agricultural Utilization Research. These enzymes encourage natural materials to form sturdy chemical bonds and transform into the polymers that make up plastic.5 

“Bio-based polymers are gaining momentum and should be part of the portfolio to reduce the environmental footprint of human activities and to create a sustainable society.”

Rafael Auras, professor, Michigan State University

Last year, a type of bioplastic called PLA or polylactic acid, made up the largest share of bioplastics production, or around 20%. This was followed by bioplastic blends made with starch, which composed nearly 18%, along with the “bio” version of the fossil-fuel based polyethylene at nearly 15%. 

What are the most common types of bioplastics? 

Bioplastics are typically categorized based on their source—that is, what material they’re made of. Each source of bioplastics comes with its pros and cons. Some argue, for example, that it doesn’t make sense to take up acres of land to grow crops like corn just for plastic. This could change as the industry grows, but researchers are also working on ways to turn already-plentiful materials into plastic. Some are looking, for instance, at food waste, while others are considering plants like seaweed that are already growing in the wild and don’t require enormous farms on land.

Protein-based bioplastics

Protein-based kinds of plastic, which scientists hope can be used in edible packaging, are often made from plant proteins like wheat gluten and soy.6 Some others, however, come from animal proteins such as whey and gelatin. These can be mixed with alcohol and heated or treated UV with light to create hardy final products. In 2016, for instance, scientists at the USDA created a film with a protein made from expired milk that can keep packaged foods fresher for longer compared to petroleum-based plastic. But once these protein-derived plastics make their way into the environment and our bodies, researchers aren’t yet sure whether they could have toxic impacts.7 

Monomer-based bioplastics

Other varieties of bioplastic, known as monomer-based, start as simple molecular units from plants. To make petroleum-based plastics, factories force monomers (the basic units that make up polymers) to bond together into polymers by applying heat, pressure, and chemical reaction-spurring compounds called catalysts. 

The process works somewhat similarly for nature-based monomers. For example, fermenting sugar from plants like corn results in a substance called lactic acid. Lactic acid can then be attached to catalysts and heated to bind the molecules. Those molecules then go on to become PLA, which is used in stuff like food packaging, textiles, and toys.8

Starch and cellulose-based bioplastics

Bioplastics from natural polymers like starch and cellulose, a fiber found in plants’ cell walls, have also popped up in research and in products like packaging and electronics. To make them, starch and cellulose are commonly extracted from plants and blended with other bioplastics like PLA to improve water resistance and durability.9 Going forward, seaweed could serve as a helpful source of cellulose in these products. 

Microbe-manufactured bioplastic

Some bioplastics are concocted by tiny organisms. Microbes, including certain types of bacteria and algae, create polyesters called polyhydroxyalkanoates (PHAs) to store carbon and energy. The same E.coli bacteria that makes people sick can even be engineered to churn out polyesters.10 Scientists have pointed out how a polyester in this category called polyhydroxybutyrate (PHB) could be engineered to compete with the popular petroleum-based polymers polypropylene and polyethylene.11 Unlike these materials, PHB is non-toxic and could break down more easily in certain environments. 

While it’s expensive to make most types of bioplastics, PHAs are particularly pricey: Production costs more than six times more than traditional plastics.12 So they’re not widely used commercially, but have found their way into food packaging and utensils, along with medical applications like implants and artificial skin.

Fossil-fuel copycats or ethanol-based bioplastics

There are also “bio” versions of widely used synthetic plastics like polyethylene and polypropylene.13 These types of plastics have comparable properties to their fossil fuel counterparts because they share similar chemical structures. Bio-polyethylene can be created by dehydrating ethanol derived from sugar cane, sugar beets, and wheat grain. The petrochemical company Braskem currently operates the world’s first industrial-scale “green” ethylene plant in Brazil, where it produces more than 200,000 tons of the product annually. Despite its relatively widespread production compared to other bioplastics, bio-polyethylene comes with a caveat: Like regular polyethylene, it’s not biodegradable.14 

What are some common applications for bioplastic?

Bioplastics are used for all sorts of products, but nearly half make their way into packaging. Other popular uses include fibers and consumer goods like electronics. Today, PLA is mostly used for food packaging.15 Bio-polyethylene, another heavy hitter, is found in items like food packaging, bags, and cosmetics. PHAs are also currently used to make food industry products like cups, containers, and trays, but at the moment they tend to be costly and tricky to manufacture.16 

What are the advantages of bioplastics?

Advocates claim that bioplastics can cut down on plastic waste and greenhouse gas emissions. They also say that the materials break down more easily and quickly than their synthetic cousins. Since they can be made from renewable resources and replace polymers sourced from fossil fuels, they could theoretically reduce the greenhouse gas emissions associated with the plastic industry.17 

The bioplastics industry may need to usurp up to 5% of all arable land to make a significant dent in conventional plastic pollution, according to a 2013 study.

Bioplastics are also made with fewer toxic ingredients then their counterparts, as well. Traditional, fossil-fuel based plastics use harmful chemicals in the manufacturing process to make them tougher, like BPA and phthalates, which can have dangerous health effects for people and animals. “Bioplastics made from agro-based materials usually have less of this type of problem,” says Biswas of the National Center for Agricultural Utilization Research. “Some plant components may exhibit toxicity, but the common ones (at least for food use) are mostly known.”

What are the disadvantages of bioplastics?

Currently, bioplastics can’t compete with their fossil fuel-derived cousins in terms of price and accessibility. They’re expensive to manufacture, says Rafael Auras, a professor specializing in packaging sustainability at Michigan State University. Bioplastic production can cost five to ten times more compared to fossil fuel-derived processes.18 

Plus, bioplastics don’t have all the convenient properties of conventional polymers like polyethylene and polypropylene. For example, bioplastics aren’t typically as strong, durable, and resistant to high temperatures.19 And some of the most sustainable bioplastics, like those made from starch or plant protein, have a limited shelf life, Biswas points out, because they’re particularly good at breaking down.

Do bioplastics leave microplastics?

While they’re not made with certain harmful substances used to produce conventional plastics, bioplastics may also release microplastics and potentially harmful chemical additives into surrounding ecosystems, risking harm to people and wildlife. In fact, PLA was found to release higher levels of microplastics in lined cups than the conventional plastic polyethylene. It’s possible that bioplastics shed microplastics more quickly than conventional plastics, but scientists haven’t fully grasped the phenomenon yet.

How do you dispose of bioplastics? 

Researchers are still figuring out the best way to get rid of single-use bioplastics once we’re done with them. Depending on the variety, they can be recycled or even biodegrade in nature—but there are still questions abound about what this looks like for people and the planet. 

Are bioplastics biodegradable?

First, let’s consider the term biodegradable. Experts consider certain bioplastics biodegradable if microorganisms can turn them into carbon dioxide, water, methane, and compost. But you can’t just rely on your backyard bin. Most biodegradable bioplastics must be composted in an industrial facility because they require high temperatures to get the job done. Still, they’re often mistakenly sent to recycling centers where they can contaminate other plastics and mess with the overall recycling process.

How long do bioplastics take to decompose?

It can take anywhere from a few weeks to months to years, depending on the variety of bioplastic and its specific fate.2021 But in the best-case scenario, the bioplastic can be broken down quickly with minimal energy input. Some experts think facilities should unleash plastic-hungry enzymes from microbes like fungi and bacteria, which can feed on bioplastics as a source of carbon and energy, for a more sustainable solution

Do bioplastics decompose in landfills?

Bioplastics do decompose in landfills, but in these dense, oxygen-free environments, that’s not a good thing. In landfills, bioplastics are broken down by tiny organisms and can release methane, a powerful greenhouse gas with at least 25 times the heat-trapping power of carbon dioxide in the atmosphere.22 So it’s best to treat them in proper composting facilities, but few cities have these right now.

Do bioplastics melt in water?

When bioplastics make their way into oceans, they could take just as long as fossil-fuel derived plastics to disappear, potentially leaving microplastics and toxins behind.23 But research has brought seaweed- and spirulina-based plastics into the spotlight.2425 These materials would likely prove much easier to degrade in water and personal compost bins because they can break down as easily as organic waste like banana peels and can naturally degrade in the ocean. 

Can bioplastics be recycled?

To reduce the environmental impacts of bioplastic, some scientists argue that these products should head straight to the recycling bin. Yet this is no simple task. Only certain kinds of bioplastics (specifically “BioPET” and “BioPe”) can be recycled, and experiments have shown that some tend to lose strength and quality after mechanical recycling.26 We also don’t generally have large-scale bioplastic recycling facilities in the United States yet, but future operations could employ tiny organisms like bacteria to help separate these products back into their useful building blocks.27

Are bioplastics better than plastics for the environment?

Bioplastics aren’t necessarily better for the environment than plastics—at least right now. While companies now use only a tiny portion of the world’s land for bioplastic ingredients like corn and sugarcane, this industry may need to usurp up to 5% of all arable land to make a significant dent in conventional plastic pollution, according to a 2013 study.28 

Farming these crops can also require fertilizer, pesticides and herbicides, which can contaminate surrounding soil and water, as well as release carbon dioxide by converting forests and grassland to new cropland.  “Even though there is much less carbon dioxide produced during the production of bioplastics, there is still a product footprint left behind,” Biswas says. “However, even when you consider all these factors, bioplastics are much better for the environment.”

Are bioplastics a viable replacement for traditional plastics?

Research teams have already made lots of progress in engineering better products that can both last longer and have less of an environmental impact compared to traditional plastic. But it’s likely up to businesses and governments to keep the ball rolling by scaling up specialized recycling and composting methods, according to Auras. “It will be hard, and it will depend on the economics and incentives,” he says. “Something that it is certain: Bio-based polymers are gaining momentum and should be part of the portfolio to reduce the environmental footprint of human activities and to create a sustainable society.”

To make a real impact on plastic pollution, it’s likely best to end our love affair with single-use products before they make their way to landfills, oceans and our bodies.

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