What is the future of bioplastics?

Could you imagine using biodegradable plastic? Bioplastics may help make that possible. See more green science pictures.
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Bioplastics -- that is, plastics derived from plants -- have the potential to alleviate some of the long-term pollution problems caused by conventionally made plastics. From manufacturing processes that release less global warming related pollution to the ability to biodegrade, bioplastics seem environmentally friendly. However, bioplastics are currently more expensive than standard plastics, and they might not be as eco-friendly as they seem.

What's the difference between bioplastics and regular plastics? Most plastics are made through petrochemical processes. In other words, they start out as the chemical byproducts of oil refining, which are turned into a variety of plastics through chemical processes that form long molecular chains known as polymers. These polymers give plastics their structure. You can find out more details on the manufacture of petrochemical plastics in How Plastics Work.

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Bioplastics, on the other hand, are derived from plant-based sources. They can be made from cane sugar, corn, or from plant byproducts like wood bark and corn husks. Pepsi is even trying to incorporate potato and orange peels into the manufacture of bioplastics [source: de Guzman]. Switchgrass is another great source for bioplastics – it grows pretty much anywhere, is drought resistant, and grows quickly. Since it isn't a primary food source, using it for bioplastics won't affect food prices.

You may have heard that bioplastics are biodegradable, but this isn't necessarily true. The term bioplastics refers to the plant-based manufacturing method. Some types of bioplastic are biodegradable, some aren't. Some bioplastics will degrade in your home compost bin, while some require industrial composting. In fact, many bioplastics won't degrade at all if placed in a landfill with other garbage.

With so much potential, yet so many challenges, what does the future hold for bioplastics?

Potential Uses for Bioplastics

Bioplastics are most frequently used in packaging, although bioplastics could potentially be used in any way that regular plastics are used. The performance characteristics of bioplastics and petrochemical plastics are very similar. There have been situations where bioplastics had to be reformulated to deal with performance problems, such as insufficient shelf-life, or those infamously loud Sun Chips bags. (When Frito-Lay debuted compostable chip bags in 2010, customers complained that the bags were too noisy. A reformulated, quieter bag was later developed.)

Coca-Cola's PlantBottle program makes plastic beverage bottles that are 30 percent plant-based. The bottles are made from polyethylene terephthalate (PET), the exact same plastic that comes from petrochemical processes, but 30 percent comes from Brazilian sugar ethanol. The mono-ethylene glycol that results doesn't change the final chemical formulation of the plastic. However, it was created from a renewable resource (sugar cane) instead of from fossil fuels. The bottles aren't biodegradable.

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PET plastics sources from plants are also used by Toyota in the manufacture of some interior trim components and by AT&T for cell phones cases and other accessories [source: de Guzman].

Another form of bioplastics is made from polylactic acid (PLA). It's used in a variety of packaging products and even in clothing. However, it has a low melting point, so it can't be used with hot foods or liquids. It's biodegradable in the presence of oxygen, which means it won't degrade in a landfill.

Next, we'll talk about the challenges bioplastics face.

Challenges Facing the Bioplastics Industry

Bioplastics may seem like an eco-friendly taste of the future, but they aren't perfect. Yet.
Bioplastics may seem like an eco-friendly taste of the future, but they aren't perfect. Yet.
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Bioplastics seem to have many benefits, but they aren't the perfect eco-friendly product we might hope for. For one thing, they're more expensive than petrochemical plastics, costing between 20 to 100 percent more [source: Dell]. The industrial processes for making petrochemical plastic have been in place for decades, so the production chain is very efficient. Large-scale bioplastics programs like Coca-Cola's should eventually lead to similar efficiency.

Bioplastics also have problems at both ends of the production cycle. While manufacturing bioplastics may not result in the same fossil fuel emissions as petrochemical plastics, the use of fertilizer and pesticides and conversion of forests to agriculture to manufacture corn or sugar cane counterbalances the benefit [source: Marshall]. Coca-Cola has tried to minimize this impact by relying on Brazilian sugar cane, which is primarily produced on degraded farm lands a long distance from the Amazon rainforest [source: Coca-Cola]. Advances in the use of cellulosic plant products (like corn husks and similar materials) would also reduce the environmental footprint of bioplastics.

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Biodegradability and recycling are problems for bioplastics too. It turns out that making consumer plastics biodegradable actually has negative effects on the environment. The first problem is that there are a lot of different types of biodegradability. Some bioplastics biodegrade with oxygen and ultraviolet radiation, so litter left out in the sun will degrade. However, it doesn't completely decompose, the process takes years, and it releases toxic chemicals. Some plastics are designed to biodegrade when composted, and this doesn't do any good if the consumer doesn't compost. Only a few types will compost in a back yard compost bin, in any case. The rest require industrial composting processes. This results in a lot of confusion for consumers. Worse, decomposition of bioplastics releases methane, which is a more harmful greenhouse gas than carbon dioxide.

Worse, it's very difficult to tell bioplastics from regular plastics. If a small amount of PLA plastic is accidentally mixed into PET plastics in the recycling stream, the resulting recycled plastic products will have lesser quality and value [source: PRO Europe]. In other words, you'd have to separate each type of plastic from the other to minimize damage to both plastics. That also means that sticking with recyclable petrochemical plastics, or PET plastics derived in whole or in part from plant-based resources (like Coke's PlantBottle program) results in less pollution and garbage.

There are exceptions – some deployments of bioplastics have focused on closed systems, like university or hospital campuses, where the company that provides the bioplastic packaging also controls the recycling stream. They can recover nearly 100 percent of the bioplastic products and compost or recycle them using the appropriate method for that type of plastic.

If the production chain is streamlined and progress can be made on the use of cellulosic plant material to produce bioplastics, then we could see a significant reduction in the environmental impact of plastic materials. The market for bioplastics is growing slowly but steadily [source: DeRosa], so there's a good chance we'll see serious improvements in the next decade.

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Sources

  • Coca-Cola. "PlantBottle Frequently Asked Questions." (April 5, 2012). http://www.thecoca-colacompany.com/citizenship/plantbottle_faq.html
  • Dell, Kristina. "The Promise and Pitfalls of Bioplastic." Time Magazine, May 3, 2010. (April 5, 2012). http://www.time.com/time/magazine/article/0,9171,1983894,00.html
  • DeRosa, Angie. "Bioplastics' growth slow, but prospects strong." Plastics News, July 18, 2011. (April 3, 2012) http://plasticsnews.com/headlines2.html?id=22604
  • Guzman, Doris. "Bioplastic stretches further." ICIS Chemical Business, Nov. 21, 2011. (April 3, 2012).
  • Marshall, Jessica. "Bioplastics Not So Green." Discovery News, Dec. 6, 2010. (April 5, 2012). http://news.discovery.com/earth/bioplastic-plant-plastic-environment.html
  • Packaging Recovery Organization Europe. "Fact sheet on bioplastics." March 2009. (April 5, 2012). http://www.pro-e.org/files/Factsheet_on_bioplastics_230309.pdf