Bioplastics FAQ

Below I take a crack at answering some questions I’ve been getting from design engineers about plastics made from plants, such as corn. These are strictly my opinions. I welcome clarification and amplification from suppliers or design engineers who have done some testing and analysis on these products.

What are they made from?

Early production facilities in the United States use corn as the primary feedstock. Future development focuses on use of waste biomass such as switchgrass. The focus shifted in the past 18 months because of concerns that ethanol (and to a much lesser extent bioplastics) would divert crops from human food supplies. Bioplastics (nylon 11) made from castor oil date back to the 1940s and have been widely used for fuel-line components. Plastics made from plant cellulose (such as Tenite) are also strongly established. Soybean oil is also being used by Ford to make seat cushions.

How strong is their environmental argument?

It runs the gamut. The biodegradability argument has always been weak because landfills are anaerobic and are designed to stop degradation. The carbon footprint argument has merit, but there are few high-quality cradle-to-grave lifecycle analyses that clearly make the case. The use of corn in the United States as a hydrocarbon replacement has been fueled more by politics than by environmental issues. Some bioplastics can also foul existing plastic recycling streams. For that reason, Telles is not proposing use of its bioplastic in bottles as a replacement for polyester.

How suitable are they for durable goods?

Again, this is changing. The original application targets were biodegradable packaging. The newer, stronger, argument focuses on reduced carbon footprint compared to hydrocarbon-based plastics. As a result, some of the biomaterials, such as DuPont’s Sorona, is blended with high-performing, traditional engineering plastics. Toyota is taking the tack of blending bioplastics, such as polylactic acid (PLA), with stronger plastics. Because of the newness of the bioplastics, significant prototype testing of parts made from the new bioplastics would be in order.

How do the economics stack up?

Right now, it costs significantly more to make bioplastics than plastics based on petroleum. With scale, most bioplastics probably will remain more expensive. The wild card, of course, is the future price of hydrocarbons. DuPont seems to be taking one of the smarter marketing strategies by creating plastics blends with demonstrably better properties than their alternatives. They are also more expensive ($2 to $3 per pound). Another strong player is Mirel polyhydroxoxyalkanoate (PHA), which will be priced around $2.50 a pound. It has properties comparable to ABS, which sells at slightly less than $1 per pound.

Is anyone actually using this stuff?

Most of the actual use is in Japan where there are government mandates to reduce the carbon footprint. As mentioned, historical bioplastics such as nylon 11 and cellulosics fit niches based on their properties and economics. There is tremendous capacity coming on line to produce the newer bioplastics. The expectation is that most of it will go into packaging. Big box retail companies with advanced green programs and smart buyers will make or break bioplastic packaging.  Is the environmental case strong enough? Is it worth slightly higher prices? Will consumers buy into it? To be determined. So far the green story is taking some interesting turns. For example, reusable cloth bags are looking like a future winner in the paper-versus-plastic battles in grocery stores. How is a biodegradable plastic bag a better story? They aren’t recycled and they don’t degrade in landfills. Engineering applications in the United States to date for bioplastics are very limited. People like you will decide. Is it worth a higher cost to design a component that reduces the carbon footprint? Will the government set mandates, as it has in Japan?  If the government becomes involved, is there a better way to skin the carbon cat?

Cosmetic container shown below is made of Cereplast compostable resin