Greener Plastics

There can be little doubt that plastic materials have dramatically improved everything from clothing to travel to communications to building. Some of the damage they have caused, however, is equally dramatic.

The most well-documented concerns about traditional plastics relate to their persistence in the environment. Plastic bags and water bottles fill up landfills, and plastic fragments gather in high concentrations in a large area of ocean known as the Great Pacific Garbage Patch. Less well known is that for every bit of solid waste floating in the ocean, as much as an equal amount of soluble plastic has dissolved in the water, where it can harm marine life.

Avoiding these problems doesn’t mean we must do without plastics. It is possible to create plastics that end their lives without polluting or poisoning (see “Plastic from Grass”).

Plastics created using the principles of “green chemistry” are designed to reduce or eliminate the use and generation of hazardous substances throughout their life cycle. This means nontoxic, renewable feedstocks, a manufacturing process that yields little or no waste, and a final plastic that, when discarded, degrades into harmless products on a human rather than a geologic time scale.

Green plastics can be made synthetically, but most are made from biomass feedstock. In recent years, the large-scale manufacturing of polylactic acid (PLA, made from starches) and polyhydroxyalkanoates (PHA, fermented from sugars or fat) has show that there may be significant market niches for green bioplastics.

PLA has been used in applications ranging from food packaging to automotive components to clothing. While its current market share is small, there are significant reasons to be optimistic that it will take on a bigger role and that green plastics in general will become more competitive.

Growth in the use of biofuels, though modest, increases the incentive to develop applications for nonfuel materials produced in biorefineries. Progress is being made toward addressing the performance limitations of bioplastics like PLA using nontoxic additives, much as plasticizers can be used to soften brittle PVC and turn it into a rubber duck toy.

Most important, research is showing that formerly recalcitrant feedstocks such as grasses, agricultural wastes, and wood are promising bases for new materials. These plastics may have not only an environmentally friendly life cycle but enhanced performance, functions, and capabilities.