Bio-based chemicals: When green is toxic

Compostable cups. The PlantBottle. Polyethylene plastic from sugar cane. Bioplastics and other biobased chemicals – made from plants rather than petroleum – can slash a product’s carbon footprint.

Brand owners are driving demand for bioproducts to help meet corporate sustainability goals. And biobased makes economic sense as a hedge against the high price of crude and volatile fossil fuel markets.

But is bio-based enough? Consumers want safer products too. Simply replacing the carbon from oil with carbon from plants won't necessarily make a product safer, if the chemical in question is hazardous to health. If toxic petrochemicals are made with renewable biomass, will customers revolt? Let’s explore the challenge.

Ten years ago, Cargill launched NatureWorks to convert cornstarch to polylactic acid (PLA), the first biopolymer to compete head-on with petrochemical plastics and fibers. PLA scored so well against all 12 principles of green chemistry that the U.S. Environmental Protection Agency gave the company a prestigious national award for environmental safety.

Since then, biobased demand has exploded. Although just a few percent of all plastics are biobased today, analysts predict rapid annual growth will claim 20 percent market share within a decade. Getting to 90 percent is already technically feasible.

Major Benefits to Climate

Turning plants into products can reduce our dependence on fossil fuels in two ways. Manufacturing PLA produces 60 percent less greenhouse gases than the petrochemical plastics such as PET and polystyrene. Life cycle assessments show similar reductions for other biobased chemicals.

But bioproducts reap even greater climate benefits upstream of the production process. Biomass has a material carbon footprint of zero. That’s because plants fix carbon dioxide from the atmosphere in roughly the same timeframe (years) that greenhouse gases are released at the end of the useful life of bioproducts. But petrochemical products are made from fossil feedstocks formed millions of years ago. The eventual disposal of petro-products adds to man-made climate change.

Consider the material carbon advantage. Every hundred pounds of biopolymer that replaces fossil-based polyethylene avoids 314 pounds of carbon dioxide emissions over the life of the product. Substituting for petrochemical PET reduces greenhouse gas emissions by about 230 pounds.

Although the climate gains are real, the market rush to bioproducts has raised some old questions and a new concern.

Next page: Out with the Old Questions …