Other Awards and Honors
1996 Discover Magazine Awards
Finalist - Environmental Category - RubberCycle: Tire-Recycling Microbes-Robert Romine
Discover Magazine Awards for Technological Innovation were presented by the Christopher Columbus Foundation "to recognize the all-too-often neglected men and women behind the technologies that impact our lives."
PNNL chemist Bob Romine was working on a way of using recycled tire rubber in asphalt pavement when his wife, Margaret, a PNNL microbiologist, introduced him to Sulfolobus acidocaldarius. As the name implies, the bug likes to dine on sulfur found among the minerals in the hot springs. When added to a vat of powdered tire rubber, the microbe attacks the sulfur in the rubber. That turns out to be the best way of decomposing this chemically tough material that is hard to recycle. Although virgin rubber is like "a plate of wet noodles," as Romine says, when heated the sulfur atoms combine with carbon to form a stiff lattice. Sulfolobus breaks the lattice down. Automobile tires generally cannot contain any more than 3 percent of recycled rubber because of high performance requirements: inert impurities would cause too much heat to build up when the rubber meets the road, making the tires wear out quickly. For this reason, Romine makes sure to curb his bacteria, either by lowering the temperature or raising the pH, before they break down all the sulfur-carbon bonds. That way the rubber can be made to bond more thoroughly with virgin rubber during recycling. Because these bonds dissipate heat, tires can contain up to 15 percent of the recycled rubber without sacrificing quality.
RubberCycle also won and R&D award in 1997.