As more than 3 billion quart-size, high-density polyethylene motor-oil containers head for U.S. landfills each year, LSU AgCenter researchers are looking for ways to keep them out.
Each year, U.S. motorists use about 150,000 tons of HDPE containers, leaving the insides coated with residual motor oil, said Qinglin Wu, a researcher in the Louisiana Forest Products Development Center in the LSU AgCenter.
Wu has been working for years to develop methods for using recycled plastics with wood and other fibers to create new products.
Wu and his research team have been combining recycled plastics with such fibers as rice straw, wood and bagasse — the fibers remaining after the juice is squeezed out of sugarcane — to create engineered products that can be used in a variety of construction projects.
While many used plastic containers can be recycled, containers contaminated with motor oil pose special problems, Wu said. Most recycling programs cannot accept emptied motor oil bottles.
“Currently, in order to recycle used plastic containers with residual petroleum products, the containers usually must be cleaned first to remove the petroleum residue,” Wu said.
While developers have created techniques to separate plastic and oil, these methods are often too expensive and/or too energy intensive to implement on a production scale, he added
Using solvents to wash away the oil creates different waste products that are difficult to dispose of, Wu said.
Recycling partially cleaned oil containers for new oil bottle manufacturing has been one of the primary targets for the recovered HDPE plastic, the researcher said. However, the blow molding process used for manufacturing the bottles requires temperatures high enough to cause significant thermal degradation of the residual oil. And the bottles end up having a strong oily odor, which severely limits their marketability.
Wu’s process combines the recycled, oil-contaminated plastics with natural fibers that absorb the oil and a “coupling agent” to bond the fibers into the plastic.
The result is an engineered product that can be used in place of wood in many applications, Wu said. He cautioned, however, that the new product has to be used outdoors because residual oil still represents 5 to 6 percent of the plastic component.
Because it doesn’t require any extreme measures to clean the plastic, the process produces little waste, Wu said.
“This process provides a way to deal with recycled plastics,” Wu said. “And the oil bonded into the product won’t escape.
“Louisiana produces many natural fiber products and has a lot of polymers from chemical processing plants,” he added. “This product will bring these two industries together.”
Wu said the process has drawn interest from oil producers, including BP, which has provided funds to perfect the process.
“By properly recycling, we can show issues like this can be dealt with,” Wu said.