USA – Penn State researchers receive grant for turning waste plastics into fuel

University Park, Pennsylvania. — After a decade of experimentation into creating fuel nuggets out of unrecycled waste plastics and burning them without creating toxic emissions, a team of researchers in Penn State‘‘s College of Agricultural Sciences recently received an $87,395 grant from the state Department of Agriculture to ramp-up their research.



“Our mission is to alleviate the burgeoning problem of waste plastics in our environment, especially on the farm,” said James Garthe, instructor in agricultural engineering, cooperative extension specialist and spokesman for the team. “We want to get energy from waste products, and plastics have energy we can recover. Properly done, plastic can supplement coal in coal-fired boilers. Why should we continue to throw energy into landfills?”



What makes this team‘‘s approach to making nuggets from waste plastic novel is the low-energy process they have developed that results in what Garthe has dubbed “Plastofuel” — a sort of rigid, waste plastic “sausage” about an inch-and-a-half in diameter. Only the outside skin is melted and fused to hold the unmelted, tightly compressed, sometimes dirty waste plastics inside.



The “sausage” is then cut into 1- to 2-inch-long nuggets. “Because the plastic is not completely melted, calculations show that only about one 85th of the energy released when the plastic nuggets burn is used to create the nugget,” he said. “With the energy required to preprocess the plastic and to cut the pieces included in the calculations, the nuggets still supply 20 times the energy used to make them.”



Although the researchers have concentrated much of their work on collecting, “nuggetizing” and burning agricultural waste products such as silage wrap, mulch film, landscape pots and flats, and pesticide and fertilizer containers, they have included household and business waste plastics in their research. “Most people think that when they place their recycling bins at the curb, all of their waste plastics are being recycled, but that‘‘s not true,” Garthe explained. “Our society does a pretty good job recycling plastic numbers 1 and 2, but that‘‘s all.”



Plastic categories 4 through 7 — such as lids, sheets of plastic and wrappers — traditionally are discarded at recycling centers. “Those plastics generally are baled and sent to a landfill. But they are of value for Plastofuel because they generate heat when burned,” said Garthe. “We will stay away from burning number 3s — vinyl, such as PVC pipe, siding and some irrigation tubing — because of the chlorinated compounds they contain. During combustion, they can become precursors to the emission of dioxin, a highly regulated substance.”



The state grant is for 18 months, and the full grant amount is not guaranteed until the state‘‘s 2005-2006 budget is approved. The funding is intended to allow Garthe and his associates to ratchet up their existing small-scale nugget-making process to 500 pounds per hour. One of the first hurdles they must clear is to develop a machine to reduce the size of larger plastic waste by grinding, chopping or shredding — not a simple task, Garthe pointed out, when one considers that the blades will encounter mud, sand, pebbles and other debris stuck to waste plastics.



“We‘‘ll just have to factor that into the design,” Garthe said. “We envision fitting the size-reducing and nugget-making equipment onto a trailer that we can haul to an interested business or farm, where we can show owners and employees how it can be done.”



Garthe‘‘s approach to using waste plastics is revolutionary because it is so forgiving. “In plastics recycling there are two unbreakable rules,” he said. “You cannot mix typ