|
|
 Fall
2003 |
||
 However, while composite lumber has potential as a use for recycled films, market forces have made it more efficient and cost-effective to use virgin rather than recycled polymers. Landscape architect Dan Stearns notes that composite lumber was developed not to recycle plastics, but to meet consumer demand for low-maintenance decks. “Virgin resins are still cheaper to work with,” Stearns says. “You can buy virgin at 10 cents a pound, in contrast with recycled at 20 cents by the time you shred the plastic, wash it with caustic solutions, rinse it with water and dry it.”
“We were going to use agricultural materials in composite decking, but it still has to be cleaned before you can use it, so you still have the expense. That’s why companies like using shopping bags and similar plastics—they’re cleaner than ag plastics.” Many experts think that soil residues and water in used ag plastics are an insurmountable problem—cleaning the plastic is too expensive to be economical. They see a future where agricultural plastic waste is not recycled, but is efficiently and cleanly converted into energy as Plastofuel. “At Penn State we’re developing a plastic fuel
nugget system that we hope will take care of plastic waste and at the
same time utilize its tremendous fuel value,” Lamont says. “I
really feel we’re on the cusp of answering this problem, not only
for Pennsylvania, but nationwide.”
The plastic fuel nugget system combines all types of thermoplastics—polyethylene, polystyrene, polypropylene, and others—into densified capsules to be burned as fuel. Instead of cleaning and sorting plastics for reuse, the process combusts plastics, dirt, and impurities together, using coal to boost burn temperatures to a safer level. Garthe says the goal is to develop a system to densify and burn enough plastic to heat some farm operation, such as a greenhouse or poultry house. “The higher the burning temperature, the fewer byproducts of incomplete combustion,” Garthe explains. “A burn barrel, for instance, typically operates at 400 to 700 degrees Fahrenheit, and that will give off the smoky, grimy stench that everyone complains about. I’ve seen sites where growers have tried to burn plastic in the fields, and all you get is a black, charred material, because it doesn’t burn completely. But when you burn the plastics with coal, the temperature reaches 1,800 to 2,200 degrees Fahrenheit. At that elevated temperature, a lot of the undesirable emissions are reduced.” What’s more, the plastics make a very good source of energy. “The heat value of the plastic is about 16,000 to 19,500 BTUs per pound,” Garthe says. “Fuel oil is about 20,000 BTUs per pound, while coal is about 12,000 to 14,000 BTUs per pound and wood is around 7,000 to 8,000 BTUs per pound.” Garthe and Lamont will continue their research into refining Plastofuel nuggets with Penn State’s Energy Institute, which can test various types of combustion, including stoker and fluidized-bed boilers in several different sizes. “The bottom line is that there’s a lot of energy laying around in the landscape that can be recaptured and utilized. That’s why it’s important to continue developing this process.” ____________________________________ Faculty and staff referenced in this article are James Garthe, instructor in agricultural engineering; William Lamont, Jr., professor of vegetable crops; Martin McGann, associate professor of landscape contracting; Michael Orzolek, professor of vegetable crops; and Dan Stearns, professor of landscape contracting.
|
||
|
Penn State | College of Agricultural Sciences | ICT Copyright - Alternative
Media - Affirmative
Action |
