Vol. 6, No. 4- April 2002
Horticulture Department
The Pennsylvania State University
`
Managing Used Agricultural
Plastics
James W. Garthe, PE, Dept of Agricultural and Biological Engineering
Your Options Today...
Option 1. Open Burn
On-site
This option is unacceptable. However, state law does allow farmers to burn waste products from the production of agricultural commodities, which includes used plastics. Municipalities are adopting open burning ordinances that override state laws and prohibit burning of plastics by farmers. Burning plastics results in high concentrations of various air pollutants, especially when allowed to smolder. If you feel you must burn, at least ensure that your fire is as clean as possible by following these guidelines:
* Remove ash from previous burn. Wet ashes and plugged air inlets create poor conditions for complete combustion to occur.
* Burn it as hot as you can. Add sticks or scrap lumber to promote combustion. Smoldering fires have flame temperatures that are 400-600 °F or less, releasing many products of incomplete combustion.
* Give it plenty of air. If you're using a barrel, make sure there are plenty of air holes. Better than a barrel, use a burner with a grate for good aeration.
* Do not let it smolder. Pollution increases when a fire smolders.
Option 2. Bury or Dump
On-site
This option is unacceptable. Farm dumps are becoming liabilities, especially when transferring title to the farm. Banks, realties, and various lending agencies are looking critically at the farm dump as an environmental concern. Environmental professionals conducting environmental site assessments (ESA's) on farmland during title transfers may uncover more liability than the seller can afford. Costs can exceed $10,000 for laboratory tests alone.
Option 3. Haul to
Recycling Facility
Recyclers or reprocessors have certain requirements before accepting your plastics:
1. Keep plastic types separate. Most plastics don't mix when they're melted during recycling. If you don't know the type plastic you're working with, ask your supplier.
2. Ship large quantities. Reprocessing centers only accept truckload quantities of 30,000 - 40,000 pounds.
3. Must be baled or palleted. Plastic should be baled or pallet-wrapped to fill a semi-trailer for shipment. Bale sizes vary, but are typically 800-1200 pounds.
4. Keep items clean and dry. Reprocessors typically allow 1-4 percent contamination by weight. Loads are often rejected if they're dirty. Suggestions are to:
* store bales indoors off the floor
* remove debris from inside bales, such as crop material, rags, tape, moisture, mud / soil, paper, cardboard, or paperboard
* discard other plastics like polystyrene (Styrofoam) or polyurethane (foam rubber)
* wipe off any oil or grease
* band with plastic strapping, not steel banding, twine or rope
Currently, polystyrene trays and flats are being accepted from Pennsylvania for recycling in Canada. Truckload quantities (about 26 pallets, shrink-wrapped) will be picked up free of charge and you will receive $80 per ton of resin recycled. Contact:
Canadian Polystyrene Recycling Association, 7595 Tranmere Drive, Mississauga, Ontario L5S 1L4 Ph: 905.612.8290 Fax: 905.612.8024
Option 4. Haul to
Waste-to-Energy Facility
This is a great way to manage plastic wastes. Waste-to-energy (WTE) facilities convert the high heat energy of plastics to steam, which in turn generates electricity. This is a great way to gain a second life from your wastes. The high burn temperatures in these facilities achieve over 99.9 percent complete combustion. Their popularity has been hampered by negative public perceptions associated with stinky smokestacks from old, obsolete incinerators. Today, emissions have been regulated to the point that they are hardly perceptible, and certainly not in concentrations that are toxic downwind from the facility. WTE's are safe.
This table compares the energy value of different materials when burned. Btu is British Thermal Units.
(By comparison, one paper match gives off about 1 Btu.)
Waste Material Btu/lb
Fuel Oil 20,900
Polyethylene plastic 19,900
Polypropylene plastic 19,850
Polystyrene plastic 17,800
Wyoming coal 9,600
Newspaper 8,000
Textiles 6,900
Wood 6,700
Yard wastes 3,000
Food waste 2,600
Average for Municipal
Solid Waste 4,500
Option 5. Hire Waste
Hauler
Farmers are hesitant to pay a private waste hauler to remove trash. However, this is often the option that might best suit your situation. Most of this material is landfilled. To minimize pollution, all landfills today are sealed top and bottom, and many have leachate and gas collection systems. Landfill gas is used to supply energy needs in the area.
Your Options
Tomorrow...
Option 1. Produce Fuel
Nuggets
Penn State has developed a process to densify dirty plastics into fuel nuggets. The nuggets are designed to be co-fired with coal in existing boilers. The end-use can be for agricultural boilers or for small community boilers designed to burn coal. The nuggets can be made either on the farm or in small industrial settings, thus consuming the energy close to the plastic supply. The benefit of the system is that it converts an annoying waste into a valuable fuel, with a minimum of energy expended in the process.
Option 2. Haul to
Waste-to-Energy Facility
As mentioned earlier, these facilities are very efficient at converting wastes to energy. As coal and petroleum reserves dwindle, these facilities will inevitably become more commonplace.
Questions may be directed to: Mr. James W. Garthe, PE, Dept. of Agricultural and Biological Engineering Penn State University, 246 Agricultural Engineering Building, University Park, PA 16802 Ph: (814) 865-7154 Fax: (814) 863-1031 Em: jwg10@psu.edu