Environmental Research & Technology Division
Technology Development & Applications Group
Use of Recycled Polymers to Encapsulate
Radioactive, Hazardous, and Mixed Wastes
Background
Approximately 16 million metric tons of plastic are generated in the U.S. each year. These non- biodegradable plastics comprise a significant fraction (20 % by volume) of the total municipal solid waste currently filling up municipal landfills. In addition, plastic waste generated at DOE and commercial facilities that is contaminated with low-level radioactive, hazardous, or mixed- waste is currently either compacted for land disposal or incinerated. Both of these treatment options are considered controversial from an environmental and public policy standpoint.
Objectives
The objective of this project, sponsored by the New York State Office of Recycling Market Development, is to investigate the use of recycled plastics in place of virgin materials for use in the
polyethylene micro and
macroencapsulation process to provide a valuable new market for non- biodegradable plastics that are currently filling up municipal landfills. Additional benefits include reduction in the use of valuable petroleum resources used in the production of virgin resins and lowering the cost of waste disposal. Further, the use of mixed waste-contaminated plastics for treatment of other DOE and commercial mixed wastes will reduce the volume of waste requiring treatment and disposal, providing additional economic and environmental incentives. This approach would reduce the quantities of contaminated plastics (e.g., bottles, test tubes, gloves) generated and would enable the use of these materials for treatment of other wastes.
Task Summary
Blends of waste plastics will be optimized to maintain high quality final waste form performance while maximizing the use of co-mingled recycled streams. This project will investigate the feasibility of using recycled polyethylene in place of virgin materials for waste encapsulation in three phases. The initial phase will concentrate on the use of clean, homogenous, well- characterized recycled low-density polyethylene feedstocks. Impact of recycled plastics on process parameters will be examined including output rates, melt temperature and pressure, maximum screw speed, and current draw. Changes in overall product quality including homogeneous mixing, density, strength, durability and leachability will also be investigated. Several surrogate waste types will be examined including radioactive, hazardous, and mixed wastes. These data will enable evaluation of the potential for using recycled feedstocks in place of virgin LDPE for waste encapsulation. If successful results are obtained, the second phase will expand the approach to incorporate heterogeneous plastics streams (i.e., co-mingled thermoplastics including polyethylene teraphthalate (PET), high-density polyethylene (HDPE), and polypropylene (PP)) and "contaminated" streams (i.e., containing small quantities of non-plastic materials such as wood, metal, paper, dirt). In addition, potential waste stream applicability will be expanded in Phase II to include municipal solid waste (MSW) ash. The final phase of this effort will investigate use of actual waste plastics generated within DOE and the commercial sector that may themselves be contaminated with mixed wastes and thus require treatment prior to disposal.
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Last Modified: November 12, 2009
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