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The recent introduction of white (pigmented) high-density polyethylene (HDPE) milk bottles has raised a number of technical and economic issues associated with the containers’ recyclability. This report presents the results of five studies conducted by the Department of Plastics Engineering at the University of Massachusetts Lowell, to help address questions concerning the recycling of this material. The majority of these studies focus on the physical characteristics of the recycled materials. There also are technical and economic issues associated with the recycling of the white HDPE bottle. This study does not attempt to address the economic issues associated with each option; however, a number of the technical issues associated with each of the three recycling options are discussed in this report.
This review concludes that recycled rubber derived from scrap tires is a safe recyclable material. This is consistent with years of usage of scrap tires in children's playgrounds and the use of the basic rubber material in chewing gums and pencil erasers. However, complete data for field tests of recycled scrap tires are currently not available. Although the studies of the environmental effects on the water layer below surface water and above groundwater table are relatively thorough, contradictions can be found in the existing data. Based on the evidence presented, the overwhelming conclusion is that it would be reasonable to recommend use of recycled scrap tires in civil engineering applications. However, it would be prudent to perform field studies on these areas over longer periods of time. It is important to recognize that the impact of scrap tires on the environment varies according to the local water and soil conditions, especially pH value. Thus, the field tests need to be systematically performed under Massachusetts’ conditions.
Low density polyethylene (LDPE) shrink-wrap film, discarded after over-winter use for protection of large boats, was demonstrated to be an appropriate and desirable feedstock for the molding of commercial products. Technical barriers to recycling were identified and circumvented, and a concept for portable equipment for in-situ conversion of discarded film to directly usable molding feedstock is presented. In addition to providing a commercially desirable source of feedstock, application of the results of this study should have a major positive environmental impact. An anticipated benefit is mitigation of a serious waste disposal problem experienced by hundreds of boatyards. Additional potential for creation of a new sub-industry to collect, preprocess and transport feedstock is identified.
This survey of ten Massachusetts paper mills assesses their ability and willingness to use increased amounts of recovered paper in their finished product. The data collected provides insight into the issues that effect a paper manufacturer’s decision to use recovered paper, including product quality, production costs, and waste generation. The survey advises that there is little incentive for the mills to dedicate the necessary resources to investigate the use of recovered paper; the technical and economic hurdles often are perceived to outweigh the potential benefits. The mills expressed a need for technical support to demonstrate the feasibility of using wastepaper, especially the lower grades such as residential mixed paper. UMass Amherst – Electronics Processing and Marketing Research Project In March of 1998, the Office of Waste Management (OWM) at the University of Massachusetts – Amherst proposed a short research project on the scope, functioning and potential of the electronics de-manufacturing and recycling industry in the Northeast region. The following three reports are the result of this effort.
The Massachusetts foundry industry currently recycles or reclaims only a small portion of the spent sand from their metal casting processes. Waste sand must be disposed of or may be used in other practices, and the reuse of waste products is regulated in Massachusetts by the Department of Environmental Protection (MA DEP) through Beneficial Use Determinations (BUDs). The long term sustainability and economics of the current disposal and reuse practices suggests that alternative use practices must be investigated. The purpose of this report was to investigate the barriers to reuse practices of spent foundry sand in Massachusetts.
A pilot scale trial to improve the overall efficiency of Erving Paper’s deinking system was performed at the Beloit Research & Development Center. The objective of this trial was to process Erving Paper’s specific furnish mix through a deinking system similar to their current system. The trial was designed to simulate the current mill operation and evaluate the benefits of adding kneading, sodium hypochlorite bleaching, post flotation, and post washing. This trial was successful in demonstrating that Erving’s furnish can be deinked using Beloit technology to give a quality final product.
The purpose of this study was to evaluate the mechanical performance of a recycled plastic material used for the production of injection molded landscape timbers. The extended service life for products used in outdoor applications, has raised concerns as to the effects of long term exposure to the weather. The formulation evaluated was based primarily on recycled high density polyethylene, and as such, will exhibit excellent resistance to moisture. However, the long term effect of sunlight exposure in the presence of oxygen is one of the primary causes of concern for plastic products slated for long term, outdoor applications. The mechanical performance of the landscape timber material formulation was evaluated as molded (for control purposes) and after approximately eight (8) years of simulated sunlight exposure in a carbon arc test apparatus. In addition, several other HDPE formulations (using the same base resin) were prepared in order to evaluate the effect of ultraviolet light stabilizing additives.
This report describes a research project carried out to investigate the feasibility of using recycled HDPE plastic timbers in the construction of typical landscape retaining walls. Two different options were examined for reinforcing/anchoring these walls: use of geosynthetics (geogrids and/or geotextiles), and use of the timbers themselves as reinforcing elements. The project scope included laboratory testing of the backfill soils, testing of several geosynthetic-timber facing connection designs, construction of two demonstration walls, and monitoring those walls for a period of about one year. The scope also included development of design and construction guidelines. (Also available are Appendix A, B, and E). Appendix C nor D are available in electronic format. For a hard copy please send your request to info@chelseacenter.org. Requests outside of Massachusetts, please send a check for $10 made payable to the University of Massachusetts to the address below.
Scrap tires pose a significant environmental and public health problem. A number of applications of this material have been attempted, but they cannot reuse the enormous amount of tires discarded every year, much less the stockpiles that exist from past disposal. The use of scrap tire chips in lieu of crushed stone aggregate in residential subsurface leaching field systems can potentially use large quantities of tire shreds. The Commonwealth of Massachusetts does not currently permit the use of scrap tire shreds in residential leaching field systems. Two primary concerns are the leaching of contaminants that may affect groundwater quality, and performance compared to a conventional leaching field system. This study presents the results of laboratory-scale experiments conducted to answer questions of leachate only. A field-scale study will answer the performance question and provide practical answers regarding the leachate.
RepTile™ is a resilient floor tile made from a blend of post-industrial, flexible PVC and post-consumer carpet waste. The RepTile is a 24" x 24" x 0.2" thick, interlocking floor tile that is ideal for use in high traffic and production areas that require durability and ease of maintenance. During early production and sale of this product, problems were discovered related to distortion of the tiles in the field. This project was designed to determine the cause of these problems and modify both the process and the material formulation to overcome the problems. It was discovered that high percentages of post-consumer carpet waste in the final product increased the severity and occurrence of tile distortion. The level of material mixing also affected the level of distortion and by increasing the level of blending, distortion could be eliminated even at higher carpet concentrations. (.pdf available soon)
With the constant development of new technology, the life span of most computers and electronics has shortened dramatically. This, in addition to waste bans translates into enormous projected volumes of computer and electronic scrap. As this scrap volume has increased, so has the number of associated plastic housings. Conigliaro Industries identified this huge volume of #3 - 7 plastics, and emphasized the concept of using the plastic regrind as an integral part of a new product. Cold Patch, an asphalt-like material used specifically to mend and/or patch large cracks and potholes in a paved area, was identified as a viable product to achieve this goal. With an American Plastics Council grant and a Recycling Industries Reimbursement Credit (RIRC) grant from the Department of Environmental Protection, Conigliaro purchased processing equipment and developed the cold patch mixing system. The Chelsea Center grant was used to develop a recipe for the cold patch. Several emulsion formulations were tried as well as various mixes of standard aggregates and plastic regrinds. (Appendix)
The presence of a wide variety of contaminants in recycled paper feedstock has proved to be an impediment to developing markets. This situation restricted Creative Paper’s ability to use a broad spectrum of recycled paper as raw materials in the production of corrugated medium and bottom liners. The goal of this project was to enhance the company’s capability to use a lower grade of recyclable mixed paperboard as a feedstock in its processes. The goal was achieved by: automating the present pulper reject dumping procedure, identifying and installing alternative equipment systems capable of filtering and screening out contaminants more efficiently, and installing a recirculation system with more efficient separation. These changes resulted in a more efficient and cost effective separation and pulping process which allowed the mill to increase its paper machine production by more than thirty tons per day. (.pdf available soon)
The purpose of this project was to develop a system that will efficiently and economically convert Ultra-High Molecular Weight Polyethylene (UHMWPE) waste into extruded sheet product. UHMWPE sheet is very versatile and enjoys the lion’s share of the total market for UHMWPE products. Hence, the largest potential for acceptance of UHMWPE sheet with a high waste content. A flat sheet with acceptable dimension tolerances and appearance was produced. However, testing showed the physicals to be satisfactory on the outer width dimensions but not in the middle portion of the sheet. Modifications to the fixture to correct the problem have been made and new samples will be made. Future work will be focused on perfecting the system so that it will produce a sheet with a high content of waste resin that has both acceptable appearance and acceptable, uniform physicals.
Cut and shredded textile waste containing spandex, cotton, and polyester was processed through a carding machine. Yarn and fabric were produced, but waste levels in the experimental manufacturing were high and output quality was poor. Experiments aimed to improve this performance by treating the material with solvents, to optimize the mechanical action in carding, and to reduce the amount of new carrier fiber added to the virgin/recycled blend. Possible flock applications for the fibers are also discussed, and recycled fibers were successfully converted into flock at a commercial manufacturing plant. Subsequently, the flock’s ability to absorb energy and its frictional properties were characterized. Nonwoven (needlepunched) fabrics were produced in the laboratory and waste from this process was evaluated for oleophilic and hygroscopic properties. Oil absorption testing of selected materials showed that the shredded fabric absorbs oil at a faster rate than typical fibers used for oil clean-up. It was concluded that these fibrous wastes, filled into knitted sock booms or pads, could be used where a high initial rate of cleanup of spilled oil is desirable.
Rubber production and use in the United States is rising, but methods to dispose of scrap rubber are limited. One potential opportunity is to reuse the scrap rubber by blending it with thermoplastics like polypropylene (PP). This study focused on making thermoplastic elastomers, which use large quantities of scrap rubber. Rubber particle size, the melt flow index (MFI) of the PP, the percentage of rubber by weight, and the type of thermoplastic were investigated for their effects on the physical properties of the rubber/plastic blends. Techniques to improve the quality and compatibility of the scrap rubber/plastic blends were developed. By proper selection of the components and compatibilization techniques, blends can be tailored for specific applications. The results of this work can guide manufacturers in the proper selection of materials and techniques to use recycled rubber in blends for a variety of product applications. Possible applications, including sports surfaces, were investigated. The physical properties and costs of some of the blends were compared to commercial products.
Estimates suggest current production of wood-thermoplastic composite products is about 300 million pounds per year, a three-fold increase over two years ago. Major markets are decking materials, pallets and automobile and window components. Fueled by the decreasing availability of solid wood relative to projected demands, both recovered wood and plastic materials are being investigated as substitutes. The objectives of this project were to identify wood and plastic recycling needs in Massachusetts and market opportunities for composite materials manufactured from these materials; and to develop a strategy for the manufacture of selected products. The investigation concentrated on products with high value-added capability, large potential markets, and a projected long-term life.
Electronics recycling is on the rise, which creates a growing waste stream of engineering thermoplastics (ETPs). As this waste stream increases, a parallel plastics recycling industry is needed. This project worked with the plastics supply chain to identify the capabilities of Massachusetts industry to process ETPs from used electronics; assessed the supply and identified markets for used electronic ETPs; demonstrated the performance of recycled ETPs derived from the electronics waste stream in injection molding applications; and initiated a series of Stakeholder Dialogues. These dialogues brought together the plastics supply chain to discuss barriers and opportunities in recycling and reuse of engineering thermoplastics. The Gordon Institute at Tufts University partnered with Nypro Inc., an international injection molder with headquarters in Massachusetts, to bring valuable industry know-how and manufacturing resources to the project. Recycled ETPs from used electronic equipment that were separated into single resin streams free of contaminants (such as metal and paper) performed well in a high performance injection molding application.
The Gordon Institute initiated a Stakeholder Dialogue process in the Spring of 1999 to bring together the plastics supply chain to discuss barriers and opportunities in the recycling and reuse of engineering thermoplastics (ETP) derived from used electronic equipment. The goal of the Dialogue is to stimulate cooperation within the supply chain to collect and process the growing volume of discarded plastics from electronics, and to utilize these recycled materials in new markets and applications. This report (to be viewed as a "work in progress") summarizes the outcome of the first two Stakeholder Dialogues, held on May 10 and June 22, 1999. The Stakeholder Dialogues are just beginning to unravel the complexity of the issues, develop recommendations, and work towards supply chain collaboration.
Recycline has manufactured the PreserveÆ toothbrush using recycled polypropylene since 1997, and currently markets it in three colors. Through ongoing market research, Recycline learned that many consumers list handle color as a primary consideration when purchasing a toothbrush. The company also learned that a large percentage of its clients would carry a children’s toothbrush from Recycline. To increase market share the company is planning to introduce three new colors, as well as the Children’s Preserve. With grants from the Chelsea Center, Recycline determined the optimal ratios of color to recycled material for its new Preserve colors, and that introducing color to the polypropylene feedstock during the molding step was most effective and cost-efficient. Working with consumers and two industrial design firms, Recycline developed two prototypes for the Children’s Preserve, which were presented at a retail industry trade show in October 1999.
Recycline is currently developing its first product designed for commercial users; a scuff board for tractor-trailers called the Ultra-Slide. With grants from the Chelsea Center, Recycline and its contract manufacturer, Arlin Manufacturing Co., explored ways to improve the manufacturing process for the Ultra-Slide, including the installation of new equipment. Recycline purchased 14,000 lbs. of post-consumer recycled high-density polypropylene (HDPE) and hired a company to compound 3,000 lbs. of the 14,000 lbs. with glass fibers. Arlin used this material to test improvements to its manufacturing process, including modifications to extruder dies and downstream cooling equipment. The compounded product and manufacturing changes produced a superior product.
The purpose of this project was to modify a formulation of recycled PVC and post-consumer carpet to produce a Class I fire-rated flooring product. Testing focused on varying the concentrations of PVC and post-consumer carpeting to assess their effect on fire resistance. In addition, a recovered, post-industrial vinyl roofing material, which already has flame retardant additives, was tested as an additive to determine if it could enhance the fire rating of the final product. Finally, flame retardant agents were added to the mixture to determine their ability to enhance the fire resistance of the final product. Testing showed that all the mixtures could be made into Class I rated flooring product and that changes in the concentration of post-consumer vinyl-backed tile had no real impact on the fire rating. Additions of flame retardant vinyl roofing membrane or even large amounts of flame-retardant agents did not significantly affect the final rating of the products.
From its client base of approximately 1,300 retailers and their customers, Recycline has learned that a variety of colors for the handle of the PreserveÆ toothbrush increases the attractiveness of the product, since color is a top buying criteria for consumers. The recycled polypropylene sourced for the PreserveÆ until this point had been uncolored, and color additives were used during compounding or production to achieve the Preserve’s color. With funding from the Chelsea Center, Recycline tested the use of pre-colored recycled polypropylene. Several suppliers of pre-colored recycled polypropylene were identified, and 5,400 lbs. of material were purchased. The Company then compounded and tested this material with New Frontier Plastic Company in Springfield, Massachusetts, and is now in the process of producing six separate colored handles from this material.
About 20,000 tons of manufactured waste asphalt shingles are being deposited in landfill every year in the state of Massachusetts, causing a shortage of precious landfill space, and a significant increase in deposit fee. The need to evaluate the use of these waste shingles in hot mix asphalt prompted a laboratory study by the Worcester Polytechnic Institute and UMass Dartmouth. The results show that the properties of hot mix asphalt with 3, 5 and 7 percent shingles are not significantly different from the properties of conventional hot mix asphalt used for surface courses. Hence, it seems that mixes with small amounts of shingles have the potential of savings as well as good performance. However, before any material can be used regularly, it must be evaluated under real-life production and construction conditions.
The Massachusetts Highway Department is making initiatives to increase their use of recycled-content products. One of the recycled products that MassHighway now allows for use via specifications is recycled plastic offset blocks, which serve as the attachment piece between guardrails and guardrail posts. Offset blocks represent a significant opportunity - over the past four years MassHighway construction contracts have required the use of approximately 37,000 offset blocks per year. Plastic offset blocks are becoming a commonly used product in place of wood and steel in other states, and a number of states have developed specifications that either allow or exclusively require use of these plastic blocks. The primary focus of this study is a cost comparison of offset blocks as it directly affects MassHighway. A secondary focus of this report is to understand the life cycle environmental impacts of blocks, which are not directly reflected in the cost.
This report evaluates ten distinct feedstock conversion opportunities against six criteria addressing the potential results, the likelihood of securing company commitments, the available supply of recycled feedstock, the production technology, the economics of making the conversion and the demand for recycled content products. Each feedstock conversion opportunity was assigned one of three levels of priority - high, medium or low. Nine feedstock conversion strategies represent the report's overall recommendations. They form a single, coherent approach that can be sustained over time, even as the Chelsea Center's priorities for targeted conversion projects change. Consistent with the priority rankings discussed above, it is recommended that the Center apply these strategies in the short-term to the two high priority feedstock conversion opportunities and, as resources allow, also to the four medium priority opportunities.
A research project was conducted to test the material properties of recycled plastic landscape timbers manufactured by SelecTech, Inc. of Taunton, MA for the purpose of evaluating the suitability of the timbers for retaining wall construction. Four-point flexural tests were used to evaluate the moment resistance characteristics of the timbers. The performance of the timbers was compared with theoretical performance of traditional wood timbers. As expected, the timbers were more flexible and had a lower moment resistance capacity, but the performance more than exceeded any expected loads when used in typical residential and commercial landscape retaining walls not exceeding eight feet in height.
This project involved investigating the feasibility of using recycled HDPE landscape timbers, in the construction of two retaining walls. One of the walls was constructed using engineered backfill and a full drainage system, the other using material stockpiled on site with no provisions for drainage. The scope of the project included determining the proper design for the retaining walls, construction of the walls, laboratory testing of the backfill material, and monitoring the walls for a period of ten months. Between June 25th and August 18th 1999, the two walls, using the landscape timbers and No. 4 reinforcing bar, were constructed at the University of Massachusetts at Amherst, Intermediate Processing Facility. The design used the passive resistance of the backfill on deadmen to provide the necessary resistance for the front face timbers. The wall construction went well, and the material was easy to work with. The performance of the wall has revealed some potential problems, but by slightly modifying the construction techniques and design, it is anticipated that these problems will be resolved.
Utilization of foundry waste products is subject to Beneficial Use Determinations by the MassDEP, with detailed characterization of the waste materials necessary in order to obtain permits. Quantities of twelve metals and regulated organic compounds extracted from foundry sand waste with the Toxicity Characteristic Leaching Procedure suggest that spent foundry sand can be beneficially used posing no or limited environmental or human health risk. Limited data suggests that spent sand be segregated from other, potentially hazardous waste streams, until detailed characterization can be performed. Mixed foundry wastes are essentially complex and must be evaluated independently. Non-ferrous foundries may produce spent sands with contaminants such as, lead, chromium, copper and zinc. The inherent variability of chemicals in wastes is not a cause for concern when their concentrations are significantly below the regulated standards. No direct correlation between leaching concentrations and bulk element content was generally found. The physical and chemical properties of foundry sands make them well suited for several reuse applications. Detailed information about leaching potential, methods for measuring risk, and waste management practices require further study. Additional work should include more detailed analysis of different waste streams and use of more appropriate analytical methods.
This field-scale study was conducted at the Massachusetts Alternative Septic System Test Center, at the Massachusetts Military Reservation Base in Falmouth. Three leaching field trenches were installed, one using conventional (gravel) fill, and the other two using tire shreds. The trenches all received influent from a septic tank effluent followed by a Distribution box. Wastewater quality was monitored for samples taken from the Distribution box and each of the three trenches for a seven-month period. The study concludes that tire shreds perform the same level of wastewater treatment as a conventional (gravel) system in terms of effluent water quality; do not leach any toxic metal, inorganic anion or metal of concern, except for manganese; do not leach any solids from their surface for the limited duration of this study; and should be compacted thoroughly before adding the top layer of sand above it.
This study, investigating the potential end uses of a polyester (PET) fiber waste, generated in the manufacture of PolartecÆ fleece fabrics, made by Malden Mills, of Lawrence, Massachusetts, was conducted in four phases: melt process feasibility, glass fiber and bottle scrap additives, fleece/polycarbonate blends, and solid stating. During the third phase of the project, with support from the Chelsea Center, Malden Mills hired an intern to look at the marketability of the pellets and molded samples made from the fiber waste. All of the formulations, including the control (unmodified) formulation molded well and appear to have “useful” properties. However, there are a number of issues that are important and will need specific attention. These issues include: residence time, drying, PET and injection molding, morphology, color, process line, contamination. The intern’s findings provides Malden Mills with two different opportunities: provide companies with the shear waste at no cost (savings due to avoided disposal costs), or invest in the equipment and training to pelletize the material, and find customers willing to pay a fair price.
Massachusetts manufacturers were invited to participate in a focus group in June 1999 to help identify barriers to post-consumer resin (PCR) use by the plastics industry, and to develop methods to overcome these barriers. While the focus group produced some valuable information, the Chelsea Center and the American Plastics Council felt that a broader survey of the industry was necessary to determine whether this information was representative of the industry. A mail survey helped to better identify both the barriers to PCR use and specific measures that might be taken to increase PCR use in the Commonwealth. A total of 18% of 246 targeted manufacturers completed the survey, and results were compiled in November 1999. The greatest barrier cited to the use of PCR was customer specifications for virgin resin and the most helpful method cited to increase its use was customer education.
Synthetic Lightweight Aggregate (SLA), produced by melt compounding high concentrations of coal fly ash into various thermoplastics, is being developed and evaluated for use in applications such as geotechnical lightweight fill, concrete masonry blocks, and lightweight concrete structures. The aggregates are manufactured through a thermal process using plastic to encapsulate and bind fly ash particles. A series of aggregate samples were produced using several different thermoplastics as binders at several fly ash to binder ratios. Results show that the SLA properties are influenced by both the fly ash concentration and the thermoplastic binder composition. However, as the fly ash concentration increases, the physical properties of the SLA become less dependent on the thermoplastic binder’s properties. At fly ash concentrations of 80%, the physical properties of the SLA are fairly insensitive to the composition of the thermoplastic binder. Samples of SLA were tested for their properties as a geotechnical aggregate and as a concrete aggregate. An expanded clay lightweight aggregate and a normal weight aggregate were used for comparison.
The majority of scrap tires are currently burned as tire derived fuel, despite potential environmental implications, while applications using whole tires and crumb rubber are still in their primitive stage. With the fast accumulation of scrap tires, it is clear that new markets and new technologies must be developed. The fact that rubber is a thermoset often leads to structural breakdown and material decomposition in attempts to recycle it like a thermoplastic. Incorporation of scrap rubber into thermoplastic elastomeric (TPE) materials is an appealing alternative to existing applications. TPEs incorporate the advantages of both thermoplastics and elastomers, and are readily recyclable in a manner similar to thermoplastics. Applications for TPEs are expanding, though the transformation of crosslinked rubber into a TPE remains a challenge. Studies of new TPEs from blends of ground scrap rubber with thermoplastics are presented in this report. Compatibilization techniques were employed to improve the mechanical properties of the resulting TPEs. The report is divided into four sections, which have been individually presented at national conferences. The first three sections deal with development of blends and compatibilization approaches. The last section is devoted to a scale-up study for processing the blends.
This report focuses on street sweepings and catch basin cleanings in the City of Worcester, Massachusetts. In order to reduce or eliminate the quantities of street sweepings and catch basin cleanings that would have to be transported for disposal outside the City in the near future, the City is considering reuse of these wastes. This report addresses regulations and policies; quantities, composition and characteristics; reuse options; treatment needs and methods; other communities’ approaches; and recommendations for implementation of a reuse program in Worcester.
This reports the results of an evaluation of the technical and economic feasibility of converting shear waste from a polyester fleece manufacturing facility into PET (polyethylene teraphthalate polyester) for sale and reuse in place of virgin PET. The shear waste is typically dark blue to black due to the many colors mixed together within the bales. The addition of a white pigment caused the color to change from a dark blue to a dark brown-purple color. Other color pigments had virtually no effect and it was concluded that only very dark color PET can be made from these shear wastes. The weight loss observed at typical processing temperatures could be due to loss of volatiles, moisture, additives, dyes, coatings, contamination, or PET decomposition products. During full-scale shear waste conversion, any volatiles of concern would be expected to be captured with conventional ventilation equipment used for plastics manufacturing. The results of physical testing of the PET material that was extruded and solidified was a brittle product that would likely be useable for only a limited number of applications as is.
A project was conducted to test the effect of adding an industrial mineral additive to mixed waste recycled glass during the fusing process of making glass units (glass pavers) for paving in place of bricks and concrete pavers. The additive seems to keep soda lime glass "glassy" rather than becoming hazy and dull in the kiln. The ultimate goal of the project was to make and test glass paving products made from mixed waste glass. In comparisons of flexure strength, it was found that a thirteen-pound per square foot (1” thick) glass paver was stronger in flexure than a seventeen-pound per square foot (15/8” thick) brick paver and twenty-four pound per square foot (21/3”) concrete paver. In addition, the test glass pavers were made with an energy input of 14,900 Btu per square foot, compared with published data of 20,100 for clay bricks and the equivalent of 26,750 Btu for the manufacture of concrete pavers. The theoretical energy needed to make the recycled glass pavers is actually only 6,600 Btu per square foot.
Chemically crosslinked rubber used in tires is one of the most difficult materials to recycle, as it will not dissolve, or melt and be reformed. Over a quarter billion tires are discarded annually in the US, with only around 60% of them being recycled or burned as fuel. A method that offers the greatest potential to fully recycle them, is to first grind them into a crumb/powder which sells for ~$0.04-$0.30 per pound (as the size decreases, the price increases), significantly less than the cost of all virgin rubbers ($1.00 or more per pound). However, the limitations of the material and current processing techniques permit only small amounts (~5% of all discarded tires) of reclaimed crumb/powder to be re-used as filler in asphalt, cements, and other materials and blended back into virgin rubber products. In the research reported here, a high-pressure high-temperature sintering technique to process recycled rubber powder into 100% recycled rubber products is described. The mechanical properties of the recycled rubber vary by rubber type and property but overall were shown to retain greater than 60% of the properties of the original rubber. There should be many rubber products that could be successfully made from scrap tires through this grinding and sintering process.
Approximately 11 million tons of waste asphalt roofing shingles are generated and disposed of in landfills in the US per year. The biggest issue raised as an impediment to the recycling of waste asphalt shingles from re-roofing project is concern over potential asbestos content. In the past asbestos was sometimes used in the manufacturing of asphalt shingles but the total asbestos content was always less than 1%. Asphalt Reclamation Industries (ARI) of Fitchburg, MA was permitted by the MA DEP to accept post-consumer asphalt shingle waste for processing for subsequent use in making asphalt pavement. The Chelsea Center for Recycling and Economic Development awarded ARI a Product Testing and Development grant to test for asbestos in 417 samples but also reviewed a total of 1,770 asbestos analysis reports from samples collected between March 2000 and September 2002. The results indicated that 0.3% of the samples analyzed tested positive for asbestos at greater than 1% and an additional 0.5% of the samples contained a trace amount (less than 1%) of asbestos. However, the actual frequency of finding asbestos in loads of shingles was probably less than this.
Studies have estimated up to 100,000 tons of mixed No. 3-7 plastic are generated annually in Massachusetts. Conigliaro Industries of Framingham, Massachusetts has addressed the need for beneficial use of this material by developing 'Plas-Crete': Portland cement concrete (PCC) containing mixed No. 3-7 waste plastic. GeoTesting Express' Materials Technology Center (GTX-MTC) was retained to better define the most appropriate mix parameters, to conduct third-party testing, evaluation, and related engineering services. Plas-Crete batches containing a range of sizes and types of mixed No. 3-7 waste plastic exhibited compressive strengths ranging from 300 to 1,700 psi. These values indicate Plas-Crete can be used for "low-density" (i.e., insulating) and "moderate-strength" lightweight concrete. GeoTesting Express is confident that with alteration of mix ratios and use of specific plastic sizes and particle shapes, higher compressive strengths (e.g., >2,500 psi) may be obtained allowing use of Plas-Crete as "structural" lightweight concrete. Plas-Crete has been an immediate success in the marketplace through use in manufacturing large (2’x 2’x 4’) lightweight concrete wall blocks for temporary and easily constructed retaining walls. These are currently being sold at a rate of 250 per week consuming about 31 tons per week of plastic that would otherwise go to a landfill.
The use of elemental lead (Pb) in fishing sinkers and jig head lures has raised environmental concerns. This project investigated the potential to manufacture a cost-effective alternative to lead-based sinkers and jig heads by developing a moldable, recycled plastic compound with a filler having a final product density similar to lead. The test used a commercial grade of 50/50 (by weight) talc-filled polypropylene. The product density was only 1.83 g/ml. Because the density of this talc-filled plastic was not as great as lead, the sample product did not match conventional lead-containing products. Therefore, a denser plastic compound must be found. Fillers to be further investigated include common and commercial grades of barium sulfate, hematite, and perhaps titanium. Assuming that a denser compound could be found or developed, the manufacturing process used was evaluated to determine the approximate cost of a lead-free alternative and a unit cost of about $0.30 was estimated. This cost is much higher than a simple lead-containing sinker. Therefore, unless legislation is passed requiring the use of lead-free sinkers (as is occurring with shot from shot gun shells near watersheds), there does not appear to be an economic opportunity for plastic sinkers to compete with lead sinkers. However, due to the higher costs and profit margins for jig heads, there may be an opportunity to market lead-free plastic replacements for value-added sinking fishing lures and jig heads.
This market research report focuses on the potential for manufacturers of nonwoven fabric and other textile products in and near Massachusetts to use shoddy or other scrap textile products as raw material instead of virgin cloth or synthetic fibers. Feedstock conversion based on scrap textiles is extremely challenging because of fundamental technical and other barriers affecting each stage of the value chain. The used textiles in greatest supply are used clothing which is often too varying and inconsistent in fiber type or too “contaminated” to be recycled into new textile. On the other hand, scrap textile that could most easily be recycled is manufacturing scrap that is in short supply as textile mills continue to move south and overseas. Other important barriers include the difficulties of increasing supplies (related to international trade concerns and a drop in prices for used clothing and other scrap textiles), lack of proven technologies, cynicism among manufacturing managers and a general lack of statistics and information on scrap supplies and markets. And yet, there is interest within certain companies in identifying new recycled content product niches and enthusiasm for research directed towards that end.
Synthetic Lightweight Aggregate (SLA) was developed, produced and evaluated for use in construction applications such as concrete masonry units (CMU), lightweight concrete, and asphalt pavement. The SLA is produced by melt compounding commingled waste plastics and high amounts of coal fly ash. Waste plastics from other sources than municipal solid waste (i.e., computer housings) can also be used to produce SLA. The presence of ammonia in fly ash has no impact on the production process of SLA and no ammonia was released during the melt compounding of ammoniated fly ash and commingled waste plastics at the ratio of 80:20 fly ash to waste plastics. The effect of PVC (polyvinyl chloride plastics) in the waste plastic stream was also tested. The results indicated that, with more than 4% PVC, the PVC degrades at the high temperature required for producing SLA and therefore the HCl gas that is emitted may be corrosive to the production equipment and may be harmful to workers without controls. The SLA samples were also tested for Los Angeles Abrasion and outperformed every other aggregate tested in this study for comparison. This test is very crucial test for use of aggregate in asphalt pavement and results show high potential for use of SLA in asphalt pavements. |
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