3 results
Distributed Recycling of Post-Consumer Plastic Waste in Rural Areas
- M. Kreiger, G. C. Anzalone, M. L. Mulder, A. Glover, J. M Pearce
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1492 / 2013
- Published online by Cambridge University Press:
- 27 February 2013, pp. 91-96
- Print publication:
- 2013
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Although the environmental benefits of recycling plastics are well established and most geographic locations within the U.S. offer some plastic recycling, recycling rates are often low. Low recycling rates are often observed in conventional centralized recycling plants due to the challenge of collection and transportation for high-volume low-weight polymers. The recycling rates decline further when low population density, rural and relatively isolated communities are investigated because of the distance to recycling centers makes recycling difficult and both economically and energetically inefficient. The recent development of a class of open source hardware tools (e.g. RecycleBots) able to convert post-consumer plastic waste to polymer filament for 3-D printing offer a means to increase recycling rates by enabling distributed recycling. In addition, to reducing the amount of plastic disposed of in landfills, distributed recycling may also provide low-income families a means to supplement their income with domestic production of small plastic goods. This study investigates the environmental impacts of polymer recycling. A life-cycle analysis (LCA) for centralized plastic recycling is compared to the implementation of distributed recycling in rural areas. Environmental impact of both recycling scenarios is quantified in terms of energy use per unit mass of recycled plastic. A sensitivity analysis is used to determine the environmental impacts of both systems as a function of distance to recycling centers. The results of this LCA study indicate that distributed recycling of HDPE for rural regions is energetically favorable to either using virgin resin or conventional recycling processes. This study indicates that the technical progress in solar photovoltaic devices, open-source 3-D printing and polymer filament extrusion have made distributed polymer recycling and upcycling technically viable.
Environmental Impacts of Distributed Manufacturing from 3-D Printing of Polymer Components and Products
- Megan Kreiger, Joshua M. Pearce
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1492 / 2013
- Published online by Cambridge University Press:
- 08 March 2013, pp. 85-90
- Print publication:
- 2013
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Although additive layer manufacturing is well established for rapid prototyping the low throughput and historic costs have prevented mass-scale adoption. The recent development of the RepRap, an open source self-replicating rapid prototyper, has made low-cost 3-D printers readily available to the public at reasonable prices (<$1,000). The RepRap (Prusa Mendell variant) currently prints 3-D objects in a 200x200x140 square millimeters build envelope from acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). ABS and PLA are both thermoplastics that can be injection-molded, each with their own benefits, as ABS is rigid and durable, while PLA is plant-based and can be recycled and composted. The melting temperature of ABS and PLA enable use in low-cost 3-D printers, as these temperature are low enough to use in melt extrusion in the home, while high enough for prints to retain their shape at average use temperatures. Using 3-D printers to manufacture provides the ability to both change the fill composition by printing voids and fabricate shapes that are impossible to make using tradition methods like injection molding. This allows more complicated shapes to be created while using less material, which could reduce environmental impact.
As the open source 3-D printers continue to evolve and improve in both cost and performance, the potential for economically-viable distributed manufacturing of products increases. Thus, products and components could be customized and printed on-site by individual consumers as needed, reversing the historical trend towards centrally mass-manufactured and shipped products. Distributed manufacturing reduces embodied transportation energy from the distribution of conventional centralized manufacturing, but questions remain concerning the potential for increases in the overall embodied energy of the manufacturing due to reduction in scale. In order to quantify the environmental impact of distributed manufacturing using 3-D printers, a life cycle analysis was performed on a plastic juicer. The energy consumed and emissions produced from conventional large-scale production overseas are compared to experimental measurements on a RepRap producing identical products with ABS and PLA. The results of this LCA are discussed in relation to the environmental impact of distributed manufacturing with 3-D printers and polymer selection for 3-D printing to reduce this impact. The results of this study show that distributed manufacturing uses less energy than conventional manufacturing due to the RepRap's unique ability to reduce fill composition. Distributed manufacturing also has less emissions than conventional manufacturing when using PLA and when using ABS with solar photovoltaic power. The results of this study indicate that open-source additive layer distributed manufacturing is both technically viable and beneficial from an ecological perspective.
Effects of periparturient systemic treatment with penethamate hydriodide on udder health and milk yield of dairy heifers
- Martina Kreiger, Gabriele M Friton, Johannes Hofer, Klemens Fuchs, Petra Winter
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- Journal:
- Journal of Dairy Research / Volume 74 / Issue 4 / November 2007
- Published online by Cambridge University Press:
- 26 July 2007, pp. 392-398
- Print publication:
- November 2007
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Sixty dairy heifers from seven Austrian herds, with high prevalence of Staphylococcus aureus mastitis, were used in this pilot study. Heifers were randomly allocated to two groups. The treatment group received at parturition intramuscularly 10 million i.u. of penethamate hydriodide and then 24 h later, 5 million i.u.; the control group received no treatment. Bacteriological examination was conducted on 7, 14, 21, 35 and 49 d post partum (pp) and milk yield data, fat and protein contents and SCC data were collected every 5th week for the first 200 d of lactation. Occurrence of retained placenta and endometritis were recorded, and the days open of both groups were compared. No effect was observed on the postparturient genital tract health and reproduction indicators. On day 7 pp, four intramammary infections (IMI; two severe clinical; one mild clinical; and one subclinical mastitis) were detected in the untreated control group, whereas there were no IMI in the antibiotic-treated group. At subsequent samplings, there were fewer IMI in the antibiotic-treated group, which were later in lactation, less severe and less persistent. Although SCC was numerically lower in the treatment group, significant differences in SCC between groups could not be detected. Antibiotic-treated heifers produced significantly more milk during the first 15 weeks of lactation than untreated heifers. Over the whole observation period (200 d), peripartum antibiotic-treated heifers produced 323 kg more milk than heifers in the untreated control. Periparturient antibiotic treatment of heifers with penethamate hydriodide prevented IMI during the first week after parturition and achieved a significant increase in milk yield, which was found to be economically beneficial.