Life Cycle Studies Shed Light On Environmental Performance of Everyday Plastics
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The larger study, “Final Report – Cradle-to-gate Life Cycle Inventory of Nine Plastics Resins and Four Polyurethane Precursors (2010),” updates a previous study completed in 2007 that looked at nine resins and two polyurethane precursors, and adds two new polyurethanes precursors – methylene diphenylene diisocyanate (MDI), and toluene diisocyanate (TDI).
The second study, “Final Report – Life Cycle Inventory of 100% Postconsumer HDPE and PET Recycled Resin from Postconsumer Containers and Packaging (2010),” adds data on two commonly recycled plastics.
Known as a life cycle inventory, or simply LCI, the studies offer a cradle-to-resin (or ”Cradle-to-Gate”) picture of plastics production. These data also are publicly available through the U.S. LCI Database, a project of the U.S. Department of Energy and its National Renewable Energy Laboratory. The results of this analysis are presented in both English and metric units for the convenience of both U.S. and international users.
Project Scope
Part I: This newest report, “Cradle-to-Gate Life Cycle Inventory of Nine Plastics Resins and Four Polyurethane Precursors (2010),” provides current data that quantify the total energy requirements, energy sources, atmospheric pollutants, waterborne pollutants, and solid waste resulting from the production of commonly used plastic materials in North America. The plastic resins studied are: High-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), polyethylene terephthalate (PET), general-purpose polystyrene (GPPS), high-impact polystyrene (HIPS), polyvinyl chloride (PVC), and acrylonitrile-butadiene-styrene (ABS). The four polyurethane precursors include flexible foam polyurethane (PU) polyether polyols, rigid foam PU polyether polyols, methylene diphenylene diisocyanate (MDI), and toluene diisocyanate (TDI).
The new data (updated from 2007) reflect a harmonization of LCA methodologies in the United States and Europe consistent with ISO standards 14040 and 14044 for life cycle inventories. Although data reported for certain categories may have changed since the 2007 report was issued, these changes reflect differences in methodology rather than actual performance.
In addition, the 2010 study offers more intermediate data as well as current industry data from producers. The resulting contributions to the U.S. LCI Database are based on data collected specifically for this project from 17 resin/precursor manufacturers, representing more than 80 plants in North America. Supplementary data for some upstream unit processes come from Franklin Associates’ LCI database. Data for the production and combustion of fuels used for process and transportation energy were borrowed from the U.S. LCI Database for this analysis.
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Part II (Recycled Resins): In 2010, the plastics industry released a second “cradle-to-gate” study, which confirms that recycling plastics, specifically PET and HDPE, results in significant savings in energy and greenhouse gas emissions. The study, “Final Report – Life Cycle Inventory of 100% Postconsumer HDPE and PET Recycled Resin from Postconsumer Containers and Packaging (2010),” employs life cycle methodology to quantify the energy requirements, solid wastes, and atmospheric and waterborne emissions for the processes required to collect postconsumer HDPE and PET packaging, sort and separate the material, and reprocess it into clean recycled resin.
Life Cycle Studies
All manufacturing processes have both inputs and outputs. A life cycle inventory (LCI) involves the compilation and quantification of inputs and outputs for a given product system throughout its life cycle.
A life cycle approach provides the information necessary to understand how manufacturers’ choices influence what happens at each stage throughout a product’s life so that we can balance trade-offs and make informed decisions that can help reduce overall burdens to the environment. In this regard, LCI studies are an essential source of information for government, scientists, manufacturers and retailers.
The cradle-to-gate LCI presented in this 2010 study quantifies the total energy requirements, energy sources, atmospheric pollutants, waterborne pollutants, and solid waste resulting from the production of nine plastic resins and four polyurethane precursors. It is considered a cradle-to-gate LCI (rather than a complete cradle-to-grave LCI) because this analysis ends at the resin/precursor production process. Therefore, the resin/precursor data in this report are intended to be combined with additional data on the fabrication, use, and end-of-life disposal or recycling of individual products to create full life cycle inventory studies. The methodology used for this inventory is consistent with the methodology for LCI in ISO standards 14040 and 14044.
NOTE: Although these data are a critical part of a full life cycle assessment, they do not provide a complete basis from which to compare the environmental performance of various materials. It is not uncommon for different materials to require different fabrication processes or to have different transportation or secondary packaging requirements even when they are used to produce similar end products. Therefore, it cannot be assumed that materials production data alone provide an equitable platform from which to compare the environmental performance of one material versus another. Only a complete cradle-to-grave life cycle assessment can provide a reliable basis from which to compare the full quantification of energy use, emissions and waste of one complete product system versus another.
Publicly Available Plastics LCI Data – U.S. Life Cycle Database Project
The U.S. LCI Database project is a public-private partnership that was established with funding from the U.S. Department of Energy (DOE), Environmental Protection Agency (EPA), and General Services Administration (GSA). Industry contributions to this effort include in-kind data (e.g., aluminum, plastics, wood).
Providing plastics data to the U.S. LCI Database has several important benefits. Once the major materials databases are completed for plastics, aluminum, steel, wood, paper, and glass, efforts can be shifted toward gathering data on downstream manufacturing. This includes transformation (fabrication) processes such as injection molding, blow molding, and the like. Gathering this information is the next step in developing a full product LCI. Major customers of all materials (e.g., building and construction, automotive, packaging, and electrical and electronics market sectors) have expressed the need to access LCI data on transformation processes in order to make informed decisions about the sustainability of various processes.
The U.S. LCI Database provides publicly available up-to-date LCI data that can be used for many purposes, such as benchmarking for product/process improvement, impact assessments, and so on.
Resources and Links:
National Renewable Energy Laboratory: U.S. Life-Cycle Inventory Database
