Energy And Environmental Assessments

As discussed, a thorough evaluation of the environmental impact of alternative types of packaging systems requires a life-cycle assessment (LCA) that takes into account all impacts from "cradle to grave." However, all such analyses must be constrained within a set of boundaries, and the choice of boundaries can make a difference in the conclusions that are drawn. The more comprehensive and detailed is the analysis, the greater is its cost. Further, numerous assumptions are required, especially when moving from the life-cycle inventory that documents inputs and outputs to the impact analysis, which describes the effects of those inputs and outputs. This effort is inextricably tied to value judgments about the relative equivalence of greatly differing types of items listed in the inventory. Even in the life-cycle inventory, assessments will vary in the data used. Some studies opt for use of publicly available data only and are often criticized on the grounds that recent improvements in processes are not recognized. Others use industry sources for recent data to reflect such improvements and are criticized because the data is not available for public scrutiny. In some European countries, government policies require use of government-approved computer-based LCA models, which may not provide all relevant data and assumptions for independent evaluation. Therefore, use of LCA, while theoretically the only fully justifiable method for evaluating the environmental consequences of packaging decisions, in practice still needs considerable development before it can become a useful tool. As a consequence, there has been considerable interest in developing shortcut methods that, while not evaluating all environmental impacts of packaging (or other) alternatives, can more readily be employed for guidance in making environmentally sound choices.

Life-cycle analysis of plastics resins themselves is outside the scope of this chapter (see Chapter 3). Our focus is the additional environmental impact associated with the conversion of plastics resins to packaging materials and the use and disposal of these materials.

One of the most wide-ranging LCA packaging studies is the massive report done by the Tellus Institute on the major packaging materials, including plastics [24]. However, this study examines only polymer production and ultimate disposal. It does not include processing steps such as forming and molding.

A study by Franklin Associates in 1992 examined the energy requirements for plastics and their alternatives in packaging materials [25]. Energy requirements for fabrication were presented for blow molding, injection molding, fabrication of film, and thermoforming and are summarized in Table 4.1. Analyses of energy requirements for resin production and for manufacture, fabrication, and recycling systems for several types of resins and container systems are shown in Table 4.2. Other studies of energy consumption for plastic packaging are also available [26, 27].

A study published in The Netherlands in 1992 [28] evaluated the environmental impact of polystyrene, paper, and porcelain coffee cups. The cups were made from a 50:50 blend of high-impact polystyrene (HIPS) and general-purpose

Table 4.1 Energy Requirements for Plastics Processing [25]

Process

Process Energy (MJ/kg) Electricity Natural Gas

Transportation Energy (MJ/kg)

Total Energy (MJ/kg)

Blow molding PET

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