Plastics Engineering - May 2014 - 36
Process Engineering for Recycled Polymers:
Life-Cycle Assessment
By Donald G. Baird and Dimitris I. Collias
Note: Below is an excerpt from Chapter 11 of the book Polymer
Processing: Principles and Design, 2nd ed., by Donald G.
Baird and Dimitris I. Collias (2014, John Wiley & Sons).
t
he decision to recycle polymers is by no means
straightforward. in some instances, recycling polymers can lead to more energy usage and more
pollution than merely disposing of them in landfills. the
decision to recycle polymers depends on the ultimate goal.
is it to reduce consumption of raw materials (i.e., feedstock)? is it to reduce the consumption of fuel? is it to reduce
the generation of solid waste?
to determine whether recycling is the appropriate option
and what type of recycling option should be selected, one
turns to a systems analysis which accounts for all energy and
raw materials used to produce a product or process and all
wastes produced. this type of analysis is referred to here as
life-cycle assessment (lca), but other names are often used,
such as ecobalance, cradle-to-grave analysis, and lifecycle
analysis.
lca is used defensively to justify recycling and offensively to improve products and processes and help select the
appropriate polymers and processes for various applications. although considerable discussion of the technique and
its application is given in the books by curran1 and Horne et
al.2, we present an overview of the topic with enough detail
to hopefully make the concept useful to the process engineer.
Figure 1: Life-cycle assessment conceptual model
(data from Curran1).
Life-Cycle Concepts
the lca conceptual model is shown in Figure 1. at the center of lca is initiation or scoping, in which the goals of the
study and the system boundaries are defined. all operations
that contribute to the life cycle of the product or process fall
within the system boundaries as shown in Figure 2. the
environment is the surroundings for the system. inputs to the
system are the natural resources, including energy resources.
36
Figure 2: Life-cycle system concept showing the
boundaries on which the life-cycle assessment must
be performed (reprinted by permission of the publisher from Curran1).
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Plastics Engineering - May 2014
Table of Contents for the Digital Edition of Plastics Engineering - May 2014
Contents
Plastics Engineering - May 2014 - Cover1
Plastics Engineering - May 2014 - Cover2
Plastics Engineering - May 2014 - Contents
Plastics Engineering - May 2014 - 2
Plastics Engineering - May 2014 - 3
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Plastics Engineering - May 2014 - Cover3
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