Environmental Engineering Reference
In-Depth Information
processing of materials, production packaging materials such as plastic and cardboard, pro-
duction of electricity, and disposal of waste materials can be generally found in commercial
LCA databases (Roy et al., 2009).
During this step, data needs to be validated and expressed in terms of the functional unit
that was defined during goal-and-scope setting. In the case of energy, all sources, such as fuels
and electricity, need consideration, including efficiencies and losses.
Generally, the results of the inventory analysis are presented in a table that contains all the
inputs and outputs of different processes encompassed by the boundaries. Table 4.3 illustrates
a detailed LCA inventory analysis for the production of pasta in Italy. This study divided the
pasta production system in five different subsystems (called “unit process” in the original),
specifically production of durum wheat, production of semolina, pasta production, plastic
packages, and cardboard packages.
Allocation
Most food processes are not linear, and they may contain multiple inputs and multiple outputs.
For instance, in poultry processing, the main product is meat; however a variety of
co-products—feathers, blood, skin, bones, offal, and meat trims—are by-products generated
during processing. These by-products are subsequently transformed into during other
products—poultry meals, blood and feather meals, and poultry fat—and used as feed for farm
and companion animals. Therefore, when conducting a life cycle inventory analysis of the
production of poultry meat, the environmental burden needs to be proportionally divided
between the “center-of-the-plate-cuts” and the by-products. In LCA terms, the procedure of
determining how much of the environmental burden is caused by each process or product
when multiple processes or products are present is called allocation (Fig. 4.5). Because there
is not a universal rule to make this decision, assigning allocations is one of the most
controversial issues in LCA (Reap et al., 2008).
ISO 14044:2006 provides guidelines to deal with allocation situations in a three-step
procedure (ISO, 2006b):
1. Avoid allocations as much as possible by dividing the process in two or more separate
processes with inputs and outputs for each of them; or by “expanding the product system
to include the additional functions related to the co-products” taking into account the
requirements of reuse and recycling.
2. If allocations cannot be avoided, partition inputs and outputs between their “different
products or functions” using “underlying physical relationships between them.” For
instance, using relative mass flows or energy densities.
3.
When physical relationships cannot be established, the standard recommends the use of
other relationships, for instance economic value.
In most food-production systems, allocations are difficult to avoid, especially when
by-products are involved or when there are multiples inputs that are by-products of previous
processes. For instance, in fish farming the feed may contain poultry feather and blood meals,
poultry protein meals, corn gluten meal from corn wet-milling, and soybean meal from
soybean oil extraction. Therefore, when conducting an LCA of a fish farm, this presents a
challenge because the environmental burden of each of these ingredients needs to be back-
calculated to where the by-product was produced (Ayer et al., 2007).
Multiple allocation criteria are possible. So, when dealing with these systems, the ISO
14044:2006 recommends a sensitivity analysis that compares allocations made using different
