Page 208 - Materials Chemistry, Second Edition

194 LIFE CYCLE ASSESSMENT HANDBOOK

observations that people dislike a landscape polluted with gar-
bage chaotically scattered about, but enjoy the order of a clean
landscape with garbage neatly contained, suggest that ideas
relating exergy and order in the environment may involve
human values (Hafele, 1981) and that human values may in
part be based on exergy and order.

One important approach to reducing the environmental impacts associated
with waste exergy emissions, resource degradation and order destruction,
which is consistent with LCA, is increased efficiency: Increased efficiency pre-
serves exergy and order by reducing the exergy necessary for a process, and
reduces waste exergy.

8.4.2 Rationale of ExLCA
LCA has proven over the recent decades to be a useful method for eval-
uating the environmental impacts of goods or services by assessing their
entire life cycles. LCA nonetheless has several challenges. First, LCA is an
extremely data intensive approach since it requires information about emis-
sions and resource use for all processes in the life cycle. Second, difficulties
can arise when combining data in disparate units with different levels of
uncertainty.
Despite recent advances in LCA and the development of relevant databases
and software, significant opportunities exist for improvement of the method.
In particular, conventional LCA is sometimes inadequate for the analysis of
new and fundamentally different technologies due to a lack of inventory data
about inputs and outputs and little knowledge about the potential human and
ecosystem impacts of the products, by-products and wastes of new technolo-
gies. The development of life cycle inventory databases and studies on the
toxicological and other impacts of new emissions requires extensive effort and
time.
Unique and generalized proxy indicators for these cases may be provided
by using thermodynamics. This observation is based in part on the fact that
industrial and ecological processes and their life cycles are networks of energy
flows, which are governed by the laws of thermodynamics (Bakshi and Ukidwe,
2006). In particular, a method to address thermodynamic irreversibilities dur-
ing the life cycle of the system is necessary in order to reduce its environmental
impacts, and exergy provides such information in a practical manner which is
usually clearer than other thermodynamic approaches. ExLCA has been devel-
oped to provide this and other relevant thermodynamic information, and is
proving to be a useful tool for investigating and evaluating the environmental
impacts corresponding to exergy destructions over the life cycle of a process or
system. These exergy destructions relate to exergy efficiencies, which provide
a true measure of the approach to ideality and thereby the actual margin for
efficiency improvement.