Page 233 - Materials Chemistry, Second Edition

220 LIFE CYCLE ASSESSMENT HANDBOOK

United States (Hendrickson, Lave, & Matthews, 2006). However, since the EIO
model uses aggregated sector data, the data can lack the precision a process
LCA would have (Huijbregts, et ah, 2001). For example, you could not use an
EIO-LCA to try to compare conventional and organic corn farming. Both of
these processes are in the grain farming sector, and would therefore result in
identical results, which is certainly not valid. One way to have both the com-
pleteness of EIO-LCA as well as the precision of process LCA is to use a hybrid
LCA method such as the Ecologically-Based LCA.

9.3 Ecologically-Based Life Cycle Assessment

Ecologically-Based Life Cycle Assessment (Eco-LCA) is framework for LCA
being developed by researchers at The Ohio State University's Center for
Resilience. It can be used to develop LCA models at the process or economy
scales, or by combining both methods resulting in a hybrid LCA. In a hybrid
study, the most important parts of the process are modeled using the process
LCA. The less important parts are then modeled at the economy scale, usually
using the economic input-output models. For example, in assessing corn farm-
ing, it may be decided that the steel used to make a tractor is not very impor-
tant, so that sector can be analyzed through the economy scale model.
In Eco-LCA, the novelty comes from its inclusion of resources that are not
normally in an LCA. Traditionally, an LCA will either compare water footprint,
energy requirements in fossil fuel equivalents, or emissions; however, Eco-
LCA contains many of the ecosystem goods and services that were assessed
in the MEA, and it even includes some supporting services that were not
included in the MEA. Following is Table 9.2 of ecosystem services included in
Eco-LCA(Zhang, Baral, & Bakshi 2010).
Of course, not all of these different goods and services can be directly com-
pared, as they have different units that cannot be added together. It is impos-
sible to directly compare a kilogram of a mineral with a joule of energy and
decide which is worth more. Instead, we take the different goods and services,
and convert them to exergy and emergy. Exergy is the maximum amount of
work a system can do. For example, a joule of natural gas cannot do a joule's
worth of work; the joule of natural gas would have to be converted to work,
and that conversion will lessen that amount of work the natural gas can do,
as per the second law of thermodynamics. Considering all thermodynamic
work to be equivalent, these exergy values can be directly compared. They
also give a measure of the amount of work that can be accomplished, which
will be much more useful than energy in some situations (Zhang, Singh, &
Bakshi, 2010).
Another method that will allow for comparison of all the various ecosystem
goods and services is to convert the physical flows to industrial plus ecological
(I+E) exergy. Unlike the previous exergy values that only look at the work that
will be done from industrial sources, the I+E exergy values will also include
the work that is done by ecological sources. This total industrial and ecological