Page 188 - Materials Chemistry, Second Edition

186 9. Life cycle decision support framework: Method and case study

where, g i is the goal of the ith criterion where the maximum normalized value of the ith cri-
+
terion is selected; d i and d i are the redundancy variables to measure the differences between
planned alternatives and the goal; w i is the weight for the ith criterion and y ij is the normalized
data of the ith criterion with respect to the jth alternative; and i¼1, 2, …, m, and j¼1, 2, …, n.
∗
The only a j ∗ that satisfies a j ∗¼1 indicates the j th alternative is the best option based on its
performance in all criteria and preferences from multiple decision makers.

9.4 Case study

In this section, a case study regarding used cooking oil management was studied to better
illustrate how to use MCDM to deal with selection problems based on LCSA results. In this
case study, the best alternative among three used cooking oil domestic management sys-
tems was analyzed according to the performances in 29 criteria from environmental, eco-
nomic, and social perspectives. The three options analyzed in this chapter include
collection through school (SCH), collection from door to door (DTD), and collection through
urban collection centers (UCC). The SCH system indicates an oil reuse and recycling system
based on schools. In this system, schools are the collection points for the used cooking oil.
All participants deliver waste oil generated from their lives to the schools by their own con-
tainers. The oils are collected and transported once a month by authorized organizations by
van to a special working center. This special working center works as the transport station to
collect all used cooking oils in a 1000t storage container and to transport them further to a
biodiesel plant by tanker. During the process, the cleaning of empty containers is conducted
by an industrial dishwaster and there are workers with a degree of disability. The DTD sys-
tem is almost the same with SCH, except that the collection points change from schools to
the houses of citizens. In the UCC system, users bring their used cooking oils directly to the
urban collection center. The oils in the urban collection center will be transported to biodie-
sel plant once the 1000t storage container in the urban collection center is full. In this case,
the participants should clean their own containers. The proceeding flows of these three op-
tions are shown in Fig. 9.2.
From the view of criteria, the data in environmental, economic, and social aspects were
adapted from LCA, LCC, and SLCA respectively. The environmental criteria involve abiotic
depletion (AD), acidification (AC), eutrophication (EU), global warming (GW), ozone layer
depletion (OPD), human toxicity (HT), fresh water aquatic ecotoxicity (WAE), marine aquatic
ecotoxicity (MAE), terrestrial ecotoxicity (TE), photochemical oxidation (PO), and energy con-
sumption (ED). The economic criteria include personnel, transport, collection container, stor-
age container, CO 2 costs, total cost, and total cost without CO 2 . As for social aspect, the criteria
used to evaluate in this case study were total employees, total working hours, total employees
with disabilities, total employees with higher education, total employees with basic educa-
tion, equal opportunities for sexual reasons, equal opportunities for disabilities, children’s
environmental education, local employment, public commitments to sustainability issues,
and contribution to economic development. The data of LCSA results were adapted from pre-
vious study of LCSA with regard to used cooking oil management (Vinyes et al., 2013)as
shown in Table 9.4.