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352   Biofuels for a More Sustainable Future


                          Table 12.8 The reference series
                          Criteria           Reference series
                          CC                 [0.3149 0.6016]
                          TA                 [0.1991 0.3609]
                          H.Tox              [0.0941 0.1584]
                          PMF                [0.0796 0.1341]
                          LCC                [0.1677 0.2398]
                          SB                 [0.0319 0.0668]
                          CED                [0.0227 0.0390]
                          FS                 [0.1064 0.2094]



          Table 12.9 The correlation degree of the series of each alternative to the reference
          series
                               Wheat-based     Corn-based    Cassava-based
          Correlation degree   5.4678          7.4517         6.2592
          Ranking              3               1              2


             According to Eqs. (12.21)–(12.23), the reference series can be obtained,
          and the results are presented in Table 12.8.
             Finally, the correlation degree of the series of each alternative to the ref-
          erence series can be determined by Eqs. (12.24)–(12.25), and the results are
          presented in Table 12.9.
             Therefore the corn-based pathway for bioethanol production was recog-
          nized as the most sustainable, followed by cassava- and wheat-based path-
          ways in the descending order.


          4 Discussion

          In order to investigate the effects of the weights of the criteria on the sus-
          tainability ranking of the three pathways for biofuel production, sensitivity
          analysis was carried out by changing the weights of the criteria for sustain-
          ability assessment of biofuel production pathways, and the following nine
          cases have been studied:
             Case 0: Equal weights—an equal weight (0.1250) was assigned to the
          eight criteria for sustainability assessment of biofuel production pathways.
             Case 1–8: A dominant weight (0.4400) was assigned to each of the eight
          criteria in each case and all the other nine criteria were assigned an equal
          weight (0.0800).
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