Page 93 - Biofuels for a More Sustainable Future
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84    Biofuels for a More Sustainable Future


             Regarding the evaluation of environmental impacts, life cycle assessment
          (LCA) is a key methodology that enables the quantification of potential
          environmental and social impacts for products, processes, and activities, pro-
          viding an indication of sustainability (Araujo et al., 2018; Neves et al., 2018;
          Coelho Jr et al., 2018; Carvalho et al., 2019).
             Recent studies related to biofuel LCA, generally, compare different
          fuel production routes from energy and environmental points of view.
          The main questions approached by a biofuel LCA are (Gnansounou,
          2018)asfollows:
          – What biofuel production route causes the lower environmental damage?
          – Are there differences in the selection of biomass, and which one is eco-
             logically better for the different production processes?
          – What is the attributable share of environmental impacts for each stage of
             production?
          – Are there margins for improvement?
          – What is the environmental behavior of the biofuel if there are changes in
             the studied scenario?
          Jungmeier et al. (2013) and Sacramento-Rivero (2012) discuss the particu-
          larities of the evaluation of sustainability in biorefineries considering the
          existence of multiple energy, food, chemical, and biomaterial products.
             In this sense, LCA can be applied in combination with optimization
          methods, as it has already been combined in other areas: with economic ana-
          lyses (Carvalho and Abrahao, 2017), with thermoeconomics (Silva et al.,
          2017), and within optimal energy supply systems (Serra et al., 2014).
             The work carried out by Gebreslassie et al. (2013), for example, utilized a
          multiobjective optimization process in an algae-based biorefinery, and max-
          imized the NPV (net present value) while minimizing the GHG emissions
          (Fig. 4.5).
             Based on the indicators of the processes employed within a biorefinery,
          we can obtain the material and energy flows associated with the inputs and
          outputs of the system, and then determine the CO 2 emissions (or any envi-
          ronmental indicator) associated, following with a comparison, as shown in
          Fig. 4.6.
             Based on refinery data, it is possible to establish minimum, maximum,
          and ideal (optimal) values for different indicators, for the several types of
          biorefineries. By plotting these data in a radar diagram (Fig. 4.7), we can
          have an idea of how much each aspect contributes. The larger area is con-
          sidered the most sustainable.
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