Table 13.2 specifies the electricity and heat sources used in the publications in our study. The electricity mix is determined by the country where the production is supposed to take place; in some publications, electricity and heat consumption are totally or partially covered by internal production from the microalgae, either by anaerobic digestion of the oilcakes

NC = Not communicated.

(Stephenson et al., 2010; Brentner et al., 2011; Campbell et al., 2011; Clarens et al., 2011) or of the algal biomass (Clarens et al., 2011; Collet et al., 2011) or by direct combustion of microalgal biomass or extraction residue (Clarens et al., 2011).

Most of the authors (Lardon et al., 2009; Baliga et Powers, 2010; Sander and Murthy, 2010; Stephenson et al., 2010; Khoo et al., 2011) underlined the important contribution of energy consumption to the global-warming potential of algal energy productions. The sensitivity of this choice has been assessed with inventories from the EcoInvent database and the ReCiPe impact assessment method (Goedkoop et al., 2009) in a hierarchical perspective. With this perspective, characterization factors of the global-warming potential are the ones defined by the IPCC (IPCC, 2006). As shown in Figure 13.3, climate change impact can vary by a factor of two according to the chosen electric mix. Consequently, the potential reduction of green­house gases by producing bioenergy from microalgae is strongly correlated with the origin of the electricity. It is important to note that the variations of endpoint impacts (i. e., human

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health, ecosystems, and resources) are almost identical to that of the climate change impact. This underlines the strong dependence of all the impacts on the energy mix composition.