A life cycle analyst’s motives for carrying out an LCA can have important implications for the results of a study. These “zero order” assumptions are often rooted in the type of LCA being performed. LCAs fall broadly into one of two categories. Attributional LCAs are those in which all of the environmental impacts associated with a product or process are compiled and reported [1]. Consequential LCAs are those that evaluate the impacts of making a particular change to a process or prod­uct, or compare two technologies with related functions. Consequential LCAs are often more straightforward to perform because they permit for the canceling of unit processes or systems that are common between the technologies of interest. In the case of algae, most published LCA studies are attributional since there are few tech­nological systems existing to which algae-to-energy can be compared. There is, however, an important role for consequential LCA as this field moves forward; since they can help identify and quantify what impacts might arise from evolving algae technologies. The decision to undertake an attributional or a consequential LCA is manifest most notably in decisions about the system boundaries and func­tional units of the study. System boundary decisions include all the elements associ­ated with geographic areas, natural environments, time horizons, and others. The functional unit is the quantitative basis for the life cycle comparison and differs depending on the processes to be compared. Both are explored here.