To quantify the relative impact of individual design decisions on system cost and CI, pairwise comparisons were conducted. For each decision variable, a baseline for comparison was first chosen (e.g., UASB as the baseline reactor type) and other values were considered alternatives (e.g., packed bed and fluidized bed for reactor type). All the evaluated samples were organized into baseline-alternative pairs, each of which only differs by one common decision variable. A decision variable's relative impact (∆𝑌) on a sustainability indicator (i.e., LC or CI) was calculated as the difference in the indicator values ( 𝑌 ) between a baseline-alternative pair normalized by the entire range of the indicator observed across 3,552 distinct combinations (Eq.