A critical aspect of the QSD methodology involves the incorporation of uncertainty. For each uncertain parameter (290 parameters for the mixed excreta and 319 parameters for the sourceseparated excreta), distributions are defined (see appended spreadsheets for all parameters) and, an additional variability of up to 25% is added to each unit cost and environmental impact factor. This variability was added to account for factors such as the spatial heterogeneity of material prices and impacts. For all scenarios, Monte Carlo simulation with Latin hypercube sampling (10,000 samples) was used to include uncertainty. This process produced a distribution of results for which the median, 5th percentile, and 95th percentile values from the uncertainty analysis are shown in the results. The input and output distributions from the simulations also were used to calculate Spearman's rank correlation coefficients as a measure of results' sensitivity to individual parameters. In this context, sensitivity refers to the degree to which an output (i.e., costs and GHG emissions) correlates with a single input parameter. Spearman's coefficients are calculated by ranking the values in each input and output distribution (e.g., the lowest value is assigned a rank of 1, and the second lowest is assigned a rank of 2, and so on) and determining the correlation between these ranks. This correlation is shown by a coefficient value that represents the degree to which an arbitrary monotonic function can describe the relationship between the input parameter and output value. Coefficient values range from -1 and 1, with a larger absolute value signifying a stronger correlation. For this work, absolute values of coefficients are shown in the results.