To understand the opportunities for carbon sequestration via biochar, we evaluated the user cost as a function of carbon sequestration credits (i.e., value of carbon) when the Biogenic Refinery would be implemented in place of a more common sanitation system. For this reference system, we estimated the GHG emissions from a sanitation system consisting of pit latrines, transportation of fecal sludge to a centralized treatment facility, and anaerobic treatment (the benchmark system shown in Figure ). Holding all equivalent parameters consistent between the technologies, we calculated the user cost of the system by including the value of mitigating carbon emissions (Figure ). Although the current carbon market is fragmented, estimates suggest that an average value of 34 -64 USD•Mg -1 of CO2 by 2025 can set the course for a 2050 net-zero CO2 emission target. Biochar, a relatively stable carbon product, can fetch on average 181 [111 -686] USD•Mg -1 of CO2 on current markets. At 150 USD•Mg -1 of CO2, the user cost of the mixed excreta scenario was 0.03 [0.01 -0.08] USD•cap -1 •d -1 and the source-separated excreta scenario was 0.05 [0.03 -0.11] USD•cap -1 •d -1 . The user costs are entirely offset by carbon at an average cost of 351 USD•Mg -1 of CO2 for the mixed excreta and 380 USD•Mg -1 of CO2 for the sourceseparated excreta. It is notable that at over 412 USD•Mg -1 of CO2 the source-separated scenario becomes less expensive than the mixed excreta scenario. In this analysis, we are only giving value to the carbon content. Source separation potentially could lead to higher quality biochar and may allow for a broader set of potential uses with higher economic value. Source separation could also produce a more consistent feedstock to pyrolysis, allowing for better optimization of operating conditions. Both feedstock and operating conditions have been shown to influence carbon stability. Producing biochar with constant properties and higher carbon stability may create greater economic opportunities, including carbon sequestration credits. Future studies may provide a more in-depth accounting of carbon and explore how biochar from fecal sludge compares to biochar from other feedstocks.