Greenhouse gas emissions from sanitation systems remain underquantified, particularly when considering the entire service chain. Previous studies have largely focused on emissions from containment, with limited attention to later stages such as collection, transport, treatment and disposal. To address this gap, this research comprehensively estimates greenhouse gas (GHG) emissions from sanitation systems in Lahan municipality, Nepal. We used an extended version of the IPCC-based Tier-1 approach. Data collection included a household survey and key informant interviews. In scenario A, the baseline total annual emissions are 8.7 Gg CO2e, mostly from the digestion of faecal sludge in the containment (7.3 Gg CO2e). In scenario B, when a projected faecal sludge treatment plant (FSTP) is built and in operation, annual emissions reach 10.0 Gg CO2e, driven by methane emitted by the anaerobic digester in the plant. Scenario C considers climate mitigation strategies: increasing the share of households emptying their containments, increased emptying frequency and adding of methane capture in the FSTP. This can reduce annual emissions to 7.9 Gg CO2e per year, which is 21% less than in scenario B. Our results suggest that methane capture in the FSTP is the most critical mitigation strategy.
Joshi et al. (Thu,) studied this question.