Abstract:

This study examined ten representative toilet models across four categories in rural China. A full life cycle carbon accounting model was constructed, covering toilet construction, fecal collection, storage, treatment (operation) and resource utilization. Emission factor method was used to quantify carbon emissions at each stage, identify key emission sources and propose mitigation strategies to support emission reduction in rural areas under China's dual−carbon goals. The results showed that: (1) carbon emissions varied across ten toilet models. Between the two sanitary dry toilets, the urine−diverting dry toilet had lower per capita carbon emissions (57.62kgCO₂e·cap⁻¹·y⁻¹) and achieved a mitigation effect of 19.10kgCO₂e·cap⁻¹·y⁻¹ through resource utilization. Among the six sanitary flush toilets, the biogas−linked toilet had the lowest per capita emissions (41.82kgCO₂e·cap⁻¹·y⁻¹) and the highest mitigation potential (176.74kgCO₂e·cap⁻¹·y⁻¹), the three−septic−tank toilet had the highest per capita emissions (113.25kgCO₂e·cap⁻¹·y⁻¹), unimproved flush toilets and pit latrines emitted 185.67kgCO₂e·cap⁻¹·y⁻¹and 48.09kgCO₂e·cap⁻¹·y⁻¹, respectively. These two models had no mitigation. (2) The main emission stages were toilet construction and fecal treatment (operation), accounting for 8.43%–56.11% and 48.59%–89.88% of total emissions respectively (excluding biogas−linked toilet). Major carbon sources included embodied carbon in construction materials, methane (CH₄) released during anaerobic degradation, and nitrous oxide (N₂O) conversion. (3) Strategies for fecal sludge−related carbon mitigation include sanitary upgrades, substitution with low−carbon materials and optimization of resource utilization pathways. This study identified the emission hot spots and feasible mitigation measures for rural toilet renovation through life cycle carbon accounting, and provided a scientific basis for advancing fecal waste resource utilization and supported China’s carbon peaking and neutrality goals.

Key words: Rural toilet renovation, Fecal resource utilization, Life cycle, Carbon emissions, Mitigation strategies