Greenhouse gas emissions from sanitation and wastewater management systems: a review

There is growing awareness of the contribution of sanitation systems to greenhouse gas (GHG) emissions globally, and hence to climate change. However, there is a lack of comprehensive insight into emission sources dis-aggregated across the entire sanitation chain. This study presents a detailed review and analysis of emission sources from both sewer-based and non-sewered sanitation systems, with a focus on both fugitive emissions and those related to system operation. Our analysis highlights evidence gaps in several areas in the literature: quantifying emissions from non-sewered sanitation systems, with particular gaps related to technologies like biogas toilets and composting toilets; oversight of contextual factors such as environmental conditions and infrastructure operational status in GHG accounting; a dearth of holistic GHG emission studies across the entire sanitation chain comparable to those in the solid waste management sector; and inconsistencies in GHG measurement methods. By pinpointing these gaps, this review provides a robust reference for planning climate mitigation strategies for sanitation and wastewater management systems, emphasizes the urgent need for the incorporation of climate-smart solutions in the sector e.g. in the design of new and retrofitted infrastructure, and aims to bridge the sustainable development goals related to sanitation and climate action.