Whole-system analysis reveals high greenhouse-gas emissions from citywide sanitation in Kampala, Uganda

Abstract

Global estimates of emissions of greenhouse gasses do not take into account the complex service chain in rapidly growing cities in low- and middle-income countries. This paper presents an end-to-end analysis to estimate emissions from all stages of the sanitation-service chain, using Kampala in Uganda as an example. We show that emissions associated with long periods of storage of faecal waste in sealed anaerobic tanks (49%), discharge from tanks and pits direct to open drains (4%), illegal dumping of faecal waste (2%), leakage from sewers (6%), wastewater bypassing treatment (7%) and uncollected methane emissions at treatment plants (31%), are contributing to high levels of greenhouse-gas emissions. Sanitation in Kampala produces 189 kt CO2 e per year, which may represent more than half of the total city-level emissions. Significant further empirical and modelling work is required to update estimates of greenhouse-gas emissions from sanitation systems globally.

Urbanization and seasonality strengthens the CO2 capacity of the Red River Delta, Vietnam

“…The natural contribution of tropical riverine CO 2 fluxes to the global C budget is comparatively minimal (<600 Tg C yr −1 ). However, our findings are consistent with recent research showing that water quality degradation through increasing lentic/stagnant waters from river channelization, sewage treatment infrastructure, and pollution load in densely populated cities, could significantly strengthen the potential for river CO 2 outgassing [11][12][13]51]. Annual pCO 2 in the Day River was 1.8-fold higher than in the Red River and up to two-fold greater during the dry season than the median of pCO 2 in >20 sub/tropical rivers.…”

“…To help mitigate these harmful effects introduced by urban development, we suggest carrying out responsive water course management actions to increase river flows in problem areas during the dry season [22,40], along with the implementation of green infrastructure that prioritize the natural hydrological functions of the river [54]. Improving sanitation infrastructure and management in urban centers [51] and strengthening the engagement with local government to exchange research findings and support policy making on water management, including sustainable agricultural development (e.g. use of fertilizers) [42], could further help reducing nutrient load and greenhouse gasses.…”

Resource recovery technologies as microbial risk barriers: towards safe use of excreta in agriculture based on hazard analysis and critical control point

“…We describe that long storage or retention times are necessary for disinfection; however, greenhouse gas emissions from fecal sludge can increase significantly with increased storage time. 141,142 Reid et al demonstrated that replacement to a low-CH 4 emission technologies (e.g., composting toilet) yields co-benefits for both greenhouse gas mitigation and water and sanitation development. 141 Second, some novel thermal treatment systems are not included that have gained traction in recent years, e.g., Omni Processors.…”

Causes and consequences of recent degradation of the Magdalena River basin, Colombia

“…Transforming the river basin and hydrological characteristics may lead to eutrophication, hypoxia, HABs, and excess partial pressure of aquatic CO 2 (Wang et al 2017; Zhang et al 2021). Projected urban development in the Magdalena River basin will thus likely increase water demand intensifying stagnant waters, oxygen drawdown, and potentially associated HABs among urban tributaries, especially during dry periods (Johnson et al 2022).…”