As cities in low- and middle-income countries expand rapidly, sanitation infrastructure struggles to keep pace, with nearly 700 million people still lacking even basic sanitation access. Lack of sanitation access leads to open defecation, overflowing pit latrines, and untreated discharge into waterways – with health impacts disproportionally felt by the poorest and most vulnerable parts of the population. But in the rush to provide safe sanitation services, are we thinking enough about their impact on the climate?

Recent research reveals that some sanitation solutions release significant methane, a greenhouse gas 25 times more potent than carbon dioxide[1]. A study conducted by USAID Urban Resilience by Building Partnerships and Applying New Evidence in WASH (URBAN WASH) projected methane emissions associated with future sanitation scenarios in urban Sub-Saharan Africa. It estimates that sanitation systems in urban sub-Saharan Africa currently contribute 3-5% of the region’s total annual anthropogenic methane emissions. This percentage is projected to increase to nearly double by 2030 if current technologies continue to be adopted (see Figure 1).

Figure 1: Estimated emissions from sanitation in urban Sub-Saharan Africa (SSA) (excluding South Africa) as a proportion of total annual anthropogenic methane emissions

With limited coverage of sewerage in low- and middle- income countries, most of these emissions come from household waste containment systems, such as pits and septic tanks. As these facilities fill, they generate methane. And, once emptied, the treatment of the sludge, like the treatment of wastewater, can release significant amounts of methane. Promising solutions exist to curb these emissions during containment and treatment. This study assessed interventions across the sanitation chain – waste containment and treatment.

Some of the solutions include reducing water content in containment systems, such as by lining dry pits in areas with high groundwater tables. But methane abatement solutions are still missing for wet containment technologies. At treatment plants, solutions like composting, drying beds, or that directly capture methane during treatment, can mitigate emissions. Integrated sanitation service models like container-based sanitation, which safely captures waste in a frequently emptied container that is taken for treatment off-site, are an alternative to traditional systems. However, barriers impede scaling of these solutions.

Here are four ways we can work collaboratively to design climate-smart sanitation systems while also protecting public health:

1. Implement proven solutions where they are contextually appropriate.
2. Experiment with promising interventions to generate evidence for further scaling.
3. Innovate to address gaps in the identified abatement approaches.
4. Create a favorable enabling environment to increase awareness of the climate impact of sanitation systems and incentivise the adoption of more climate-friendly technologies and services.

Some key questions remain. For approaches that we know can eliminate, or greatly minimise, methane emissions, there are still questions about how to make them viable in low- and middle-income countries. For many of the promising approaches, we still need more empirical research to understand their emission profiles at scale. And we still need research and development of new technologies and novel approaches.

While more research is needed, the urgency of climate change means we need action today. Implementing no-regret solutions where possible, generating evidence, supporting innovation, and strengthening the enabling environment must start now.

The sanitation sector aims to eliminate public health hazards. By integrating climate-conscious planning, the sanitation sector can simultaneously become a part of the climate solution. Turning the sanitation sector from a driver to a reducer of emissions requires rethinking how we approach sanitation but can be done without sacrificing our public health goals. As access to sanitation expands across rapidly developing countries over the next 10-15 years, now is the time to bring climate into the conversation. At the moment, the sector’s greenhouse gas footprint is rapidly expanding; it is our responsibility to ensure that we do all we can to reduce and reverse this trend.

Want to learn more about designing lower-methane sanitation systems? Attend the workshop “Climate impact of sanitation technologies: Where are we headed?” on Thursday 14 December, Session 2 in Room MH1 at the IWA Water and Development Congress & Exhibition in Kigali, Rwanda on Thursday 14 December 2023 where we will explore research insights, challenges, and potential solutions to curb methane emissions from sanitation.  You can also access URBAN WASH’s recent publication on this topic here: “Managing the climate impact of human waste”.

Join us and other water and development experts who will convene to find relevant solutions tailored for low- and middle-income countries. Registration is open.

[1] Johnson, J., Zakaria, F., Nkurunziza, A. G., Way, C., Camargo-Valero, M. A., & Evans, B. (2022). Whole-system analysis reveals high greenhouse-gas emissions from citywide sanitation in Kampala, Uganda. Communications Earth & Environment, 3(1), 80.

*WS 36 Mitigating The Climate Impact Of Sanitation: Where Are We Headed? on Thursday 14 December, Session 2, Room MH1