With the climate crisis deepening, sanitation systems must be designed to adapt. Like much of the sanitation sector, CBS is still generating evidence and refining approaches to maximise its climate benefits and resilience potential. However, CBS is increasingly seen as a climate-smart sanitation solution – cutting emissions, conserving water, and building resilience against climate shocks.
Reduced emissions with CBS
The sanitation sector now has better evidence of the significant direct methane emissions and outsized climate impact of unmanaged systems, such as faeces stored long-term in pits and septic tanks. In contrast, CBS offers an actively managed service chain: small, sealable containers are collected frequently and treated quickly, limiting emissions at every stage.
The evidence to support this has been building for several years. Following gas flux measurements of SOIL’s service in 2019, showing that composting human waste significantly reduces emissions, CBSA developed an emissions calculator using IPCC emission factors to further quantify CBS’s climate benefits. Results showed that four CBS operators were mitigating between 80–210 kg CO2e (CO2 equivalent emissions) per person per year, depending on treatment processes – equivalent to a combined total of 45,000 tonnes CO2e annually.
These findings were reinforced by a 2022 study CBSA commissioned with the consultancy South Pole, which found that CBS systems can reduce emissions by 79–93% compared to business as usual. With this growing body of evidence, CBS has been recognised by USAID and Green Climate Fund guidelines as a key climate solution for both methane reduction and adaptation.
Water scarcity
CBS provides a viable alternative to sewered systems that depend on increasingly stressed water supplies. Most CBS toilets are either waterless or use ultra-low flush technology, only needing water to clean containers, significantly reducing water demand and minimising the risk of contamination in water-scarce settings. The importance of water-efficient sanitation is particularly evident in Lima – one of the driest capital cities in the world – where Sanima operates. In Cape Town, the 2018 ‘Day Zero’ crisis highlighted similar vulnerabilities. The city narrowly avoided having to shut off taps in over a million homes and restrict residents to collecting 25 litres of water per day at designated points. Although the crisis was averted through aggressive conservation efforts and improved rainfall, it sparked a surge of interest in waterless toilet systems as a more resilient solution.
Adaptation
CBS providers are increasingly demonstrating how actively managed sanitation services can enhance resilience in the face of climate shocks. Emerging data from the UK Research and Innovation-funded Scaling up Off-grid Sanitation project shows that people experienced significantly fewer problems with their toilets when using CBS during shocks. Sealed containers and frequent collection reduce the risk of faecal contamination during floods, while diversified transport modes – such as hand carts – improve the chances of service continuity even when roads are inaccessible. CBS services can adjust their collection frequency in anticipation of seasonal rainfall, helping to mitigate cascading failures across urban systems. These qualities align closely with the GCF’s sanitation annex’s framing of climate-resilient sanitation as a combination of technical adaptation, active management and preparedness for systemic disruption.
Monetising the climate impact of CBS
Several years before the Climate Resilient Sanitation Coalition’s recent work to produce guidelines for sanitation with the Green Climate Fund (GCF), the CBS sector had already begun developing a pathway to unlock climate finance through carbon credits. With solid emissions data and GCF’s recognition of CBS as a climate resilient, actively managed sanitation solution, the sector is now better positioned to access climate funding.