By members of the Climate Resilient Sanitation Coalition and the Water Initiative for Net Zero

On 18 March 2024, policymakers, industry leaders and scientists will gather in Geneva, Switzerland, for the Global Methane Forum. The purpose is to take stock of progress on methane mitigation strategies and to mobilize ambitious action, in line with the Global Methane Pledge.

Much has happened since the pledge was launched in 2021. At that time, the international community was just starting to understand that the Paris Agreement’s goal to keep global warming below 1.5°C can only be met through fast reductions in methane emissions. Since then, 155 countries have signed the Global Methane Pledge, which aims to cut global methane emissions by at least 30% by 2030, relative to 2020 levels. We have also achieved a better understanding of methane emissions, thanks to more research and better data from new satellite technologies.

At the same time, it is striking how many countries lack either concrete plans for how to achieve the necessary cuts in methane emissions or sufficient data on current emissions. This may not be strange given how fast our understanding of methane is growing, but it is worrying, nevertheless.

We are especially concerned that the issue of methane emissions from sanitation systems is not on the radar of the climate community and is only starting to get the attention of the sanitation sector. Ahead of the Global Methane Forum, we want to draw attention to key barriers for action, and the measures we should take to address them.

Sanitation emissions are greater than assumed 

Anthropogenic methane emissions are commonly characterized as originating primarily from three sectors: fossil fuel production; agriculture; and waste. Sanitation and wastewater management systems fall within the “waste” sector. Methane emissions from wastewater management (primarily those systems using water-borne sewers), are estimated to account for 7% of global methane emissions, and the rest of sanitation for another 5%, according to recent research. However, existing greenhouse gas (GHG) emission inventories likely underestimate methane emissions from the sanitation sector due to limited empirical data on the scale of emissions from sanitation systems that do not utilize sewers (i.e., pit latrines, septic tanks, etc.), as well as on other aspects of sanitation systems, including the emptying and transport services and disposal of sewage sludge.

Even for well-researched aspects of the sanitation system like wastewater treatment plants, studies indicate that methane emissions could be as much as double the estimates made using Tier 1 and Tier 2 Intergovernmental Panel on Climate Change (IPCC) guidelines for emissions inventories. Moreover, none of the current methodologies take into account the full sanitation system – from the point of production to end-point reuse or disposal of waste products.

Sanitation systems that do not utilize sewers are of particular concern since the problem could grow fast if we don’t take action. This is because they are predominant in the low-income countries (LICs) and middle-income countries (MICs) where we will see most of the population growth and where the 1.5 billion people without access to basic sanitation services typically live. For instance, in many cities in sub-Saharan Africa, well over 70% of urban residents are unable or unwilling to connect to sewers.

Efforts to achieve SDG 6.2 (universal safely managed sanitation coverage) could result in a 60% increase in methane emissions from sanitation systems in sub-Saharan Africa and maybe even more in India. This calls for investments in climate-smart sanitation, especially since this would also make vulnerable populations more resilient to the impacts of climate change while using technologies that also don’t lead to massive methane emissions.

Unlike other sectors like energy production or aviation, emissions from sanitation cannot be solved through substitution. Excreta will always be produced. We need to find and promote ways to manage it which optimize both public health, environmental, and climate objectives.

Sanitation is missing in NDCs and methane action plans

Despite the significant contribution of sanitation systems to methane emissions, the sanitation sector has to date largely been a blind spot in methane reduction policies and plans. The same goes for Nationally Determined Contributions (NDCs) under the Paris Agreement on climate change. A recent analysis of 168 NDCs received as of December 2022 revealed a total of 476 actions focused on methane. Methane mitigation from sanitation systems was only covered in 59 NDCs (35% of countries) and in most of these, the focus is on capturing biogas from centralized wastewater treatment plants, ignoring the rest of the sanitation system such as pit latrines and septic tanks.

Actions for methane mitigation in the sanitation sector

So, why don’t we see greater interest in mitigating methane emissions from sanitation services? It is not due to a lack of solutions – on the contrary.

For example, emissions can be reduced immediately and significantly by adding methane capture to existing and planned wastewater and fecal sludge treatment plants, with the collected biogas used as an energy source. The use of treated sludge in agriculture can also have net positive impacts on carbon retention in soils and can substitute out a fraction of chemical soil conditioners and fertilizers. Active management of pits and tanks through regular desludging, and the deployment of aerobic treatment technologies (especially those that do not require electricity inputs) can also have positive impacts.

Three barriers for action prevent us from scaling up these solutions: (1) the range of methane emissions from sanitation systems and the scope for their reduction are under-estimated or not evaluated; (2) sanitation-related emissions are hidden within the wider waste sector and may be ignored or deprioritized; and (3) the available solutions are not fully exploited and may be underfunded by implementing parties.

Ahead of the Global Methane Forum, we call on three constituents to help remove these barriers:

• Scientists and researchers: There is a need for more empirical data from sanitation systems in more contexts and for more types of technologies, to better understand which approaches are most promising and provide the most cost-effective means for methane abatement. Empirical data and, subsequently, improved emission models can ensure that national GHG inventories accurately account for methane emissions from sanitation systems and hence can guide effective mitigation strategies.
• Policymakers: It is imperative for planners and policymakers in governments to align sanitation policies and strategies with climate commitments and vice versa. This involves the inclusion of climate-smart sanitation strategies in NDCs and National Adaptation Plans (NAPs), as well as in Methane Action Plans and National Methane Roadmaps.
• Funders and investors: Dedicated allocation of funds for research into emissions assessment, the development of innovative abatement technologies, and the scaling of existing mitigation solutions within the sanitation sector as well as their operation and maintenance, are crucial. Finance can also be leveraged to incentivize concerted action in the sanitation sector through the incorporation of specific criteria that evaluate the potential of projects to reduce methane emissions.

Methane emissions from the sanitation sector are not hard-to-abate, but historically they have been easy to ignore. Now we have the solutions at hand and know they make a real impact. We cannot afford to wait to take full advantage of this opportunity.