Infiltrated Pits: Using Regional Groundwater Data to Estimate Methane Emissions from Pit Latrines

Area of Science:

• Environmental Science
• Climate Science
• Sanitation Engineering

Background:

• On-site sanitation systems (OSS), particularly pit latrines, are significant sources of methane (CH4) emissions.
• Methane emissions increase with pit latrine inundation, which is driven by anaerobic conditions exacerbated by high groundwater levels.

Purpose of the Study:

• To develop and present a model for estimating methane (CH4) emissions from pit latrines.
• To incorporate seasonal groundwater fluctuations and pit latrine inundation into CH4 emission estimations.
• To address data scarcity in low- and middle-income countries (LMICs) for accurate emission modeling.

Main Methods:

• Utilized inverse distance weighted (IDW) interpolation to estimate regional groundwater table depth.
• Integrated groundwater data with average pit latrine depth to identify areas of inundation.
• Incorporated open-source data on population, urban/rural distribution, and sanitation facilities.
• Applied Intergovernmental Panel on Climate Change (IPCC) methodologies for CH4 emission calculations.

Main Results:

• Developed a model to estimate CH4 emissions based on fluctuating groundwater levels and pit latrine inundation.
• Demonstrated the model's application using a case study from Senegal, estimating ~1.69 kt CH4 emissions for January.
• Highlighted the potential of satellite remote sensing for regions lacking historical groundwater data.

Conclusions:

• The developed model provides a method to estimate CH4 emissions from OSS by considering groundwater dynamics.
• Improved understanding of pit latrine inundation timing can inform better management strategies and reduce CH4 production.
• The study emphasizes the need for localized data and innovative modeling approaches for climate change mitigation efforts in sanitation.