Methane emissions from onsite sanitation containment units in Indonesia

an empirical study at the household level

Abstract

Sanitation contributes to greenhouse gas (GHG) emissions, but the lack of empirical data adds high uncertainty to current estimates. The Intergovernmental Panel on Climate Change (IPCC) provides expert advice on standard methodologies for estimating emissions. In the wastewater sector, limited empirical emission factors mean that national inventories often fail to reflect the diversity in onsite sanitation systems linked to design, operation and maintenance of household containment units. For that reason, we measured methane emissions from 27 containment units across five Indonesian cities during both dry and wet seasons (two to four times per season over 12- or 24‑hour periods). Sealed containment units had a median emission rate of 2.22 g CH₄ cap^-1 day^-1, rising to 2.43 g CH₄ cap^-1 day^-1 for lined and 17.27 g CH₄ cap^-1 day^-1 for open (unlined) units. Our findings also show that construction features such as the presence of outlets and aeration affect methane emission rates, along with other site‑specific factors (sludge age, loading rate, etc.). These support the need for expanded empirical datasets in low‑ and middle‑income countries where sanitation technologies are predominant and highly heterogeneous.  This is essential for improving the accuracy and representativeness of national GHG inventories for the sanitation sector.