Greenhouse gas emissions from wastewater treatment

Abstract

Quantifying greenhouse gas (GHG) emissions from wastewater treatment is fundamental for national inventories and climate change mitigation. This study aimed to estimate these emissions for domestic and industrial wastewater in Cuba during the period 1990–2022. The methodology followed the IPCC Level 1 Guidelines (2006), using default emission factors. Methane (CH₄) emissions were calculated from the organic load (expressed as BOD for domestic wastewater and COD for industrial wastewater) and the fractions of wastewater directed to different treatment or disposal systems (anaerobic lagoons, septic tanks, direct discharge into water bodies, among others). Indirect nitrous oxide (N₂O) emissions were estimated based on human protein consumption for effluents discharged into aquatic environments. The results showed that total emissions in 2022 were 1936.59 kt of CO₂-eq, representing a 1.31% increase compared to 1990. A decrease in industrial emissions was observed due to the sector's limited development, but an increase in domestic emissions and N₂O emissions was associated with greater sanitation coverage and wastewater disposal. It was concluded that CH₄ was the predominant GHG and that, while Cuban emissions are lower than global averages, it is necessary to promote more efficient, low-emission treatment systems to contribute to climate mitigation.