Measurement Report: Methane and NOx emissions from natural gas cooking stoves, the case of Chile and Colombia

Abstract

Natural gas is widely used for household cooking, with methane (CH4), its main component, being a potent short-lived greenhouse gas (GHG). While a much cleaner alternative to solid fuels like wood and charcoal, natural gas combustion and leaks also contribute to GHG emissions and indoor air pollution. Yet, combustion and fugitive methane and air pollutant emissions from residential appliances, especially cookstoves, are poorly quantified in low- and middle-income countries. In this study, we measured CH4, carbon dioxide (CO2), carbon monoxide (CO), and nitrogen oxides (NOx) emissions from cookstoves in 35 homes in Santiago, Chile, and 23 in Bogotá, Colombia, two countries experiencing growth in natural gas use over the last decades. We assessed continuous (“stove-off”) methane leaks, ignition-related emissions, and combustion emissions, using a mass balance approach that accounts for air exchange rates and gas concentrations. Our real-world measurements provide rare data on household cookstove emissions and inform emission factors used in GHG inventories. The mean (median) methane emission rate during combustion was 410.2 (63.9) mg h−1 in Bogotá and 331.2 (30.7) mg h−1 in Santiago, respectively. The equivalent energy-based methane emission factors derived from the data for residential stoves in Bogotá averaged 80.8 (median = 16.2) and Santiago 41.2 (median = 3.66) kgCH4 TJ−1 are many times higher than the Tier 1 IPCC emission factors currently used in national inventories. Notably, our data suggests that continuous leaks and ignition-related emissions, which are excluded from current national and local emission inventories, contribute significantly to total methane emissions, with around 50 % of total methane emissions likely coming from continuous and episodic leaks, with the remaining half of emissions generated during combustion. For NOx, the emission factors from the measurements were 21.4 g GJ−1 (C.I., 19.1–23.8) and 15.8 g GJ−1 (C.I., 11.4–19.6) for Bogotá and Santiago, respectively. Overall, these findings suggest that current national inventories in Chile and Colombia underestimate methane emissions from household gas use, highlighting the need for more real-world measurements and research across Latin America. Our results have important implications for improving the accuracy of GHG inventories, understanding the role of household energy use in climate change, and guiding effective mitigation strategies.