A document by Euan G. Nisbet. Click on the document to view its contents.

Emission of methane (CH and CO2. In situ mole fractions of CH4 and CO2 were measured in the subglacial air at a subglacial river outlet where emissions of CH4 and CO2 had been identified. Water samples were analysed for dissolved CH4 and CO2 concentrations. CH4 and CO2 in gas and water samples were analyzed for their isotopic composition of 13C and 2H. Close correlation between gaseous and dissolved CH4 and CO2, respectively, show degassing of CH4 and CO2 from the subglacial meltwater. The diurnal variability of in situ mole fractions of CH4 and CO2 in subglacial air was related to meltwater runoff. Maximum in situ mole fractions decreased after the peak of the melt season, but estimated net emissions increased because the size of the subglacial river outlet increased. The isotopic signature of CH4 in the subglacial air, estimated with a Keeling plot, indicated that subglacial CH4 likely originated from acetoclastic methanogenesis. Isotopic signatures of gaseous CO2 indicate that both microbial oxidation of CH4 in the subglacial system and remineralization of carbon in subglacial sediments contribute to subglacial CO2.

Natural gas is considered a bridging technology in the energy transition because it produces fewer carbon emissions than coal, for example. However, when leaks exist, methane is released into the atmosphere, leading to a dramatic increase in the carbon footprint of natural gas, as methane is a much stronger greenhouse gas than carbon dioxide. Therefore, we conducted a detailed study of methane emissions from gas-powered end-use appliances and then compared their climate impacts with those of electricity-powered appliances. We used the Munich Oktoberfest as a case study and then extended the study to 25 major natural gas consuming countries. This showed that electricity has been the more climate-friendly energy source at Oktoberfest since 2005, due to the extensive use of renewable electricity at the festival and the presence of methane emissions, particularly caused by incomplete combustion of natural gas appliances. Further, our global study shows that using electric appliances for cooking and heating would be more climate-friendly not only at Oktoberfest but also in several countries around the world, depending on the energy mix used and the leakage rate of natural gas. With this study, we demonstrate one way in which countries with a high renewable share in power generation, in particular, can reduce a significant amount of carbon emissions in the future.