Influence of methane emissions on the GHG emissions of fossil fuels

Abstract

Our study examines the effects of methane emissions on the greenhouse gas (GHG) emissions of crude oil and natural gas between 2015 and 2040. Our scenario calculations, derived from global methane budgets and shale analyses, provided a range of 22–59 million tons of global methane emissions from the oil sector in 2015. By 2040, the methane emissions of crude oil will increase by between 18% and 59%. For the global warming potential over 100 years (GWP100), our analysis shows venting, flaring, and fugitive (VFF) emissions of global diesel and gasoline combined of between 8.78 and 14.80 g CO2eq MJ−1 in 2015 and 8.88 to 16.34 g CO2eq MJ−1 by 2040. Our minimum average values for VVF emissions of fossil fuels are thus twice as high as those used in the calculations for the fossil reference value used in the Fuel Quality Directive of the European Union (EU‐FQD). The VVF emissions from diesel and gasoline produced from shale oil will reach up to 26.84 g CO2eq MJ−1 and from shale natural gas liquids (NGL) up to 31.84 g CO2eq MJ−1. Our maximum marginal values for the VVF emissions of fossil fuels are thus up to nine times higher than the VVF value for the EU‐FQD. Based on our calculations, the EU‐FQD reference value for conventional fossil diesel will increase from 95 g MJ−1 to between 99.16 and 105.06 g MJ−1 for the GWP100 and between 109.80 and 124.70 g MJ−1 for the global warming potential over 20 years (GWP20). Our results thus show that the previous reference values for fossil fuels are clearly too low because their assumptions for methane emissions are far too low. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd

A Structured Approach for the Mitigation of Natural Methane Emissions—Lessons Learned from Anthropogenic Emissions

“…Here, highly sensitive sensors coupled with up-to-date algorithms, models and datasets are used to generate bottom-up estimates for anthropogenic as well as natural methane emissions [29,82]. However, current global bottom-up emission estimates rely heavily on assumptions and generalizations to be able to model methane emissions for every source, since detailed measurements and precise emission allocation on a global scale can only be performed with some degree of uncertainty [16,38]. This uncertainty can be seen in current global methane budgets [3,12,13,38], (9) where uncertainties of natural methane emissions typically range from 25% to 50%.…”

“…In natural methane mitigation from air, Problems (1), (2), (12) and (16) come to mind, i.e., in particular the low concentrations and large areas in combination with the physical properties of methane. The example of solid waste landfills shows that mitigation of methane emissions over somewhat larger areas is possible [109].…”

“…Consequently, a lot of research is dedicated on pre-generation methane mitigation, specifically for anthropogenic non-point sources, where mitigation after methane production proves particularly difficult. Pre-generation mitigation is therefore a candidate to solve Problems (1)-(3), (15) and (16), but, due to Problems (10) and (18), for natural emissions, pre-generation is challenging. Existing anthropogenic examples are fish to increase bioturbation in rice paddies [140], to feed cattle a specific diet [141] and to introduce air into landfills to omit anaerobic methane generation by converting organic materials aerobically [142].…”

“…In-situ mitigation is also not applicable in most cases due to the large areas and ecological side-effects. Consequently, post-emission mitigation is the only broadly applicable possibility to approach a generalized natural methane emission reduction strategy aiming to solve or avoid Problems (1)-(4), (10), (16), (18). Indeed, if there are for certain applications favorable pre-or in-situ-mitigation options or will be developed, these should be used or tested.…”

“…Anthropogenic and natural emissions are increasingly studied, measured and reported, but large uncertainties persist [11][12][13][14][15]. Recent research point to largely underestimated methane emissions from oil and gas production questioning also the lower GHG emission factor of natural gas [16]. Furthermore, models predict a strong increase of natural emissions such as from permafrost [17][18][19].…”