Relevant methane emission to the atmosphere from a geological gas manifestation

Abstract

Quantifying natural geological sources of methane (CH4) allows to improve the assessment of anthropogenic emissions to the atmosphere from fossil fuel industries. The global CH4 flux of geological gas is, however, an object of debate. Recent fossil (14C-free) CH4 measurements in preindustrial-era ice cores suggest very low global geological emissions (~ 1.6 Tg year−1), implying a larger fossil fuel industry source. This is however in contrast with previously published bottom-up and top-down geo-emission estimates (~ 45 Tg year−1) and even regional-scale emissions of ~ 1–2 Tg year−1. Here we report on significant geological CH4 emissions from the Lusi hydrothermal system (Indonesia), measured by ground-based and satellite (TROPOMI) techniques. Both techniques indicate a total CH4 output of ~ 0.1 Tg year−1, equivalent to the minimum value of global geo-emission derived by ice core 14CH4 estimates. Our results are consistent with the order of magnitude of the emission factors of large seeps used in global bottom-up estimates, and endorse a substantial contribution from natural Earth’s CH4 degassing. The preindustrial ice core assessments of geological CH4 release may be underestimated and require further study. Satellite measurements can help to test geological CH4 emission factors and explain the gap between the contrasting estimates.

The mud volcanoes at Santa Barbara and Aragona (Sicily, Italy): a contribution to risk assessment

“…At the same time, an update of the actual hazard maps for the two areas must be implemented. However, a better comprehension of the sedimentary volcanism paroxysmal processes is needed, with particular reference to their hazard assessment; it is certainly important in a next future to build a paroxysmal event catalogue in order to be able to apply advanced assessment approaches such as the one proposed by Mellors et al (2007).…”

“…According to a detailed study performed by Mellors et al (2007), for the mud volcanoes in Azerbaijan, the temporal correlation between earthquakes and eruptions is most pronounced for nearby earthquakes (within 100 km) and with intensities of Mercalli 6 or greater. According to Bonini (2009), mud volcanoes of the Pede-Apennine margin in Italy are intimately connected with rising fluids trapped in the core of anticlines associated with the seismogenic Pede-Apennine thrusts.…”

“…For this reason, several multidisciplinary monitoring approaches have been proposed in different MV in the world. More recently, Mazzini et al (2021) have estimated the total CH 4 emissions from Lusi using both ground-based and for, the first time, satellite (TROPOMI) measurements; CO 2 emission is additionally measured by ground-based techniques. In May and October 2011, the activity was documented with highresolution time-lapse photography, open-path Fourier transform infrared (FTIR) imagery, and thermal infrared imagery (Vanderkluysen et al, 2014).…”

Long-Term Atmospheric Emissions for the Coal Oil Point Natural Marine Hydrocarbon Seep Field, Offshore California

“…This estimate, if accurate, suggest the COP seep field contributes an astounding 1% of global seep emissions (submarine and aerial) and is difficult to reconcile with the COP seep field and other top seepage estimates. For example, CH4 atmospheric emissions for the Lusi hydrothermal system of 0.1 Tg yr -1 (Mazzini et al, 2021), a hotspot in the Laptev Sea of 0.9 Tg yr -1 into shallow seas (Shakhova, Semiletov, Leifer, et al, 2010), and for the East Siberian Arctic Sea using eddy covariance of 3.0 Tg yr -1 (Thornton et al, 2020). Thus, COP seep field emissions either play a significant role in global seep emissions or indicate that geo-gas emissions are less tightly constrained.…”

Influence of permafrost thaw on an extreme geologic methane seep

“…Fossil CH 4 (i.e., CH 4 with no modern carbon [ 14 C‐free]) accounts for ~5 Tg CH 4 yr −1 of the total 38 ± 23 Tg CH 4 yr −1 atmospheric CH 4 emission 14 . The highest known single CH 4 seep—Tramutola in Italy—emits ~0.0024 Tg CH 4 yr −1 , 12 and the highest emitting seep field—a sediment‐hosted hydrothermal system called Lusi in Indonesia, 15,16 emits approximately 0.1 Tg CH 4 yr −1 17 . Fossil CH 4 originates from thermal and microbial decomposition of organic matter in sedimentary basins 14,18,19 .…”