Lusi is the nickname of a spectacular gas manifestation that developed in 2006 in the Java Island, Indonesia. Since then, Lusi is relentlessly bursting, water, oil, gas and mud, with flow rate peaks of 180,000 m3/day (equivalent to around 72 Olympic swimming pools) and the vapour plumes reach several tens of meters in height.
Years of monitoring and analyses have shown that this geological phenomenon is fueled by high fluid pressures in sedimentary rocks and high temperatures resulting from the interaction with the neighbouring magmatic volcano. Lusi is therefore considered the surface manifestation of a hybrid sedimentary/hydrothermal system. The gas is rich in carbon dioxide (CO2) and methane (CH4), which are expelled at a central crater and across thousands of vents covering an area of 7.5 km2. Until now, the amount of gas released from this site remained unknown.
The research team, coordinated by the Centre for Earth Evolution and Dynamics (University of Oslo) with the collaboration of the Istituto Nazionale di Geofisica e Vulcanologia of Rome, the Netherlands Institute for Space Research of Utrecht, and the Indonesian Agency Pusat Pengendalian Lumpur Sidoarjo combined ground-based and satellite (TROPOMI) measurement techniques to quantify the amount of gas released to the atmosphere by Lusi. Both techniques indicated a total methane output of about 100,000 tonnes per year. Importantly, this is the highest methane emission ever recorded experimentally for a single natural gas manifestation.
The results, published this week in Scientific Reports, suggests that recent estimates of global geological methane emissions, based on radiocarbon in pre-industrial era ice cores (ranging from 100,000 to 5,400,000 tonnes of CH4 per year), may be underestimated. In other words, the amount of methane released by the volcanic system of Lusi alone, already matches the minimum assessment of the ice-core based studies for the entire planet. The Lusi value is thought to be proportionally consistent with the level of methane flux (the so-called “emission factor”) typically released by other, similar terrestrial natural gas manifestations (e.g. other mud volcanoes, large methane seep systems). If these sites are combined globally, the bottom-up global estimates lead to a total output in the order of 40-50 million tonnes per year.
Knowing the true amounts and fluxes of methane release from natural geological sources is important to better assess the anthropogenic gas emissions, such as from the oil industry, and the atmospheric methane budget in general. This new study also suggests that satellite-derived gas emission measurements can be a key tool to support ground-based studies and improve global geo-methane budget estimates.
Citation: Mazzini, A., Sciarra, A., Etiope. E., Sadavarte, P., Houweling, S., Pandey, S., Husein, A. 2021. Relevant methane emission to the atmosphere from a geological gas manifestation, Scientific Reports, v. 11, no. 1, p. 4138. www.nature.com/articles/s41598-021-83369-9
Contact: Adriano Mazzini (CEED, Uni.Oslo) adriano.mazzini@geo.uio.no
The work was funded by the by the European Research Council under the European Union's Seventh Framework Programme Grant agreement number 308126 (LUSI LAB project, PI A. Mazzini) and Research Council of Norway through its Centres of Excellence funding scheme, Project Number 223272 (CEED)
