Non-volcanic CO2 Earth degassing: Case of Mefite d'Ansanto (southern Apennines), Italy

Abstract

Mefite d’Ansanto, southern Apennines, Italy is the largest natural emission of low temperature CO2 rich gases, from non‐volcanic environment, ever measured in the Earth. The emission is fed by a buried reservoir, made up of permeable limestones and covered by clayey sediments. We estimated a total gas flux of about 2000 tons per day. Under low wind conditions, the gas flows along a narrow natural channel producing a persistent gas river which has killed over a period of time people and animals. The application of a physical numerical model allowed us to define the zones which potentially can be affected by dangerous CO2 concentration at breathing height for humans. The geometry of the Mefite gas reservoir is similar to those designed for sequestering CO2 in geological storage projects where huge amounts of CO2 should be injected in order to reduce atmospheric CO2 concentration. The approach which we have used at Mefite to define hazardous zones for the human health can be applied also in case of large CO2 leakages from storage sites, a phenomena which, even if improbable, can not be ruled out.