Gas flaring: a review focused on its analysis from space

This review represents the current state-of-the-art in analyzing gas flaring (GF) from space. GF is a prominent source of air pollution, with significant global and local impacts. Its emissions contribute to climate change and air pollution, and its practice is a waste of a valuable energy source. A key barrier in evaluating the status of this phenomenon is the incomplete and inconsistent availability (or lack) of public information. In the last few decades, satellite-based methodologies have shown considerable potential for bridging this gap. They have been employed for 1) detecting flaring sites, globally or regionally; 2) characterizing them; 3) computing the volumes of gas they flare; and 4) assessing air pollutant and greenhouse gases emissions. Long-term archives of multispectral satellite imagery, dating to the 1990s, also provide the ability to follow the spatiotemporal evolution of GF. This work, which collects literature papers through July 2019 starting with background information on satellites' capabilities to observe gas flares, describes satellite-based methods used to derive independent, reliable data on GF. This article highlights the progress made by the scientific research in each of the aforementioned scientific fields, with a final focus on the major open challenges and potential future improvements.