The global water footprint of fossil fuels

2. marzo 2023, Ore 16:00 - Ore 17:00

Eawag Dübendorf, FC-C20 & Online

Prof. Avner Vengosh, Duke University, Division of Earth and Climate Sciences,
North Carolina, USA


As countries increasingly turn to renewable energy to reduce their carbon footprint, in 2019 renewables still comprised approximately 5% in comparison to fossil fuels that comprised 86% of global energy consumption. Given the predominance of fossil fuels, we re-evaluate the volumes of global water withdrawal and consumption for the different cycles of energy recovery and processing of fossil fuels. In doing so, we highlight the water quality component of the energy-water nexus. Based upon updated water intensity (water use per energy) and energy utilization data, the combined global water withdrawal for the different stages of fossil fuels extraction and production increased from 283 billion cubic meters (BCM) in early 1990’s to 642 BCM in 2019, while global water consumption increased from 33.9 BCM to 57.8 BCM. The revised estimate of global water utilization for energy far exceeds previous estimates, reflecting the rapid rise of global energy consumption, in particular the increasing intensity of unconventional oil and gas exploration. Parallel to water use, the global wastewater from all the major components of fossil fuels in 2019 was 43 BCM, in which coal and crude oil wastewaters consisted of 52% and 46%, respectively. Given the high levels of contaminants in the wastewaters, the release of even small volume of the wastewater through spills, leaks, or inadequate management to the environment severely affects the water quality of the receiving water and thus induces a large impaired-water intensity, which commonly is not evaluated in the energy-water nexus paradigm. Reevaluation of energy-water nexus and considering water quality degradation implies that the water intensity of fossil fuels is even larger than the estimated water footprint based on water quantity alone.
The environmental legacy of fossil fuels through abandoned oil and gas wells, leaching of contaminants from oil and wastewater spills sites, discharge of acid mine drainage, and disposal of coal combustion residuals will continue to impact the quality of water resources for decades to come, even in scenarios where fossil fuels utilization is declining. Given the much lower water intensity of solar energy, we quantified the water saving from the transition to rooftop PV solar across the U.S. We show that the rise in rooftop PV solar installation not only causes a reduction in greenhouse gas emissions but also a major reduction in the overall water footprint of the household electricity consumption.