Seite - 20 - in Water, Energy, and Environment - A Primer

century.It is important tonotethat‘peakingout’still leaveslotsof liquidhydrocarbonstobeextracted.TheUScurrentlyranksasthe world’s top oil producer, followed by Saudi Arabia, Russia, Canada andChina (seeFigure 2.5). Demand for liquid fuels today is driven largely by their use in transportation and is growing as automobile, truck, and aviation use grows inmany countries. Eventually, this demand will begin to decrease as more fuel-efficient cars, alternative fuels, and electric drive propulsion systems enter the transportationmarket. According to the IEA, between 1971 and 2016 oil’s share of total primary energy supply (TPES) fell from44%to32%(16). This is just one of several changes that have occurred in the global energy picture over this period. TPES increased by a factor of 2.3 (from 6101Mtoe to 13,647Mtoe); coal increased its share to 29% in 2011, when it peaked, and has been declining since (27% in 2016); nuclear’s share rose from 1% to 5%; and the natural gas share grew from 16% to 22% (see Figure 2.6). Figure2.5Worldoil productionby region (Source: InternationalEnergy Agency). Water,Energy, andEnvironment–APrimer20