Ecosystem maintenance energy and the need for a green EROI

A number of official energy forecasts—including those compatible with the aspirational 1.5 °C Paris Accord global temperature rise limit—see both global primary and net energy use continuing to rise, even out to 2100. Various technologies, including greatly increased use of renewable and nuclear energy, negative emission technologies such as direct air capture, and geoengineering are proposed as approaches for meeting the 1.5 °C target. In contrast, we argue that meeting this target and avoiding significant increases in extreme weather events will require marked reductions in future energy demand. We argue that the combined fossil fuel and renewable net green energy production will fall in the coming decades, after subtraction of various energy costs essential for ecosystems maintenance, including those needed to stabilise climate. At best, nuclear energy will only fractionally increase its global energy share, because of its high capital costs and political opposition arising from accident risks, waste disposal and proliferation concerns. Geoengineering will not solve fossil fuel depletion, and has serious known—and perhaps unknown—risks. We conclude that global net energy produced in an ecologically sustainable manner will start falling in a decade or so, and suggest the need to account for this at a policy level by introduction of a green EROI—EROIg.