Energy production is water-intensive and the vast supplies that are needed to run every type of power plant natural gas, coal, nuclear and renewables is not well understood.
Unconventional oil production (whether from shale or oil sands) is an energy-intensive process, and emits more CO2 than conventional extractive methods do.
The production of modern wind turbines, solar panels and nuclear power plants are extremely energy-intensive enterprises, and are by and large powered by the burning of fossil fuels.