Why Technology Could Slow the Clean Energy Transition Energy density—defined as the “amount of energy stored in a given system, substance, region of space per unit volume”—is the main reason why fossil fuels will not be replaced in the near future by renewables. Approximately 84 percent of global electricity derives from oil, natural gas, and coal. The International Energy Agency (IEA) released a sobering report on the mining and infrastructure requirements needed for decarbonization and/or net-zero to take shape. Mining to move away from hydrocarbons will require 4,200 percent more lithium, 2,500 percent more graphite, 1,900 percent more nickel, and at least 700 percent more rare earth metals and minerals.