energy
the capacity to do work; the amount of work that can be performed by a force
coal
around 30%
90% of coal production is used to make electricity, also make steel
humus
dark, more or less stable art of the organic matter of the soil so well decomposed the original source can’t be identified
petroluem
a naturally occurring complex liquid of hydro-carbons that after distillation yield a range of combustible fuels, petrochemicals, and lubricants- all derived from marine plankton