The oldest energy systems are the human and animal muscles, which still perform all over the world a lot of mechanical energy, but were not mentioned in any energy statistics.
It is not only healthy to use ones own muscles but indispensable for the increasing number of people who like to use bicycles or the stairs instead of motorized vehicles and lifts, which are in the statistics of energy demand, but muscle power is not. Count the millions of work animals also, horses, elephants, buffalos, camels or sledge dogs, which are not in energy statistics, in spite of their excellence in sustainability, but motor vehicles and tractors with their polluting fuels are in the statistics, giving an incomplete, biased picture of unsustainable versus sustainable forms energy !
Assuming that the world population is performing only some 100 W for their mobility during two hours per day, this represents 600 GW power, or annually around 400 TWh mechanical energy, covering about 0,4 % of the world’s total energy needs – clean, sustainable and eternally available without energy cost, if the already existing food chain is not counted, and keeping people much fitter, slimmer and healthier compared with noisy, polluting rides in cars or on motor bikes.
Animal power must be added to this human energy supply, thus replacing polluting tractors. Statistics and forecasts for all these sustainable forms of energy versus their fuel consuming, polluting competitors are overdue and will show that much more than 10 % of total energy needs can be covered by the combination of human and animal muscle energy !
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The ISEO working groups will add more information.