This is a short summary of this 10-page research paper:
Carbajales-Dale, M., et al. 2018. Human powered electricity generation as a renewable resource. BioPhysical Economics and Resource Quality.
Before fossil fuels arrived, we depended on the energy from burning wood to make metals, bricks, ceramics, structures, and other objects, and the muscle power of men and animals to do work.
We discovered fire at least 250,000 years ago for cooking and warmth. Hunters and gatherers relied on muscle power when hunting, fishing, trapping, and gathering until approximately 12,000–10,000 B.C.. when agriculture began and transformed societies into sedentary villages. Work animals were domesticated to do the arduous work of plowing. Civilizations with excess muscle power were able to put it to other uses, such as constructing the 13,170 mile Great Wall of China, which probably required 2,000 years and millions of laborers. In Egypt the great pyramid in Khufu had 2.3 million blocks weighing from 2.5 to 80 tons, which probably took 25,000 laborers at least 20 years to build.
Ways to use energy more efficiently with mechanical devices such as pulley systems, windlasses, tread wheels, and gear wheels were invented that made muscle power go even further.
Now we’re almost entirely dependent on fossil fuels for our unprecedented high quality of life, yet we know fossils are finite and likely to decline.
So it is time to look again at what we can gain from muscle power, which will have to increasingly replace fossil fuels as they decline.
This has the added bonus of helping to cope with the obesity crisis. The authors estimate that an average American has 5 pounds of excess fat, which translates to 133,000 GJ of stored energy. Using human muscle as an energy source has the added benefit of reducing heart disease, strokes, and diabetes.
Gym members comprise a large potential muscle power workforce. Over 54 million people are members of a fitness center in the U.S. where their potential electricity generating exercise is wasted. Instead, members do the opposite and consume electricity, since equipment such as treadmills, ellipticals, stationary bikes, and rowers are electric. And air conditioning to keep members cool uses additional electricity.
This study looked at how much electric power could be generated by 40 members at a gym in South Carolina.
At best, 3-5% of the gym’s average daily electricity demand could be provided at a large cost. To convert the rowing machines to generate electricity would take 33 years to pay back, perhaps longer than a rowing machine will last.
Alice Friedemann www.energyskeptic.com author of “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts: Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity , XX2 report