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You're right that it doesn't make economic sense. It also doesn't make scientific sense. First of all, human power releases tons of carbon dioxide just like b

• scarmig 9y ago
  The carbon that humans exhale is already part of the carbon cycle. So equilibrium CO2 concentrations don't change, so it's not an issue pollution wise. (This is assuming you didn't use a bunch of fossil fuels to create and transport food in the first place, and you're instead using human/animal power to do that.)
  • kristjansson 9y ago
    However, using humans as power source would increase the amount of food consumed, and co2 exhaled, so this analysis would need to take at least that incremental co2 into account.
    • deleted 9y ago
      [deleted]
    • ouid 9y ago
      Whether a human eats the plant or it decomposes naturally, the same amount of carbon dioxide is released.
      • erroneousfunk 9y ago
        That would be fine if humans simply walked around consuming plants that would have otherwise decomposed and there were no other resources associated with food production. Unfortunately, agriculture is a major driver of deforestation (and forests are excellent at actually sequestering carbon in the ground). It also requires trucks, boats, and planes to haul supplies to farms, work the land, move water around, and transport the produce to stores. You have processing and packaging that rely on fossil resources (paper, plastic, metal cans...) That doesn't even touch on the impact of meat production, which is several times worse for the environment. Food consumption is absolutely not carbon neutral. You're far better off taking public transportation to work (if available) than walking or riding a bike, if you care about the environment.
    • photojosh 9y ago
      Challenge accepted. On a bike I can do around 220W for an hour, and 160W for an indefinite period (have done up to 12 hours before). Biking is known to be 20-25% efficient from calories burned to power at the wheel, so that's ~700 kCal/h for an hour at 160W. My idle consumption is ~1600 kCal/day, or roughly 70 kCal per hour, so riding on the bike uses 10x as much; therefore I'm going to be producing 10x as much CO2 (obviously). It takes ~140 L of oxygen to burn those ~700 calories, resulting in ~110 L of CO2. So if I do a 4 hour ride at 160W to produce maybe 600Wh of energy after conversion inefficiencies, that's 2800 kCal just for the ride and 4400 kCal for the whole day, around 2.75x my idle consumption. Disclaimer: I've done this quickly. Feel free to point out any errors. > Whether a human eats the plant or it decomposes naturally, the same amount of carbon dioxide is released. Yes, but we produce agricultural crops to meet demand. If as per the calculations above, every human suddenly started consuming 2.5x as much food, we'd have to grow more. And yes, this is part of the carbon cycle. The problem is that we use fossil fuels and release CO2 above and beyond what's part of the normal cycle.
• Bartweiss 9y ago
  > First of all, human power releases tons of carbon dioxide just like burning fossil fuels does I was disappointed that for all its calculations, the article completely avoided the question of "How green is human power?" Instead, it just repeated "could become one of the cleanest energy forms available". But they had to, of course - answering that would have destroyed the entire idea. Fueling humans burns a huge amount of carbon, and neither the food > muscle conversion or the muscle > electricity conversion is even passably efficient.