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.
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.