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Comment by ReptileMan | Hacker News Reader

When I was cycling I was joking that the bike is not much greener than the car, because it burns 4 ribeyes/100km or 17 miles/ribeye.

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I read somewhere that if you’re not at least mostly vegan, e-bikes actually have lower lifecycle carbon emissions than bikes because you end up burning fewer calories and eating less (assuming you don’t substitute in more exercise).

So. Lithium battery powered humans would emit less carbon than regular humans?

They would since we could charge them using PV instead of wasteful bovines.

That makes a lot of sense. Intuitively (I haven't tried to run numbers on this), the big efficiency problem with a car – gas or EV – is not that it's using "unnatural" forms of power, it's that you're hauling a 3000 pound vehicle around with your 160 pound human. It's easy to believe that photovoltaic power -> modern battery -> electric motor is far more efficient than photosynthesis -> animal digestion -> human digestion -> human muscle. I wouldn't be shocked if that held up even on a vegan diet, though the difference would be a rounding error compared to the emissions from other aspects of our lives.

It’s plausible especially if you use PVs to charge. But what about the costs in producing and disposing of the batteries?

Yes, sedentary lifestyles require less overall energy input vs. active ones

If we consider the average diet bikes are still around 1/3 the emissions of cars per mile. Obviously if you eat only meat that gets worse but I doubt it’s possible to exceed car emissions this way.

This has some data: https://keith.seas.harvard.edu/blog/climate-impacts-biking-v...

According to Table 1, a meat eating biker emits more CO2, than a double-occupancy Prius.

I suspect an EV would completely tip the table in favor of driving.

Side note - comments like this are why I come to HN. Thank you.

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