Would you show your work? I am curious and a little bit skeptical.
A gallon of gasoline has about 31,000 kcal. In the US, a typical sedan gets about 30 miles per gallon.
Walking a mile at 150lb bodyweight burns about 100 kcal. (This is non linear though: walking longer distances will burn less per mile on average)
If we assume linearity, to walk an extra 30 miles in a day you'd need 3000 more kcal of food. What is the energy cost of growing and transporting 3000 kcal of food? Does it exceed 31,000 kcal?
This was 10-15 years ago, so I don't have my notes lying around. However, I do remember that it was based on the calorific efficiency of bread bought at a supermarket. Other foods may vary - for instance if you grow potatoes in your back garden then it's probably going to be a lot more efficient.
I can well believe that there is a 10:1 ratio between energy in and mechanical energy out of a human.
However my point wasn't that cars and humans are about the same. That's probably only true in the "same order of magnitude" sense. My point was that humans are way less efficient at propelling a bicycle than an electric motor is.
A gallon of gasoline has about 31,000 kcal. In the US, a typical sedan gets about 30 miles per gallon.
Walking a mile at 150lb bodyweight burns about 100 kcal. (This is non linear though: walking longer distances will burn less per mile on average)
If we assume linearity, to walk an extra 30 miles in a day you'd need 3000 more kcal of food. What is the energy cost of growing and transporting 3000 kcal of food? Does it exceed 31,000 kcal?