Not by a long shot, but the answer is still interesting.
In the carbon footprint spreadsheet I developed for the 1.5 degree lifestyle, I did not include anything for cycling or walking, considering them zero carbon activities. Then I saw a tweet fly by:
Did I just hear a public commenter at the SF supes meeting suggest that riding a bicycle equates to 30 miles per gallon fuel consumption because of the fossil fuel required to produce a person's food?— Dominic Fracassa (@DominicFracassa) February 4, 2020
I laughed at first, especially since we say that Bikes aren't just transportation, they are climate action. And, as I explain later, there is biogenic carbon and fossil carbon, and they are two different things. But then remembered the case of Alan Wayne Scott vs Canada covered in TreeHugger here. He went to court in Canada to demand that he get to expense his food, which was his fuel as a bike courier. The judge agreed with him, writing:
Back in 1997, the judge noted the environmental benefits. "Arguably, it also recognizes and encourages [rather than discourages as a prohibition on this expense would] new environmentally responsible ways of producing income." Based on the estimated number of calories that bike couriers burned, the government allows C$ 17.50 per day for food, so we have legal recognition that food is a fuel. American courts have rejected all of this, saying, "Expenditures for food, the 'fuel' for all human activities, whether or not business related, are considered inherently personal in nature" and, of course, showing once again how the system is biased toward four wheels and against two.
Because the courier who drives the automobile is allowed to deduct his or her fuel, the foot and transit courier should be able to deduct the fuel his body needs. However, because we all require food and water to live, he can only deduct the extra food and water he must consume above and beyond the average person's intake in order to perform his job.
So how efficient is food as a fuel, compared to gasoline? A lot of people have looked at this but the most comprehensive analysis appears to be the one published in Bicycle Universe by Michael Bluejay, which has extensive sourcing. It turns out that much depends on what you eat, since diet including meat takes so much more energy to make than a vegetarian or vegan diet. But even in the worst case scenario, a meat-eating cyclist is getting the equivalent of 75 MPG, while the vegan gets the equivalent of 145 MPG.
No doubt Tesla drivers will be all excited about this, since a Model 3 gets the miles per gallon equivalent of 130 MPGe, saying, "We're better than a bicycle!" But this doesn't take into account the Upfront Carbon Emissions, commonly called Embodied Carbon, from the making of the vehicle, which are about 15 percent higher than a comparable ICE powered car because of the batteries, and are probably around 20 tonnes of CO2.
A lot of people will complain about this article, as they did about the original carbon calculation, suggesting that it is actually encouraging driving, especially if you own an electric car. There are obviously many other environmental costs to driving, and walking or biking is good for you.
Most importantly the IPCC and the International Energy Agency consider the carbon people emit to be biogenic,"the emissions related to the natural carbon cycle, as well as those resulting from the combustion, harvest, digestion, fermentation, decomposition or processing of biologically based materials." It is essentially coming from our conversion of plants that recently absorbed the carbon so it doesn't change the amount of carbon in the atmosphere, while cars generate fossil carbon that raises the levels of CO2.
So you really can't compare vehicle carbon emissions to people carbon emissions at all. But it is an interesting exercise that does prove that the public commentor was off by a mile.