I think you may be thinking of the question, "how much greenhouse gas does it take to move a human X miles if they are self-powered versus using an ICE?"
> our estimates suggest that the net emissions associated with the ‘fuel’ required for driving, walking, and cycling may be comparable in some settings
With the caveat that they're looking at *per-mile* emissions, and nobody in the developed world is walking 60 miles to and from work every day.
However there's an important clarification to your recollection.
- You're correct that eating meat (and dairy) is very carbon-intensive.
- You're not correct that agricultural transportation is significant. It doesn't even make it into the paper above, as far as I could find. Agricultural transportation, even things like flying blueberries to California from Chile, is negligible compared to the carbon cost of food.
For example this study https://www.nature.com/articles/s41598-020-66170-y.
> our estimates suggest that the net emissions associated with the ‘fuel’ required for driving, walking, and cycling may be comparable in some settings
With the caveat that they're looking at *per-mile* emissions, and nobody in the developed world is walking 60 miles to and from work every day.
However there's an important clarification to your recollection.
- You're correct that eating meat (and dairy) is very carbon-intensive.
- You're not correct that agricultural transportation is significant. It doesn't even make it into the paper above, as far as I could find. Agricultural transportation, even things like flying blueberries to California from Chile, is negligible compared to the carbon cost of food.
You can see that in the following graph. Red is transport. You have to look closely even to see it. https://ourworldindata.org/food-choice-vs-eating-local