alt Hacker NewsFun fact:
e-bikes are more climate friendly than human-powered bikes.
5 grams CO2 equivalent emissions per mile e-bike, 40 grams per mile for human eating exclusively bananas. Much, much worse for other dietary choices. Embodied carbon emissions in the bike itself are essentially equivalent.
The Carbon Footprint of Everything (2022)
The carbon in food is not captured or emitted in any coherent sense here. The crops are grown (capturing the carbon in the first place) for the purpose of feeding people -- in the same way that modern American forestry for paper is functionally carbon neutral (ignoring transport and processing) because the trees are in equilibrium. The counterfactual of not eating the food results in fewer crops and basically the same atmospheric carbon dioxide.
Edit: if you only mean food transportation carbon, it seems impossible bananas are literally optimal per calorie.