I jumped down the rabbit hole because I like the idea that insects could harvest carbon from the atmosphere... especially since carbon is required for amino acids. But it looks like that's not the case (great hypothesis though!)

I did find a reliable source that puts insect food to protein conversion at 2:1, which is still impressive compared to a cow at around 8:1.

From https://www.fao.org/edible-insects/en?hl=en-US#%3A%7E%3Atext=%232%2Ckg+of+body+weight+gain.

Insects have a high feed conversion efficiency because they are cold-blooded. On average, insects can convert 2 kg of feed into 1 kg of insect mass, whereas cattle require 8 kg of feed to produce 1 kg of body weight gain.