Your claimed calculation is very vague, I have to say I don't believe for a second you actually did that and it's laughable you're claiming you did
When someone tells me that they've noticed a fundamental flaw that all the leading minds in the field have not it does not lead me to think that the field itself is flawed rather the person I'm speaking to's understanding of it.
Of course we understand that it's not all going to come from one source but where there are waste products like stalks and leaves left over from food production, poo, algae, and etc it makes sense to work towards using all of those so we can transition away from the extracting oil and gas.
This is a fantastic idea, here in the UK we've just been dumping raw sewage in the rivers and poisoning the coast because it'd cut into water companies record profits to treat it (also Brexit chemical shortages or something)- if we can turn the poop into something useful that can sell then the won't let a drop off that precious filth go to waste.