It is not that I had found a “fundamental flaw”. Those eco-fuel things simply don’t scale up to realistic levels, and the people who are behind it know that their small-scale experimental systems will never power the current level of aviation fuel demands.
Yes, human poo has some energy left. But it is way less than the same amount of fuel, I.e. you need several tons of poo to create a ton of fuel.
So you would have to collect the days worth of shit of way over half a million people to power this flight. And all this - again - with a lossless conversion. The reality is probably more like a 10% conversion productivity, meaning you would need ten times the poo.
I leave the question if this technology is actually sustainable to the reader.
And yes, my calculation of rapeseed oil based fuel was similarly funded in facts.