Crap into coal ??

[BDG]

It is not really a new thing, I can remember someone doing an A-level biology practical and making some back when I was younger at school.

A lot of energy is used to get up to temperature and while I would say you would not have to do it at such pressures mentioned (20 bar I think it was) the higher the pressure, the less heat you need as a rule of thumb. It would be a pretty special bit of kit that would handle 20 bar that you could fit a lot of crap into and remove the product from, move around, lift onto a fire etcetera.

Worth doing on an industrial scale, but if it was me post SHTF, my sludge would be going on willow beds.