thank you for your reply and reference to the frontiers article..

A bit above my technical grade I’m afraid, though it did appear to be saying the oil production was ‘sustainable’ — -exactly how they define that was not made very clear — -at least not to me, but as i said, that isn’t my field at all.

I was wary of that because many articles of this kind use the word ‘sustainable, which I think requires a clearer definition

It also said ‘’addition of chopped beechwood’’ which raised a cautionary signal with me — -not outright condemnation at this stage, without understanding what it meant. I look at world oil usage and refer it to availability of trees and am left with the thought that tree shortage was what kicked off the industrial revolution in the first place.

The article also didnt seem to offer basic end product information on Energy input/vs energy ouput as some kind of conclusion.

At least that wasnt clear to me, if they did give that. I confess to being a bit bogged down by formulae