The efficiency of wood burning (or similar) at 10% or whatever percent, is hard to measure around other things needed to burn it.

I don't know where people get %'s from unless purely for the BTU but you have to balance how you burn it and convenience of method.

Just some points below that show my logic (can read arrowed lines only for the TLDR / less text also or can skip to the end for summary !!)

➡️ it's not really a scale of 0-100% when looking at things...

as 100% is not really possible when transferring or exchanging or kind of shouldn't be to account for convenience or other material involved (metals for stoves can't / shouldn't always be that pure (like gold) or maybe if they were it might justify such high quality

(but extremely heavy / unmanagable for example)

➡️ %'s are often comparing two things or a perspective in itself of what should be 100%, and comparisons are often not like for like or different in nature when looking at things.

➡️ So it's hard to measure in %'s
- maybe maximum of 70% is possible say (in theory) for wood and that might involve ways that give off long-term burn and not enough heat to heat a person or house.

Smoking food for example could be seen as using a % use of wood but not for heat (curing meat is a usage we could consider useful).

➡️ And then the materials around wood, such as stove, chimney, metals, convenience all come into it...

True stoves can be better but a small box, like mine are the Nordic type - and they know what they are doing (or should) since they have history of trees and living in heavier snow so their art has longer history than my bourgeois lifestyle in comparison :)

➡️ I mentioned it would be more efficiency to have a multi-level floor or longer chimney inside (maybe that would be efficient / more ehat) but I wouldn't want to manage that structurally or as hot hazard inside.

Ok that's it about that :)

➡️ Oh you mentioned the fuel and those things need in order to get heat at the end (diesel, tractor, metals etc) and I agree it's heavy investment and on-going extraction from Arab / East / Asia / Russia (wherever oil comes from) and I wouldn't choose this way (and we don't see what it takes to make machines and metal -

Maybe overall in #Tech and #Machines that's the "magic" as we don't see the extraction chain for a metal blob or tractor (they are being imported now or factories sold off so they will have their day like all machines!)...

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SUMMARY
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Right now 'it works' because

➡️ there is a balance of extraction / waste (which all can't continue too long has to switch fuels and materials eventually / trees fall and need time to grow)

➡️ we don't see the long line of material-chains and brutal steam-rollering of areas to get us all these toys

and motorized chains(aws) /

Hydraulics and other chemical, rubber plastic ETC ETC chains !!