Coal mixed in with wood?

I have a ton of coal. Have you ever tried adding a little coal in with the wood? Do you think it would work?

Hi David,

coal as fuel has been discussed many times here. Conduct a search for “coal” in the search box at the top left on any of the DOW pages and you’ll find at least half a dozen results.
From what I recall, in most posts they say coal is no good in a Wayne Keith gasifier, since it has too much and too many nasties in it.
Coal gasification has been done in and right after WW2 in Europe. So basically it works, but you will have to deal with those nasties!

Best regards,


PS: Many others are more competent to comment on this. I just did a quick reply from my memory.

Coal? What do you mean by coal? Do you mean charcoal? Often times refered to as coal. Do you mean soft coal? Is this bituminous coal also known as mineral coal? Or are you talking about anthracite coal known as hard coal?
Coal = charcoal, Yes, it will work well.
Coal = bituminous coal. Forget it. Will swell up, clinker and gum up your fire tube.
Coal = anthracite. Small amounts will work as it is mostly pure carbon with little sulfur and clinkers.
Gary in the soft coal area of PA.

I do some blacksmithing and we use a grade of bituminous coal that comes from just above the first “anthracite” layer. we often have clinker contests when we shut down for lunch. You have to dig the clinker out of the forge and be able to suspend it in the air on your poker. I almost won last Saturday with a 6 inch diameter clinker “donut” about an inch thick. I say “almost” because, although I got it out of the firepot okay, it broke in half when I lifted it. Not a good thing to have in your grate.

Gary- when you say the bituminous coal “swells up”, do you mean that it “cokes up”? I have heard that not all bituminous coal does coke up well, and, as you probably know, that is a feature that we need in the forge. So we have to be very careful about our source for low sulphur, low ash (clinker) and high btu coal. We buy 22 ton to 26 ron loads about once a year and it is getting harder to get every day. Now they all seem to want us to buy a 100 ton car load since they don’t want to mess around with a single truck.

Pete Stanaitis

My understanding for a book learned point of view is:
a.) exactly like Gary says only “hard” coals are a go
b.) It all has to do with the total heating value of the feedstock and what heat the gasifier was designed to withstand.

Imagine it this way 1 cubic foot of wood contains ‘x’ btus.
One cubic foot of coal contains ‘x*4’ btus. Same volume, but a lot more energy.

A few ways a gasifier can be engineered to withstand this extra energy:
-Heavier/ improved material construction.
-Reintroduction of inert gasses (usually exhaust gases) to reduce the temperature of the combustion.
-Water injection at the hearth/ char bed (which produces additional hydrogen too).

The most practical use of coal in a Keith style woodgasifier system would be in the correct proportion with overhydrated wood chunks to allow you to use wet or green wood without the corresponding loss of gasification efficeincy because of the increased mositure content of wood.