After scrap wood came to have value as a commodity ( sold to overseas firms to mix with resin, extrude into boards, and sold as chip board, particle board and Scandinavian furniture) the burners fell into disuse back in the late 1970's. They were characterized as either cylinders capped with a half-ball of mesh, or cone-shaped with the top capped with mesh. All had a conveyor belt which dumped the slash wood and sawdust into a continuously burning fire.

Many outlasted the sawmils - standing sentinel over former sawmill sites in Oregon, Washington, Idaho that no longer even had any other portion of the mill remaining (including millpond). Within the past ten years, most have be cut down to recover the iron as scrap. If you see one - make your images soon. The remainder are rapidly disappearing. Use the access door, go inside and look upwards at the image potentials...