Abstract: Combustible off-gas(es) produced by the process of pyrolysis are superheated; and a pressurized gaseous mixture including oxygen, normally compressed air, is preheated; before, and by, a burning of the combustible off-gas(es) produced by process of pyrolysis in the presence of stoichiometric oxygen. The burning transpires in a large number of relatively small burner cups having bulbously-shaped and exhaust-constricted combustion chambers. The burner cups are both individually, and collectively, adjustable in their uptake of combustible gases by adjusting the flow of compressed air. The combustion in each burner cup is very complete and efficient nonetheless to having increased area contact with the chamber wall, and nonetheless to the rapidly and turbulent flow of gases, because everything contributing to or touching the combustion reaction is optimally hot, and because the shape of the burner cups holds the combustion optimally long.