A process for forming and maintaining a carbonaceous bed with coke replacement units suitable for use in pyrolytic processes includes the steps of: forming a plurality of non-coke units that are either or both irregularly shaped natural wood blocks and bricks including carbon-containing fines and one or more binders; forming an initial carbonaceous bed by a quantity of particles of coke in which at least about 25% of the carbon content of the initial bed is provided by said quantity of non-coke units and up to about 75% of the carbon content of the initial bed is provided by said quantity of particles of coke; and performing a pyrolytic process with the carbonaceous bed including reacting carbon in the bed with other added process material at an elevated temperature in the bed and supplementing carbon material during the pyrolytic process by adding additional carbon material of which at least 25% of the additional carbon material is not coke.