As it operates a modern flue gas cleaning system, the Altenstadt combined heat and power plant can burn fuels of different wood classes. This includes wood of waste wood classes AI to AIII which many smaller biomass CHPs cannot use due to their less powerful flue gas treatment equipment.

Apart from waste wood, sawmill waste (e.g. saw dust) and fresh forestry wood also play a significant role in energy production. The new wood used is mainly tree thinnings, stool, wind breakage, smallwood and wood from branches and treetops which cannot be used for production. Most of the wood used was usually burnt or chaffed and scattered to rot as smallwood directly in the forest as there was no market for it.

Both the forestry wood and the waste wood need to be treated before they can be burnt. They are chopped to produce wood chips which should be of a certain size. After that, foreign bodies such as metal parts are removed from the fuel to protect the boiler from damage.