In future the usage of alternative biomass for energy generation becomes more and more important. Due to the CO2 problems and the raising prices for fossil fuels it is necessary to search for alternatives to wood. However the thermal conversion of biomass like agricultural residues in small furnace installations involves various problems. The most important reason is the low melting point of ash with temperatures mostly under 1000°C. Accordingly these fuels have got a high content of ash and nitrogen as well as a low abrasion resistance in compressed form. For solving these problems and using the biomass in a combustion system their fuel properties and the influence of additives to them were analysed. For preventing ash agglomeration it is essential to provide ideal combustion conditions and to avoid temperature peaks. Therefore it is necessary to get more detailed information of the thermal conversion, which can be split up in the process of drying, pyrolysis, gasification and combustion. In case of biomass the sub-step of pyrolysis is of special interest, since up to 85% of the solid may be converted. For the investigations of pyrolysis behaviour a pilot plant, which combines a thermo gravimetric scale and a differential scanning calorimeter, was adapted and applied. With this plant the fuel massloss and the heat of reaction of the volatiles dependent on pyrolysis time can be evaluated. Additionally the oxygen demand of the combustion of pyrolysis gas can be found out. With the knowledge of these parameters it is possible to ensure an ideal combustion in a furnace installation. The results of the tests showed a positive influence of additives to the ash melting behaviour. Unfortunately also negative effects to the ash content and the abrasion resistance of pellets could be recognised in case of the addition of inert additives like blast furnace slag. Hence it is necessary to add only a smidgen of inert substances. Concerning the pyrolysis further positive effects could be found out during the investigations with additives. Both applied substances, blast furnace slag and molasses, showed an increasing of secondary crack reactions, in which tars are split into shorter non condensable hydrocarbons. Mostly tars are undesirable, because they condense at low temperatures and following they pollute and clog up lines.