Abstract: The conversion of lignocellulose biomass to liquid biofuels requires a far more complex technology than food crop-based first generation biofuel production does. Conversion rate and production capacity are also lower, but for advanced biofuel plants, the investment cost can be up to ten times higher. However, recent technological developments have made it possible to produce biofuels without endangering the continuous food supply. Lignocellulose biofuels can be produced from a wider range of raw materials such as forest residues and agricultural by-products. Unfortunately, collecting woody and herbaceous by-products is costly; therefore, we investigated the usability of short rotation coppices (SRC) as base material for biofuel production. The plantations are suitable for producing a large amount of biomass in a small area, and even in non-utilized agricultural areas. The dendromass from SRC is characterized by high bark content, which generates a high ash amount during utilization. Several studies confirm that bark content adversely affects both biochemical and thermochemical processes; our studies examined the importance of cutting-cycle selection and tree species on ash content during thermal treatment.