Fuel characterization and biomass combustion properties of selected native woody shrub species from central Portugal and NW Spain

► Selected shrub native species from Spain and Portugal were characterized. ► Ashes of 1-2%, N > 0.6%, S < 0.1% and HHV of 21-24 MJ kg−1were found. ► Alkali metal 20-30% denote potential ash bed sintering/agglomeration and fouling risk. ► ash trace elements were below most of European limits.