In this work, fuel characteristics such as proximate analysis, ultimate analysis, higher heating value, and ash composition of shells from four oilseed plants (hazelnut, walnut, almond, and sunflower) and olive husk were determined by analytical methods. Fuel properties for the combustion analysis of biomass can be conveniently grouped into physical, chemical, thermal, and mineral properties. The carbon content of selected biomass species varies from about 47.4% to 53.5% due to varying lignin and extractives content. The hydrogen content of the species varies from 5.8% to 6.7%. Oxygen content ranges from 35.5% to 41.6%, S is <0.1% and N ranges from 0.5-1.6%. Lignin content ranges from 17.0% to 52.3%. The higher heating values (HHVs) of selected samples were correlated with their lignin contents. There was a highly significant linear correlation between the HHVs of the samples and their lignin contents. The HHV (MJ kg(-1)) of the samples as a function of lignin content (L, wt%) was calculated using the following equation: HHV = 0.0889(L) + 16.8218; for which the correlation coefficient (r) was 0.9504. The HHVs calculated with this equation showed a mean difference of 0.056%.