Effect of sulfuric acid concentration on the yield and properties of the bio-oils obtained from the auger and fast pyrolysis of Douglas Fir

► Sulfuric acid reduces the yield of oil and increases the yield of char. ► Sulfuric acid enhances the production of anhydrosugars during pyrolysis. ► There is an optimum sulfuric acid concentration at which the yield of anhydro-sugars is maximized. ► Sulfuric acid addition increases water production. ► The yield of lignin derived compounds decreases when sulfuric acid was used.