Comparison of fast pyrolysis bio-oils from straw and miscanthus

Fast pyrolysis is one of the most promising conversion processes for producing advanced biofuels, which can be used as substitute for fuel oils or chemicals. This paper investigates the fast pyrolysis of two common types of biomass: a mixture of wheat/barley straw as typical agriculture residue and miscanthus as fast-growing energy plant. All experiments were performed using an ablative hot surface reactor. It was observed that the product yields by using wheat/barley straw and miscanthus are almost similar on mass basis. Noteworthy were the higher share on reaction water and a lower content of organics in the wheat/barley straw based pyrolysis bio-oil. As a result of the high total water content (about 48 wt.-%), the bio-oil separated into two phases: an upper aqueous phase and a bottom tarry phase. The amount of water-soluble organic compounds contained in the aqueous phase of bio-oil derived from miscanthus pyrolysis can be attributed to the higher amount of hemicellulose present in miscanthus compared to straw. The phase separation by decantation is not an efficient method to reduce the water content and total acid number because a part of valuable components will be lost to the aqueous phase.