Co-pyrolysis of biomass with waste tyres: Upgrading of liquid bio-fuel

• Co-pyrolysis of biomass and waste tyres is evaluated.
• A single phase is obtained.
• The quality of the bio-oil is upgraded after the addition of waste tyres.
• Calorific value and acidity are synergically improved.
• A stable bio-oil is obtained.

Co-pyrolysis of forestry wastes and waste tyres is carried out using different facilities: a fixed bed reactor and a continuous auger reactor. Remarkably, only one phase is found in the liquid fraction, which is not achieved by mixture of the pure liquids. In addition, positive effects between waste tyre and biomass are evidenced, being more notable even synergetic in the auger reactor. It is found that whilst acidity, density and oxygen content decrease, pH and calorific value increase with respect to the merely biomass pyrolysis liquid, leading to upgraded bio-oil. Upgrading process is linked to the presence of radical interactions between waste tyres and biomass pyrolysis products. In addition, it is observed that the addition of waste tyres to the feedstock blend is significantly decreasing the amount of aldehydes and phenolic compounds, which is beneficial for improving the stability of the new bio-oils.