Co-pyrolysis of microalgae and plastic: Characteristics and interaction effects

Abstract

To improve the quality of the oil produced from microalgae, the co-pyrolysis of low-density polyethylene (LDPE) and Nannochloropsis sp. (NS) in a fixed bed reactor was investigated at different mixing ratios. Co-pyrolysis improved the gas yield, and the lower heating value of the gas products increased obviously with an increase in the LDPE amount. Furthermore, co-pyrolysis promoted the generation of CH₄ and C₂₊, especially C₂H₄, with the maximum C₂₊ yield (84.86 mL/g) obtained with 75% LDPE. Meanwhile, the amounts of oxygenous and nitrogenous compounds in the liquid products decreased rapidly with LDPE addition. The aliphatic hydrocarbon content of the liquid products increased from 22.63% for NS pyrolysis to 77.4% with 25% LDPE. During co-pyrolysis with LDPE, O tended to evolve as H₂O and CO (rather than as CO₂ for NS pyrolysis) and N was more likely to be released into gas products, which enhanced the quality of the pyrolysis oil.

Keywords: Co-pyrolysis; Interaction effect; Low-density polyethylene; Nannochloropsis sp..