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

Area of Science:

• Chemical Engineering
• Materials Science
• Biotechnology

Background:

• Microalgae pyrolysis yields oil, but quality can be limited by oxygen and nitrogen content.
• Low-density polyethylene (LDPE) is a common plastic waste product.
• Improving the quality of bio-oil from microalgae is crucial for its sustainable utilization.

Purpose of the Study:

• To investigate the co-pyrolysis of Nannochloropsis sp. (NS) and LDPE to enhance microalgae oil quality.
• To determine the effect of varying LDPE mixing ratios on pyrolysis products.
• To analyze the chemical composition of liquid products and gas yields.

Main Methods:

• Co-pyrolysis of NS and LDPE in a fixed-bed reactor at various mixing ratios.
• Analysis of gas yield, lower heating value, and composition (CH4, C2+).
• Characterization of liquid products, focusing on aliphatic hydrocarbon content and heteroatomic compounds.

Main Results:

• Co-pyrolysis increased gas yield and its lower heating value with higher LDPE content.
• Maximum C2+ yield (84.86 mL/g) achieved at 75% LDPE, with increased CH4 and C2H4 generation.
• Aliphatic hydrocarbon content in liquid products increased from 22.63% (NS only) to 77.4% (with 25% LDPE).
• Oxygen evolved mainly as H2O and CO, and nitrogen was released into gas products, reducing their content in the oil.

Conclusions:

• Co-pyrolysis of NS and LDPE is an effective method to improve microalgae pyrolysis oil quality.
• Increasing LDPE content favorably alters the product distribution, enhancing oil quality.
• This approach offers a potential route for valorizing plastic waste and microalgae biomass simultaneously.