Mechanistic insights into the synergistic pyrolysis of microalgae (Chlorella vulgaris) biochemical components

Microalgae are promising renewable feedstocks for thermochemical conversion due to their rapid growth, high biochemical diversity, and non-competition with food resources. However, the synergistic interactions among carbohydrates, proteins, and lipids during microalgae pyrolysis remain insufficiently understood, hindering the rational control of product distribution. In this study, an improved extraction protocol was developed to obtain high-purity carbohydrate, protein, and lipid fractions from Chlorella vulgaris , enabling systematic evaluation of component-specific and interactive effects during pyrolysis. Co-pyrolysis experiments were conducted using both the extracted fractions and representative model compounds (glucose, aspartic acid, and glycerol monostearate), with product evolution analyzed by Py-GC/MS. The extracted components exhibited thermal decomposition behaviors comparable to those of their corresponding model compounds, confirming the validity of the extraction strategy and model selection. Carbohydrate-protein co-pyrolysis promoted Maillard reactions between amino and carbonyl groups, significantly enhancing the formation of nitrogen-containing compounds such as pyridines and pyrroles. In contrast, protein–lipid interactions favored carbonization pathways, increasing biochar yields while suppressing bio-oil formation. Carbohydrate–lipid co-pyrolysis displayed limited synergy, primarily due to overlapping decomposition pathways and chemically similar oxygenated products. Overall, this work elucidates component-dependent synergistic mechanisms in microalgae pyrolysis and provides a validated framework for predicting and regulating product distributions from microalgal biomass.