Microalgae-based biorefinery for biostimulant and biogas production: An integrated approach for resource recovery

Microalgae can contribute solving global challenges, including energy, climate, resource depletion, and food demand. A multi-product biorefinery approach can enhance profitability by generating cost-effective and valuable bio-based products. This study evaluated the potential of Scenedesmus sp. microalgal biomass grown in a demonstrative raceway pond to produce valuable bioproducts (biostimulants) and biogas. Bioassays using watercress, mungbeans, and wheat confirmed the plant biostimulant potential of microalgal biomass extracts, showing effects similar to gibberellins, auxins, and cytokinins. Mesophilic biochemical methane potential (BMP) tests demonstrated that extracting biostimulants from microalgae biomass increased the methane yield by 20 % (from 244 to 293 mL CH 4 ·g −1 VS), and improved the kinetics of the process, which was attributed to the disruption of the microalgal cell wall during metabolite extraction. This novel biorefinery approach demonstrated valuable biostimulants production and bioenergy recovery from residual biomass. These findings provide new insights to optimise the valorisation of biomass in microalgal biorefineries, fostering environmentally friendly and economically viable agricultural practices aligned with circular economy principles. • Scenedesmus sp. microalgal biomass was grown in a demonstrative raceway pond. • Scenedesmus sp. biomass was used to produce agricultural biostimulants and biogas. • Bioassays confirmed the biostimulant potential of microalgal biomass on crops. • The extraction of biostimulants enhanced the methane yield and kinetics by 10–20 %.