Benefits of combining anaerobic digestion and amino acid extraction from microalgae

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 258; pp. 1 - 9
• Main Authors: Ramos-Suárez, Juan L., Cuadra, Francisco García, Acién, F. Gabriel, Carreras, Nely
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-12-2014
• Subjects: Ammonia inhibition; Anaerobic digestion; Biogas; Biorefinery; Microalgae; Microalgae; Biogas; Biorefinery; Ammonia inhibition; Anaerobic digestion
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2014.07.086

•High biogas yields were obtained from amino acid-extracted microalgae.•Ammonia inhibition could be avoided by dilution of the substrate.•The acclimation of microorganisms improved the efficiency of the process.•Coupling anaerobic digestion to microalgae biorefineries could save costs in fertilizers and CO2.
The anaerobic digestion of Scenedesmus residues generated after a process of amino acid extraction with an extraction efficiency of 59% was thoroughly studied in 3L working volume semi-continuous reactors. Anaerobic digestion of high concentrated Scenedesmus residues (17.6%TS) was inhibited due to ammonia and volatile acids accumulation. Dilution of the substrate to 10.5%TS avoided the inhibition of the process. The acclimation of microorganisms to the digestion of the substrate caused a further improvement in the process performance. High biogas and methane yields (409.3 and 291.5LkgVS−1, respectively) were achieved at an organic loading rate of 3.85gVSL−1d−1 with an hydraulic retention time of 20days. Electrical and thermal energy (0.525kWh and 2305.9kJperkg−1dry cultivated biomass) generated by the combustion of methane could be used for the different steps within the culturing of microalgae and the amino acid extraction processes. Moreover, a mass balance suggested that nitrogen and carbon dioxide needs for growing microalgae could be cut to a maximum of 30% and 25%, respectively, thanks to the coupling of anaerobic digestion to the extraction of amino acids from microalgae.