Anaerobic digestion of microalgae as a necessary step to make microalgal biodiesel sustainable

• Published in: Biotechnology advances Vol. 27; no. 4; pp. 409 - 416
• Main Authors: Sialve, Bruno, Bernet, Nicolas, Bernard, Olivier
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Inc 01.07.2009; Elsevier
• Subjects: Anaerobic digestion; Anaerobiosis; Biochemical methane potential; Biodegradation, Environmental; Biofuel; Biofuel production; Biogas; Biological and medical sciences; Biomass; Biotechnology; Carbon Dioxide - metabolism; CO 2 mitigation; Codigestion; Cyanobacteria - metabolism; Energy; Energy-Generating Resources; Environmental Engineering; Environmental Sciences; Eukaryota - metabolism; Fundamental and applied biological sciences. Psychology; Industrial applications and implications. Economical aspects; Life Sciences; Lipid Metabolism; Methane - metabolism; Microalgae; Pretreatment; Sodium - metabolism; CO 2 mitigation; Codigestion; Microalgae; Biochemical methane potential; Biogas; Biofuel; Pretreatment; Anaerobic digestion; Methane; mitigation; Algae; Carbon dioxide; CO; Biodiesel; MICROALGAE; ANAEROBIC DIGESTION, BIOCHEMICAL METHANE POTENTIAL, CODIGESTION, PRETREATMENT, BIOGAS, CO2 MITIGATION, BIOFUEL
• ISSN: 0734-9750; 1873-1899; 1873-1899
• DOI: 10.1016/j.biotechadv.2009.03.001

The potential of microalgae as a source of biofuels and as a technological solution for CO 2 fixation is subject to intense academic and industrial research. In the perspective of setting up massive cultures, the management of large quantities of residual biomass and the high amounts of fertilizers must be considered. Anaerobic digestion is a key process that can solve this waste issue as well as the economical and energetic balance of such a promising technology. Indeed, the conversion of algal biomass after lipid extraction into methane is a process that can recover more energy than the energy from the cell lipids. Three main bottlenecks are identified to digest microalgae. First, the biodegradability of microalgae can be low depending on both the biochemical composition and the nature of the cell wall. Then, the high cellular protein content results in ammonia release which can lead to potential toxicity. Finally, the presence of sodium for marine species can also affect the digester performance. Physico-chemical pretreatment, co-digestion, or control of gross composition are strategies that can significantly and efficiently increase the conversion yield of the algal organic matter into methane. When the cell lipid content does not exceed 40%, anaerobic digestion of the whole biomass appears to be the optimal strategy on an energy balance basis, for the energetic recovery of cell biomass. Lastly, the ability of these CO 2 consuming microalgae to purify biogas and concentrate methane is discussed.