The paper discusses the potential of anaerobic digestion as a sustainable process for microalgal biodiesel production. It highlights the challenges and strategies involved in managing large-scale microalgal cultures, particularly the disposal of residual biomass and the high demand for fertilizers. Anaerobic digestion is proposed as a solution to these issues, as it can recover more energy than the energy derived from cell lipids. The study identifies three main bottlenecks in digesting microalgae: low biodegradability due to biochemical composition and cell wall structure, ammonia release from high cellular protein content, and sodium toxicity in marine species. To overcome these challenges, physico-chemical pretreatment, co-digestion, and control of gross composition are suggested. The paper also discusses the ability of microalgae to purify biogas and concentrate methane, and provides a detailed review of the theoretical approach to methane potential and ammonium release, as well as operating conditions. Finally, it compares the direct strategy of methanizing the whole biomass with the indirect strategy of recovering lipids, concluding that direct methanization is more energy-efficient when the lipid content is below 40%.The paper discusses the potential of anaerobic digestion as a sustainable process for microalgal biodiesel production. It highlights the challenges and strategies involved in managing large-scale microalgal cultures, particularly the disposal of residual biomass and the high demand for fertilizers. Anaerobic digestion is proposed as a solution to these issues, as it can recover more energy than the energy derived from cell lipids. The study identifies three main bottlenecks in digesting microalgae: low biodegradability due to biochemical composition and cell wall structure, ammonia release from high cellular protein content, and sodium toxicity in marine species. To overcome these challenges, physico-chemical pretreatment, co-digestion, and control of gross composition are suggested. The paper also discusses the ability of microalgae to purify biogas and concentrate methane, and provides a detailed review of the theoretical approach to methane potential and ammonium release, as well as operating conditions. Finally, it compares the direct strategy of methanizing the whole biomass with the indirect strategy of recovering lipids, concluding that direct methanization is more energy-efficient when the lipid content is below 40%.