Efficiency and biotechnological aspects of biogas production from microalgal substrates

• Conversion of photosynthetic microalgae into biogas is a simple and straight-forward route for bioenergy generation.
• This review provides a state-of-the-are summary of the research made in the field of anaerobic digestion processes of microalgal biomass.
• Biological and technological aspects are summarized.
• Future prospects and challenges are highlighted.
• An extended data summary is provided as Tables 1–3, allowing a comprehensive overview of the past achievements.

Photosynthetic organisms like plants and algae can harvest, convert, and store solar energy and thus represent readily available sources for renewable biofuels production on a domestic or industrial scale. Anaerobic digestion (AD) of the organic biomass yields biogas, containing methane and carbon dioxide as major constituents. Combustion of the biogas or purification of the energy-rich methane fraction can be applied to provide electricity or fuel. AD procedures have been applied for several decades with organic waste, animal products, or higher plants and more recently, utilization of photosynthetic algae as substrates have gained considerable research interest. To provide an overview of recent research efforts made to characterize the AD process of microalgal biomass, we present extended summaries of experimentally determined biochemical methane potentials (BMP), biomass pretreatment options and digestion strategies in this article. We conclude that cultivation options, biomass composition and time of harvesting, application of biomass pretreatment strategies, and parameters of the digestion process are all important factors, which can significantly affect the AD process efficiency. The transition from batch to continuous microalgal biomass digestion trials, accompanied by state-of-the-art analytical techniques, is now in demand to refine the assessments of the overall process feasibility.