Microalgae are a potential candidate for biofuel production and environmental treatment because of their specific characteristics (e.g. fast growth, carbon neutral, and rich lipid accumulations). However, several primary bottlenecks still exist in current technologies, including low biomass conversion efficiency, bio-invasion from the external environment, limited or costly nutrient sources, and high energy and capital input for harvest, and stalling its industrial progression. Coupling biofuel production with environmental treatment renders microalgae a more feasible feedstock. This review focuses on microalgae biotechnologies for both bioenergy generation and environmental treatment (e.g. CO₂ sequestration and wastewater reclamation). Different intelligent technologies have been developed, especially during the last decade, to eliminate the bottlenecks, including mixotrophic/heterotrophic cultivation, immobilization, and co-cultivation. It has been realized that any single purpose for the cultivation of microalgae is not an economically feasible option. Combinations of applications in biorefineries are gradually reckoned to be necessary as it provides more economically feasible and environmentally sustainable operations. This presents microalgae as a special niche occupier linking the fields of energy and environmental sciences and technologies. The integrated application of microalgae is also proven by most of the life-cycle analysis studies. This study summarizes the latest development of primary microalgal biotechnologies in the two areas that will bring researchers a comprehensive view towards industrialization with an economic perspective.

Photobiological hydrogen production through algae (including green algae and cyanobacteria) is one of the most promising ways to obtain green hydrogen energy due to its outstanding light-harvesting and energy conversion efficacy. However, the sustainability and cost essentially impede its large-scale commercial production. This study aims to bridge this gap, present a blueprint for sustained and sustainable bioH₂ production, and provide scientists and policymakers with a reference and foundation to evaluate its economic feasibility when applied locally. Evaluation is based on a simplified assumption of functioning algae as living ‘solar panels’. By revisiting the current literature, recent advancements in this technology are identified, offering potential solutions to overcome the issues. A combination of a promising algal bioH₂ generating method with its derivative concept-design algae culturing model was compared with the largest photovoltaic electrolysis H₂ plant in the world hitherto to show both pros and cons of these two methods. A global spatiotemporal dynamic map and scalability analysis were performed to demonstrate the potential of algal bioH₂ production among various locations.

Correction for ‘Global potential of algae-based photobiological hydrogen production’ by Yimin Chen et al., Energy Environ. Sci., 2022, 15, 2843–2857, https://doi.org/10.1039/D2EE00342B.