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[Display omitted] • Renewable biomass, microalgae have immense potential for sustainable H 2 production. • Dark fermentation and photolysis are currently emerging biotechnological routes. • Biowaste-syngas- H 2 could be a commercially adoptable process for low-cost economics. • Global warming, acidification, and eutrophication are key factors for H 2 scale-up. • Biomass recalcitrance, achieving Thauer Limit and stable H 2 production are key challenges. Biohydrogen (bio-H 2) is regarded as a clean, non-toxic, energy carrier and has enormous potential for transforming fossil fuel-based economy. The development of a continuous high-rate H 2 production with low-cost economics following an environmentally friendly approach should be admired for technology demonstration. Thus, the current review discusses the biotechnological and thermochemical pathways for H 2 production. Thermochemical conversion involves pyrolysis and gasification routes, while biotechnological involves light-dependent processes (e.g., direct and indirect photolysis, photo/ dark fermentation strategies). Moreover, environmentally friendly technologies can be created while utilizing renewable energy sources including lignocellulosic, wastewater, sludge, microalgae, and others, which are still being developed. Lifecycle assessment (LCA) evaluates and integrates the economic, environmental, and social performance of H 2 production from biomass, microalgae, and biochar. Moreover, system boundaries evaluation, i.e., global warming potential, acidification, eutrophication, and sensitivity analysis could lead in development of sustainable bioenergy transition with high economic and environmental benefits. [ABSTRACT FROM AUTHOR]

[Display omitted] • Overview of challenges and opportunities of low carbon circular bioeconomy. • Development of low carbon circular bioeconomy were discussed. • Co-evolution of ecosystems, technologies, business strategies and user practices was analyzed. • Overview of value-added products production from these substrates were review. • Metabolic pathway of acidogenic fermentation was reviewed. The development of sustainable and low carbon impact processes for a suitable management of waste and by-products coming from different factors of the industrial value chain like agricultural, forestry and food processing industries. Implementing this will helps to avoid the negative environmental impact and global warming. The application of the circular bioeconomy (CB) and the circular economic models have been shown to be a great opportunity for facing the waste and by-products issues by bringing sustainable processing systems which allow to the value chains be more responsible and resilient. In addition, biorefinery approach coupled to CB context could offer different solution and insights to conquer the current challenges related to decrease the fossil fuel dependency as well as increase efficiency of resource recovery and processing cost of the industrial residues. It is worth to remark the important role that the biotechnological processes such as fermentative, digestive and enzymatic conversions play for an effective waste management and carbon neutrality. [ABSTRACT FROM AUTHOR]