Dear Colleagues,

The world is currently experiencing exponential population growth, coupled with the expansion of various industries and domestic activities; this is leading to the generation of an unprecedented volume of diverse wastes, encompassing both wastewater and solid waste. These waste streams pose a significant threat to downstream users' health and well-being, necessitating comprehensive treatment. However, the treatment of these waste materials comes at a considerable cost, making it imperative to adopt economically viable technologies for their remediation.

In addition to this pressing concern, we are confronted by the impending energy crisis. It is widely predicted that the extensive consumption of fossil-based fuels, such as petrol, natural gas, and coal, will deplete within the next half-century. This looming energy scarcity underscores the urgent need to explore alternative, sustainable sources of energy to meet our future energy demands. Among these alternatives, the anaerobic digestion process has emerged as a focal point of interest due to its potential to yield valuable byproducts, including bio-gas and bio-hydrogen.

Hydrogen, in particular, holds promise as a secondary energy source for the future. Its appeal lies in its clean energy attributes, diverse technological pathways for production and utilization, high gravimetric energy density, and remarkable efficiency. Consequently, research into hydrogen production and utilization assumes paramount importance.

The pursuit of carbon-neutral energy consumption is an essential component of maintaining a sustainable and eco-friendly social infrastructure. Renewable energy sources have gained traction as pivotal components of alternative energy strategies able to achieve carbon neutrality. Notably, biogas derived from biomass and waste materials stands out as the most forward-looking renewable energy source. Given this imperative, the development of biomass and waste-to-biogas technologies should be accelerated to unlock the full potential of biogas as a valuable resource.

Anaerobic fermentation represents a biotechnology well-suited to processing a wide array of organic solid wastes. Beyond the recovery of energy in the form of biogas (methane), a more sustainable approach involves valorizing organic waste by extracting high-value compounds such as carboxylic acids (VFA, lactic acid, MCFA), and PHA. Regulating mixed microbiomes to harvest these valuable carbon compounds in the aqueous phase presents an even more attractive prospect. Therefore, an alternative and viable solution lies in the valorization of organic waste via the recovery of these value-added compounds.

In light of these considerations, this Special Issue seeks to compile articles that contribute to the maximization of biogas, biohydrogen, organic carboxylic acids, and PHA production from biomass or wastewater. The topics of interest, while not exhaustive, encompass the following:

1. Advancements in biomass and waste utilization.
2. Enhancement of biogas quantity and quality.
3. Innovations in anaerobic digestion/fermentation processes.
4. Pre- and post-treatment techniques for biomass, organic waste, and digestate.
5. Strategies for recovering biogas and value-added resources from waste streams.
6. Biohydrogen generation.
7. Scaling up and commercial applications of biohydrogen, biogas, and organic acid generation processes.
8. Biological processes (fermentation, photobiological, microbial electrolysis, etc.).
9. Biomass utilization.
10. Waste utilization (industrial, agricultural, etc.).
11. Catalyst utilization for bio-gas and bio-hydrogen production from waste.
12. Microbial fuel cells for renewable energy extraction from waste.

This Special Issue welcomes contributions that explore the realms of bio-energy, bio-gas, bio-hydrogen, carboxylic acids, pretreatment, anaerobic treatment, wastewater, and solid waste. Your valuable research endeavors in these domains hold the potential to shape a more sustainable and energy-abundant future.

Dr. Hussein Al-Hazmi
Prof. Dr. Xiang Li
Guest Editors

Manuscript Submission Information

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• food waste
• wastewater treatment
• solid waste management
• energy crisis
• anaerobic digestion
• hydrogen production
• renewable energy
• biogas technology
• organic waste valorization
• biomass utilization
• carboxilic acids