About this Research Topic
The amount of waste generated due to human activities have grown steadily during the past decades. Although waste management technologies and practices have evolved considerably, the appearance of new contaminants and the constant evolving of human lifestyles poses new challenges on the environment, demanding the development of alternative management approaches. Moreover, most of the conventional waste management technologies make use of relatively large amounts of energy, despite a significant energy content in many types of organic wastes, which often remains untapped. Wastewaters represent a classic illustration of this problem. It has been estimated that the treatment of 1 m3 of wastewater requires about 0.5 kWh of energy, which represents around 0.5% of the total world power budget. This contrasts with the chemical energy available in the raw wastewater, that might exceed the power requirements in a wastewater treatment facility by a factor of 9.3.
There exists a wide spectrum of technologies intended for energy valorization of wastes that can be grouped under thermochemical, physicochemical and biochemical processes. Most of these are mature technologies (e.g.: combustion, anaerobic digestion, etc) that have widely proved their economic and technical feasibility. However, they are very often too rigid in the sense that, for each of them, the waste feedstocks must meet very specific requirements and the energy products are usually restricted to only one.
Microbial electrochemical technologies (MET), that can be included within the biochemical processes mentioned above, have evolved during the past 15 years becoming a promising and more flexible alternative for waste feedstock valorization (solid, liquid and gaseous waste streams) and producing energy carrier (electricity, liquid fuel, gas fuel). MET encompasses a group of technologies derived from conventional electrochemical systems in which bioelectrochemical reactions are directly or indirectly linked to the metabolic activity of electrogenic microorganisms. In contrast to the conventional technologies mentioned above, METs have not yet made the leap to commercial scale, as many challenges and issues (mostly techno-economic in nature) remain unresolved, necessitating a multidisciplinary approach if they are to be overcome.
This Research Topic aims at providing the readers with insights on the use of MET as renewable energy producing devices. We welcome basic and applied studies on using MET for energy valorization of liquid, solid and gaseous waste streams. We invite contributions (original research papers, short communications, review/mini-review papers, perspectives, commentaries and opinion papers, etc.) about all the areas involved in the development of this technology.
More specifically, this Research Topic will cover:
• Conventional biofuels and (alternative) energy carriers such as methane, hydrogen, methanol, electricity, ammonia, etc.
• Energy efficiency.
• Case studies.
• Mathematical modelling.
• Life-cycle and techno-economic analysis.
• Up-scaling experiences.
• Integration with other (bio) technologies.
• Challenges and opportunities of using solid, liquid and gas feedstocks.
• Novel materials and reactor configurations.
• Novel microbial electrochemical technologies.
Keywords: Microbial electrochemical technologies, waste valorization, bioelectrochemical systems, energy carriers, energy efficiency
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