Sustainable circular biorefinery approach for novel building blocks and bioenergy production from algae using microbial fuel cell.

The imminent need for transition to a circular biorefinery using microbial fuel cells (MFC), based on the valorization of renewable resources, will ameliorate the carbon footprint induced by industrialization. MFC catalyzed by bioelectrochemical process drew significant attention initially for its exceptional potential for integrated production of biochemicals and bioenergy. Nonetheless, the associated costly bioproduct production and slow microbial kinetics have constrained its commercialization. This review encompasses the potential and development of macroalgal biomass as a substrate in the MFC system for L-lactic acid (L-LA) and bioelectricity generation. Besides, an insight into the state-of-the-art technological advancement in the MFC system is also deliberated in detail. Investigations in recent years have shown that MFC developed with different anolyte enhances power density from several µW/m2 up to 8160 mW/m2. Further, this review provides a plausible picture of macroalgal-based L-LA and bioelectricity circular biorefinery in the MFC system for future research directions.

Progress in thermochemical co-processing of biomass and sludge for sustainable energy, value-added products and circular economy.

To achieve the main goal of net zero carbon emission, the shift from conventional fossil-based energy/products to renewable and low carbon-based energy/products is necessary. Biomass has been perceived as a carbon-neutral source from which energy and value-added products can be derived, while sludge is a slurry waste that inherently contains high amount of minerals and organic matters. Hence, thermochemical co-processing of biomass wastes and sludge could create positive synergistic effects, resulting in enhanced performance of the process (higher conversion or yield) and improved qualities or characteristics of the products as compared to that of mono-processing. This review presents the current progress and development for various thermochemical techniques of biomass-sludge co-conversion to energy and high-value products, and the potential applications of these products from circular economy's point of view. Also, these technologies are discussed from economic and environmental standpoints, and the outlook towards technology maturation and successful commercialization is laid out.

A review on potential of green solvents in hydrothermal liquefaction (HTL) of lignin.

One of the greatest challenges in biorefinery is to reduce biomass' recalcitrance and enable valorization of lignin into higher value compounds. Likewise, green solvents and hydrothermal liquefaction (HTL) with feasible economic viability, functionality, and environmental sustainability have been widely introduced in extraction and conversion of lignin. This review starts with the underscore of disadvantages and limitations of conventional pretreatment approaches and role of green solvents in lignin extraction. Subsequently, the effect of process parameters along with the reaction mechanisms and kinetics on conversion of lignin through HTL were comprehensively reviewed. The limitations of green solvents in extraction and HTL of lignin from biomass were discussed based on the current advancements of the field and future research scopes were also proposed. More details info on HTL of biomass derived lignin which avoid the energy-intensive drying procedures are crucial for the accelerated development and deployment of the advanced lignin biorefinery.

A state-of-the-art review on capture and separation of hazardous hydrogen sulfide (H2S): Recent advances, challenges and outlook.

Hydrogen sulfide (H2S) is a flammable, corrosive and lethal gas even at low concentrations (ppm levels). Hence, the capture and removal of H2S from various emitting sources (such as oil and gas processing facilities, natural emissions, sewage treatment plants, landfills and other industrial plants) is necessary to prevent and mitigate its adverse effects on human (causing respiratory failure and asphyxiation), environment (creating highly flammable and explosive environment), and facilities (resulting in corrosion of industrial equipment and pipelines). In this review, the state-of-the-art technologies for H2S capture and removal are reviewed and discussed. In particular, the recent technologies for H2S removal such as membrane, adsorption, absorption and membrane contactor are extensively reviewed. To date, adsorption using metal oxide-based sorbents is by far the most established technology in commercial scale for the fine removal of H2S, while solvent absorption is also industrially matured for bulk removal of CO2 and H2S simultaneously. In addition, the strengths, limitations, technological gaps and way forward for each technology are also outlined. Furthermore, the comparison of established carbon capture technologies in simultaneous and selective removal of H2S-CO2 is also comprehensively discussed and presented. It was found that the existing carbon capture technologies are not adequate for the selective removal of H2S from CO2 due to their similar characteristics, and thus extensive research is still needed in this area.