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Item Biohydrogen production from waste substrates and its techno-economic analysis(Elsevier, 2023) Dikshit, P.K.; Poddar, M.K.; Chakma, S.The demand for alternative energy is increasing considerably due to the fast depletion of fossil fuel reserves and increasing greenhouse gases emission, causing serious climate change. Among various alternative energy sources, biohydrogen (H2) has achieved major traction due to its distinct properties like high-energy content, recyclability, and production of water on the combustion process. Although several processes are adopted for hydrogen production from a wide range of substrates, utilization of organic feedstock using dark fermentation has proven to be one of the most promising methods among all. However, the raw material cost, which contributes around 70%–80% of the total production expenses, is the major hurdle in the successful commercialization of this process. Organic wastes can be used as an alternative to pure carbons for the reduction of production cost. This chapter summarizes biohydrogen production from various waste substrates, its production process, microorganisms involved, fermentation approaches, and various factors that influence the production along with major advantages and challenges. Additionally, techno-economic analysis of biohydrogen production on an industrial scale from various organic wastes is also discussed in detail. © 2023 Elsevier Ltd. All rights reserved.Item Basic concepts of ultrasound and its effects on fuel processing(Bentham Science Publishers, 2023) Poddar, M.K.; Dikshit, P.K.; Chakma, S.Ultrasound-assisted technique is well-known for process intensification via chemical and physical changes under the influence of acoustic cavitation. Acoustic cavitation is the phenomenon of nucleation, growth, and collapse of cavitation bubbles into a liquid medium that augments the reaction kinetics and the final process yield. This chapter provides a fundamental and detailed understanding of the acoustic cavitation phenomenon. It includes the history and origin of the acoustic wave and its formation, the concept of cavitation bubbles, bubble nucleation and growth mechanism, cavitation effects, and its types. Numerous process parameters, such as applied frequency, intensity, temperature, dissolved gas content, etc., also directly or indirectly influence the cavitation threshold are also highlighted. Further, the ultrasound's physical and chemical effects involving various chemical and biochemical processes to enhance the process yield are also reviewed. The mode of generation of ultrasound energy and its measurement technique are also briefly discussed. Finally, an overview of modeling and simulation of radial motion of single bubble growth, its oscillation in both ultrasound-assisted and conventional systems, and bubble growth rate under rectified diffusion are also discussed in detail. © 2023 Bentham Science Publishers. All rights reserved.Item Application of ultrasound in microbial and algal biofuel production(Bentham Science Publishers, 2023) Poddar, M.K.; Pattanaik, L.; Dikshit, P.K.The application of ultrasound has received immense research attentions in the past few years due to its application in various sectors including dye degradation, pretreatment process, fuel production, bioprocessing, etc. Recently, ultrasonication has been used as a novel bioprocessing tool for enhancing biofuel production from microbial and algal biomass during the fermentation process. Additionally, this technique is also used in many areas of downstream processing such as extraction of lipids from biomass, filtration, and crystallization. The usage of ultrasonication during the fermentation process can result in the enhancement of the transfer of oxygen for aerobic culture, homogenization of biomass for the reduction in clump formation, and faster substrate transfer to biomass which further results in enhanced microbial growth. In view of this, the present chapter mainly focuses on the role of ultrasonication in microbial and algal lipid production and its extraction process with an aim for liquid biofuel production. Additionally, the influence of various operating parameters (power intensity, frequency, duration, reactor design, and kinetics) over the growth, lipid production, and extraction process are also described in detail. © 2023 Bentham Science Publishers. All rights reserved.Item Extraction and characterization of lignin from waste invasive weeds with dioxane-based process(Springer Science and Business Media Deutschland GmbH, 2023) Borah, A.J.; Dikshit, P.K.; Doloi, M.; Moholkar, V.S.; Poddar, M.K.This study has put forth the concept of “control through utilization” for invasive weeds, which cause severe damage to ecosystem and biodiversity. The study comprised of extraction of lignin and pretreatment of spent biomass of four invasive weeds. Lignin was extracted from native biomass using 1,4–dioxane as solvent. Lignin yield of all biomass varied in the range 8.61 − 11.14% w/w with the solvent recovery of 75.56–78.88% v/v. Extracted lignin was characterized using FTIR, TGA, and GPC. Lignin from Mikania micrantha had the highest thermal stability (T50% = 490 °C) and molecular weight (Mw = 5537 g/mol). The spent biomass was subjected to dilute acid pretreatment for synthesis of total reducing sugars (TRS). TRS yields from different entities were as follows: non-extracted biomass = 94.18 − 221.81 mg/g, warm water wash = 8.74 − 15.66 mg/g, and raw biomass = 115.9 − 391.27 mg/g raw biomass. Biomass of Saccharum spontaneum gave the highest TRS yield. Graphical abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.