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Bioethanol is the alternative to fossil fuels for the transport sector's environmental sustainability. Scientific journals have disclosed a few works on modeling and enhancing bioethanol production processes. To industrialize these production processes, however, the modeling requires consideration for mass and heat transfer, mainly when applying intensification machinery. Consequently, CFD is preferable to a comprehensive analysis of fluids. Computational fluid dynamics (CFD) configure the flowing progress of bioethanol production, the flow pattern distribution curve, and flow pattern visualization. This article reviews recent advances in CFD Modeling of bioethanol production processes in conventional and newly designed bioethanol production technologies, such as simultaneous saccharification and fermentation (SSF) and membrane bioreactor. None of other studies addressed a kinetic model of the fermentation process in the SSF and membrane bioreactors. For the design of new (SSF) and membrane bioreactors, CFD and its combination with other simulation software might deliver a wealth of useful data. The first section of this paper addresses the bioethanol production process of the second generation: pretreatment, enzymatic saccharification, and fermentation. The second section of this review discussed hydrodynamics, reaction kinetics, and bioreactor design, focusing on CFD models of the bioethanol production technology. A conclusion and a recommendation, this section concludes with a discussion of insights into unexplored areas of study and challenges in modeling bioethanol production processes. • Industrial applications of bioethanol production processes necessitate CFD modeling. • The review provides insight into CFD modeling of bioethanol production technology, especially SSF and membrane bioreactors. • This paper considers the methods used to produce bioethanol. • Perspectives in CFD modeling of bioethanol production processes are analyzed. [ABSTRACT FROM AUTHOR]

The main objective of this review paper is analyzes perspectives of manufacturing bioethanol via biotechnology, using sustainable management. Two categories are emphasized: (i) agro-industrial valuation, which represents alternative methods for bioethanol production, and (ii) Agro-industrial Techniques and Infrastructure Analysis. Future of biofuels is addressed in terms of applicability and production methods. Authors perform a systematic literature review to characterize the present state of knowledge on ethanol production. The study is conducted from a decision-making standpoint, so that they identify several problems (subcategories) in bioethanol production. The section on technology and industrial infrastructure focuses on advances in biorefineries, revealing technical and economic limitations, and also the gap between sustainable production policies and environmental impact. The second part of the paper presents the evolution of the industrial sector toward technological innovation and adoption of complex bio-production methods for clean energy production. This review mostly covers results reported over the past decade, with a special emphasis on papers published recently, from 2010 to 2021, therefore, it can serve for extended future research that would address additional specific categories. One concludes that the industrial sector must promote bioethanol production efficiently and sustainably, harmonized with the society and the environment. Sustainable production points to alternative energy sources based on cellulosic materials and third generation materials derived from algal biomass. • Chemical processes in the agro-industrial production sector include clean technologies. • Critical gaps for biofuel production contain factors that must be related to industrial processes and uncertain economic cost. • Technological integration of 1G and 2G bioethanol production can reduce operating costs and investment risks. • Biorefinery models use various biomass feedstocks, and they integrate 1st/2nd generation technological processes. [ABSTRACT FROM AUTHOR]

Brown algae adsorb a considerable amount of CO 2 and store carbon in their biomass more than many other algae species. Nowadays, depletion of fossil fuel resources, greenhouse gas emissions, climate change, and the future of human food security have encouraged scientists and policymakers to develop safer and more sustainable alternatives of energy sources. Brown algae have attracted most of this attention in North American countries to generate a wide range of products and biomass for biorefinery. In this review paper, various aspects of brown algae cultivation and its biorefinery process are discussed. Main drivers of the sectors, opportunities, challenges, and future prospects of brown algae-based biofuels in North America have been taken into account; the most appropriate processes and pathways are compared to maximize the outputs and environmental benefits, and minimize costs and drawbacks of the industry. Analysis and predictions of renewable energy future in North American countries revealed that biomass-derived fuels, including brown algae biofuels, will play an important role especially in the transportation sector. These biofuels, including bioethanol and biodiesel are accompanied by various co-products and by-products in an optimized biorefinery system to convert every available component of brown algae. However, cultivation of brown algae to produce biomass at a commercial scale with minimum costs and market demands are the main challenges of algal biofuels. Finally, expanding the value chain of the brown algae biorefinery by producing more advanced biofuels such as aviation fuels and value-added co- and by-products would significantly impact North American countries' gross domestic product. • Many studies related to biofuel production from brown algae are reviewed comprehensively. • Brown algae have attracted significant attention in North America. • Costs and markets demands are two main challenges for this algal energy. • Effective strategies for optimal production of biofuel from brown algae are provided. • Current challenges and future prospects for biofuel from brown algae are discussed. [ABSTRACT FROM AUTHOR]

Increased environmental concern over climate change due to higher oil usage has made human being to shift to cleaner and greener alternatives. The utilization of abundant agricultural waste streams as renewable feedstock for biofuels production can be a pivotal strategy. Among others, rice is one of the most largely grown crops, and more than 4.8% of the total production goes to waste. Although previous reviews are related to biofuels obtained from some rice waste, most of those are focused on lignocellulosic rice residues with much attention to thermo-chemical processes. The present paper, instead, reviews for the first time the biotechnological approaches to convert all rice wastes, like rice husk, rice straw, broken rice, discolored rice, unripe rice, into liquid (bioethanol, biobutanol, biodiesel), and gaseous (biogas, biohydrogen) biofuels through the use of pure or mixed microbial cultures. The global availability of each rice byproduct has been also investigated and the potential of rice waste as a 'fuel farm' has been estimated for bioethanol. The physical, chemical, enzymatic, or microbial pretreatments, which play a key role in making carbon available for hydrolysis and fermentation, are here discussed and evaluated. Despite the great promise of technologies so far developed, further research is still required for their up-scale and industrial commercialization. Moreover, future process integrations will open the landscape to biorefinery schemes where rice waste streams can be processed into biofuels and other added-value products, towards the full exploitation of the feedstocks and the economic and environmental sustainability of the overall process. [Display omitted] • Rice waste has the potential to produce many gigalitres of biofuels worldwide. • Selection of pretreatment is the key to obtain the highest biofuel production. • Different biotechnological approaches for biofuel production are elucidated. • Complete rice waste valorization using a biorefinery approach is underscored. [ABSTRACT FROM AUTHOR]

Indonesia has an intensive agro-industrial sector which evolves large volumes of residues each year. Currently, these residues are under-utilized and have a deleterious impact on the environment, Oil Palm Empty Fruit Bunches (OPEFBs) in particular are highly abundant and offer good potential for conversion to bioenergy and bio-based products, in particular bioethanol and xylitol (widely used as an artificial sweetener and can substitute sugar in food and pharmaceutical industries). This paper provides a comprehensive review of the techno-economic opportunities and challenges for the wider utilization of OPEFBs for the generation of bioethanol and xylitol in Indonesia. This review highlights the significant potential for the valorization of OPEFB based on resource availability in the country (828 MWe/year or 45.86 Mt/year) and growing demand for both bioethanol (from 0.22 billion L in 2019 to 10.38 billion L in 2025) and xylitol (up to 2.20 kt in 2020). Various process configurations were explored to assess the potential for simultaneous co-production of bioethanol and xylitol. A mass balance and techno-economic assessment showed that the preferred scenario was Scenario 3 (co-production of bioethanol with xylitol and lignin) and that this has the potential to generate 46,145 kL bioethanol, 7.716 kt xylitol, and 25.704 kt lignin per year. This is significant given the limited production for both bioethanol and xylitol in the country currently. Further work is required to address challenges around technical, policy and supply chains. This work provides an original and novel strategy to support the wider adoption of commercially viable bioethanol production in Indonesia. • An abundance of oil palm empty fruit bunches (OPEFB) creates prospect for biorefining. • Manufacture and supply of bioethanol and xylitol in Indonesia is feasible. • Multiple scenarios are proposed for mono- and co-production of bioethanol and xylitol. • Co-production of bioethanol and xylitol promotes sustainable bioeconomy. • Challenges remain on scalability, financial incentives and supply chain integration. [ABSTRACT FROM AUTHOR]

The Canadian province of British Columbia has large forestry resources and therefore provides an informative example of the potential role of bioenergy in mitigating GHG emissions. Even in biomass-rich British Columbia, forestry resources are only sufficient to meet part of the energy demand. This paper compares different energy conversion routes for forestry waste materials: via hydrothermal liquefaction, thermochemical methanol and bioethanol, renewable natural gas, cogeneration of heat and power, heat-only boilers, and power-only generation. The GHG savings, health impacts, minimum selling prices, and GHG abatement costs for each option are estimated by combining life cycle assessment with a discounted cash flow model. The input-based functional unit of 1 oven-dry tonne biomass provides a better basis for comparing possible uses of finite biomass supply than the commonly-used output-based functional unit of 1 GJ bioenergy. Heat-only boiler for district heating gives the highest GHG reduction of 960 kgCO 2 -eq per oven-dry tonne feedstock, while power-only generation delivers minimal GHG benefit in British Columbia. Heat-only boiler and cogeneration offer the lowest GHG abatement costs (<$-20/tCO 2 -eq), due to lower costs and higher energy conversion efficiencies, and are already economically viable, but will not use all the available resources because health impacts generated by biomass combustion limit their deployment, despite life cycle health benefits for avoiding hazardous emissions from slash burning of forestry waste materials. Refined biofuel options are much less cost-effective (>$50/tCO 2 -eq); further technology improvement and policy support are needed to offset the cost disadvantage. • Comparison based on 1 ODT biomass identifies the most efficient way to utilize this scarce resource. • Producing energy from forestry waste materials can reduce emissions of GHGs and other pollutants. • Biomass-fired heat boiler gives maximum GHG mitigation per ODT feedstock. • Biomass-fired heat boiler and cogeneration are the most cost-effective in GHG mitigation. • Liquid biofuel options cause lower local health impacts but at higher GHG abatement costs. [ABSTRACT FROM AUTHOR]

Fossil fuel depletion and strict government regulations have necessitated the finding of alternatives to conventional fuel sources. The growing population and better transport are increasing the need for energy every day. The pollution and disposal of agriculture and food waste are still serious problems to be tackled. Bioethanol has proved an alternative to S.I. engine diesel and gasoline. 10% ethanol blending is widely used by passenger cars worldwide and countries such as India have announced the implementation of a 20% ethanol blending in petrol. As a result, demand for ethanol is growing and there is inadequate bioethanol supply to meet demand. This paper portrays the extraction of ethanol from the waste pomegranate fruits and effect of its different blends on the spark ignited engine performance. Ethanol was extracted using fermentation and steam distillation processes from waste pomegranate fruit. Four blends were prepared on volumetric basis and tested for various performance and emission parameters at a constant compression ratio of 10:1 and wide-open throttle at various engine speeds. Indicated power, volumetric efficiency, and mechanical efficiency were improved by ethanol enrichment. Enrichments of ethanol decrease emissions of HC, CO and CO 2 , however increase nitrogen oxide emissions. The engine performance was found optimal for WPFE15 among all fuel blend studied. This study recommends the use of waste pomegranate fruits as a source for production of second-generation ethanol if after treatments be performed to reduce NOx emissions. This study proposes the use of waste pomegranate fruits for second-generation ethanol processing, if NOx pollution after treatment is carried out. • The first study on waste pomegranate fruit ethanol on SI engine performance. • Outcome will provide alternative source for ethanol production. • Different ethanol blends were prepared and tested. • Improved engine performance and emissions (HC, CO and CO 2 reduce while NOX increases) with ethanol addition. • Outcome will help in solid waste management and pollution control. [ABSTRACT FROM AUTHOR]