Sustainable environmental management and related biofuel technologies.

Butanol can be produced from renewable sources via the acetone-butanol-ethanol (ABE) fermentation route to create biobutanol or from fossil fuel to create petrobutanol. Despite the similar chemical properties of these two forms of butanol, the market penetration of biobutanol is still hindered due to its higher production costs compared to those for petrobutanol. This review article traces the history of the butanol industry and discusses recent advances in butanol production by ABE fermentation, with several novel approaches being highlighted. These approaches include searching for abundant and inexpensive substrates and optimising upstream and downstream processes. As butanol production by ABE fermentation consists of several critical stages, this review article divides the whole process into five significant steps: (1) feedstock selection, (2) upstream, (3) midstream, (4) downstream and (5) final products. Recent progress involving all stages along with their challenges and potential research routes are summarised. Recent progresses in the direct use of ABE as a biofuel are also reviewed in brief. Low butanol yield and end-product toxicity remain the major drawbacks of a typical butanol production by ABE fermentation. For successful biobutanol production, a number of critical issues should be considered. These include the development of clostridial and non-clostridial strains as well as innovative in-situ recovery methods integrated with the ABE fermentation process. Finally, future research direction of butanol production by ABE fermentation is presented in the last section of this article.

Recent advances in butanol production by acetone-butanol-ethanol (ABE) fermentation

Butanol has similar characteristics to gasoline, and could provide an alternative oxygenate to ethanol in blended fuels. Butanol can be produced either via the biotechnological route, using microorganisms such as clostridia, or by the chemical route, using petroleum. Recently, interest has grown in the possibility of catalytic coupling of bioethanol into butanol over various heterogenic systems. This reaction has great potential, and could be a step towards overcoming the disadvantages of bioethanol as a sustainable transportation fuel. This paper summarizes the latest research on butanol synthesis for the production of biofuels in different biotechnological and chemical ways; it also compares potentialities and limitations of these strategies.

Butanol Synthesis Routes for Biofuel Production: Trends and Perspectives.

Microalgae have gained interest over the century due to numerous intrinsic attributes surpassing higher plants, making them a potential feedstock for third-generation biofuel production. The current state of art technologies produces biodiesel from microalgal biomass attributed to high intrinsic neutral-lipid contents. However, persisting hurdles in terms of techno-economic feasibility have impeded commercial-scale operations. The latent qualities of microalgae towards the accumulation of multiple high-value products ranging from animal feed to pharmaceuticals adds up to the economic feasibility. Alternatively, the high abundant carbohydrate contents of microalgal strains are used as low-cost substrates for the growth of commercially important microbes to synthesize biofuels. Novel carbohydrate enhancement strategies such as two-stage cultivation, phytohormones, starvation strategies, combinatorial stress strategies, etc., are frequently emerging to mitigate the challenges. Therefore, this study targets to review the recent trends in tuning the microalgal metabolism for increased carbohydrates and associated biofuel generation to attain process feasibility and sustainability. According to recent reports, nitrogen limitation, phosphate limitation, the optimal light intensity with reduced dissolved oxygen, limited inorganic carbon, optimal organic carbon levels, and indole-3-acetic acid augmented the carbohydrate productivity in different microalgal strains. Further analysis on different pretreatment methods highlighted electric-based physical treatment strategies with high efficiencies and less energy requirements of 13.3 kJ to 1.5 MJ per kg biomass. The production cost for microalgae-based bioethanol varies from US$ 1.67 to 31.36 per gallon for different process scenarios, which needs further attention.

Microalgae: Sustainable resource of carbohydrates in third-generation biofuel production

The role of nanoparticles on biofuel production and as an additive in ternary blend fuelled diesel engine: A review

Abstract Finite availability of conventional fossil carbonaceous fuels coupled with increasing pollution due to their overexploitation has necessitated the quest for renewable fuels. Consequently, biomass-derived fuels are gaining importance due to their economic viability and environment-friendly nature. Among various liquid biofuels, biobutanol is being considered as a suitable and sustainable alternative to gasoline. This paper reviews the present state of the preprocessing of the feedstock, biobutanol production through fermentation and separation processes. Low butanol yield and its toxicity are the major bottlenecks. The use of metabolic engineering and integrated fermentation and product recovery techniques has the potential to overcome these challenges. The application of different nanocatalysts to overcome the existing challenges in the biobutanol field is gaining much interest. For the sustainable production of biobutanol, algae, a third-generation feedstock has also been evaluated.

Recent trends in biobutanol production

Growths of Lyngbya limnetica and Oscillatoria obscura were investigated at varying pH, light intensity, temperature, and trace element concentration with a view to optimize these parameters for obtaining the maximum carbohydrate content. The maximum growth for both strains was obtained at pH 9.0 and temperature 20 ± 3 °C using a light intensity of 68.0 μmol m−2 s−1 with continuous shaking. Growth under the nitrogen starvation condition affected the carbohydrate content more compared to the phosphorus starvation, and maximum concentrations were found as 0.660 and 0.621 g/g of dry biomass for L. limnetica and O. obscura, respectively. Under the optimized nitrogen-rich conditions, the specific growth rates for the two strains were found to be 0.187 and 0.215 day−1, respectively. The two-stage growth studies under nitrogen-rich (stage I) followed by nitrogen starvation (stage II) conditions were performed, and maximum biomass and carbohydrate productivity were found as 0.088 and 0.423 g L−1 day−1 for L. limnetica. This is the first ever attempt to evaluate and optimize various parameters affecting the growth of cyanobacterial biomass of L. limnetica and O. obscura as well as their carbohydrate contents.

Growth of Cyanobacteria: Optimization for Increased Carbohydrate Content.

Biobutanol production from hydrolysates of cyanobacteria Lyngbya limnetica and Oscillatoria obscura

Biofuels will become competitive globally only when they can be delinked from food crops. All non-food feeds for bio-alcohols (bioethanol/biobutanol) production have the inherent difficulty of conversion from cellulose to simpler sugars that can be fermented into end products. The process currently being used to convert complex cellulosic feedstocks into sugars is costly; hence, the biofuels obtained through these routes are not economical. Enormous efforts are currently being made worldwide to convert second- and third-generation feedstocks into bioethanol/biobutanol, and several prominent global energy-producing companies are investing large sums of money to realize this dream. The complexity and cost of different stages of bio-alcohols production can be minimized with the application of different nanoparticles. A three-pronged approach is required to comprehend the economic production of bioethanol which begins with technology for better crop production, improved feedstock processing, and development of new biofuels such as biobutanol and renewable hydrocarbons. Various kinds of nanoparticles such as iron oxide, nickel cobaltite, zinc oxide and different nanocomposites, etc. have been used for production of biofuels. The present chapter deals with the present status on the application of nanoparticles in different stages of bio-alcohols (bioethanol/biobutanol) production. Involvement of these nanomaterials in different bioconversion processes provides a sustainable way by reducing the raw biomass processing as well as production costs and lowering down the harmful environmental impacts.

Deepika Kushwaha

Papers

Recent trends in biobutanol production

Growth of Cyanobacteria: Optimization for Increased Carbohydrate Content.

Biobutanol production from hydrolysates of cyanobacteria Lyngbya limnetica and Oscillatoria obscura

Nanotechnology in Bioethanol/Biobutanol Production

Co-fermentation of residual algal biomass and glucose under the influence of Fe3O4 nanoparticles to enhance biohydrogen production under dark mode