Article

Ultrasound-enhanced conversion of biomass to biofuels

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Abstract

Two important challenges need to be addressed to realize a practical biorefinery for the conversion of biomass to fuels and chemicals: (i) effective methods for the degradation and fractionation of lignocelluloses and (ii) efficient and robust chemical methods for the conversion of bio-feeds to target products via highly selective catalytic reactions. Ultrasonic energy promotes the pretreatment and conversion process through its special cavitational effects. In this review, recent progress and methods for combining and integrating sonication into biomass pretreatment and conversion for fuels and chemicals are critically assessed. Ultrasonic energy combined with proper solvents allows destruction of the recalcitrant lignocellulosic structure, fractionation of biomass components, and then assists many thermochemical and biochemical reactions, with increased equilibrium yields of sugars, bio-ethanol and gas products by 10–300%. Sonication promotes hydrolysis, esterification and transesterification in biodiesel synthesis and leads to reduced reaction time by 50–80%, lower reaction temperature, less amounts of solvent and catalyst than comparable unsonicated reaction systems. For algal biomass, sonication benefits the disruption, lysis and content release of macro and microalgae cells, and reduces the time required for subsequent extraction and chemical/biochemical reactions, with efficiencies typically being improved by 120–200%. High-frequency ultrasound of 1–3 MHz allows harvesting of microalgae, liquid product separation and in-situ process monitoring of biomass reactions, while high-intensity ultrasound at 20–50 kHz activates heterogeneous and enzymatic catalysis of the biomass reactions. The use of ultrasound in conversion of biomass to biofuels provides a positive process benefit.

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... Although ultrasound treatment does not completely remove lignin or hemicellulose from lignocellulosic materials, it markedly enhances the extraction and separation of these components by breaking down their structural barriers and weakening their bonds. Several studies have also reported enhanced yields of enzymatic hydrolysis following ultrasound pretreatment [18,25,26]. ...
... Due to its ability to breakdown lignin and hemicellulose, which are the outer structures of lignocellulose, the application of acid can be advantageous [31]. The combination of mild acid pretreatment and ultrasound can improve the accessibility of cellulose by disrupting the lignin-carbohydrate matrix and reducing the crystallinity of cellulose [25]. Using a mild acid concentration prevents excessive degradation of cellulose. ...
Article
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This study aims to obtain the optimum conditions of ultrasonication pretreatment using response surface methodology (RSM) with Box Behnken Design (BBD) as a first step before going to glucose production by enzymatic hydrolysis. The variables used in the ultrasonication optimization process include temperature (35–55 °C), time (25–65 min), and sulfuric acid concentration (0–1% v/v), with percent cellulose obtained as the response parameter. The optimum conditions for ultrasonication were at temperature of 45,3 °C, a time of 52 min, and an acid concentration of 1%. As a result, the relative cellulose content of oil palm empty fruit bunch (OPEFB) increased from 32.36 to 44.35%. It was found that ultrasound pretreatment can significantly reduce the extractive content of OPEFB. The use of diluted acid also reduces hemicellulose and loosens the bonds between lignin, which leads to an increase of glucose during the enzymatic hydrolysis process. Enzymatic hydrolysis using cellulase from Trichoderma reseii was then carried out, producing 26.5% of glucose yield which is 3 times higher compared to unpretreated (6.6% glucose yield) after 36 h. Examination by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscope (SEM) was able to reveal how the ultrasonic pretreatment affects the microscopic structure, chemical, and physical properties of the OPEFB leading to improvement of the enzymatic conversion to glucose.
... Regarding the physical effect, acoustic cavitation occurs when a sound wave propagates in a liquid medium, generating bubbles that grow and collapse violently in successive cycles of compression and rarefaction. A mechanical acoustic wave with frequencies between 10 kHz and 20 MHz transmits high energy to the reaction medium through cavitation and other associated effects [14]. This process breaks down the cell wall, reduces particle size, and enhances mass and heat transfer, intensifying the contact and separation of reactants, thus accelerating the reaction or altering its kinetics [3,14]. ...
... A mechanical acoustic wave with frequencies between 10 kHz and 20 MHz transmits high energy to the reaction medium through cavitation and other associated effects [14]. This process breaks down the cell wall, reduces particle size, and enhances mass and heat transfer, intensifying the contact and separation of reactants, thus accelerating the reaction or altering its kinetics [3,14]. Regarding the chemical effect, derived from the effect of acoustic cavitation, reactive free radicals are generated that promote the decomposition of biomass macromolecules under the influence of ultrasound; this causes rapid changes in temperature and pressure, together with turbulence and intense shear forces, producing morphological alterations. ...
Article
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Growing awareness of resource sustainability and waste management has driven the search for circular-economy solutions. Lignocellulosic biomass waste, the most abundant renewable carbon resource, offers green potential as an alternative to declining non-renewable fuels. However, due to its recalcitrant nature, it requires pre-processing to convert it into valuable products like energy and chemicals. Biorefineries play a key role in this process by promoting the integral use of biomass, by finding ways to utilize lignin, previously treated as waste. Common pretreatment methods are unsustainable, prompting research into eco-friendly solvents and advanced techniques like ultrasound- and microwave-assisted methods. Recent approaches have also explored the use of eutectic solvents, which, when combined with these intensification techniques, offer promising results. These green technologies improve delignification efficiency, which in turn improves the saccharification process, reduces solvent use, and minimizes environmental impact. Despite progress, challenges remain in making these methods economically viable and adaptable to diverse biomass types. This review article highlights recent advances in sustainable treatment technologies, including the combined use of eutectic solvents and process-intensification techniques, and the potential of the obtained lignin in various industrial applications. It also discusses future prospects for more environmentally friendly processes in biomass utilization.
... Several studies reported that high-energy EMR has emerged as a promising technology for pretreating lignocellulosic biomass to enhance the efficiency of enzymatic saccharification [112,127,128]. The effectiveness of a treatment method is influenced by various process factors, including temperature, radiation power, frequency, contact time, and liquid-to-solid ratio (LSR). ...
... However, the selectivity of the radiation system helps decrease the creation of inhibitors in the treatment matrix, thereby minimizing their impact on the enzymatic saccharification and fermentation processes. By utilizing statistical methods such as factorial design and multi-variable optimization, numerous researchers employ advanced technology to optimize a range of parameters for the radiation pretreatment process [61,128]. The most significant advantage of the radiation method is its simple operation and short processing time, its selectivity to degrade biomass components [63]. ...
Article
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The use of lignocellulosic biomass as a sustainable source for bio-based products has gained significant attention in recent years. However, the recalcitrant nature of lignocellulose biomass poses challenges in its conversion to valuable products. Pretreatment methods have been developed to enhance the accessibility of cellulose and hemicellulose, thereby improving the enzymatic hydrolysis efficiency. Pretreatment of lignocellulosic biomass can be done using various physical, chemical, biological, and combinations of these methods. Electromagnetic radiation (EMR) is one of the physical pretreatment methods, which includes microwave radiation, gamma radiation, and electron beam radiation. The purpose of this review is to explore the recent scientific discoveries and advancements, potential uses, challenges in scaling up, and the outlook for using EMR as a pretreatment method in valorizing lignocellulosic biomass. It offers several advantages, such as minimizing energy consumption, shorter processing times, ease of operation, improving selectivity, sustainability, and eco-friendliness. A brief discussion was made about the effects of EMR on lignocellulosic biomass based on the literature. This included changes in structure, lignin degradation, cellulose crystallinity, and hemicellulose solubilization. Furthermore, we highlight the influence of process parameters such as radiation power, radiation dose rate, liquid-to-solid ratio, frequency, and contact time on pretreatment efficiency. The evaluation also provides an overview of the challenges and future perspectives of the EMR method. Furthermore, environmental sustainability as a green technology is addressed, including the potential of noxious chemical reduction and waste generation minimization.
... Ультразвуковой (УЗ) кавитационное воздействие является одним из наиболее перспективных способов ускорения химических реакций [1][2][3]. Применение ультразвука не только повышает скорость химической реакции, но и, в отличие от традиционных методов, увеличивает процент прореагировавших веществ при равном времени реакции. При ультразвуковом кавитационном воздействии жидкой среды, можно получить химические реакции, которые в других случаях получить невозможно. ...
... Однако все экспериментальные результаты были получены только для отдельных пар веществ жидкость-жидкость [1][2][3] и, как правило, существует зависимость скорости химической реакции от интенсивности колебаний. При этом нет зависимостей от частоты колебаний, так как ввиду резонансных свойств ультразвуковых рабочих инструментов для работы на другой частоте необходимо новое ультразвуковое устройство. ...
Article
В статье представлена феноменологическая модель кавитационной интенсификации химических реакций в высокоинтенсивном ультразвуковом поле. В основе предложенной модели лежит статистический подход, который заключается в оценке константы скорости химической реакции, усредненной по объему. Усреднение проводится по объему, который намного больше, чем объем кавитационного пузырька, в котором микроскопическое значение постоянной зависит от ударного волнового давления при коллапсе кавитационных пузырьков. Константа скорости химической реакции зависит от давления и рассчитывается с использованием распределения скоростей молекул Максвелла и вероятности события, что энергия молекулы больше энергии активации для данной реакции. Численный анализ модели показал, что ультразвуковое воздействие повышает эффективность химических реакций в 1,5 раза. The paper is devoted to proposed phenomenological model of cavitation intensification of chemical reactions in high-intensity ultrasonic field. The model is based statistical approach which is evaluation of volume-averaged chemical reaction rate constant. Averaging is performed over volume that is much more than cavitation bubble volume in which the microscopic value of constant depends on shock wave pressure at cavitation bubbles collapse. The chemical reaction constant dependency on pressure is calculated by using Maxwell distribution of molecules velocities and probability of event that the molecule energy is more than activation energy for given reaction. The numerical analysis of model shown that ultrasonic influence increase of chemical reaction efficiency up to 1.5 times.
... The reaction times of these new, environmentally friendly technologies must be sped up while still producing biodiesel of high calibre. In order to do this, a variety of techniques have lately been investigated, including microwave (Changmai et al., 2019;Das, Shi, Halder, & Lalthazuala Rokhum, 2022;Motasemi & Ani, 2012;Soltani, Rashid, Yunus, & Taufiq-Yap, 2015), membrane (Shuit, Ong, Lee, Subhash, & Tan, 2012), ultrasonic (Badday et al., 2012;Luo, Fang, & Smith, 2014;Rajkumari et al., 2021), hydrodynamic cavitation (Chuah, Yusup, Abd Aziz, Bokhari, & Abdullah, 2016), plasma discharge (Troter, Todorović, Dokić-Stojanović, Stamenković, & Veljković, 2016), reactive distillation, cosolvent, rotatory, supercritical methods (Tan & Lee, 2011), and plug flow reactors (Buchori, Istadi, & Purwanto, 2016) for the generation of biodiesel (Laskar et al., 2018). ...
... This reaction mechanism depends on the flow of sonochemical radiations produced by sound waves as well as the acoustic energy they offer. Through the use of piezoelectric transducers, electric energy in ultrasonic radiation is converted to mechanical energy, which is subsequently converted into chemical change (Asakura, Nishida, Matsuoka, & Koda, 2008;Luo et al., 2014). The transesterification and esterification reactions can be greatly enhanced for creating highquality biodiesel at a low cost and in a significantly shorter amount of time by providing ultrasonic energy with other reaction processes. ...
Chapter
The search for alternate energy sources has intensified due to growing concerns. These worries include the availability of feed�stock in relation to supply security and the utilisation of domes�tic energy sources, volatility of cost, the ongoing depletion of non-renewable petroleum reserves, and greenhouse gas emis�sions. It is beyond the scope of this chapter to list all of the legal, regulatory, and incentive measures implemented to address these concerns. The importance of fuels generated from biological sources, including lipid substances like fats and oils, has grown. Fuels produced through various production methods employing fats and oils as feedstocks have varying compositions and physi�cal characteristics. Biodiesel is the most well-known of these fuels
... Ultrasound pretreatment is a rapid technique that can reduce the hydrolysis time by up to 80%, thereby enhancing the overall efficacy of the bioconversion process [80]. When ultrasonic waves penetrate low-pressure regions, they generate tiny gas or vapor bubbles. ...
Article
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The growing global population is driving up energy demand. The continued reliance on conventional energy sources is contributing to global warming and significant emissions of harmful gases. Conventional energy sources, such as coal, crude oil, and natural gas, commonly used in petrochemical processes, must be replaced with sustainable alternatives. One of the most popular and affordable sources for producing renewable energy and chemicals is lignocellulosic biomass (LCB). Lignocellulosic biomass, which includes agricultural waste, energy crops, and forest residues, is readily available, cost-effective, and provides a sustainable feedstock for bio-based energy and chemical production. To break down the natural structure of lignocellulosic biomass and facilitate the separation of its components for various applications, pretreatment is essential. Conventional pretreatment methods, however, have significant drawbacks; they tend to be toxic, environmentally polluting, and expensive compared to non-conventional approaches. To address these issues, we must shift toward less harmful, eco-friendly strategies. Techniques such as microwave, ultrasound, irradiation, hydrodynamics, and pulsed electric fields are promising alternatives, generating fewer toxic by-products and being more environmentally friendly. This paper explores the benefits, limitations, and mechanisms of specific non-conventional pretreatment methods, as well as the role of lignocellulosic biomass in biomass valorization and the circular economy.
... Перспективным подходом к решению проблемы повышения эффективности получения биоэтанола из целлюлозы являются ультразвуковые (УЗ) колебания [1][2]. ...
Article
Аннотация - В работе представлена модель механоактивации молекул при получении биоэтанола из микропорошковой целлюлозы под действием ультразвуковой кавитации. Рассматривается процесс ферментативного гидролиза в системе «жидкость-твёрдое тело», ускоряемого ультразвуковой кавитацией. Модель впервые учитывает размер кавитационной зоны и зависимость размера зоны от частоты. В конечном итоге это позволяет определить оптимальные режимы, обеспечивающие максимальную скорость получения биоэтанола из микропорошковой целлюлозы. Abstract-the paper presents a model of mechanoactivation of molecules in the production of bioethanol from micro-powder cellulose under the action of ultrasonic cavitation. The process of enzymatic hydrolysis in the system "liquid-solid" accelerated by ultrasonic cavitation is considered. The model for the first time takes into account the size of the cavitation zone and the dependence of the zone size on frequency. In the end, this allows you to define the modes, providing the maximum speed of bioethanol from cellulose microporosity.
... Billion tonnes of lignocellulosic biomass wastes are produced annually, which are mostly disposed off by burning or dumped in landfills. Nonetheless, this growing quantity might function as a cheap source of cellulose, with possible applications [3,4]. For every ton of palm oil produced, 220 kg of oil palm mesocarp fibres are generated. ...
Article
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Natural cellulose-based microfibers were obtained through an economical and environmentally sustainable process called alkaline-peroxide purification, from the waste products of oil palm mesocarp fibres (OPMF) and pineapple leaves (PL), with the intention of creating porous, biodegradable, biocompatible, and non-toxic solid supports for use in future processes. The extracted microfibres were then taken through microscopic, spectroscopic and thermal characterisation to establish their cellulosic nature. The scanning electron microscopic (SEM) images of the bleached microfibres (B-OPMF and B-PLF) were cleaner, smoother and porous as compared with that of the unrefined fibres (Ur-OPMF and Ur-PLF). The bleached fibres (B-OPMF and B-PLF) exhibited peaks of C and O, which are indicative of pure cellulose, in the energy-dispersive X-ray spectroscopy (EDS) analysis. The FTIR spectral analysis of the extracted cellulose-based fibres (B-OPMF and B-PLF) exhibited peaks that were similar in composition to the reference cellulose (P-GB). For the thermogravimetric analysis (TGA) analysis, the maximum weight degradation in the reference cellulose (P-GB), occurred at 363.11 °C, in the bleached palm fibres (B-OPMF) at 334.55 °C and in the bleached pineapple leaf fibres (B-PLF) at 375.68 °C which, corresponds to cellulose decomposition. The differential scanning calorimetry (DSC) test verified the microfibers' thermally induced transitions. Therefore, these cellulose-based microfibres could be applied as functionalised microfibre supports for future applications.
... The collapse also releases significant energy in localized hot spots (Suslick, 1994;Ranade et al., 2022) and produces physical effects that are not otherwise achievable in conventional processes. The micro-flow of liquid filling the cavity after the implosion generates strong jets and shear forces, that significantly improve mixing and transport properties in the liquid phase (Bundhoo and Mohee, 2018;Parvizian et al., 2011;Tang and Sivakumar, 2014;Luo et al., 2014;Rahimi et al., 2013). The jets may induce mechanical fragmentation of the solid, which is a key advantage when cavitation is applied to the leaching process, as it increases the surface area exposed to the leaching agent (Zeiger and Suslick, 2011;Sander et al., 2014;Jordens et al., 2016). ...
Article
Along with the transition to cleaner energy production methods, closing the processing loop on batteries is becoming one of the significant issues to tackle in this decade. The most promising recycling technique consists in the leaching of crushed cathode material, i.e. the dissolution of the solid battery material in an acid solution, to recover valuable metals from spent batteries. To lower process time and to use green organic solvents, ultrasonically enhanced leaching is a valid alternative to conventional processing. The mechanism of action of ultrasound during leaching is still unclear, and yet to be directly observed on solid particles. Therefore, this work aims to shed light on the underlying phenomena in the ultrasonically enhanced leaching process, by directly observing leached material. In particular, the focus is placed on the combined effect of ultrasound and acetic acid on NMC particles. Residual material from conventional and ultrasonically enhanced leaching was analyzed with inductively coupled plasma - optical emission spectrometry (ICP-OES), dynamic light scattering (DLS) and scanning electron microscopy (SEM). Conventional and ultrasonically enhanced leaching techniques were thus compared in terms of leaching efficiency, particle size distribution and morphological changes, demonstrating the beneficial effect of ultrasonic cavitation on mass transfer. Additionally, the NMC particles were exposed to ultrasound in water, to confirm that standalone ultrasonic cavitation does not lead to particles breakage. The understanding of the effect of ultrasound enables their targeted application in leaching processes and allows a deeper understanding of ultrasound in heterogeneous systems.
... Indeed, the use of ultrasonic extraction in black tea increases polyphenolic content by + 15 % compared to maceration (Both et al., 2014). Ultrasound has been used at a pilot scale for biofuel production Chemat et al., 2017;Flores et al., 2021;Luo et al., 2014). ...
Article
Lignocellulosic biomass has a promising role in a circular bioeconomy and may be used to produce valuable molecules for green chemistry. Lignocellulosic biomass, such as food waste, agricultural waste, wood, paper or cardboard, corresponded to 15.7% of all waste produced in Europe in 2020, and has a high potential as a secondary raw material for industrial processes. This review first presents industrial lignocellulosic waste sources, in terms of their composition, quantities and types of lignocellulosic residues. Secondly, the possible high added-value chemicals obtained from transformation of lignocellulosic waste are detailed, as well as their potential for applications in the food industry, biomedical, energy or chemistry sectors, including as sources of poly-phenols, enzymes, bioplastic precursors or biofuels. In a third part, various available transformation treatments, such as physical treatments with ultrasound or heat, chemical treatments with acids or bases, and biological treatments with enzymes or microorganisms, are presented. The last part discusses the perspectives of the use of lignocellulosic waste and the fact that decreasing the cost of transformation is one of the major issues for improving the use of lignocellulosic biomass in a circular economy and green chemistry approach, since it is currently often more expensive than petroleum-based counterparts.
... Although sonocatalysis offers several advantages for biomass processing, but some drawbacks need to be addressed. Firstly, the cost of implementing sonocatalysis can be high due to the need for specialized equipment, including ultrasonic generators and reactors [10,50,[64][65][66][67]. Secondly, the degradation and conversion of lignocellulosic biomass and its derivatives through sonocatalysis can be affected by heterogeneity [29]. ...
... This leads to a powerful vibration that releases energy. The energy from the sound waves transforms into heat, enhancing the contact and disengagement of heterogeneous reactants [51]. A report by Gadhe et al. [52] mentioned that the pretreatment of complex food waste via ultrasonication enhanced the production of hydrogen by two times compared to unsonicated food waste. ...
Article
Full-text available
The increasing global population has led to a significant accumulation of food waste. It is important to focus on reducing food waste instead of disposal methods like landfilling and incineration, which have severe environmental impacts. Upcycling food waste has emerged as an effective strategy for repurposing discarded food into higher-value products. However, concerns about food safety and public acceptance of products directly produced from food waste persist. Consequently, there is growing interest in utilizing food waste rich in moisture and biodegradable organic compounds as a potential medium for cultivating microalgae. This review article examines the utilization of food waste as a culture medium for microalgae cultivation and the methods for treating food waste to enhance its nutrient content. Additionally, it discusses the influence of nutrients such as carbon, nitrogen, and phosphorus on microalgae growth and external factors such as pH and light intensity. The article also addresses the innovation of the food supply chain from environmental, social, and economic perspective, along with food safety and public acceptability concerns. Furthermore, it explores the legislative issues surrounding products derived from food waste and the end use of microalgae biomass produced from food waste. Overall, this review provides insight into the potential of microalgae cultivation using food waste, serving as a platform towards the realization of a circular bioeconomy.
... This may be because BEW has a high REDOX potential, which can protect proteins from oxidation caused by free radicals (Li et al 2022), protect S. platensis protein, and effectively prevent bacterial and enzymatic degradation of food(Li et al 2021), increasing enzyme activity. US produces an acoustic cavity effect in the solvent, increases the surface contact area between the solid and liquid phases, and thus enables the solute to spread from the solid phase to the solvent more quickly (Hossain et al 2012), plays a role in assisting cell fragmentation and reducing the size of S. platensis particles, and improves the efficiency of protein and peptide extraction after cell lysis (Luo et al 2014). Ultrasound-assisted extraction is an environmentally friendly extraction method suitable for lab-scale extraction of S. platensiss peptides (Vernes et al 2019). ...
Preprint
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In this study, four kinds of Spirulina platensis ( S. platensis) peptides were obtained by enzymolysis of protein after different pretreatment to S. platensis powders. The novel coronavirus main protease (SARS-CoV-2 main protease, Mpro) was successfully prepared by heterologous expression in E. coli and its activity was detected. After identification of S. platensis peptides sequences, highly active peptides were synthesized and their inhibition effects on Mpro was verified. Subsequnently, the mechanism of action between them were analyzed by computer simulations. Results showed that the extraction rate of the protein from S. platensis was 96.11%, the activity of Mpro was 845.90 U mg ⁻¹ , the peptide MQGPNY could inhibit the activity of Mpro with the inhibition rate of 20.21%±3.8% at the concentration of 2 mM. Fuerthermore, results from computer Simulation showed that the peptide MQGPNY forms four pairs of hydrogen bonds with Mpro, which are Gln189, Ser46, Thr26 and Glu166. In addition, there were nine free residues involved in hydrophobic contacts, which were His164, His41, Thr24, Met49, Thr45, Thr25, Gly143, Asn142, and Cys145 and Met165. This study developed natural peptides from S. platensis , which could inhibited the activity of Mpro. Besides, the mechanism of the peptide MQGPN acting on Mpro was revealed by the method of computer Simulation. The foundings could provide theoretical support for the use of protein and its hydrolysates from S. platensis in functional food and supplement formulations in the post-epidemic era.
... Despite their suitability for certain applications, they suffer from low cavitation efficiency and a lack of consistent distribution of acoustic intensity, as discussed in this chapter. Consequently, it is often necessary to complement this process with mechanical agitation [49]. ...
Chapter
The production of biofuels has a great impact on the economy and society. Biodiesel is a sustainable liquid fuel used for partial or full replacement of standard diesel fuel, and its production generates valuable by-products. The use of ultrasound in biodiesel production has a growing interest due to several advantages; it significantly reduces the reaction time and avoids the use of heating, reaching similar or higher FAME yield. The application of ultrasounds in homogeneous and heterogeneous catalysis processes is reported to be technically feasible, but several issues are to be considered such as the corrosion effect on sonotrodes, and the effect of ultrasounds waves on solid catalyst surface and pores. Combining it with microwave irradiation might be an effective procedure for the intensification of biodiesel production, especially with heterogeneous catalysis. Technical challenges are associated with the design of large-scale reactors in which both types of energy could be applied concurrently with cost reduction. This chapter explores the basis of ultrasounds and their use in the production of biodiesel, its main features, and challenges.
... The most important challenge is the heterogeneity of biomass that leads to a low thermal conductivity that generates a barrier for heat and mass transfer. Conversion and selectivity in biomass transformation tend to be weak due to deficient catalyst-reactant interactions [10]. One of the most challenging aspects involves the extraction of lignin from lignocellulosic biomass, given its complex nature as a phenolic polymer. ...
Article
Full-text available
As a renewable and sustainable resource, lignocellulosic biomass serves as a crucial raw material for the production of biofuels, biochemicals, and various value-added products. This paper aims to develop and optimize a mild alkaline treatment of sawdust assisted by ultrasound, along with enzymatic hydrolysis of the pretreated material. The alkaline sonochemical pretreatment emerged as the optimal approach to enhance the susceptibility of cellulose to subsequent enzymatic hydrolysis to improve the yield of reducing sugars. A comparative study was performed using various ultrasonic applicators (horn and bath) and conventional assisted alkaline pretreatment. The ultrasonic-assisted pretreatment revealed a higher delignification of 68% (horn) and 57% (bath) compared with conventional pretreatment. Processes were optimized using a statistical analysis based on a 23 factorial design. The ratios between sawdust and alkaline solution (RSL = 0.5–1.5 g/100 mL), US amplitude (A = 20–60%), and working temperature (t = 30–50 °C) were selected as process factors. The optimal operating conditions to maximize the reducing sugar yield (138.15 mg GE/gsubstrate) were found as follows: a solid/liquid ratio of RSL,opt = 1.25 g/100 mL, US amplitude of Aopt = 60%, and pretreatment temperature of topt = 50 °C. The overall outcomes clearly confirmed the intensification of delignification by ultrasound-assisted alkaline pretreatment.
... KR-1 showed only 27.4% hydrolyzed sugars (Lee et al., 2015), and Chlorella homosphaera (both unpretreated biomass) exhibited 47% of total glucose in biomass (Rodrigues et al., 2015), highlighting the importance of pretreatment. Moreover, research efforts are currently focused on optimizing parameters to identify the most energy-efficient pretreatment method for algal materials (Luo et al., 2014). ...
... The most important challenge is the heterogeneity of biomass that lead to a low thermal conductivity that generates a barrier for heat and mass transfer. Conversion and selectivity in biomass transformation tend to be weak due to deficient catalyst-reactant interaction [10]. One of the most challenging aspects involves the extraction of lignin from lignocellulosic biomass, given its complex nature as a phenolic polymer. ...
Preprint
Full-text available
Lignocellulosic biomass, an abundant and renewable resource, serves as a crucial raw material for the production of biofuels, biochemicals, and various value-added products. This paper aims to develop and optimize a mild alkaline treatment of sawdust assisted by ultrasound, along with enzymatic hydrolysis of the pretreated material. The sonochemical pretreatment with alkali emerged as the optimal approach to enhance the susceptibility of cellulose to subsequent enzymatic hydrolysis, thereby increasing the yield of reducing sugars. A comparative study was performed using various ultrasonic applicators (horn and bath) and conventional assisted alkaline pretreatment. The ultrasonic assisted pretreatment revealed a higher delignification as 68% (horn) and 57% (bath) comparing with conventional pretreatment. Processes were optimized using a statistical analysis based on a 23 factorial design. The ratio between sawdust and alkanine solution (RSL = 0.5–1.5 g/100 mL), US amplitude (A = 20–60%), and working temperature (t = 30–50 °C) were selected as process factors. The optimal operating conditions to maximize the reducing sugar yield (138.15 mg GE /gsubstrate) were found as following: solid/liquid ratio RSL,opt = 1.25 g/100 mL, US amplitude Aopt = 60%, and and pretreatment temperature topt = 50 °C. The overall outcomes clearly confirmed the intensification of delignification by ultrasound assisted alkaline pretreatment
... When ultrasounds evolve in water, bubbles (4-300 μm diameter) are instantly created and collapse just after nanoseconds: It is cavitation. The forced-out air releases locally an extremely high pressure up to 50 MPa and temperatures up to 5000 °C (Fig. 3) [70]. Ultrasound pretreatment is based on the effect of cavitation on the submerged biomass. ...
Article
Full-text available
Lignocellulosic biomasses, mainly forestry and agricultural residues, are inexpensive, available and attractive to reduce the dependence of the world on fossil fuels. However, before their processing in biorefineries, they must undergo a pre-treatment to allow access to the desired compounds of interest (cellulose, hemicellulose, or lignin). However, the pretreatment step significantly reduces and affects the profitability of the biorefinery process. Several pretreatment technologies have been developed so far. However, taken individually, these methods do not make lignocellulosic biomass a fully cost-effective input for biorefineries, hence the current trend to combine technologies. Extrusion is currently one of the most attractive technologies. It is relatively new and has been combined with many other methods to pretreat various types of biomasses with interesting benefits and results. This article provides a critical review of pretreatment combinations involving extrusion and discusses the challenges, solutions, and R&D needs for these combinations.
... Via compression and rarefaction, ultrasonic waves with a minimum frequency of 16 kHz propagate, causing a large number of microscopic cavities to form, the generation of free radicals, the dispersal of chemical layers, and an acceleration of the reaction's ingredient contact [33]. Because emulsification is encouraged and mass heat transfer in two-phase systems is amplified, ultrasonic effects are typically far stronger in heterogeneous chemical systems than in homogeneous ones [34]. These effects have been used in biological, environmental, and agricultural chemistry to prepare samples [35]. ...
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Fruit juices are produced in home or industrially from horticultural crops by pressing the liquid part. They are rich in sugar, vitamins, and minerals like iron, copper, potassium, folate minerals, and vitamins A, B, and C which are essential for giving the body the nutrients it needs to stay healthy since fruits contain vital mineral components like copper (Cu), iron (Fe), and manganese (Mn), which is necessary for human growth and respiration. However, they may have heavy metals which may poison health risk and toxic even the presence is in little amount. Since fruit juices doesn’t pass through different processes, except extracting the liquid from the fruits of vegetables contamination and heavy metals affect human health. Before determination of heavy metals different procedures are applied for analysis. Digestion is the key component for determination of heavy metals from different samples. In this paper we are concerned on wet digestion methods for analysis. Closed system wet digestion is preferred since it lower the risk of contamination. There are different wet digestion types. Some of them are conventional wet digestion, ultraviolet digestion, ultrasound-assisted acid decomposition, conventional heating, microwave-assisted wet digestion etc. From thus, microwave digestion procedure was preferred for the digestion of samples for determination of heavy metals due to its ability to oxidize almost all of the organic samples.
... In summary, immersion of surfactant in slurry before the enzymatic hydrolysis can increase delignification. The decreased surface tension of the surfactant will increase lignin removal and crystalline cellulose deconstruction (Luo et al. 2014). Zhang et al. (2020) employed varying concentrations of NaOH (ranging from 0% to 10%). ...
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Alkaline pretreatment stands out as a valuable strategy in biomass conversion to overcome the recalcitrance of biomass by removing lignin and a part of hemicellulose. This enhances enzyme accessibility and promotes saccharification. However, increasing the alkaline concentration to enhance the delignification and improve glucose yield together presents inherent limitations. In this experiment the amount of delignification and glucose yield resulting from surfactant associated with sonication during mild alkaline pretreatment of Eucalyptus pellita was investigated. Also, the effect of various factors (sonication temperature and surfactant immersion time) on delignification and glucose yield were examined. The results demonstrated that surfactant associated with sonication pretreatment could overcome the limitation of alkaline pretreatment and could increase the amount of delignification alongside enzymatic hydrolysis glucose yield of Eucalyptus pellita wood by around 90%. The findings indicated that surfactant-assisted with sonication during mild alkaline pretreatment of Eucalyptus pellita (i.e., hardwood) could be recommended as a supporting pretreatment method for the production of monomeric sugars.
... The creation of oxidizing radicals of H + and OHcaused by the dissolution concerning molecules of water is attributed to the high frequency provided by acoustic oscillations. These highly active radicals disrupt the complex structure of glycosidic connections found in LCB [179]. ...
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The mounting concerns regarding the depletion of fossil fuel resources and the environmental consequences linked to greenhouse gas emissions have propelled scientific investigations toward sustainable alternatives. Lignocellulosic biomass (LCB) has prominently emerged as a promising feedstock for the development of fourth-generation biofuels and a range of value-added bioproducts. This comprehensive review is dedicated to exploring recent advancements in this dynamic field, elucidating innovative strategies aimed at efficiently converting the intricate structure of lignocellulose into fourth-generation biofuels and various value-added bioproducts. Additionally , it provides a detailed explanation of the extraction and utilization of organic acids and solvents derived from LCB. Moreover, this study also addresses the generation of biodegradable hydrogels and other materials for drug delivery. Furthermore, the review sheds light on the current landscape of opportunities and challenges surrounding lignocellulosic-based biorefineries. By critically assessing the potential of this emerging field, it offers insights into the path ahead. The convergence of innovative research, sustainable practices, and industrial scalability holds the potential to reshape the bioenergy and bioproducts sector, fostering a more sustainable and resilient future.
... The local hotspots may cause the formation of radical species [4], such as hydroxyl radicals when water is sonicated [5]. The collapse of these bubbles also produces micro-jets and wakes, that generate strong shear forces [6][7][8][9][10]. In recent years, UIC has been extensively applied to the production of food and beverages [11,12], drug delivery [13,14], water treatment [15,16], and to processing of hydrocarbon mixtures, both fossil [17,18] or bio-derived [6]. ...
... The physical effect is regarded as the formation of strong microturbulence in a reaction system through convective forces by creating a transient bubble motion induced by the passage of ultrasonic waves (Ong and Wu 2020;Jeon et al. 2015). While, the latter effect is in terms of thermal dissociation of entrapped vapor molecules inside the bubbles during transient collapse, which promotes to the development of highly reactive radicals include · OH, · O, and HO 2 · (Hart and Henglein 1985;Luo et al. 2014). The generated radical species involves in the chemical reaction that causes lignin degradation efficiently (Nakashima et al. 2016). ...
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Microalgae are a great source of feedstock for the formulation of new products and the choice of extraction solvent is essential for the development of new extraction technologies for algal product recovery. Strong impulses for the industry established the search for new extraction processes with solvents considered green for the environment. In this sense, the use of microalgae-based molecules is drawing attention to a sustainable perspective and an attractive alternative to minimize environmental impacts. Appropriately, this chapter presents the extraction processes of microalgae compounds, the main extraction solvents, and the main compounds that can be obtained from them. The process of extraction of microalgae-based molecules shows to be a scientifically promising field, where there are still gaps to be evaluated. In addition, this chapter explores key results that can be achieved on a laboratory scale and how these results can be achieved on an industrial scale. Future perspectives and a promising overview on the subject are provided.
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Biofuels are a straightforward strategy for replacing fossil fuels, and lignocellulosic biomass contributes to this process. The chemical structure of the lignocellulosic matrix is quite recalcitrant, imposing a previous pretreatment to enable biomass into biofuels and chemicals. However, this process has been perceived as one of the most expensive steps in biomass-to-biofuel conversion. This chapter relates lignocellulosic residues from the industrial processing of agricultural products such as agave, corn, palm and sugarcane, which are highly important for the energetic context. The intention is to discuss ways of pretreatment of these materials to get the necessary biofuels. Thus, different methods (physical, chemical and physicochemical) are covered in this chapter, describing their physical and chemical effects on biomass structure. Emerging pretreatments will also be discussed as promising eco-friendly and low-cost techniques.
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Chapter
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Currently, in the context of biorefinery and bioeconomy, lignocellulosic biomass is increasingly used to produce biofuels, biochemicals and other value-added products. Microwaves and ultrasound are emerging techniques that enable efficient and environmentally sustainable routes in the transformation of lignocellulosic biomass. This review presents some of the most important works published in the last few years on the application of microwaves and/or ultrasound in lignocellulosic materials pretreatment and can be used as a starting point for research into this theme. This review is divided into four parts. In Part I, the theoretical fundamentals of microwave and ultrasound treatments are reviewed. Dielectric constants for biomass, factors that influence pretreatment, are some of the subjects addressed. In Part II, the effects that these techniques have on lignocellulosic biomass (on the size and surface area of the particle; on the content of lignin, hemicellulose and cellulose; on the crystallinity index of cellulose; on the effect of solubilization of organic matter; on hydrolysis and reduction of sugars) are discussed. In Part III, emphasis is given to the contribution of microwaves and ultrasound in obtaining value-added products. In this context, several examples of liquefaction and extraction procedures are presented. Part IV describes examples of performing sonocatalysis on lignocellulosic biomass to obtain value-added products, such as furfural, whose production is significantly reduced by ultrasound treatment.
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Ultrasonic irradiation with organic solvents and alkaline extractions were carried out on a fast-growing poplar wood, triploid of Populus tomentosa Carr., in an attempt to develop efficient lignin isolation procedures. Four organosolv and three alkaline lignin fractions were successively isolated and comparatively characterized by sugar analysis, alkaline nitrobenzene oxidation, gel permeation chromatography (GPC), Fourier transform infra-red spectroscopy (FT-IR), quantitative 13C, and 2D HSQC nuclear magnetic resonance (NMR) spectroscopy, as well as thermogravimetric analysis (TGA). The results showed that the ultrasonic treatments and sequential extractions with three different concentrations of NaOH led to a release of 90.9% of the original lignin. The four organosolv lignin preparations obtained under the ultrasound-assisted extractions were degraded significantly and contained more carbohydrate and non-condensed syringyl units when compared to the three alkaline lignin preparations. Furthermore, the analyses confirmed that L 5, the lignin preparation with the highest yield (44.6% of the original lignin), was partially acylated at the γ-carbon of the side-chain preferentially over syringyl units. The percentage of lignin acylation of β-O-4' linkages was about 14%. The amount of β-O-4', β-β', and -OCH 3 were estimated to be about 0.31/Ar, 0.06/Ar, and 1.73/Ar, respectively. The ratio of S/G was calculated to be 2.0.
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The solubility of lignin from bagasse in a 1,4-butanediol/water mixed solution was investigated and explained by the solubility parameter (δ-value). To explore the lignin solubility, enzymatic hydrolysis/mild acidolysis lignin (EMAL) isolated from bagasse was used as the starting material to prepare lignin solution by ultrasonic treatment. The lignin content in solution was determined by UV-vis spectroscopy at a wavelength of 280 nm. The results showed that 240 minutes of ultrasonic treatment was needed to achieve lignin dissolution equilibrium in the 1,4-butanediol/water mixture. Maximum lignin solubility (14.6 g/L) occurred at a concentration of 80% (v/v). The δ-value of lignin (14.0 (cal/cm 3) 1/2) was calculated based on the atomic and functional groups present in the phenylpropane unit. The δ-values of the 1,4-butanediol/water showed a decrease from 22.31 to 11.09 (cal/cm 3) 1/2 as the concentration of 1,4-butanediol increased. The maximum lignin solubility predicted by the δ-value should occur at a concentration of 80% (v/v), which agreed with the experimental result.
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The paper reports the enhanced effect of multi-frequency ultrasonic irradiation on cavitation yield. The cavitation yield is characterized by electrical conductivity determination, fluorescence intensity determination and iodine release method. Two-frequency (28 kHz/0.87 MHz) orthogonal continuous ultrasound, two-frequency (28 kHz/0.87 MHz) orthogonal pulse ultrasound and three-frequency (28 kHz/1.0 MHz/1.87 MHz) orthogonal continuous ultrasound have been used. It has been found that the combined irradiation of two or more frequencies of ultrasound can produce a significant increase in cavitation yield compared with single frequency irradiation. The possible mechanisms of the enhanced effect are briefly discussed.
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In the present study, we report on an optimized method for fatty acid methyl esters (FAME) production from castor and jatropha seeds. In order to identify the most effective biodiesel production method, we have compared three two-stage methods, each consisting of oil extraction (the first step) and FAME production by transesterification (the second step), with the same three techniques each conducted in one stage, i.e., direct transesterification. The three techniques are conventional heating, sonochemistry, and microwave radiation. The FAME product was analyzed by 1H NMR spectroscopy and GC-MS. The SrO catalyst was reused successfully, together with seeds containing oil residues, for 10 cycles. The highest yield of FAME, 57.2 % of the total weight of the castor seeds, and a conversion of castor oil to FAME of 99.95 % were achieved in a one-stage method lasting 5 min using microwave radiation as a heat source. Using jatropha seeds leads to a yield of 41.1 % and a 99.7 % conversion of triglyceride to FAME under microwave irradiation in a one-stage method. The direct transesterification by sonication resulted in yields of 48.2 % and 32.9 %, and a 93.6 % conversion from castor and jatropha seeds, respectively.
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Factors affecting intracellular lipid extraction from marine microalgae were investigated using various techniques. The biomass drying method and moisture content, and the solvent extraction system were the factors studied. Lipid was analytically classified into three categories i.e. neutral lipid, free fatty acid (FFA) and polar lipid using solid-phase extraction. Biomass drying methods (freeze-, oven- and solar drying) did not affect lipid yield, but the FFA content of the lipid was three times higher for solar dried biomass. Of the various lipid extraction methods tested, including sonication, homogenization, accelerated solvent extraction (ASE) and Soxhlet extraction, sonication was the least efficient compared to other methods when a partially miscible solvent system i.e. hexane–methanol was used. Chloroform–methanol solvent system had maximum lipid extraction efficiency (33%). A biomass moisture content up to 5% had no impact on lipid extraction efficiency, but higher moisture contents reduced lipid extraction and increased the FFA fraction.
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Aqueous suspensions of dispersed Glaucocystis cellulose microfibrils were sonicated at 4 °C for 3 h, using 24 kHz ultrasonic waves. This treatment induced a variety of ultrastructural defects, as the microfibrils became not only shortened, but also presented substantial damage materialized by kinks and subfibrillation. Upon analysis by X-ray diffraction and 13C solid-state NMR spectroscopy, it was found that the initial sample that contained 90 % of cellulose Iα allomorph became, to a large extent, unexpectedly converted into the Iβ phase, while the loss of crystallinity was only moderate during the sonication treatment.
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Biodiesel, which consists of long-chain fatty acid methyl esters (FAME) obtained from renewable lipids such as those in vegetable oils or animal fat can be used as both an alternative fuel and an additive for petroleum diesel. This book gathers research from across the globe in the study of biodiesel blends, properties and applications. Topics discussed include biodiesel purification methods; exhaust emissions study of biodiesel operated garbage trucks; the heterogeneous catalyst for the transesterification of triglycerides into biodiesel; valorization of wastes and by-products derived from biodiesel manufacturing and biodiesel production using cation-exchange resin as heterogeneous acid catalyst. (https://novapublishers.com/shop/biodiesel-blends-properties-and-applications/)
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This article addresses the biochemical methane potential (BMP) production from anaerobic digestion of corn-ethanol coproducts including dried distiller grain with solubles (DDGS), distiller's wet grains (DWG), thin stillage, and condensed distiller's solubles (CDS) as well as evaluating the effects of ultrasonic pretreatment on methane production from these feedstocks. Ultrasonic pretreatment was applied with three amplitude settings of 33% (52.8 μm pp), 66% (105.6 μm pp), and 100% (160 μm pp) as well as five time settings (10, 20, 30, 40, and 50 s) to each of the four coproducts prior to conducting benchtop BMP trials. Ultrasonic pretreatment reduced mean particle size of DDGS and DWG by 45% and 43%, respectively. Without ultrasound pretreatment, CDS had the highest methane production potential (407 mL g -1 VS added) compared to the other coproducts. Ultrasonic pretreatment of DWG co-products (DDGS and DWG) resulted in greater increases in methane production than on liquid coproducts (CDS and thin stillage). Methane yields were increased by 25% and 12% for the ultrasound pretreated DDGS and DWG, respectively, compared with untreated samples. An energy balance for the DWG, thin stillage, and CDS coproducts indicated that ultrasonic pretreatment required more energy than was generated by the process in terms of additional biogas production. However, an energy balance for ultrasonic pretreatment of DDGS provided 70% more energy than was required to operate the ultrasonic unit. © 2010 American Society of Agricultural and Biological Engineers.
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Bio-oil produced from biomass by fast pyrolysis is mainly composed of oxygenated organics and contains high content of water, which makes it unsuitable for direct use as fuel. By developing emulsions from diesel and bio-oil, however, the bio-oil can then be used in compression ignition engines. In this work, the emulsions from diesel and bio-oil are produced by using ultrasonic emulsification method. The physicochemical properties of the emulsions were measured, including density, viscosity, flash point, smoke point, freezing point, and gross heating value. The optimum hydrophilic and lipophilic balance (HLB) value of the emulsifier and the influence of emulsification conditions on the emulsion stability were investigated. The results show that the optimum HLB value of the emulsifier for the emulsification of diesel and bio-oil is about 5.5~6.2; the most stable emulsions are then obtained when the emulsification is conducted at 50°C~60°C and with the input work of 180J/mL~300J/mL. With the increase of bio-oil content in the emulsions, the density, viscosity, flash point and smoke point of the emulsions are increased, while their freezing point and gross heating value are decreased.
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Diminishing petroleum resources combined with environmental concerns over CO2 emissions are causing our society to search for sustainable sources of transportation fuel. Lignocellulosic biomass is abundant and inexpensive making it an ideal feedstock to be used for production of liquid transportation fuels. However, many technical challenges exist in conversion of lignocellulosic biomass to liquid fuels. This article is a brief summary of a workshop sponsored by National Science Foundation on June 25-26th, 2007 in Washington DC entitled "Breaking the Chemical and Engineering Barriers to Lignocellulosic Biofuels". The purpose of the workshop was to discuss the key chemical and engineering barriers that must be overcome to make lignocellulosic biofuels a practical reality. Chemistry, catalysts, and chemical engineering offer many new possibilities for conversion of our renewable biomass resources to liquid transportation fuels.
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Alkali lignin of wheat-straw from black liquor was processed by ultrasonic wave and the activation effect of ultrasonic wave on the alkali lignin was discussed. Functional group of alkali lignin was measured by chemical methods, molecular weight was measured by GPC and chemical structure was analysed by 1H NMR. Results indicated that ultrasonic processing was very effective. At ultrasonic processing time 20 min, power 200 W, and mass ratio (0.2 mol/L NaOH : lignin solution) 100 : 1, the contents of phenolic hydroxyl, aliphatic hydroxyl, carboxyl and aldehyde of the alkali lignin are from 1.88 mmol/g to 2.54 mmol/g, from 1.99 mmol/g to 4.14 mmol/g, from 0.59 mmol/g to 0.29 mmol/g, and from 2.16 mmol/g to 2.68 mmol/g, respectively. From the spectrum of 1H NMR, G-lignin percentage (the ratio of area of G-lignin peak to sum of all peaks' area) is from 3.61% to 0. S-lignin percentage is from 0.77% to 0, OCH3 percentage is from 11.50% to 8.90%. The numerical-average molecular weight (Mn) is from 1179 to 5031, the weight-average molecular weight (Mw) is from 10250 to 11605, dispersiveness (Mw/Mn) is from 8.69 to 2.31.
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The nano-structured KF/γ-Al2O3-catalyzed synthesis of biodiesel was performed in ultrasonic irradiation. Effects of experimental parameters including ultrasonic power density, molar ratio of methanol to soybean oil, catalyst amount, reaction temperature and time on the transesterification of soybean oil and methanol were investigated. The fresh and used catalysts were characterized by means of XRD, TEM and BET. The results indicate that increasing the ultrasonic power density causes the increase in the methyl esters concentration of the transesterification. The maximum concentration of methyl esters is 98.70% under the following optimized conditions: ultrasonic power density 53.3 W/L; molar ratio of methanol to soybean oil 6:1; mass ratio of catalyst to soybean oil 3%; reaction temperature 45°C and reaction time 35 min. In comparison to the mechanical stirring, the ultrasonic irradiation allows the significant reduction of the amounts of KF/γ-Al2O3 and methanol and the time requires for reaching equilibrium. The structure of nano KF/γ-Al2O3 surface does not change, but the specific surface area of the nano-catalyst greatly reduces from 60.34 m2/g to 37.26 m2/g after transesterification of soybean oil and methanol in the ultrasound field.
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Increasing demands and concerns for the reliable supply of liquid transportation fuels makes it important to find alternative sources to petroleum based fuels. One such alternative is cellulosic biofuels. However, several technical barriers have hindered large-scale, cost-effective manufacturing of cellulosic biofuels, such as the low density of cellulosic feedstocks (causing high transportation and storage costs) and the lack of efficient pretreatment procedures for cellulosic biomass. This paper reports experimental investigations on ultrasonic vibration-assisted (UV-A) pelleting of cellulosic feedstocks. It studies effects of input variables (ultrasonic vibration, moisture content, and particle size) on output variables (pellet density, stability, durability, pelleting force, and yield of biofuel conversion) in UV-A pelleting. Results showed that UV-A pelleting could increase the density of cellulosic feedstocks and the yield of biofuel conversion. [DOI: 10.1115/1.4003475]
Conference Paper
This paper reviews the biochemical methane potential (BMP) production from anaerobic digestion of corn-ethanol by-products including dried distiller grain with solubles (DDGS), centrifuge solids, thin stillage, and corn-syrup as well as evaluating the effects of ultrasonic pretreatment on biogas production from these feedstocks. Ultrasonic pretreatment was applied with three amplitude settings of 33% (52.8 µmpp), 66% (105.6 µmpp), and 100% (160 µmpp) as well as five time settings of 10, 20, 30, 40, and 50 seconds, respectively, to each of the four by-products before setting up a bench top BMP trial. Biogas production was measured and analyzed for methane content and accumulated methane production. Without ultrasound pretreatment, corn-syrup had the highest methane production potential (408 ml/g VS added) compare to the other by-products. Methane production was increased by 25 and 12% for the ultrasound pretreated DDGs samples and solids samples, respectively, compared with untreated samples. The ultrasonic pretreatment of ethanol co-products was shown to increase methane production from the anaerobic digestion of these products. The ultrasonic pre-treatment of solids co-products (DDGS and centrifuge solids) was far more effective than on liquid co-products (syrup and thin stillage). An energy balance showed that ultrasonic pretreatment of DDGS provided 70% more energy than was required to operate the ultrasonic unit. An energy balance for other co-products however, indicated that the ultrasonic pre-treatment required more energy than was generated by the process in terms of additional biogas production.
Article
The authors have discovered that ultrasonic irradiation of Ni powder increases its activity as a hydrogenation catalyst by >10/sup 5/. In order to probe the origin of this dramatic enhancement, the surface composition has been examined. They find that ultrasonic irradiation of Ni powder causes remarkable changes in particle aggregation, surface morphology, and thickness of the surface oxide coating.
Book
This is the first book dedicated to biorefineries and biobased industrial technologies, and, as such, is directed towards the technological principles of biorefineries, green processes, plants, concepts, current and forthcoming biobased product lines, as well as the economic aspects. Since the hot topics of green chemistry and green processes are of a multidisciplinary interest, this book will benefit the whole spectrum of the process industry, including chemical engineers, process engineers, apparatus construction engineers, chemical industry, chemists in industry, and biotechnologists. The editors and authors are all internationally recognized experts from industry and academia, including Dr. Patrick Gruber, the former Vice President and Chief Technology Officer of Cargill Dow, a winner of the U.S. Presidential Green Chemistry Award and holder of more than 40 patents.
Article
Ultrasonic pretreatment was developed to increase conversion of cellulose to bio-oil in hot-compressed water. The physical structures of cellulose were greatly changed by ultrasonic pretreatment, resulting in excellent swelling and dispersion of cellulose in the water. With the increased surface area and decreased crystallinity and degree of polymerization of cellulose, the bio-oil yield was increased remarkably. The highest bio-oil yield (61.5%) was obtained at 260 °C with a residence time of 0 min for the 1 h pretreated cellulose. Under the optimum reaction conditions, ultrasonic pretreatment increased the bio-oil yield by 22.1% and reduced residence time by 5 min. GC-MS analysis results showed that ultrasonic pretreatment affected the chemical compositions of bio-oils and significantly improved the content of 5-hydroxymethylfurfural in heavy oils.
Article
In this study, the production of methyl ester from Oedogonium sp. oil was studied using an isolated thermo-, solvent-, and sono-tolerant Bacillus sp. lipase immobilized on celite. The application of ultrasound during the reaction reduced the reaction time significantly. The effect of sonication time, enzyme dosage, water content, methanol/oil molar ratio, and solvent addition on the performance of transesterification was studied. The reaction time required in the presence and absence of ultrasound was 2 and 40 h, respectively. Under optimum conditions, 75 and 82% fatty acid methyl ester (FAME) yields were obtained for normal and ultrasound-assisted transesterification, respectively. The reusability of the immobilized enzyme after five cycles did not show much loss in enzyme activity, and this indicates that the isolated enzyme was not affected as a result of the application of ultrasound.
Article
Ethanol is a renewable and environmentally benign substitute for the current fossil-fuel-based transportation fuels. Fermentation of sugars, which is, in general, a slow process, is an essential step in the production of ethanol from renewable sources. This paper reports a successful attempt to accelerate the well-known sugar fermentation process by applying soft sonication. Fermentation of glucose was carried out using Saccharomyces cerevisiae under continuous mild ultrasonication conditions. The kinetics of the fermentation reaction was monitored by 13C nuclear magnetic resonance spectroscopic analysis and weight loss measurements of the fermentation broth. The reaction rate constant was enhanced by 2.3 ± 0.2 and 2.5 ± 0.2 times as a result of sonication at 30 and 20 °C, respectively, as compared to a stirred reaction, and was about 10 times faster than non-stirred fermentation. The acceleration in the fermentation of glucose was observed for both 20 and 40 wt % concentrations of the glucose solution.
Article
The use of biodiesel as an alternative fuel has become more attractive recently because of its environmental benefits such as nontoxicity and biodegradability. However, due to the unfavorable economics and other problems for design and operation of large scale reactors, commercialization of biodiesel has not been significantly effective. The specific challenges in the synthesis route based on transesterification include higher separation times, high operating cost, high energy consumption, and low production efficiency due to equilibrium limitations. The present work highlights the potential use of waste cooking oil as a cheap and economical feedstock discussing the advantages of the process and limitations for transesterification reaction. Improvements in the synthesis process based on the different pretreatment methods and process intensifying techniques are discussed with specific reference to transesterification of waste cooking oil. Different physical and chemical pretreatment methods required for the preparation of feedstock include filtration, drying, acidic esterification, adsorption, crystallization, and distillation for the removal of fatty acids and other contaminants. The critical review also highlights the different process intensification techniques such as cavitational reactors, microwave irradiation, microchannel reactor, oscillatory flow reactor, use of cosolvent, and supercritical transesterification process that can be used for biodiesel production process with an objective of enhancing the reaction rate, reduction in the molar ratio of alcohol to oil, and energy input by intensifying the transport processes and overcoming the equilibrium limitations. Guidelines for the selection of optimum operating parameters have also been given with comparative analysis of the different approaches of process intensification. Finally, some recommendations have been made for the possible research that needs to be done for successful commercialization of biodiesel synthesis.
Article
Biodiesel synthesis from nonedible oils, which offer excellent potential as sustainable feed stock, is highly energy-intensive and slow operation, because it requires considerable processing due to higher initial acid values and due to the fact that the reaction is mass-transfer-controlled. The present work reports the intensification of synthesis of biodiesel from the high-acid-value Nagchampa oil using sonochemical reactors. The synthesis process is a two-step method of esterification in the presence of homogeneous acid catalyst followed by transesterification using an alkaline (KOH) catalyst. The synthesis has also been attempted using conventional methods of reflux for analyzing the degree of intensification. With an objective of avoiding possible saponification reaction in the transesterification based on use of an alkaline catalyst, the acid value of oil was reduced from 18.4 mg KOH/g of oil to 1.4 mg KOH/g of oil, using the first-stage esterification method. The reduction in the acid value allows for an efficient second transesterification stage. The reaction temperature, molar ratio, and catalyst concentration were optimized for esterification and transesterification stages for the ultrasound and conventional techniques. It has been observed that the reaction temperature and reaction time required for esterification, as well as the transesterification stages, are substantially lower in the case of sonochemical reactors, compared to the conventional heating method. Also, the percentage excess of the reactants is significantly reduced, leading to energy savings in the subsequent separation processes for getting the purified product. Overall, the present work has clearly established the efficacy of sonochemical reactors for the intensification of biodiesel synthesis based on a sustainable raw material.
Article
The present study acquaints optimization of ultrasound assisted lime pretreatment to reduce the time of lime pretreatment. The study was conducted on three lignocellulosic biomass materials, Areca nut husk (Areca catechu), bon bogori (Ziziphus rugosa), and moj (Albizia lucida) available in Northeast India, exploiting ultrasound for the pretreatment of lignocellulosic biomass along with lime augments the delignification ratio. The present study reports removal of 68% (bon bogori), 65% (Areca nut husk), and 64% (moj) of the lignin present in the naive lignocellulosic fiber with good recovery of total solid and fermentable sugars, respectively. The simultaneous saccharification and fermentation (SSF) process for the production of bioethanol was also carried out using baker’s yeast. The yield of ethanol was found to be in the range from 0.32 to 0.43 for all the ultrasound assisted lime pretreated biomasses.
Article
The conversion of lignocellulosic biomass for biofuels and biorefinery applications is limited due to the cost of pretreatment to separate or access the biomass’s three main usable components, cellulose, hemicellulose, and lignin. After pretreatment, each component may be utilized via chemical conversion, hydrolysis, and/or fermentation. In this review we aim first, to identify the current status-quo of knowledge of the parametric effects of ultrasound, second, to evaluate the potential of ultrasound as a pretreatment and fractionation method of lignocellulose, and last, to identify the challenges that this technology faces. Ultrasound produces chemical and physical effects which were both found to augment the pretreatment of lignocellulose via delignification and surface erosion. The magnitudes of these effects are altered when the ultrasonic field is influenced by parameters such as solvent, ultrasonic frequency, and reactor geometry and type. Therefore, the implementation of ultrasound for the pretreatment of lignocellulose must consider the variation of ultrasonic influences to capitalize on the key effects of ultrasound. Currently the literature is dominated by low frequency ultrasonic treatment, coupled with alkaline solutions. High frequency ultrasound, oxidizing solutions, and use of combined alternative augmentation techniques show promise for the reduction of energy consumed and synergistic enhancement of ultrasonic treatment. Furthermore, feedstock characteristics, reactor configuration, kinetics, and the ultrasonic environment should be considered.
Article
The batch transesterification of vegetable oil with methanol, in the presence of potassium hydroxide as catalyst, by means of low fre-quency ultrasound (40 kHz) was studied with the aim of gaining more knowledge on intimate reaction mechanism. The concentration of fatty acid methyl esters, of mono-, di-and triglycerides of the actual reaction mixture were determined at short reaction time by HPLC. The effect of ultrasounds on the lipids transesterification correlated with triglyceride structures is discussed. It was found that under ultra-sonic activation the rate-determining reaction switches from DG ! MG (classical mechanic agitation) to MG + ROH ! Gly + ME (ultrasonically driven transesterification).
Article
H2SO4 catalyzed pre-esterification of Jatropha curcas oil was investigated in this study. Ultrasound was used to enhance the mixing extent of methanol and oil. The experimental results showed that 18% methanol (wt% of oil), 1.2% H2SO4 catalyst (wt% of oil) and 900 W/L ultrasonic power density were the optimum conditions for the pre-esterification of J. curcas oil with a 20 mg KOH/g initial acid value (AV). The kinetics of the pre-esterification shows that the apparent forward reaction rate constant k+A increased with the rise of the amounts of methanol, catalyst and ultrasonic power density to some extent, while the reverse reaction rate constant was almost independent on these factors. Compared with mechanical stirring, ultrasonic radiation could greatly enhance the pre-esterification. Finally, a function of ultrasonic power density U was embedded into the kinetic equation, and under the optimum conditions, k+A could be expressed as: k+A=0.034023(−10−6U2+0.002U+0.0531). The relative deviations between the experimental data and the results calculated by the equation are less than 5%.
Article
Completely bio-derived cholinium ionic liquids (ILs) such as choline acetate (ChOAc) are reported to be less expensive, more biocompatible, and more biodegradable and bio-renewable in comparison with the imidazolium ILs that are conventionally used for the pretreatment of lignocellulosic biomass. We demonstrated here, for the first time, that the cholinium-IL-assisted pretreatment of lignocellulosic biomass is enhanced by ultrasound irradiation in comparison with conventional heating. The cellulose saccharification ratio of bamboo powder was approximately 55% when pretreated thermally in ChOAc at 110 °C for 60 min. Conversely, after ultrasonic pretreatment in the same IL at 25 °C for 60 min, 92% of cellulose was hydrolyzed to glucose. Moreover, X-ray diffractometry and Fourier-transform infrared spectrometry analyses revealed that the cellulose crystallinity of pretreated bamboo powder was lower in case of ultrasonic pretreatment in ChOAc than in case of thermal pretreatment in the same IL.
Article
This paper attempts to discern physical mechanism and kinetic aspects of ultrasound irradiation on transesterification of soybean oil with methanol using sulfuric acid as catalyst with approach of coupling experimental results with simulations of cavitation bubble dynamics. Kinetic constants as well as activation energies of transesterification reaction were determined at different alcohol to oil molar ratios and reaction temperatures. The results of this study reveal interesting features of inter–relation between mechanics of ultrasound/cavitation, and the intrinsic behavior (represented by specific rate constant) of the transesterification reaction. The beneficial effect of ultrasound irradiation on transesterification is of physical nature. Several anomalies of ultrasound assisted acid catalyzed transesterification (as compared to conventional system) are: occurrence of reaction at low temperature of 15 °C (albeit with low conversions of 13.45% and 10.2% for alcohol to oil molar ratios of 6:1 and 12:1, respectively); despite higher activation energy, higher rate constant at low alcohol to oil molar ratio of 6:1; and minima shown by reaction rate constant with temperature. The major physical effect of sonication is fine emulsification that generates enormous interfacial area for reaction that overwhelms the effect of specific rate constant. As revealed by simulations, physical effects of cavitation (viz. micro-convection and shock waves) are more pronounced at low temperature, which is primary cause leading to these anomalies.
Article
This study presents the sono-assisted pretreatment and enzymatic saccharification of sugarcane bagasse (SCB) for the production of bioethanol. The effect of sono-assisted alkali (NaOH) pretreatment on the removal of hemicellulose and lignin from SCB was studied and the results showed 80.8% of hemicellulose and 90.6% of lignin removal. Sono-assisted enzymatic saccharification was performed with Cellulomonas flavigena (MTCC 7450) and the yield was found to be affected by liquid-to-solid ratio (LSR), cell mass and pH. The optimum reaction time, LSR, cell mass and pH were found to be 360 min, 15:1, 15 g/L and 6.0 respectively. At optimum conditions, the maximum glucose yield obtained was 91.28% of the theoretical yield and the maximum amount of glucose obtained was 38.4 g/L. The enhancement in performance may be correlated with the swelling of cellulose and accelerated enzymatic saccharification due to the application of ultrasound. The hydrolyzate obtained was fermented using Zymomonas mobilis (MTCC 89) and about 91.22% of the theoretical ethanol yield was observed in 36 h of fermentation.
Article
Batch production of biohydrogen from cassava wastewater pretreated with (i) sonication, (ii) OPTIMASH BG® (enzyme), and (iii) α-amylase (enzyme) were investigated using anaerobic seed sludge subjected to heat pretreatment at 105 °C for 90 min. Hydrogen yield at pH 7.0 for cassava wastewater pretreated with sonication for 45 min using anaerobic seed sludge was 0.913 mol H2/g COD. Results from pretreatment with OPTIMASH BG® at 0.20% and pH 7 showed a hydrogen yield of 4.24 mol H2/g COD. Superior results were obtained when the wastewater was pretreated with α-amylase at 0.20% at pH 7 with a hydrogen yield of 5.02 mol H2/g COD. In all cases, no methane production was observed when using heat-treated sludge as seed inoculum. Percentage COD removal was found to be highest (60%) using α-amylase as pretreatment followed by OPTIMASH BG® at 54% and sonication (40% reduction rate). Results further suggested that cassava wastewater is one of the potential sources of renewable biomass to produce hydrogen.
Article
Glycerol is a major by-product in biodiesel manufacturing, which surplus raises a critical need to transform it into high added-value products. In particular, glycerol carbonate is an important glycerol derivative being the most valuable intermediate for the production of glycidol, which is an added-value product of major industrial interest used, for example, as a precursor for the synthesis of a large number of polymers. Solvent-free conventional thermal activation, ultrasound-activation and microwave-activation in the liquid phase are able to selectively transform glycerol carbonate into glycidol under mild conditions using a ZSM-5 zeolite catalyst and a zinc oxide-supported nanoscaled cobalt oxide catalyst with short reaction times and in the absence of solvent. To the best of our knowledge, we report the highest selectivity to glycidol (>99%) from glycerol carbonate at high conversion values (71%).
Article
Lignin isolated from Miscanthus × giganteus using acidic (FAL) and basic (AL) conditions was thereafter subjected to catalytic depolymerization under thermal or ultrasonic activation. The characterization of lignin samples was achieved by thermogravimetric analysis and FTIR. Three different classes of catalysts containing nickel as the active species have been prepared in this respect: (i) nano-Ni(0) by reduction of NiCl2 with NaBH4 under ultrasonication, (ii) Fe3O4–(NiMgAlO)x and (NiAlO)x by calcination of Mg(Ni)–Al hydrotalcite incorporating Fe3O4, followed by reduction with hydrogen, and (iii) NiO(1 1 1) nanosheets by reduction of Ni(NO3)2 with urea using benzyl alcohol as a structure directing agent. The catalysts were characterized by XRD and XPS techniques. Reduced mixed oxides displayed a moderate activity while a significant increase in conversion (up to 90%) was observed with nano-Ni(0) and NiO(1 1 1) nanosheets catalysts. The conversion and the mass distribution of the reaction products were strongly related to th