Biofuel Production Research Articles

Methylimidazolium ionic liquids - A new class of forever chemicals with endocrine disrupting potential

A class of chemical with a potentially important perceived future contribution to the net zero carbon goal (as “green” solvents) is the methylimidazolium ionic liquids (MILs). These solvents are used in industrial processes such as biofuel production yet little is known about their environmental stability or toxicity in man although one MIL – 1-octyl-3-methylimidazolium (M8OI) – has been shown to activate the human estrogen receptor alpha (ERα). The stabilities of the chloride unsubstituted methylimidazolium (MI) and MILs possessing increasing alkyl chain lengths (2C, 1-ethyl-3-methylimidazolium (EMI); 4C, 1-butyl-3-methylimidazolium (BMI); 6C; 1-hexyl-3-methylimidazolium (HMI), 8C, M8OI; 10C, 1-decyl-3-methylimidazolium (DMI)) were examined in river water and a human liver model system. The MILs were also screened for their abilities to activate the human ERα in vitro and induce uterine growth in pre-pubertal rats in vivo. Short chain MILs (EMI, BMI and HMI) underwent negligible metabolism and mineralisation in river water; were not metabolised in a model of human liver metabolism; activated the human ERα in vitro and were estrogenic in vivo in rats. A structure-based computational approach predicted short chain MIL binding to both the estrogen binding site and an additional site on the human estrogen receptor alpha. Longer chain MILs (M8OI and DMI) were metabolised in river water and partially mineralised. Based on structure-activity considerations, some of these environmentally-derived metabolites may however, remain a hazard to the population. MILs therefore have the potential to become forever chemicals with adverse effects to both man, other animals and the environment in general.

Unlocking the potential of Spirulina microalgae: Cultivating in wastewater treatment for sustainable biofuel production

Municipal wastewater, known for its high nitrogen and phosphorus levels, disrupts natural biogeochemical cycles. However, these nutrients are vital for cultivating green algae, which show potential as a sustainable energy source. In this study, Spirulina microalgae biomass was cultivated from diluted municipal wastewater and converted into biofuel to assess its compatibility with conventional diesel applications. Algae growth rate, nutrient removal from wastewater, and proximate and ultimate analyses of the biomass were conducted. Elemental, functional group, and chemical analyses of the biodiesel were also performed using an elemental analyzer, Fourier-transform infrared (FTIR) spectroscopy, and Gas Chromatography-Mass Spectrometry (GC-MS), respectively. Results showed effective removal of calcium, magnesium, potassium, and nitrogen nutrients by 44.7%, 71.7%, 50%, and 55.6%, respectively, through algae cultivation. Proximate and ultimate analyses confirmed the biomass's energy content and efficiency for energy production. Elemental analysis of biodiesel revealed significant contributions of carbon, hydrogen, and oxygen, while FTIR and GC-MS analyses identified carbon-based components and methyl esters as major constituents, respectively. Physicochemical properties of algae biodiesel met ASTM D6751 limits. This comprehensive assessment suggests that Spirulina algae from wastewater treatment holds promise as a viable energy source for diesel applications.

The role of AdhE on ethanol tolerance and production in Clostridium thermocellum

Many anaerobic microorganisms use the bifunctional aldehyde and alcohol dehydrogenase, AdhE, to produce ethanol. One such organism is Clostridium thermocellum, which is of interest for cellulosic biofuel production. In the course of engineering this organism for improved ethanol tolerance and production, we observed that AdhE was a frequent target of mutations. Here, we characterized those mutations to understand their effects on enzymatic activity, as well ethanol tolerance and product formation in the organism. We found that there is a strong correlation between NADH-linked alcohol dehydrogenase (ADH) activity and ethanol tolerance. Mutations that decrease NADH-linked ADH activity increase ethanol tolerance; correspondingly, mutations that increase NADH-linked ADH activity decrease ethanol tolerance. We also found that the magnitude of ADH activity did not play a significant role in determining ethanol titer. Increasing ADH activity had no effect on ethanol titer. Reducing ADH activity had indeterminate effects on ethanol titer, sometimes increasing and sometimes decreasing it. Finally, this study shows that the cofactor specificity of ADH activity was found to be the primary factor affecting ethanol yield. We expect that these results will inform efforts to use AdhE enzymes in metabolic engineering approaches.

Characterization of Fuel Pellets Made From Rice Husk, Sawdust and Corncob Bond with Cissus Populnea and Manihot Esculenta

There is growing interest in the production of biofuels from biomass wastes. The availability of biomass waste poses the need for technical assessment of pelletisation of biomass waste at industrial production level. The misuse of environmentally friendly and sustainable energy resources and lack of compressed biomass energy products that could enhance fuel quality needs to be addressed. This study intends to determine the energy output from tenary combination of the biomass fuel pellets consisting of rice husks, African birch sawdust, corncobs and their varying mixtures bond with aqueous extract of C. populnea (Cp) and M. esculenta (Me). The combustion characteristics of pellets produced from Rice Husk, African Birch Sawdust, Corncob and their blends (M, M1, M2, M3 and M4) were conducted by the development of an analytical protocol. Pellet admixtures were prepared at each binder ratio of 10% of bulk weight of RH, ABS, corncob and their various blends in the ratios 1:1:1 (M), 1:2:3 (M1), 2:1:3 (M2), 3:1:2 (M3) and 2:3:1 (M4), respectively. The Bulk Density (BD), Ash Contents (AC), Heat Release Rate (HRR) and Calorific Value (CV) of the pellets were measured using established procedures. The result revealed that combustion characteristics of fuel pellets made from Corncob and Blend ratio of 1:2:3 bound with Manihot esculenta gel were enhanced and the fuel pellets possessed sufficient calorific values suitable for energy applications. It was recommended that massive production of fuel pellets from biomass wastes for small and medium scale energy systems could give a positive development to agrarian and rural areas in Nigeria where there is a lot of these resources and lack of stable electrical supply.

Effect of solvent pre-treatment on microwave assisted pyrolysis of Spirulina (Algal Biomass) and Ficus benghalensis (Lignocellulosic Biomass) for production of biofuels: comparative experimental studies

Effect of solvent pre-treatment on microwave assisted pyrolysis of Spirulina (Algal Biomass) and Ficus benghalensis (Lignocellulosic Biomass) for production of biofuels: comparative experimental studies

Microalgae and cyanobacteria as natural sources of antioxidant enzymes and enzyme inhibitors for Alzheimer's and diabetes

Microalgae and cyanobacteria biomass can be cultivated in large amounts, producing a variety of bioactive compounds. As a result, various industries have begun to study the potential of this biomass in a wide range of applications such as biofuel production, environmental remediation for contaminated soil and water, food supplements, and as a source of feed for aquaculture. The cultivation conditions have a profound impact on microalgae biochemical composition. Therefore, the culture conditions must be tailored to the specific application of the biomass. This entails careful control of factors such as light exposure, nutrient concentration, and the application of stress conditions. To further enhance the value of microalgae biomass beyond its nutritional analysis, this review aims to explore the potential of the biomass as biofactories for producing antioxidant enzymes and inhibitors targeting Alzheimer's and diabetes diseases. Both chronic diseases are a growing concern due to an aging population and an increase in obesity rates. Microalgae when exposed to stressful conditions enhance the activity of antioxidant enzymes. However, further studies in the isolation and storage of these enzymes need to be performed. From the literature reviewed microalgae exhibited great potential in inhibiting key enzymes involved in Alzheimer's and Diabetes. The inhibitory potential was observed both in vitro and at a cellular level making them a promising natural alternative to current medication used to inhibit these enzymes.

Recent developments on sustainable biobutanol production: a novel integrative review.

Renewable and sustainable biofuel production, such as biobutanol, is becoming increasingly popular as a substitute for non-renewable and depleted petrol fuel. Many researchers have studied how to produce butanol cheaply by considering appropriate feedstock materials and bioprocess technologies. The production of biobutanol through acetone-butanol-ethanol (ABE) is highly sought after around the world because of its sustainable supply and lack of competition with food. The purpose of this study is to present the current biobutanol production research and to analyse the biobutanol research conducted during 2006 to 2023. The keyword used in this study is "Biobutanol," and the relevant data was extracted from the Web of Science database (WoS). According to the results, institutions and scholars from the People's Republic of China, the USA, and India have the highest number of cited papers across a broad spectrum of topics including acetone-butanol-ethanol (ABE) fermentation, biobutanol, various pretreatment techniques, and pervaporation. The success of biobutanol fermentation from biomass depends on the ability of the fermentation operation to match the microbial behaviour along with the appropriate bioprocessing strategies to improve the entire process to be suitable for industrial scale. Based on the review data, we will look at the biobutanol technologies and appropriate strategies that have been developed to improve biobutanol production from renewable biomass.

Adsorption enhanced biological treatment of hydrothermal liquefaction aqueous phase derived from municipal sludge

Hydrothermal liquefaction (HTL) is a promising method for municipal sludge valorization through waste minimization and biofuel production. The process wastewater, HTL aqueous, presents a significant challenge for scale-up due to recalcitrant compounds. In this study, granular activated carbon (GAC) was used to remove potential inhibitors from HTL aqueous through adsorption to enhance aerobic and anaerobic biological treatment. GAC removed up to 61 % chemical oxygen demand (COD), 50 % biochemical oxygen demand (BOD) and potential inhibitors, such as total phenolic compounds (87 %) and N-heterocycles (90 % of pyridines) at 100 g/L. Conversely, most volatile fatty acids remained in HTL aqueous. Subsequently, mesophilic and thermophilic specific methane potential increased by up to 97 % and 83 %, respectively. BOD increased by up to 50 %, which enhanced BOD/COD ratio from 81 % to 93 % before and after adsorption. This study established the groundwork for HTL aqueous adsorption, described mechanism for pollutant removal, and provided insights for biological treatment.

Green nanobiocatalysts: enhancing enzyme immobilization for industrial and biomedical applications.

Nanobiocatalysts (NBCs), which merge enzymes with nanomaterials, provide a potent method for improving enzyme durability, efficiency, and recyclability. This review highlights the use of eco-friendly synthesis methods to create sustainable nanomaterials for enzyme transport. We investigate different methods of immobilization, such as adsorption, ionic and covalent bonding, entrapment, and cross-linking, examining their pros and cons. The decreased environmental impact of green-synthesized nanomaterials from plants, bacteria, and fungi is emphasized. The review exhibits the various uses of NBCs in food industry, biofuel production, and bioremediation, showing how they can enhance effectiveness and eco-friendliness. Furthermore, we explore the potential impact of NBCs in biomedicine. In general, green nanobiocatalysts are a notable progression in enzyme technology, leading to environmentally-friendly and effective biocatalytic methods that have important impacts on industrial and biomedical fields.

Biorefinery of red seaweed Palmaria palmata for production of bio-based chemicals and biofuels

The seaweed Palmaria palmata was used as feedstock for production of chemical/fuel precursors (acetone, butanol, ethanol) and biogas. Palmaria palmata consists of xylan as major cell wall polysaccharide, as well as galactan and glucan. First, the biomass was subjected to acid hydrolysis at laboratory scale to solubilise fermentable sugars using acetic or hydrochloric acid as catalysts. Differences were observed in composition and amenability to hydrolysis of seaweeds from different harvests. Highest saccharification yields were obtained using HCl (pH 1.7, 120 °C, up to 80 % of xylose). Hydrolysates were fermented to acetone-butanol-ethanol by Clostridium beijerinckii reaching yields of 0.28 g products/g consumed sugars. The process by-products (solids after acetic acid hydrolysis and spent fermentation broth) were used as feedstocks for anaerobic digestion showing biogas yields between 310 and 650 L/kg dry organic material when mixed in different ratios with sugar beet pulp. Subsequently, the hydrolysis and fermentation processes were upscaled up to a 100-L pilot volume where nanofiltration was implemented to increase sugar concentration and remove salts. While high monomeric sugar yields were replicated during upscaling, fermentation inhibition was observed in the upscaled process. This paper shows Palmaria palmata to be a suitable feedstock for the co-production of bio-butanol and biogas and highlights process development needs to desalt and detoxify seaweed hydrolysates prior to fermentation.

Impact of key parameters on the hydrothermal carbonization process of sewage sludge: A systematic review

The hydrothermal carbonization (HTC) process is a promising green technology for reducing and reusing sewage sludge and can be a powerful tool against the current problems of energy scarcity, climate imbalance, and environmental pollution. Despite its admirable robustness, HTC can be easily tuned by controlling temperature and reaction time, as well as by biomass:water mass ratio and pH. The systematized knowledge of the relationship between these parameters is fundamental to successful innovative research aiming at scaling up the process. In this review, a bibliometric analysis based on ten years of scientific publications was carried out. The PRISMA guidelines were adopted to select forty-seven works as a source of information and critical discussion on key findings of reactions performed in high-pressure reactors. The global scientific community is mainly concerned with solid products (hydrochar) and the study of mechanisms of removal/adsorption of nutrients, minerals, and pollutants. The gaseous phase is in the background, opening up numerous research possibilities. Future outlooks are focused on coupling HTC with biorefineries to strengthen the valorization of sewage sludge, contribute to the production of biofuels and biofertilizers, and benefit communities currently without access to environmental sanitation.

The lignin riddle in jute: A comparative genomic investigation identifies targets for improving fiber quality

Jute fiber has become more popular in recent years due to its renewability, biodegradability, low manufacturing costs, and wide range of uses. However, one of the major components of fiber is lignin, which impairs the fiber quality and, as a result, makes jute fiber unsuitable for use in the textile industry and biofuel production. The availability of the jute (Corchorus olitorius) genome sequence provides the opportunity to perform a systematic analysis of the gene families and transcription factors specific to the lignin biosynthesis. Here, genome-wide screening was performed to identify the members of gene families associated with lignin biosynthesis in jute. Following this, phylogenetic analysis was carried out with functionally characterized genes involved in lignin biosynthesis of other species. The expression analysis among different tissues and different regions of bark tissue, taking into account fiber developmental stages, is also conducted to identify the genes mainly involved in jute fiber lignification. Fourteen genes and eleven transcription factors belonged to bona fide clades and showed strong expression in highly lignified tissues. Moreover, the transcript levels of these proteins were higher in the bottom bark tissues, which have a higher lignin accumulation compared to the top bark tissues, suggesting these genes were the core lignification genes in fiber formation. Similarly, gene ontology and protein-protein interactions analysis indicated that these genes were mainly involved in lignin biosynthesis and interacted with each other. The identification of the major lignification genes and transcription factors involved in jute fiber development provides a strong foundation for the development of jute cultivars to improve fiber quality.

Valorization of cheese-making residues in biorefineries using different combinations of dark fermentation, hydrothermal carbonization and anaerobic digestion

Dark fermentation (DF), hydrothermal carbonization (HTC) and anaerobic digestion (AD) are applied, in different combinations, to cheese whey (CW), which is the liquid effluent from the precipitation and removal of milk casein during the cheese-making process. The aim and novelty of this research is to investigate the production of various biofuels (H2-rich gas, hydrochar and biogas) in cascade, according to the waste biorefinery concept. The simplest case is the direct AD of CW. The second investigated possibility is the preliminary HTC of CW, producing hydrochar, followed by the AD of the process water from which hydrochar is separated by filtration. The third possibility is based on DF of CW, followed by the AD of the fermentate (F) from DF. The final possibility is based on DF of CW, followed by HTC of the F, and then AD of the process water. Accordingly, the physical and chemical properties of CW, F, resulting hydrochar and process water (PW), and biomethane potentials of CW, F, and process waters are studied to determine the energy and carbon balances of all variants. In brief, the first variant, direct AD of CW, is believed to be the most energy efficient method.

Production of a high-energy solid biofuel from biochar produced from cashew nut shells

The aim of the study is to produce a solid biofuel of high physico-mechanical and energetic quality from heat-treated cashew nut shells. Raw cashew nut shells are heat treated at 300 °C for 120 min at a heating rate of 1 °C/s. The resulting biochar is milled to 74 μm. Sugar cane molasses was incorporated into the biochar powder at a rate of 10% without the addition of water. The mass yields of solid, liquid and gaseous products obtained were 46.5%, 27.6% and 25.9% respectively. The solid biofuel produced has slightly improved physicochemical and energy properties over biochar, except ash and moisture content. Thus, the addition of binder and densification increased the ash and moisture content of the solid biofuel compared to the biochar obtained. With a higher calorific value of 33.02 MJ/kg, the solid biofuel has high water resistance and meets the quality requirements of class A1 of the NF EN ISO 17225-6 standard in terms of density and mechanical strength. Solid biofuel is ideal for use in households and biomass power stations.

Heterologous glucose-6-phosphate dehydrogenase empowers the biofuel potential of Tetradesmus obliquus via generating lipogenic NADPH

Large-scale production of biofuels from oleaginous microalgal feedstocks in a commercially feasible manner is hampered by their relatively slow growth rates and overall lipid yield than the rapidly proliferating algal species. Therefore, it is pivotal to obviate this bottleneck by augmenting lipid overproduction in fast-growing microalgal species by heterologous overexpression lipogenic genes from model oleaginous species. In this regard, the pentose phosphate pathway of Tetradesmus obliquus was perturbed by heterologous overexpression of glucose-6-phosphate dehydrogenase (PtG6PD) from the model pennate diatom Phaeodactylum tricornutum, known for its oleaginicity. The role of PtG6PD in increasing lipid production was reported in the heterologous T. obliquus. Total lipid content was increased by 2.09- and 2.31-fold in transgenic lines than WT by elevating the lipogenic NADPH, without any negative impact on their growth rates. Interestingly, lipid yields in the transgenic strains reached up to 93 mg/L and 103 mg/L which showed a further 2-fold enhancement under nitrogen-deficient conditions. Furthermore, it was demonstrated that PtG6PD overexpression also altered fatty acid composition, with a specific increment in total monounsaturated fatty acids. Our results uncovered the pivotal role of the pentose phosphate pathway in supplying lipogenic NADPH in T. obliquus and identified key genetic targets for lipid biosynthesis enhancement in alternative hosts. Altogether, these findings open avenues for metabolic engineering in non-model and fast-growing non-oleaginous microalgal species, thereby presenting a promising strategy for empowering commercially viable photosynthetic cell factories for biofuel production.

A comprehensive review of current progress in biofuel production using marine algae biomass

The world's fossil fuel resources are rapidly depleting as the global population grows and energy demands rise. Current fossil fuel supplies are insufficient to meet rising demand and are nearing depletion. Careless exploitation of fossil fuels increases greenhouse gas emissions, environmental pollution, and global warming, resulting in ecological imbalances and health risks. Consequently, contamination, rising temperatures, and high oil costs have fueled the search for renewable and alternative energy sources. This study seeks to explore renewable energy alternatives that are critical to meeting future global energy demands. Marine algae such as red algae, green algae, and brown algae are gaining popularity as economically viable and environmentally friendly sources of renewable biofuel. Several studies are currently underway to assess the ability of marine algae to produce a variety of bioproducts, including biofuels. Macroalgae, in particular, emerges as an ideal resource for biofuel production due to their lipid and carbohydrate content, coupled with low or absent lignin content. The article investigates the potential of marine algal species to promote biofuel production and discusses novel methods for improving biofuel yields. It also emphasizes the economic factors and challenges associated with sustainable biofuel production.

The role of natural resources, and economic development in evaluating the environmental effects of biofuel and waste energy generation in the group of BRICS

The green energy sources such as biomass conversions and waste energy have shown great potential in environmental management. This article aims to examine the changes brought about by the production of biofuel and the management of solid fossil waste over the past forty years, and to analyze the significant roles that natural resources and economic factors have played in the BRICS countries (Brazil, Russia, India, China, and South Africa) from 1990 to 2021. To achieve accurate and feasible results, second-generation econometric methodologies were applied. The Driscoll-Kraay standard errors (DKSE) approach revealed a significant negative relationship between biofuel production and environmental damage through waste management. Thus, an increase in biofuel production is associated with a reduction in environmental degradation in the region. Furthermore, the results indicate that environmental degradation (ED), the dependent variable, is still positively correlated with natural resources, urbanization, trade, and economic growth. As the financial sector struggles to address environmental threats, stringent monitoring of financial control measures and provisions for environmental issues is necessary. To achieve sustainable development, BRICS member countries need to address the issues of natural resource exhaustion and over-exploitation. The findings of this research suggest policy support for sustainable redevelopment, which should be goal-oriented and backed by the central authorities of the respective countries.

Valorization of the complex organic waste in municipal solid wastes through the combination of hydrothermal carbonization and anaerobic digestion

Municipal Solid Wastes (MSW) consist of the valorizable inorganic fraction, i.e., Refuse Derived Fuel, and the organic fraction which also can be valorized. However, the separated organic fraction, which is known as Complex Organic Waste (COW), contains traces of glass, plastics, non-ferrous metals, and stones. Thus, the aim of this work was to determine the value of the COW that comes from a MSW separation plant through the combination of Hydrothermal Carbonization (HTC) and Anaerobic Digestion (AD) for the production of biofuels. COWs were conditioned to undergo HTC for 1 h at 180 °C and 190 °C. HTC liquid was used as a substrate operating an Anaerobic Hybrid Reactor (AHR) in continuous mode with 5 gCOD/Ld at 35 ± 2 °C. The hydrochar contained on average (dry matter): (180 °C) 30.44 % carbon and 15.47 MJ/kg and (190 °C) 40.44 % carbon and 17.60 MJ/kg. The AHR removed more than 93 % (COD) reaching 0.34 LCH4 at STP/gCODrem, and no inhibitory effects were observed. The coupling of HTC with AD at low temperatures for short times turned out to be a promising alternative for the valorization of COW, i.e., it produced 10,888 MJ (94 % HTC and 6 % AD) per metric ton of COW.

The Microalgae Chlamydomonas for Bioremediation and Bioproduct Production.

The extensive metabolic diversity of microalgae, coupled with their rapid growth rates and cost-effective production, position these organisms as highly promising resources for a wide range of biotechnological applications. These characteristics allow microalgae to address crucial needs in the agricultural, medical, and industrial sectors. Microalgae are proving to be valuable in various fields, including the remediation of diverse wastewater types, the production of biofuels and biofertilizers, and the extraction of various products from their biomass. For decades, the microalga Chlamydomonas has been widely used as a fundamental research model organism in various areas such as photosynthesis, respiration, sulfur and phosphorus metabolism, nitrogen metabolism, and flagella synthesis, among others. However, in recent years, the potential of Chlamydomonas as a biotechnological tool for bioremediation, biofertilization, biomass, and bioproducts production has been increasingly recognized. Bioremediation of wastewater using Chlamydomonas presents significant potential for sustainable reduction in contaminants and facilitates resource recovery and valorization of microalgal biomass, offering important economic benefits. Chlamydomonas has also established itself as a platform for the production of a wide variety of biotechnologically interesting products, such as different types of biofuels, and high-value-added products. The aim of this review is to achieve a comprehensive understanding of the potential of Chlamydomonas in these aspects, and to explore their interrelationship, which would offer significant environmental and biotechnological advantages.

Exploring Bacillus species xylanases for industrial applications: screening via thermostability and reaction modelling.

Xylanases derived from Bacillus species hold significant importance in various large-scale production sectors, with increasing demand driven by biofuel production. However, despite their potential, the extreme environmental conditions often encountered in production settings have led to their underutilisation. To address this issue and enhance their efficacy under adverse conditions, we conducted a theoretical investigation on a group of five Bacillus species xylanases belonging to the glycoside hydrolase GH11 family. Bacillus sp. NCL 87-6-10 (sp_NCL 87-6-10) emerged as a potent candidate among the selected biocatalysts; this Bacillus strain exhibited high thermal stability and achieved a transition state with minimal energy requirements, thereby accelerating the biocatalytic reaction process. Our approach aims to provide support for experimentalists in the industrial sector, encouraging them to employ structural-based reaction modelling scrutinisation to predict the ability of targeted xylanases. Utilising crystal structure data available in the Carbohydrate-Active enzymes database, we aimed to analyse their structural capabilities in terms of thermal-stability and activity. Our investigation into identifying the most prominent Bacillus species xylanases unfolds with the help of the semi-empirical quantum mechanics MOPAC method integrated with the DRIVER program is used in calculations of reaction pathways to understand the activation energy. Additionally, we scrutinised the selected xylanases using various analyses, including constrained network analyses, intermolecular interactions of the enzyme-substrate complex and molecular orbital assessments calculated using the AM1 method with the MO-G model (MO-G AM1) to validate their reactivity.