Second-generation Biofuel Feedstocks Research Articles

Synthesis of biodiesel from residual oil extracted from spent bleaching earth using spent bleaching earth-supported catalyst

Proper disposal of spent bleaching earth (SBE) is much anticipated to create a circular economy. In this study, a two-pronged approach was employed to utilise SBE from palm oil refinery for its suitability to act as second-generation biofuel feedstock and catalyst. The SBE was first wet-impregnated and doped with potassium hydroxide (KOH) to further enhance the catalytic activity. The hexane-extracted bleached oil of SBE at conditions of 40 g SBE, 1:4 ratio of oil to n-hexane, and 6 hr extraction time was subjected to different transesterification parameters i.e., catalyst loading, oil: methanol ratio, reaction temperature, and reaction time. The obtained catalysts were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy with energy dispersive X-ray, temperature programmed desorption of carbon dioxide (TPD-CO2) and Brunauer-Emmett-Teller (BET) techniques. The N2 adsorption-desorption and TPD-CO2 analyses indicated that SBE/KOH (600 °C) had the highest attainable BET surface area (22.62 m2/g) and basicity (25.82 cm3/g). SBE/KOH (600 °C) exhibited the highest biodiesel yield (80.3%) at the optimised reaction conditions: (80 °C, 2 wt% catalyst loading, 1:20 oil: methanol ratio and 2 h reaction time) compared to 67.3% via the unmodified control. The kinetics study revealed that the experimental results followed the first order reaction kinetics. The activation energy, enthalpy (ΔH) and entropy (ΔS) were determined to be 90.06 kJ/mol, 6.92 × 10−4 kJ/mol and −0.0414 kJ/mol K, respectively while the Gibbs free energy (ΔG) was 15.443 kJ/mol. Overall, SBE has enormous potential as one of the alternative sources for second-generation biofuel production.

Enhanced ethanol production using hydrophobic resin detoxified Pine forest litter hydrolysate and integrated fermentation process development supplementing molasses.

Globally escalating ethanol demand necessitates the use of hybrid technologies integrating first- and second-generation biofuel feedstocks for achieving the futuristic targets of gasoline replacement with bioethanol. In present study, an optimized two-step sequential pre-treatment (first dilute alkali, then dilute acid) of Pine forest litter (PFL) was developed. Furthermore, the saccharification of pre-treated PFL was optimized through Response Surface Methodology using Box-Behnken Design, wherein 0.558g/g of reducing sugar was released under the optimized conditions (12.5% w/v of biomass loading, 10 FPU/g of PFL enzyme loading, 0.15% v/v Tween-80 and 48h incubation time). Moreover, during hydrolysate fermentation using Saccharomyces cerevisiae NCIM 3288 strain, 22.51 ± 1.02g/L ethanol was produced. Remarkably, hydrophobic resin (XAD-4) treatment of PFL hydrolysate, significantly removed inhibitors (Furfural, 5-hydroxymethylfurfural and phenolics) and increased ethanol production to 27.38 ± 1.18g/L. Furthermore, during fermentation of molasses supplemented PFL hydrolysate (total initial sugar: 100 ± 3.27g/L), a maximum of 46.02 ± 2.08g/L ethanol was produced with 0.482g/g yield and 1.92g/l/h productivity. These findings indicated that the integration of molasses to lignocellulosic hydrolysate, would be a promising hybrid technology for industrial ethanol production within existing bio-refinery infrastructure.

Production of first and second-generation biodiesel for diesel engine operation: A review

Researchers are looking at alternative cleaner technologies to fulfill the rising need for greener fuels. For this reason, alternatives like bioethanol and biodiesel have become commercially available. Renewable fuels are classified as either "first generation," "second generation," or "third generation" depending on the feedstock used in their manufacture. Over the past decade, society's reliance on first-generation biofuel feedstocks has created an inbuilt rivalry between food and fuel. Second-generation biofuel feed-stocks, such as non-edible agricultural waste products, energy crops, and crop residues, have been illuminated by emerging technical prospects. Technologies for producing biofuels have been proposed and developed in multiple stages, with first-generation technologies being the most developed. In several nations, including the United States, corn grain is used as feedstock in bio-refineries. There is a risk that food and fuel prices will rise as a result of the usage of edible materials in crops like corn. Second-generation biofuel manufacturing technology that utilizes crop residues has been developed to deal with this kind of problem. This study investigates and evaluates the economic viability and environmental sustainability of the proposed solution for the production of second-generation biodiesel.

Comparative study of pyrolysis and hydrothermal liquefaction of microalgal species: Analysis of product yields with reaction temperature

Renewable and sustainable biofuel production from algal biomass has been explored vigorously due to the owing potential of overcoming the limitations of first and second-generation biofuel feedstocks. Thermochemical conversion technologies are considered promising routes for bioenergy production from algal biomass and have been extensively investigated over the last few years. This paper aims to review the various pyrolysis (slow, fast, and microwave -assisted) processes and hydrothermal liquefaction (HTL) techniques. The fast pyrolysis is involving a higher heating rate and shorter residence time compared to slow pyrolysis. Microwave-assisted pyrolysis (MAP) is considered a highly efficient process due to uniform heating. Due to a high moisture feedstock, the HTL process is considered the most energy-efficient processing option for algal biomass. In all these processes, the process temperature is considered the most critical parameter affecting product yield. This paper provides a detailed analysis and discussion on the effect of temperature and heating rates on the product (biochar, bio-oil, and syngas) yields for various microalgal species. The process details, different approaches, and process conditions investigated, challenges and recent advancements achieved in both technologies have been discussed in detail that provides useful insights to design a sustainable process and understand the process feasibility.

Growing Jatropha (Jatropha curcas L.) as a Potential Second-Generation Biodiesel Feedstock

Dwindling supplies of fossil fuels and their deleterious impacts on human health and the global environment have intensified the search for substitute energy sources. Biodiesel has been identified as a promising renewable energy substitute for diesel fuel due to several comparable and sustainable properties. However, approximately 95% of biodiesel is derived from edible oil crops, threatening the current food supplies. Therefore, the biodiesel production potential from inexpensive, non-edible, and non-conventional bioenergy crops, such as Jatropha (Jatropha curcas L.), has attracted the attention of many researchers, policymakers, and industries globally. Jatropha is considered to be the second-generation biofuel feedstocks for biodiesel production. However, sustainable biodiesel generation from J. curcas oil has not yet been attained, owing to different socio-economic, ecological, and technical factors. This study aimed to synthesize the information from the existing literature on the present status and to identify the knowledge gaps for future research on Jatropha by providing comprehensive information regarding its origin and distribution, morphology, phenology, and reproduction, genetic diversity, its productivity, oil content, and fatty acid composition, the methodology used for extracting biodiesel, and agronomic, economic, and environmental aspects of biodiesel production. The germplasm screening of J. curcas and the exploration of its adaptability and agronomic potential across diverse climates are highly desired to promote this crop as an alternative biofuel crop, particularly in arid and semi-arid regions. Moreover, future research should focus on developing, optimizing, and modernizing the technologies involving seed collection, the processing of seeds, oil extraction, and the production of biodiesel.

Functional characterization of a highly specific l-arabinose transporter from Trichoderma reesei

BackgroundLignocellulose biomass has been investigated as a feedstock for second generation biofuels and other value-added products. Some of the processes for biofuel production utilize cellulases and hemicellulases to convert the lignocellulosic biomass into a range of soluble sugars before fermentation with microorganisms such as yeast Saccharomyces cerevisiae. One of these sugars is l-arabinose, which cannot be utilized naturally by yeast. The first step in l-arabinose catabolism is its transport into the cells, and yeast lacks a specific transporter, which could perform this task.ResultsWe identified Trire2_104072 of Trichoderma reesei as a potential l-arabinose transporter based on its expression profile. This transporter was described already in 2007 as d-xylose transporter XLT1. Electrophysiology experiments with Xenopus laevis oocytes and heterologous expression in yeast revealed that Trire2_104072 is a high-affinity l-arabinose symporter with a Km value in the range of sim 0.1–0.2 mM. It can also transport d-xylose but with low affinity (Kmsim 9 mM). In yeast, l-arabinose transport was inhibited slightly by d-xylose but not by d-glucose in an assay with fivefold excess of the inhibiting sugar. Comparison with known l-arabinose transporters revealed that the expression of Trire2_104072 enabled yeast to uptake l-arabinose at the highest rate in conditions with low extracellular l-arabinose concentration. Despite the high specificity of Trire2_104072 for l-arabinose, the growth of its T. reesei deletion mutant was only affected at low l-arabinose concentrations.ConclusionsDue to its high affinity for l-arabinose and low inhibition by d-glucose or d-xylose, Trire2_104072 could serve as a good candidate for improving the existing pentose-utilizing yeast strains. The discovery of a highly specific l-arabinose transporter also adds to our knowledge of the primary metabolism of T. reesei. The phenotype of the deletion strain suggests the involvement of other transporters in l-arabinose transport in this species.

A comprehensive review on oilseed cakes and their potential as a feedstock for integrated biorefinery

In oil processing industry, large number of oilseed cakes remains after the extraction of oil. Oilseed cakes and meals are the residues would act as valuable feeds for livestock as it is rich in protein. These agricultural residues serve as a major valuable feedstock for cattle and used for the production of value-added products such as biogas, biofuel, biopolymer, antibiotics, enzymes, etc. The usage of oilseed cake as raw material would reduce environmental pollution as well as the production cost. This can be served as a potential solution to overcome nutritional problems in animals by enriching the nutrition using appropriate technologies. As the world moving towards sustainable fuel and chemical synthesis using renewable resources deemed as second-generation biofuel feedstock rather than fossil fuels, these non-edible oilseed cakes are used to produce biofuels with an integrated biorefinery perspective. The oilseed cakes plays vital role in the area of enzyme and fermentation technology. The fermentation process using fungi could act as relatively low-cost appropriate technology for upgrading nutrients in oilseed cakes. Oilseed cakes are rich in fibre and have a high concentration of non-starch polysaccharides (NSP) such as cellulose and hemicellulose (Xylan). Lipase and alpha-amylase are the two most essential enzymes produces by the oilseed cake. This review focuses on exploiting the various oilseed cakes and their commercial utilization by implementing various biotechnological approaches.

Residual biomass from food processing industry in Cameroon as feedstock for second-generation biofuels

The yields in bioconversion of residues produced in the Cameroon food industry to liquid and gaseous biofuels were evaluated and the potential of these residues as feedstock for renewable energy production in Cameroon were assessed. Residues generated after processing avocado, cocoa, and peanut crops were converted at laboratory-scale to second-generation gaseous biofuels (biogas) and liquid biofuels (ethanol). Mechanical (milling), thermal-chemical (steam-NaOH), and microwave pretreatments were applied before hydrolysis of biomass using cellulolytic enzymes. Cellulosic sugars production potential was also assessed. The energy conversion rate was higher when anaerobic digestion technology was applied to convert the tested biomass to methane. The total Cameroon potential under anaerobic digestion technology is over 330,000 m3, which represents 28% from oil consumption or 5.39% from electricity consumption when lignocellulosic ethanol technology was applied. The national potential was assessed up to 200,000 kg, representing 17% from oil consumption in transport or 3.19% from electricity consumption. Overall, the share of energy potential of the tested residual biomass is important when compared to fossil fuel consumption in Cameroon and represents an important potential feedstock for electricity production.

Characterisation and Py-GC/MS analysis of Imperata Cylindrica as potential biomass for bio-oil production in Brunei Darussalam

Bio-oil production from renewable sources has been seen as suitable alternative to supply future energy demand. Perennials grasses are currently being developed as a suitable second-generation biofuel feedstock. It has advantages such as rapid growth rate, easy to grow, minimal maintenance and utilise marginal land without competing with food supply. Taking into account of the various challenges attributed to the transformation of second-generation biomass for energy production, this work systematically looks at the ecological perspective and the availability for bioenergy production from Imperata Cylindrica in Brunei Darussalam. Biomass characterisation was carried out to determine the properties and energy content, meanwhile py-GC/MS study was conducted to identify building blocks of value-added chemical from I. cylindrica. The physicochemical properties of feedstock was thoroughly evaluated using thermogravimetric analysis, proximate analysis, elemental analysis, compositional analysis, calorific value, and analytical pyrolysis interfaced with gas chromatograph (Py-GC/MS). Characterisation results indicate that Imperata Cylindrica has a calorific value of 18.39 MJ/kg, with low ash content and high percentage of volatile matter. Py-GC/MS analysis revealed the presence of furfural, 2,3-dihydrobenzofuran, 4-vinylguaiacol, propenylguaiacol, guaiacol and 4-ethylphenol. The fixed-bed pyrolysis experiment of imperata cylindrica showed that the yield of bio-oil increases with the increase of temperature and it reached a peak of 37.16% at 500 °C. These results show that Imperata Cylindrica is suitable as feedstock for bio-oil production via pyrolysis process.

Genomic skimming for identification of medium/highly abundant transposable elements in Arundo donax and Arundo plinii.

Transposable elements (TEs) are the most abundant genetic material for almost all eukaryotic genomes. Their effects on the host genomes range from an extensive size variation to the regulation of gene expression, altering gene function and creating new genes. Because of TEs pivotal contribute to the host genome structure and regulation, their identification and characterization provide a wealth of useful data for gaining an in-depth understanding of host genome functioning. The giant reed (Arundo donax) is a perennial rhizomatous C3 grass, octadecaploid, with an estimated nuclear genome size of 2744 Mbp. It is a promising feedstock for second-generation biofuels and biomethane production. To identify and characterize the most repetitive TEs in the genomes of A. donax and its ancestral A. plinii species, we carried out low-coverage whole genome shotgun sequencing for both species. Using a de novo repeat identification approach, 33,041 and 28,237 non-redundant repetitive sequences were identified and characterized in A. donax and A. plinii genomes, representing 37.55 and 31.68% of each genome, respectively. Comparative phylogenetic analyses, including the major TE classes identified in A. donax and A. plinii, together with rice and maize TE paralogs, were carried out to understand the evolutionary relationship of the most abundant TE classes. Highly conserved copies of RIRE1-like Ty1-Copia elements were discovered in two Arundo spp. in which they represented nearly 3% of each genomic sequence. We identified and characterized the medium/highly repetitive TEs in two unexplored polyploid genomes, thus generating useful information for the study of the genomic structure, composition, and functioning of these two non-model species. We provided a valuable resource that could be exploited in any effort aimed at sequencing and assembling these two genomes.

Way forward to achieve sustainable and cost-effective biofuel production from microalgae: a review

Driven by policies aimed at enhancing energy security and mitigating greenhouse gas emissions, the production and use of biofuels have significantly increased in recent years. Microalgae owing to its multiple advantages which include high lipid content, sustainable biomass production, effective land and water utilization are the most potential biofuel feedstock that can provide drop-in fossil fuel replacements without stimulating competition for agricultural resources and are considered to be more environmentally benign than the first- and second-generation biofuel feedstocks. However, there are many existing technical and scientific impediments that are yet to be resolved. Keeping this in view, the present review provides a concise account of the microalgal species known to accumulate high levels of lipid and describes the main factors that should be taken into consideration while selecting suitable algal strains for mass cultivation. The underlining advantages and limitations of raceway pond and photobioreactor cultivation systems are also examined. The recent advances in genetic engineering of microalgae to improve biomass and lipid productivity are then highlighted, which include the ongoing debate over the biosafety issues pertinent to the use of genetically modified algae. Furthermore, a wide range of high-value products that can be co-produced from microalgae have been discussed. The review concludes with a comprehensive summary of the major techno-economic constraints to commercialization of algal-derived biofuels along with promising methods for overcoming these challenges in order to produce cost-competitive and environmentally sustainable biofuel.

Thermotolerant fermenting yeasts for simultaneous saccharification fermentation of lignocellulosic biomass

Lignocellulosic biomass is the most abundant renewable source of energy that has been widely explored as second-generation biofuel feedstock. Despite more than four decades of research, the process of ethanol production from lignocellulosic (LC) biomass remains economically unfeasible. This is due to the high cost of enzymes, end-product inhibition of enzymes, and the need for cost-intensive inputs associated with a separate hydrolysis and fermentation (SHF) process. Thermotolerant yeast strains that can undergo fermentation at temperatures above 40°C are suitable alternatives for developing the simultaneous saccharification and fermentation (SSF) process to overcome the limitations of SHF. This review describes the various approaches to screen and develop thermotolerant yeasts via genetic and metabolic engineering. The advantages and limitations of SSF at high temperatures are also discussed. A critical insight into the effect of high temperatures on yeast morphology and physiology is also included. This can improve our understanding of the development of thermotolerant yeast amenable to the SSF process to make LC ethanol production commercially viable.

Microwave assisted chemical pretreatment of Miscanthus under different temperature regimes

Miscanthus is a major bioenergy crop in Europe and a potential feedstock for second generation biofuels. The most efficient and realistic method to produce fermentable sugars from lignocellulosic biomass is by enzymatic hydrolysis, assisted by thermo-chemical pretreatment. Recently, microwave technology has drawn growing attention, because of its unique effects and performance on biomass. In this work, microwave energy was applied to facilitate NaOH and H2SO4 pretreatment for Miscanthus under different temperatures (130–200 °C) for 20 min. The yields of reducing sugars from Miscanthus during the pretreatment process increased up to 180 °C and then declined with increasing temperature. Out results here showed a remarkable sugar yield from available carbohydrate (73 %) at the temperature of 180 °C by using 0.2 M H2SO4. In comparison with conventional heating pretreatment studied at same temperature with same biomass material, the reducing sugar release in this study was 17 times higher within half the time. It was highlighted that the major sugar component could be tuned by changing pretreatment temperature or pretreatment media. Optimally, the glucose and xylose yield from available carbohydrate are 47 and 22 % by using 0.2 M H2SO4 and NaOH respectively when temperature was 180 °C. The digestibility of pretreated Miscanthus was 10 times higher than that of untreated biomass. 68–86 % of the lignin content was removed from biomass by 0.2 M NaOH. Simultaneous saccharification fermentation (SSF) results showed an ethanol production of 143–152 mg/g biomass by using H2SO4/NaOH microwave assisted pretreatment, which is 7 times higher than that of untreated Miscanthus. Biomass morphology was studied by SEM, showing temperature has a strong influence on lignin removal process, as different lignin deposits were observed. At the temperature of 180 °C, NaOH pretreated biomass presented highly exposed fibres, which is a very important biomass characteristic for improved enzymatic hydrolysis. Compared to conventional pretreatment, microwave assisted pretreatment is more energy efficient and faster, due to its unique heating mechanism leading to direct interaction between the polar part of biomass and electromagnetic field. The results of this work present promising potential for using microwave to assist biomass thermo-chemical pretreatment.

Microwave assisted acid and alkali pretreatment of <i>Miscanthus </i>biomas<i>s </i>for biorefineries

Miscanthus is a major bioenergy crop in Europe and a potential feedstock for second generation biofuels. Thermochemical pretreatment is a significant step in the process of converting lignocellulosic biomass into fermentable sugars. In this work, microwave energy was applied to facilitate NaOH and H2SO4 pretreatments of Miscanthus. This was carried out at 180 ℃ in a monomode microwave cavity at 300 W. Our results show that H2SO4 pretreatment contributes to the breakdown of hemicelluloses and cellulose, leading to a high glucose yield. The maximum sugar yield from available carbohydrates during pretreatment is 75.3% (0.2 M H2SO4 20 Min), and glucose yield is 46.7% under these conditions. NaOH and water pretreatments tend to break down only hemicellulose in preference to cellulose, contributing to high xylose yield. Compared to conventional heating NaOH/H2SO4 pretreatment, 12 times higher sugar yield was obtained by using microwave assisted pretreatment within half the time. NaOH pretreatments lead to a significantly enhanced digestibility of the residue, because the effective removal of lignin and hemicellulose makes cellulose fibres more accessible to cellulases. Morphological study of biomass shows that the tightly packed fibres in the Miscanthus were dismantled and exposed under NaOH condition. We studied sugar degradation under microwave assisted H2SO4 conditions. The results shows that 6-8% biomass was converted into levulinic acid (LA) during pretreatment, showing the possibility of using microwave technology to produce LA from biomass. The outcome of this work shows great potential for using microwave in the thermo-chemical pretreatment for biomass and also selective production of LA from biomass.

Side by Side Comparison of Chemical Compounds Generated by Aqueous Pretreatments of Maize Stover, Miscanthus and Sugarcane Bagasse

In order to examine the potential for coproduct generation, we have characterised chemical compounds released by a range of alkaline and acidic aqueous pretreatments as well as the effect of these pretreatments on the saccharification ability of the lignocellulosic material. Comparative experiments were performed using three biomass types chosen for their potential as second-generation biofuel feedstocks: maize stover, miscanthus and sugarcane bagasse. The release of lignin from the feedstock correlated with the residual biomass saccharification potential, which was consistently higher after alkaline pretreament for all three feedstock types. Alkaline pretreatment released more complex mixtures of pentose and hexose sugars into the pretreatment liquor than did acid pretreatment. In addition, complex mixtures of aromatic and aliphatic compounds were released into pretreatment liquors under alkaline conditions, in a temperature-dependent manner, but far less so under acidic conditions. We show that the three feedstocks characterised interact with the pretreatment conditions in a specific manner to generate different ranges of products, highlighting the need to tailor pretreatments to both the starting feedstock and desired outcomes.

Land use and second-generation biofuel feedstocks: The unconsidered impacts of Jatropha biodiesel in Rajasthan, India

Governments around the world see biofuels as a common solution to the multiple policy challenges posed by energy insecurity, climate change and falling farmer incomes. The Indian government has enthusiastically adopted a second-generation feedstock – the oilseed-bearing shrub, Jatropha curcas – for an ambitious national biodiesel program. Studies estimating the production capacity and potential land use implications of this program have typically assumed that the ‘waste land’ slated for Jatropha production has no economic value and that no activities of note will be displaced by plantation development. Here we examine the specific local impacts of rapid Jatropha plantation development on rural livelihoods and land use in Rajasthan, India. We find that in Jhadol Tehsil, Jatropha is planted on both government and private land, and has typically displaced grazing and forage collection. For those at the socioeconomic margins, these unconsidered impacts counteract the very benefits that the biofuel programs aim to create. The Rajasthan case demonstrates that local land-use impacts need to be integrated into decision-making for national targets and global biofuel promotion efforts.

Protecting Innovation: Genomics-Based Intellectual Property for the Development of Feedstock for Second-Generation Biofuels

One of the many controversies surrounding large-scale biofuel production is the diversion of land and other resources that might otherwise be used for food crops. Recent innovations will lead to a second generation of biofuel crops that can co-exist with food crops with little or no competition. Feedstocks from these bio-energy crops will be used to produce liquid fuel from cellulose, the most abundant polymer on the planet. Cell walls of higher plants are mainly composed of cellulose, hemicellulose, and lignin polymers. Cellulose and hemicellulose are polysaccharides with obvious value for biofuel production. However, lignin, while vital for plant growth and development, is widely known to negatively impact conversion efficiencies. Biomass pre-treatment, which is aimed at lignin removal, is not straightforward, and presents one of the major scientific and technical challenges and expenses associated with secondgeneration biofuel production. Scientific breakthroughs associated with altering the expression of key genes in the lignin biosynthetic pathway of biomass crops is a promising path toward solving this problem, and will likely impact the feedstock patent landscape in the near future. This review summarizes some of the recent and most important issued patents and patent applications associated with lignin-modification genes and methods of developing transgenic plants with altered lignin content and composition.