Advanced Biofuels Research Articles

Second-Generation Bio-Fuels: Strategies for Employing Degraded Land for Climate Change Mitigation Meeting United Nation-Sustainable Development Goals

Increased Greenhouse Gas (GHG) emissions from both natural and man-made systems contribute to climate change. In addition to reducing the use of crude petroleum’s derived fuels, and increasing tree-planting efforts and sustainable practices, air pollution can be minimized through phytoremediation. Bio-fuel from crops grown on marginal land can sustainably address climate change, global warming, and geopolitical issues. There are numerous methods for producing renewable energy from both organic and inorganic environmental resources (sunlight, air, water, tides, waves, and convective energy), and numerous technologies for doing the same with biomass with different properties and derived from different sources (food industry, agriculture, forestry). However, the production of bio-fuels is challenging and contentious in many parts of the world since it competes for soil with the growth of crops and may be harmful to the environment. Therefore, it is necessary to use wildlife management techniques to provide sustainable bio-energy while maintaining or even improving essential ecosystem processes. The second generation of bio-fuels is viewed as a solution to the serious issue. Agricultural lignocellulosic waste is the primary source of second-generation bio-fuel, possibly the bio-fuel of the future. Sustainable practices to grow biomass, followed by their holistic conversion into ethanol with desired yield and productivity, are the key concerns for employing renewable energy mix successfully. In this paper, we analyze the various types of bio-fuels, their sources, and their production and impact on sustainability.

The socio-economic impact assessment of biofuels production in South Africa: A rapid structured review of literature

Biofuels as a substitute for conventional aviation and motor vehicle fuels have received considerable global interest over the past decades mainly due to their perceived economic, social, and environmental benefits. Despite these economic benefits, most developing countries, including South Africa (SA), have yet to produce commercial biofuels. This study aims to inform South African policymakers. Prospective producers of biofuels about the potential socio-economic returns from producing biofuels at a commercial level through a structured rapid review of the literature differs from the peer-reviewed studies to date in South Africa, which focussed more on assessing the economic viability and environmental impacts of biofuels production. The systematic review methodology was used. About 48% of the published empirical studies reviewed integrated the socio-economic and environmental impact assessment, followed by studies that only examined the social impacts of biofuel (about 26%), about 15% of the studies examined economic impact only, and 11.54% examined the socio-economic impact. The results revealed that although the production of biofuels is associated with a positive socio-economic benefit, the biofuel industry is not viable without government support and the selling price of biofuel is not competitive relative to gasoline and petroleum alternatives. Lastly, the results revealed a need for more objective empirical studies in South Africa that can quantify the economy-wide implications of biofuels (especially second-generation biofuels) production. Only two (n = 2) of the 28 reviewed studies were conducted in South Africa from 28 studies reviewed. Both studies conducted in South Africa were feasibility studies focusing more on bioethanol; no study quantified the economy-wide impacts. The study recommends the implementation of the biofuels support mechanism by the government. Furthermore, amendments to the existing biofuels regulatory framework are recommended in order to support the production of advanced biofuels.

Catalytic pyrolysis of olive mill wastes towards advanced bio-fuels and bio-chemicals using metal oxide catalysts

Among the environmental challenges that Mediterranean countries have to address are the abundant amounts of olive mill wastewater (OMWW) produced by olive oil agro-industry, such as those found in Greece and Tunisia, which lead to significant land and water pollution. The most common disposal method of olive mill wastewater, includes storage ponds, where most of the water is evaporated, while the residual sludge (olive mill wastewater sludge, OMWWS) is sent to landfills. Fast pyrolysis of OMWWS was investigated as an alternative approach of valorizing this waste, leading to the production of high heating value biofuel (bio-oil). Extraction of polyphenolic compounds with bioactive properties from OMWWS was additionally explored in order to provide further added value to OMWWS, considered as a source of bioactively important polyphenolic compounds, prior its use as pyrolysis feedstock towards the production of green fuel. Pyrolysis of the treated OMWWS (after extraction) led to a considerable reduction of the bio-oil yield, however in both cases the bio-oil produced exhibits a very interesting composition (predominance of aliphatic hydrocarbons and small fractions of aromatic hydrocarbons and phenols) and sufficiently low oxygen content. Exploring the effect of either an acidic (ZSM-5) or a basic (MgO) catalyst on the yield and composition of the bio-oil produced during the catalytic pyrolysis of OMWWS we observed that yield and quality of the produced bio-oils strongly depended on the catalyst used. Thus, acidic ZSM-5 zeolite catalyzed cracking and aromatization reactions, resulting in a bio-oil enriched in aromatics, while basic MgO catalyzed decarboxylation of fatty acids yielding a bio-oil composed mostly of aliphatic hydrocarbons. In addition, Co-promoted catalysts (5% Co either on ZSM-5 or MgO) led to additional variation of bio-oil quality, mostly enhancing ketonization reactions. The effect of a series of Fe and Mn oxide catalysts, based on alumina, silica and magnesia supports, was also studied for the catalytic pyrolysis of OMWWS, mainly focusing on using low-cost catalytic materials. In addition, ferric oxide, aluminum oxide, magnesium oxide, and silicon oxide, are among the major components of red mud, an effective catalyst used in the pyrolysis of OMWWS. All of these Fe- or Mn- materials exhibit very promising in situ upgrading of pyrolysis vapors (retaining organics’ yield and improving produced bio-oil). Most of these materials also tend to favor ketonization reactions, a more or less preferred route among the studied catalysts, which seems to mainly relate with their multifunctional (both acidic and basic) character.

On-line reversed-phase liquid chromatography x supercritical fluid chromatography coupled to high-resolution mass spectrometry: A powerful tool for the characterization of advanced biofuels

Bio-oils obtained by thermochemical or biochemical conversion of biomass represent a promising source of energy to complement fossil fuels, in particular for maritime or air transport for which the use of hydrogen or electricity appears complicated. As these bio-oils are very rich in water and heteroatoms, additional treatments are necessary before they can be used as biofuel. In order to improve the efficiency of these treatments, it is important to have a thorough knowledge of the composition of the bio-oil. The characterization of bio-oils is difficult because they are very complex mixtures with thousands of compounds covering a very wide range of molecular weight and polarity. Due to the high degree of orthogonality between the two chromatographic dimensions, the on-line combination of reversed-phase liquid chromatography and supercritical fluid chromatography (on-line RPLC x SFC) can significantly improve the characterization of such complex matrices. The hyphenation was optimized by selecting, in SFC, the stationary phase, the co-solvent, the make-up solvent prior to high resolution mass spectrometry (HRMS) and the injection solvent. Additionally, a new interface configuration is described. Quality descriptors such as the occupation of the separation space, the peak shapes and the signal intensity were considered to determine the optimal conditions. The best results were obtained with bare silica, a co-solvent composed of acetonitrile and methanol (50/50, v/v), a make-up solvent composed of methanol (90%) and water (10%) with formic acid (0.1%), an addition of co-solvent through an additional pump for SFC separation in a 2.1 mm column, and an hydro-organic solvent as injection solvent. The optimized setup was used to analyze two microalgae bio-oils: the full bio-oil coming from hydrothermal liquefaction and Soxhlet extraction of microalgae, and the gasoline cut obtained after distillation of the full bio-oil. Results in on-line RPLC x SFC-qTOF were particularly interesting, with very good peak shapes and high reproducibility. Moreover, the high degree of orthogonality for microalgae bio-oils of RPLC and SFC was highlighted by the very large occupation of the separation space. Isomeric profiles of compound families could be obtained in RPLC x SFC-qTOF and many isomers not separated in SFC alone were separated in RPLC and vice versa, thus showing the complementarity of the two chromatographic techniques.

Integrated Approach to Spent Coffee Grounds Valorization in Biodiesel Biorefinery

With the increasing consumption of coffee beverages, an increased amount of food waste—spent coffee grounds (SCG)—is generated and disposed into landfills or combusted in incinerators. SCG are characterized as a highly polluting substance with partial toxicity due to the presence of caffeine, tannins, and polyphenols. It also contains 15% of oil on average, and its potential for biodiesel production is thus considerable. The aim of the presented work is to evaluate the possibility and technical potential of biodiesel production from the SCG oil (SCGO) by esterification and transesterification reaction. According to the characterization of the studied SCGO, this stream must be adjusted and purified to be utilized in the existing biodiesel production plant. Fatty acids (FA) represent 85.85% of the SCGO, with two dominant FAs—linoleic and palmitic acids. The necessity of removal and disposal of unsaponifiable matter, which accounts for 15% of the SCGO content, must be highlighted when producing biodiesel from the SCG. The objective of this research was the comparison of different biodiesel production processes, where a two-step transesterification process has been identified as the most successful method for biodiesel production from the SCGO with the highest ester content of 89.62% and the lowest content of unsaponifiable and unidentified matter in the final product. The novelty of the analyses is a characterization of the d unsaponifiable matter present in the SCGO, and the article highlights the importance of progression to be considered when evaluating the technical potential of the SCG biodiesel production integrated into a biorefinery. Nevertheless, the SCG biodiesel can contribute to fulfilling the mandatory share of advanced biofuel in the fuel energy mix given by national legislation and contribution to the circular economy approach of biorefineries.

From Secondary Biomass to Bio-Methanol through CONVERGE Technology: An Environmental Analysis

Owing to residual biomass availability, the share of advanced biofuels produced from secondary biomass is forecasted to increase and significantly contribute towards achieving net-zero emissions. The current work investigates bio-methanol production through a new process configuration designed to improve the environmental performance when compared to the state-of-the art technologies (Base Case). The environmental evaluation is conducted according to the Life Cycle Assessment (LCA) methodology. ReCiPe was employed as an impact assessment method with the aid of GaBi software. Depending on the plant geographical location, wooden biomass and exhausted olive pomace were evaluated as biomass sources. A scenario analysis targeting different energy sources was performed as well. The outcome of the environmental evaluation highlights a better performance in eight of a total of nine impact categories studied in the wooden biomass scenarios compared to the exhausted olive pomace. Moreover, two of the CONVERGE technology cases were compared against the Base Case. As the results show, CONVERGE technology registers a lower score in at least six of the impact categories studied. Concerning the total CO2 emissions, CONVERGE exhibits a better performance compared to the Base Case, if the additional amount of CO2 is either stored, sold as a by-product or vented into the atmosphere.

Biochemical Methane Potential of Mechanically and Enzymatically Pretreated Solid Olive Mill Waste

Olive cake, the solid byproduct of three-phase centrifugation olive oil production, has a high organic and polyphenol content, rendering it an environmental threat when landfilled as well as limiting its animal feed potential. This residue can be a good candidate for biomethane production due to its rich polysaccharide content (pectin, hemicellulose, and cellulose). Two strategies were compared to maximize biomethane production: destoning (i.e., removal of the seed fragments via mechanical means) and enzymatic pretreatment of the pulp. After 30 days of batch anaerobic digestion at 35 °C, both enzymatically pretreated and destoned olive cakes produced similar amounts of methane (~295 mL CH4/g volatile solids (VS)), 42% more than the control. A comparison of olive cake’s biomethane yields with a broad range of agricultural residues in the literature demonstrated its suitability for biomethane production. Additionally, the digestate recovered from the anaerobic digestion of olive cake had high Kjeldahl nitrogen contents (3.6%, db) and low polyphenol concentrations (0.02 mg gallic acid equivalent (GAE)/g), qualifying it as an ingredient for soil amendment. This study demonstrated olive cake can be diverted from landfills for second-generation biofuel production, and that the resulting digestate may have value for soil amendment.

The crystalline structure transition and hydrogen bonds shift determining enhanced enzymatic digestibility of cellulose treated by ultrasonication

Global energy issue raised the necessity to develop second-generation biofuels, and biorefinery of cellulosic biomass becomes a promising solution. Various pretreatments were used to overcome the cellulose nature of recalcitrance and improve the enzymatic digestibility, but the lack of mechanism understanding hindered the development of efficient and cost-effective technologies of cellulose utilization. Using structure-based analysis, we demonstrate that the improved hydrolysis efficiency caused by ultrasonication was ascribed to the changed cellulose properties rather than the increased dissolubility. Further, isothermal titration calorimetry (ITC) analysis suggested that enzymatic digestion of cellulose is an entropically favored reaction driven by hydrophobic forces other than an enthalpically favored reaction. The changes in cellulose properties and thermodynamic paramenters due to ultrasonication accounted for the improved accessibility. Ultrasonication-treated cellulose showed porous, rough and disordered morphology, accompanying with the loss of crystalline structure. Despite the unaffected unit cell structure, ultrasonication expanded the crystalline lattice by increasing grain sizes and average cross-sectional area, resulting in the transformation from cellulose I to cellulose II, with the decreased crystallinity, better hydrophilicity and increased enzymatic bioaccessibility. Furthermore, FTIR combined with two-dimensional correlation spectroscopy (2D-CoS) verified that the sequential shift of hydroxyl group and intramolecular/intermolecular hydrogen bonds, the functional groups governing cellulose crystal structure and stability, accounted for the ultrasonication-induced transition of cellulose crystalline structure. This study provides a comprehensive picture of cellulose structure and property response caused by mechanistic treatments and will open up avenues to develop novel pretreatments for efficient utilization.

Production of cellulolytic enzymes from microorganisms isolated from coconut fiber

The worldwide production of microbial enzymes is generally limited by the cost of the substrate used for the cultivation of microorganisms. Thinking of a low-cost and abundant lignocellulosic substrate, coconut fiber is an alternative because it is rich in cellulose, hemicellulose, and lignin, presenting itself as a promising raw material for the production of an enzyme cocktail, which can be used in the production of second-generation biofuels. The objective of this work was to produce cellulolytic enzymes from microorganisms isolated from coconut fiber. In the production of the enzyme, the kinetic profile of the enzymatic complex was evaluated, analyzing the effects of moisture content, temperature, and pH during solid-state fermentation of coconut fiber, using a microorganism isolated from the bagasse itself. Statistica software was used to evaluate the enzyme complex production parameters. Statistical results indicated that the best humidity, temperature, and pH conditions were 80%, 30°C and 3, respectively, with activities of 119.93 U/g CMCase (endoglucanase) and 89.32 U/g FPase (total cellulases ) over a period of 48 h.

Supporting Second Generation Biofuel Development: Thermophilic Anaerobic Digestion of Vinasse for Harmonizing with Molasses Based Bioethanol Plant Capacity

First-generation biofuel is environmental quandary due to its impact to the forest conversion into plantation area. Not only environmental sector, first-generation biofuel has other issues on socioeconomic sector. It consumes crops as its feedstock which will be a conflict between food and energy source. This conflict will impact the vulnerable people as the raising food price. Molasses-based bioethanol is second-generation biofuel which more beneficial from environmental, economic, and social aspect. Molasses-based bioethanol production process generates waste named vinasse. Vinasse can’t be directly discharged to the environment due to its high organic matter concentration which is harmful to the waterbody, soil, and air. On the other hand, high organic matter contained in vinasse can be converted into biogas and is higher potential for molasses-based bioethanol plant. This study was preliminary study for processing vinasse using thermophilic anaerobic digestion specifically by temperature direct escalation and starvation method to the mesophilic originated inoculum. The result shows robust performance of thermophilic microbia which is an averment of compatible method for enriching thermophilic anaerobic microbia in mesophilic originated inoculum.

A comparative analysis of second-generation biofuels and its potentials for large-scale production in arid and semi-arid regions

This study compares the pyrolysis products from eight different feedstocks of potential availability in arid and semi-arid regions, namely, post-consumption food waste, biosolids (anaerobically digested and undigested sewage sludges), segregated fruits and vegetable waste, animal manure, date palm waste, and halophyte plant (Salicornia bigelovii seed and seedless-plant). Food waste, Salicornia bigelovii seed, and undigested sludge produced the highest bio-oil yield, 38.0 %, 35.3 %, and 32.5 %, respectively. The bio-oils from food waste and Salicornia bigelovii seed were rich in acidic compounds. The former has the highest calorific value (34.7 MJ kg−1), while the latter is the lowest due to a significant amount of water (29.9 mass%). The biosolids produced bio-oil rich in alcohols and esters, turning it towards high alkalinity (pH > 9). The biochar from animal manure and biosolids has the lowest calorific value (<10.0 MJ kg−1) and the least potential for soil amendment and carbon sequestration due to poor stability, low fixed carbon, and significantly high ash content in the feed (>39 mass%). The gas from digested biosolid has the highest calorific value (>38.9 MJ kg−1), benefiting from the presence of high H2 content (21.2 mass%). Analysis of the potential implementation of the eight feedstocks for pyrolysis in an arid region indicates that food waste is the most promising due to its superior bio-oil quality, higher conversion efficiency, abundant availability, and the possibility of low-cost drying.

Which crop has the highest bioethanol yield in the United States?

Annual U.S. production of bioethanol, primarily produced from corn starch in the U.S. Midwest, rose to 57 billion liters in 2021, which fulfilled the required conventional biofuel target set forth by the Energy Independence and Security Act (EISA) of 2007. At the same time, the U.S. fell short of the cellulosic or advanced biofuel target of 79 billion liters. The growth of bioenergy grasses (e.g., Miscanthus and switchgrass) across the Central and Eastern U.S. has the potential to feed enhanced cellulosic bioethanol production and, if successful, increase renewable fuel volumes. However, water consumption and climate change and its extremes are critical concerns in corn and bioenergy grass productivity. These concerns are compounded by the demands on potentially productive land areas and water devoted to producing biofuels. This is a fundamental Food-Energy-Water System (FEWS) nexus challenge. We apply a computational framework to estimate potential bioenergy yield and conversion to bioethanol yield across the U.S., based on crop field studies and conversion technology analysis for three crops—corn, Miscanthus, and two cultivars of switchgrass (Cave-in-Rock and Alamo). The current study identifies regions where each crop has its highest yield across the Center and Eastern U.S. While growing bioenergy grasses requires more water than corn, one advantage they have as a source of bioethanol is that they control nitrogen leaching relative to corn. Bioenergy grasses also maintain steadily high productivity under extreme climate conditions, such as drought and heatwaves in the year 2012 over the U.S. Midwest, because the perennial growing season and the deeper and denser roots can ameliorate the soil water stress. While the potential ethanol yield could be enhanced using energy grasses, their practical success in becoming a potential source of ethanol yield remains limited by socio-economic and operational constraints and concerns regarding competition with food production.

Microbial Enzyme Systems in the Production of Second Generation Bioethanol

The primary contributor to global warming has been the careless usage of fossil fuels. Urbanization’s threat to the depletion of these resources has made it necessary to find alternatives due to the rising demand. Four different forms of biofuels are now available and constitute a possible replacement for fossil fuels. The first generation of biofuels is generated from the edible portion of biomass, the second generation is made from the non-edible portion of biomass, the third generation is made from algal biomass, and the fourth generation is made using molecular biology to improve the algal strain. Second-generation biofuels are extremely important because they are derived from non-edible biomass, such as agricultural and agro-industrial wastes rich in cellulose, hemicellulose, pectin, and starch impregnated with lignin, and are hydrolyzed after delignification by physio-chemical or biological pretreatments using ligninases. The enzymes involved in the hydrolysis of feedstocks for the production of second-generation bioethanol, a highly acceptable biofuel, are discussed in this article. Furthermore, the article discusses various fermentation technologies as well as significant developments in second-generation biofuel production by combining various microbial enzyme systems.

Pyrolysis of Waste Biomass: Technical and Process Achievements, and Future Development—A Review

Pyrolysis has been applied in the human economy for many years, and it has become a significant alternative to the production of chemical compounds, including biofuels. The article focuses mostly on recent achievements in the technical and processing aspects of pyrolysis. The aim of the review is to present the latest research on the process of waste biomass pyrolysis to fuel production. The paper describes the mechanisms of the pyrolysis process, composition, and properties of the obtained fractions, namely pyrolysis gas, bio-oil, and biochar. Additionally, the technical aspects of the pyrolysis process are mentioned, with particular attention to the construction of the reactors. The process of waste biomass pyrolysis allows for obtaining many chemical compounds (second-generation biofuels). Optimization of the pyrolysis process allows obtaining the desired products that are applied in the chemical industry, energy, and transport. The application of pyrolysis gas, oil, and biochar as valuable chemical compounds are related to the intensifying effects of climate change, biofuel production, and waste management in accordance with the principles of sustainable development. In recent years, there has been large-scale research into the use of renewable energy sources through pyrolysis. This will make it possible to significantly reduce the carbon footprint and produce second-generation biofuels in a sustainable manner. Current research into the mechanisms of pyrolysis processes is promising, and will therefore provide access to clean and low-cost compounds that will have broad applications in the energy, chemical, agricultural, and transportation industries.

Integration of third generation biofuels with bio-electrochemical systems: Current status and future perspective.

Biofuels hold particular promise as these can replace fossil fuels. Algae, in particular, are envisioned as a sustainable source of third-generation biofuels. Algae also produce several low volume high-value products, which enhance their prospects of use in a biorefinery. Bio-electrochemical systems such as microbial fuel cell (MFC) can be used for algae cultivation and bioelectricity production. MFCs find applications in wastewater treatment, CO2 sequestration, heavy metal removal and bio-remediation. Oxidation of electron donor by microbial catalysts in the anodic chamber gives electrons (reducing the anode), CO2, and electrical energy. The electron acceptor at the cathode can be oxygen/NO3 -/NO2 -/metal ions. However, the need for a continuous supply of terminal electron acceptor in the cathode can be eliminated by growing algae in the cathodic chamber, as they produce enough oxygen through photosynthesis. On the other hand, conventional algae cultivation systems require periodic oxygen quenching, which involves further energy consumption and adds cost to the process. Therefore, the integration of algae cultivation and MFC technology can eliminate the need of oxygen quenching and external aeration in the MFC system and thus make the overall process sustainable and a net energy producer. In addition to this, the CO2 gas produced in the anodic chamber can promote the algal growth in the cathodic chamber. Hence, the energy and cost invested for CO2 transportation in an open pond system can be saved. In this context, the present review outlines the bottlenecks of first- and second-generation biofuels along with the conventional algae cultivation systems such as open ponds and photobioreactors. Furthermore, it discusses about the process sustainability and efficiency of integrating algae cultivation with MFC technology in detail.

CeO2-based oxygen storage capacity materials in environmental and energy catalysis for carbon neutrality: extended application and key catalytic properties

ABSTRACT Reducing carbon dioxide emissions is one of the largest energy and environmental challenges currently faced globally. To achieve carbon neutrality, the development of new technologies and simultaneous improvement of conventional technologies are required. Catalysis, which determines the success or failure and efficiency of the process, is at the center of addressing these problems. Innovative advancements in catalysis have been accomplished through the extensive research on catalytic materials. Oxygen storage materials with oxygen storage capacity (OSC) have been widely applied in supports and active cocatalysts for energy and environmental catalytic applications. This review provides knowledge on the extended applications (reforming, water-gas shift reaction, and partial oxidation of methane (POM) for high-value-added chemicals, including hydrogen production, deoxygenation of fatty acids for second-generation biofuel production, selective catalytic reduction of NO x with NH3, hydrocarbon (HCs) oxidation for emission control, CO oxidation for vehicle exhaust control and purification of gaseous product fuel, and soot oxidation for the removal of motor-type pollutants) of these materials, which are mainly used as three-way catalysts (TWC) in automotive catalysis, to the carbon-neutral field. In particular, this study focuses on the physico-chemical properties that are closely synergistic with OSC, such as reducibility, dispersion, surface acid/base properties, and physical properties, such as surface structure or morphology.

Moderate pressure boosts the aromatization activity of HZSM-5 zeolite during catalytic pyrolysis of lignocellulosic materials

Lignocellulose pyrolysis has been deeply investigated in the past years as a potential route for the production of advanced biofuels and biochemicals from residues and wastes. However, the effect of pressure has rarely been addressed in catalytic pyrolysis processes. Accordingly, the current work reports a comprehensive study on the pressure influence during the catalytic pyrolysis of different lignocellulosic materials (oak wood, cellulose, hemicellulose, and lignin) using nanocrystalline HZSM-5 zeolite as a catalyst and a downflow fixed-bed reactor. In thermal pyrolysis tests, pressure increase affects negatively the bio-oil* (organic components in the liquid products) since it reduces its yield in favor of the production of char and gases. However, in the case of the catalytic pyrolysis tests, working under moderate pressure (10 bar) has very positive effects on bio-oil upgrading, minimizing its oxygen concentration (< 10 wt.%) and sharply increasing the carbon yield of aromatic hydrocarbons, while the undesirable coke deposited on the catalyst surface can be even reduced. This finding denotes the occurrence of a remarkable synergistic effect between the pyrolysis pressure and the catalyst loading. These outstanding results are attributed to a more efficient activity of the zeolite under mild pressurization since both oxygenated species and light olefins are more strongly adsorbed over the catalyst surface, facilitating their subsequent transformation into aromatic hydrocarbons. The sharp enhancement of the deoxygenation and aromatization activity does not involve higher coke deposition over the zeolite surface, thus attenuating one of the major limitations of the lignocellulose catalytic pyrolysis process.

Second Generation Bioethanol Production from Soybean Hulls Pretreated with Imidazole as a New Solvent

Soybean hulls (SH) are the main industrial waste from soybean processing, representing 5–8% of the whole grain. Imidazole was employed for the hydrothermal pretreatment of SH and further bioethanol production. Different pretreatment temperatures (120 and 180 °C) and times (1 and 3 h) were tested. Lignin removal and glucose yield were significantly influenced by temperature. After 48 h of enzymatic hydrolysis of imidazole-treated SH (120 °C, 1 h), 32.7 g/L of glucose and 9.4 g/L of xylose were obtained. A maximum bioethanol yield of 78.9% was reached after 12 h of fermentation by Saccharomyces cerevisiae using SH enzymatic hydrolysate. Imidazole appears to be a potential alternative to pretreat lignocellulosic wastes such as SH for the production of second-generation biofuels and other biomolecules.

Biomass characterization of wild and cultivated cardoon accessions and estimation of potential biofuels production

Cardoon is considered an interesting raw material to obtain second-generation biofuels, due to its perennial culture condition and its rare use as food. In addition, cardoon, being a rustic species, requires few inputs and has fast growth and high lignocellulosic biomass production. However, despite its large genetic variability worldwide, both cardoon botanical varieties were subject only to few (cultivated cardoon)/zero (wild cardoon) breeding programs. The aims of this study were (I) to characterize biomass quality and quantity of genotypes of wild and cultivated cardoon in order to produce different types of biofuels and (II) to identify the most promising accessions to be included in breeding programs for bioenergy characteristics or to be incorporated in the local agro-productive system. The performance of twelve Cynara cardunculus L. accessions (six cultivated cardoons and six wild cardoons) was compared through biometric, chemical, and energetic characteristics. Moreover, the potential bioethanol and biomethane yields and the energy potentially generated from direct combustion were calculated for each botanical variety. Significant differences were found between botanical varieties for several biometric traits, but not in chemical traits except for ash content. Results indicate that cardoon biomass, especially cultivated cardoon, has characteristics that make this species a promising candidate to be grown for energy purposes under very low crop inputs in the local edapho-climatic conditions. In addition, our screening identified an accession that stands out based on yield, biomass composition, and potential to produce different types of biofuels/bioenergy.

Control in Advanced Biofuels Synthesis via Alcohol Upgrading: Catalyst Selectivity to n‐Butanol, sec‐Butanol or Isobutanol

AbstractRuthenium complexes with tetradentate PNNP donor ligands demonstrate a marked change in selectivity compared to analogous bis bidentate PN complexes in Guerbet catalysis, producing mixtures of n‐butanol (17 %), sec‐butanol (14 %) and ethyl acetate (66 %) rather than the usual 90 %+ selectivity to n‐butanol. Tridentate PNP ruthenium complexes such as [Ru(H)(Cl)(CO)(Ph2PCH2CH2NHCH2CH2PPh2)] also produce sec‐butanol and, in optimized conditions (120 °C, 10 mol% NaOEt base), achieve 71 % selectivity to this butanol isomer. The same tri‐ and tetradentate complexes are efficient catalysts for the conversion of methanol/ethanol mixtures to isobutanol (up to 97 % selectivity). In this way, judicious choice of ligand within this general catalyst family allows selectivity to three butanol isomers of interest as fuel molecules.