A Comprehensive Review on Oil Extraction and Biodiesel Production Technologies

Cellulase production by Aspergillus fumigatus A4112 and the potential use of the enzyme in cooperation with surfactant to enhance floating oil recovery and methane production from palm oil mill effluent

This research performed cellulase production by Aspergillus fumigatus A4112 and evaluated its potential use in palm oil mill effluent (POME) hydrolysis to recover oil simultaneously with the generation of fermentable sugar useful for biofuel production under non-sterilized conditions. Empty fruit bunch (EFB) without pretreatment was used as carbon source. The combination of nitrogen sources facilitated CMCase production. The maximum activity (3.27 U/mL) was obtained by 1.0 g/L peptone and 1.5 g/L (NH4)2SO4 and 20 g/L EFB at 40 °C for 7 days. High level of FPase activity (39.51 U/mL) was also obtained. Interestingly, the enzyme retained its cellulase activities more than 60% at ambient temperature over 15 days. In enzymatic hydrolysis, Triton X-100 was an effective surfactant to increase total oil recovery in the floating form. High yield of reducing sugar (50.13 g/L) and 21% (v/v) of floating oil was recoverable at 65 °C for 48 h. Methane content of the raw POME increased from 41.49 to 64.94% by using de-oiled POME hydrolysate which was higher than using the POME hydrolysate (59.82%). The results demonstrate the feasibility of the constructed process for oil recovery coupled with a subsequent step for methane yield enhancement in biogas production process that benefits the palm oil industry.

Experimental Investigation of the Effect of Surfactant-Polymer Flooding on Enhanced Oil Recovery for Medium Crude Oil

High technical and financial risks are involved in exploring and exploiting new fields; hence, greater focus has placed on the development of environmentally friendly, cost-effective, and enhanced oil recovery (EOR) options for existing fields. For reservoirs producing high-density crudes and those with high interfacial tensions, water flooding is usually less effective due to density differences-hence the advent of polymer and surfactant flooding. For cost-effective and eco-friendly EOR solutions, a biopolymer and a surfactant synthesized from Jatropha seeds are used in this study to determine their effectiveness in increasing the oil recovery during core flooding analysis. The experiment involved an initial water flooding that served as the base cases of three weight percentages of polymers and polymeric surfactant solutions. The results for the polymer flooding of 1 wt%, 1.5 wt%, and 2 wt% showed an incremental oil recovery in comparison to water flooding of 16.8%, 17%, and 26%, while the polymeric surfactant mixtures of 5 wt% of surfactant and 1 wt%, 1.5 wt%, and 2 wt% of a polymer recorded 16.5%, 22.3%, and 28.8%, and 10 wt% of surfactant and 1 wt%, 1.5 wt%, and 2 wt% of a polymer recorded incremental oil recoveries of 20%, 32.9%, and 38.8%, respectively.

Biodiesel production and characteristics from waste frying oils: sources, challenges, and circular economic perspective

Biodiesel serves as a viable alternative to traditional diesel due to its non-toxicity, biodegradability, and lower environmental footprint. Among the diverse edible and inedible feedstocks, waste frying oil emerges as a promising and affordable feedstock for biodiesel production. Commonly waste frying oils include those derived from palm, corn, sunflower, soybean, rapeseed, and canola. The primary challenge related to biodiesel production technologies is the high production cost, which poses a significant barrier to its widespread adoption. Thus, refining the production techniques is essential to enhance yield, reduce capital expenditure, and curtail raw material expenses. An examination of the research focusing on feedstock availability, production, hurdles, operational expenditures, and future potential is pivotal for identifying the most economically and technically viable solutions. This paper critically reviews such research by exploring feedstock availability, production techniques, challenges, and costs intrinsic to biodiesel synthesis. It also underscores the economic feasibility of biodiesel production, shedding light on the pivotal factors that influence profitability, especially when leveraging waste frying oils. Through an in-depth understanding of these considerations, optimal production and feedstock choices for biodiesel production can be identified. Addressing cost and production bottlenecks could potentially enhance the economic viability of waste frying oil-based biodiesel, thus fostering both environmental sustainability and more extensive adoption of biodiesel as an environmental-friendly fuel in the future.

Investigation of NaCl-Modified Graphitic Carbon Nitride for Efficient Biodiesel Production from Waste Oil via Transesterification: A Box-Behnken Design Approach

NaCl-modified graphitic carbon nitrides (GCN) were applied in the base-catalyzed transesterification of recovered oil. GCN has been seen as a prospective heterogeneous catalyst for transesterification, but pristine-GCN has a narrow range of applications because of its weak basic sites and small surface area. To overcome these defects, NaCl-modified GCN was prepared through the co-thermal polymerization of NaCl with urea. The doping of NaCl generated C≡N and Na-N species, which enhanced the basicity of the catalyst. Meanwhile, with the assistance of NaCl, GCN was decomposed and produced a large number of small pores of hundreds of nanometers, which contributed to the increase in specific surface area. In addition, the effects of transesterification parameters and their interactions on biodiesel yields were investigated by using Box-Behnken design, and the reaction conditions were optimized. A high biodiesel yield of 93.05% was achieved under the optimal conditions.

Trends and social aspects in the management and conversion of agricultural residues into valuable resources: A comprehensive approach to counter environmental degradation, food security, and climate change

The circular economy is essential as it encourages the reuse and recycling of resources while reducing waste, which ultimately helps to reduce environmental pollution and boosts economic efficiency. The current review highlights the management of agricultural and livestock residues and their conversion into valuable resources to combat environmental degradation and improve social well-being. The current trends in converting agricultural residues into useful resources emphasize the social benefits of waste management and conversion. It also emphasizes how waste conversion can reduce environmental degradation and enhance food security. Using agricultural residues can increase soil health and agricultural output while reducing pollution, greenhouse gas emissions, and resource depletion. Promoting sustainable waste-to-resource conversion processes requires a combination of strategies that address technical, economic, social, and environmental aspects. These multiple strategies are highlighted along with prospects and considerations.

Study on the Formation Mechanism of Cold-Rolled Sludge and the Biodiesel Production from Sludge

Cold-rolled sludge (CRS) has become a challenge due to its large volumetric capacity and high toxicity and is difficult to be degraded under natural conditions. This article aims to explore the feasibility of the solvent extraction method for recovering oil and fat from CRS and utilizing it as a raw material to prepare biodiesel with the application of a homogeneous catalyst H2SO4 to mediate esterification and transesterification. The formation mechanism of CRS was proposed with its detailed analysis; hydroxylates were preferentially adsorbed on the metal surface by hydrogen bonds, and free fatty acids were hooked by carbon chains to form a second layer of adsorption. It revealed the reason for the residual oil content on the surface of the extracted solid phase. Experimental data represented an optimum biodiesel yield of 96.5% at a catalyst dosage of 25 wt %, a reaction time of 24 h, a methanol-to-oil molar ratio of 70:1, and a reaction temperature of 60 °C. The main properties of the biodiesel were tested and confirmed to meet ASTM D6751 standards.

Utilization of vanillin to prepare sulfated Calix[4]resorcinarene as efficient organocatalyst for biodiesel production based on methylation of palmitic acid and oleic acid

Recently, biodiesel production from palm oils has been thoroughly investigated to substitute crude oil due to its scarcity. However, the biodiesel production process is time-consuming due to its slow kinetics; thus, concentrated sulfuric acid has been used to fasten the reaction process in some industries. Unfortunately, sulfuric acid is a toxic, corrosive, and non-environmentally friendly catalyst. In this study, we prepared sulfated Calix[4]resorcinarene derived from vanillin as an efficient organocatalyst to replace sulfuric acid. The catalytic activity of sulfated Calix[4]resorcinarenes was evaluated through the methylation of palmitic acid and oleic acid as model compounds due to their abundant amounts in palm oil. The Calix[4]resorcinarene and sulfated Calix[4]resorcinarenes have been obtained through a one-pot reaction in 71.8-98.3% yield. Their chemical structures were confirmed by using FTIR, NMR and HRMS spectrometry analyses. The results showed that the sulfated Calix[4]resorcinarene exhibited high catalytic activity for methyl palmitate and methyl oleate productions in 94.8 ± 1.8 and 97.3 ± 2.1% yield, respectively, which was comparable to sulfuric acid (96.3 ± 1.8 and 95.9 ± 2.5%). The optimum condition was achieved by using 0.020 wt equivalent of organocatalyst for 6 h reaction process at 338 K. The methylation of palmitic acid and oleic acid fits well with the first-order kinetic model (R² = 0.9940-0.9999) with a reaction rate constant of 0.6055 and 1.1403 h^-1, respectively. Further investigation reveals that the hydroxyl group of vanillin plays a pivotal role in the organocatalytic activity of sulfated Calix[4]resorcinarene.

A SWOT-AHP analysis on biodiesel as an alternative future marine fuel

Alternative fuels especially those produced in a green way are essential for meeting supplying the world's growing energy needs. Biodiesel is becoming more prominent to meet international maritime organization regulations, minimize reliance on fossil fuels, and lessen the rising harmful emissions in the maritime sector. Four different generations have been investigated in the production stage in which a wide range of fuel types have existed including biodiesel, bioethanol, and renewable diesel. To investigate all facets of biodiesel usage as a marine fuel, the SWOT-AHP method is utilized in this paper in which 16 maritime experts with an average of 10.5 years of experience participated. SWOT factors and sub-factors have been developed in light of the literature review focused on biomass and alternative fuels. The AHP method is utilized for data acquisition from specified factors and sub-factors according to their superiority to each other. The analysis demonstrates the main factors 'PW and sub-factors' IPW values, and CR values to calculate the local and global rank of factors. Results highlighted that "Opportunity" has the highest prominence among the main factors; however, "Threats" remain at the lowest level. Moreover, "Tax privilege on green and alternative fuels supported by the authorities" (O4) is the one with the highest weight compared to the other sub-factors. Noteworthy energy consumption will be fulfilled in the maritime industry in addition to the development of new-generation biodiesel and other alternative fuels. This paper will be a quite valuable resource for experts, academics, and industry stakeholders to lessen the ambiguity around biodiesel.

Graphical abstract

Sustainable production of biofuels and bioderivatives from aquaculture and marine waste

The annual global fish production reached a record 178 million tonnes in 2020, which continues to increase. Today, 49% of the total fish is harvested from aquaculture, which is forecasted to reach 60% of the total fish produced by 2030. Considering that the wastes of fishing industries represent up to 75% of the whole organisms, the fish industry is generating a large amount of waste which is being neglected in most parts of the world. This negligence can be traced to the ridicule of the value of this resource as well as the many difficulties related to its valorisation. In addition, the massive expansion of the aquaculture industry is generating significant environmental consequences, including chemical and biological pollution, disease outbreaks that increase the fish mortality rate, unsustainable feeds, competition for coastal space, and an increase in the macroalgal blooms due to anthropogenic stressors, leading to a negative socio-economic and environmental impact. The establishment of integrated multi-trophic aquaculture (IMTA) has received increasing attention due to the environmental benefits of using waste products and transforming them into valuable products. There is a need to integrate and implement new technologies able to valorise the waste generated from the fish and aquaculture industry making the aquaculture sector and the fish industry more sustainable through the development of a circular economy scheme. This review wants to provide an overview of several approaches to valorise marine waste (e.g., dead fish, algae waste from marine and aquaculture, fish waste), by their transformation into biofuels (biomethane, biohydrogen, biodiesel, green diesel, bioethanol, or biomethanol) and recovering biomolecules such as proteins (collagen, fish hydrolysate protein), polysaccharides (chitosan, chitin, carrageenan, ulvan, alginate, fucoidan, and laminarin) and biosurfactants.

The effect of high altitude environment on diesel engine performance: Comparison of engine operations in Hangzhou, Kunming and Lhasa cities

The all-area operating performance of the vehicles requires the development of diesel engines that can operate at high altitudes without significant performance deterioration. Prior to optimizing the efficiency and emissions of highland engines, there is a necessity to investigate the underlying causes of engine performance degradation. The purpose of this paper was to study the in-cylinder activities occurring in the combustion chamber of diesel engines at high altitudes, which can help explain the effect of altitude on engine efficiency and emissions of concern to the customer. Specifically, a turbocharged direct injection compression ignition engine was operated at a constant engine speed and load, but at different altitudes. The theoretical analyses based on experimental data suggested that the mismatch between air and diesel quantities caused by the high altitude atmosphere led to the engine combustion deterioration. Specifically, the lower gas density at high altitudes during fuel injection resulted in a reduction of the injection angle and an enhancement of the penetration capability. In addition, the rise in altitude extended the ignition delay, which increased the fuel fraction mixed with air in the premixed combustion stage and raised the pressure rise rate. Moreover, at high altitudes, the reduction in excess air ratio and increased possibility of wall impingement of the fuel droplets resulted in uneven mixture concentration distribution and reduced air utility. Accordingly, combustion deterioration occurred in the combustion chamber of the plateau engines, which reduced energy release during main mixing-controlled combustion, lowered combustion efficiency, increased exhaust energy, and raised engine-out incomplete combustion emissions. All these effects resulted in a decrease in engine thermal efficiency of ∼6.5% and an increase in soot emissions of ∼4.2 times from Hangzhou to Lhasa city for the engine and operating conditions investigated in this study. Consequently, engines operating in highland areas need to be optimized in terms of efficiency and emissions.

Rheological and Physicochemical Analysis of Nonedible Oils Used for Biodiesel Production

Rheological and physicochemical characteristics of edible oils used for biodiesel production are well established; nonetheless, the rheological and physicochemical characteristics of nonedible oils are yet to be established. The present study therefore focuses on rheological and physicochemical characterization of nonedible vegetable oils that can be used as biodiesel feedstock. The selected vegetable oils studied include cashew nut shell liquid (CNSL), castor oil (CO), Croton megalocarpus oil (CMO), Podocarpus usambarensis oil (PUO), and Thevetia peruviana oil (TPO). Physicochemical parameters analyzed were free fatty acids, acid value, saponification value, peroxide value, iodine value, specific gravity, and moisture content using methods by the Association of Official Analytical Chemists (AOAC). Rheological properties were analyzed using a VT-550 Thermo Haake Viscotester operated by the Rheowin 3 Job Manager software. The preset parameters in the Viscotester were shear rate and temperature. The shear rate increased uniformly from 5 to 100 s^-1 at the temperature range of 30-60 °C. The experimental data were fitted into rheological models of Newton, Bingham, Ostwald-de Waele (power-law), and Herschel-Bulkley using Rheowin 3 Data Manager. The oil yield was 29-65%, highlighting the feedstock's potential for commercial biodiesel production. At a constant temperature, all oil samples exhibited a Newtonian flow behavior. In contrast to edible oils, nonedible oils exhibited high shear stress, emphasizing the reconstruction of new appropriate designs of production systems. The rheological models appropriate to represent the flow behavior of the samples were the Newton and Ostwald-de Waele models, with a fit of R ² = 0.990-1.000.

Treatment of Saussurea heteromalla for biofuel synthesis using catalytic membrane reactor

Membrane technology has been adopted as a prospective and promising alternative to the standard technology used for biodiesel production since the time when it had some limitations. During this research project, the inedible seed oil generating feedstock known as Saussurea heteromalla was put through a biodiesel production process that utilized membrane technology with an effort to increase the yield of methyl ester. The transesterification process was mediated by zirconium oxide nanoparticles that were generated using an aqueous extract of Portulaca oleracea leaf. With an oil to methanol ratio of 1:9, a catalyst concentration of 0.88 (wt. %), temperature of 87 °C, and reaction time of 180 min, the highest possible biodiesel yield of 93% was achieved. The findings of the catalyst characterization demonstrated the purity of the zirconium oxide nano particles and their nanoscale nature with average particle size of 31 nm. Using gas chromatography and mass spectrometry (GC/MS), an examination of biodiesel revealed the presence of four different peaks of methyl esters. Using Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance, we were able to verify that the production of methyl esters in the biodiesel sample was successful (NMR). Zerconium oxide nanoparticles were found reusable up to five consecutive cycles of transesterification. The fuel-related properties of methyl ester have been determined and are in line with the requirements of the international standards ASTM D-6571 and EN 14214. In the course of our ongoing research, we made use of membrane technology, which led to the production of biodiesel from the seed oil of Saussurea heteromalla that was better for the environment, more cost effective, and produced in greater quantities.

Biodiesel Production Using Lithium Metasilicate Synthesized from Non-Conventional Sources

A facile and versatile process to produce lithium metasilicate (Li₂SiO₃) from non-conventional silicon sources (two different sand sources from the central area of México) was developed. The synthesis protocol based on a solid-state reaction followed by a hydrothermal treatment resulted in highly pure lithium metasilicate, as corroborated by XRD, SEM-EDS, and XPS analysis. Furthermore, lithium metasilicate was used as a heterogeneous catalyst for biodiesel production from soybean oil, where conversion yields were compared according to the silicon source used (based on chemical purity, stability, and yield efficiency). The best performing metasilicate material displayed a maximum of 95.5% of biodiesel conversion under the following conditions: 180 min, 60 °C, 5% catalyst (wt./wt., catalyst-to-oil), and 18:1 (methanol:oil). This contribution opens up alternatives for the production of lithium metasilicate using non-conventional precursors and its use as an alternative catalyst in biodiesel production, displaying better chemical stability against humidity than conventional heterogeneous catalysts.

Application of Tubular Reactor Technologies for the Acceleration of Biodiesel Production

The need to arrest the continued environmental contamination and degradation associated with the consumption of fossil-based fuels has continued to serve as an impetus for the increased utilization of renewable fuels. The demand for biodiesel has continued to escalate in the past few decades due to urbanization, industrialization, and stringent government policies in favor of renewable fuels for diverse applications. One of the strategies for ensuring the intensification, commercialization, and increased utilization of biodiesel is the adaptation of reactor technologies, especially tubular reactors. The current study reviewed the deployment of different types and configurations of tubular reactors for the acceleration of biodiesel production. The feedstocks, catalysts, conversion techniques, and modes of biodiesel conversion by reactor technologies are highlighted. The peculiarities, applications, merits, drawbacks, and instances of biodiesel synthesis through a packed bed, fluidized bed, trickle bed, oscillatory flow, and micro-channel tubular reactor technologies are discussed to facilitate a better comprehension of the mechanisms behind the technology. Indeed, the deployment of the transesterification technique in tubular reactor technologies will ensure the ecofriendly, low-cost, and large-scale production of biodiesel, a high product yield, and will generate high-quality biodiesel. The outcome of this study will enrich scholarship and stimulate a renewed interest in the application of tubular reactors for large-scale biodiesel production among biodiesel refiners and other stakeholders. Going forward, the use of innovative technologies such as robotics, machine learning, smart metering, artificial intelligent, and other modeling tools should be deployed to monitor reactor technologies for biodiesel production.

Bioprocesses for the Biodiesel Production from Waste Oils and Valorization of Glycerol

The environmental context causes the use of renewable energy to increase, with the aim of finding alternatives to fossil-based products such as fuels. Biodiesel, an alternative to diesel, is now a well-developed solution, and its production from renewable resources makes it perfectly suitable in the environmental context. In addition, it is biodegradable, non-toxic and has low greenhouse gas emissions: reduced about 85% compared to diesel. However, the feedstock used to produce biodiesel competes with agriculture and the application of chemical reactions is not advantageous with a “green” process. Therefore, this review focuses only on bioprocesses currently taking an important place in the production of biodiesel and allow high yields, above 90%, and with very few produced impurities. In addition, the use of waste oils as feedstock, which now accounts for 10% of feedstocks used in the production of biodiesel, avoids competition with agriculture. To present a complete life-cycle of oils in this review, a second part will focus on the valorization of the biodiesel by-product, glycerol. About 10% of glycerol is generated during the production of biodiesel, so it should be recovered to high value-added products, always based on bioprocesses. This review will also present existing techniques to extract and purify glycerol. In the end, from the collection of feedstocks to the production of CO2 during the combustion of biodiesel, this review presents the steps using the “greener” possible processes.

Ionic Liquid Co-Catalyst Assisted Biodiesel Production From Waste Cooking Oil Using Heterogeneous Nanocatalyst: Optimization and Characterization

In the present work, the biodiesel was produced from waste cooking oil (WCO) using heterogeneous zinc doped iron nanocatalyst and tetrabutylammonium iodide (TBAI) as co-catalyst. The heterogeneous zinc doped iron nanocatalyst was synthesized and characterized. The functional group in the heterogeneous nanocatalyst was confirmed using FTIR analysis, the crystalline nature was studied by XRD analysis, and the size and structure of the nanocatalyst were analyzed by SEM. The optimization of transesterification parameters like oil to methanol molar ratio, zinc doped iron concentration, TBAI concentration, temperature, and time were carried out for the maximum conversion of biodiesel from WCO. At 50 min the maximum biodiesel conversion of 90% was achieved at 55°C with 12% catalyst, 30% co-catalyst, and 1:11 WCO to methanol ratio. The presence of functional groups and the methyl ester composition of the biodiesel from WCO were confirmed by FTIR and GC-MS analysis. The use of zinc doped iron nanocatalyst with TBAI showed good catalytic activity to produce biodiesel from WCO.

Analyzing the Role of Renewable Energy and Energy Intensity in the Ecological Footprint of the United Arab Emirates

Even though a great number of researchers have explored the determinants of environmental pollution, the majority have used carbon emissions as an indicator while only recent studies have employed the ecological footprint which is a broader and more reliable indicator for the environment. The present study contributes to the literature by exploring for the first time in the literature the role of real output, energy intensity (technology), and renewable energy in the ecological footprint under the STIRPAT framework for a Gulf Cooperation Council (GCC) country—the United Arab Emirates. By applying the novel bounds testing with dynamic simulations on the data from 1992–2017, the findings of this paper reveal that energy intensity and renewable energy have a negative and significant influence on the ecological footprint but real output has a positive and significant impact on it. In other words, the empirical results indicate that a rise in the real income increases environmental pollution while increases in renewable energy and advances in technology mitigate the level of emissions. The findings also suggest that the government should establish new programs, investment opportunities, and incentives in favor of energy intensity-related technology and renewable energy for the sake of environmental sustainability. The outcomes from this research analysis are useful for policymakers, industrial partners, and project designers in the United Arab Emirates.

A Novel Approach of Bioesters Synthesis through Different Technologies by Highlighting the Lowest Energetic Consumption One

Fatty acids esters have a wide application as bioplasticizers and biolubricants in different industries, obtained mainly in classic batch reactors, through an equilibrium complex reaction, that involves high temperatures, long reaction times, vigorously stirring, and much energy consumption. To overcome these shortcomings, we synthesized a series of fatty acid esters (soybean oil fatty acids being the acid components with various hydroxyl compounds) through novel low energy consumption technologies using a bubble column reactor, a microwave field reactor and for comparison meaning, a classic batch reactor. The obtained bioesters physicochemical properties were similar to one another, a good concordance among their rheological properties was obtained, but the energetic consumption is lower when using the bubble column or the microwave reactors instead of the classical batch reactor.

Synergetic Co-Production of Beer Colouring Agent and Solid Fuel from Brewers’ Spent Grain in the Circular Economy Perspective

Brewers’ Spent Grain is a by-product of the brewing process, with potential applications for energy purposes. This paper presents the results of an investigation aiming at valorization of this residue by torrefaction, making product for two purposes: a solid fuel that could be used for generation of heat for the brewery and a colouring agent that could replace colouring malt for the production of dark beers. Decreased consumption of malt for such purposes would have a positive influence on the sustainability of brewing. Torrefaction was performed at temperatures ranging between 180 °C and 300 °C, with a residence time between 20 and 60 min. For the most severe torrefaction conditions (300 °C, 60 min), the higher heating value of torrefied BSG reached 25 MJ/kg. However, the best beer colouring properties were achieved for mild torrefaction conditions, i.e., 180 °C for 60 min and 210 °C for 40 min, reaching European Brewery Convention colours of 145 and 159, respectively. From the solid fuel properties perspective, the improvements offered by torrefaction in such mild conditions were modest. Overall, the obtained results suggest some trade-off between the optimum colouring properties and optimum solid fuel properties that need to be considered when such dual-purpose torrefaction of BSG for brewery purposes is implemented.

Key Barriers to the Adoption of Biomass Gasification in Burkina Faso

The industrial sector in Burkina Faso faces two significant energy challenges access to efficient energy sources that are also renewable. Pyrolysis and gasification are emerging as conversion pathways that exploit available agricultural and industrial biomass. Pyrolysis has been adopted successfully, whereas gasification failed without getting beyond the experimental stage. This article assesses potential barriers to the adoption of gasification based on interviews with the stakeholders of the energy sector (users, NGOs, policy makers). We use pyrolysis as a benchmark to point out the barriers to adoption. The hierarchical analysis process (AHP) method was applied to identify the most significant barriers to the adoption of gasification. Twenty-seven barriers were identified and prioritized in two dimensions and five categories “technical”, “economic and financial”, “socio-cultural and organizational”, “political, governmental and institutional”, and “ecological and geographical” barriers. The category of socio-cultural and organizational barriers emerged as the most critical in the adoption of gasification. This category deserves special consideration to go past the pilot installation stage and adopting this technology.

Activation of Nano Kaolin Clay for Bio-Glycerol Conversion to a Valuable Fuel Additive

High production of biodiesel results in a surplus of glycerol as a byproduct that leads to a drastic decline in the glycerol price as well as overall biodiesel production. Alternative methods must be introduced for the economical process for biodiesel production via utilization of crude glycerol into valuable chemicals or fuel additives. This study introduces an ecofriendly process of solketal synthesis from glycerol and acetone in the presence of a novel metakaolin clay catalyst, which is a useful additive in biodiesel or gasoline, in order to enhance the octane number and to control the emissions. Moreover, kaolin clay catalysts are low cost, abundantly available, eco-friendly and one of the more promising applications for solketal synthesis. In this study, raw kaolin clay was activated with an easy acid activation technique, modification in physicochemical and textural properties were determined by using X-ray diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) and Field Emission Scanning Electron Microscope. Among all acid-treated catalysts, metakaolin K3 have shown best catalytic properties, high surface area and pore size after acid activation with 3.0 mol/dm3 at 98 °C for 3 h. Acetalization of glycerol with acetone carried out in the presence of an environmentally friendly and inexpensive novel metakaolin K3 catalyst. The maximum yield of solketal obtained was 84% at a temperature of 50 °C, acetone/glycerol molar ratio 6/1 and for 90 min with novel metakaolin clay catalyst. Effect of various parameters (time, temperature, acetone/glycerol molar ratio, catalyst loading) on the solketal yield and glycerol conversion was discussed in detail. This approach offers an effective way to transform glycerol into solketal—a desirable green chemical with future industrial applications.