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Waste-Derived Catalysts for Sustainable Biodiesel Production: Current Status on Catalyst Development and Future Prospectives
Abstract
The extensive use of fossil resources in fuel production, leading to the emission of high levels of anthropogenic gases and atmospheric degradation, is a cause for concern. Consequently, exploring substitutes for fossil fuels and renewable raw materials in the production of sustainable fuels has become a critical area of research. Over the past decades, significant efforts have been dedicated to researching renewable and eco-friendly fuels from diverse sources. A prominent avenue of investigation involves biodiesel production from fats and oils through the uncomplicated process of transesterification, utilizing acid–base catalysts. The design of these catalysts is pivotal, not only for ensuring efficient conversion but also for achieving high biodiesel selectivity and enhancing the techno-economics of the process. Strategic selection of raw materials, such as non-edible fats and oils, is crucial to elevate the process's importance and mitigate potential conflicts between food and fuel resources. Furthermore, catalyst design and synthesis play a crucial role in refining the biodiesel production process. Particularly, catalysts derived from waste, featuring precise active sites, are recognized as important tools for achieving enhanced catalyst activity at reduced costs. Therefore, this review examines the trajectory of catalyst development for biodiesel production from various feedstocks, with a primary focus on the design of waste-derived catalytic nanostructured materials for sustainable development. It is anticipated that this review will provide insights into the next generation of sustainable biodiesel production methods.
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Biodiesel, a renewable and sustainable alternative to fossil fuels, has garnered significant attention as a potential solution to the growing energy crisis and environmental concerns. The review commences with a thorough examination of feedstock selection and preparation, emphasizing the critical role of feedstock quality in ensuring optimal biodiesel production efficiency and quality. Next, it delves into the advancements in biodiesel applications, highlighting its versatility and potential to reduce greenhouse gas emissions and dependence on fossil fuels. The heart of the review focuses on transesterification, the key process in biodiesel production. It provides an in-depth analysis of various catalysts, including homogeneous, heterogeneous, enzyme-based, and nanomaterial catalysts, exploring their distinct characteristics and behavior during transesterification. The review also sheds light on the transesterification reaction mechanism and kinetics, emphasizing the importance of kinetic modeling in process optimization. Recent developments in biodiesel production, including feedstock selection, process optimization, and sustainability, are discussed, along with the challenges related to engine performance, emissions, and compatibility that hinder wider biodiesel adoption. The review concludes by emphasizing the need for ongoing research, development, and collaboration among academia, industry, and policymakers to address the challenges and pursue further research in biodiesel production. It outlines specific recommendations for future research, paving the way for the widespread adoption of biodiesel as a renewable energy source and fostering a cleaner and more sustainable future.
Clean energy can lead to significant health benefits. Making it accessible throughout the world can address many ills. We delve deeply into one example—the transition toward clean residential heating and its relationship to health benefits—in China. We find that the health benefits can outweigh costs from energy expenses in northern provinces. Low-income households enjoy larger health benefits but also experience a higher expense increase, suggesting that extra subsidies or stimuli are needed to help them benefit from clean energy. Our findings suggest that clean energy transitions should be promoted in developing economies due to improved social health, lessened medical costs, and significant environmental improvements.
Sustainable agriculture strives to ensure future food and energy supply while safeguarding natural resources. The interpretation of sustainability varies by context and country, yielding distinct indicators. Researchers have studied sustainable agriculture for the past 25 years and have developed several indicators. Renewable energy holds a vital role in sustainable agriculture, aiding energy needs and mitigating environmental harm tied to agriculture. It curbs fossil fuel dependency and harnesses agricultural waste for energy. However, a consistent update of renewable energy indicators for agricultural sustainability is needed. Employing SALSA (Search, Appraisal, Synthesis, and Analysis) and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodologies within the PRISMA protocol, this study extracts 84 indicators from 420 papers via SCOPUS. These indicators span social, environmental, economic, institutional, and technical dimensions. The study refines these indicators based on significance and influence, offering an enriched perspective. Furthermore, the analysis categorizes papers by publication year, continent, and topic, providing insights for stakeholders, policymakers, and researchers. By ensuring periodic indicator updates, this research promotes sustainable agriculture, informs priority areas, and guides strategic decisions. This contributes to global resilience and food security aspirations in a changing world. The future of renewable energy and sustainable agriculture will involve cutting-edge technologies, refined policy frameworks, and inclusive cross-sector collaboration to address pressing global challenges and create a greener, more resilient world.
Biodiesel produced from different edible and non‐edible feedstocks is a viable alternative option for fueling a combustion engine. However, the widespread use of edible sources for biodiesel production may lead to food versus fuel controversy. Oil from non‐edible feedstock is best possible solution for problems that inhibits biodiesel production on commercial scale. This study presents the potential of different non‐edible feedstock for biodiesel production. Several aspects such as extraction technologies used for extracting oil from non‐edible sources and biodiesel production pathways from non‐edible feedstocks are discussed. The quality of biodiesel should be assured before its commercialization by different physical and chemical characterization techniques are used. In particular, the emission comparison of biodiesel derived from the different non‐edible feedstocks is discussed. Based on this study, the non‐edible feedstocks have the potential to produce biodiesel but still it has a long way to go. This is due to non‐edible feedstock is in the R&D phase and needs more research to eliminate additional treatment steps compared to edible feedstock for economic aspects. Furthermore, there has been a trade off in emission properties of biodiesels produced from non‐edible feedstocks which must be removed or evaluated for pilot scale investigations before commercialization.
The strontium‐manganese supported over ceramic was synthesized through wet impregnation method and investigated as a solid catalyst for its catalytic performance in transesterifying‐esterifying low‐grade waste frying oil with methanol in a batch reactor; parameters for synthesis of catalyst and transesterification reaction were also optimized. The maximum biodiesel yield of 93.66 % was attained by SrO‐MnO/Ceramic catalyst under normal process conditions. The synthesized catalyst reusability potential was also evaluated for 12 runs with regeneration carried out after the 7th run only and it revealed that the catalyst showed great stability for the initial five cycles offering yield of over 90 %. The fresh and used SrO‐MnO/Ceramic catalysts were characterized to address the mechanism of catalytic behavior and deactivation using scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), X‐ray diffraction (XRD), benzoic acid and n‐butylamine titration method, and Hammett indicators. The alteration in surface morphology; Mn solubility in glycerol and methanol; occupation of energetic centers by organics might be the reasons for diminished activity or deactivation of solid catalyst after repeated reuse.
Biodiesel, an important sustainable fuel used in the transportation sector, demands a stable, recyclable and green catalyst for its economical and environmentally benign production. A novel green heterogeneous acid catalyst was developed by extracting sodium silicate from bamboo leaf ash (BLA), using which SBA-16 (BLA) was synthesized and then impregnated with 10 wt% each of WO 3 and ZrO 2 , characterized and evaluated for the transesterification of Ankol seed oil with methanol to biodiesel. XRD, SEM, TEM and pore size characterization indicated that impregnated WO 3 and ZrO 2 were present outside the mesopores of SBA-16 (BLA) as monoclinic phases, thus 3D cubic cage-like Im3m mesopores of SBA-16 were unaltered. NH 3 -TPD indicated the presence of acid sites of two distinct strengths, attributed to the Lewis and Brønsted acidity of WO 3 –ZrO 2 impregnated into SBA-16 (BLA) and hence gave the highest biodiesel yield of 98 %. In contrast 10 wt% of WO 3 and 10 wt% of ZrO 2 separately impregnated into SBA-16 gave 65 and 57 % of biodiesel yield respectively, possibly due to the presence of Lewis acidity alone in them. Among the WO 3 (10 %)–ZrO 2 (10 %) impregnated mesoporous supports viz. SBA-16 (BLA), SBA-16 (synthesized using tetraethyl orthosilicate), SBA-15, MCM-41, MCM-48, KIT-6, FDU-5, and TUD-1, the highest biodiesel yield of 98 % was given by SBA-16 (BLA), attributed to its spherical morphology and strong interaction with WO 3 –ZrO 2 as inferred from SEM and XPS characterizations respectively. From the effect of process parameters on the WO 3 (10 %)–ZrO 2 (10 %)/SBA-16 (BLA) catalyst, maximum biodiesel yield was obtained at the temperature of 65 °C, catalyst amount of 200 mg, methanol:oil weight ratio of 10:1 and reaction time of 3 h. Under these reaction conditions, it retained the same biodiesel yield for six recycles after regeneration every time, confirmed its catalytic stability and recyclability.
The marine fish oil obtained during fishmeal production and shrimp shells through whole shrimp processing have less commercial importance, mostly considered as waste and are disposed to environment resulting in pollution. The current research focuses on exploiting fish industry wastes such as Fenneropenaeus indicus shrimp shell and marine fishmeal industry (MFMI) oil with a perspective of achieving sustainable biodiesel production and overcome disposal pollution issues. The physicochemical properties of MFMI oil indicated its suitability to be used as feedstock for biodiesel production. The catalyst characterization by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Scanning electron microscopy (SEM), and Brunauer–Emmett–Teller analysis revealed that calcination of shrimp shells resulted in the formation of crystalline mesoporous solid catalyst primarily composed of CaO. As per the central composite design of response surface methodology, the maximum biodiesel yield of 86.56wt% was obtained from MFMI oil at an oil to methanol molar ratio of 1:12 (mol/mol), catalyst concentration of 5 wt% of oil, reaction temperature of 65 °C, and reaction time of 120 min. Further, based on flask level optimized condition, the biodiesel production was scaled to a 50 L oil volume batch and achieved a good yield of 88.74 wt%. Further, the physicochemical properties and cold flow property of MFMI oil biodiesel ensured its application as fuel. Thus, MFMI oil and calcined shrimp shell catalyst could be utilized as promising feedstock and catalyst for sustainable biodiesel production.
Graphical Abstract
Biodiesel is a potential alternative fuel that offers several environmental benefits and can be used in conventional engines. However, high feedstock cost poses a challenge for its commercial viability. This study focuses on producing biodiesel using waste cooking oil (WCO) and Moringa oleifera oil (MOO) as feedstock, with a specific emphasis on the use of modified conch shell as solid catalyst under ultrasonic conditions. Different mixtures of WCO and MOO were evaluated for their suitability in a two‐stage esterification transesterification process, and the acid value of the WCO‐MOO blend was reduced through an ultrasound‐assisted esterification process. Additionally, a calcium oxide‐based catalyst was developed from conch shells (CS) through calcination for 3 h at 900°C and further modified using water and methanol. The characterization studies confirm the successful development and modification of the CS catalyst and also demonstrates excellent catalytic activity. The ultrasound assisted transesterification process parameters were optimized using response surface methodology (RSM) based Box–Behnken design (BBD). By employing a catalyst loading of 5.8 wt%, methanol to esterified oil volumetric ratio of 0.37:1, and an ultrasonication time of 57 min, a maximum predicted methyl ester conversion of 94.7% was achieved. Therefore, this work provides valuable insights into the use of modified conch shell catalyst for biodiesel production from WCO and MOO mixtures thereby contributing to the advancement of cost‐effective and environmentally friendly biodiesel production methods.
For further resource utilization of solid waste steel slag and the reduction in biodiesel production costs, this study used steel slag as a carrier to synthesize a CaO-CeO2/slag solid base catalyst for the effective transesterification of palm oil into fatty acid methyl esters (FAMEs). The synthesis involved a two-step impregnation of steel slag with nitrate of calcium and cerium and thermal activation at 800 °C for 180 min. Then, the catalysts’ textural, chemical, and CO2 temperature-programmed desorption properties were characterized. The catalytic activity depended highly on the ratio of Ca-Ce to steel slag mass; the CaO-CeO2/slag-0.8 catalyst showed outstanding performance. Characterization showed that the surface area and total basicity of the Ca-Ce/slag-0.8 catalyst were 3.66 m²/g and 1.289 mmol/g, respectively. The reactivity results showed that FAMEs obtained using 7 wt.% catalyst, 9:1 of methanol-to-palm-oil molar ratio, 180 min reaction duration, and 70 °C reaction temperature was optimum (i.e., 95.3% yield). In addition, the CaO-CeO2/slag-0.8 catalyst could be reused for at least three cycles, retaining 91.2% of FAMEs yield after n-hexane washing. Hence, the catalyst exhibits an excellent potential for cost-effective and environmentally friendly biodiesel production.
A novel carbon‐based solid catalyst was synthesized from waste biomass of watermelon peel (Citrullus lanatus) by one pot carbonization and functionalization with H2SO4 for biodiesel production. Oleic acid was utilized as a test substrate in this study given that it is a key component for majority of feedstocks used for biodiesel production. Synthesized catalyst was extensively characterized by X‐ray diffraction, Fourier transform infrared, thermogravimetric analysis, X‐ray photoelectron spectroscopy, scanning electron microscopy–EDX and Brunauer–Emmett Teller analysis. The catalyst revealed aromatic structure, hydrophilic OH and COOH groups as well as a high density of SO3H active centres with a total acidity of 3.6 mmol g⁻¹. Using the optimized reaction condition (MeOH: oleic acid molar ratio 20:1, catalyst loading 8 wt.%, temperature 100°C and reaction time of 60 min) under microwave irradiation (50 W, 100 psi) a conversion as high as 94.36 ± 0.3% of oleic acid to biodiesel was reported. Activation energy of the esterification was found to be 38.16 kJ mol⁻¹. Catalyst recovery was probed to over five reaction cycles, with a modest loss in activity (81.73 ± 0.4% conversion in the fifth cycle) resulting from limited active site leaching.
The global shift from a fossil fuel-based to an electrical-based society is commonly viewed as an ecological improvement. However, the electrical power industry is a major source of carbon dioxide emissions, and incorporating renewable energy can still negatively impact the environment. Despite rising research in renewable energy, the impact of renewable energy consumption on the environment is poorly known. Here, we review the integration of renewable energies into the electricity sector from social, environmental, and economic perspectives. We found that implementing solar photovoltaic, battery storage, wind, hydropower, and bioenergy can provide 504,000 jobs in 2030 and 4.18 million jobs in 2050. For desalinization, photovoltaic/wind/battery storage systems supported by a diesel generator can reduce the cost of water production by 69% and adverse environmental effects by 90%, compared to full fossil fuel systems. The potential of carbon emission reduction increases with the percentage of renewable energy sources utilized. The photovoltaic/wind/hydroelectric system is the most effective in addressing climate change, producing a 2.11–5.46% increase in power generation and a 3.74–71.61% guarantee in share ratios. Compared to single energy systems, hybrid energy systems are more reliable and better equipped to withstand the impacts of climate change on the power supply.
The Russia–Ukraine conflict has triggered an energy crisis that directly affected household energy costs for heating, cooling and mobility and indirectly pushed up the costs of other goods and services throughout global supply chains. Here we bridge a global multi-regional input–output database with detailed household-expenditure data to model the direct and indirect impacts of increased energy prices on 201 expenditure groups in 116 countries. On the basis of a set of energy price scenarios, we show that total energy costs of households would increase by 62.6–112.9%, contributing to a 2.7–4.8% increase in household expenditures. The energy cost burdens across household groups vary due to differences in supply chain structure, consumption patterns and energy needs. Under the cost-of-living pressures, an additional 78 million–141 million people will potentially be pushed into extreme poverty. Targeted energy assistance can help vulnerable households during this crisis. We emphasize support for increased costs of necessities, especially for food.
The global amount of solid waste has dramatically increased as a result of rapid population growth, accelerated urbanization, agricultural demand, and industrial development. The world's population is expected to reach 8.5 billion by 2030, while solid waste production will reach 2.59 billion tons. This will deteriorate the already strained environment and climate situation. Consequently, there is an urgent need for methods to recycle solid waste. Here, we review recent technologies to treat solid waste, and we assess the economic feasibility of transforming waste into energy. We focus on municipal, agricultural, and industrial waste. We found that methane captured from landfilled-municipal solid waste in Delhi could supply 8–18 million houses with electricity and generate 7140 gigawatt-hour, with a prospected potential of 31,346 and 77,748 gigawatt-hour by 2030 and 2060, respectively. Valorization of agricultural solid waste and food waste by anaerobic digestion systems could replace 61.46% of natural gas and 38.54% of coal use in the United Kingdom, and could reduce land use of 1.8 million hectares if provided as animal feeds. We also estimated a levelized cost of landfill solid and anaerobic digestion waste-to-energy technologies of 0.07/kilowatt-hour, with a payback time of 0.73–1.86 years and 1.17–2.37 years, respectively. Nonetheless, current landfill waste treatment methods are still inefficient, in particular for treating food waste containing over 60% water.
Every year, close to 8 million tons of waste crab, shrimp and lobster shells are produced globally, as well as 10 million tons of waste oyster, clam, scallop and mussel shells. The disposed shells are frequently dumped at sea or sent to landfill, where they modify soils, waters and marine ecosystems. Waste shells are a major by-product, which should become a new raw material to be used to the best of their potential. There are a number of applications for waste shells in many fields, such as agriculture, medicine, chemical production, construction, environmental protection, cosmetic industry, food and feed industry, and a plethora of other (often niche) applications, which are being developed by the day. This review provides a broad picture of crustacean and mollusc shell waste management and reutilization possibilities, reviewing well established, current, and potential strategies, particularly from the standpoint of sustainability challenges and energy demand.
Sewage sludge (SS) is a residual/semi-solid material produced from industrial and municipal wastewater treatment processes. SS contains a high content of lipids and earth alkaline metals that can be used as catalysts for various chemical applications; however, its valorization has rarely been the focus of research. This study demonstrates that SS could be a promising raw material for biodiesel production and a biochar catalyst to promote the reaction kinetics of alkylation. Thermally induced transesterification of the SS extract (SSE) was performed in comparison with the conventional homogeneous reaction. SS biochar was fabricated via pyrolysis. The highest yield (33.5 wt.% per SSE) of biodiesel production was achieved in 1 min of reaction at 305 °C via thermally induced transesterification in the presence of SS biochar, while the yield of biodiesel from (trans)esterification with 5 wt.% H 2 SO 4 was less than 1% even after 24 h. The reaction kinetics (< 1 min) of thermally induced transesterification was extraordinarily faster than that of conventional transesterification (3–24 h). The porous structure and high content of alkaline species in the SS biochar expedited the reaction kinetics. Consequently, the integrated/hybridized process for thermally induced transesterification and pyrolysis of the solid residue of SS was experimentally proved for the valorization of SS in this study. Considering that SS is being disposed of as a waste material and generates toxic chemicals in the environment, its valorization into value-added biodiesel and a catalyst could be an environmentally benign and sustainable technique.
Graphical Abstract
In this study, we have synthesized a solid acid catalyst by areca nut husk using low temperature hydrothermal carbonization method. The fabricated catalyst has enhanced sulfonic actives sites (3.12%) and high acid density (1.88 mmol g−1) due to –SO3H, which are used significantly for effective biodiesel synthesis at low temperatures. The chemical composition and morphology of the catalyst is determined by various techniques, such as Fourier transform infrared (FTIR), powder X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Scanning electron microscope (SEM), Energy disruptive spectroscopy (EDS), Mapping, Thermogravimetric analysis (TGA), CHNS analyzer, Transmission electron microscopy (TEM), particle size analyzer, and X-ray photoelectron spectroscopy (XPS). Acid–base back titration method was used to determine the acid density of the synthesized material. In the presence of the as-fabricated catalyst, the conversion of oleic acid (OA) to methyl oleate reached 96.4% in 60 min under optimized conditions (1:25 Oleic acid: methanol ratio, 80 °C, 60 min, 9 wt% catalyst dosage) and observed low activation energy of 45.377 kJ mol−1. The presence of the porous structure and sulfonic groups of the catalyst contributes to the high activity of the catalyst. The biodiesel synthesis was confirmed by gas-chromatography mass spectrometer (GC–MS) and Nuclear magnetic resonance (NMR). The reusability of the catalyst was examined up to four consecutive cycles, yielding a high 85% transformation of OA to methyl oleate on the fourth catalytic cycle.
Since fossil fuel emissions will continue indefinitely, we must find a suitable and long-term alternative, owing to the fact that it is biodegradable, non-toxic, and eco-friendly, biodiesel an excellent substitute for diesel engines. EASAC classifies the evolution of biodiesel into four generations. Biodiesel feedstocks and their advantages and disadvantages for different generations of the fuel are thoroughly analysed in this article. An in-depth investigation is provided in this article, of the benefits and drawbacks of various feedstocks used in the manufacturing process of different generations of biodiesel.
In terms of the production of biodiesel, transesterification is the best method because it produces high-yield biodiesel with comparable properties to diesel, making it an ideal choice. As far as economics are concerned, this process is also viable. It is possible to meet the energy requirements of the future by blending different oil feedstocks. The system used and the cost of feedstock have the most significant impact on the cost of biodiesel production. Characteristics of biodiesel such as the oxidation stability, cold flow and cetane number, viscosity, and density, are some of the most important characteristics of biodiesel. Biodiesel’s performance in diesel engines was also discussed in this paper, and it was suggested that biodiesel is safer for the environment than Petro-diesel. Unlike Petro-diesel, it degrades four times faster and has with a higher flash point, making storage and handling easier. It’s also nontoxic and causes less irritation to the skin than soap and water. The paper also looked at the production of biodiesel using feedstocks from the first through the fourth generation.
Solid waste management (SWM) is one of the key responsibilities of city administrators and one of the effective proxies for good governance. Effective SWM mitigates adverse health and environmental impacts, conserves resources, and improves the livability of cities. However, unsus-tainable SWM practices, exacerbated by rapid urbanization and financial and institutional limitations , negatively impact public health and environmental sustainability. This review article assesses the human and environmental health impacts of SWM practices in the Global South cities that are the future of global urbanization. The study employs desktop research methodology based on in-depth analysis of secondary data and literature, including official documents and published articles. It finds that the commonplace SWM practices include mixing household and commercial garbage with hazardous waste during storage and handling. While waste storage is largely in old or poorly managed facilities such as storage containers, the transportation system is often deficient and informal. The disposal methods are predominantly via uncontrolled dumping, open-air incinerators, and landfills. The negative impacts of such practices include air and water pollution, land degradation, emissions of methane and hazardous leachate, and climate change. These impacts impose significant environmental and public health costs on residents with marginalized social groups mostly affected. The paper concludes with recommendations for mitigating the public and environmental health risks associated with the existing SWM practices in the Global South.
Herein, a zinc oxide based coal fly ash (ZnO-CFA) composite as heterogeneous catalyst was formulated and explored for transesterification of non-edible oil (Jatropha curcas oil, JCO). The as-synthesized catalyst was analyzed to gain insights into its properties using various characterization techniques (EDX, FTIR, TEM, XRD and BET surface area). The solid catalyst’s ability to catalyze the methanolysis reaction was investigated and optimized at varying reaction temperature, methanol/JCO molar ratio and catalyst dosage using Box-Behnken design. Predicted value of biodiesel yield was found to be in excellent agreement with observed value with high coefficient of determination R2=0.9759andAdj.R2=0.9449. It was determined that optimum transesterification process conditions of 60.4 oC reaction temperature, 11.8:1 methanol/JCO molar ratio and 1.63 wt.% catalyst loading resulted in biodiesel yield and FAME content of 91.08 ± 0.06% and 97.22%, respectively. Additionally, the produced biodiesel at the optimum conditions was shown to be conformed to ASTM standard. The ZnO-CFA catalyst was simple to synthesize and handle, eliminating the need for costly aluminosilicate-based catalysts in biofuel synthesis. It was also simple to separate from the product stream and could be recycled up to four times.
Biochar and ashes derived from coffee husk were used as heterogeneous catalysts in the synthesis of biodiesel through a transesterification reaction. The catalysts were obtained from the carbonization, activation, and combustion of raw coffee husks. Their properties were characterized by solid-state 13C and 31P nuclear magnetic resonance (NMR) spectroscopies and X-ray diffraction, among other techniques. The results evidenced the presence of different inorganic compounds (mostly K- and Ca-containing phases) mixed with the turbostratic structure (in the case of the biochar samples). A biodiesel conversion of 66% (evaluated by 1H NMR analysis of the liquid reaction products) was found for the biochar sample prepared at 700 °C; the activated biochar catalyst prepared at the same temperature showed a higher biodiesel conversion (74%), which can be attributed to its superior specific surface area. The best catalytic efficiency (biodiesel conversion of 93%) was observed for the coffee husk ashes, which is consistent with the higher contents of Ca and K salts in the ashes in comparison with the biochar samples. Reuse tests conducted with the ashes samples showed an efficiency reduction after the second cycle (from around 90% in the first two cycles to 8% in the third cycle), due to the partial removal of active phases (mostly K-containing salts) within the reaction medium. The presented results show that coffee husks are a cheap and environmentally viable source for the production of materials of interest in heterogeneous catalysis, with no need for chemical modification to achieve good efficiency.
To produce biodiesel from oleic acid (OA), the effectiveness of sweet lemon (Citrus limetta) waste peels as an acidic catalyst in an esterification process is examined in the current work. A biowaste-derived sulfonated carbon-based catalyst is fabricated without high temperatures via a simple one-pot process. Several techniques are used to investigate the chemical components and morphology of the catalyst, including Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), and N2 adsorption-desorption. The biodiesel conversion is observed by gas chromatography-mass spectrometry (GC-MS), proton nuclear magnetic resonance 1H NMR, and carbon nuclear magnetic resonance 13C NMR. The excellent biodiesel conversion of 96% was obtained using optimized conditions, i.e., 1:20 of OA/MeOH, 5 wt % catalyst loading, 70 °C temperature, and 3 h. The catalyst shows 87% conversion in just 1 h, and the maximum conversion was found to be ≈96%. This high activity of the catalyst can be attributed to the presence of sulfonic groups and its porous nature. The formed catalyst shows excellent catalytic activity up to three cycles.
Efficient valorization of renewable liquid biomass for biodiesel production using the desirable biomass-based catalysts is being deemed to be an environmentally friendly process. Herein, a highly active biomass-based solid acid catalyst (SiO2@Cs-SO3H) with renewable chitosan as raw material through sulfonation procedure under the relatively mild condition was successfully manufactured. The SiO2@Cs-SO3H catalyst was systematically characterized, especially with a large specific surface area (21.82 m²/g) and acidity (3.47 mmol/g). The catalytic activity of SiO2@Cs-SO3H was evaluated by esterification of oleic acid (OA) and methanol for biodiesel production. The best biodiesel yield was acquired by Response Surface Methodology (RSM). The optimized reaction conditions were temperature of 92°C, time of 4.1 h, catalyst dosage of 6.8 wt%, and methanol to OA molar ratio of 31.4, respectively. In this case, the optimal experimental biodiesel yield was found to be 98.2%, which was close to that of the predicted value of 98.4%, indicating the good reliability of RSM employed in this study. Furthermore, SiO2@Cs-SO3H also exhibited good reusability in terms of five consecutive recycles with 87.0% biodiesel yield. As such, SiO2@Cs-SO3H can be considered and used as a bio-based sustainable catalyst of high-efficiency for biodiesel production.
Biodiesel is considered eco-friendly, biodegradable, non-toxic, and carbon-neutral fuel. It is made from edible or non-edible oil feedstocks including other triglyceride sources. The production of biodiesel depends on the availability of a particular feedstock and the cost of desired raw materials. Biodiesel is mainly produced by the transesterification process using a suitable catalyst preferably a heterogeneous catalyst as it is more beneficial in terms of reusability, recovery, product purity, and production cost as well. Various reactors are developed to produce cost-effective biodiesel at the commercial level. The latest trend in biodiesel synthesis is the application of the machine learning (ML) technique to optimize the process parameters. The application of a mixture of two or more oils as feedstock either non-edible or edible oil is emphasized for biodiesel synthesis and is presently getting more importance. In this paper, the production of biodiesel from various mixed oil (hybrid oil) is reviewed and the effects of mixed oil on the reaction, physicochemical properties, fatty acid composition, and fuel quality of the product are discussed. The study highlighted the activity of various catalysts in the reaction of mixed oil and the economic feasibility. It was found that the ratio of mixed oil is an important factor in terms of conversion and quality of biodiesel. It is also revealed that the application of the ML technique is essentially useful to optimize production efficiency. The utilization of mixed oils will overcome the issues related to the non-availability of feedstocks and reduce the overall cost with improved quality of biodiesel. This approach enhances the production possibility of biodiesel at a large-scale and may boost the biorefinery sector satisfying the future energy demand if the research at the advanced level goes in the right direction.
Garlic peel (GP), as a readily available agricultural waste, has been successfully employed to synthesize a carbon-based solid acid catalyst, which, in turn, has been used to catalyze the esterification of oleic acid with methanol for biodiesel production. Several GP-based catalysts have been synthesized by partial carbonization at various temperatures (300, 350, 400, 450, and 500 °C) followed by sulfonation at 105 °C for 120 min, and characterized by means of various techniques. The catalyst carbonized at 350 °C showed the highest density of sulfonic acid moieties of 1.24 mmol/g, corresponding to the maximum oleic acid conversion of 96.3%. This was achieved with optimum operating parameters of catalyst dosage 8 wt% (with respect to the mass of oleic acid), a molar ratio of methanol to oleic acid of 10, and reaction for 210 min at 60 °C. Importantly, the GP-based catalyst showed satisfactory recyclability, retaining 73.2% of its initial catalytic activity after a fifth cycle.
Graphical Abstract
Sustainable renewable energy production is being intensely disputed worldwide because fossil fuel resources are declining gradually. One solution is biodiesel production via the transesterification process, which is environmentally feasible due to its low-emission diesel substitute. Significant issues arising with biodiesel production are the cost of the processes, which has stuck its sustainability and the applicability of different resources. In this article, the common biodiesel feedstock such as edible and non-edible vegetable oils, waste oil and animal fats and their advantages and disadvantages were reviewed according to the Web of Science (WOS) database over the timeframe of 1970-2020. The biodiesel feedstock has water or free fatty acid, but it will produce soap by reacting free fatty acids with an alkali catalyst when they present in high portion. This reaction is unfavourable and decreases the biodiesel product yield. This issue can be solved by designing multiple transesterification stages or by employing acidic catalysts to prevent saponification. The second solution is cheaper than the first one and even more applicable because of the abundant source of catalytic materials from a waste product such as rice husk ash, chicken eggshells, fly ash, red mud, steel slag, and coconut shell and lime mud. The overview of the advantages and disadvantages of different homogeneous and heterogeneous catalysts is summarized, and the catalyst promoters and prospects of biodiesel production are also suggested. This research provides beneficial ideas for catalyst synthesis from waste for the transesterification process economically, environmentally and industrially.
In this study a novel, high surface area, and recyclable nano-size solid basic catalyst is developed for the first time from ZIF-8 MOF-derived CaO/ZnO for the high-yielding transesterification of soybean oil (SO) to biodiesel with methanol under microwave irradiation. The chemical composition, texture and morphology of the catalyst were comprehensively characterized by FT-IR, SEM-EDS, XRD, TGA, XPS and BET. In addition, 1H NMR analyses were performed to confirm the conversion of soybean oil to biodiesel, whereas, GC-MS spectrum provide information about the chemical composition of the produced biodiesel. Kinetic studies are performed for the optimized catalyst and it follows the pseudo-first-order reaction. Thermodynamic analyses show that the transesterification of soybean oil to biodiesel reaction is endothermic and not spontaneous. By using Response surface methodology (RSM), the optimization of parameters that affect the biodiesel yield is studied. The transformation of 1:20 soybean oil with methanol using CaO/ZnO catalyst (7 wt. %) gives 97.4 % biodiesel yield for the transesterification at 90 ºC for 50 min. The catalyst shows good reusability after 5 successive cycles demonstrating its industrial-scale applications. According to Life cycle cost analysis (LCCA) the estimated price of 1 kg of biodiesel produced in this work is merely $1.11 showing high commercial applicability.
Importance of the work: A solid carbon catalyst was derived from mangosteen peel ash (MA) activated by potassium hydroxide and used as a support for potassium carbonate (K2CO3). It was prepared as a heterogeneous catalyst for the transesterification of palm oil to fatty acid methyl esters. Objectives: A central composite response surface methodology was used to optimize the biodiesel yield. The effects were investigated of different K2CO3impregnation levels on MA (0 by weight percentage (wt.%), 25 wt.%, 30 wt.% and 35 wt.%) and then on the catalyst loading (2.32-5.68 wt.%), the methanol-to-oil molar ratio (3.95:1-14.05:1), and the reaction time (39.55- 140.45 min) of the transesterification reaction at 65 °C. Materials & Methods: The mangosteen peel was procured from Songkhla province, Thailand and the palm oil was purchased from a local supermarket in Songkhla province. The catalysts were prepared using the incipient wetness impregnation method and applied for transesterification of palm oil with methanol to produce biodiesel. The reaction process was optimized in terms of the biodiesel yield using response surface methodology based on a central composite design. Results: The results demonstrated that the catalyst consisting of 30 wt.% K2CO3loaded MA (30K-MA) had the highest catalytic activity. Using the 30K-MA catalyst at 65 °C, the maximum biodiesel yield of 97.9% was prodcued at a catalyst loading of 4.5 wt.%, a methanol-to-oil molar ratio of 10.8:1 and a reaction time of 98.7 min. Main finding: The 30K-MA catalyst maintained sufficient catalytic activity (above 65% biodiesel yield) until the fourth reaction cycle, demonstrating the possibility of developing heterogeneous alkali catalysts from MA for biodiesel production.
In the fast-developing time, the accumulation of waste materials is always in an uptrend due to population increases and industrialization. This excessive accumulation in waste materials harms the ecosystem and human beings by depleting water quality, air quality, and biodiversity. Further, by use of fossil fuel problem-related global warming, greenhouse gases are the major challenge in front of the world. Nowadays, scientists and researchers are more focused on recycling and utilizing different waste materials like a municipal solid waste (MSW), agro-industrial waste etc. The waste materials added to the environment are converted into valuable products or green chemicals using green chemistry principles. These fields are the production of energy, synthesis of biofertilizers and use in the textile industry to fulfil the need of the present world. Here we need more focus on the circular economy considering the value of products in the bioeconomic market. For this purpose, sustainable development of the circular bio-economy is the most promising alternative, which is possible by incorporating the latest techniques like microwave-based extraction, enzyme immobilization-based removal, bioreactor-based removal etc., for the valorization of food waste materials. Further, the conversion of organic waste into valuable products like biofertilizers and vermicomposting is also realised by using earthworms. The present review article focuses on the various types of waste materials (such as MSW, agricultural, industrial, household waste, etc.), waste management with current glitches and the expected solutions that have been discussed. Furthermore, we have highlighted their safe conversion into green chemicals and contribution to the bioeconomic market. The role of the circular economy is also discussed.
A solid heterogeneous catalyst was derived from oil shale ash by impregnation of the ash with KNO3 followed by calcination for 4 h. Different preparation conditions were studied (KNO3 concentrations: 0.05 and 0.1 M, and calcination temperatures: 500 and 700 °C). After calcination, the dependence of waste cooking oil to biodiesel conversion on the reaction variables such as the catalyst loading, the methanol to oil molar ratio, and reaction time was investigated. The catalyst characterization was conducted using FT-IR, XRD, BET, TEM, and SEM. Further, the typical unsaturated fatty acids present in common vegetable oils, the oil-to-biodiesel conversion, and the chemical composition of the produced biodiesel were quantified by (¹H NMR). Among the various catalysts prepared, the ash impregnated with 0.1 M KNO3/and calcined at 700 °C (Ash 0.1/700 catalyst) provided the maximum oil to biodiesel conversion of about 100% at 65 °C reaction temperature, methanol to oil molar ratio of 45:1, and 2 h reaction time.
In the present study, the ash from discarded Karanja seed shell (KSS), obtained after burning dried seed shells has been identified as one of the most cost-effective and efficient green heterogeneous catalysts for biodiesel production. Soybean oil methanolsis was used to study the catalytic activity of karanja seed shell ash as solid base heterogeneous catalysts in the biodiesel production. To characterize the catalyst, XRD, WD-XRF, SEM, FT-IR, BET and TGA techniques were utilized. Soybean oil methyl ester was converted under the following experimental conditions, as determined by GC-MS, and FT-IR: a catalyst amount of 2 wt%, a methanol to oil molar ratio of 10:1, a reaction temperature of 65 °C, a reaction time of 60 min. The synthesized heterogeneous catalyst is an efficient alternative that may be utilized as an eco-friendly catalyst because it is benign, reusable, sustainable, and widely available.
Resistance of biodiesel industrial production came from high energy consumption and feedstock costs. To solve it, Na2CO3@BFD catalyst was prepared from blast furnace dust and used to catalyze biodiesel production at low temperature. Biodiesel yield of 99.04 wt% was obtained under conditions optimized by response surface methodology of methanol/oil molar ratio 13.72/1, catalyst dosage 9.77 wt % and 74.86 °C for 1.62 h. The order of influence of the four factors was temperature (245.9) > time (109.8) > methanol/oil molar ratio (23.83) > catalyst dosage (1.19). Back propagation neural network model (BPNN) was optimized using genetic algorithm (GA) and sparrow search algorithm (SSA) to predict biodiesel yield. The evaluation indexes of mean absolute error, mean square error, root mean square error and mean absolute percentage error of SSA-BPNN were 0.9236, 2.0184, 1.4207 and 1.0247 (vs. 2.4329, 9.1037, 3.0172 and 3.5000 for GA-BPNN and 4.3291, 43.4693, 6.5931 and 6.9227 for BPNN), indicating that SSA-BPNN model had excellent prediction ability to effectively reduce experimental costs and resource consumption. The reaction kinetics of Na2CO3@BFD for transesterification process showed that its activation energy was 65.73 kJ/mol, lower than that of reported solid base catalyst, indicating that it had significant potential in biomass conversion.
Waste biomass-supported magnetic solid acids have particular advantages in catalyst separation. First, a novel magnetic carbonaceous catalyst was synthesized from waste garlic peel (GP) via in situ impregnation before conducting carbonization at 450–600°C and sulfonation at 105°C. The physical and chemical properties of the synthesized catalysts were characterized. It was found that the magnetism of the catalyst increased with the carbonization temperature. The optimized catalyst, carbonized at 600°C (C600-S), possessed an excellent magnetization value of 12.5 emu/g, with a specific surface area of 175.1 m2/g, a pore volume of 0.16 cm3/g, and an acidic property of 0.74 mmol/g -SO3H density. By optimizing the esterification conditions to produce biodiesel, an oleic acid conversion of 94.5% was achieved at w(catalyst dosage) = 10% (w is mass fraction), a molar ratio of n(methanol): n(oleic acid) = 10: 1 (n is the amount of substance), and a reaction for 4 h at 90°C. Further, for catalyst regeneration, it was found that sulfuric acid treatment was more effective for improving the esterification activity than solvent washing, with which a conversion of more than 76% was achieved after the third run.
In this study, efficient solid catalysts from the post-harvest Musa chinensis peel, trunk and rhizome were prepared and applied effectively for the production of biodiesel from the quinary oil mixture (soybean oil, sunflower oil, canola oil, jatropha oil and pongamia oil). Catalyst characterization exhibited a highly basic character with the micro-mesoporous and polycrystalline nature of the material. This work investigated the effect of catalyst load, different catalysts from different parts of the plant, MRMO (molar ratio of methanol to oil) and temperature on the reaction. The calcined M. chinensis peel catalyst was found to be the best with 44.15 wt% of K occurring as its carbonate and oxide, which successfully yielded 95.82 % biodiesel at optimized conditions of 5 wt% catalyst amount and 9:1 MRMO at temperature of 65 • C in 11 min. The highest basicity was observed in calcined peel catalyst (0.93 mmol g − 1) in comparison to that of trunk (0.15 mmol g − 1) and rhizome catalysts (0.2 mmol g − 1). This study also displayed a turnover frequency of 16.85 h − 1 (peel), 7.025 h − 1 (trunk) and 2.317 h − 1 (rhizome). The activation energy of the quinary oil mixture-based biodiesel synthesis with the peel catalyst was 53.625 kJ mol − 1. In this work, the catalyst was found to be highly effective, reusable and produced good quality biodiesel that conforms to the international standards, and thus, it may be considered a potential renewable catalyst for biodiesel industries.
Biodiesel has been referred to as a perfect substitute for diesel fuel due to its numerous promising properties. They are renewable, clean, increase energy security, and improve the environment. The seed oil of Chrysobalanus icaco was characterized using Gas Chromatography-Mass Spectrophotometer (GCMS) and Fourier Transform Infrared Spectroscopy (FTIR). The heterogeneous solid catalyst of periwinkle shell ash was prepared in 3 forms: raw, calcined, and acid-activated. They were characterized using Scanning Electron Microscope (SEM) and FTIR. The results of the SEM analysis revealed the calcined samples to be a better choice because of their larger surface area. The result showed that the oil yield of the used crop was promising for commercial biodiesel production, with Chrysobalanus icaco having a yield of 51.90%. The reusability of the catalyst for continuous reaction runs showed that biofuel yield was still high after five cycles: 92.25–80.60% for calcined periwinkle shell ash (PSA) catalyst and 89.26–78.50% for acid-activated PSA catalyst. The result of the fuel properties of the biodiesel and their blend indicated their suitability for biodiesel production. Methyl ester blends of 20:80 had viscosity that placed them in 2D grade diesel (2.0–4.3 mm2/s), helpful in powering stationary equipment. Other fuel properties, including acid value, pour point, flash point, and density, were within the ASTM D6751 limits for biodiesels. Artificial Neural Network (ANN) was used to compare the experimental value to the simulated value using MATLAB 2020. The seed oil of Chrysobalanus icaco trans-esterified with methanol using Periwinkle Shell Ash (PSA) catalyst was proven to be a good source of biodiesel.
Keywords : Chrysobalanus icaco, Catalyst, Trans-esterification, Artificial neural network
The continuous increase in demand for fossil-based fuel has led to the requirement for an alternative source that must be renewable. Biodiesel is gaining global acceptance as a renewable source of energy. This research focuses on the optimization of the transesterification of waste cooking oil under the CaO-based catalyst derived from a solid ostrich eggshell by different types of machine learning approaches. The objective of the current study is to evaluate and compare the prediction results as well as the simulating efficiency of the biodiesel production yield using heterogeneous catalysts by various machine learning (ML) techniques: type 1 fuzzy logic system (T1FLS), response surface methodology (RSM), adaptive neuro-fuzzy inference system (ANFIS), and type 2 fuzzy inference logic system (T2FLS). The influence of the independent variables, methanol-oil molar ratio (M:O), temperature, catalyst concentration, and reaction time on the production yield was investigated. Among all the input parameters, the reaction temperature is the most influential one based on the aforesaid techniques. The validity of the proposed models has been verified with the help of statistical analysis and multiple linear regression. The values of the determination coefficient (R2) of type 2 fuzzy logic systems are 99.1% whereas R2 of type 1 fuzzy logic systems, response surface methodology, and adaptive neuro-fuzzy inference systems are 95.3%, 93.3%, and 83.2% respectively. All models give close predicted values. However, the type 2 fuzzy logic models were more accurate compared to other models. This proves that it is more capable of handling a wide range of dynamic processes in the chemical industry.
This paper presents the current scenario of solid waste management aspects and its challenges in India, which will benefit developing and low-income countries. The leading cause of waste generation is the growing population and the new lifestyle due to the increased per capita income. Consequently, the magnitude of solid waste is continuously growing along with its compositional diversity. In earlier days, the wastes were organic and could be disposed of in low-lying areas conveniently without causing any adverse impact on the environment. But today, the organic fraction of waste has steeply declined while the inorganic portion has increased manifold. Moreover, wastes from industries, hospitals, construction sites, households, and many other sources severely affect the environment and public health. Also, the chemicals generated from the improper disposal of these wastes enter the air, soil, and water resources, causing hazardous and toxic effects in countries that could not implement the adopted policy framework strictly. A state-of-the-art review is conducted in this paper to further search other primary and prevalent reasons behind the inability of proper waste management and to find a real solution.
A solid catalyst was prepared from waste filter cake (WFC) from a sugar beet processing plant and used, after calcination at 900 °C within 2 h, for biodiesel production from rapeseed oil and methanol. The calcined WFC (CFC) catalyst was characterized by XRF, FTIR, XRD, TGA/DTG, TPDe, TPD-CO2, SEM, N2 physisorption, and Hg porosimetry. The CFC is a CaO-based catalyst with a rigid, sustainable macroporous structure with the largest particles of 2.0 × 0.5 µm, a specific surface area of 7.3 m²/g, and a basicity of 0.27 mmol/g. It provides high conversion of 97.9% in 1 h at the methanol-to-oil molar ratio of 9:1, the temperature of 60 °C, and the catalyst loading of 10% of the oil mass. Its catalytic efficiency is comparable to the WFC-based nanocatalysts and CaO-based catalysts from natural sources. CFC was reused twice with a negligible decrease in catalytic activity, ensuring a FAME content above 97% in 1 h. The biodiesel produced from rapeseed oil over the CFC catalyst has good fuel properties that fulfill most of EN 14214. Therefore, WFC is a promising source of a low-cost, highly active, basic, and environmentally friendly CFC catalyst, which could reduce biodiesel production costs. From this point of view, this catalyst has great potential for developing the process at the commercial level.
Clean, renewable, and sustainable energy is required daily to improve social, economic, and environmental health, leading to economic development and productivity. The aim of the work has deliberated on the reoccurrence of renewable energies to assist in the mitigation of climate change and environmental health excellently. This work aims to determine whether renewable energy sources are viable and study how a shift from fossil fuel-based energy sources to renewable energy sources would assist in reducing climate change and its impact. State of the art in biofuels and energy generation from lignocellulosic biomasses has shown that applying advanced technologies such as biorefinery and bioreactors to the chemical transformation process is a sustained strategy. To optimally exploit biorefineries' potential, government policies must favor technological innovations in universities and in an industry that can help produce high-value fuels and products from various biomasses. This work deliberated to light the prospects allied with renewable energy sources; energy security, access to energy, social and economic progress, and climate change mitigation to reduce ecological and health impacts.
Heterogeneous catalysis has provided a viable alternative to homogeneous catalysis for the production of low-cost biodiesel fuel, overcoming the constraints of homogeneous catalysis. In recent years, there have been numerous breakthroughs in the development of high-efficiency and cost-effective heterogeneous-based catalysts for catalytic transesterification of triglycerides (oil or fat) to biodiesel. Because of its simplicity and low cost, the heterogeneously catalyzed transesterification reaction has long been considered the most feasible biodiesel synthesis method. The intrinsic features of nine types of heterogeneous catalysts, including heteropolyacid, zeolite, hydrotalcite, carbon and waste materials, metal, metal oxide, enzyme, and ion exchange resins, which are commonly used in today's biodiesel research, have been studied in detail. Emphasis is placed on versatile catalysts with high activity and low production cost as they make biodiesel production more practical, efficient and sustainable. Key parameters that influence the activity of heterogeneous catalysts as well as challenges and opportunities that could motivate future exploration are also highlighted.
In this research, a green solid catalyst of phosphomolybdic acid (HPA) prated on Chitosan was synthesized to produce biodiesel. The prepared catalyst was characterized using Fourier Transform Infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray (EDX), X-ray diffraction (XRD), and XRF analyses. The catalyst was applied in microwave-assisted trans-esterification of Pomegranate oil, and the biodiesel production process was optimized by response surface methodology based on central composite design (RSM-CCD). The effect of influential reaction parameters, including time (33–142 min), catalyst weight (0.15–5.6 wt%), and methanol to oil molar ratio (3.3:1–17:1), were investigated. The maximum biodiesel yield of 95% was obtained in a short time (74 min) using the catalyst weight of 1.25 wt% and methanol to oil molar ratio of 6:1 at the temperature of 65 °C. The catalyst was reused six times without any significant reduction in catalyst activity. The H NMR spectroscopy was employed to compare Pomegranate oil and biodiesel. The kinetic results of transesterification via microwave-assistant have good agreement with first-order kinetics as well as the activation energy and Arrhenius constant are 50 kJ/min and 16.47×10⁷ min⁻¹, respectively. As a result, Pomegranate biodiesel has high quality. The physicochemical properties of Pomegranate biodiesel under the optimal condition agreed with the ASTM standard. In conclusion, phosphomolybdic acid/Chitosan as a catalyst has a high potential for biodiesel production on a large scale.
Modern times are facing a massive crisis with rising global energy demand and carbon dioxide emission due to the consumption of fossil fuels. The depletion of petroleum-derived fuel has created a demand for an alternative fuel source. Fossil fuels are also regarded as conventional fuels, are the prime sources of non-renewable energy, whose loss cannot be sustained in years. According to the 2019 global statistical review of world energy, there is a 0.5% increased carbon dioxide emission rate and 1.3% primary energy consumption worldwide. These increased rates are a triggered alarm to humankind and the environment. Meanwhile, renewable sources such as biofuel show a potential usage with low carbon dioxide emission, less polluting and can be created from biomass in the forms of organic waste. Moreover, they are effective against greenhouse gases (GHGs) emission and the impact of changing climate from transports and vehicles. Today the biofuel research is performed globally because of the two fundamental properties, sustainability and renewability. There are many effective biomass production sources and fall into three categories, including the First generation, Second generation and Third generation biofuel. The first generation comprises food crop-related biomass, whereas the second generation includes lignocellulosic biomass, and the third generation features potential renewable sources in the form of algal biomass. The paper aims to review the various sources of biofuels and the methods used in the production, and discuss its advantages and sustainability.
The CaO-Al2O3-SiO2-CaSO4-based solid catalysts developed from calcium carbide residue (CCR) was investigated for biodiesel production using waste lard in optimisation and regeneration studies. The catalysts were synthesized by calcination of the CCR at the temperature of 500, 700 and 900 °C and sulphonation, to give Cat500, Cat700 and Cat900 respectively. The catalysts were studied to optimise the biodiesel yield from waste lard using combinations of response surface methodology (RSM) and meta-heuristic algorithms such as particle swarm optimisation (PSO), genetic algorithm (GA) and firefly algorithm (FA). The process parameters investigated were methanol: oil molar ratio (6–12 w/w), reaction temperature (50–60 °C), reaction time (1–4 h), catalyst quantity (5–15 % (w/w)) and catalyst type (Cat500, Cat700 and Cat900). The study revealed that the 12:1 MeOH: oil molar ratio, 59.97 °C reaction temperature, 1 h reaction time, 5% (w/w) catalyst quantity and Cat500 catalyst type gave biodiesel yield of 96.35%. The performance of the meta-heuristic algorithms based on the optimisation output compared well with that of the RSM. This study concludes that the catalyst developed from the CCR can be regenerated after the ninth cycle of usage and re-utilised for efficient biodiesel production.
The efforts have been made to review phyllosilicate derived (clay-based) heterogeneous catalysts for biodiesel production via lignocellulose derived feedstocks. These catalysts have many practical and potential applications in green catalysis. Phyllosilicate derived heterogeneous catalysts (modified via any of these techniques like acid activated clays, ion exchanged clays and layered double hydroxides) exhibits excellent catalytic activity for producing cost effective and high yield biodiesel. The combination of different protocols (intercalated catalysts, ion exchanged catalysts, acidic activated clay catalysts, clay-supported catalysts, composites and hybrids, pillared interlayer clay catalysts, and hierarchically structured catalysts) was implemented so as to achieve the synergetic effects (acidic-basic) in resultant material (catalyst) for efficient conversion of lignocellulose derived feedstock (non-edible oils) to biodiesel. Utilisation of these Phyllosilicate derived catalysts will pave path for future researchers to investigate the cost-effective, accessible and improved approaches in synthesising novel catalysts that could be used for converting lignocellulosic biomass to eco-friendly biodiesel.