Towards integrated sustainable biofuel and chemical production: An application of banana pseudostem ash in the production of biodiesel and recovery of lignin from bamboo leaves

Recycling the powder of spent alkaline batteries as a sustainable and reusable catalyst in producing biodiesel from waste cooking oil

Alkaline batteries are widely used in contemporary society. However, their black powder, which contains metals, categorizes them as hazardous waste, posing environmental risks if not disposed of correctly. Similarly, waste cooking oil (WCO), frequently produced in homes and restaurants, is often discarded into the environment as waste. In this study, the spent black powder from alkaline batteries was effectively utilized as a catalyst for biodiesel generation from WCO. This catalyst, containing carbonaceous materials, MnO2, ZnO, and K, facilitated both esterification and transesterification processes. It featured a Brunauer-Emmett-Teller (BET) value of 31.87 m2/g. Response Surface Methodology with Central Composite Design (RSM-CCD) was used to evaluate the influence of key variables on production efficiency. The highest biodiesel yield (99.23%) was attained with a methanol-to-oil ratio of 16:1, a temperature of 70 °C, a catalyst mass of 3 wt%, and a production time of 160 min. The regeneration process revealed that n-hexane effectively removes glycerol and biodiesel residues from the catalyst. Additionally, the catalyst demonstrated strong reusability for up to five cycles, with a significant decline in catalytic activity observed after the fifth cycle. The process demonstrated an activation energy of 22.046 kJ/mol and a pre-exponential factor of 62.878 min⁻1. It was characterized as endothermic (ΔH: 19.274 kJ/mol) and non-spontaneous (ΔG: 94.666 kJ/mol). The economic assessment in this study showed that the production cost of 1 kg of biodiesel using a catalyst derived from waste batteries is $0.579, demonstrating its cost-effectiveness compared to alternative methods for large-scale applications. Fourier Transform Infrared Spectroscopy (FTIR), 13C-NMR, and 1H-NMR analyses validated the catalyst's effectiveness in converting WCO to biodiesel. Therefore, it is suggested that this catalyst be tested at an industrial scale.

Catalytic solid derived from residual bean husk biomass applied to sustainable biodiesel production: preparation, characterization, and regeneration study

This study investigates the use of bean husks as a precursor for the synthesis of an efficient and regenerable catalyst, with the aim of offering an economical and sustainable alternative for biodiesel production. Residual bean shell biomass (RBBH) was calcined at different temperatures (350-500 °C) and times (1-4 h) to determine the optimum synthesis conditions. The catalyst obtained was characterized by various methods, such as X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Thermogravimetric Analysis (TG/DTG). The results showed that the catalyst contains metal oxides and carbonates as active sites. In addition, the influence of reaction conditions was evaluated in the ranges of temperature (60-120 °C), time (0.5-2.5 h), MeOH : oil molar ratio (12 : 1-28 : 1) and catalyst concentration (2-10% by weight). The maximum ester content (97.6%) was achieved at 120 °C, 2 h, a MeOH : oil molar ratio of 20 : 1 and 8% catalyst. After partial deactivation of the solid catalyst, it was regenerated with KOH, yielding biodiesels with an ester content of over 75% in three consecutive cycles, demonstrating its efficiency and potential for continuous use.

Lignin valorization through the oxidative activity of β-etherases: Recent advances and perspectives

The increasing interest in lignin, a complex and abundant biopolymer, stems from its ability to produce environmentally beneficial biobased products. β-Etherases play a crucial role by breaking down the β-aryl ether bonds in lignin. This comprehensive review covers the latest advancements in β-etherase-mediated lignin valorization, focusing on substrate selectivity, enzymatic oxidative activity, and engineering methods. Research on the microbial origin, protein modification, and molecular structure determination of β-etherases has improved our understanding of their effectiveness. Furthermore, the use of these enzymes in biorefinery processes is promising for enhancing lignin breakdown and creating more valuable products. The review also discusses the challenges and future potential of β-etherases in advancing lignin valorization for biorefinery applications that are economically viable and environmentally sustainable.

High removal of volatile organic compounds on hierarchical carbons prepared from agro-industrial waste of banana fruit production for air decontamination

Activated carbons were prepared from residues from agro-industrial banana production (banana pseudostem) and evaluated in the capture of five different volatile organic compounds (VOCs): dichloromethane, chloroform, ethyl acetate, hexane, and cyclohexane. The biomass was first submitted to a hydrothermal treatment in the presence of KOH or ZnCl2 as activating agents, followed by a dry pyrolysis. This new advance in methodology contributes to producing activated carbons with hierarchical porosity and high surface areas (701-1312 m2 g-1), promoting increased interest in managing waste from banana fruit agricultural production. VOC capture studies were performed by thermal analysis, and capture capacities were similar to or higher than those presented in the literature. Higher adsorption capacities were related to the amount of available micropores, and the capture capacity was enhanced by the contribution of small mesopores. As the highest adsorbed amounts of dichloromethane (933 mg g-1 at 25 °C) were obtained for the material activated with ZnCl2 (1:3), further studies were carried out for this system. The experimental data was fitted using a pseudo-first-order kinetic model. A study was carried out in different atmospheres (He, N2, air), showing that co-adsorption is occurring. Under simulated environmental conditions, the capture capacity decreased slightly at equilibrium, and the new adsorbent was used for up to ten cycles without significantly losing its efficiency, indicating good application in the field.

Catalytic Performance Investigation of Alkali and Bifunctional Catalysts Derived from Lignocellulosic Biomasses for Biodiesel Synthesis from Waste Frying Oil

In this study, alkali and bifunctional catalysts were synthesized for waste frying oil methyl ester (WFOME) synthesis. Coffee husk (CH) and CH blended with Eragrostis tef straw (TS) (CH-TS) lignocellulosic biomasses (LBs) were utilized during the catalysts' synthesis. The alkali catalysts were CH and CH-TS ashes, both modified by KNO3 impregnation. They are designated as C-45 and C-Mix, respectively. Zirconia (ZrO2) promoted CH ash catalysts via precipitation followed by impregnation (Bic-PP) and in situ precipitation-impregnation (Bic-Dm) were the bifunctional ones. CH and CH-TS chars were the supporting frameworks during the catalysts' composite materials (CCMs) preparation. The combustion performance of LBs and CCMs was evaluated and associated with the catalysts' physicochemical properties. Using XRD, SEM, FTIR, alkalinity, TOF, and BET surface area analysis, catalysts were characterized. The combustion performance of the LBs was in the order of TS > CH-TS > CH. Among CCMs, the highest combustion performance was for CCM-Mix (KNO3/(CH-TS char)) and the lowest was for CCM-45 (KNO3/ CH char). The C-Mix catalyst was a light green powder due to the reaction between inorganic components, whereas C-45 was dark gray due to the presence of unburned char. The CCMs for bifunctional catalysts had moderate combustion performance and yielded light gray powdered catalysts containing tetragonal ZrO2. The optimum WFOME yields were 98.08, 97, 92.69, and 93.05 wt % for C-Mix, C-45, Bic-Dm, and Bic-PP assisted WFO transesterification, respectively. The results were obtained at a reaction temperature of 65 °C, time of 1 h, and methanol to WFO molar ratio of 15:1 using catalyst amounts of 5 and 7 wt % for the alkali and bifunctional catalysts, respectively. The greatest moisture resistance was offered by the C-Mix catalyst. The best reusability was for the C-45 catalyst. Catalysts' deactivation modes include active site leaching and poisoning.

Cleaner Biofuel Production via Process Parametric Optimization of Nonedible Feedstock in a Membrane Reactor Using a Titania-Based Heterogeneous Nanocatalyst: An Aid to Sustainable Energy Development

Membrane technology has been embraced as a feasible and suitable substitute for conventional time- and energy-intensive biodiesel synthesis processes. It is ecofriendly, easier to run and regulate, and requires less energy than conventional approaches, with excellent stability. Therefore, the present study involved the synthesis and application of a highly reactive and recyclable Titania-based heterogeneous nanocatalyst (TiO2) for biodiesel production from nonedible Azadhiracta indica seed oil via a membrane reactor, since Azadhiracta indica is easily and widely accessible and has a rich oil content (39% w/w). The high free fatty acids content (6.52 mg/g KOH) of the nonedible oil was decreased to less than 1% via two-step esterification. Following the esterification, transesterification was performed using a heterogeneous TiO2 nanocatalyst under optimum conditions, such as a 9:1 methanol-oil molar ratio, 90 °C reaction temperature, 2 wt.% catalyst loading, and an agitation rate of 600 rpm, and the biodiesel yield was optimized through response surface methodology (RSM). Azadhiracta indica seed oil contains 68.98% unsaturated (61.01% oleic acid, 8.97% linoleic acid) and 31.02% saturated fatty acids (15.91% palmitic acid, 15.11% stearic acid). These fatty acids transformed into respective methyl esters, with a total yield up to 95% achieved. The biodiesel was analyzed via advanced characterization techniques like gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR), whereas the catalyst was characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and Fourier transform infrared spectroscopy (FT-IR). Due to its physicochemical properties, Azadirachta indica seed oil is a highly recommended feedstock for biodiesel production. Moreover, it is concluded that the Titania-based heterogeneous nanocatalyst (TiO2) is effective for high-quality liquid fuel synthesis from nonedible Azadirachta indica seed oil in a membrane reactor, which could be an optional green route to cleaner production of bioenergy, eventually leading to sustenance, robustness, and resilience that will aid in developing a holistic framework for integrated waste management.

Enhancing Sustainable Production of Fatty Acid Methyl Ester from Palm Oil Using Bio-Based Heterogeneous Catalyst: Process Simulation and Techno-Economic Analysis

A new sustainable solid carbon catalyst has been developed for biodiesel synthesis using pyrolytic coconut shell ash (CSA). The CSA support was loaded with various amounts of potassium carbonate (K2CO3), and response surface methodology with a central composite design was used to optimize the transesterification process. The best-performing catalyst was the 30 wt % K2CO3/CSA catalyst. The optimal conditions included a catalyst loading of 3.27 wt %, methanol:oil molar ratio of 9.98:1, reaction time of 74 min, and temperature of 65 °C, resulting in an obtained biodiesel yield of 97.14%. This catalyst was reusable for up to four cycles, but a reduction in the biodiesel yield was observed due to potassium ion leaching during the recovery process. A techno-economic analysis to assess the financial viability of the project revealed a net present value of 5.16 million USD for a project lifetime of 20 years, a payback period time of 2.49 years, and an internal rate of return of 44.2%. An environmental assessment to evaluate the impact of global warming potential from the production of biodiesel revealed a lower level of carbon dioxide emission (1401.86 ton/y) than in the conventional process (1784.6 ton/y).

Biological valorization of lignin-derived vanillin to vanillylamine by recombinant E. coli expressing ω-transaminase and alanine dehydrogenase in a petroleum ether-water system

Vanillylamine, as an important drug precursor and fine chemical intermediate, has great economic value. By constructing a strategy of double enzyme co-expression, one newly constructed recombinant E. coli HNIQLE-AlaDH expressing ω-transaminase from Aspergillus terreus and alanine dehydrogenase from Bacillus subtilis was firstly used aminate lignin-derived vanillin to vanillylamine by using a relatively low dosage of amine donors (vanillin:L-alanine:isopropylamine = 1:1:1, mol/mol/mol). In addition, in a two-phase system (water:petroleum ether = 80:20 v/v), the bioconversion of vanillin to vanillylamine was catalyzed by HNIQLE-AlaDH cell under the ambient condition, and the vanillylamine yield was 71.5%, respectively. This double-enzyme HNIQLE-AlaDH catalytic strategy was applied to catalyze the bioamination of furfural and 5-hydroxymethylfurfural with high amination efficiency. It showed that the double-enzyme catalytic strategy in this study promoted L-alanine to replace D-Alanine to participate in bioamination of vanillin and its derivatives, showing a great prospect in the green biosynthesis of biobased chemicals from biomass.