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Malaysia is rich in palm oil plantations, where oil palm wastes (OPWs) are one of the readily accessible biomass resources. OPWs has the potential to be used as a fuel for electricity generation. Hence, the evaluation of OPWs co-firing for one of Malaysia's 500 MW utility boilers was executed numerically. Three types of OPWs were tested including empty fruit bunches (EFB), palm kernel shell (PKS), and palm mesocarp fibres (PMF). The predicted furnace exit gas temperature (FEGT) from the numerical model was validated against the actual FEGT from the power plant where the current boiler is situated, revealing a difference of less than 10%. The nose area temperature was predicted to exceed the cap of 1200°C in OPWs co-firing cases due to higher volatile matter (VM) in OPWs than the baseline of pure coal case, leading to higher levels of volatile release. When co-firing with OPWs, the predicted unburned carbon (UBC) at the boiler's outlet is lower because OPWs-coal blends contain less fixed carbon (FC) than the pure coal blend. UBC levels were anticipated to be lower than the loss of ignition (LOI) limit in all cases, highlighting its positive impact on carbon reduction. Slightly lowered mill performance was observed as a result of the calculated OPWs fuel flow surpassing the normal operation in the power plant to make up for the low gross calorific value (GCV) of OPWs while meeting the required load from the boiler. OPWs co-firing was predicted to emit lower carbon monoxide (CO) and carbon dioxide (CO2) than baseline coal due to lower FC. Nonetheless, higher thermal nitrogen oxides (NOx) were predicted due to the higher flame temperature created by OPWs co-firing. Even so, it is recommended that the ash mineral composition be included in future numerical studies since the ash minerals may have an effect on the emitted NOx.

Increasing the amount of hydrogen (H2) in natural gas mixtures contributes to gas turbine (GT) decarbonisation initiatives. Hence, the swirling flame characteristics of natural gas mixtures with H2 are investigated in the current work using a numerical assessment of a single swirl burner, which is extensively employed in GT combustors. The baseline numerical and experimental cases pertained to natural gas compositions largely consisting of methane (CH4). The results show that the numerical model adequately describes the swirling component of the flame observed in the experiment. Altogether, the findings show that hydroxyl (OH) radical levels increase in H2-enriched CH4 flames, implying that greater OH pools are responsible for the change in flame structure caused by considerable H2 addition. The addition of 10 % H2 is predicted to raise the peak flame temperature by 4 % compared to the baseline CH4 flame. Therefore, adding 10 % H2 into a GT combustor without any flowrate tuning raises the risk of turbine material deterioration and increased thermal NOx emission. Due to the lower volumetric Lower Heating Value (LHV) of H2, which needs a higher volumetric fuel flow rate than burning natural gas/CH4 at the same thermal output, the addition of 2 % H2 is predicted to reduce the peak flame temperature by 4 % compared to the baseline CH4 flame. Hence, if 2 % H2 is fed into a GT combustor without any flowrate tuning, the required load may not be obtained. When compared to the baseline CH4 case, the addition of 5 % H2 is predicted to provide almost identical peak flame temperature, which can be postulated that the addition of 5 % H2 can produce roughly the same peak flame temperature as the pure CH4 flame because the Wobbe Index is comparable. Therefore, it reveals that incorporating 5 % H2 in the natural gas-fired GT combustor with nearly no modification is viable. More research, however, is required to fully capture the flame structure and strain for assessing transient-related phenomena such as flashback and blow off by raising the H2 proportion and utilising a higher precision turbulence model.

5-Hydroxymethylfurfural (5-HMF) is a potential value-added product gaining popularity due to its wide range of applications. Glucose is widely used for 5-HMF production because it is abundant and more cost-effective than other resources. In the current research, a combination of microwave irradiation and low transition-temperature mixture (LTTM) for 5-HMF production was sustainably created. A preliminary study was conducted to derive 5-HMF using LTTM as a green solvent in various ratios of glucose: LTTM (MA/ChCl): water (10:100:15) and (10:48:100) via microwave heating at 90 °C for 10–60 min reaction time. The product analysis revealed that the 10:100:15 combination ratio of glucose: LTTM: water produced more 5-HMF (20.5%) than the 10:48:100 (0.28%) ratio. Following the preliminary results, an optimization study was conducted, focusing on the reaction temperature, LTTM mass, and water to assess the impact on 5-HMF yield and glucose conversion, using CCD in Design-Expert software. The quadratic model fit for 5-HMF yield and the 2FI model for glucose conversion yielded R2 values of 0.9861 and 0.8610, respectively. Both responses had a significant p value of 0.0061 for glucose conversion and

The energy demand in Malaysia has shown a dramatic increase over the last few years: with natural gas and coal being the primary contributors. Nevertheless, due to declining in fossil fuel reserves coupled with negative environmental impacts, shifting to sustainable renewable energy for meeting the future energy demand is recommended. Since Malaysia is rich with natural resources, utilization of biomass energy (bioenergy/biofuel) as the alternative energy is promising to be further explored. Therefore, this review paper intents to discuss the current scenario of different types of biomass energy in Malaysia along with the up-to-date local biomass energy–related environmental policy (from 2016 onwards). In addition, challenges and barriers for large-scale implementation of the biomass energy in Malaysia are to be discussed. Overall, this review paper is interesting as it can assist in promoting the biomass utilization as energy source, and to ensure the future growth of biomass energy market in the country along with its effective implementation while alleviating poor disposal problem and to create job employment opportunities. Furthermore, a collective effort to expand potential biomass feedstocks, apart from oil palm, should be emphasized to encourage the renewable energy production diversification in the nation.

Under the Paris agreement, Malaysia has set its target of reducing greenhouse gas emissions by 45% by 2030 (35% of which is on an unconditional basis), having 2005 as the base year. Carbon capture and utilization, together with an increased use of renewable energy sources, will be one of the main pillars of the national policy towards achieving this goal. Malaysia produces on an annual basis more than 100 million tons of biomass and is the second largest palm oil producer in the world. Thus, the focus of this study is the biogenic sources of carbon dioxide, and more specifically biomass power plants and palm oil mill effluent-based biogas power plants, operating at different scales across the country. Our objective is to map the existing carbon sources as well as the potential carbon receivers as many as possible (in both regions, East and West Malaysia), estimate the annual amount of produced carbon dioxide and identify the most economically viable business models for the development of symbiotic schemes based on the capture and reuse of carbon dioxide.

One of the greatest challenges in biorefinery is to reduce biomass' recalcitrance and enable valorization of lignin into higher value compounds. Likewise, green solvents and hydrothermal liquefaction (HTL) with feasible economic viability, functionality, and environmental sustainability have been widely introduced in extraction and conversion of lignin. This review starts with the underscore of disadvantages and limitations of conventional pretreatment approaches and role of green solvents in lignin extraction. Subsequently, the effect of process parameters along with the reaction mechanisms and kinetics on conversion of lignin through HTL were comprehensively reviewed. The limitations of green solvents in extraction and HTL of lignin from biomass were discussed based on the current advancements of the field and future research scopes were also proposed. More details info on HTL of biomass derived lignin which avoid the energy-intensive drying procedures are crucial for the accelerated development and deployment of the advanced lignin biorefinery.

The generation of hydrogen-enriched synthesis gas from catalytic steam gasification of biomass with in-situ CO2 capture utilizing CaO has a high perspective as clean energy fuels. The present study focused on the process modeling of catalytic steam gasification of biomass using palm empty fruit bunch (EFB) as biomass for hydrogen generation through experimental work. Experiment work has been carried out using a fluidized bed gasifier on a bench-scale plant. The established model integrates the kinetics of EFB catalytic steam gasification reactions, in-situ capturing of CO2, mass and energy balance calculations. Chemical reaction constants have been calculated via the parameters fitting optimization approach. The influence of operating parameters, mainly temperature, steam to biomass, and sorbent to biomass ratio, was investigated for the hydrogen purity and yield through the experimental study and developed model. The results predicted approximately 75 vol% of the hydrogen purity in the product gas composition. The maximum H2 yield produced from the gasifier was 127 gH2/kg of EFB via experimental setup. The increase in both steam to biomass ratio and temperature enhanced the production of hydrogen gas. Comparing the results with already published literature showed that the current system enables to produce a high amount of hydrogen from EFB.

Bamboo is the fastest-growing plant and is abundant in Malaysia. It is employed as a starting material for activated carbon production and evaluated for its potential in CO2 capture. A single-stage phosphoric acid (H3PO4) activation is adopted by varying the concentrations of H3PO4 between 50 and 70 wt.% at a constant temperature and holding time of 500°C and 120 min, respectively. The bamboo-based activated carbons are characterized in terms of product yield, surface area, and porosity, as well as surface chemistry properties. Referring to the experimental findings, the prepared activated carbons have BET surface area of >1000 m2 g-1, which implies the effectiveness of the single-stage H3PO4 activation. Furthermore, the prepared activated carbon via 50 wt.% H3PO4 activation shows the highest BET surface area and carbon dioxide (CO2) adsorption capacity of 1.45 mmol g-1 at 25°C/1 bar and 9.0 mmol g-1 at 25°C/30 bar. With respect to both the characterization analysis and CO2 adsorption performance, it is concluded that bamboo waste conversion to activated carbon through H3PO4 activation method is indeed promising.

The heavy utilization of fossil fuels and efforts to reduce carbon footprint worldwide led to the development of biofuels. Therefore, this paper investigates the kinetic study for the catalytic cracking reaction of refined rubber seed oil (RSO) for bio gasoline production using Cu/ZSM5 catalyst. The reaction was carried out at 440 ᵒC and at atmospheric condition within the WHSV range of 1.5–3.5 h−1 in a fixed bed reactor. The kinetic rate constants were estimated based on 3, 4 and 5 lumped models sequentially. In the 3-lump model, the RSO was converted mostly to organic liquid product (OLP) and only forming some undesired gas and coke. Both refined RSO and OLP contributed to the formation of gas and coke products in the 4-lump model. In the 5-lump model, the RSO and OLP both favoured gasoline production. The absence of gaseous product suggests that no secondary cracking reactions occurred in gasoline fractions, but coke deposition was formed due to condensation. The high R2 squared values suggest that the predicted model data was in good agreement with the experimental data.

Hydrogen (H2) production via biomass gasification has demonstrated to be a viable method to obtain environmental-friendly fuel. In this paper, steady-state modeling of palm kernel shell (PKS) steam gasification pilot-plant is developed and validated using experimental data. The process optimization study for the gasification of PKS utilizing the coal bottom ash as a catalyst is conducted in the continuous advanced fluidized bed technology pilot-scale gasification plant to determine the optimum conditions to produce maximum H2 and syngas composition. The optimum conditions for maximum H2 and syngas composition are a temperature of 625 °C, PKS particle size of 1–2 mm, and coal bottom ash to PKS percentage of 7.5 %. The optimum operating condition results are then validated in the pilot-scale gasification system. Steady-state simulation of the pilot scale biomass gasification plant is then developed using Aspen Plus® and validated using the experimental data.

Zeolite β supported bimetallic Fe and Ni catalysts have been prepared using sequential impregnation method and calcined at temperatures between 500-700 ºC. The catalytic activity of these catalysts in a steam gasification of palm kernel shell was tested in a fixed-bed quartz micro-reactor at 700 ºC. Both Fe and Ni active metals present in FeNi/BEA and NiFe/BEA catalysts are corresponding to Fe2O3 and NiO. Different calcination temperatures and different sequence in metal addition have a significant effect to the catalytic activity where FeNi/BEA (700) shows the highest hydrogen produced than other catalysts.

The presence of phytochemical constituents, such as alkaloids, flavonoids, polyphenols, fatty acids, etc., within various parts of Carica papaya is highly valuable for various health and medicinal benefits. This paper aimed to review various sample preparation and extraction methods, including conventional extraction and greener extraction methods of phytochemical compounds from Carica papaya. In this review, the methodology used was based on comprehensive data searched from the Web of Science for literature review and technology benchmarking. An in-depth discussion, including advantages and drawbacks, of each sample and extraction methods of Carica papaya Linn. are presented and outlined. Furthermore, key solutions were proposed to overcome issues faced in conventional extraction methods and the challenges encountered in larger extraction scale ratios were also presented to complement the movement towards more sustainable and greener extraction processes.

The potential of lignin is huge mainly in refining into biofuels and useful chemicals. Tropical countries have large reserve of biomass; however, lignin is underutilized. Hence, this paper aims to evaluate the lignin potential from biomass and current utilization level in tropical countries such as Brazil, Africa, and Southeast Asia. This paper relevant information is derived from multiple sources, included papers from ISI and Scopus indexed journals, international databases, and online patent search engine. In short, Brazil, has the largest lignin potential, mainly from sugarcane industry, and the highest lignin utilization level at TRL8. Africa had limited information and the least reported amount of studies on biomass available in the studied regions. Southeast Asia countries have oil palm and sugarcane as their largest lignin sources, and a TRL4 lignin utilization level. In Malaysia, oil palm refinery residues are the largest sources of lignin, which are readily to be extracted and processed into value-added products. Lignin utilization industry is also supported by some government policies. In this case, integrated biorefinery is a promising approach in achieving feasible conversion and utilization of lignin in Malaysia, where it adds value to various agricultures wastes produced, while also reducing the waste disposal problems.

Hydrodeoxygenation (HDO) of vegetable oil is one of the promising key processes designed for a possible convenient method for automotive clean fuel production. The HDO of rubber seed oil into diesel range hydrocarbon over non-sulphided monometallic (Ni/γ-Al2O3 and Mo/γ-Al2O3) catalysts were investigated. The catalysts were synthesized via conventional wet impregnation method using 3 wt.%, 12 wt.% and 15 wt.% Ni and Mo loading over γ-Al2O3 support, to examine the influence of metal loading on catalytic activity, coke deposition, and reaction routes. The synthesized catalysts were subjected to characterization techniques including XRD, FESEM coupled with EDX, BET, TEM, TGA, ICP-OES and H2TPR. All the catalysts were tested for HDO reaction at 623.15 K, 3.5 MPa, H2/oil of 1000 N (cm3/cm3) with WHSV = 1 h−1 in a continuous flow fixed bed tubular reactor. The hydrocarbon products were analyzed using gas chromatography, and intermediates were identified using GC–MS. The Ni supported catalysts showed comparatively higher surface area, small particle size, homogeneous dispersion of particles, higher crystallinity and lower reduction temperature, low coke deposition. Proposed reaction mechanism suggests the decarboxylation (DCO2) reaction occurred mainly over Ni supported catalysts. Whereas, higher Ni loading reduced the extent of decarboxylation (DCO2) reaction. Additionally, Mo supported catalysts allowed the deoxygenation reaction to occur and higher Mo loading enhanced the extent of hydrodeoxygenation (HDO). The triglycerides conversion for all the catalysts was 99.9%. The catalysts with higher metal loading showed overall higher catalytic activity for hydrodeoxygenation of RSO. 15 wt.% Ni loading produced higher hydrocarbon yield (55.1 wt.%) whereas, 15 wt.% Mo loading produced up to 61.7 wt.%. Mo comparatively produced high amount of C16 (15.7 wt.%), and C18 (30.7 wt.%) hydrocarbons. Whereas, Ni produced mainly C15 (20.9 wt.%) and C17 (20.3 wt.%) hydrocarbons. Significant findings were observed on hydrocarbon yield, intermediates, and amount of coke formation. Mo supported catalysts shows significant HDO activity with less concentration of oxygenated component in the mixture. Besides Mo supported catalysts exhibit the high amount of coke deposition compared to Ni supported catalysts.

Extracts of Aquilaria sinensis possess pharmacological activity that has been widely used in traditional medicines since ancient times. In this study, techno-economic assessment was conducted for extraction of volatile oil from abundant biomass (lignified ring) and resin of A. sinensis to evaluate their respective economic feasibility using supercritical carbon dioxide (SC-CO2) extraction in Malaysia. The assessment revealed that for a production capacity of 5280 kg/y volatile oil, the total capital investment (TCI) was $ 7.11 million from summation of fixed capital cost and working capital. In terms of operating expenditure (OPEX), the volatile oil extracted from resin and lignified ring of A. sinensis required $ 81.96 million and $ 52.39 million, respectively. The selling price of volatile oil from resin and lignified ring were estimated to be $ 0.025 million/kg and $ 0.0125 million/kg, respectively. Both volatile oil extracted from resin and lignified ring showed a positive net profit which indicated their profitability. In addition, a cradle-to-gate analysis of life-cycle assessment (LCA) was performed, whereby the extraction process contributed the highest impact towards the environment due to its high energy consumption. Nevertheless, this study estimated that the process might reduce the environmental impacts by approximately 90% when the technology readiness levels (TRLs) reach the level of 9–10. These findings are beneficial in providing preliminary insights in terms of economic and environmental aspects for volatile oil extraction using SC-CO2 technology.

The volumetric adsorption kinetics of carbon dioxide (CO2) onto the synthesized palm kernel shell activated carbon via single-stage CO2 activation and commercial Norit® activated carbon were carried out at an initial pressure of approximately 1 bar at three different temperatures of 25, 50, and 100 °C. The experimental kinetics data were modelled by using the Lagergren’s pseudo-first-order model and pseudo-second-order model. Comparing these two, the non-linear pseudo-second-order kinetics model presented a better fit towards CO2 adsorption for both adsorbents, owing to its closer coefficient of determination (R2) to unity, irrespective of the adsorption temperature. In addition, kinetics analysis showed that the corresponding kinetics coefficient (rate of adsorption) of both activated carbons increased with respect to adsorption temperature, and thereby, it indicated higher mobility of CO2 adsorbates at an elevated temperature. Nevertheless, CO2 adsorption capacity of both activated carbons reduced at elevated temperatures, which signified exothermic and physical adsorption (physisorption) behaviour. Besides, process exothermicity of both carbonaceous adsorbents can be corroborated through activation energy (Ea) value, which was deduced from the Arrhenius plot. Ea values that were in range of 32–38 kJ/mol validated exothermic adsorption at low pressure and temperature range of 25–100 °C. To gain an insight into the CO2 adsorption process, experimental data were fitted to intra-particle diffusion model and Boyd’s diffusion model, and findings revealed an involvement of both film diffusion and intra-particle diffusion during CO2 adsorption process onto the synthesized activated carbon and commercial activated carbon.

The supercritical fluid extraction of Carica papaya linn. leaves in the presence of CO2 solvent and ethanol modifier was carried out with respect to four operating parameters, namely temperature (40–60 °C), pressure (18–30 MPa), solvent flow rate (3–6 mL/min) and co-solvent ratio (3 – 5 vol%), for the maximization of global extract yield of Carica papaya linn. leaves. The optimized parameters obtained are as follows: temperature of 57.47 °C, pressure of 26.62 MPa, solvent flow rate of 5.43 mL/min and co-solvent ratio of 4.98% with a predicted global extract yield of 0.0806 g. Five density-based solubility models, namely Chrastil, Bian et al., Bartle et al., Sparks et al. and Mendez-Santiago and Teja models were correlated against experimental solubility data. The Mendez-Santiago and Teja model were found to be more accurate with AARD of 1.36% and R2 value of 0.873 due to the non-linearity extraction profiles of papaya leaves.

This research demonstrates the conversion of grape marc into highly carbonaceous and oxygen functionalized porous activated biocarbons (PABs) with a high specific area for CO2 capture. The materials are synthesized using KOH activation at 800 °C and show a high content of micropores and high specific surface areas which can be easily manipulated by varying the amount of KOH. The optimized material PAB3 obtained using KOH/grape marc biochar ratio of 3 displays the highest specific surface area (2473 m2 g−1), high micropore volume (0.72 cm3 g−1) and a pore diameter of 0.74 nm. Owing to its highly developed porosity and excellent textural parameters, PAB3 exhibits a high CO2 adsorption of 6.2 mmol g−1 at 0 °C/1 bar and 26.8 mmol g−1 at 0 °C/30 bar. It is often considered challenging to synthesize a CO2 adsorbent with all-round performance for CO2 capture under diverse conditions of temperature and pressure. The optimized material PAB3 is also found to be thermally stable which when coupled with its superior CO2 capture performance presents a promising candidature in the field of carbon capture. Furthermore, the excellent features of the synthesized material suggest that these materials could be extended to several other adsorption related fields.

The process optimization of hydrodeoxygenation of rubber seed oil was investigated on diesel range hydrocarbons selectivity and conversion of reaction intermediates. The comprehensive investigation has been performed on effects of reaction parameters and optimization condition using Response Surface Methodology. The experimental runs were carried out over four operating parameters i.e. temperature (300-400 °C), pressure (30–80 bar), weight hourly space velocity (WHSV) (1-3 h−1) and H2: oil ratio (400–1000 N cm3/cm3). The reaction intermediates were investigated over optimized reaction parameters for 5 h time on stream. The current study revealed that triglycerides are completely converted into diesel range hydrocarbons to produce hydrodeoxygenation (HDO) selectivity (C16 + C18) of (19.1 wt%) and decarboxylation (DCOx) selectivity (C16 + C18) of (81.7 wt%) under optimized reaction condition at the temperature of 400 °C, pressure 80 bar, WHSV = 1 h−1, and H2: oil ratio 400 N(cm3/cm3). Among all the variables temperature and weight hourly space velocity have significantly influenced the hydrodeoxygenation selectivity. In contrast, where the increase in temperature and pressure dropped the decarboxylation selectivity. H2: oil ratio was observed with significant effect on conversion of transition state of intermediates to stable state of intermediates at optimized condition. The ANOVA analyses demonstrated that HDO selectivity competitively followed on respective reaction condition.

The catalytic and non-catalytic pyrolytic conversion kinetics of palm kernel shell (PKS) with untreated (as received) and H2SO4-treated coal bottom ash as catalyst were investigated in this study. Flynn-Wall-Ozawa (FWO) and distributed activation energy model (DAEM) isoconversional kinetic models were exploited to evaluate the kinetic parameters. The study was conducted using thermogravimetric analysis at 10, 20, 30, and 50 °C/min heating rates. The activation energy (Ea) and pre-exponential factor (A) for non-catalytic PKS decomposition for DAEM ranged from 74.39 to 217.05 kJ/mol and 4.77E+01 to 1.99E+14 s−1 at different conversions while for the untreated ash, the ranges were 103.84–402.53 kJ/mol and 7.35E+03–1.04E+29 s−1. In the decomposition with treated ash, Ea and A were 81.79–191.07 kJ/mol and 1.61E+02–1.20E+12 s−1 for 7 wt% ash and 74.41–137.35 kJ/mol and 4.91E+03–4.53E+08 s−1. Values of Ea and A obtained for FWO followed the same pattern and are in close agreement with that obtained using DAEM. The use of 10 wt% acid-treated ash reduced the activation energy compared with the non-catalytic process by about 33.05% while the untreated ash increased the activation energy. The kinetic parameters were determined satisfactorily using the first-order reaction mechanism.

Hydrodeoxygenation (HDO) is considered as a substantial path for cleaner production of fatty acids and triglycerides into diesel range hydrocarbons (DRHs) (C15–C18) generally identified as green diesel fuel. Heterogeneous catalysis suggests a supplementary approach for the conversion of biomass into significant biochemicals possibly selective hydrocarbons by an inventive method. The present study reveals the optimization of reaction parameters for the process of HDO of rubber seed oil (RSO) over the transition metal NiMo/γ-Al₂O₃ (NMA) catalyst (designed via sonochemical co-impregnation approach) into DRHs, that is, n-C15-n-C18. The comprehensive studies have been performed to investigate the parametric effects employing response surface methodology using central composite design. The experimental design was conducted on the four most influential operating factors, namely, temperature within the range of 300–400 °C, weight hourly space velocity (WHSV) (1–3 h–¹), H₂/oil ratio (400–1000 N (cm³/cm³)), and pressure (30–80 bar), for triglyceride conversion and DRH yield. All the experimental runs were performed in continuous process using a fixed bed tubular reactor over the NMA catalyst. The product analysis showed that triglycerides are completely hydrodeoxygenated into DRHs with an optimum production of 84.94 wt % yield led by prime reaction conditions at a temperature of 400 °C, WHSV of 1 h–¹, pressure of 80 bar, and H₂/oil ratio of 400 N (cm³/cm³). The parametric interaction between temperature and WHSV has significantly influenced the diesel yield. The investigations validated that HDO tracked the corresponding reaction condition in competitive mode and obligated the diverse optimum and limiting reaction conditions. In addition, deactivation of the catalyst study was performed at the optimized reaction condition. The catalyst was found to be active until 18 h without bringing to sulfidization process with 80% diesel yield and 100% triglyceride conversion. The slight deactivation of the catalyst is observed, with a very small amount coke deposition even after 18 h of time on stream at the optimized reaction condition. The novelty of the present study lies in the performance of sonochemically synthesized catalyst for HDO of RSO to produce green diesel and to optimize the reaction condition and catalysts deactivation performance at optimized reaction conditions.

The air gasification of palm waste specifically palm kernel shell has been performed in the fixed bed gasifier using coal bottom ash as a potential catalyst. Effect of the process variables (temperature, catalyst loading, and airflow rate) has been investigated on the product gas composition. The design of experiments was accomplished using the Design Expert v11® with a Central Composite Design approach. Moreover, the parametric study and optimization of the entire process have been carried out using Response Surface Methodology within the specific range of variables. The results suggested that the temperature has been found as the most influencing parameter for increment of H2 and CO production. Whereas, airflow rate was more sensitive for CH4 and CO2 production. Catalyst loading was found very effective for the amplified amount of H2 and CO production and the reduction in the amounts of CO2 and CH4, caused by the catalytic activity of coal bottom ash (CBA). Optimized parameters are found to be the temperature of 850 °C, catalyst loading of 14.50 wt%, and airflow rate of 2.50 L/min, which predicted the composition for H2 of 31.38 vol%, CO of 26.44 vol%, CH4 of 15.67 vol%, and CO2 of 25.59 vol%.

Biodiesel derived from palm fatty acid distillate (PFAD) was produced via catalytic esterification using sulfonated tin oxide (HSO3−/SnO2) as the superacid solid catalyst. In this work, the SnO2 catalyst was synthesised by the self-propagating combustion (SPC) method, and activated using chlorosulfonic acid. The SPC method was able to produce nano-sized particles with homogenous size and shape that were anchored with many HSO3− ions, resulting in more exceptional acid properties that effectively esterified the PFAD feedstock into FAMEs (fatty acid methyl esters). Several studies based on metal oxide-based catalysts were also included for comparison. Under the optimised conditions of 9 : 1 (methanol-to-PFAD molar ratio), 4 wt% (catalyst loading), 100 °C (reaction temperature) and 3 h (reaction time), the FFA conversion and FAME yield were 98.9% and 93.8%, respectively. Besides, the sulfonated SnO2-spc catalyst can be reused in up to five consecutive cycles with an acceptable esterification performance and minimal sulfur leaching. It is worth mentioning that the SPC method is a greener and simpler technique to obtain the nanocatalysts. Overall, the production of FAME from low value, cheaper, abundant, and non-edible PFAD feedstock, assisted by a non-transition metal oxide of sulfonated SnO2 catalyst, could reduce the cost of biodiesel production.