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Alternative fuel recovery from used engine lubricant (UEL) and empty fruit bunch (EFB) was achieved through microwave co-pyrolysis. Co-pyrolysis was chosen for its potential to improve the quality of pyrolytic oil by generating synergistic effects between two distinct feedstocks, reducing activation energy, and enhancing pyrolytic oil quality. The central composite design (CCD) of response surface methodology (RSM) was used to optimise the temperature and EFB ratio. Atomic absorption spectrometry (AAS) was employed to characterise the heavy metal concentration in the pyrolytic oil. The optimised pyrolytic oil (UE450) produced the highest oil yield (25.17 wt%) with the lowest metal concentration at 450 °C with a 50 % EFB ratio. The fuel’s characteristics were similar to those of conventional diesel, with a higher value of HHV (45.17 MJ/kg). However, the oil was slightly acidic, with a pH of 4.3. GC–MS analysis of UE450 revealed the presence of alkanes and monoaromatic-rich hydrocarbons. Additionally, the UE450 biochar was characterised using FTIR, FESEM, and XRF. FTIR analysis showed that the carbonyl group (C = O) peaks at 1730 and 1440 cm−1 disappeared, indicating that heavy metals were bound to the biochar surface. Likewise, XRF analysis of UE450 biochar revealed that zinc (Zn) exhibited a high metal adsorption capacity, following the sequence Zn > Fe > Pb (1.96, 1.06, and 0.81 mmol/g). The XRF results also indicated a significant removal of SO3 at approximately 10.37 mmol/g.

Commercialised biodiesel, comprising of methyl esters, have large amounts of oxygenated compounds which cause low calorific value, high viscosity, poor low temperature performance and can only used in blends with petroleum-based diesel. Deoxygenation of these compounds can occur through three reaction pathways which are decarboxylation, decarbonylation, hydrodeoxygenation. The removal of oxygen can improve their fuel properties, and is heavily influenced by the presence of hydrogen (H2). However, given safety issues during transportation and storage of H2, the use of solvents to produce in-situ H2 for the deoxygenation process has been suggested as an alternative. The present work attempts to investigate the addition of solvents (deionised water, methanol, ethanol, 1-propanol, 2-propanol, n-hexane and cyclohexane) on the deoxygenation of methyl oleate to enhance its fuel properties. The experiments were carried out with unreduced bimetallic NiCo impregnated onto TiO2. Incorporation of NiCo onto TiO2 maintained the mesoporous nature of the support while increasing the number of strong acid sites of the catalyst, which can promote C-O bond cleavage during deoxygenation. Under hydrogen-restricted conditions, the deoxygenation is expected to occur mainly through decarboxylation and decarbonylation to produce alkanes and alkenes, with cracking to produce shorter chain methyl esters. The deoxygenation was conducted with 50 g methyl oleate, 40 g solvent, 5 wt% catalyst at 300 °C for 2 h in a pressurised nitrogen atmosphere. GCMS analysis show that the addition of 2-propanol showed the highest methyl oleate conversion (69.08 %) over other solvents, with 12.74 % selectivity for alkane formation. These results indicate the potential of solvent-aided deoxygenation of methyl esters for biofuel use.

With the rapid advancement of industrialization, the escalating demand for energy and need for decarbonization prompt for the development of alternative renewable energy sources and highly efficient, clean combustion technologies. Ammonia, being a carbon-free fuel and an excellent hydrogen carrier has gained widespread attention. However, challenges persist in using ammonia as a fuel include high NOx pollutant emissions and the weak reactivity of ammonia. In this study, a swirl experimental platform was employed to investigate the effect of main air preheating on the flame and NOx emissions characteristics of ammonia-methane. Two fuel injection strategies were compared, i.e., dual-fuel injection and premixed injection mode, to form a dual flame and fully premixed swirl flame. The chemiluminescence experiments were performed to analyse the intensities of OH* emissions from flame. Numerical simulations were carried out using the chemical reaction network model. Results shows that both type of flames exhibit different flame structure, with dual flame exhibit higher OH* chemiluminescence intensities. Comparing fully premixed combustion with dual flame combustion modes at T = 473 K and ? = 0.6, the latter shows an 80 % reduction in NO emissions. For CO emissions, both modes maintain CO emissions within 10 ppm/kW, indicating high combustion efficiency. The simulation result shows that a significant increase in the percentage of NNH generated through the reaction of NO and NH2 in the NO reduction process within the dual flame, leading to a notable reduction in NOx emissions. In addition, a fraction of NH2 undergoes thermal decomposition, resulting in the formation of NH, but a portion of this process diminishes as the preheated air temperature rises.

Utilising non-hydrogen environments to convert fatty acids to liquid fuels is potentially an economical, green and promising method for sustainable fuel production. This work focuses on solvent-free biojet fuel generation (C8 to C16) from the trimethylolpropane oleate (TMPE) using transition metal-loaded TiO2 as a solid acid catalyst. Wet impregnation was implemented to produce a series of TiO2-based cobalt, nickel, and iron catalysts with 2 wt.% metal loading without reduction. Each catalyst was tested for the deoxygenation of TMPE at 350 °C for 2 h at atmospheric pressure in a N2 atmosphere. It was found that using transition metal catalysts without reduction in a non-hydrogen environment could generate hydrocarbons with carbon chain lengths within the jet fuel range. The abundance of acid sites on the Fe catalyst helps break C-O bonds and facilitate the deoxygenation process. Fe/TiO2 exhibited the highest selectivity for C8 to C16 hydrocarbons (53.7 %) with relatively good deoxygenation performance (74.2 %). Although impregnation of transition metals resulted in reduction of specific surface area, the additional active sites were able to promote deoxygenation and breaking bond reactions to occur. The acidic sites provided by Fe metal and TiO2 carriers indicate that the catalyst is suitable for atmospheric nitrogen deoxygenation of TMPE for the preparation of biojet fuel. The result shows the potential of using a non-hydrogen environment to perform deoxygenation on long-chain fatty acid molecules to derive jet-fuel range hydrocarbons.

The potential of coffee waste to be valorised into useful bioenergy is investigated using a continuous microwave pyrolysis rig. Coffee waste of Arabica species was ground and pretreated prior to pyrolysis at elevated temperature under CO2 atmosphere. Valorisation of the coffee waste result in char, liquid, and gaseous products. Analysis shows that biochar yield is highest at 450 °C, while bio-oil recovery peaks at 550 °C. Gaseous product results in highest yield at 650 °C. Energy analysis indicates that biochar contains the highest energy density, while bio-oil's energy density decreased with temperature due to cracking of volatiles. Energy profitability was shown to be negative across all temperatures, with highest deficit at 450 °C due to the formation of non-recoverable products such as water. Higher energy profitability was achieved at 650 °C as more volatiles could be recovered in gaseous form. The study shows that microwave pyrolysis is effective in valorising coffee waste and essential to enhance the energy recovery from coffee waste.

Ammonia stands out as a promising zero-carbon fuel and an efficient hydrogen carrier, offering great promise for industrial applications in gas turbines and boilers. However, different combustion modes significantly influence the flame structure and combustion characteristics of ammonia. In this study, two distinct fuel injection strategies were employed in a model combustor: ammonia and methane, under fully premixed and dual-flame combustion modes. Numerical simulations were performed to analyze the flame structure, velocity fields, and temperature distribution, complemented by planar flow field, flame OH* chemiluminescence, and NO emission measurements. Findings reveal that with an increasing NH3 ratio, the flame front becomes more elongated with more pronounced temperature fluctuations at the swirler exit. Particularly, at 50% NH3, a significant reduction in flame temperature is observed, notably at a height of 30 mm from the burner. For dual flames, the reaction NH2 + O ↔ HNO + H was less significant compared to its effect in premixed flames, whereas the H + O2 ↔ O + OH reaction demonstrated the highest sensitivity coefficient. An increase in the NH3 ratio correspondingly led to a reduction in NO consumption reaction rates, heightening the sensitivity coefficient for NO inhibition, and providing critical insights into ammonia combustion optimization.

Abstract Renewable jet fuel (RJF) is often touted as the only viable sustainable energy source for the aviation sector, given the difficulties faced by other low-carbon energy sources in overcoming technological barriers. Despite that, the sustainability of RJF is still in dispute due to the conflicting requirements in natural resource for producing the fuels. We introduce a holistic 25-indicator sustainability index encompassing the four domains of energy-water-food nexus and governance, that measures the potential impact of RJF production on 154 countries (and territories) through the oil-to-jet, alcohol-to-jet and gas-to-jet conversion methods. Countries and territories are ranked according to the composite index scores of the four domains. The sustainability index model provides insights on how RJF affords the aviation sector a clean slate in determining the manner of development in a sustainably and equitable way, while also marching towards the long-term goal of carbon neutrality, in alignment with the Sustainable Development Goals.

The conversion of waste cooking oil (WCO) into renewable fuels has been proposed as a waste utilisation method which can ease global energy demand. The deoxygenation of WCO into fuel range hydrocarbons avoids the use of expensive hydrogen but comes at the cost of poor fuel properties and elevated reaction conditions. The use of bimetallic catalysts for the deoxygenation can improve catalyst performance and selectivity for alkane and alkene chains. The present work attempts to utilise the synergistic combination of nickel and cobalt catalysts to produce fuel with suitable carbon chain hydrocarbon composition. The experiments were carried out with monometallic Ni, Co and bimetallic NiCo all impregnated onto TiO2 without reduction. The deoxygenation parameters were set at 100 g feedstock, 5 wt% catalyst, 250 mL/min nitrogen flow at 100 rpm rotation for 2 h under atmospheric pressure. NiO catalyst showed the highest deoxygenation conversion, obtaining 89.03 % of deoxygenated product after reaction. Although Co3O4 catalyst showed relatively lower deoxygenation activity (52.01 %), the higher selectivity towards C10-C16 hydrocarbons highlighted its potential to be used as catalyst promoter. The use of bimetallic NiCo catalysts in a nitrogen atmosphere was found to be capable of producing hydrocarbons within a suitable carbon chain length for jet fuel use. Overall, the sequential impregnated NiCo is identified as the optimum catalyst as it showed good deoxygenation activity (78.78 %) with the highest selectivity towards C10-C16 hydrocarbons. The outcome of this study provides scientific insights on the deoxygenation of fuel range hydrocarbons under atmospheric pressure without the use of hydrogen.

The depletion of fossil fuels, harmful emissions from their combustion, and the 2022 global energy shock due to geopolitical instabilities have led to the surge in renewable energy development. Within the context of the transportation sector, biodiesel is a sustainable and green source of liquid biofuel that can replace petroleum diesel and simultaneously be part of a solution to the aforementioned global problems. Conventional biodiesel production suffers from poor mass transfer, which leads to slow reaction kinetics, lengthy reaction time and inefficient heating of reaction. This study aims to enhance the mass transfer of biodiesel production through microwave heating in combination with a mesochannel reactor, fabricated using polyethylene terephthalate glycol (PETG). A full factorial experimental study was investigated using palm oil with sodium hydroxide as catalyst, incorporating test parameters of methanol to oil molar ratio (3:1, 6:1, 9:1), catalyst loading (0.6, 0.8, 1.0 wt%) and reaction temperature (50, 60, 70 °C). Biodiesel samples were characterised using gas chromatography to quantify the biodiesel yield. The highest biodiesel yield of 78.0 % was achieved in under 1 minute at a methanol to oil molar ratio, reaction temperature and catalyst loading of 3:1, 70 °C and 1.0 wt%, respectively. It is postulated that greater yield could be achieved by lengthening the reactor channels. Overall, the use of PETG mesochannel reactor in combination with microwave-assisted heating has the prospect of facilitating rapid biodiesel production with enhanced mass transfer between reactants.

Biodiesel is an important renewable fuel derived from bioresources that can help to mitigate climate change by significantly reducing carbon emissions from the transportation sector. The conventional batch reactor transesterification process to produce biodiesel is inefficient due to long production time and high energy consumption. In this study, transesterification of palm oil for biodiesel production is conducted using the combined technologies of tubular reactor and microwave-assisted heating method. Parameters investigated include the effects of microwave power, methanol to oil molar ratio, KOH catalyst concentration, and tube length, on FAME yield. Fatty acid methyl ester (FAME) yield of 96.5 % meeting the EN 14214 standard were obtained within the conditions where methanol to oil molar ratio was 8.5-10.0 and microwave power was.320 to 350 W. It was observed that FAME yield reduces when excess microwave power is provided to the reaction due to overheating of organic molecules and boiling of methanol. An average increase of around 10 % in FAME yield was found when the KOH catalyst concentration increases from 0.8 to 1.2 wt%. The results of this study provide insights into the optimisation of transesterification process for producing biodiesel using the combined microwave-assisted heating in tubular reactor method.

Biodiesel stands at the forefront as a replacement for fossil diesel in compression ignition engines, particularly in the transportation sector where diesel engines are the primary movers. However, biodiesel production is hampered by poor heat and mass transfer during the transesterification reaction, leading to long production times and high costs due to inefficient energy utilisation. This study targets heat and mass transfer issues during the production of biodiesel via a synergic approach that combines microwave-assisted heating and microfluidics via a polyethylene terephthalate glycol (PETG) microchannel reactor. The transesterification reaction of palm oil and methanol was investigated using a full factorial design of experiments (DOE) method. Biodiesel yield was quantified via gas chromatographic analysis, and the results were optimised using statistical analysis. Optical analysis of slug quantification within the microchannel revealed that small slugs, smaller than 1 mm, accelerated the transesterification reaction. The composite-optimised experimental results, aimed at minimising energy costs and environmental impacts while maximising fatty acid methyl ester (FAME) yield, indicate a reaction temperature of 50 °C, a catalyst loading of 1.0 wt.%, and a 3:1 methanol to oil molar ratio. Regression analysis revealed that the reaction temperature was statistically insignificant when utilising the PETG microchannel reactor. This key finding positively impacts biodiesel production as it relates to significantly reduced energy intensity, costs, and emissions. Overall, this research work paves a pathway toward an energy-efficient and sub-minute rapid transesterification reaction, highlighting the effectiveness of microwave heat delivery and effects of microfluidics via the PETG microchannel reactor in overcoming heat and mass transfer barriers in biodiesel production.

The depletion of fossil fuels, along with the environmental damages brought by their usage, calls for the development of a clean, sustainable and renewable source of energy. Biofuel, predominantly liquid biofuel such as biodiesel, is a promising alternative to fossil fuels, due to its compatible direct usage within the context of compression ignition engines. However, the industrial production of biodiesel is far from being energy and time efficient, which contributes to its high production cost. These inefficiencies are attributed to poor heat and mass transfer of the transesterification reaction. The utilisation of microchannel reactors is found to be excellent in escalating heat and mass transfer of the reactants, benefitting from their high surface area-to-volume ratio. The microchannel also intensifies the mixing of reactants via the reactor design, micromixers and the slug flow patterns within the reactor, thus enhancing the contact between reactants. Simulation studies have aided in the identification of mixing regimes within the microchannel reactors, induced by various reactor designs. In addition, microwave irradiation heating is found to enhance biodiesel production by localised superheating delivered directly to the reactants at a molecular level. This enables the reaction to begin much earlier, resulting in rapid biodiesel production. It is postulated that the synergy between microchannel reactors and microwave heating would catapult a pathway towards rapid and energy-efficient biodiesel production by enhancing heat and mass transfer between reactants.

Approximately 17.9% of fuel energy is used to overcome engine friction in passenger cars with engine frictional losses further broken down into losses along hydrodynamic (40%), elastohydrodynamic – due to pure sliding motion (40%), mixed (10%) and boundary (10%) lubrication regimes. Therefore, to assess the tribological influence of TMP trioleate as an eco-friendly additive to a low viscosity Polyalphaolefin (PAO) at different lubrication regimes, the present study adopted a Stribeck-type analysis. Through this study, the viscosity index of PAO was found to increase significantly when blended with 5-vol% TMP trioleate. Tribologically, across the tested conditions at different sliding velocities and applied normal loads, it was determined that this blend could potentially reduce friction power and wear scar diameter by up to 6.09% and 39.65%, respectively, when compared with the neat PAO. Such an improvement was demonstrated to also synergistically enhance the friction modifier effect of this blend at the mixed lubrication regime, delaying the onset of boundary lubrication regime when the contact is lubricated by this mixture.

The efforts in discovering new, green and sustainable energy sources have been overwhelming, all with the common aim of combating global warming and environmental pollution while protecting the supply security of conventional energy sources. Pyrolysis is a secure thermo-chemical conversion method suitable for the conversion of biomass waste into a product of higher energy value, aimed for energy production. Co-pyrolysis on a blend of feedstock from different sources has captured the attention of the scientific community as it has been demonstrated to be able to overcome undesirable characteristics of the derived products like high acidity and high ash content. The present study demonstrates the co-pyrolysis of empty fruit bunch (EFB) and waste tire (WT) at a mass ratio of 1:1 using a thermogravimetric analyser. The results were compared with the baseline of pure feedstock pyrolysis. It was reported that EFB is more reactive at a lower temperature region (200-325 (C) due to the composition of cellulose and hemicellulose. WT has a higher temperature degradation zone (300-480 (C), correlating with the compositions of natural rubber, styrene-butadiene rubber and butadiene rubber. A synergism analysis by comparison of theoretical and experimental TG and DTG curve of the blend revealed an inhibitive effect on the decomposition rate on the first peak of the DTG graph (~316 (C) while promoting the decomposition rate on the second peak of the DTG graph (~371 (C). The activation energy of the blend (194.98 kJ/mol) is determined to be lower as compared to EFB (257.29 kJ/mol) and WT (252.92 kJ/mol) obtained through Flynn-Wall-Ozawa (FWO) method, which indicates some form of synergism between both feedstock during co-pyrolysis. Thus, the blending of EFB and WT has been proven to attain synergism during pyrolysis. This finding reports a viable pathway for co-processing of biomass waste (EFB) and rubber waste (WT) while potentially able to generate valuable bio-products of alternate use.

Alternative fuels are under scrutiny for mitigating carbon dioxide emissions. One of these alternatives is ammonia, which can be produced from waste sources, renewable energy and even nuclear power with potentially zero carbon emissions over most of its life cycle. The difficulties of pure ammonia combustion, partially due to its low flame speed and flammability, can be addressed by doping ammonia mixtures with hydrogen, which increases the reactivity of these blends and allows combustion features similar to those of some fossil fuels. However, NOx emissions are still a problem when burning ammonia, with some circumstances where emissions are even worse than with fossil-based systems. This is a consequence of the considerable formation of N2O, a greenhouse gas that is known to possess up to 300 times the Global Warming Potential (GWP) of carbon dioxide, making these regimes unsuitable for the purpose of fuel replacement to combat climate change. Therefore, this work shows bespoke results for unburned NH3 and NOx emissions, specifically NO, NO2 and N2O, at various conditions of operation whilst employing ammonia-hydrogen blends in a tangential swirl burner representative of industrial gas turbines. The results show a good compromise of NOx emissions at the near 1.05 - 1.2 equivalence ratio, with further understanding behind the chemistry that precludes the formation/consumption of these unwanted emissions for full deployment of ammonia-based energy systems.

The valorization of chicken manure via pyrolysis can give biowaste a second life to generate value and contribute to the circular economy. In the present study, the thermal degradation and pyrolysis characteristics of chicken manure pyrolysis were investigated via thermogravimetric analyses (TGA) coupled with optimization methods. Thermogravimetric data were obtained for the samples at five heating rates of 5, 10, 20, 30 and 50 °C/min over a range of temperature under inert conditions. The manure devolatilization process was initiated at between 328 and 367 °C to overcome the global activation energy barrier. The determined activation energy of the manure via Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Friedman and Kissinger methods was in the range of 167.5–213.9 kJ/mol. By using the particle swarm optimization (PSO) method, the pyrolytic kinetic parameters of the individual component present in the manure were calculated, in which the activation energy for cellulose (227.8 kJ/mol) was found to be higher than that of hemicellulose (119 kJ/mol) and lignin (134.3 kJ/mol). Based on intrinsic transition-state theory, the pre-exponential factor and activation energy of the manure can be correlated through a linear equation ln Aα = 0.2006 Eα − 1.2847. The devolatilization characteristics of the chicken manure were elucidated via the optimization process, paving the way for the design of thermochemical conversion reactors and processes.

Vegetable-oil-based biolubricants are an excellent alternative to conventional lubricants. Instead of focusing on novel feedstocks, these biolubricants should be further elucidated based on their fatty acid composition, which influences their tribological properties. Therefore, the study utilises gene expression programming (GEP) to derive a boundary lubricity model for vegetable-oil-derived trimethylolpropane (TMP) esters, considering the fatty acid composition (saturation and monounsaturation levels), load and speed. Neat vegetable oil and blends from seven feedstocks are selected following a wide range of fatty acid profiles to synthesise TMP esters using a two-stage transesterification process. The TMP esters are spin-coated on wear discs that are subsequently rotated against a ball using a purpose-built tribometer. The frictional performance of the TMP esters with balanced saturation and monounsaturation levels of fatty acid are measured to improve it at higher speeds. The GEP model is statistically evaluated by adopting the friction data, a showing good generalisation and predictability capability. The model demonstrates that friction decreases with increasing saturation levels of the TMP ester. The GEP model for vegetable oil TMP esters allows for the tribological performance prediction of TMP esters following the fatty acid profile, providing a platform to optimise such biolubricant for desired applications.

In regard to the current state of global energy, the high demand for traditional fossil fuels and their negative environmental impact have led to an increase of interest in the development of renewable clean fuels. Recently, nano-additives such as carbon nanotubes (CNTs) have been considered as a potential additive to increase fuel combustion performance. Thus, we experimentally studied the combustion characteristics of multi-walled carbon nanotubes (MWCNTs) blended palm-oil biodiesel/air mixtures at a wide range of equivalence ratios, 0.7–1.6. Experiments were conducted at atmospheric pressure and a temperature of 550 K to ensure full vaporization of the liquid biodiesel fuel. Concentrations of the MWCNTs in the mixture were varied from 25 to 200 ppm for two different groups of nanotubes having outer diameter ranges of 10–20 nm and 30–50 nm. The results showed that both laminar burning velocity and blowoff velocity were increased with the additions of MWCNTs. Besides, the flammability limits of MWCNTs blended biodiesel/air premixed flames were also extended at both fuel-lean and fuel-rich conditions. It was also observed that the MWCNTs of 10–20 nm experienced more noticeable improvements in the combustion characteristics compared to the MWCNTs of 30–50 nm. After reaching the highest enhancement, a further increase in the concentration of MWCNTs generally caused less improvement in the laminar burning velocities of the premixed flames. Besides, the addition of MWCNTs increased nitrogen oxides and decreased carbon monoxide concentrations in the combustion products.

Ammonia (NH3) has emerged as an attractive carbonless fuel that can be co-fired with hydrocarbon fuel to reduce carbon dioxide emissions. To understand the influence of NH3 on soot formation when co-fired with hydrocarbons, the soot formation propensity is experimentally investigated via a laminar diffusion jet flame. A stable ethylene (C2H4) jet flame doped with NH3 at different volume percentages was established for the investigation of soot formation tendency. OH* chemiluminescence imaging revealed the change of flame structure, in which the signals emitted from the heat release region weakened with increasing NH3 addition, while the peak intensity shifted from the flame wings towards flame centerline region. The laser extinction method used to measure the soot volume fraction (SVF) at different heights above the burner, which showed the effect of NH3 on soot suppression is significant, owing to the interaction between N-containing compounds with carbon atoms that result in the reduction of key intermediate products required for the formation of benzene and polycyclic aromatic hydrocarbons (PAH). The effect of soot inhibition appears to be stronger for the low NH3 blend fraction. The chemistry effect of NH3 on soot reduction for C2H4 flame is ascertained by comparing with N2-doped C2H4 flame at the same volume percentage. This work highlights the need for improved understanding of hydrocarbon fuel with NH3 to enable detailed understanding on the soot generation and oxidation process.

Post-combustion carbon capture (PCC) plays an important role in reducing the greenhouse gas emissions. In the present study, an exergy analysis is conducted to assess the exergy destruction and exergetic efficiency of a natural gas-fired combined cycle gas turbine (CCGT) system coupled with the PCC unit. The overall exergetic performance of the system is compared against the baseline CCGT by using realistic data. The working temperature and composition of the exhaust flue gas are two critical parameters that have significant impact on the performance of the absorption liquid and equipment operation. Results show that the highest exergy destruction occurs in the combustion chamber and condenser are 15.69 MW and 11.78 MW, occupying more than 45 % of the exergy destruction of the overall system for the conventional CCGT system. For the CCGT system with PCC unit, the exergy destruction of absorber is relatively high with an exergetic efficiency of 56.18 %. The highest exergetic efficiency is found in the units of combustion chamber and heat recovery steam generator (HRSG), which are 90.23 % and 87.01 %, while the condenser has the lowest efficiency. Identification of the low efficiency component presents an opportunity for improvement of the system.

Concerns regarding energy security are raised due to the conventional fossil fuel depletion, which drives the need of diversifying fuel sources for power generation. Sewage sludge, which is a waste product from the wastewater treatment plant, contains energy that could be retrieved and reused. Typically, these sludge are treated as a form of schedule waste and disposed of in a landfill. In this work, the valorisation potential of sludge cake to produce higher-value products was studied through thermogravimetric analysis....It has been demonstrated through this study that the sludge cake from food processing industries is a promising feedstock pyrolysis to yield bio-products of higher values.

Transforming waste to energy is essential in view of the need to search for greener and more sustainable energy sources. Such transformation of energy is also aligned with the aim of reducing excessive waste generation whilst creating potential biofuel pathways for power generation. In the present study, animal waste in the form of horse manure is being used as feedstock to undergo microwave-induced pyrolysis via a fixed-bed pyrolysis rig. The relationship of the pyrolysis parameters such as pyrolysis temperature of 350 and 550 ?C, carrier gas flow rate of 0.5 and 1.5 L/min and ratio of horse manure to activated carbon blend of 1:2 and 1:1, with the yield of pyrolysed products is studied. The derived pyrolysis products in the form of solid, liquid and gaseous are characterised and quantified. Result shows that the highest yield of solid, liquid and gaseous products obtained are 78.8 wt%, 24.7 wt% and 34.2 wt%. Solid yield is observed to decrease with increasing pyrolysis temperature while gaseous yield shows a reverse trend. Higher carrier gas flow rate is observed to lower the generation of gaseous and liquid yield while increasing the solid yield. Higher amount of activated carbon within the feedstock is seen to lower the solid yield but increase the gaseous and liquid yields. The liquid yield is found to contain 55.78 wt% of phenolic compounds while gaseous product consists of up to 55 vol% of syngas. The control of the operating conditions in pyrolysis rig enables the production of pyrolysis end products in different phases, generating useful bioenergy and biofertilizer products in the context of circular economy.

Algae is a potential third-generation biofuel sources that can be used to produce high quality liquid fuel. The physio-chemical properties of algae depend on the species type, of which can also vary with climate, geography and environmental conditions. In this study, the pyrolysis behaviour of a brown macroalgae, Sargassum polycystum (SP), obtained along the coast of Desaru, Malaysia is characterised using a thermogravimeter. The thermal decomposition of the selected brown algae was carried out at the heating rate of 5, 10, 20 and 40 °Cmin-1. A model-fitting method, which includes the most common reaction mechanism in solid-state decomposition processes is being used to predict the kinetic parameters for Sargassum polycystum. The results showed that the Sargassum polycystum macroalgae decomposition process follows the third-order of reaction, F3 with a highest correlation value of 0.94, at 15-70 % of conversion level. The average activation energy from all heating rates is found to be 19.09 kJ/mol with a pre-exponential value of 0.537 s-1. An increase in heating rate results in the increase of activation energy and pre-exponential values.

Horse manure contains potential source of bioenergy that can be pyrolysed to obtain bio-oil and synthesis gas. In the present work, horse manure samples collected from the horse stable in Universiti Teknologi Malaysia were analysed through thermogravimetric analysis (TGA) to determine the Arrhenius parameters and thermodynamics properties. TGA was conducted on the horse manure at heating rates of 1, 2, 5, 10 °C/min in a nitrogen-filled reactor. The TGA data was analysed by using three different model-free, non-isothermal methods, namely Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Kissinger methods. Result shows the temperature for highest conversion of horse manure is within the range of 290.2-329.6 K. The Kissinger method shows the overall average activation energy of 148.47 kJ/mol, whereas FWO and KAS methods show the activation energy at different conversional fractions throughout the process with the range of 176.2-293.6 kJ/mol and 175.6-300.1 kJ/mol. Thermodynamic properties including the pre-exponential factor, enthalpy change, free Gibbs energy and entropy of horse manure during pyrolysis were also determined.

Biodiesel is commonly produced via the transesterification process, usually through the use of batch type reactor. There are significant gaps in batch reactor technologies, where the importance of these factors are often concluded based on the steady-state conditions, manifested in the form of the final yield. In this study, a comprehensive test matrix is setup using full factorial design of experiments, consisting of 4 factors and 2 levels. Four parameters of interest such as agitation speed (200-400 rpm), catalyst loading (0.5-1.5 wt%), methanol to oil ratio (3:1-6:1), and temperature (30-60 °C), were investigated to understand the interaction of these independent factors at the different stages of transesterification. To further investigate the effect of each factors on the transient process, one-way effect of these factors on the transient yield is investigated. Through the multi-factor analysis, the transesterification process can be segregated into 5 unique stages, as the standardised effect of these factors responded differently throughout. The results indicate that batch reactor transesterification performs better with low methanol-oil ratio at the beginning phase, and importance of methanol-oil ratio significantly increases over time. The methanol-oil ratio also become the most influential factor when steady-state is achieved, from a standardised effect magnitude of 0.38 to 14.21, representing an over 37-fold improvement. Agitation speed also showed a reduction of 37-fold in standardised effect throughout the transesterification process, where the effect reached plateau around mid-way of the reaction. Catalyst loading and temperature share similar trends, as they both influence the activation energy of transesterification. Although catalyst loading and temperature are highly influential throughout, a 1.88 and 1.78fold decrease in impact are observed. In conclusion, this study provides insights towards developing biodiesel production techniques, through better understanding of the cross-interactions between factors, and in terms of optimising transesterification dynamically.

Crude glycerol, a by-product of biodiesel production created via transesterification was pyrolyzed using a microwave heating technique in an oxygen-deficient environment. Coconut shell-based activated carbon was used as a catalyst to assist in the heat transfer and the cracking of glycerol into gaseous and liquid products. Investigation into the product yield was conducted by varying the pyrolysis temperature between 300°C and 800°C. The result revealed that liquid and gaseous pyrolysis products yield fell in the range of 15?42% and 55?82% by mass, respectively. An analysis of the liquid product using gas chromatography mass spectrometry (GC-MS) shows that glycerin (C3H8O3), methanamine (CH5N), and cyclotrisiloxane (C6H18O3Si3) were among the highest derived compounds in the pyrolyzed liquid yield. The derived pyrolysis products can potentially be used as alternative fuels in combustion systems.

The present study focuses on the characterization of carbon nanotubes (CNTs) synthesized from flame under an atmospheric condition. A laminar flame burner was utilized to establish a rich premixed propane/air flame at the equivalence ratio ? = 1.8–2.2. The flame was impinged on a stainless steel wire mesh coated with nickel (Ni) catalyst to grow CNTs. Distribution and yield of the CNTs on the substrate were quantified. Carbon nanotubes formed on the substrate were harvested and characterized using scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and thermogravimetric analysis (TGA). The FESEM micrograph showed that the CNTs produced were in disarray. The synthesized CNTs were an average of 50–60 nm in diameter while the length of the tubes was in the order of microns. TGA analysis showed that 75% of CNTs were present in the sample and the oxidation temperature was 510°C.

This study investigated the use of microwave pyrolysis as a recovery method for waste shipping oil. The influence of different process temperatures on the yield and composition of the pyrolysis products was investigated. The use of microwave heating provided a fast heating rate (40 °C/min) to heat the waste oil at 600 °C. The waste oil was pyrolyzed and decomposed to form products dominated by pyrolysis oil (up to 66 wt. %) and smaller amounts of pyrolysis gases (24 wt. %) and char residue (10 wt. %). The pyrolysis oil contained light C9–C30 hydrocarbons and was detected to have a calorific value of 47–48 MJ/kg which is close to those traditional liquid fuels derived from fossil fuel. The results show that microwave pyrolysis of waste shipping oil generated an oil product that could be used as a potential fuel.

Commercialised biodiesel, comprising of methyl esters, have large amounts of oxygenated compounds which cause low calorific value, high viscosity, poor low temperature performance and can only used in blends with petroleum-based diesel. Deoxygenation of these compounds can occur through three reaction pathways which are decarboxylation, decarbonylation, hydrodeoxygenation. The removal of oxygen can improve their fuel properties, and is heavily influenced by the presence of hydrogen (H2). However, given safety issues during transportation and storage of H2, the use of solvents to produce in-situ H2 for the deoxygenation process has been suggested as an alternative. The present work attempts to investigate the addition of solvents (deionised water, methanol, ethanol, 1-propanol, 2-propanol, n-hexane and cyclohexane) on the deoxygenation of methyl oleate to enhance its fuel properties. The experiments were carried out with unreduced bimetallic NiCo impregnated onto TiO2. Incorporation of NiCo onto TiO2 maintained the mesoporous nature of the support while increasing the number of strong acid sites of the catalyst, which can promote C-O bond cleavage during deoxygenation. Under hydrogen-restricted conditions, the deoxygenation is expected to occur mainly through decarboxylation and decarbonylation to produce alkanes and alkenes, with cracking to produce shorter chain methyl esters. The deoxygenation was conducted with 50 g methyl oleate, 40 g solvent, 5 wt% catalyst at 300 °C for 2 h in a pressurised nitrogen atmosphere. GCMS analysis show that the addition of 2-propanol showed the highest methyl oleate conversion (69.08 %) over other solvents, with 12.74 % selectivity for alkane formation. These results indicate the potential of solvent-aided deoxygenation of methyl esters for biofuel use. [ABSTRACT FROM AUTHOR]

With the rapid advancement of industrialization, the escalating demand for energy and need for decarbonization prompt for the development of alternative renewable energy sources and highly efficient, clean combustion technologies. Ammonia, being a carbon-free fuel and an excellent hydrogen carrier has gained widespread attention. However, challenges persist in using ammonia as a fuel include high NOx pollutant emissions and the weak reactivity of ammonia. In this study, a swirl experimental platform was employed to investigate the effect of main air preheating on the flame and NOx emissions characteristics of ammonia-methane. Two fuel injection strategies were compared, i.e., dual-fuel injection and premixed injection mode, to form a dual flame and fully premixed swirl flame. The chemiluminescence experiments were performed to analyse the intensities of OH* emissions from flame. Numerical simulations were carried out using the chemical reaction network model. Results shows that both type of flames exhibit different flame structure, with dual flame exhibit higher OH* chemiluminescence intensities. Comparing fully premixed combustion with dual flame combustion modes at T = 473 K and ϕ = 0.6, the latter shows an 80 % reduction in NO emissions. For CO emissions, both modes maintain CO emissions within 10 ppm/kW, indicating high combustion efficiency. The simulation result shows that a significant increase in the percentage of NNH generated through the reaction of NO and NH2 in the NO reduction process within the dual flame, leading to a notable reduction in NOx emissions. In addition, a fraction of NH2 undergoes thermal decomposition, resulting in the formation of NH, but a portion of this process diminishes as the preheated air temperature rises. [ABSTRACT FROM AUTHOR]

The depletion of fossil fuels, harmful emissions from their combustion, and the 2022 global energy shock due to geopolitical instabilities have led to the surge in renewable energy development. Within the context of the transportation sector, biodiesel is a sustainable and green source of liquid biofuel that can replace petroleum diesel and simultaneously be part of a solution to the aforementioned global problems. Conventional biodiesel production suffers from poor mass transfer, which leads to slow reaction kinetics, lengthy reaction time and inefficient heating of reaction. This study aims to enhance the mass transfer of biodiesel production through microwave heating in combination with a mesochannel reactor, fabricated using polyethylene terephthalate glycol (PETG). A full factorial experimental study was investigated using palm oil with sodium hydroxide as catalyst, incorporating test parameters of methanol to oil molar ratio (3:1, 6:1, 9:1), catalyst loading (0.6, 0.8, 1.0 wt%) and reaction temperature (50, 60, 70 °C). Biodiesel samples were characterised using gas chromatography to quantify the biodiesel yield. The highest biodiesel yield of 78.0 % was achieved in under 1 minute at a methanol to oil molar ratio, reaction temperature and catalyst loading of 3:1, 70 °C and 1.0 wt%, respectively. It is postulated that greater yield could be achieved by lengthening the reactor channels. Overall, the use of PETG mesochannel reactor in combination with microwave-assisted heating has the prospect of facilitating rapid biodiesel production with enhanced mass transfer between reactants. [ABSTRACT FROM AUTHOR]