Engineering Headway Vol. 38

Abstract: The co-pyrolysis of biomass and plastic waste offers a promising pathway for renewable fuel production and sustainable waste management. In this study, the co-pyrolysis of empty fruit bunches (EFB) and polypropylene (PP) was investigated to evaluate the influence of temperature and blending ratio on product distribution. Experiments were conducted in a semi-batch reactor at temperatures ranging from 400 to 600 °C with a fixed 50:50 blending ratio, and at 500 °C with varying ratios of EFB:PP (75:25, 50:50, 25:75). The results demonstrated that temperature strongly influenced product yields, with bio-oil production reaching its maximum at 500–550 °C. However, 500 °C was identified as the most favorable condition, providing high bio-oil yield more than 45% while minimizing secondary cracking and excessive gas formation. The blending ratio also played a significant role, with the 50:50 mixture producing the highest liquid yield (46.54%) due to synergistic interactions between hydrogen-rich PP and oxygen-rich EFB, which enhanced radical stabilization and suppressed char formation. At higher PP proportions, gas yields increased substantially, whereas pure PP produced high bio-oil (52.7%) with minimal char but elevated gas fractions. A comparative analysis with literature confirmed the strong influence of feedstock composition, reactor configuration, and operating conditions on product selectivity. Overall, the findings highlight that co-pyrolysis of EFB and PP at 500 °C and a 50:50 blending ratio provides an optimum balance for maximizing bio-oil production, offering a viable strategy for integrating biomass and plastic waste valorization into renewable energy pathways.

Abstract: The increasing energy demand and environmental challenges associated with fossil fuel use highlight the need for renewable alternatives, with algal biomass offering promise due to its abundance, rapid growth, and carbon-neutral profile. While catalytic pyrolysis using ZSM-5 has shown potential in enhancing biofuel yield and quality, studies integrating process optimization for algae waste remain scarce. This research addresses this gap by investigating the catalytic pyrolysis of algae waste and optimizing operational parameters using Response Surface Methodology (RSM). It was hypothesized that optimizing reaction temperature and catalyst loading would significantly improve product selectivity and yield. Experimental runs were designed using a central composite design (CCD), where algae waste was pyrolyzed at 400–600 °C with 4–6 wt% ZSM-5 catalyst. Product yields were quantified and analyzed through GC/MS, and statistical modeling was applied to evaluate parameter interactions. The results revealed that temperature and catalyst concentration strongly influenced product distribution, with bio-oil yields peaking at 15.77% around 475 °C and 5 wt% catalyst, while biochar and gas yields reached 32.39% and 55.89% under optimized conditions. The predictive models showed strong reliability (R² > 0.9), confirming their suitability for guiding process optimization. These findings demonstrate the feasibility of converting algae waste into valuable fuels and materials through catalytic pyrolysis, offering insights for scaling up algae-based biofuel technologies and contributing to sustainable energy development.

Abstract: The increasing demand for clean and sustainable solid fuels has drawn attention to biomass briquettes as an alternative energy source. This study investigates the synergistic effect of mineral–organic interaction on the thermal stability and combustion characteristics of Meranti wood briquettes. Four briquette formulations were prepared: control (Meranti wood + 10% starch binder), and samples with additional eggshell powder at 0.5% and 1%, as well as limestone at 1%. Proximate analysis, calorific value measurement, and thermal analysis (TGA–DTA) were conducted to evaluate fuel properties. The results revealed that the addition of eggshell significantly reduced volatile matter (from 34.37% in the control to 27.06% at 1% addition), increased fixed carbon (up to 61.92%), and moderately raised ash content. Thermal analysis indicated a remarkable shift in decomposition onset from ~349 °C (control) to ~452 °C (+1% eggshell), suggesting improved char stability and delayed volatile release. In contrast, limestone addition drastically increased ash content (28.6%) and decreased calorific value (3956 cal/g), indicating poor suitability. The findings confirm that small additions of eggshell act as a mineral stabilizer, enhancing thermal stability and reducing soot formation while maintaining acceptable energy density. The synergistic role of calcium-rich additives and organic binder presents a promising approach to improving the combustion quality of biomass briquettes.

Abstract: This study aims to enhance hydrogen-rich syngas production through the development of a Ni-Fe/zeolite catalyst derived from natural zeolite obtained in Bayah, Banten Province. Natural zeolite was selected due to its abundance, availability, and favorable physicochemical properties, including high surface area and Brønsted acidity, which make it an effective catalyst support. Nickel (Ni) was employed for its ability to cleave hydrocarbon bonds and decompose tar, while iron (Fe), which is inexpensive and abundant, was utilized for its role in facilitating water-gas shift reactions. The interaction between Ni and Fe as bimetallic catalysts offers a promising area for improving gasification performance. The novelty of this research lies in investigating the synergistic effects between the Ni-Fe/ZA catalyst and the thermal degradation behavior of rice husk biomass, a feedstock widely available in Indonesia with high cellulose and hemicellulose content, low lignin, and favorable porosity. The experimental procedure consisted of catalyst preparation, raw material and catalyst characterization using proximate and ultimate analyses, BET, XRD, SEM-EDS, FTIR, and GC-MS. Results showed that acid-modified zeolite impregnated with Ni and Fe enhanced hydrogen-rich syngas yield while reducing tar and char formation during the gasification process, demonstrating the potential of rice husk as a sustainable feedstock for biomass gasification.

Abstract: This study investigates the thermal distribution characteristics during the pyrolysis of mahogany wood biomass in conjunction with a zeolite catalyst, utilizing a packed bed reactor modelled through ANSYS thermal transient software. The simulations were conducted at various temperatures, specifically 523 K, 623 K, and 823 K, with a consistent heating rate of 800 K/hour over 120 minutes. Our findings reveal that zeolite significantly outperforms mahogany wood in thermal efficiency, demonstrating faster, more uniform, and stable heating across the reactor volume. In contrast, mahogany biomass experiences delays in reaching optimal temperatures, particularly at lower settings. The disparity in thermal performance between the two materials becomes more pronounced with increasing temperatures. These results underscore the effectiveness of zeolite catalysts in not only expediting the attainment of pyrolysis temperatures but also improving heating efficiency and uniformity. This study positions zeolite as a promising catalyst for enhancing the performance and sustainability of biomass pyrolysis reactors, offering valuable insights for optimizing industrial applications.

Abstract: Eucalyptus oil is a type of essential oil primarily composed of 1,8-cineole, which influences its quality and commercial significance. Examining how the source of the eucalyptus leaf raw material affects the yield and chemical properties of eucalyptus oil extracted by the hydrodistillation process is the goal of this study. Eight settlements with different soil types and elevations on Buru Island in Maluku Province provided eucalyptus leaves for collection. All samples were extracted using the hydrodistillation method under consistent operating conditions. Gas chromatography-mass spectrometry (GC-MS) was used to identify the oil's chemical composition, and total yield and recovery were used to analyze oil yield. Based on observations of the extracted oil's visual properties, the 1,8-cineole content was determined to be the primary eucalyptus oil quality measure. The study's findings demonstrate that, while using the same extraction technique, local leaf sources differ in terms of eucalyptus oil output and quality. 1,8-cineole was the predominant constituent in the entire oil sample, with changes in content between locations suggesting possible variances in quality. A few samples had 1,8-cineole level that was within or near the Indonesian National Standard's (SNI) acceptable quality range. This discovery directly affects conventional and small-scale eucalyptus oil production and demonstrates that the source of raw materials has a significant role in determining the quality of eucalyptus oil.

Abstract: Fuel characteristics are the most important thing in the combustion process. Fuel characteristics are influenced by the composition of the mixture, the molecular structure of the mixture formed, the calorific value and the evaporation temperature of the fuel. The purpose of this study was to determine the characteristics of isooctane fuel after being mixed with n-heptane and eugenol additives. This study was conducted by mixing isooctane fuel with n-heptane, at a composition of 92%v Isooctane and 8%v n-Heptane. The mixture was added with eugenol additives. Analysis tests were carried out on the molecular structure, calorific value, evaporation rate, octane number. Experimental tests were carried out to test the combustion rate. The test results were analyzed on the molecular structure. The test results showed that there was no interaction between isooctane, n-heptane and eugenol molecules. Based on these results, it was concluded that eugenol was able to increase the calorific value of isooctane-based fuel at a mixture composition of 1%v eugenol.

Abstract: The increasing worldwide demand for energy is driving the search for less harmful alternatives to fossil fuels. In Indonesia, the plentiful palm oil resources position fatty acid methyl ester generated from crude palm oil (CPO-FAME) as a viable low-carbon alternative to traditional diesel. Due to the crucial influence of microscale combustion phenomena on ignition behavior and burn stability, it is imperative to undertake controlled single-droplet tests to isolate the impacts of fuel additives. This study investigates the efficacy of d-limonene as a bioadditive to improve the performance of CPO-FAME. Seven fuel mixes, containing d-limonene at concentrations from 0 to 20% v/v, were examined using a stabilized single-droplet combustion apparatus. The maximum temperature of the flame, ignition delay (ID), burning time (BT), droplet lifetime (DL), and the burning-rate constant (Kc) were determined by utilizing high-speed imaging at 50 frames per second and a thermocouple type K connected to a data logger. Non-linear responses were seen in the results: the ID was shortest at 5% (4.75 s vs 5.25 s baseline), and the flame temperature increased from 513°C (0%) to 602°C (10% v/v). DL increased from 16.25 s (0%) to 19.5 s (20%), and BT dropped to 8.25 s at 3% before increasing at deeper concentrations. At 5%, Kc peaked at 0.17 s^-1, plateaued at 10–15%, and then climbed to 0.19 s^-1 at 20%, but with an unstable flame. Stable flames between 5 and 10% and soot with micro explosions above 15% were verified by visualization. In conclusion, moderate d-limonene loadings lead to improved ignition and flame stability, while large concentrations are detrimental. To improve biodiesel performance, the additive formulation must be managed.

Abstract: The fossil fuels depletion and its environmental impacts encourages the development and utilization of biodiesel as renewable fuels. Optimatization of engine operational parameter is needed to obtained cleaner combustion. This study aims to evaluate the effect of 190, 200, and 210 MPa injection pressure on Common Rail Direct Injection (CRDI) diesel engine performance and exhaust emissions using B50 and B55 fuel mixtures at various engine speed (1500, 2000, 2500, and 3000 rpm). The results showed that injection pressure increase significantly improved engine performance and reduced emissions. Maximum power increased by 12.59% at 210 MPa compared to 190 MPa at 78.4 HP using B50, while torque increased from 177.6 Nm to 204.2 Nm. B55 fuels shows maximum power reaching 88.9 HP and maximum torque of 203.7 Nm at 210 MPa. Exhaust emissions decline as injection pressure increases. B55 fuel opacity emission decreases from 7.5% (190 MPa) to 6.3% (210 MPa), B50 also shows similar behaviour. This study reveals that injection pressure increase gives better performance and reduced emissions in diesel engines fueled by palm oil biodiesel blends.