Automotive Experiences

Effectiveness of HNO3 and NaOH Pretreatment on Lignin Degradation in Areca Leaf Sheath Fibre (Areca catechu L.) for Bioethanol Production

Wahyuti Wahyuti — 2025-08-15

Areca leaf sheaths are underutilized waste but have a high cellulose content of 72.27%, so they can be utilized for bioethanol production. This research aims to utilize areca leaf waste for bioethanol production through acid (HNO₃ 5%) and alkaline (NaOH 10%) pretreatment processes, enzyme hydrolysis, and fermentation. Pretreatment using 5% HNO₃ and 10% NaOH solutions is carried out because it can break down the lignin bond and release it from cellulose and hemicellulose fibers. The enzymatic hydrolysis process uses cellulase enzymes at 37 °C for 48 hours to produce glucose. Glucose content analysis uses the DNS method and UV-Vis spectrophotometry instruments because it is accurate and can detect glucose in low concentrations. The fermentation process is carried out using Saccharomyces cerevisiae as a fermentation microorganism because it has high efficiency in bioethanol production for a duration of 3, 5, and 7 days. Based on the results of the analysis, pretreatment with HNO₃ 5% solution reduced the level of lignin in areca leaf sheaths by 2.31%. Meanwhile, pretreatment using a 10% NaOH solution lowered lignin levels to 1.81%. Reduced sugar levels after hydrolysis after pretreatment with HNO₃ 5% and NaOH 10% were 25.08 mg/mL and 16.37 mg/mL, respectively. The highest concentration of bioethanol in the 5% HNO₃ pretreatment was achieved on the 7th day at 16.75%, while that of 10% NaOH on the 5th day was 14.75%. This difference is influenced by the availability of fermentable sugars, where HNO₃ substrates take longer to decompose by S. cerevisiae than NaOH substrates. Based on the analysis, the bioethanol contains ethanol, thus the areca leaf sheath fibre feedstock has the potential to assist in the advancement of a sustainable biorefinery process that can reduce dependence on fossil fuels and increase added value.

Catalyst-Free Pyrolysis of Mixed Tyres and Plastic Waste for Heavy Fuel-Oil Production with Distillation

Janter Pangaduan Simanjuntak — 2025-08-27

Waste from used tires and plastics poses a significant environmental challenge due to their non-biodegradable nature. These materials take hundreds to thousands of years to decompose naturally. Every year, plastic and tire waste increase in correlation with population growth and vehicle usage. This waste management is frequently insufficient, resulting in significant adverse effects on human society. One of the effective solutions to the environmental challenges posed by used tires and plastic waste is converting them into crude oil and solid char using pyrolysis technology without a catalyst. This process is a thermochemical decomposition that occurs at high temperatures without oxygen. Pyrolysis breaks down the complex chemical structure of plastics and tires into simpler, valuable components. After being cut into small pieces of 3 cm to 5 cm, the feedstock was placed into a pyrolyzer, with each batch weighing 500 grams, to produce pyrolytic liquid oil and char. The pyrolysis temperature was set at 350 ℃ for all experiments, with a heating rate of 10 ℃/min and a holding time of 90 minutes. The process was followed by distillation at two different temperatures, 250 ℃ and 350 ℃, with a heating rate of 10 ℃/min. This distillation process separated the pyrolytic oil based on its boiling points to obtain distillate liquid oil. Two types of distillate liquid oil were produced and analyzed using gas chromatography and mass spectrometry to determine their chemical composition and compounds. It was found that both distillate oils contained similar organic compounds, primarily consisting of complex mixtures of C12–C31 hydrocarbons, which are typical of heavy fuel oils. The heating value of both distillate oils was 31.26 MJ/kg. Additionally, the residual char produced during the process had a calorific value of 21.73 MJ/kg, indicating its potential use as a solid fuel. These properties demonstrate the potential of the products to substitute conventional fuels for heavy machinery or industrial boilers. This study confirms that used tires and plastic waste can be converted into heavy fuel oils, offering great potential as alternative energy sources.

Optimised Flywheel-Assisted Regenerative Braking for Enhanced Energy Recovery and Voltage Stability in Electric Vehicles

Jafar Masri — 2025-08-27

This study presents a flywheel-assisted regenerative braking system (FARBS) designed to improve energy recovery and voltage stability in electric vehicles (EVs). Conventional regenerative braking systems (RBS) suffer from short energy retention durations and voltage fluctuations, limiting their efficiency. The proposed system incorporates a spherical shell flywheel (120 mm radius, 20 mm thickness, 3 kg mass) directly into the braking mechanism to prolong energy recovery and optimise braking efficiency. Experimental results demonstrate a 439% increase in energy recovery duration, extending from 1.15 seconds (2000 RPM) to 6.2 seconds (4500 RPM). Voltage retention improves significantly, increasing from 10.3V to 19.2V, ensuring sustained voltage delivery. Kinetic energy storage attains 580 J at 4500 RPM, exhibiting a 23.4% increase over 2000 RPM. The flywheel system quadruples power output longevity, sustaining 6.40 W for 6.2 seconds at 4500 RPM, compared to 2.2 seconds without the flywheel. Energy recovery efficiency peaks at 16 J at 4500 RPM, an improvement of 275% in comparison to the baseline 4 J. Optimisation analysis confirms that increasing flywheel mass (1 kg to 3 kg) improves energy recovery by 194%, while a spherical shell flywheel improves energy recovery, achieving 327 J. This is twice as much as that of a solid disk (162 J). Carbon fibre outperforms steel, boosting energy recovery by 94%, while increasing the thickness from 10 mm to 20 mm, and resulting in a 200% efficiency gain. These findings underline the superiority of flywheel-assisted energy recovery, paving the way for high-efficiency braking solutions in EVs, public transportation and railway networks.

Plasma Enhanced Ionic Liquid Catalysis for the Production of Biodiesel from Chicken Skin

Yasir Ali Elsheikh — 2025-08-28

Biodiesel production has emerged as a promising area of alternative fuel development, though challenges remain in sourcing cost-effective raw materials and selecting effective catalysts. This study investigates the production of biodiesel from chicken skin fat using two distinct catalytic methods. In the first method, transesterification was catalyzed by trioctyl ammonium hydrogen sulfate (Oct3AMHSO4) at concentrations ranging from 3-6 wt%. In the second method, the same catalyst was combined with plasma to enhance the reaction. The first method yielded only 35% biodiesel with 3.5 wt% Oct3AMHSO4, while the second method, under identical conditions, showed a significant improvement, achieving a 97.4% yield. The impact of temperature variations (40-80°C) was also explored with different catalyst concentrations (3-6 wt%). Increasing the catalyst concentration to 3.5% and raising the temperature to 55°C resulted in a notable yield improvement. However, further increases in temperature or catalyst concentration beyond 3.5% led to a decline in yield, particularly at temperatures exceeding 60°C. This suggests that certain reaction conditions may reverse the transesterification process, pushing the products back toward the reactants and reducing efficiency.