The Journal of Clean Technology (JoCT) is a premier, peer-reviewed, open-access scholarly journal that focuses on the advancement of science, engineering, and policy in the field of clean and sustainable technologies. Established to support global efforts toward environmental sustainability, JoCT provides a dynamic platform for academics, researchers, practitioners, and policymakers to disseminate high-impact research, innovative practices, and transformative ideas that contribute to a cleaner and more sustainable future. JoCT welcomes contributions from a wide range of disciplines—including but not limited to chemical engineering, environmental science, renewable energy, green materials, waste management, circular economy, industrial ecology, sustainable manufacturing, and clean production systems. This multidisciplinary approach reflects the complex, interconnected nature of today’s environmental challenges and promotes collaborative innovation across sectors and regions. As part of its mission to promote equitable access to scientific knowledge, JoCT is fully open-access and does not impose any article processing charges (APCs) or publication fees on authors. All published articles are freely available online to the global research community and the general public, ensuring maximum visibility and impact without financial barriers. This commitment supports the democratization of knowledge and encourages contributions from researchers in both developed and developing countries. JoCT is published both in print and electronically, carrying the registered standard serial numbers p-ISSN 2460-8874 for the printed edition and e-ISSN 2460-9811 for the electronic version. The journal is managed and reviewed by a distinguished international editorial board and adheres to rigorous peer-review standards to ensure the quality, integrity, and originality of every published manuscript. Through its dedication to scientific excellence, environmental responsibility, and open accessibility, The Journal of Clean Technology aims to play a critical role in shaping the future of sustainable technological development and global environmental stewardship.
All articles published in The Journal of Clean Technology (JoCT) are licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). Under this license, readers are free to share, copy, and redistribute the material in any medium or format for non-commercial purposes, provided that the following terms are met: Attribution: Proper credit must be given to the original author(s) and source, including a link to the license and an indication of any changes made (if applicable). NonCommercial: The material may not be used for commercial purposes. NoDerivatives: If the material is remixed, transformed, or built upon, the modified material may not be distributed. The full license terms can be viewed at: https://creativecommons.org/licenses/by-nc-nd/4.0/ Authors retain the copyright of their articles and grant The Journal of Clean Technology the right of first publication with the work simultaneously licensed under this Creative Commons license.
Physicochemical Characterization and Bioactive Compound Profiling of Oil Palm Leaf (Elaeis guineensis Jacq.) Extract for Green Nutraceutical Effervescent Tablets
The valorisation of oil palm leaf (Elaeis guineensis Jacq.) agricultural waste into high-value nutraceutical products embodies circular economy principles within the world's largest palm oil producing nation. Oil palm leaves, currently discarded across 16.83 million hectares of Indonesian plantations, harbour diverse antioxidant, antimicrobial, and anti-inflammatory bioactive compounds. This study presents a comprehensive, multi-technique physicochemical and chemical characterisation of palm leaf ethanol extract and its optimal effervescent tablet formulation (F1, acid:base = 1:1) relevant to clean technology nutraceutical development. The palm leaf extract was characterised by X-Ray Diffraction (XRD) nanostructural analysis using the Debye-Scherrer equation, Fourier Transform Infrared Spectroscopy (FTIR), and Gas Chromatography-Mass Spectrometry (GC-MS). Antioxidant stability was assessed by the DPPH radical scavenging assay over four weeks (n = 3). XRD analysis revealed nanoparticulate crystal sizes of 58.91 nm (granules) and 56.38 nm (tablets), with predominantly amorphous phase morphology preserved through pharmaceutical processing. FTIR confirmed phenolic O–H stretching (3420 cm⁻¹), fatty acid C–H chains (2920, 2851 cm⁻¹), ester carbonyl (1740 cm⁻¹), and aromatic C=C (1633 cm⁻¹), validating chemical composition. GC-MS identified 25 peaks with 19 characterised compounds; dominant bioactives include n-hexadecanoic acid (11.80%), combined heneicosane peaks (31.14%), hexadecanoic acid 2-hydroxy ester (10.39%), and heptadecene-(8)-carbonic acid-(1) (10.15%), with documented antioxidant, antimicrobial, and antiproliferative activities. Formulation F1 maintained IC50 = 21.22 mg/L unchanged over four weeks. Pharmaceutical processing preserves the nanostructural integrity and bioactive composition of palm leaf extract. The research validates a clean technology circular economy pathway converting palm leaf waste—currently 91.5 million tonnes dry weight annually in Indonesia—into stable, bioavailability-enhanced nutraceutical ingredients.
Copyright (c) 2026 Hanif Ardhiansyah, Fisa Savanti, Meci Aryani Saputri, Khusnul Khairul Nisa (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Optimizing Carica Waste Processing into Liquid Organic Fertilizer Using Bioconversion Techniques to Increase Agricultural Productivity in Kejajar District, Wonosobo
This community service program aims to optimize the use of Carica (Carica pubescens) waste into liquid organic fertilizer through bioconversion techniques, while simultaneously increasing the capacity of MSMEs and farmer groups in Kejajar District, Wonosobo. Activities include outreach, training, and mentoring in the production of liquid organic fertilizer on a household scale using simple technology based on decomposer microbes. The results of the community service show an increase in partners' knowledge and skills in Carica waste fermentation techniques, as well as in the production of liquid organic fertilizer with physical, chemical, and microbiological properties suitable for organic farming. Analysis shows decrease in pH and color changes, a distinctive fermentation odor, and increases in nutrient content (N, P, K), along with variations in substrate concentration. In addition, participants received mentoring on digital marketing strategies to increase the product's economic value. This program contributes to reducing Carica industrial waste, providing alternative organic fertilizers, and empowering local communities to improve welfare based on regional potential.
Copyright (c) 2026 Zuhriyan Ash Shiddieqy Bahlawan, Megawati Megawati, Irene Nindita Pradnya, Astrilia Damayanti, Indrasukma Permanadewi, Maulida Zakia (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Nutrient Recovery from Palm Oil Mill Effluent for Fertilizer Production: Technology Options and Practical Barriers
Palm oil mill effluent (POME) is a high-strength agro-industrial wastewater whose management governs both environmental performance and operational resilience of palm oil mills. Treatment trains optimized solely for COD/BOD reduction often accumulate operational penalties under feed variability, including scaling, sludge burden, and persistent polishing demands, rather than forming a controllable value-generating platform. This review reframes nutrient recovery from POME as a fertilizer manufacturing problem embedded in a wastewater system, where removal does not equal recovery unless nutrients are transferred into a defined product phase with mass-balanced yield, controlled composition, impurity management, and agronomic function. Anaerobic digestion is positioned as a pivotal pivot point because it converts organic load to methane while producing an anaerobically digested liquor that is operationally more suitable for targeted nutrient recovery than raw POME. Using a PRISMA-ScR scoping review with a systematic search, evidence was mapped across three coupled outcome domains: water reuse/reclamation, energy recovery (biogas/CH₄), and nutrient circularity (N–P recovery and derived products). The synthesis compares unit operations by function and operability constraints, then assembles feasible combinations into a process superstructure and a decision roadmap for pathway selection under mill constraints. Findings emphasize that raw POME and anaerobically digested POME are not interchangeable feedstocks: raw POME is dominated by solids/colloids that hinder selective recovery and contaminate products, while post-digestion variability is more chemistry-driven and governs precipitation windows and membrane stability. Recovery options converge toward hybrid systems integrating crystallization (struvite/phosphate minerals), adsorption/ion exchange with regenerability, membrane concentration including fertilizer-drawn forward osmosis, and biological assimilation (microalgae), with fouling, scaling, and crystallization inhibition as decisive design variables. Overall, meaningful nutrient recovery from POME is achieved only when fertilizer grade products are produced while simultaneously reducing compliance risk and operational burden.
Copyright (c) 2026 Agung Kurnia Yahya, Apsari Puspita Aini, Miftahurrahmah, Anang Baharuddin Sahaq (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Chronological innovations in biogas biodigesters design technology in Ethiopia
Biodigester design of National Biogas Programme of Ethiopia (NBPE) was modified five times from the year 2009 to 2023. Three more design model biodigesters were introduced namely small and medium scale prefabricated plastic geomembrane and medium sized fixed dome biodigesters. The five biodigesters modified were SINIDU 2008, SINIDU 2010, Solid State Digester (SSD), Black Cotton Soil Digester (BCD) and MITIN 2012 (2.5m3). Simplicity during construction, affordability, environmental conditions and needs of users were the main benefits obtained in chronologically improved SINIDU biodigester models. In NBPE, the last modified biodigester used in all environmental conditions was SINIDU 2010 that replaced both SINIDU and SINIDU 2008. Modification of the design did not have considerable change on daily biogas production rate. For example, SINIDU, SINIDU 2008 and SINIDU 2010 produces 2m3, 1.75m3 and 1.75m3 biogas per day with 50kg of daily cow dung, respectively. Introduced alternative prefabricated design was suitable for the users and masons as the design is easy to install and adaptable to different environmental conditions. Introduction of solid baffle to SINIDU 2008 and its following version to get less volume of buffer resulted in less Hydraulic Retention Time (HRT) from 50 days in SINIDU model to 35 days in SINIDU 2008. Other design modification was for MITIN 2012 biodigester which the manhole is at the top of the dome and sealed but for other models it is through outlet chamber. The design for BCD is robust than other designs due to its spherical/oval shape but for SINIDU model and its version, the shape of the digester is cylindrical. Innovations such as SSD and injera mitad and stove were at pilot stage and not scaled up. Therefore, research institutes and universities should strengthen additional roles on further modification/development of injera mitad and stove to get easy access to market penetration.
Copyright (c) 2026 Miftah F. Kedir (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Improvement of Microbial Fuel Cell Electricity Generating with Bacterial Isolate Implementation on Electrode in Liquid Waste of Pindang Fish Processing improvement of Microbial Fuel Cell Electricity Generating with Bacterial Isolate Implementation on Electrode in Liquid Waste of Pindang Fish Processing
Abstract Microbial Fuel Cells (MFC) can generate electricity from organic substances which is converted to simply chemical component to discharge protons and electrons by microbial activity. Microbial Fuel Cell (MFC) is a technology that produces environmentally friendly energy because MFC in its use does not produce CO2 emissions. Bacteria that is able to generate electricity grouped as exoelectrogen bacteria. Two kinds of bacteria has isolated from operating MFC with activated sludge need to find its performs which are Pediococcus acidilactici and Staphylococcus warneri. This study aims to determine the influence of sticking bacteria (Pediococcus acidilactici and Staphylococcus warneri) on electrode plates and the addition of activated sludge to increased electricity of MFC, reduce pollutant load from salt-boiled fish processing wastewater, and microbial density in electrode plates. This study has five stages, namely, bacterial cultivation, bacterial sticking on electrodes surface, activated sludge acclimatization, MFC assembly, and electrical measurement. This study used four treatments namely, electrodes that bacteria do not attach with and without added activated sludge (KoL and Ko), electrodes attached with bacterial isolates (anodes with Pediococcus acidilactici and cathode with Staphylococcus warneri) with and without active sludge (AKL and AK). AKL treatment obtained the highest average electrity value with a voltage value of 0.31±0.02 V, an electric current value of 3.28±0.66 mA, and a power value of 1.15±0.25 mW. Pollutant loads in COD, BOD, and TAN parameters decreased by 57%, 38%, and 92%. The sticking bacteria on the electrodes surface with activated sludge added was able to increase the density of bacteria on the electrode plate.
Copyright (c) 2026 Bustami Ibrahim, Desniar, Rofi Muyassar (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Ocean Wave Utilization for Renewable Power Generation Using Wave Energy Converters (WECs): A Review
The growing demand for electricity and the environmental impact of fossil fuel use have increased interest in renewable energy sources, including ocean wave energy. As a country with vast marine resources, Indonesia has significant potential to harness ocean waves as a clean and sustainable energy solution. This review explores various Wave Energy Converter technologies with a primary focus on the Oscillating Water Column system. The analysis covers ten recent studies that examine energy conversion efficiency, hydrodynamic performance, and field implementation. The findings indicate that the Oscillating Water Column system generally offers higher efficiency and greater operational stability than overtopping devices. Key factors influencing performance include wave height, wave period, chamber geometry, and turbine configuration. Case studies such as LIMPET in Scotland and OBREC in Italy provide evidence of real-world viability. Despite these advantages, challenges remain in terms of high construction costs, material durability in marine environments, and infrastructure limitations in coastal regions. This review highlights the importance of continued innovation, local adaptation, and policy support to enable the broader adoption of ocean wave energy, especially in island nations seeking to enhance energy resilience and reduce carbon emissions.
Copyright (c) 2025 Faranisa Febiola, Kanthi Prihastika Wijaya, Richa Amalia Fatma, Riziq Maulana (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Energy Transformation in the Dairy Industry Towards Process Efficiency and Environmental Impact Reduction
The dairy industry is among the most energy-intensive sectors within the food processing chain, relying heavily on fossil fuels for heating, cooling, and packaging operations. In response to global sustainability challenges and climate targets, this review explores integrated strategies for energy transformation in the dairy sector, focusing on renewable energy adoption, waste valorization, and digital technologies. Emphasis is placed on the use of soybean hulls—a rich source of lignocellulosic biomass—as feedstock for bioethanol production through a sequence of pretreatment, hydrolysis, fermentation, and distillation processes. Additionally, the role of biogas and solar energy integration, along with energy recovery systems and IoT-based monitoring, is analyzed for improving operational efficiency. The findings reveal that such transformations can reduce greenhouse gas emissions, lower operational costs, and increase energy self-sufficiency, especially when supported by circular economy principles. This review highlights the potential for scaling these solutions in both industrial and small-scale dairy production, offering practical insights into how renewable energy and digital innovation can drive a more competitive, sustainable, and decarbonized dairy industry.
Copyright (c) 2025 Rajwa Ruhing Raisha, Dimas Rafi Umara, Indah Nurhayati, Archil Inayatus Sa‘idah (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Valorization of Chicken Feather Waste in west Java into Bokashi Fertilizer Using Anaerobic Fermentation to Support Circular Agriculture: A Review
The rapid growth of the poultry industry in Indonesia, particularly in West Java, has resulted in significant chicken feather waste, which remains largely unutilized and poses environmental risks due to its high keratin content. This review explores the potential of converting chicken feather waste into bokashi fertilizer through anaerobic fermentation as a sustainable strategy in line with circular agriculture principles. The fermentation process involves pretreatment using keratinase producing microorganisms such as Bacillus subtilis or Pseudomonas aeruginosa, followed by the application of Effective Microorganisms (EM4) activated with molasses. Under optimal conditions, including a carbon to nitrogen ratio of 25 to 30 to 1, temperature between 30 to 40 degrees Celsius, and humidity around 50 percent, the process can produce high quality organic fertilizer that meets national standards. The resulting bokashi exhibits favorable physical and chemical characteristics, such as high nitrogen content and a balanced nutrient profile. More broadly, this approach offers a low cost, scalable, and environmentally friendly solution for managing livestock waste while enhancing soil fertility and supporting regenerative farming. With further optimization and wider implementation at the community level, chicken feather based bokashi has strong potential to contribute to sustainable agriculture and effective waste management in poultry producing regions.
Copyright (c) 2025 Satria Agung Saputra, Faatin Nisriinaa Zain, Kharisma Ardhani Nur Pratiwi (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Energy Efficiency in Palm-Based Food Production Processes in margarine industry through the Utilization of Palm Fiber as Solid Biomass in Boiler Systems: A Comprehensive Review
The increasing demand for margarine, especially in palm oil producing countries like Indonesia, raises concerns about energy consumption and environmental sustainability. This review discusses the potential of palm fiber, a lignocellulosic byproduct of crude palm oil extraction, as a solid biomass fuel to improve energy efficiency in margarine processing industries. A systematic literature review was conducted by analyzing more than sixty peer reviewed journal articles, technical reports, and case studies to evaluate the feasibility and impact of palm fiber utilization. Based on various studies, palm fiber contains 47.9 percent cellulose, has a calorific value of 17.2 megajoules per kilogram, and shows low ash and moisture content, making it suitable for combustion in industrial boilers. Emission data indicate reductions in carbon dioxide, nitrogen oxides, and sulfur oxides compared to fossil fuels, with potential greenhouse gas savings of 0.098 tons of carbon dioxide per gigajoule and sulfur oxide reductions of up to ninety percent. Economically, palm fiber offers cost savings of up to forty percent, with a levelized cost of energy around six United States dollars per gigajoule and a payback period of less than five years. The application of drying and co firing technologies, supported by policy incentives such as Indonesia’s capital expenditure assistance, could enhance adoption. Research gaps remain in terms of long term boiler corrosion and industrial scale briquetting. Overall, palm fiber supports circular economy practices and aligns with SDG 7, 12, and 13, contributing to cleaner energy transitions in palm oil based food production systems.
Copyright (c) 2025 Faatin Nisriinaa Zain, Kharisma Ardhani Nur Pratiwi, Mochammad Choiril Muna, Zuhriyan Ash Shiddieqy Bahlawan (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Recycling Palm Shell Waste into Biochar Using Biomass-Based Pyrolysis Method for Sustainable Energy Transition: A Review
Palm kernel shell (PKS), a by-product of Indonesia's palm oil industry, represents both a waste management challenge and an opportunity for renewable energy transition. This review critically examines recent advancements in the conversion of PKS into biochar using biomass-based pyrolysis. By synthesizing findings across multiple studies, the review highlights how pyrolysis parameters—such as temperature (200–1200 °C), residence time (1–4 hours), and chemical activation (NaOH, H₂SO₄)—affect the physicochemical properties of biochar. Among these, the combination of 550 °C pyrolysis temperature, 2-hour residence time, and NaOH pre-treatment via microwave-assisted pyrolysis was identified as optimal for maximizing fixed carbon content, surface area, and adsorption capacity. Such biochar is suitable for a wide range of applications, including soil amendment, wastewater treatment, and long-term carbon sequestration. The review not only confirms the environmental viability of PKS biochar based on Indonesian National Standards (SNI), but also emphasizes its role in supporting sustainable agriculture and mitigating greenhouse gas emissions. Future research directions include scaling production technologies and assessing biochar performance in diverse agroecological systems.
Copyright (c) 2025 Naswa Mevira Setiawan, Sella Stephanie, Annisa Nazilatul Aziz, Berliana Yusfinda (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Energy Consumption and Efficiency Optimization in Freeze Drying of Fruits and Vegetables: A Review
Fruits and vegetables are essential for global nutrition and economic growth, yet they are among the most perishable food commodities, contributing to major postharvest losses worldwide. Freeze drying is widely recognized as a superior preservation method that maintains the structural integrity, nutritional value, and sensory quality of fresh produce. Despite its advantages, freeze drying is energy-intensive, posing challenges for cost-effectiveness and sustainability in large-scale applications. This review explores the freeze drying process in detail, highlighting the critical operational parameters such as freezing rate, chamber pressure, shelf temperature, and sample thickness, that influence both product quality and energy consumption. Additionally, the role of cryoprotectants in preserving bioactive compounds during drying is discussed. By identifying optimization strategies for these parameters, this study aims to support the development of more energy-efficient and economically viable freeze drying systems for the fruit and vegetable processing industry.
Copyright (c) 2025 Kirana Maharani Zudana, Fitri Wahyuni, Sheila Azzahra Putri, Yuniar Nanda Lestari (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
High-Pressure Processing (HPP) Energy Efficiency and Scalability Challenges in Ultra-Processed Meat: A Review
The global expansion of ultra-processed meat products (e.g., sausages, nuggets) faces dual challenges: microbiological safety risks from conventional thermal processing and rising consumer demand for clean-label, nutritious options. High-Pressure Processing (HPP) emerges as a promising non-thermal technology to address these concerns by inactivating pathogens while preserving sensory and nutritional quality. However, its industrial adoption is hindered by significant energy efficiency and scalability constraints. This systematic literature review synthesizes recent research to critically analyze these barriers. Methodologically, we conducted a Systematic Literature Review (SLR) using databases such as Scopus, ScienceDirect, Web of Science, and PubMed, focusing on studies related to High-Pressure Processing (HPP) applications in ultra-processed meats. Our analysis reveals that HPP consumes 2.5–3.2 kWh/kg up to 26× more energy than thermal pasteurization primarily due to hydraulic system demands and adiabatic heat dissipation during batch cycling. Scalability limitations stem from batch-based processing (3–7 min/cycle), vessel size constraints (<500 L), and capital costs reaching $2.5 million per unit, resulting in only 18% adoption by large-scale manufacturers. Energy recovery inefficiencies and product matrix variations (e.g., lipid-protective effects in emulsified meats) further exacerbate these challenges. Emerging solutions include semi-continuous systems (35% throughput increase), pulsed HPP protocols (18% energy reduction), and solar-hybrid installations (40% emission cuts), though economic viability remains problematic. We conclude that while HPP offers unparalleled safety and quality benefits, its scalability and energy intensity require coordinated innovations in process engineering, renewable energy integration, and cooperative industry models to achieve sustainable implementation.
Copyright (c) 2025 Shaka Kusuma Nurjati, Muhammad Adam Purnawan, Rizma Stevviani (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
Artificial Intelligence in Renewable Energy: A Review of Predictive Maintenance and Energy Optimization
The integration of Artificial Intelligence (AI) into renewable energy systems represents a transformative step in enhancing the efficiency, reliability, and sustainability of clean energy technologies. This review explores the roles and applications of AI techniques—including Machine Learning (ML), Deep Learning (DL), Reinforcement Learning (RL), and ensemble models like XGBoost—in predictive maintenance and energy optimization. Through a comprehensive analysis of recent studies, the review highlights how AI improves system performance by enabling early fault detection, optimizing energy distribution, and managing storage efficiently. Predictive maintenance driven by AI can reduce unplanned downtime by up to 35% and enhance energy output by approximately 8.5%. In energy optimization, AI models forecast demand and control load distribution, significantly contributing to smart grid development. However, several challenges remain, particularly in Indonesia, including limited high-quality data, high computational demands, system interoperability issues, and a lack of regulatory and human resource readiness, reducing unplanned downtime by up to 35% and increasing energy output by approximately 8.5%, as reported in previous studies. The review concludes that successful implementation requires strategic investment in digital infrastructure, inter-sectoral collaboration, and pilot projects to ensure sustainable AI adoption in Indonesia's renewable energy sector.
Copyright (c) 2025 Arimbi Mutiara Suci, Rofiqoh Amini, Agnes Kusuma Asri, Nicolas Martin (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
The Potential Utilization of Biomass as Substitute Renewable Energy in Supporting Energy Security in Central Java
The utilization of rice straw as a renewable energy resource has received growing attention in the context of regional energy security and carbon emission reduction, particularly in Central Java, Indonesia. This review explores the potential of rice straw as a feedstock for bioethanol production, emphasizing its primary lignocellulosic components—α-cellulose, hemicellulose, and lignin—and key conversion stages, including pretreatment, hydrolysis, fermentation, and purification. In addition, the performance of various technologies for converting bioethanol into electricity is critically examined. Among these, Direct Ethanol Fuel Cells (DEFCs) are identified as the most efficient, offering conversion efficiencies of 40–60% and notable environmental advantages over conventional ethanol-fueled combustion generators. The findings suggest that the integration of high-efficiency conversion technologies with the region’s abundant rice straw resources could represent a strategic pathway toward a more sustainable and low-emission regional energy system.
Copyright (c) 2025 Rahma Dhani Fatonah, Arvie Tri Listiyani, Sindi Dwi Putri, Rossa Dwi Nur Insani (Author) https://creativecommons.org/licenses/by-nc-nd/4.0
A Review of Process Intensification Strategies in Biodiesel Production from Waste Cooking Oil to Enhance Efficiency and Sustainability
The global energy crisis and environmental concerns from fossil fuel use have driven the development of renewable biofuels. Biodiesel produced from waste cooking oil (WCO) is a promising option due to its low cost, wide availability, and non-competition with food resources. However, WCO typically contains high levels of free fatty acids (FFA), moisture, and impurities that hinder efficient conversion. This review highlights recent advances in process intensification strategies to improve WCO-based biodiesel production. Pretreatment methods such as heating, filtration, and centrifugation reduce contaminants, while acid esterification lowers FFA before transesterification. The physicochemical properties of WCO, particularly acid value and viscosity, are critical for setting optimal reaction conditions. Catalysts like NaOH (homogeneous), CaO from waste shells (heterogeneous), and bifunctional Mo₇-Zn₃/CaO are widely used to enhance reaction efficiency. Advanced reactors—especially microwave- and ultrasonic-assisted systems—significantly improve yield and energy efficiency. For instance, microwave-assisted transesterification using Mo₇-Zn₃/CaO achieves 94–96% biodiesel yield within 5–10 minutes at 65 °C, reducing energy consumption by up to 40% compared to conventional methods. Most approaches meet ASTM D6751 and EN 14214 fuel quality standards. Life cycle assessments show that WCO biodiesel can reduce greenhouse gas emissions by 75–80% compared to fossil diesel. The use of waste-derived catalysts and recycling of by-products such as glycerol supports circular economy goals. Nonetheless, challenges like variable WCO quality and high capital costs for advanced reactors remain. Future work should focus on scalable reactor development, realtime monitoring, and supportive policy frameworks to promote sustainable biodiesel production at an industrial level.
Process Intensification, Heterogeneous Catalyst
Copyright (c) 2025 Journal of Clean Technology https://creativecommons.org/licenses/by-nc-nd/4.0
Zero Waste Education Organic Waste Treatment for Students of SD N Petompon 3
Improper waste management at SDN Petompon 3 Semarang has led to inadequate sanitation and a lack of environmental awareness among students. This community service initiative aimed to address these issues by educating 5th and 6th-grade students on organic waste processing through the utilization of Black Soldier Fly (BSF) larvae. The program introduced a hands-on approach where students learned to sort, manage, and convert organic waste into value-added products such as animal feed and organic fertilizer. Additionally, the program incorporated entrepreneurship training, equipping students with basic skills in packaging, branding, and marketing to promote sustainable small-scale enterprises. The activities included stakeholder coordination, infrastructure preparation, environmental education, and product processing workshops. Results showed improved student participation, increased environmental knowledge, and measurable growth in maggot biomass and waste decomposition rates over 30 days. This integrated program not only enhanced environmental cleanliness at the school but also fostered early environmental stewardship and entrepreneurial skills among students, contributing to sustainable waste management and community empowerment.
Copyright (c) 2024 Journal of Clean Technology https://creativecommons.org/licenses/by-nc-nd/4.0
Study of Nitrification Process in a Media Raised Bed Based Aquaponic System
Aquaponics is an integrated and sustainable farming method that combines aquaculture and hydroponics in a recirculating water system. This system utilizes fish waste as a nutrient source for plants, and the plants act as biofilters to clean the water before it returns to the fish tank. A critical process in this system is nitrification, where ammonia is converted into nitrite and nitrate by beneficial bacteria, reducing toxicity to fish and providing nutrients for plants. This study investigates the efficiency of the nitrification process using four different biofilter media—rockwool, pumice stone, gravel, and zeolite—in a media-raised bed aquaponic system. Results showed that pumice stone provided the highest nitrate concentration (131.62 mg/L), indicating superior nitrification performance. The findings offer valuable insights for optimizing biofilter media selection in aquaponic systems, which is crucial not only for maintaining water quality but also for enhancing crop productivity. The study contributes to the development of more efficient and sustainable aquaponic designs, particularly in regions facing water scarcity and the need for integrated food production solutions.
Bioethanol Production as Renewable Energy from Macroalgae Eucheuma cottonii: A Mini Review
Energy demand has increased from several years ago due to economic growth and population increase. Meanwhile, non-renewable energy reserves from fossil fuels are dwindling. Bioethanol is one alternative energy resource to substitute fossil fuels and their derivatives. The fast expansion and environmental friendliness of Eucheuma cottonii macroalgae's growth make it a promising contender for use as a sustainable renewable energy source. Because of its abundant carbohydrate content, it can be utilized in generating bioethanol. This analysis delves into the potential of macroalgae in bioethanol production by concentrating on hydrolysis and fermentation. The Eucheuma cottonii process involved hydrolyzing it into reducing sugars using an optimal dilute acid hydrolysis pretreatment. This hydrolysate is converted into bioethanol by Saccharomyces cerevisiae through fermentation. Process the bioethanol obtained is distilled to reach the maximum concentration. The process of producing bioethanol, which is a renewable energy source, is expected to have an important impact on dealing with the energy crisis and advancing environmental sustainability.
Bioethanol, Fermentation, Eucheuma cottonii, Renewable Energy, Yeast
Copyright (c) 2024 Journal of Clean Technology
Bioethanol Production from Corn Cob Trough Utilization of Agrobiomass Waste in East Java as Renewable Energy : a Review
The demand for energy from fossil fuels continues to surge along with the rapid development of industry and the economy. Efforts to reduce dependence on fossil energy, especially the limited petroleum, are crucial. Therefore, it is necessary to increase the utilization of other energy sources, especially bioethanol, which is renewable and environmentally friendly. The production of bioethanol is intensifying due to market stability, low costs, sustainability, its role as an alternative fuel, and the risk of fossil fuel depletion. Corn cob waste comprises various organic compounds, including 40-60% cellulose, 20-30% hemicellulose, and 15-30% lignin. These compounds can be transformed into various forms of bioenergy, including bioethanol, biogas, and bio-oil. The process of producing bioethanol from corn cobs involves pretreatment, hydrolysis, fermentation, and distillation. The production of bioethanol from corn cob waste consists of several stages: pretreatment, hydrolysis, fermentation, and distillation. Lignin impedes acid penetration before hydrolysis and inhibits microbial growth during fermentation, so it must be removed through alkaline pretreatment. Glucose production from alkali-treated corn cobs can be achieved through hydrolysis using chemical or enzymatic catalysts. Acid hydrolysis with 21% H2SO4 and 21% HCl is preferred due to its shorter operating time. On the other hand, the high cost of enzymes and the extended operating time diminish production efficiency. The acid hydrolysis method using 21% H2SO4 requires 1 hour, 2 hours, and 3 hours and uses 21% HCl at a temperature of 100°C with a yield of less than 10%. The production of bioethanol from corn cobs is carried out using the SHF and SSF methods. The SSF method yields a range of 1.94%-88.37%. The SHF method yields a range of 0.28%-0.57%. Distillation is employed to remove impurities from liquids contaminated by dissolved substances from corn cobs, which have varying boiling points. Vacuum distillation can achieve a purity level of 89%. Converting corn cob into bioethanol aids in reducing environmental pollution and promotes the use of clean energy.
Bioethanol, Corn Cob, East Java, Fermentation, Fossil Fuel
Comparison of the Effectiveness of Electrical Energy Production from Livestock Manure by Optimization using Combined Heat and Power (CHP) Method: A Literature Review
Livestock manure is a potential source of renewable energy. This study compares the effectiveness of electrical energy production from livestock manure with and without optimization using the Combined Heat and Power (CHP) method. Using the CHP method can improve energy efficiency by utilizing the heat generated from burning livestock manure to produce electricity and heat. The literature shows that CHP can significantly improve energy efficiency. The energy efficiency of CHP systems can reach 80%, compared to 30-40% for conventional systems. In addition, CHP can produce lower greenhouse gas emissions compared to traditional systems. The study also shows that CHP can be an economical solution to generate electrical energy from livestock manure. CHP systems can generate significant economic benefits in the long run.
Livestock manure, CHP, renewable energy, energy efficiency
Utilization of Palm Solid Residue For Bioethanol Production In Sumatra Indonesia – A Review
The combustion of fossil fuels causes an increase in the release a group of gases found in the earth atmosphere that trap heat and contribute to the greenhouse effect, which in turn contributes to the occurrence of global warming. The advancement of sustainable energy sources plays an important role in human life due to renewable and environmentally friendly. This problem can be resolved by using alternative fuels as renewable sources of energy that are more environmentally friendly, such as bioethanol. Empty fruit bunches (EFB) constitute a portion of the solid waste that cause problems in storage, transportation, and processing costs. This is because EFB is waste in a solid that is produced from a processing facility where the fruits of the oil palm tree are processed to extract palm oil in large quantities. The process of producing bioethanol by utilizing coconut fruit bunches that are devoid of their contents as a raw material involves two essential stages: hydrolysis and drying. Hydrolysis with an acid catalyst results in a lower yield, but the catalyst itself is inexpensive. Conversely, when using enzyme catalysts, hydrolysis produces a greater quantity of reducing sugars. Enzyme catalysts can be employed in the simultaneous saccharification and fermentation (SSF) process using S. cerevisiae yeast, while chemical catalysts can be used in separate hydrolysis and fermentation (SHF) methods. The SSF method provides a comparatively elevated ethanol yield, demands less enzyme usage, has a shorter duration for ethanol production, and is environmentally friendlier when compared to the SHF procedure.
Bioethanol Production from Sago Waste as Renewable Energy: A Review
Energy consumption has increased rapidly because the world population has grown, so has energy consumption for industrial needs. Now Indonesia still uses fossil fuels as the main energy source, because of their non-renewable nature, the continuous use of fossil fuels causes scarcity problems. Bioethanol production is currently getting more intense, this is because there are several factors that cause it to be more intense, namely market stability, low costs, sustainability, the composition of alternative energy fuels and the catastrophic depletion of fossil fuels. Sago waste can be used as an environmentally friendly renewable resource. Bioethanol production process from sago waste using enzymes and fermentation with the help of microorganisms. The bioethanol production process from sago waste has four main parts. The first thing to do is the pre-treatment process, namely drying the sago pulp and delignification process. Samples from the delignification process will then be used in the hydrolysis process with a catalyst in the form of HCl. The results of the hydrolysis were fermented at a pH of 5 and tape yeast was added. Then in the distillation process requires filtrate which was then evaluated qualitatively using K2Cr2O7 reagent. The mixture derived from the fermentation process using baker's yeast and wet sago pulp can produce bioethanol levels up to 45.70%. The process of making bioethanol from sago waste through a baker's yeast fermentation process is expected to help advance the bioethanol production process as a renewable energy source in Indonesia.
Sustainable Production of Biofuels from Microalgae (Chlorella vulgaris) Using Irradiation Microwave as Future Green Energy; a Review
Biodiesel is a solution to the problem of depleting fossil fuel sources in Indonesia. Biodiesel can be derived from vegetable and animal fats. On the other hand, microalgae cultivation areas are spread across 26 provinces in Indonesia with a production potential of 462,400 tonnes/year. Microalgae with lipid content ranging from 38% - 60% can be converted into crude biodiesel as much as 35%. Irradiation microwave is the simplest and most effective technology with a constructive method for extracting oil from animal and vegetable fats, and biomass, and can be scaled easily. Using irradiation microwave, oil will be extracted from microalgae using hexane: methanol solvent for 60 minutes with a microwave power of 600 watts. Microalgae extraction with the help of irradiation microwave can produce more lipids compared to conventional lipid extraction which is 31% and 26% higher. Microalgae that go through a treatment process using irradiation microwave is more efficient because the average cost is two-thirds less compared to conventional heating, its lower energy consumption, lower costs, a more effective heating process, can increase production, and have a big impact on increasing biofuel yields.
Utilization of Rice Straw Waste as a Source of Bioenergy: A Review
The rice straw waste is a byproduct of rice processing and is a plentiful natural resource in Indonesia. It has been utilized as a renewable energy source to decrease reliance on fossil fuels and tackle worldwide energy concerns. Rice straw waste contains various organic compounds, such as 36.6% cellulose, 25.3% hemicellulose, and 14.3% lignin. These compounds can be converted into various types of bioenergy, such as bioethanol, biogas, biomass, and bioelectricity through fermentation and pyrolysis processes. Rice straw waste has significant potential as a raw material in bioethanol production, biogas and bio-oil. rice straw waste also has the potential to produce bio-oil through the pyrolysis process. Tiny organisms, like bacteria and fungi, have a crucial part in the creation of bioethanol, biogas, and bio-oil. These microscopic organisms will be used in the process of fermentation, decomposition, or other biochemical reactions to convert rice straw waste into the desired renewable energy source. In the production of bioethanol, the use of enzymes such as amylase or cellulase may be required to break down the raw materials into simpler components that can be converted through the fermentation process into bioethanol. The process of producing biogas involves utilizing an anaerobic digester, which is a controlled environment devoid of oxygen. In this environment, microorganisms decompose the organic material found in rice straw waste and generate biogas. The methods used in the production of bioenergy (bioethanol, biogas and bio-oil) from straw waste may vary depending on the context and available technology.
Bioethanol Production from Rice Straw through Utilization of Agrobiomass Waste in Central Java Towards Clean Energy: a Review
Bioethanol is an alternative energy to replace fossil fuels from plants. Central Java is the second largest rice producer in the world in Indonesia, with the potential of rice straw waste which can be optimized into bioethanol. Rice straw contains abundant cellulose reaching 32-47%, hemicellulose reaching 19-27%, and lignin reaching 5-24%. Methods for making bioethanol from rice straw include pretreatment, hydrolysis, fermentation, and distillation. Lignin inhibits acid penetration before hydrolysis and microbial growth during fermentation, so it needs to be eliminated using alkaline pretreatment. Glucose production from alkali-pretreated rice straw can be hydrolyzed using chemical or enzymatic catalysts. Acid hydrolysis method using dilute H2SO4 with consideration of a shorter operating time. In addition, the price of enzymes is very high, and the operating time is very long, which will reduce product effectiveness. The acid hydrolysis method using 2% H2SO4 takes 30 minutes at 150 oC, which can produce a yield of 16%. Production of bioethanol from rice straw using separate hydrolysis and fermentation (SHF) methods. Saccharomyces cerevisiae, with a 24-hour fermentation time, produced a yield of 80.9% and a productivity of 0.172 g/L h. Distillation is used to remove impurities from liquids that have been polluted with rice straw-derived solutes with various boiling points. Vacuum distillation can produce a yield of 40% purity. Utilization of rice straw into bioethanol can reduce environmental pollution so that it supports clean energy.
Bioethanol, rice straw, Central Java, clean energy