The growing demand for energy and emerging environmental concerns are making it necessary to look for more sustainable alternatives. To address the limitations of first-generation biofuels and reduce dependence on fossil fuels, this study focuses on second-generation bioethanol sourced from non-edible pomegranate waste. This study develops and analyses a supply chain optimization model for the sustainable production of biofuel from pomegranate waste and solves it using a genetic algorithm. The framework assesses key supply chain elements, including collection centres for pomegranate waste, processing plants, bio-refineries for conversion and distribution centres for final bioethanol. The primary objective of the optimization is to reduce the total cost of the biofuel production system and to maximize positive environmental impact through waste valorization. A numerical example validates the framework, and a sensitivity analysis further evaluates the economic viability of the supply chain under fluctuating market conditions, such as variations in the purchasing cost of waste, the production cost of bioethanol and the opening cost of plants. Biofuel production supports the Sustainable Development Goals (SDG-12 and -13) by transforming waste into renewable energy. This study aims to address gaps in biofuel research by focusing on the underutilized area of pomegranate-based biofuel through an integrated supply chain optimization framework. The findings offer practical values for researchers working on renewable energy solutions, policymakers and business leaders.

Ammonia, as a hydrogen carrier and clean fuel, has an increasingly urgent demand for large-scale transportation. Utilizing the existing refined oil pipeline network for sequential transportation of ammonia and refined oil is an economically and efficiently feasible solution. However, the unique micro-solubility characteristics of ammonia and refined oil can cause significant differences in the mixing mechanism of the two substances during sequential transportation in the pipeline compared to traditional oil products. This study conducts transient flow numerical simulation and mechanism research on the mixing problem during the sequential transportation process of ammonia and refined oil under the influence of micro-solubility transfer. Using the ANSYS Fluent platform and combining it with the dynamic mesh technology, a sequential transportation pipeline model was constructed. In the VOF multiphase flow model framework, the Fick diffusion and convective transfer theories were coupled. Through the development of user-defined functions, a transfer model was established to describe the ammonia dissolution process in refined oil during sequential transportation. This model characterizes the axial transfer process of the two-phase flow and the dissolution transfer in the pipeline. Then, the correctness and accuracy of the transfer model were verified, proving that the model has reliable simulation capabilities. To evaluate the comprehensive influence of various engineering factors on the mixing law, this study selected seven key parameters. It then designed and simulated multiple sets of comparative conditions. The influence of each parameter on the development of the mixing section was analyzed, and a sensitivity analysis was conducted. Subsequently, using the growth rate of the mixing length (dL/dt) as the dependent variable to represent the dynamic development of the mixing process, and using the above seven parameters as independent variables, a semi-empirical fitting formula was established. This formula can comprehensively reflect the coupling effect of multiple factors. The results show that the model has good generalization ability and extrapolation robustness. It provides a prediction model and theoretical tool with certain engineering practical value. This can be used for predicting the amount of mixing and optimizing operating parameters in actual pipeline sequential transportation systems.

In the Philippines’ agricultural setup, pre-harvest cacao (Theobroma cacao) fruits are wrapped with low-density polyethylene (LDPE) for moisture retention and damage protection. Responding to the growing concern for its waste volume and scarcity of treatment, this research explores the co-hydrothermal carbonization (co-HTC) of cacao shells (CS) and LDPE as a method to convert agricultural waste with plastic into hydrochar for potential energy applications. Thus, observations on the thermal, physicochemical, and morphological changes from feedstocks to hydrochar are carried out. Optimal conditions of 200 °C for 60 min resulted in hydrochar with 21.11 MJ/kg and appreciable thermal properties. SEM micrographs show that hydrochar had increased surface area, a good fuel characteristic, and surface flaking on oversized LDPE film, suggesting relative LDPE degradation. EDX analysis reveals C, K, Ca, and Zn metals that affect chemical pathways. FTIR analysis further supports chemical synergy by preservation of functional groups innate from both parent materials. Kinetic and thermal evolutions are also investigated to reveal the influence of pretreatment on the stability of cacao shell-dominated hydrochar and the effectivity of biomass integration to facilitate relatively easier cracking of LDPE. The findings support co-HTC as a viable technology to enhance the circular economy by valorizing LDPE and cacao shells while promoting energy recovery and solid fuel production.

Bioenergy production from agro-industrial waste has the potential to contribute to climate change mitigation. In Brazil, the pequi (Caryocar brasiliense Camb.) production chain makes an economic, environmental, and social contribution. However, the collection and processing of the fruit produce large amounts of waste, such as the peel, whose improper disposal leads to significant environmental impacts. This study evaluated how moisture and carbonization temperature influence the energy properties of charcoal briquettes made from pequi peel waste. Carbonization was performed at two final temperatures (360 °C/480 °C) with a heating rate of 1.5 °C min−1 and residence times of 4 h and 5 h 20 min, respectively. Carbonization yields were calculated based on dry mass. Briquettes were produced from pequi peel at moisture contents of 5%, 7.5%, and 10% (wet basis). After carbonization, the charcoal briquette samples were characterized by proximate analysis, higher heating value (HHV), bulk density, energy density, and mechanical durability. Carbonization temperature exerted a more pronounced effect on the properties of the carbonized briquettes than the initial moisture content. Carbonization at 480 °C increased the fixed carbon content (76.38%, 74.25%, and 75.10% for treatments 1, 2, and 3) and the HHV (25.10–25.31 MJ kg−1), while reducing the gravimetric yield (32.84–33.25%). The influence of moisture content was more evident in carbonizations carried out at 360 °C, indicating a temperature-dependent interaction. The use of pequi peel for solid biofuel production promotes the valorization of agro-industrial residues and supports strategies aimed at the circular bioeconomy and the decarbonization of the energy matrix.

To investigate the synergistic effect of hydraulic fracturing and hot water injection on enhancing methane extraction from low-permeability coalbeds and elucidate the underlying thermal-hydraulic coupling mechanism, methane desorption experiments were conducted in coal samples with varying fracture networks using a self-developed multi-field coupling experimental system. Tests were performed under different injection pressures and temperatures to analyze coal temperature evolution and methane desorption-seepage characteristics. The results demonstrate that hydraulic fracturing significantly improves pore structure and connectivity, thereby optimizing methane desorption behavior. The methane migration in the samples is influenced by water injection, exhibiting an initial promotion followed by inhibition. The combined fracturing-thermal injection approach effectively reduces the dynamic viscosity of water, mitigates the water lock effect, and enhances the desorption capacity. The hydraulic fracturing and the hot water injection complement each other, achieving synergistic production enhancement. The optimal injection pressure and water temperature can be selected according to specific reservoir conditions to balance the production increase and cost efficiency. This laboratory-scale study provides theoretical support for optimizing hydraulic measures and thermal injection techniques in coalbed methane extraction, revealing complementary synergies between these two methods and offering new insights into multi-field coupling enhancement mechanisms with practical application guidelines.

Fossil fuel depletion has increased interest in renewable alternatives such as biodiesel derived from non-edible plant oils. Droplet evaporation is a key process influencing fuel–air mixing and combustion efficiency in diesel engines. In this study, the evaporation characteristics of diesel and two non-edible biofuels, Jatropha and Castor, are investigated using computational fluid dynamics (CFD) under high-temperature and high-pressure conditions representative of engine environments. The numerical model incorporates the conservation equations of mass, momentum, and energy, together with the k–ε turbulence model and a discrete phase model to simulate droplet heating, motion, and mass transfer during evaporation. A comparative CFD analysis is performed to examine how fuel properties, ambient temperature, and droplet size affect the evaporation behaviour of diesel, Jatropha, and Castor droplets under identical engine-like conditions. The evolution of droplet diameter, temperature, velocity, and lifetime is analysed, and the applicability of the classical D2-law is evaluated under different operating conditions. The results indicate that biofuel droplets generally evaporate faster than diesel droplets at lower temperatures, while evaporation trends become similar at higher temperatures. These findings provide insight into the evaporation behaviour of Jatropha and Castor fuels and their potential application in diesel engines.

An exorbitant amount of organic fractions of the municipal solid waste, i.e., fruit and vegetable waste (FVW), generated from farm to fork are being treated through anaerobic digestion (AD). Anaerobic digestion (AD) of FVW only achieves <60% methane potential due to methanogen loss and indirect electron transfer. Hence, the technology necessitates further improvements in performance to maximise the methane gas yield by stabilising the methanogens using a potential additive. Magnetic biochar is a budding and promising additive in anaerobic digestion that amplifies biomethanation performance. This study focuses on the role of magnetic biochar in enhancing the viability of the AD system in biogas production from organic waste fractions. Herein, the magnetic biochar was produced using a FeCl3-impregnated walnut shell and then characterized. The derived magnetite was identified as the major crystalline phase in biochar with the presence of several oxygenated functional groups. The specific surface area, pore volume, and pore diameter were found to be 360.99 m2 g−1, 0.089 cm3 g−1, and 0.98 nm, respectively. The SEM and TEM images illustrated a good dispersion of the material, with size ranging between 18.2 and 46.6 nm, thus indicating the porous nature of the magnetic biochar. The incorporation of magnetic biochar in the CN ratio modified the AD system with enhanced methane production and the highest volume (1523.4 mL) reported in treatment, with a CN ratio of 25:1 and 0.5% magnetic biochar. The resulted gas yield is 35% more than the control (1125 ML) with reduced lag phase (4 vs. 12 days). It concludes that walnut shell MBC uniquely combines DIET conduits and biofilm support and enhances methane production from FVW. However, 16S rRNA confirmations of syntrophs, continuous reactor validation, and magnetic biochar recovery and reuse potential studies are essential for further scaleup.

Biogas is increasingly recognized as a strategic component of Indonesia’s clean energy transition; however, household-level adoption remains limited, even in livestock-dense regions. This study provides one of the first empirical assessments in Indonesia that integrates socioeconomic, behavioral, and institutional determinants of household biogas adoption within a unified analytical framework. Focusing on dairy-farming households in West Java Province, we examine why adoption remains low despite significant manure-based energy potential. Guided by the hypothesis that institutional support and household perceptions exert stronger influence on adoption than resource availability alone, we apply a binary logistic regression model to data from 201 households (101 adopters and 100 non-adopters). The analysis incorporates structural variables (income, livestock ownership, and electricity access) together with perceptual and experiential factors (fuel-cost pressure, perceived time savings, and participation in training). Contrary to conventional expectations, higher education is negatively associated with adoption, reflecting Indonesia’s LPG price distortions and aspirational energy preferences. In contrast, fuel-cost pressure, livestock ownership, perceived time savings, and training participation significantly increase adoption likelihood. These findings underscore that effective biogas dissemination requires not only physical resources but also strengthened institutional support, improved technical capacity, and targeted awareness-building interventions.

In the process of using the freezing method to uncover coal from stone gates, the thermal evolution profiles of the coal body during the freezing process tend to be complex due to the presence of gas and moisture. To investigate the temperature response of coal containing gas under different freezing temperature conditions, a self-developed low-temperature freezing test system for coal containing water and gas was used to conduct freezing and cooling tests at different freezing temperatures (−5 °C to −30 °C). The temperature changes at various measuring points inside the coal over time were monitored in real time, and the temperature distribution, cooling law, and strain evolution process of the coal in the axial and radial directions were analyzed. The experimental results show that the cooling process of the center point of the coal can be divided into four stages: rapid cooling, extremely slow temperature drop, relatively slow cooling, and stable constant temperature. The time required to reach the stable constant temperature stage is inversely proportional to the freezing temperature, and corresponding prediction formulas have been established based on this. The standardized coal briquettes exhibit a gradient distribution characteristic of gradually increasing temperature from outside to inside in both axial and radial directions, with the radial temperature distribution being well matched by an exponential decay model. The strain of coal is affected by both thermal shrinkage and ice-induced expansion. The occurrence time of frost heave is positively correlated with freezing temperature, while the strain of frost heave is negatively correlated with freezing temperature. The axial frost heave effect is significantly stronger than the radial effect, but the radial frost heave occurs slightly earlier than the axial effect. This study reveals the thermal-mechanical coupling response mechanism of gas-containing coal during the low-temperature freezing process, and the research results can provide theoretical support for parameter optimization and engineering application of low-temperature freezing anti-outburst technology.

A Cantera-based combustion-kinetics framework that maps the operating space of hydrogen compression ignition (H2-CI) engines and establishes a structured charter to guide experiments. Beginning with a diesel (n-dodecane) baseline at an intake temperature of 300 K, the model is virtually converted to neat hydrogen and evaluated across intake temperatures of 400–600 K, compression ratios (CR) of 20–28, and exhaust gas recirculation (EGR) levels of 0–15%. Hydrogen demonstrates stable operation across a broad equivalence ratio window (ϕ = 0.45–2.1), achieving power outputs of 16–22 kW and higher efficiencies with substantially lower fuel mass than diesel. The optimal operating region is identified at an approximately 400 K intake temperature, CR = 24–28, and EGR between 5% and 10%, where power remains high (20–18 kW), efficiency increases (above 50%), and NOx emissions are markedly reduced (from 332 ppm at zero EGR to 48 ppm at 5% EGR and 10 ppm at 10% EGR), with only modest hydrogen slip (0.07–0.11). The kinetics-based framework thus provides a systematic and validated roadmap for experimental calibration, research, and development of compression ignition engines working on pure hydrogen.