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To help mitigate the effects of global warming and fossil fuel depletion caused by human use of fossil fuels, solid fuel pellets were developed from a mixture of spent coffee grounds (SCG) and pine sawdust (PS). The feasibility of SCG-PS pellets as biofuel was also verified by evaluating its fuel quality. An increase in the proportion of SCG in the pellet led to an increase in its calorific value, owing to the high C, H, and oil contents, and increases in the ash and S contents, owing to the high S content in SCG. Analysis of the feedstock particle size distribution revealed that SCG particles are smaller than PS particles; thus, the durability of the pellet decreases as the proportion of SCG increases. Accordingly, the samples with higher SCG proportions (70 and 90 wt.%) did not meet the moisture content standards for biomass solid refuse fuel (bio-SRF) set by the Korea Ministry of Environment, whereas the samples with lower SCG proportions did. In particular, CP10 (10 wt.% SCG + 90 wt.% PS) satisfied the quality standards of Grade 1 wood pellets, demonstrating the feasibility of using SCG as a raw material for biofuel pellet production.

Fuels should behave appropriately in all sections of the engine system: the engine, fuel delivery system, and tank. Fuel quality can be linked to the following three crucial areas: performance, fitness for current use, and stability. Classical methods of diesel fuel examination mostly rely on the absolute value measurement of one specific parameter while stabilizing outside conditions. In contrast, multiparametric methods depend on simultaneously measuring a set of parameters. Therefore, multiparametric methods open the possibility of intriguing new examinations and classifications of diesel fuel quality while raising specific issues relating to the instrumentation and construction of sensing devices. This paper presents a review, based on the published literature and the authors’ research, of the current state-of-the-art multiparametric methods for rapid diesel fuel quality classification and related instrumentation, systematizing the various types of methods from the point of view of the principles of their operation. The main conclusion is that different measuring procedures use similar methods of data processing. Moreover, the heavy, costly, and complex devices that enable standard examinations can be converted to simpler devices in the future, whose cost of use is significantly lower. However, to achieve this, progress in electronic devices is required.

Hydrothermal liquefaction (HTL) of algal biomass is a promising approach for renewable biofuel production. The actual study investigates the effects of reaction temperature (225–325 °C), residence time (15–60 min), algae-to-water mass ratio (1:5–1:20), and pressure on the yield and quality of biofuel derived from municipal wastewater-grown mixed algal-cyanobacterial biomass. Eleven HTL experiments were conducted, and the resulting products were separated into gas, liquid, and solid phases for thermal and chemical analyses. Selected biofuel samples were characterized using gas chromatography–mass spectrometry (GC–MS), elemental analysis, and thermogravimetric analysis (TGA). The biofuels contained complex mixtures of aliphatic hydrocarbons, aromatics, phenolics, carboxylic acids, esters, and nitrogen-containing compounds, classified into biogasoline, bio-jet fuel, biodiesel, and motor oil fractions. Optimal yields of biofuel, gas, and solid residues were 16.86%, 26.14%, and 40.43%, respectively, achieved at a 1:10 algae-to-water ratio, 30 min reaction time, and 250 °C. The biofuel composition comprised 11.37% gasoline, 29.41% kerosene, 9.71% diesel, with a heating value of 42.93 MJ·kg⁻¹. A higher fraction of gasoline, kerosene and diesel-range compounds enhances energy density and combustion stability, while lower oxygen and nitrogen content improves storage and fuel properties. Solid residues exhibited uniform physical properties but were unsuitable for high-grade biochar due to low carbon and high inorganic content. These findings demonstrate that HTL of municipal wastewater-grown microalgae is a viable route for sustainable biofuel production, integrating resource recovery with renewable energy generation, while systematically evaluating key operational parameters and characterizing the resulting biofuel for downstream applications.

Near infrared spectroscopy is a non-invasive and rapid technique to support the analysis of solid biofuels such as woodchip, which is considered as a suitable alternative for energy production, according to European goals for fossil fuel reduction. Chemical and physical properties of the woodchip influence combustion performance, so the most discriminant parameters such as moisture and ash content and gross calorific value were constantly monitored. The aim of this study was the development of prediction models for these three parameters with the use of a hand-held NIR spectrometer. Laboratory analyses were carried out to evaluate the quality of several Italian samples from a power plant, and PLS regression models were developed to test prediction accuracy. Moreover, the most relevant wavelengths were investigated to discriminate chemical compounds influence. Prediction models demonstrated the capacity of handheld MicroNIR instrument to be considered a practical tool for solid biofuel quality assessment. As a consequence, NIR spectroscopy improved real-time analysis and made it suitable for practical and industrial applications, as supported by the recent Italian standard UNI/TS 11765.

Purpose:  The aimed witch of this study was to verify the quality of the fuel sold by gas stations in the Amazonian towns of Bragança and Tracuateua (Brazil).   Method:  It were applied physicochemical analyses to verify the anhydrous ethyl alcohol content of samples of gasoline, as well as the specific mass of samples of diesel and gasoline.   Result and conclusion: Just over a quarter (26.47%) of the samples of gasoline collected in Bragança contained more ethanol than permitted by Brazilian law and were thus classified as in non-conformity. Three (75%) of the four gasoline samples from Tracuateua were non-conformity. In addition, 11.76% of the gasoline samples collected in Bragança were less dense at 20 °C than specified by the Brazilian legislation, and were thus considered as in non-conformity. Based on this same criterion, half (50%) of the gasoline samples collected in Tracuateua were also non-conformity. Diesel was the only fuel that presented no alteration in specific mass in either town.   Research implications: There is a lack of academic studies related to this serious problem in the surveyed sites. This pioneering study is of great importance because it will alert local authorities about the problem of marketing fuels that do not meet the current specifications of the Brazilian legislation and whose emission of gases causes atmospheric pollution besides being harmful to life and to the environment.   Originality/value: This study indicated that both types of gasoline (regular and premium) may be subject to adulteration in both Amazonian towns (Pará, Brazil). Objetivo: O objetivo deste estudo foi verificar a qualidade dos combustíveis comercializados pelos postos de abastecimento das cidades amazônicas de Bragança e Tracuateua (Brasil). Método: Foram aplicadas análises físico-químicas para verificar o teor de álcool etílico anidro de amostras de gasolina, bem como a massa específica de amostras de óleo diesel e gasolina. Resultados e conclusão: Pouco mais de um quarto (26,47%) das amostras de gasolina coletadas em Bragança continham mais etanol do que o permitido pela legislação brasileira e, portanto, foram classificadas como não conformes. Três (75%) das quatro amostras de gasolina de Tracuateua não estavam conformes. Além disso, 11,76% das amostras de gasolina coletadas em Bragança eram menos densas a 20 °C do que o especificado pela legislação brasileira, sendo assim consideradas não conformes. Com base neste mesmo critério, metade (50%) das amostras de gasolina coletadas em Tracuateua também apresentavam inconformidade. O diesel foi o único combustível que não apresentou alteração na massa específica em nenhum dos municípios. Implicações da pesquisa: Existe uma carência de estudos acadêmicos nos locais pesquisados em relação a este sério problema. Este estudo pioneiro é de grande importância porque alertará as autoridades locais sobre o problema da comercialização de combustíveis que não atendem às especificações vigentes da legislação brasileira e cuja emissão de gases causa poluição atmosférica além de ser prejudicial à vida e ao meio ambiente. Originalidade/valor: Este estudo indicou que ambos os tipos de gasolina (comum e premium) podem estar sujeitos a adulteração em ambas as cidades amazônicas (Pará, Brasil). Palavras-chave: análises físico-químicas, qualidade do combustível, álcool etílico anidro, não conformidade, adulteração.

Diesel fuel quality can be considered from many different points of view. Fuel producers, fuel consumers, and ecologists have their own ideas. In this paper, a sensor of diesel fuel quality type, and fuel condition that is oriented to the fuel’s consumers, is presented. The fuel quality types include premium, standard, and full bio-diesel classes. The fuel conditions include fuel fit for use and fuel degraded classes. The classes of fuel are connected with characteristics of engine operation. The presented sensor uses signal processing of an optoelectronic device monitoring fuel samples that are locally heated to the first step of boiling. Compared to previous works which consider diesel fuel quality sensing with disposable optrodes which use a more complex construction, the sensor now consists only of a capillary probe and advanced signal processing. The signal processing addresses automatic conversion of the data series to form a data pattern, estimates the measurement uncertainty, eliminates outlier data, and determines the fuel quality with an intelligent artificial neural network classifier. The sensor allows the quality classification of different unknown diesel fuel samples in less than a few minutes with the measurement costs of a single disposable capillary probe and two plugs.

Minimising dry matter losses during storage of comminuted forest fuels is desirable from both an economic and a sustainability perspective. This study examined fuel quality and amount of recovered energy during the storage of forest wood chips stored at full industrial scale at three locations, and the effect of sieving and covering piles with a water-resistant, vapour-permeable fabric. Sieving wood chips before storage, that is, reducing the number of fines smaller than 8 mm, reduced the cumulative dry matter losses to <2%, while cumulative dry matter losses after storage for 4–6 months using current practices, that is, unsieved and uncovered, reached 10.6%. The combined effect of storage management led to a value loss of 11.5%, while both covering and sieving led to lower losses, with the combination of sieving and covering giving a 1.3% value increase, and thus, increased storability.

Co-combustion is regarded as an effective means for high-efficiency utilization of low-quality fuels. However, low-quality fuel has problems such as low energy density and high water content. The fuel quality and blending performance can be further optimized by the pretreatment of low-quality fuel, for example, calorific value, hydrophobicity, and NO conversion rate. Based on the idea of co-upgradation, this study systematically investigates the effects of integrated upgrading on fuel quality and hydrophobicity under different conditions. In this study, lignite and wheat straw were selected as research objects. The co-upgrading experiments of wheat straw and lignite were conducted at reaction temperatures of 170 °C, 220 °C, and 270 °C in flue gas and air atmospheres with biomass blending ratios of 0%, 25%, 50%, 75%, and 100%. SEM (scanning electron microscopy) and nitrogen (N2) adsorption analyses showed that under low-temperature and low-oxygen conditions, organic components from biomass pyrolysis migrated in situ to cover the surface of lignite, resulting in a gradual smoothing of the fuel surface and a decrease in the specific surface area. Meanwhile, water reabsorption experiments and contact angle measurements showed that the equilibrium water holding capacity and water absorption capacity of the lifted fuels was weakened, and hydrophobicity was enhanced. Combustion kinetic parameters and pollutant release characteristics were investigated by thermogravimetric analysis (TGA) and isothermal combustion tests. It was found that co-upgradation could effectively reduce the reaction activation energy and NO conversion rate. Characterized by Raman spectroscopy (Raman) and X-ray photoelectron spectroscopy (XPS), in situ migration of organic components affected combustion reactivity by modulating changes in N-containing product precursors. The results showed that the extracted fuel with a 75% biomass blending ratio in the flue gas atmosphere exhibited the best overall performance at 220 °C, with optimal calorific value, combustion reactivity, and hydrophobicity. These findings may provide important theoretical foundations and practical guidance for the optimization of industrial-scale upgrading processes of low-quality fuels.

The aim of this study was to investigate the effect of changes in meteorological parameters and fuel composition on the emission rate of air pollutants in the vehicle fleet of the Tehran Metropolis. The results of this study can be used in management decisions to reduce the emission of air pollutants. In this paper, based on the international vehicle emission model and using mathematical equations, the effects of changing meteorological parameters and fuel composition on the emission of pollutants were modeled. The emission rates of CO, VOCs, and NOx pollutants were the most sensitive to the changes in meteorological parameters, respectively. Among all parameters studied in this research, the changes in sulfur level had the greatest effect on the emission of pollutants from the vehicle fleet of Tehran Metropolis. If the fuel was replaced with Euro 5 standard instead of Euro 3, the emission rates of CO, VOCs, NOx, PM, and SOx pollutants from the vehicle fleet of Tehran Metropolis would be reduced by 9%, 6%, 5%, 14%, and 90%, respectively. Managing and reducing the sources of production and emission of air pollution is one of the best ways to reduce the air pollution. In general, since the emission of pollutants from the fleet of Tehran Metropolis in the cold seasons of the year is greater than during hot seasons and the problem of air pollution is exacerbated by air stability, using Euro 5 fuel in cold seasons is one of the efficient ways to reduce the air pollution.

The automotive industry faces increasing challenges due to fuel scarcity and pollutant emissions, necessitating the implementation of strategies that optimize engine performance while minimizing the environmental impact. This study aimed to analyze the influence of oil viscosity and fuel quality on the engine performance and pollutant emissions in an internal combustion engine. A Response Surface Methodology (RSM)-based experimental design was employed. Three oil viscosity levels (SAE 5W-30, 10W-30, and 20W-50) and three fuel quality levels (87, 92, and 95 octane) were evaluated using a Chevrolet Grand Vitara 2.0L (General Motors, Quito, Ecuador) tested on a dynamometer. The oil grades were selected to represent a practical range of viscosities commonly used in commercial vehicles operating under local conditions. The results indicate that using lower-viscosity oil (SAE 5W-30) increased the engine power by up to 6.25% compared to when using SAE 20W-50. Additionally, using higher-octane fuel led to an average power increase of 1.49%, attributed to improved combustion stability and the ability to operate at a more advanced ignition timing without knocking. The emissions analysis revealed that high-viscosity oil at high RPMs increased CO2 emissions to 14.4% vol, whereas low-viscosity oil at low RPMs reduced CO2 emissions to 13.4% vol. Statistical analysis confirmed that the engine speed (RPM) was the most influential factor in emissions (F = 163.11 and p < 0.0001 for CO2; F = 247.02 and p < 0.0001 for NOx), while fuel quality also played a significant role. These findings suggest that optimizing the oil viscosity and selecting the appropriate fuel can enhance engine efficiency and reduce emissions, thereby contributing to the development of more sustainable automotive technologies. Future research should explore the use of ultra-low-viscosity lubricants (SAE 0W-20) and assess their long-term effects on engine wear.