Search Results (4,435)

The growing demand for sustainable, decentralized energy solutions has heightened interest in biomass-based technologies for rural applications. In Mexico, the expansion of oil palm cultivation in humid tropical regions has generated large quantities of agro-industrial residues that remain largely underutilized. This review analyzes the potential of oil palm residues as feedstock for small-scale thermochemical conversion, with a particular focus on gasifier stove technologies. Key residues, including empty fruit bunches, mesocarp fiber, and palm kernel shells, exhibit favorable physicochemical properties, including adequate calorific values and high volatile matter content, which support their suitability for gasification processes. However, challenges related to moisture content, ash composition, and tar formation may affect system performance and require appropriate pre-treatment and operational control. Gasifier stoves, especially fixed-bed and top-lit updraft (TLUD) configurations, represent a viable solution for decentralized energy generation in rural settings, improving combustion efficiency and reducing emissions compared to traditional biomass use. Despite their potential, current bioenergy policies in Mexico remain primarily focused on large-scale biofuel production, limiting the deployment of small-scale technologies. Overall, oil palm residues constitute a promising feedstock for gasifier stove applications, although their successful implementation depends on feedstock optimization, appropriate stove design, and the development of policy frameworks that support decentralized bioenergy systems. Full article

Syngas (synthesis gas) is a promising gaseous biofuel for small-scale power generation, but its highly variable composition, which depends on the biomass source and gasification process, poses challenges for engine optimization. This study investigates syngas–diesel dual-fuel combustion in an optically accessible engine using chemiluminescence imaging of OH*, CH*, and CH₂O* to characterize ignition and flame development. Three representative syngas compositions—Downdraft, Updraft, and Fluidbed—were examined. The Fluidbed composition exhibited the weakest OH* signal, approximately one-third of that observed for the other two, primarily due to its higher CO₂ dilution and lower H₂ content. Ignition delay trends were strongly correlated with dilution level: Downdraft and Updraft showed similar delays despite different H₂/CO ratios, while larger CO₂ shares led to longer delays and flattened heat-release rates. CH* and CH₂O* chemiluminescence showed better agreement with combustion timing than OH*. Methane enrichment enhanced flame propagation and reduced ignition delay, partially offsetting CO₂ dilution effects. Full article

Microbial lipids have emerged as a promising sustainable alternative to plant- and petroleum-derived oils, with applications spanning biofuels, oleochemicals, nutraceuticals, and specialty materials. Significant advances in metabolic engineering and strain development have increased lipid production capacity across diverse microorganisms. Numerous reviews have summarized the biological and metabolic advances in this field, highlighting significant progress in metabolic engineering and strain development that has increased lipid production capacity across diverse microorganisms. However, translating these gains into economically viable industrial processes remains a major challenge. This review examines process engineering strategies for microbial lipid production across the full bioprocessing pipeline, from laboratory-scale strain evolution to industrial-scale operation. We discuss recent developments in adaptive laboratory evolution, systems-guided strain optimization, and robustness engineering, emphasizing their implications for process performance. Key bioprocess parameters—including substrate selection, nutrient limitation strategies, reactor design, oxygen transfer, and process control—are critically evaluated for their impact on lipid yield, productivity, and scalability. Furthermore, downstream processing considerations and techno-economic constraints are analyzed in the context of large-scale implementation. By integrating strain-level innovations with process engineering principles, this review highlights current bottlenecks, emerging solutions, and future directions for achieving efficient and scalable microbial lipid biomanufacturing. Full article

Organic Rankine Cycles (ORCs) are widely recognized as an effective solution for Waste heat recovery (WHR). However, the design and optimization of these systems must address the tradeoff between computational efficiency and the need to capture complex component behavior. This requires moving beyond purely energetic 0D modeling approaches to account for constructional, spatial, and operational constraints. This work presents a novel modeling framework with a specific focus on the expansion device. Radial inflow turbine stages are selected for their capability to achieve high pressure ratios while maintaining compactness and high efficiency. Heat exchangers follow a generic one-dimensional counterflow configuration, with a shell-and-tube geometry adopted for sizing purposes. The turbine stages are modeled by resolving several internal sections in order to capture local thermofluid dynamic conditions. The framework predicts turbine efficiency and incorporates a newly developed formulation for shock-induced losses, improving performance prediction under trans-sonic flow conditions. After validation against experimental data, the model is applied to a WHR system integrated with an internal combustion engine fueled by biofuels. The results highlight the existence of optimal operating conditions arising from competing physical mechanisms. The analysis also shows the transition from single-stage to two-stage turbine configurations at high pressure ratios and emphasizes the role of real gas effects in determining stage performance and optimal expansion distribution. The results of simulations carried out for three different working fluids (ethanol, toluene, and R1234ze(E)) highlight that the available mechanical power ranges from 10 to 22 kW for single-stage turbine configurations and from 24 to 36 kW for two-stage configurations, with total system volumes varying between approximately 600 and 9000 L. Among the working fluids considered here, ethanol provides the best overall performance for the present case study. Overall, the proposed approach provides a reliable and computationally efficient tool for the preliminary design and optimization of ORC-based WHR systems. Full article

Lignocellulosic biomass represents an abundant and renewable carbon source, and its valorization through microalgal cultivation offers a sustainable route to resource-efficient bioprocessing. This study examined the effects of various carbon and nitrogen sources on the growth and lipid metabolism of Desmodesmus subspicatus, with a focus on ryegrass enzymatic hydrolysates as an alternative carbon source. Cultures were supplied with glucose, xylose, or arabinose at different concentrations, along with sodium nitrate or yeast extract, under different carbon-to-nitrogen ratios. Additionally, the impacts of alkaline- and acid-pretreated enzymatic ryegrass hydrolysates were evaluated. Growth was assessed by optical density and gravimetric analysis, and fatty acid profiles by gas chromatography. Glucose supplementation enhanced lipid accumulation, yielding fatty acid profiles dominated by C16 and C18 fatty acids, which are favorable for the quality of the produced biodiesel. Nitrogen limitation further promoted lipid accumulation; cultures supplied with sodium nitrate achieved higher total lipid content, while yeast extract favored greater proportions of PUFAs. Alkaline-pretreated ryegrass hydrolysate supported dose-dependent biomass formation reaching approximately 12 g L⁻¹ at 50%, whereas the acid-pretreated hydrolysate exhibited inhibitory effects at the same concentration. Scale-up in a 1 L photobioreactor yielded lower biomass but higher lipid content with a fatty acid profile shifted to SFA. These results support ryegrass as a viable alternative carbon source and highlight cultivation parameters that influence growth and lipid quality relevant for biofuel applications. Full article

Microalgae and cyanobacteria are photosynthetic microorganisms capable of removing nutrients from eutrophic waters and producing biomass. Therefore, the aim of this study was to evaluate the bioremediation performance of three microalgae and one cyanobacterium native to Lake Xochimilco and to assess their potential for biofuel production (biodiesel and biogas) from biomass generated. In photobioreactors, ammonium (96.61–97.06%), nitrate (82.4–100%), and phosphate (83.95–89.71%) were effectively removed from the lake water. The specific growth rates ranged from 0.041 to 0.144 d⁻¹ and biomass productivities from 0.016 to 0.049 g L⁻¹ d⁻¹, with high biomass yield on the substrate. The estimated CO₂ fixation rates ranged from 0.024 to 0.092 g L⁻¹ d⁻¹. Chlorella sp. achieved the highest yield of fatty acid methyl esters (FAMEs) with 91.24% of the extracted lipids. Overall, saturated FAMEs were predominant in the biodiesel; however, the presence of monounsaturated FAMEs such as methyl palmitoleate and methyl oleate enhances their fluidity and oxidative stability. Synechocystis sp. and Chlorella sp. produced the most biogas using biomass after lipid extraction, at 429.5 L kg⁻¹ VS and 404.9 L kg⁻¹ VS, respectively, with over 60% biomethane. These strains represent a sustainable and promising possibility for water bioremediation and generating biofuels. Full article

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. Full article

Lignocellulose represents an abundant repository of renewable carbon. Derived from various plant sources, it holds tremendous potential as a renewable and sustainable feedstock for the production of valuable chemicals and fuels. However, its solid fermentable compounds, cellulose and hemicellulose, are embedded within complex lignin structures and are therefore poorly accessible to microbial conversion. This paper describes an artificial rumen reactor (ARR) that uses anaerobic microbes from the cattle rumen to increase the release of fermentable carbon from recalcitrant biomass. We outline the development of an ARR for the efficient conversion of lignocellulosic grass into volatile fatty acids (VFAs), which are valuable precursors for the production of a range of bioproducts, including biofuels, biomaterials, and biochemicals. The ARR, a 4-L bioreactor equipped with a ceramic filtration unit, has been optimised and was operated for extended periods of continuous VFA production. Across distinct short- and long-term observation periods, and independent of the cow from which the rumen microbes originated, the bioreactor demonstrated the ability to sustain VFA production, indicating robustness and stability. At an input of 60–80 g dry grass d⁻¹, the system produced approximately 6 mol VFA per kg of dry matter input (DMI). The decoupling of the Solid Retention Time (SRT; 10 days) and the Liquid Retention Time (LRT; 0.5 days) prevented inhibition of the VFA production. The VFA profile was dominated by acetic and propionic acids, comprising 68% and 19%, respectively, with butyric acid and minor VFAs accounting for the remainder. The application of low oxygen levels (<10%) in the reactor via limited aeration did not affect the VFA yield or its profile. Full article

Climate change-induced variability in temperature and precipitation increasingly constrains crop production on sandy-textured soils with low water-holding capacity and limited nutrient retention. Such soils, classified as Brunic Arenosols, are widespread across the temperate climate zone of Central Europe, particularly in post-glacial landscapes, where they constitute a significant proportion of marginal agricultural lands. This study evaluated the relative influence of growing-season weather conditions and selected soil physicochemical properties on the yield of Camelina sativa and Brassica carinata cultivated under low-input management on Brunic Arenosols in northwestern Poland during the 2023 season. Yields varied markedly among sites. Camelina sativa produced yields from 300 to 930 kg ha⁻¹, with the highest yield recorded at the site characterized by higher BS and phosphorus availability. Brassica carinata produced yields from 0 to 370 kg ha⁻¹, including complete yield loss at one location due to severe pathogen infestation. Spearman’s correlation analysis revealed that temperature was a key determinant for both crops (r = 0.77 for C. sativa; r = 0.82 for B. carinata). For Camelina sativa, yield was strongly associated with BS (r = 0.80) and available P (r = 0.69), whereas Brassica carinata was more sensitive to climatic variability, showing a negative relationship with precipitation (r = −0.63). The results indicate species-specific responses to soil fertility and weather conditions under water- and nutrient-limited conditions typical of Central European sandy soils. While Camelina sativa performance was more closely linked to soil chemical status, Brassica carinata appeared predominantly climate-driven. These findings highlight the broader relevance of the study for temperate regions of Central Europe and support the integration of soil fertility management with climate-adaptive strategies when introducing alternative oilseed crops to marginal lands. Full article

Docosahexaenoic acid (DHA) is an essential ω-3 polyunsaturated fatty acid (PUFA) with high nutritional and pharmaceutical value. The marine protist Aurantiochytrium is a promising industrial DHA producer; however, its DHA biosynthesis via the PUFA synthase pathway co-produces ω-6 docosapentaenoic acid (DPA), limiting DHA purity. Here, we introduced an ω-3 desaturase from Phytophthora infestans (Pin-O3D) into Aurantiochytrium sp. SD116. Functional validation in an Escherichia coli system co-expressing the native PUFA synthase confirmed that Pin-O3D converts DPA to DHA, shifting the DHA/DPA ratio from 1:1 to 2:1. Pin-O3D was then integrated into the fatty acid synthase (FAS) locus, simultaneously attenuating FAS activity and enabling heterologous gene expression. The engineered strain ΔFAS-Pin-O3D exhibited significantly (p < 0.0001 in t-test) increased DHA content (55.2% of total fatty acids) and DHA/DPA ratio (5.91) in shake flasks, with no negative impact on biomass or lipid accumulation. Fed-batch fermentation confirmed the scalability of this strategy, achieving a >20% increase in DHA/DPA ratio. This study demonstrates that combining heterologous ω-3 desaturase expression with FAS attenuation is an effective approach for optimizing PUFA profiles in Aurantiochytrium. Full article

Municipal wastewater represents an underutilized secondary biomass resource rich in organic carbon and nutrients that can be valorized through biotechnological conversion. In this study, we developed an integrated multi-microbial biorefinery platform to transform municipal wastewater into value-added biofuel via sequential bacterial treatment, microalgal biomass generation, and fungal-assisted harvesting. Wastewater was first pretreated with Bacillus subtilis to enzymatically hydrolyze complex organic substrates and enrich the medium with bioactive metabolites, including auxins and gibberellins. The conditioned wastewater was subsequently used to cultivate Chlorella vulgaris, followed by biomass recovery using Trichoderma viride pellets as a sustainable bioflocculant. The integrated consortium significantly enhanced nutrient removal efficiency and promoted algal biomass accumulation, lipid enrichment, and biodiesel productivity compared to monoculture controls. Elevated hydrolytic enzyme activities (cellulase, protease, and amylases) facilitated organic matter conversion into bioavailable substrates, while increased phytohormone levels stimulated algal growth and lipid biosynthesis. Additionally, fungal bioflocculation substantially improved biomass recovery efficiency, reducing the need for energy-intensive harvesting technologies. This work highlights the potential of a biotechnology-driven approach for integrating wastewater remediation with biofuel production. By integrating microbial metabolism, enzymatic transformation, and sustainable separation processes, the proposed biorefinery system suggests a potentially low-carbon approach for simultaneous environmental remediation and biomass valorization, although further life cycle and energy balance analyses are required to validate this aspect. Full article

Nano–bio hybrid catalysts have emerged as a promising platform for sustainable energy conversion by integrating the high selectivity of enzymes with the structural robustness and conductivity of nanomaterials. In recent years, the growing demand for clean energy technologies has driven the development of biohybrid systems capable of efficient electron transfer, enhanced catalytic activity, and improved operational stability. This review comprehensively discusses the design principles, mechanistic foundations, and performance metrics of enzyme–nanomaterial interfaces for energy-related applications. We first outline the fundamentals of enzymatic redox catalysis and the limitations of free enzymes in practical systems. Subsequently, we examine the functional roles of nanomaterials including carbon-based materials, metal and metal oxide nanoparticles, and two-dimensional platforms such as MXenes in facilitating enzyme immobilization and promoting direct or mediated electron transfer. Special emphasis is placed on engineering strategies at the bio–nano interface, including immobilization techniques, surface functionalization, and structural tuning to optimize catalytic efficiency. The review further highlights representative hybrid systems based on laccase, glucose oxidase, peroxidase, and hydrogenase enzymes, and evaluates their applications in biofuel cells, solar–bio hybrid systems, green oxidation reactions, and self-powered biosystems. Stability challenges, deactivation mechanisms, and enhancement strategies such as polymer coatings, cross-linking, and nanoconfinement are critically analyzed. Finally, emerging directions including artificial enzymes, AI-guided catalyst design, and self-healing bioelectrodes are discussed to provide a forward-looking perspective on next-generation sustainable bioelectrocatalytic systems. Full article

The development of modern society has intensified fossil fuel consumption, resulting in the depletion of oil resources and rising greenhouse gas emissions. In this context, the promotion of renewable alternatives in the transport sector has become essential, with Hydrotreated Vegetable Oil (HVO) emerging as a promising transitional fuel due to its compatibility with conventional diesel engines. To ensure proper engine operation and performance, the physical properties and chemical structure of HVO must be accurately characterized. Gas chromatography is commonly used for this purpose. While dedicated gas chromatography methods for HVO are available on specialized equipment, this study proposes a chromatographic method applicable to conventional gas chromatograph systems equipped with a flame ionization detector, enabling the analysis of HVO using commonly available laboratory equipment. The method was developed using commercially available HVO and pure n-alkanes (C₅–C₁₈) as reference compounds for component identification. The proposed approach enabled the estimation of carbon and hydrogen atom numbers in the analyzed fuel fractions and the determination of the stoichiometric air. The calculated values show good agreement with the literature data, confirming the reliability and applicability of the proposed boiling-point-based chromatographic method. Full article

Biodiesel is a sustainable and promising alternative energy source produced from renewable raw materials using various methods. One effective approach is simultaneous esterification and transesterification, which relies on suitable catalysts that can be either homogeneous or heterogeneous. Homogeneous catalysts (acid or base) offer high activity but are corrosive and difficult to recover, necessitating energy-intensive processes such as aqueous quenching and neutralization, which can lead to soap formation and stable emulsions. By comparison, heterogeneous catalytic systems overcome many of these challenges due to their ease of recovery, reusability, and simplified product separation, which collectively enhance economic viability and environmental sustainability. This review highlights recent progress in the application of zeolite-based solid catalysts for biodiesel synthesis, with particular emphasis on their use in converting waste cooking oil and other low-cost feedstocks, including non-edible oils, non-food biomass sources, algal resources, and genetically engineered microorganisms. Key factors such as catalytic activity, selectivity, catalyst loading, and reusability are discussed, highlighting the advantages of zeolites due to their unique crystal structure, high thermal stability, and ease of product recovery. Overall, this review underscores the challenges and opportunities in zeolite-based catalysis to provide a comprehensive understanding of its potential to enhance the efficiency and scalability of biodiesel production. Full article

Diesel engines have evolved significantly over the last century while maintaining core qualities such as reliability, durability, and fuel economy. Currently, the viability of their continued use is under discussion, mainly due to the environmental impact of polluting emissions from conventional fossil fuels. An advantage of these engines is their high fuel flexibility, which includes the capability to operate with pure vegetable oils. Following the established limitations of large-scale conventional biodiesel use, this perspective explores the implementation of straight vegetable oils (SVOs) blended with low-viscosity, low-octane (LVLC) oxygenated solvents to address climate targets such as the “Fit for 55” agenda. The discussion examines the potential of these advanced biofuels to contribute to the 2050 carbon neutrality goals while addressing the technical and economic requirements of the transport sector. Full article