Search Results (67)

This study assesses the aptitude of heterocystous cyanobacterial strain Dolichospermum spiroides MBDU 903 in integrated wastewater treatment and biofuel production at a laboratory scale. The efficiency of the strain was assessed based on pigment accumulation, growth kinetics, nutrient remediation efficiency, and biodiesel fuel quality. The results demonstrated that the biomass productivity of D. spiroides MBDU 903 ranged from 69.27 to 167.08 mg L⁻¹ day⁻¹ across various nutrient regimes, achieving a maximum lipid content of 31% (w/w). Cultivation in municipal wastewater with BG11+ (50% v/v) yielded the highest pigment production biomass. The physicochemical properties of the derived biodiesel were estimated from gas chromatography-derived fatty acid methyl ester (FAME) profiles. Furthermore, the biorefinery potential was explored as a proof-of-concept by fermenting the post-transesterification residual biomass with Saccharomyces cerevisiae, yielding 14.5 mg/g of bioethanol from the pretreated residue. While a 10 L pilot-scale trial was conducted, significant productivity drops suggest that further optimization is required to bridge the gap between laboratory results and practical application. This study provides a baseline evaluation of the dual-fuel potential of a heterocystous cyanobacterium under wastewater-integrated conditions. 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

Road transport decarbonization remains a strategic priority in the context of the global climate emergency. Between 2013 and 2024, most economic sectors in the European Union reduced emissions, whereas the transport and storage sector increased them by 14%, largely driven by road freight demand. This review provides an updated overview of the decarbonization status of the road transport fleet across all segments, with particular focus on heavy-duty freight, which remains 97.9% fossil-fuel dependent. It examines short- and medium-term decarbonization pathways for the existing fleet, highlighting liquid biofuels as an immediately deployable option where full electrification is constrained by technological and economic barriers. Among these options, fatty acid methyl ester (FAME) and hydrotreated vegetable oil (HVO) stand out due to their compatibility with current engines and fuel distribution infrastructure, but each presents specific limitations. Biodiesel raises concerns over long-term engine durability, while HVO requires further evidence on its impact on NO_x emissions and fuel lubricity. When these sustainable fuels are used with or without fossil diesel, there are still several unanswered questions. The emerging use of HVO/FAME blends is therefore discussed as a promising route to mitigate the drawbacks of each fuel, and a research agenda is proposed to support accelerated decarbonization of heavy-duty road freight in the EU. Full article

Growing pressure to decarbonize aviation has accelerated the search for alternative fuels to replace conventional Jet A-1 kerosene, with renewable biofuels attracting significant interest. While early demonstrations of kerosene–biofuel blends have been successful, they also introduce new operational challenges. This study examines the influence of low temperatures on blends of Jet A-1 and FAME (fatty acid methyl ester), focusing on clear point, cloud point, and density—parameters critical for maintaining reliable fuel flow in cold environments. The measurements demonstrate a consistent trend in which greater FAME fractions raise the clear point from 0.5 °C (0% FAME) to 5.8 °C (40% FAME) and the cloud point from −29.3 °C to −23.4 °C over the same range. Mixture density also increases with higher FAME content, from 810 kg·m⁻³ for pure Jet A-1 to 883 kg·m⁻³ for 100% FAME. Additionally, density rises as temperature decreases, with an increase of 6–16 kg·m⁻³ when the temperature drops from 8 °C to −8 °C. These shifts may impair stable fuel delivery to aircraft engine combustion chambers at low temperatures. The findings confirm that higher FAME content elevates clear and cloud point temperatures and increases density, indicating that such blends may be unsuitable for aviation use in polar and subpolar regions. Full article

Biofuels offer potential to mitigate climate change, increase energy security, and economically support farmers around the world. Licuri (Syagrus coronata) could be an important biofuel feedstock because its kernel (edible seed) has high energy content. This research investigates the optimal reaction conditions to convert fatty acids (FAs) and fatty acid methyl esters (FAMEs) (including licuri biodiesel) to hydrocarbons via deoxygenation in a trickle-bed reactor over granular Pd/C catalysts. Our results indicate that a 20 wt.% palmitic acid (PA) feed is optimum for continuous deoxygenation at 300 °C and 15 bar in 5% H₂/He because of decarboxylation inhibition at higher concentrations. Deoxygenation rates are higher for PA than for methyl palmitate (MP) because of the slow initial hydrogenolysis of the methoxy bond over Pd/C. The hydrocarbon product distributions from deoxygenation of licuri biodiesel were fully consistent with FA decarboxylation and decarbonylation. A lab-prepared 5 wt.% Pd/C catalyst with higher metal dispersion provided modestly higher hydrocarbon yields from licuri biodiesel than a commercial 1 wt.% Pd/C catalyst. Full article

The sustainable extraction of microalgal lipids represents a critical step toward the valorization of biomass for nutraceutical, pharmaceutical, and biofuel applications. In this study, a microwave-assisted extraction approach using a biocompatible ionic liquid (IL), [N_{1 1 2OH 2OH}][C₆H₁₁O₂], was investigated for lipid recovery from Chlorella vulgaris. Conventional methods (Soxhlet, Folch, and Bligh & Dyer) were first evaluated for benchmarking. Optimization of microwave power, extraction time, and algae-to-IL mass ratio demonstrated that a 1:8 (m/m) ratio under 5 min and 750 W microwave pretreatment achieved the highest lipid yield, with 10.61 ± 0.39% lipids recovered from the supernatant alone. Subsequent extraction of the pretreated biomass using an environmentally benign solvent mixture (ethyl acetate/ethanol, 1:1 v/v) raised the total lipid recovery to 14.29 ± 0.75%, surpassing Soxhlet extraction with chloroform/methanol (13.04 ± 0.16%). Importantly, the IL was efficiently recovered (≈85%) and reused without significant loss of performance or structural integrity, as confirmed by NMR, DSC, and FTIR analyses. The combined process yielded up to 42.56 ± 0.64 mg FAMEs/g algae, comparable to conventional Soxhlet extraction but with superior environmental compatibility. The relative distribution of FAMEs (in weight percent, wt%) was as follows: C16:2 trans 6.05%, C16:3 trans 13.99%, C16:1 cis 1.85%, C16:1 trans 0.82%, C16:0 16.72%, C18:2 cis 13.74%, C18:3 trans + C18:1 cis + C18:2 trans 26.91%, C18:1 trans 1.67% and C18:0 3.61%. These findings demonstrate that microwave-assisted extraction with choline-based ILs offers an efficient, recyclable, and greener alternative for lipid and fatty acid recovery from microalgae. Full article

The current paper investigated the potential of oleaginous fungus Rhizopus oryzae B97 for lipid accumulation under varying process variables. The fungal strain was isolated from bread mold and analyzed for its potential to grow on sludge with simultaneous production of microbial lipids. The sludge sample was sourced from the wastewater treatment plant located in Sector I-9, Islamabad. The effects of various process variables, such as pH, temperature, carbon and nitrogen sources, and shaking, on lipid accumulation, cell dry weight (CDW), chemical oxygen demand (COD), and volatile solids (VS) removal were investigated. It was found that glucose and yeast promoted the maximum lipid accumulation. At the same time, the fungal biomass reached its maximum value of up to 64% at 30 °C and at pH 4 (CDW: 28 g/L). These process conditions also improved the sludge treatment efficiency, achieving 68% COD and 55% VS removal in 168 h. FTIR analysis of the accumulated lipids indicated strong characteristic peaks of functional groups associated with fatty acids. The GC-MS analysis confirmed the production of essential FAMEs required in biodiesel production from the corresponding fatty acids, such as oleic acid, palmitic acid, stearic acid, and erucic acid. Operation in a continuous-shaking aerobic batch reactor (CSABR) system under optimum conditions further improved the process efficiency. Overall, the results indicated the competent potential of oleaginous fungus Rhizopus oryzae B97 for lipid-based biofuel production through fatty acid transesterification. Full article

Microalgae are photosynthetic microorganisms that could be used as potential microbial cell factories by directly converting CO₂ into valuable bioproducts and biofuels. This study aims to improve the production of biofuel from the isolated green alga Chlorella sp., in terms of an increase in its lipid content and its conversion to fatty acid methyl esters (FAMEs) when the cells are grown under the influence of phosphorus (P) limitation and heavy metal addition. The results show that the highest content of lipids, at 68.9%, was achieved within one day under 0% P with a 17 µM cobalt addition. Moreover, supplementation with a low Pb concentration increased cell growth even under P limitation, but under this condition, its lipid content was decreased after seven days of growth. The lipids of Chlorella sp. were transesterified to produce FAMEs. The overall biodiesel properties of the obtained FAMEs were of acceptable quality according to the standards (ASTM and EN). Additionally, the energy conversion from light energy to lipids was shown to be in the range of 10–16% conversion efficiency within seven days. Hence, the physiological modification of Chlorella sp. culture by phosphorus limitation coupled with the addition of a low concentration of heavy metals enabled the improvement of lipid content, with the subsequent transesterification resulting in the production of biodiesel with acceptable quality. Full article

Macauba is a versatile palm and has been explored in various sectors due to its ability to produce oils, proteins, energy, and biofuels. This paper presents the extraction, refining, and characterization of the macauba kernel oil, the synthesis of biodiesel, and an evaluation of the density and viscosity of its blends with mineral diesel, ranging from B15 to B20. Conversion was determined using the integral areas of the ¹H NMR spectrum for the FAME methyl ester (3.62, -CH₃) and FAME carbonyl (2.26, -COOCH₂). Predictions of the key inputs required for the extraction and degumming of the macauba kernel oil, as well as for the biodiesel production, are also presented. These results provide valuable insights into diesel-biodiesel blends exceeding 14% (vol.) of biodiesel, thereby contributing to the expansion of the biofuels industry. Full article

The present research features an experimental comparative design and the objective of this work was to determine the susceptibility to microbiological contamination in fatty acid methyl esters (FAMEs) and the FAME–water interface of residual and refined lard, large volume simulating storage conditions as fuel supply chain, and to identify the microorganisms developed. The plates were seeded according to ASTM E-1259 and the instructions provided by the manufacturer of the Bushnell Haas agar. Microbiological growth was observed at the FAME–water interface of FAME obtained from residual lard. Using the MALDI-TOF mass spectrometry technique, Pseudomonas aeruginosa and Streptomyces violaceoruber bacteria were identified in the residual lard FAMEs, with the latter being previously reported in FAMEs. The implications of microorganism development on the physicochemical quality of FAMEs are significant, as it leads to an increase in the acid index, which may negatively impact metals by inducing corrosion. The refined lard FAMEs did not show any development of microorganisms. The present research concluded that residual lard tends to be more prone to microbiological attack if the conditions of water and temperature affect microbial growth. The findings will contribute to the knowledge base for a safer introduction of FAMEs into the biofuel matrix. Full article

This study investigated the effect of KOH activation on biochar, with a focus on how porosity and potassium content influence microwave-assisted catalytic biodiesel production, using experimental design approaches. Activated biochar was synthesized from oat hull waste through KOH activation, followed by pyrolysis under controlled conditions. The biochar was characterized through chemical, morphological, and physical analyses, and its catalytic performance in converting used waste cooking oil (WCO) into biodiesel was evaluated using methanol as the acyl acceptor and microwave irradiation to optimize the reaction via experimental design. Results revealed that increasing the KOH/biomass ratio significantly enhanced the specific surface area (SSA) of the catalyst, achieving a maximum SSA of 637.28 m²/g under optimal pyrolysis conditions: 600 °C for 3 h with a KOH/biomass ratio of 2. A maximum fatty acid methyl ester (FAME) yield of 100% was achieved within 1 min of microwave-assisted reaction using an optimized catalyst dosage of 2.5%, a WCO/MeOH molar ratio of 1/12, and a reaction temperature of 150 °C, with the catalyst being successfully recycled across three cycles. An economic and energy evaluation estimated a catalyst production cost of USD 176.97/kg and a biodiesel production cost of USD 8.9/kg of FAMEs. This research provides a straightforward and cost-effective approach for biofuel production. Full article

As global energy demand continues to rise, microalgae have gained attention as a promising feedstock for biofuel production due to their environmental adaptability and renewable nature. This study investigated the growth performance and stress tolerance of Desmodesmus sp. KNUA231 under varying pH and salinity conditions to evaluate its potential as a biofuel candidate. The strain was cultivated under controlled laboratory conditions and exhibited stable growth across a broad pH range (4–10) and moderate salinity levels (up to 5 g L⁻¹ NaCl), indicating its resilience to diverse environmental conditions. Fatty acid methyl ester (FAME) analysis revealed that the biodiesel properties of Desmodesmus sp. KNUA231 comply with ASTM and EN standards in specific parameters, reinforcing its feasibility as a renewable biofuel feedstock. Additionally, its high calorific value (CV) suggests its potential as an energy-dense biomass source. The results of inductively coupled plasma mass spectrometry (ICP) analysis show that the soil is supplied with essential nutrients while minimizing heavy metal contamination, suggesting the possibility of biofertilizers. Although Desmodesmus sp. KNUA231 demonstrated promising characteristics for biofuel applications, further research is required to optimize large-scale cultivation and improve productivity for industrial applications. These findings highlight the potential of Desmodesmus sp. KNUA231 as a biofuel resource, particularly in non-optimal environmental conditions where pH and salinity fluctuations are common, contributing to the ongoing search for sustainable bioenergy solutions. Full article

Spent coffee grounds (SCGs) are an underutilized biomass resource with high potential for renewable energy and bioproduct synthesis. This study applies hydrothermal liquefaction to transform SCGs into high-quality biofuels and value-added biochemicals. Five experiments were conducted over a temperature range of 300 °C to 380 °C, highlighting significant temperature-dependent shifts in product composition. Notably, phenolic compounds peaked at 1180.1 mg/L at 300 °C before declining sharply, while chemical oxygen demand (COD) dropped to a minimum of 13,949.8 mg/L at 350 °C—a temperature that also maximized hydrochar yield (26%) and achieved a high heating value of 32.9 MJ/kg. Plasma chromatographic analyses showed the dynamic behavior of volatile fatty acids (VFAs) and fatty acid methyl esters (FAMEs); maximum levels of acetic (540.7 mg/L), formic (67.8 mg/L), and propionic acids (155.6 mg/L) were recorded at 300 °C, whereas FAMEs such as methyl butyrate, methyl hexanoate, methyl undecanoate, and methyl palmitate increased markedly at higher temperatures due to intensified carboxylation reactions. These results denote the potential of hydrothermal liquefaction to valorize SCGs for the production of biomolecules, expanding the conventional sustainable biofuel production pathways. Full article

Renewable energy sources, such as biofuels, represent promising alternatives to reduce dependence on fossil fuels and mitigate climate change. Their production through enzymatic hydrolysis has gained relevance by converting agro-industrial waste into fermentable sugars and residual oils, which are essential for the generation of bioethanol and biodiesel. The fungus Aspergillus stands out as a key source of enzymes, including cellulases, xylanases, amylases, and lipases, which are crucial for the breakdown of biomass and oils to produce bioethanol and fatty acid methyl esters (FAME). This review examines the current state of these technologies, highlighting the significance of Aspergillus in the conversion of energy-rich waste materials. While the process holds significant potential, it faces challenges such as the high costs associated with enzymatic production and final processing stages. Agro-industrial waste is proposed as an energy resource to support a circular economy, thereby eliminating reliance on non-renewable resources in these processes. Furthermore, advanced pretreatment technologies—including biological, physical, and physicochemical methods, as well as the use of ionic liquids—are explored to enhance process efficiency. Innovative technologies, such as genetic engineering of Aspergillus strains and enzyme encapsulation, promise to optimize sustainable biofuel production by addressing key challenges and advancing this technology towards large-scale implementation. Full article

Agriculture may hold the key to a sustainable future. By efficiently capturing atmospheric CO₂, we can simultaneously produce food, feed, biomass, and biofuels. For more eco-friendly soil processing practices, biofuels can replace diesel in agricultural machinery, significantly reducing the carbon footprint of crop production. Thus, biofuel production can be a sustainable solution for a future with a decreasing carbon footprint. This paper examines the possibility of replacing petroleum-based fuels with 100% biofuels to continue powering heavy-duty vehicles, where the use of electric vehicles is not the optimal solution. This study particularly focused on the operating scenario of heavy-duty engines under medium to high loads, typical of transport or soil processing in agriculture. Diesel was used as a benchmark, and each alternative, such as vegetable oil, methyl ester (B100), and methyl ester–ethanol blends (90B10E, 80B20E, and 70B30E), was tested individually. To find a sustainable fuel substitute, the goal was to identify a biofuel with a kinematic viscosity similar to that of diesel for a comparable spray process. Experimental results showed that an 80% methyl ester and 20% ethanol blend had a kinematic viscosity close to that of diesel. In addition to diesel, this blend resulted in a 48.6% reduction in exhaust gas opacity and a 6.54% lower specific fuel consumption (BSEC). The main aim of the tests was to find a 100% biofuel substitute without modifying the fuel injection systems of existing engines. Full article