Bioenergia - UB
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- Acid-Based Deep Eutectic Solvents for Structural Modification of Sulphite Pulp Cellulose: A Potential Route Toward Advanced MaterialsPublication . Moran, Guadalupe; Costa Trigo, Iván; Domínguez, José Manuel; Vilaseca, FabiolaABSTRACT: The transition toward renewable and environmentally responsible materials has intensified interest in cellulose-based systems for use in sustainable packaging applications. Although cellulose offers biocompatibility, structural versatility, and tuneable physicochemical properties, conventional modification routes rely on harsh chemicals and generate environmentally burdensome effluents. In this study, an efficient and a potentially green strategy for cellulose modification was developed using acid-based deep eutectic solvents (DES) composed of choline chloride and lactic, acetic, or citric acid at different molar ratios. Under mild conditions (110 degrees C, 4 h), DES pretreatment reduced glucan content in sulphite pulp from 99% to 79-93%, depending on the hydrogen bond donor (HBD), while suggesting an apparent increase in relative crystallinity, from approximately 82% to 90%, as estimated by the Segal method. FTIR, XRD, and morphological analyses revealed the disruption of the hydrogen bonding network, enhanced fibrillation, and residual DES-derived functional groups detectable by FTIR. Although DES pretreatment increased structural order, it also reduced enzymatic digestibility due to the higher proportion of crystalline domains. Overall, the results demonstrate that acidic DES constitutes a sustainable and recyclable medium capable of modulating cellulose structure and generating materials with enhanced physicochemical properties. These findings suggest that DES-modified cellulose could serve as a potential reinforcement platform for future biodegradable packaging and bioplastic formulations, enabling the development of high-performance, renewable, and environmentally compliant packaging materials.
- Advances of Hydrothermal Biomass Liquefaction Using Microalgae: Process Parameters and Biocrude Upgrading MethodsPublication . Martins, Marta; Fernandes, Marcelo Domingos; Rodrigues, Alda J.; Costa, Paula; Gírio, FranciscoABSTRACT: The ReFuelEU Aviation Regulation introduces mandatory targets for sustainable aviation fuels (SAF) from 2025 to 2050. However, hydrotreated esters and fatty acids (HEFA) technology based on waste oils alone is insufficient to meet targets beyond 2030, highlighting the need for alternative biocrude feedstocks to increase SAF production in the EU. Microalgae are promising feedstocks due to their biochemical composition and CO2-utilization potential, although their high moisture content and nitrogen and oxygen levels require energy-efficient conversion technologies. Hydrothermal liquefaction (HTL) is a suitable process for converting wet microalgal biomass into biocrude, with an optimal temperature window of approximately 300-330 degrees C and typical biocrude yields ranging from 20 to 70 wt%, depending on feedstock composition and operating conditions. However, microalgal HTL remains at TRL 5-7 and faces challenges related to the high heteroatom content of the resulting biocrude. Hydrodeoxygenation (HDO) is a key upgrading step for converting biocrude into drop-in aviation fuels and commonly operates at approximately 250-400 degrees C and 10-30 MPa H2 pressure. Nevertheless, few studies have addressed the HDO of microalgae-derived biocrude. This review examines microalgal HTL, pilot and demonstration facilities, biocrude yields and quality, and upgrading strategies for producing synthetic drop-in aviation biofuels.
- Applicability Assessment of a Microbial Proteolytic Fermentation Broth to Leather Processing and Protein Stain RemovalPublication . Lageiro, Maria Manuela; Moura, Maria João; Simões, Fernanda; Alvarenga, Nuno; Reis, AlbertoABSTRACT: Microbial proteases are fundamental towards the eco-sustainability of proteolysis at the industrial scale. A proteolytic broth was obtained from a bioreactor fermentation of a proteolytic Bacillus strain isolated from an industrial alkaline bath. Broth proteolytic activity was applied to leather tanning and to the removal of protein stains. The hide tanned with the microbial proteolytic fermentation broth showed better physical properties than the one tanned with commercial pancreatic proteases of the same activity (780 LVU). Proteinaceous stains on cotton fabric were removed more efficiently using the Bacillus proteolytic broth than water or a commercial detergent. Blood and egg yolk disappeared in less than 30 min. The removal of soya and English sauce stains was even faster. Broth proteolytic activity was characterised by caseinolytic (5200 LVU), collagenolytic (10.0 U mg-1), elastolytic (3.7 U mg-1), and keratinolytic (0.7 U mg-1) activities, which were compared with those of a commonly used commercial protease. Alkaline protease activity in the broth was demonstrated by a 20% increase in caseinolytic activity from pH 5 to 8. Besides the demonstrated applications in the leather and detergent industries, the produced alkaline microbial proteases can also be used in the treatment of proteinaceous wastes and effluents, offering potential environmental benefits reinforcing and impacting the bioeconomy.
- Benchmarking commercially available value-added fractions with potential for production via microalgae-based biorefineries: is it worth it?Publication . Ferreira, Flávio; Reis, Alberto; Ortigueira, Joana; Lopes, TiagoABSTRACT: The urgent need to mitigate climate change requires finding sustainable and efficient alternatives to fossil fuel-based materials. Biosequestration by microalgae has been suggested as a potential method for climate change mitigation due to its environmentally friendly nature and ability to produce high-value compounds. However, the large-scale application of microalgal biorefineries faces significant challenges, particularly in the harvest and processing stages, which are often costly and energy-intensive. This study aims to benchmark value-added fractions that can be produced via microalgae-based biorefineries against their commercially available counterparts. A systematic review was conducted using the Web of Science™ database to identify current commercial sources of proteins, lipids, polyunsaturated fatty acids and pigments, this study identified key sectors and applications for each fraction, as well as potential market competitors. The results highlight substantial cost differences across production systems, with traditional agricultural sources demonstrating lower CAPEX but greater environmental challenges. Meanwhile, microalgal systems, although associated with higher CAPEX, offer advantages such as reduced land and water dependency, potentially leading to long-term economic resilience and environmental sustainability. By pinpointing research trends, key sectors and optimization opportunities, this work offers valuable insights into the profitability and competitiveness of microalgal systems, providing a benchmark for future optimization efforts. The novelty of this research lies in its comprehensive comparison of microalgae-based and traditional production systems, establishing a clear benchmark for microalgal production and suggesting focus areas for enhancement.
- Bio-oil from hydrothermal liquefaction of microalgae cultivated in wastewater: An economic and life cycle approachPublication . Silva, Thiago; Junior, Maurino Magno de Jesus; Magalhães, Iara; Ananias, Marina Stefany; Saleme Aona de Paula Pereira, Alexia; Rodrigues, Fábio de Ávila; Delgado dos Reis, Alberto José; Calijuri, Maria LuciaABSTRACT: Although microalgae are a promising sustainable biofuel feedstock, their energy-intensive production and most environmental assessments rarely achieve the desired trade-off between productivity and sustainability. In this context, this study aims to evaluate the economic and environmental feasibility of producing bio-oil via hydrothermal liquefaction (HTL) of wastewater-grown microalgae at an industrial scale. Four scenarios varied production scale and steam source: sugarcane bagasse (SCB) in SC1 and SC3, liquefied petroleum gas (LPG) in SC2 and SC4. Each scenario processed microalgae at 300 degrees C for 30 min. Smaller-scale feedstock (1332.9 kg/h) in SC1 and SC2 produced 34.6 kg/h of bio-oil, while the larger feedstock (85,554.4 kg/h) in SC3 and SC4 yielded 2222.2 kg/h. Microalgae biomass cultivation costs dominated overall expenses (56-75 %). Economic analyses indicated minimum selling prices of 3.82-8.52 USD/kg, exceeding the average literature figure of 1.57 USD/kg. Life Cycle Assessment (LCA) showed SCB reduced fossil resource depletion by 14.97 % compared to LPG but increased emissions of nitrogen oxides, particulates, and toxic compounds, which are manageable via selective catalytic reduction and flue gas desulphurization. Cyclohexane as a solvent elevated human carcinogenic toxicity, greener alternatives could reduce toxicity but may cost more, requiring further cost analysis. Advancing this biorefinery route requires optimization of cultivation and processing costs, adoption of environmentally benign solvents, and implementation of emission control strategies to enable economically feasible and environmentally sustainable bio-oil production.
- Biogas Production from the Anaerobic Co-Digestion of Elephant Grass Juice and CattleWastewater: Batch and Semi-Continuous Performance in Anaerobic ReactorsPublication . da Silva, Guilherme Henrique; Otenio, Marcelo; Reis, Alberto; Martins, Marcio; Borges, Alisson; Lopes, Tiago; Renato, NataliaABSTRACT: Considering the limited information available on the use of elephant grass juice (EGJ) as a liquid co-substrate, this study aimed to evaluate its feasibility and biogas production potential for anaerobic co-digestion with dairy cattle wastewater (DCW), focusing on substrate ratios and reactor operating conditions. Initially, batch tests were conducted at different temperatures to evaluate the effects of varying substrate mixture ratios (EGJ/DCW). In the reactor with 20% EGJ/80% DCW at 39 °C, a biogas volume of 414.35 mL was generated, which was considerably higher than that in the test at 25 °C, where 258.7 mL was generated over the 30-day experimental period. Greater efficiency in organic matter removal and other analyzed parameters was also observed under these conditions. The best configuration was selected for the semi-continuous tests. To this end, an Upflow Anaerobic Sludge Blanket (UASB) reactor was operated with hydraulic retention times of 10, 6, 2, and 1 d and volumetric organic loading rates of 2.06, 3.39, 10.40, and 20.70 kg VS m−3 d−1, respectively. Volatile solids were removed by 29–58%, with biogas yields ranging from 0.78 to 2.28 m3 m−3 d−1 and a maximum CH4 concentration of 72% (v/v). The co-digestion of the analyzed agricultural waste substrates proved to be a promising approach for bioenergy recovery. These results provide useful guidelines for optimizing co-digestion systems, improving reactor performance, and waste treatment processes.
- Biopolymers Derived from Forest Biomass for the Sustainable Textile IndustryPublication . Dias, J. C.; Marques, Susana; Branco, Pedro C.; Rodrigues, Thomas; Torres, Cristiana A.V.; Freitas, Filomena; Evtuguin, Dmitry; Silva, CarlaABSTRACT: In line with environmental awareness movements and social concerns, the textile industry is prioritizing sustainability in its strategic planning, product decisions, and brand initiatives. The use of non-biodegradable materials, obtained from non-renewable sources, contributes heavily to environmental pollution throughout the textile production chain. As sustainable alternatives, considerable efforts are being made to incorporate biodegradable biopolymers derived from residual biomass, with reasonable production costs, to replace or reduce the use of synthetic petrochemical-based polymers. However, the commercial deployment of these biopolymers is dependent on high biomass availability and a cost-effective supply. Residual forest biomass, with lignocellulosic composition and seasonably available at low cost, constitutes an attractive renewable resource that might be used as raw material. Thus, this review aims at carrying out a comprehensive analysis of the existing literature on the use of residual forest biomass as a source of new biomaterials for the textile industry, identifying current gaps or problems. Three specific biopolymers are considered: lignin that is recovered from forest biomass, and the bacterial biopolymers poly(hydroxyalkanoates) (PHAs) and bacterial cellulose (BC), which can be produced from sugar-rich hydrolysates derived from the polysaccharide fractions of forest biomass. Lignin, PHA, and BC can find use in textile applications, for example, to develop fibers or technical textiles, thus replacing the currently used synthetic materials. This approach will considerably contribute to improving the sustainability of the textile industry by reducing the amount of non-biodegradable materials upon disposal of textiles, reducing their environmental impact. Moreover, the integration of residual forest biomass as renewable raw material to produce advanced biomaterials for the textile industry is consistent with the principles of the circular economy and the bioeconomy and offers potential for the development of innovative materials for this industry.
- Bridging gaps in biorefineries: The unexplored role of social dimension in life cycle assessment researchPublication . Ortigueira, Joana; Lopes, TiagoABSTRACT: This review examines the disregarded role of social dimensions in Life Cycle Assessment (LCA) within biorefinery implementation, addressing the question: "How can the inclusion of social factors in LCA improve sustainability assessments, and what are the implications of the limited Social Life Cycle Assessment (S-LCA) studies in biorefineries?" A systematic literature review was conducted using Web of ScienceTM, focusing on studies that integrate social dimensions in LCA. Bibliometric analysis using the bibliometrix R-package and VOSviewer identified key trends, influential papers, and research gaps. Results revealed a significant gap in incorporating social dimensions into biorefinery LCA, with most studies focusing primarily on environmental and economic impacts. Limited attention is given to social aspects such as community well-being, labor rights, and social equity. Case studies that included social factors demonstrated a more comprehensive sustainability assessment, emphasizing the importance of stakeholder engagement and social acceptability in biorefinery projects. This review highlights the need for standardized social indicators and methodologies to integrate social dimensions effectively. The lack of S-LCA in biorefinery implementation reflects a critical gap in sustainability assessments. Addressing this requires developing a unified S-LCA methodology, fostering interdisciplinary collaboration, and encouraging stakeholder participation to ensure diverse perspectives are considered. Ultimately, incorporating social dimensions is essential for achieving a more balanced and comprehensive evaluation of biorefinery sustainability.
- Catalytic Upgrading of Microalgae-Based Bio-Oils for Sustainable Jet Fuel ProductionPublication . França, Bruna Thomazinho; Paradela, Filipe; Martins, Marta; Fernando, Ana Luisa; Reis, Alberto; Costa, PaulaABSTRACT: The transition to sustainable energy systems has intensified the search for renewable alternatives to reduce greenhouse gas emissions and reliance on fossil fuels. In this context, microalgae have emerged as a promising third-generation feedstock for biofuel production due to their rapid development, high lipid content, and ability to grow in wastewater without competing with freshwater resources. In this study, the hydrotreatment of biocrudes derived from C. vulgaris, T. obliquus, and a mixed microalgal culture cultivated in domestic wastewater is investigated. Catalytic upgrading was applied using sulphided CoMo/Al2O3 (sCoMo) and Pt/Al2O3 catalysts. The results demonstrated that catalytic upgrading enhanced the upgraded bio-oils’ quality compared to non-catalysed reactions, confirming the crucial role of catalysts in improving bio-oil properties. Compared with the Pt catalyst, sCoMo produced higher yields of upgraded bio-oil, greater enrichment in carbon and hydrogen, and higher heating value (HHV), while effectively enhancing nitrogen and oxygen removal. However, when compared with the non-sulphided CoMo, the sulphiding treatment did not significantly improve denitrogenation and treated oil yields. The highest fraction of components within the jet fuel boiling range (37.7%) was obtained using a Pt catalyst, while the non-catalysed process yielded the lowest (26.6%). In this sense, catalytic upgrading of microalgae-based biocrude represents an important step towards the production of advanced and environmentally sustainable fuels.
- Clean production of microalgae high-value lipid fraction: Influence of different pretreatments on chemical and cytotoxic profiles of Chlorella vulgaris supercritical extracts and life cycle assessmentPublication . Vladic, Jelena; Radman, Sanja; Jerkovic, Igor; Besu, Irina; Speranza, Lais Galileu; Hala, Ahmad Furqan; Kovacevic, Strahinja; Perreira, Hugo; Gouveia, LuisaABSTRACT: Microalgae have emerged as a promising natural resource rich in bioactive compounds. Health-beneficial properties of microalgae, coupled with advantageous characteristics such as high biomass productivity, adaptability, robustness, and carbon dioxide mitigation, position them as a viable solution for global sustainable food production. This study explored clean and environmentally friendly processes to enhance the recovery of lipid bioactive fractions. Microwave (MW), enzymatic (ENZ), and ultrasound (US) pretreatments were applied to improve environmentally friendly extraction of lipid-based components using supercritical CO2. The effects of these pretreatments on extraction yield, chemical profiles, and cytotoxic properties of Chlorella vulgaris (Cv) and smooth C. vulgaris (sCv) extracts were investigated. Additionally, a Life Cycle Assessment (LCA) was conducted to evaluate environmental impacts. MW pretreatment achieved the highest yield increases, from 2.58 times (Cv) to 3.15 times (sCv). UHPLC-ESI-HRMS analysis revealed shifts in the distribution of pigments and derivatives caused by pretreatments, with ENZ extracts showing the most pronounced changes: pigments increased from 9.24% (control Cv) to 40.92% (Cv) and from 12.52% (control sCv) to 71.12% (sCv). Cv extracts exhibited greater activity against MDA-MB-453 cells, while sCv extracts from US pretreatment demonstrated the strongest effect on HeLa cells. The LCA indicated reduced environmental impacts of the pretreatment-enhanced processes up to 65% compared to the control. A scenario analysis was presented to show further possible impact reduction by recirculating the CO2 solvent and substituting the energy source. These findings provide valuable insights into sustainable and scalable green processes for recovering microalgal bioactive components.