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- 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.
- Development of a georeferenced database as a tool to improve circular material flows in lignocellulosic waste valorization [Poster]Publication . Silva, Tiago; Eusebio, Ana; Camocho, David; Alexandre, Jorge; Sousa Rocha, Cristina; Patinha, Pedro; Quental, Lídia; Gírio, Francisco; Moura, PatríciaABSTRACT: The Frontsh1p project aims to accelerate the development and implementation of cross-sector circular value chains through the creation of a multi-level toolkit that includes georeferenced data. This will facilitate the identification of the different stakeholders, their levels of interaction, regional distribution, and communication pathways, as well as the planning of new circular material flows for by-products and waste streams. The region of Łódzkie in Poland was selected for the development of this toolkit to establish guidelines, methodologies and technologies, based on information at the regional economic level, that can be easily replicated in different regions across Europe.
- Energy potential of elephant grass broth as biomass for biogas productionPublication . da Silva, Guilherme Henrique; Renato, Natalia dos Santos; Coelho, Felipe Ferreira; Donato, Thiago Paiva; Otenio, Marcelo; Machado, Juarez; Delgado dos Reis, Alberto JoséABSTRACT: The growing demand for clean energy has highlighted plant biomass as a valuable alternative, supporting sustainable development goals. Elephant grass (EG) is a promising feedstock due to its adaptability to diverse soils and climates, high dry matter production, and substantial energy yield. This study aimed to evaluate and characterize six selected EG genotypes (BRS Capia & ccedil;u, T_23.1, T_23.2, T_41.2, T_47.1, and T_51.5) based on their broth productivity and energy yield. Analysis of the broth's yield and physicochemical properties revealed that the by-product extracted from the biomass had a high residual energy value. Additionally, extracting the broth reduces the grass's biomass moisture content, enhancing its calorific value and improving the bagasse quality for combustion in boilers, thus optimizing energy production. This study demonstrates that the promising EG genotypes T_47.1, T_41.2, and T_23.1 presented relevant energy values ranging from 4248.12 to 4304.06 kcal kg- 1 of bagasse and thus are suitable for energy production through direct combustion. The extracted broth is a valuable residual energy source that can be utilized industrially after anaerobic digestion. Future research should focus on the environmental and economic effectiveness of EG broth as an energy source from waste and its potential for biogas production.
- Improving Carbon Fixation and Acetate Production from Syngas Fermentation: On-Demand Versus Continuous FeedingPublication . Pacheco, Marta; Silva, Tiago; silva, carla; Moura, PatríciaABSTRACT: Syngas fermentation is a promising carbon capture and utilization (CCU) technology for producing carboxylic acids while transforming low-cost waste gas into high-value products. This study evaluates the two bioreactor feeding strategies for synthesis gas (syngas) fermentation by Eubacterium callanderi (formerly Butyribacterium methylotrophicum) strain Marburg-on-demand feeding (ODF) and continuous feeding (CF)-with a synthetic syngas mixture of 23 vol% CO2, 29 vol% CO, 32 vol% H2, and 16 vol% CH4, mimicking the syngas from lignocellulosic gasification. The ODF assay achieved a maximum syngas consumption rate of 112 mL/h, yielding 24.1 g/L acids, namely 22.9 g/L acetate and 1.3 g/L butyrate. CF of syngas at 223 mL/h required more gas (62.9 L) to produce 22.7 g/L total acids, from which 19.0 g/L acetate and 3.7 g/L butyrate were achieved. The CF-specific production rate (gproduct/gdry_cell_weight/hour) reached 0.5 g/gDCW/h (acetate) and 0.17 g/gDCW/h (butyrate), outperforming ODF with 0.3 and 0.02 g/gDCW/h, respectively. ODF minimized gas wastage and enabled CH4 accumulation inside the bioreactor up to approximately 78 vol%, while CF led to CO2 accumulation, indicating a need for more efficient CO2 utilization strategies, such as sequential fermentations. This work highlights the critical impact of the two feeding options studied with regard to scaling up the carbon-efficient production of carboxylic acids, and indicates that both strategies can have potential applications. ODF is ideal for increasing carbon fixation and achieving, simultaneously, gas cleaning, while CF fermentations are better suited to maximizing the acid production rate.
- Industrial Off-Gas Fermentation for Acetic Acid Production: A Carbon Footprint Assessment in the Context of Energy TransitionPublication . Pacheco, Marta; Brac de la Perrière, Adrien; Moura, Patrícia; silva, carlaABSTRACT: Most industrial processes depend on heat, electricity, demineralized water, and chemical inputs, which themselves are produced through energy- and resource-intensive industrial activities. In this work, acetic acid (AA) production from syngas (CO, CO2, and H2) fermentation is explored and compared against a thermochemical fossil benchmark and other thermochemical/biological processes across four main Key Performance Indicators (KPI)—electricity use, heat use, water consumption, and carbon footprint (CF)—for the years 2023 and 2050 in Portugal and France. CF was evaluated through transparent and public inventories for all the processes involved in chemical production and utilities. Spreadsheet-traceable matrices for hotspot identification were also developed. The fossil benchmark, with all the necessary cascade processes, was 0.64 kg CO2-eq/kg AA, 1.53 kWh/kg AA, 22.02 MJ/kg AA, and 1.62 L water/kg AA for the Portuguese 2023 energy mix, with a reduction of 162% of the CO2-eq in the 2050 energy transition context. The results demonstrated that industrial practices would benefit greatly from the transition from fossil to renewable energy and from more sustainable chemical sources. For carbon-intensive sectors like steel or cement, the acetogenic syngas fermentation appears as a scalable bridge technology, converting the flue gas waste stream into marketable products and accelerating the transition towards a circular economy.
- Integrating social aspects in microalgal biorefineries: a Product Social Impact Life Cycle Assessment (PSILCA) approachPublication . Ortigueira, Joana; Lopes, Tiago; Reis, Alberto; Gírio, FranciscoABSTRACT: The ongoing climate change phenomenon requires the reduction of atmospheric CO2 concentrations. Microalgal biorefineries, which convert atmospheric CO2 into chemical energy, offer a viable alternative to fossil fuel-based industrial systems. This study assesses the social impacts of microalgal biorefineries using the Product Social Impact Life Cycle Assessment database approach, focusing on an industrial facility located in P & oacute;voa de Santa Iria, Vila Franca de Xira, Portugal. The foreground system involves the production of microalgae in cascade raceway systems, followed by their refinement into protein, lipid and carbohydrate fractions. Dedicated surveys were distributed to the local community to collect social data, which was then analyzed using the Product Social Impact Life Cycle Assessment (PSILCA) database and a newly designed evaluation schema. Preliminary data from approximately 300 valid responses indicated that the local community faces a medium risk of being unfamiliar with the concept of microalgae or its benefits but acknowledged the high probability of local economic benefits and job creation upon implementation. The study highlights a general lack of familiarity with microalgae among the local community, which could affect the acceptance of the biorefinery. Although the PSILCA approach identifies social hotspots effectively, reliance on generic data may not accurately represent the local context. The study underscores the need for enhanced information dissemination to improve community acceptance and support for microalgal biorefineries. Preliminary data collection and analysis highlight the potential for social benefits, but further research is required to address the identified limitations.
- Monitoring C. vulgaris Cultivations Grown on Winery Wastewater Using Flow CytometryPublication . Lopes da Silva, Teresa; Silva, Thiago; França, Bruna Thomazinho; Ribeiro, Belina; Reis, AlbertoABSTRACT: Winery wastewater (WWW), if released untreated, poses a serious environmental threat due to its high organic load. In this study, Chlorella vulgaris was cultivated in diluted WWW to assess its suitability as a culture medium. Two outdoor cultivation systems-a 270 L raceway and a 40 L bubble column-were operated over 33 days using synthetic medium (control) and WWW. A flow cytometry (FC) protocol was implemented to monitor key physiological parameters in near-real time, including cell concentration, membrane integrity, chlorophyll content, cell size, and internal complexity. At the end of cultivation, the bubble column yielded the highest cell concentrations: 2.85 x 106 cells/mL (control) and 2.30 x 106 cells/mL (WWW), though with lower proportions of intact cells (25% and 31%, respectively). Raceway cultures showed lower cell concentrations: 1.64 x 106 (control) and 1.54 x 106 cells/mL (WWW), but higher membrane integrity (76% and 36% for control and WWW cultures, respectively). On average, cells grown in the bubble column had a 22% larger radius than those in the raceway, favouring sedimentation. Heterotrophic cells were more abundant in WWW cultures, due to the presence of organic carbon, indicating its potential for use as animal feed. This study demonstrates that FC is a powerful, real-time tool for monitoring microalgae physiology and optimising cultivation in complex effluents like WWW.
- Production of sustainable aviation fuel precursors using the oleaginous yeast Rhodotorula toruloides PYCC 5615 cultivated on eucalyptus bark hydrolysatePublication . Saraiva Lopes da Silva, Maria Teresa; Dutra, Francisca; Gomes, Miguel; Costa, Paula; Paradela, Filipe; Ferreira, Frederico Castelo; Torres Faria, Nuno Ricardo; Mugica, Paula; Pinheiro, Helena M.; Sá-Correia, Isabel; Gírio, Francisco; Marques, SusanaABSTRACT: Sustainable aviation fuels (SAF) obtained from renewable sources of carbon can reduce carbon dioxide emissions and contribute for mitigating climate changes. In the present study, the yeast Rhodotorula toruloides PYCC 5615 was found to be highly promising for the bioconversion of eucalyptus bark hydrolysate and the accumulation of intracellular lipids which were further thermochemically processed to bioenergy intermediaries for SAF production. Two growth medium formulations were tested. Eucalyptus bark hydrolysate, obtained by steam explosion followed by enzymatic hydrolysis, was supplemented with yeast nitrogen base medium or with corn steep liquor and mineral medium. The latter produced the highest fatty acid content and productivity (30 % w/w and 0.11 g/ (L.h) respectively). Thereafter, the whole yeast biomass (WB) and the de-oiled biomass (DOB), obtained after lipid extraction, were processed into Bio-crude using a hydrothermal liquefaction (HTL) reactor, with a yield of approximate to 40 % (w/w). The two obtained Bio-crude fractions and the yeast lipids fraction (YL) were further upgraded by hydrodeoxygenation (HDO), to remove oxygen atoms and increase the hydrocarbon content, resulting in a Bio-crude composed of linear long-chain fatty acids suitable for processing to SAF. The best Bio-crude characteristics was observed for WB and YL fractions, with 34.8 % and 40.7 % of hydrocarbons, respectively. Both WB and YL hydrocarbons were composed of C15-C17 compounds. These results demonstrate the potential of an integrated process based on microbial oils from R. toruloides PYCC 5615 to produce SAF precursors from Eucalyptus bark residues, contributing for the sustainable jetfuel bioproduction process.
- Proteolytic Bacillus sp. Isolation and Identification from Tannery Alkaline BathsPublication . Lageiro, Maria Manuela; Simões, Fernanda; Alvarenga, Nuno; Delgado dos Reis, Alberto JoséABSTRACT: The application of microbial alkaline proteases holds significant potential for eco-sustainable industrial processes by reducing chemical usage and lowering the costs of effluent treatment. In the search for novel proteases with industrial relevance, several microbial strains were isolated from alkaline baths of the Portuguese tannery agroindustry. The most promising protease-producing strains were selected for identification and further study. Two isolates demonstrated the highest proteolytic activity, reaching 0.51 +/- 0.01 U mL-1 and 0.70 +/- 0.01 U mL-1 after 7.5 h of submerged cultivation in nutrient broth. Based on API biochemical tests, molecular biology techniques, and GC-FAME analysis of membrane lipids, the isolates were identified as Bacillus subtilis and incorporated into INIAV's collection of industrial microbial cultures as B. subtilis CCMI 1253 (BMR2) and B. subtilis CCMI 1254 (BMR1). The most promising protease producer, B. subtilis CCMI 1253 (BMR2), exhibited a maximum specific growth rate of 0.88 +/- 0.10 h-1. The proteases produced exhibited good extracellular proteolytic activity, with adaptability to industrial conditions, indicating their suitability for agroindustry applications such as leather making, detergent formulations and the treatment of effluents and protein residues. The results support the potential of microbial proteases as valuable tools in the bioeconomy and green chemistry.