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- A review of cleaning technologies for biomass-derived syngasPublication . J.R.C. Rey; A. Longo; B. Rijo; C.M. Pedrero; L.A.C. Tarelho; P.S.D. Brito; C. NobreBiomass gasification is a promising thermochemical conversion technology with substantial potential for sustainable global energy development. It can replace various fuels and chemicals derived from fossil fuels, producing a gas composed of CO, H2, and CH4 as targeted compounds and CO2, H2O, and N2 as adulterating compounds. However, the gas also contains impurities like tars, particulate matter, nitrogen and sulfur compounds, hydrogen halides, and trace metals, posing challenges for its use. Efficient gas purification is essential before application in internal combustion engines, gas turbines, or chemical processes. This paper provides a comprehensive survey of gas purification technologies arising from biomass gasification. Two main categories are explored: wet purification systems, notably using wet scrubbers, and dry purification systems, which are more appealing due to avoiding gas cooling and associated energy losses. Traditional particulate removal devices and modern catalysts for tar, acid gases, and trace metal elimination are examined in the dry purification category. Furthermore, this work describes alternative gasification concepts such as integrated gasification, supercritical-water gasification, and, chemical loop gasification, also addressing carbon capture technologies for syngas conversion. Finally, advances in syngas cleaning methods are revised and commercially available purification systems are presented and discussed, offering insights into current outcomes in this field
- A review of solid oxide cell technologies for power, fuel, and reversible energy storagePublication . Rijo, Bruna; Mateos-Pedrero, Cecilia; Copa Rey, José R.; Longo, Andrei; Brito, Paulo; Nobre, CatarinaSolid oxide cell (SOC) technologies, encompassing solid oxide fuel cells (SOFCs), solid oxide electrolysis cells (SOECs), and reversible solid oxide cells (rSOCs), are emerging as key components in the transition to sustainable energy systems due to their high operating efficiency, fuel flexibility, carbon–neutral fuel production potential, and compatibility with renewable energy sources. This work reviews current SOC technologies for renewable electricity generation and sustainable fuel production, examining their working principles and system configurations. Recent advances in materials, stack design, and control strategies are reviewed alongside significant challenges in material stability, dynamic response, electrode degradation, thermal management, and scalability. The paper highlights demonstration projects and provides an economic feasibility analysis of each SOC technology. Among electrolysis technologies, SOEC has higher capital expenditure (CAPEX) and operational expenditures (OPEX), but lower hydrogen production costs. A Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis reveals that SOEC possesses high hydrogen production efficiency, while SOFC offers great flexibility in fuel usage. However, it also points out that thermal stress and component degradation are significant challenges that need to be addressed. For rSOC, the analysis highlights the advantages of flexibility for twoway operation, along with concerns about stack cell degradation. The review also identifies innovation pathways needed to transition these systems from advanced prototypes to reliable components of decarbonised energy infrastructure, focusing on cost-effective materials development, electrode optimisation, and enhanced mathematical modelling
- Consumer-driven selection of low-emission vehicles for sustainable urban centers: An AHP-based approachPublication . Brito, Filipe Cardoso; Saba, Hugo; Panizio, Roberta Mota; Nobre, Catarina Pereira; Guarieiro, Lilian Lefol Nani; Ferreira, Cristiano Vasconcellos; Ferreira, Paulo; Santos, Alex Álisson Bandeira; Nascimento Filho, Aloísio S.In densely populated urban areas, air quality is one of the main concerns, affecting human health and the environment. In developing and emerging countries, an alternative method for reducing the effects of air pollution is to select vehicles with lower pollutant emissions, as a way of making these large centers more sustainable. Since the complete elimination of vehicle emissions is not possible in the short term. The aim of this work is conducting a selectivity study of low-emission vehicles to increase the proportion of less polluting vehicles by using a dynamic combination of technical information while simultaneously meeting consumer preferences. An adapted Analytic Hierarchy Process (AHP), a multi-criteria technique, was applied on secondary data on vehicle characteristics. The Brazilian Labeling Program was the main resource used in this research. The research innovatively promotes vehicle selection considering environmental aspects. In addition to being adaptable, dynamic, and interactive, it facilitates its use in different vehicle markets and contributes to policies for reducing pollutant emissions. Thus, the study presents a strategy to minimize vehicle emissions in urban centers until the energy transition is consolidated, especially in emerging countries like Brazi
- Do clean fuel and trade-openness reduce environmental degradation in China: evidence from asymmetric modelPublication . Shakeel, Muhammad; Nobre, CatarinaThis study investigates the relationship between economic growth, clean fuel utilization, trade, and environmental pollution. By focusing on the potential of clean fuels and trade in reducing pollution, this research aims to understand their role in promoting environmental sustainability in China from 1990 to 2020
- Impact of Quality Assurance on Higher Education Institution Performance: Differences Between Public and Private InstitutionsPublication . Serrano, Orlando; Gonzalez, Francisco Miranda; Mourato, JoaquimThis study aims to distinguish the Quality Assurance Effectiveness (QAE) and the performance of public and private Higher Education Institutions (HEIs), analysing the individual and combined effects of QAE on institutional performance. The originality of this study lies in three main aspects: first, it investigates the current state of QAE and HEIs performance, filling a gap in the literature by comparing them between public and private institutions; second, it addresses the lack of evidence on QAE as a predictor of HEIs performance, exploring its impact from the perspectives of faculty members; third, it applies Partial Least Squares Structural Equation Modelling (PLS-SEM) to data collected from Portuguese higher education institutions, revealing significant differences between public and private institutions in both Quality Assurance Effectiveness (QAE) and performance outcomes. The results indicate that management support, faculty engagement, and infrastructure quality are key factors for QAE, positively impacting the performance of HEIs, particularly in research and teaching/learning areas. This study contributes to the literature by providing quantitative evidence on the relationship between QAE and institutional performance. The findings also highlight that the adoption of quality practices by HEIs is influenced by external pressures and the need for legitimacy, as described by the neo-institutional theory. Management implications include strengthening leadership, consolidating quality culture, investing in infrastructure, and promoting faculty development
- Investigation of biochars derived from waste lignocellulosic biomass and insulation electric cables: A comprehensive TGA and Macro-TGA analysisPublication . Roberta Panizio; Carlos Castro; Nuno Pacheco; Ana Carolina Assis; Andrei Longo; Cândida Vilarinho; José Carlos Teixeira; et al.This study investigates the thermochemical decomposition and gasification performance of biochars produced from blends of waste lignocellulosic biomass and waste insulation electrical cables at varying temperatures. Characterization tests revealed changes, particularly in ash content (27.5 %–34 %) and elemental composition, with nitrogen content increasing notably in biochar samples compared to the original feedstock. Van Krevelen diagrams demonstrated a reduction in O/C and H/C ratios with increasing production temperature, resembling fossil fuels more closely. The thermogravimetric and the derived thermogravimetric profiles illustrated distinct degradation stages influenced by heating rates and production temperature. Macro-TGA tests provided insights into biomass residue behavior under gasification conditions, indicating higher reaction rates at elevated temperatures. Syngas analysis highlighted the impact of temperature and equivalence ratio on syngas composition, with higher temperatures favoring hydrogen-rich gas production. The observed trends in cold gas efficiency (42.61 %–50.40 %) and carbon conversion efficiency (45.83 %–50.40 %) underscore the significance of temperature control in maximizing gasification performance. Biochars produced at higher temperatures demonstrated superior gasification performance, suggesting potential for optimizing biochar production processes to enhance energy recovery and waste valorization
- Renewable Hydrogen from Biomass: Technological Pathways and Economic PerspectivesPublication . Rey, José Ramón Copa; Mateos-Pedrero, Cecilia; Longo, Andrei; Rijo, Bruna; Brito, Paulo; Ferreira, Paulo; Nobre, CatarinaHydrogen is undeniably one of the most promising options for producing energy with minimal environmental impact. However, current hydrogen production is still derived from carbonintensive processes relying on fossil fuels. Biomass is a sustainable and versatile resource that can be converted into hydrogen through biological and thermochemical pathways from a large variety of feedstocks and technologies. This work reviews and compares existing biomass-to-hydrogen technologies, focusing on their characteristics, maturity level, benefits, limitations, and techno-economic and lifecycle environmental impacts. Less-developed biological conversion methods are characterized by low efficiencies and hydrogen productivity. More mature thermochemical routes enable higher efficiencies and hydrogen yields. Overall, while thermochemical processes suit centralized largescale hydrogen production, biological pathways offer decentralized options, necessitating continued innovation for integration into future energy strategies. Some of these technologies, such as anaerobic digestion (best-case: 1.28 EUR/kgH2 ) and conventional gasification (best-case: 1.79 EUR/kgH2 ), emerge as promising, sustainable, and affordable alternatives for renewable hydrogen generation, offering production costs comparable to those of natural gas steam reforming (0.92–2.8 EUR/kgH2 ).
- Waste-Derived Chars: A Comprehensive ReviewPublication . Santa Margarida Santos; Margarida Gonçalves; Paulo Brito; Catarina NobreThe production of heterogeneous solid waste, such as municipal solid waste (MSW), construction and demolition waste (CDW), and industrial solid waste (ISW), has increased dramatically in recent decades, and its management is one of today’s biggest concerns. Using waste as a resource to produce value-added materials such as char is one of the most promising strategies for successful and sustainable waste management. Virtually any type of waste, through various thermochemical technologies, including torrefaction, pyrolysis, hydrothermal carbonization, and gasification, can produce char with potential material and energy applications. Pyrolysis is the most widespread technology, and there are more studies on producing and applying waste-derived char using this technology. The properties of waste-derived char seem to be influenced by the conversion technology and conditions, as well as by the composition of the source waste. A literature search indicated that the properties of waste-derived char are highly variable with the composition of the raw material, with carbon content in the range 8–77%, a higher heating value of 2.5–28.4 MJ/kg and a specific surface area of 0.7–12 m2/g. Depending on the properties of char derived from waste, there are greater or minor difficulties in applying it, with ash content, heavy metals, and polycyclic aromatic hydrocarbon (PAH) concentrations being some of its limiting properties. Therefore, this review attempts to compile relevant knowledge on the production of waste-derived char, focusing on heterogeneous solid waste, applied technologies, and practical application routes in the real world to create a supply chain, marketing, and use of waste-derived char. Some challenges and prospects for waste-derived char are also highlighted in this study.
- An Overview of the Thermochemical Valorization of Sewage Sludge: Principles and Current ChallengesPublication . Bruna Rijo; Catarina Nobre; Paulo Brito; Paulo FerreiraWith the increase in the world population and economic activity, the production of sewage sludge has grown, and its management has become an environmental problem. The most traditional method of managing sewage sludge is to dispose of it in landfills and on farmland. One way to valorize sewage sludge is to use thermochemical conversion processes to produce added-value products such as biochar, biofuels, and renewable gases. However, due to the high moisture content, thermochemical conversion using processes such as pyrolysis and traditional gasification involves multiple pre-treatment processes such as material drying. Hydrothermal thermochemical processes usually require high pressures, which pose many challenges to their application on a large scale. In this work, the advantages and disadvantages of the different existing thermochemical processes for the recovery of sewage sludge were analyzed, as well as the resulting industrial and environmental challenges. A SWOT analysis was carried out to assess the different thermochemical processes in terms of technical feasibility, economic viability, and broader market considerations
- Hydrogen from Waste GasificationPublication . Reinhard Rauch; Yohannes Kiros; Klas Engvall; Efthymios Kantarelis; Paulo Brito; Catarina Nobre; Santa Margarida Santos; Philipp A. GraefeHydrogen is a versatile energy vector for a plethora of applications; nevertheless, its production from waste/residues is often overlooked. Gasification and subsequent conversion of the raw synthesis gas to hydrogen are an attractive alternative to produce renewable hydrogen. In this paper, recent developments in R&D on waste gasification (municipal solid waste, tires, plastic waste) are summarised, and an overview about suitable gasification processes is given. A literature survey indicated that a broad span of hydrogen relates to productivity depending on the feedstock, ranging from 15 to 300 g H2/kg of feedstock. Suitable gas treatment (upgrading and separation) is also covered, presenting both direct and indirect (chemical looping) concepts. Hydrogen production via gasification offers a high productivity potential. However, regulations, like frame conditions or subsidies, are necessary to bring the technology into the market