Waste Biorefinery Technologies for Accelerating Sustainable Energy Processes

A special issue of Reactions (ISSN 2624-781X).

Deadline for manuscript submissions: 31 August 2024 | Viewed by 9868

Special Issue Editors


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Center of Physics and Engineering of Advanced Materials (CeFEMA), Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal
Interests: low-temperature fuel cells; alkaline water electrolysis; electrochemical wastewater treatment
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VALORIZA—Research Center for Endogenous Resource Valorization, Campus Politécnico, 10, 7300-555 Portalegre, Portugal
Interests: bioenergy; biofuels; biochar; pyrolysis; gasification; refuse derived fuels; biomass wastes
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VALORIZA—Researche Center for Endogenous Resources Valorization, Polytecnic Institute of Portalegre Campus Politécnico, 10, 7300-555 Portalegre, Portugal
Interests: bioenergy; thermal gasification; waste valorization; electrolysis; corrosion
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Mechanical Engineering and Resource Sustainability Center, Faculty of Science and Technology, NOVA University of Lisbon, 2829-516 Caparica, Portugal
Interests: biofuels; biomass; thermochemical processes; waste valorization; microalgae; biorefineries
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

By 2030, the bio-based economy is expected to have grown significantly in Europe. One of the pillars of this bioeconomy is the concept of biorefinery, the sustainable processing of several kinds of waste and biomass into a spectrum of marketable products and energy. While many research efforts have been conducted toward understanding, modelling, and designing conversion processes that can sustain a true circular economy, this knowledge is fragmented and unevenly distributed across Europe. Several countries lack appropriate policies and public engagement to endeavour the challenges ahead. Harmonisation must start with robust knowledge and the ability to cover the whole value chain, from source materials to marketable products. That is the mission of COST Action CA20127—Waste biorefinery technologies for accelerating sustainable energy processes (WIRE).

The WIRE COST Action is broadly organised into 4 key Working Groups (WG) that bring together experts from academia, industry, and technology transfer organisations and cover (1) raw materials, (2) biorefinery conversion technologies, (3) biorefinery applications, and (4) communication and dissemination. These WG will proactively contribute to promoting (i) the circular economy, (ii) bioenergy and bioeconomy, (iii) research and innovation in the field, (iv) applied research towards biorefineries’ implementation, and (v) EU-wide harmonisation of the scientific and technical approaches, thus facilitating engagement with policy makers and industry, paving the ground for a more effective link with the relevant industry sectors and attracting their interest.

This Special Issue in Reactions aims to publish some of the outcomes of WIRE COST Action and other research works that fall within the topic of the issue. We hope that this issue can positively influence the future landscape in science and technology in the critical field of waste biorefineries.

Dr. Diogo M.F. Santos
Dr. Catarina Nobre
Prof. Dr. Paulo Brito
Prof. Dr. Margarida Gonçalves
Guest Editors

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Published Papers (6 papers)

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Research

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20 pages, 7700 KiB  
Article
Sewage Sludge Plasma Gasification: Characterization and Experimental Rig Design
by Nuno Pacheco, André Ribeiro, Filinto Oliveira, Filipe Pereira, L. Marques, José C. Teixeira, Cândida Vilarinho and Flavia V. Barbosa
Reactions 2024, 5(2), 285-304; https://doi.org/10.3390/reactions5020014 - 16 Apr 2024
Viewed by 899
Abstract
The treatment of wastewater worldwide generates substantial quantities of sewage sludge (SS), prompting concerns about its environmental impact. Various approaches have been explored for SS reuse, with energy production emerging as a viable solution. This study focuses on harnessing energy from domestic wastewater [...] Read more.
The treatment of wastewater worldwide generates substantial quantities of sewage sludge (SS), prompting concerns about its environmental impact. Various approaches have been explored for SS reuse, with energy production emerging as a viable solution. This study focuses on harnessing energy from domestic wastewater treatment (WWT) sewage sludge through plasma gasification. Effective syngas production hinges on precise equipment design which, in turn, depends on the detailed feedstock used for characterization. Key components of plasma gasification include the plasma torch, reactor, heat exchanger, scrubber, and cyclone, enabling the generation of inert slag for landfill disposal and to ensure clean syngas. Designing these components entails considerations of sludge composition, calorific power, thermal conductivity, ash diameter, and fusibility properties, among other parameters. Accordingly, this work entails the development of an experimental setup for the plasma gasification of sewage sludge, taking into account a comprehensive sludge characterization. The experimental findings reveal that domestic WWT sewage sludge with 40% humidity exhibits a low thermal conductivity of approximately 0.392 W/mK and a calorific value of LHV = 20.78 MJ/kg. Also, the relatively low ash content (17%) renders this raw material advantageous for plasma gasification processes. The integration of a detailed sludge characterization into the equipment design lays the foundation for efficient syngas production. This study aims to contribute to advancing sustainable waste-to-energy technologies, namely plasma gasification, by leveraging sewage sludge as a valuable resource for syngas production. Full article
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21 pages, 3960 KiB  
Article
Dry and Hydrothermal Co-Carbonization of Mixed Refuse-Derived Fuel (RDF) for Solid Fuel Production
by Andrei Longo, Octávio Alves, Ali Umut Sen, Catarina Nobre, Paulo Brito and Margarida Gonçalves
Reactions 2024, 5(1), 77-97; https://doi.org/10.3390/reactions5010003 - 16 Jan 2024
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Abstract
The present study aims to test several conditions of the thermochemical pretreatment of torrefaction and carbonization to improve the physical and combustible properties of the Portuguese RDF. Therefore, two different types of RDF were submitted alone or mixed in 25%, 50%, and 75% [...] Read more.
The present study aims to test several conditions of the thermochemical pretreatment of torrefaction and carbonization to improve the physical and combustible properties of the Portuguese RDF. Therefore, two different types of RDF were submitted alone or mixed in 25%, 50%, and 75% proportions to dry carbonization processes in a range of temperatures between 250 to 350 °C and residence time between 15 and 60 min. Hydrothermal carbonization was also carried out with RDF samples and their 50% mixture at temperatures of 250 and 300 °C for 30 min. The properties of the 51 chars and hydrochars produced were analyzed. Mass yield, apparent density, proximate and elemental analysis, ash mineral composition, and higher heating value (HHV), among others, were determined to evaluate the combustion behavior improvement of the chars. The results show that after carbonization, the homogeneity and apparent density of the chars were increased compared to the raw RDF wastes. The chars and hydrochars produced present higher HHV and lower moisture and chlorine content. In the case of chars, a washing step seems to be essential to reduce the chlorine content to allow them to be used as an alternative fuel. In conclusion, both dry and wet carbonization demonstrated to be important pretreatments of the RDF to produce chars with improved physical and combustion properties. Full article
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18 pages, 3021 KiB  
Article
Immobilization of Cellulolytic Enzymes in Accurel® MP1000
by Julia R. S. Baruque, Adriano Carniel, Júlio C. S. Sales, Bernardo D. Ribeiro, Rodrigo P. do Nascimento and Ivaldo Itabaiana, Jr.
Reactions 2023, 4(2), 311-328; https://doi.org/10.3390/reactions4020019 - 16 Jun 2023
Viewed by 1347
Abstract
Cellulases are a class of enzymes of great industrial interest that present several strategic applications. However, the high cost of enzyme production, coupled with the instabilities and complexities of proteins required for hydrolytic processes, still limits their use in several protocols. Therefore, enzyme [...] Read more.
Cellulases are a class of enzymes of great industrial interest that present several strategic applications. However, the high cost of enzyme production, coupled with the instabilities and complexities of proteins required for hydrolytic processes, still limits their use in several protocols. Therefore, enzyme immobilization may be an essential tool to overcome these issues. The present work aimed to evaluate the immobilization of cellulolytic enzymes of the commercial enzyme cocktail Celluclast® 1.5 L in comparison to the cellulolytic enzyme cocktail produced from the wild strain Trichoderma harzianum I14-12 in Accurel® MP1000. Among the variables studied were temperature at 40 °C, ionic strength of 50 mM, and 72 h of immobilization, with 15 m·L −1 of proteins generated biocatalysts with high immobilization efficiencies (87% for ACC-Celluclast biocatalyst and 95% for ACC-ThI1412 biocatalyst), high retention of activity, and specific activities in the support for CMCase (DNS method), FPase (filter paper method) and β-glucosidase (p-nitrophenyl-β-D-glucopyranoside method). Presenting a lower protein concentration (0.32 m·L−1) than the commercial Celluclast® 1.5 L preparation (45 m·L−1), the ACC-ThI1412-derived immobilized biocatalyst showed thermal stability at temperatures higher than 60 °C, maintaining more than 90% of the residual activities of FPase, CMCase, and β-glucosidase. In contrast, the commercial-free enzyme presented a maximum catalytic activity at only 40 °C. Moreover, the difference in molecular weight between the component enzymes of the extract was responsible for different hydrophobic and lodging interactions of proteins on the support, generating a robust and competitive biocatalyst. Full article
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16 pages, 5825 KiB  
Article
Biofuels from Pyrolysis of Third-Generation Biomass from Household and Garden Waste Composting Bin: Kinetics Analysis
by Bruna Rijo, Ana Paula Soares Dias, Novi Dwi Saksiwi, Manuel Francisco Costa Pereira, Rodica Zăvoianu, Octavian Dumitru Pavel, Olga Ferreira and Rui Galhano dos Santos
Reactions 2023, 4(2), 295-310; https://doi.org/10.3390/reactions4020018 - 12 Jun 2023
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Abstract
The modern society produces large amounts of household waste with high organic matter content. The vermicomposting of household waste produces high-value humic substances and is a way to stabilize organic material for later use as raw material (3rd generation biomass) for bioenergy proposes. [...] Read more.
The modern society produces large amounts of household waste with high organic matter content. The vermicomposting of household waste produces high-value humic substances and is a way to stabilize organic material for later use as raw material (3rd generation biomass) for bioenergy proposes. A 6-month matured compost, combining vegetable and fruit scraps from domestic trash and grass and shrub clippings from yard waste, was evaluated to assess its potential as a raw material in pyrolysis processes. The pyrolysis activation energy (Kissinger) of the composted material showed values in the range of 200–300 kJ/mol, thus confirming its suitability for pyrolysis processes with promising H2 yields. The treatment of the composted material with H2SO4 and NaOH solution (boiling; 1 mol/L) led to the production of solid residues that present higher pyrolysis activation energies, reaching 550 kJ/mol for the most resilient fraction, which makes them suitable to produce carbonaceous materials (biochar) that will have incorporated the inorganics existing in the original compost (ashes 37.6%). The high content of inorganics would play a chief role during pyrolysis since they act as gasification promoters. Full article
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23 pages, 3789 KiB  
Article
Preliminary Studies on the Electrochemical Conversion of Liquefied Forest Biomass
by Tiago Silva, José Condeço and Diogo M. F. Santos
Reactions 2022, 3(4), 553-575; https://doi.org/10.3390/reactions3040037 - 31 Oct 2022
Cited by 2 | Viewed by 1656
Abstract
Bio-oils produced from three different biomass sources, namely cork, pinewood, and olive stones, are evaluated concerning their suitability and prospects of including their electrochemical transformations in a biorefinery scenario for the production of added-value compounds. Different types and concentrations of electrolytes (e.g., H [...] Read more.
Bio-oils produced from three different biomass sources, namely cork, pinewood, and olive stones, are evaluated concerning their suitability and prospects of including their electrochemical transformations in a biorefinery scenario for the production of added-value compounds. Different types and concentrations of electrolytes (e.g., H2SO4, KOH) are added to the bio-oils to increase the samples’ initially low ionic conductivity. The samples prepared by mixing bio-oil with 2 M KOH aqueous solution (50 vol.%) lead to a stable and homogeneous bio-oil alkaline emulsion suitable for electrochemical studies. The bio-oil samples are characterized by physicochemical methods (e.g., density, viscosity, conductivity), followed by analyzing their electrochemical behavior by voltammetric and chronoamperometric studies. The organics electrooxidation and the hydrogen evolution reaction in the bio-oils are assessed using Pt electrodes. Single- and two-compartment cell laboratory bio-oil electrolyzers are assembled using nickel plate electrodes. Electrolysis is carried out at 2.5 V for 24 h. Attenuated Total Reflection-Fourier-Transform Infrared Spectroscopy and Mass Spectrometry are applied to identify possible changes in the bio-oil samples’ chemical structure during the electrolysis experiments. Comparing the analyses of the bio-oil samples subjected to electrolysis with the blank samples demonstrates that bulk electrolysis significantly changes the bio-oil composition. The bio-oil obtained from cork biomass shows the most promising results, but further studies are required to understand the nature of the actual changes. Full article
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Review

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66 pages, 8444 KiB  
Review
Transformations of Glycerol into High-Value-Added Chemical Products: Ketalization and Esterification Reactions
by Federico M. Perez, Martin N. Gatti, Gerardo F. Santori and Francisco Pompeo
Reactions 2023, 4(4), 569-634; https://doi.org/10.3390/reactions4040034 - 8 Oct 2023
Viewed by 1552
Abstract
Biomass allows us to obtain energy and high-value-added compounds through the use of different physical and chemical processes. The glycerol obtained as a by-product in the synthesis of biodiesel is considered a biomass compound that has the potential to be used as a [...] Read more.
Biomass allows us to obtain energy and high-value-added compounds through the use of different physical and chemical processes. The glycerol obtained as a by-product in the synthesis of biodiesel is considered a biomass compound that has the potential to be used as a raw material to obtain different chemical products for industry. The development and growth of the biodiesel industry allows for the projection of glycerol biorefineries around these plants that efficiently and sustainably integrate the biodiesel production process together with the glycerol transformation processes. This work presents a review of the ketalization and esterification of glycerol to obtain solketal and acetylglycerols, which are considered products of high added value for the chemical and fuel industry. First, the general aspects and mechanisms of both reactions are presented, as well as the related chemical equilibrium concepts. Subsequently, the catalysts employed are described, classifying them according to their catalytic nature (zeolites, carbons, exchange resins, etc.). The reaction conditions used are also described, and the best results for each catalytic system are presented. In addition, stability studies and the main deactivation mechanisms are discussed. Finally, the work presents the kinetic models that have been formulated to date for some of these systems. It is expected that this review work will serve as a tool for the advancement of studies on the ketalization and esterification reactions that allow for the projection of biorefineries based on glycerol as a raw material. Full article
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