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Special Issue "Advances in Conversion of Biomass and Waste to Chemicals and Fuels"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (30 November 2020) | Viewed by 21705

Special Issue Editors

Prof. Dr. Rafael Luque
grade E-Mail Website
Guest Editor
Departamento de Química Orgánica, Universidad de Córdoba, Campus de Rabanales, Edificio Marie Curie (C-3), Ctra Nnal IV-A, Km 396, Córdoba, Spain
Interests: green chemistry; biomass valorization; heterogeneous catalysis; nanomaterial design
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Luís Adriano Santos Do Nascimento
E-Mail Website
Guest Editor
Institute of Biological Sciences, Federal University of Pará, Belém, Brazil
Interests: biomass/waste valorisation; oil chemistry; heterogeneous catalysts; biofuels

Special Issue Information

Dear Colleagues,

Residual biomass and wastes are ideal and sustainable substitutes for products derived from petroleum. The development of processes for decreasing the use of non-renewable products is recent, but significant. Several new technologies are focusing processes for the production of biofuels and chemicals from different types of residual biomass or wastes. However, research on these themes is advancing extremely fast; therefore, a compilation of the latest advances in the field would be useful to connect interested authors and readers. This Special Issue aims to cover recent and emerging strategies for the development of sustainable biomass/waste conversion processes, focusing on the aspects that drive present and future research, from chemical catalysis to biocatalysis and bioprocessing. For authors, this issue will be a good opportunity to publish their original research after peer review by expert researchers of biomass/waste valorisation. Review articles by experts in such fields of research are also strongly encouraged to be submitted for publication in this Special Issue.

Prof. Rafael Luque
Prof. Luís Adriano Santos do Nascimento
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2300 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • waste valorisation
  • biomass
  • lignocellulosic
  • lipidic
  • biofuels
  • biorefinery

Published Papers (12 papers)

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Research

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Article
Effect of Oligosaccharide Degree of Polymerization on the Induction of Xylan-Degrading Enzymes by Fusarium oxysporum f. sp. Lycopersici
Molecules 2020, 25(24), 5849; https://doi.org/10.3390/molecules25245849 - 11 Dec 2020
Cited by 4 | Viewed by 1096
Abstract
Xylan is one of the most abundant carbohydrates on Earth. Complete degradation of xylan is achieved by the collaborative action of endo-β-1,4-xylanases and β-d-xylosidases and a number of accessories enzymes. In filamentous fungi, the xylanolytic system is controlled through induction and [...] Read more.
Xylan is one of the most abundant carbohydrates on Earth. Complete degradation of xylan is achieved by the collaborative action of endo-β-1,4-xylanases and β-d-xylosidases and a number of accessories enzymes. In filamentous fungi, the xylanolytic system is controlled through induction and repression. However, the exact mechanism remains unclear. Substrates containing xylan promote the induction of xylanases, which release xylooligosaccharides. These, in turn, induce expression of xylanase-encoding genes. Here, we aimed to determine which xylan degradation products acted as inducers, and whether the size of the released oligomer correlated with its induction strength. To this end, we compared xylanase production by different inducers, such as sophorose, lactose, cellooligosaccharides, and xylooligosaccharides in Fusarium oxysporum f. sp. lycopersici. Results indicate that xylooligosaccharides are more effective than other substrates at inducing endoxylanase and β-xylosidases. Moreover, we report a correlation between the degree of xylooligosaccharide polymerization and induction efficiency of each enzyme. Specifically, xylotetraose is the best inducer of endoxylanase, xylohexaose of extracellular β-xylosidase, and xylobiose of cell-bound β-xylosidase. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Article
Analysis of the Effect of the Biomass Torrefaction Process on Selected Parameters of Dust Explosivity
Molecules 2020, 25(15), 3525; https://doi.org/10.3390/molecules25153525 - 01 Aug 2020
Cited by 1 | Viewed by 1075
Abstract
This article presents the findings of a study investigating the explosion and combustion parameters of dust from the raw biomass of wheat straw and energy willow and from the products of biomass torrefaction generated at temperatures ranging from 220 to 300 °C. Agricultural [...] Read more.
This article presents the findings of a study investigating the explosion and combustion parameters of dust from the raw biomass of wheat straw and energy willow and from the products of biomass torrefaction generated at temperatures ranging from 220 to 300 °C. Agricultural waste and energy crops and their modifications, e.g., in the torrefaction process, did not find a place in explosive risk research, which the authors decided to present in their work. The study was designed to estimate explosion hazard during the processing of the materials into fuels and during the storage process. The measurements recorded a maximum explosion pressure Pmax in the case of dust from biomass ranging from 7.2 to 7.3 bar and for dust from torrefied materials amounting to 7.5–9.2 bar, and a maximum rate of pressure rise over time (dp/dt)max in raw biomass ranging from 201.4 to 261.3 bar/s and in torrefied materials amounting to 209.6–296.6 bar/s. The estimated explosion index Kstmax for raw biomass was 55–72 m*bar/s and for torrefied materials was in the range from 57 to 81 m*bar/s. In the results, the authors present values for specific types of fuel which differ significantly depending on the type of biomass. The research findings show that the torrefaction process used in fuel production is not associated with a significantly greater risk of explosion and the materials obtained may safely be used as an alternative to conventional solid fuels. Given the growing interest in the use of biomass and in the variety of biomass processing methods for energy-related purposes, it seems there is a need for research to develop appropriate guidelines and for effective practices to be introduced in the energy industry in order to ensure the safety of the processes used in the production of novel fuels especially in small installations converting these materials into more efficient energy material. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Article
Photocatalytic Cleavage of β-O-4 Ether Bonds in Lignin over Ni/TiO2
Molecules 2020, 25(9), 2109; https://doi.org/10.3390/molecules25092109 - 30 Apr 2020
Cited by 11 | Viewed by 1723
Abstract
It is of great importance to explore the selective hydrogenolysis of β-O-4 linkages, which account for 45–60% of all linkages in native lignin, to produce valued-added chemicals and fuels from biomass employing UV light as catalyst. TiO2 exhibited satisfactory catalytic [...] Read more.
It is of great importance to explore the selective hydrogenolysis of β-O-4 linkages, which account for 45–60% of all linkages in native lignin, to produce valued-added chemicals and fuels from biomass employing UV light as catalyst. TiO2 exhibited satisfactory catalytic performances in various photochemical reactions, due to its versatile advantages involving high catalytic activity, low cost and non-toxicity. In this work, 20 wt.% Ni/TiO2 and oxidant PCC (Pyridinium chlorochromate) were employed to promote the cleavage of β-O-4 alcohol to obtain high value chemicals under UV irradiation at room temperature. The Ni/TiO2 photocatalyst can be magnetically recovered and efficiently reused in the following four consecutive recycling tests in the cleavage of β-O-4 ether bond in lignin. Mechanism studies suggested that the oxidation of β-O-4 alcohol to β-O-4 ketone by oxidant PCC first occurred during the reaction, and was followed by the photocatalysis of the obtained β-O-4 ketone to corresponding acetophenone and phenol derivates. Furthermore, the system was tested on a variety of lignin model substrates containing β-O-4 linkage for the generation of fragmentation products in good to excellent results. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Article
The Effect of Thermomechanical Pretreatment on the Structure and Properties of Lignin-Rich Plant Biomass
Molecules 2020, 25(4), 995; https://doi.org/10.3390/molecules25040995 - 23 Feb 2020
Cited by 7 | Viewed by 1638
Abstract
The cooperative thermomechanical properties of plant-derived polymers have been studied insufficiently, although this feedstock has a very high potential. In the present paper, we analyzed the changes in the structure and physicochemical properties of lignin-rich biomass induced by thermomechanical pretreatment. Low-temperature treatment allows [...] Read more.
The cooperative thermomechanical properties of plant-derived polymers have been studied insufficiently, although this feedstock has a very high potential. In the present paper, we analyzed the changes in the structure and physicochemical properties of lignin-rich biomass induced by thermomechanical pretreatment. Low-temperature treatment allows one to retain the original supramolecular structure of the cell walls, while an appreciably high disintegration degree is reached. This increases the reactivity of the material in the subsequent heterogeneous reactions. Mechanical pretreatment at medium temperatures (10 °C), when almost all cell wall polymers except for low-molecular-weight lignin are in the glassy state, enhances the mobility of cell wall polymers and causes sufficient cellulose disordering, while the specific surface area is not significantly increased. High-temperature pretreatment of reed biomass is accompanied by pore formation and lignin release from the cell wall structure, which opens up new prospects for using this biomass as a matrix to produce core–shell-structured sorbents of heavy metals. The energy consumed by mechanochemical equipment for the activation of reed biomass was determined. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Article
Towards the Properties of Different Biomass-Derived Proteins via Various Extraction Methods
Molecules 2020, 25(3), 488; https://doi.org/10.3390/molecules25030488 - 23 Jan 2020
Cited by 19 | Viewed by 2310
Abstract
This study selected three representative protein-rich biomass—brewer’s spent grain (BSG), pasture grass (PG), and cyanobacteria (Arthrospira platensis; AP) for protein extraction with different extraction methods (alkaline treatment, aqueous extraction, and subcritical water extraction). The yield, purity, molecular weight, oil–water interfacial tension, [...] Read more.
This study selected three representative protein-rich biomass—brewer’s spent grain (BSG), pasture grass (PG), and cyanobacteria (Arthrospira platensis; AP) for protein extraction with different extraction methods (alkaline treatment, aqueous extraction, and subcritical water extraction). The yield, purity, molecular weight, oil–water interfacial tension, and thermal stability of the obtained proteins derived from different biomass and extraction methods were comprehensively characterized and compared. In the view of protein yield and purity, alkaline treatment was found optimal for BSG (21.4 and 60.2 wt.%, respectively) and AP (55.5 and 68.8 wt.%, respectively). With the decreased oil–water interfacial tension, the proteins from all biomass showed the potential to be emulsifier. BSG and AP protein obtained with chemical treatment presented excellent thermal stability. As a novel method, subcritical water extraction is promising in recovering protein from all three biomass with the comparable yield and purity as alkaline treatment. Furthermore, the hydrolyzed protein with lower molecular weight by subcritical water could promote its functions of foaming and emulsifying. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Article
Pathogen Reduction Potential in Anaerobic Digestion of Organic Fraction of Municipal Solid Waste and Food Waste
Molecules 2020, 25(2), 275; https://doi.org/10.3390/molecules25020275 - 09 Jan 2020
Cited by 26 | Viewed by 1753
Abstract
Anaerobic digestion (AD) is a commonly used method of processing waste. Regardless of the type of the used digestate (fertilizer, feedstock in case of solid-state fermentation, raw-material in case of thermal treatment) effective pathogen risk elimination, even in the case of high pathogen [...] Read more.
Anaerobic digestion (AD) is a commonly used method of processing waste. Regardless of the type of the used digestate (fertilizer, feedstock in case of solid-state fermentation, raw-material in case of thermal treatment) effective pathogen risk elimination, even in the case of high pathogen concentration is essential. An investigation of the survival time and inactivation rate of the Salmonella Senftenberg W775, Enterococcus spp., and Ascaris suum eggs during thermophilic anaerobic digestion performed on laboratory scale and confirmation of hygienization in full-scale operation were performed in this study. Except for sanitization efficiency, the AD process performance and stability were also verified based on determination of pH value, dry matter content, acidity, alkalinity, and content of fatty acids. The elimination of pathogen was met within 6.06 h, 5.5 h, and about 10 h for the Salmonella Senftenberg W775, Enterococcus spp., and Ascaris suum, respectively in the laboratory trials. The obtained results were confirmed in full-scale tests, using 1500 m3 Kompogas® reactors, operating in MBT Plant located in Poland. Sanitization of the digestate was achieved. Furthermore, the process was stable. The pH value, suspended solids, and ammonium content remained stable at 8.5, 35%, and 3.8 g/kg, respectively. The acetic acid content was noted between almost 0.8 and over 1.1 g/kg, while the concentration of propionic acid was noted at maximum level of about 100 mg/kg. The AD conditions could positively affect the pathogen elimination. Based on these results it can be found that anaerobic digestion under thermophilic conditions results in high sanitation efficiency. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Article
Single-Step Methylation of Chitosan Using Dimethyl Carbonate as a Green Methylating Agent
Molecules 2019, 24(21), 3986; https://doi.org/10.3390/molecules24213986 - 04 Nov 2019
Cited by 5 | Viewed by 2025
Abstract
N,N,N-Trimethyl chitosan (TMC) is one chitosan derivative that, because of its improved solubility, has been studied for industrial and pharmaceutic applications. Conventional methods for the synthesis of TMC involve the use of highly toxic and harmful reagents, such as methyl iodide and [...] Read more.
N,N,N-Trimethyl chitosan (TMC) is one chitosan derivative that, because of its improved solubility, has been studied for industrial and pharmaceutic applications. Conventional methods for the synthesis of TMC involve the use of highly toxic and harmful reagents, such as methyl iodide and dimethyl sulfate (DMS). Although the methylation of dimethylated chitosan to TMC by dimethyl carbonate (DMC, a green and benign methylating agent) was reported recently, it involved a formaldehyde-based procedure. In this paper we report the single-step synthesis of TMC from chitosan using DMC in an ionic liquid. The TMC synthesised was characterised by 1H NMR spectroscopy and a functionally meaningful degree of quaternisation of 9% was demonstrated after a 12-h reaction time. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Article
Genome-Wide and Functional View of Proteolytic and Lipolytic Bacteria for Efficient Biogas Production through Enhanced Sewage Sludge Hydrolysis
Molecules 2019, 24(14), 2624; https://doi.org/10.3390/molecules24142624 - 18 Jul 2019
Cited by 2 | Viewed by 1570
Abstract
In this study, we used a multifaceted approach to select robust bioaugmentation candidates for enhancing biogas production and to demonstrate the usefulness of a genome-centric approach for strain selection for specific bioaugmentation purposes. We also investigated the influence of the isolation source of [...] Read more.
In this study, we used a multifaceted approach to select robust bioaugmentation candidates for enhancing biogas production and to demonstrate the usefulness of a genome-centric approach for strain selection for specific bioaugmentation purposes. We also investigated the influence of the isolation source of bacterial strains on their metabolic potential and their efficiency in enhancing anaerobic digestion. Whole genome sequencing, metabolic pathway reconstruction, and physiological analyses, including phenomics, of phylogenetically diverse strains, Rummeliibacillus sp. POC4, Ochrobactrum sp. POC9 (both isolated from sewage sludge) and Brevundimonas sp. LPMIX5 (isolated from an agricultural biogas plant) showed their diverse enzymatic activities, metabolic versatility and ability to survive under varied growth conditions. All tested strains display proteolytic, lipolytic, cellulolytic, amylolytic, and xylanolytic activities and are able to utilize a wide array of single carbon and energy sources, as well as more complex industrial by-products, such as dairy waste and molasses. The specific enzymatic activity expressed by the three strains studied was related to the type of substrate present in the original isolation source. Bioaugmentation with sewage sludge isolates–POC4 and POC9–was more effective for enhancing biogas production from sewage sludge (22% and 28%, respectively) than an approach based on LPMIX5 strain (biogas production boosted by 7%) that had been isolated from an agricultural biogas plant, where other type of substrate is used. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Article
Development and Optimization of the Biological Conversion of Ethane to Ethanol Using Whole-Cell Methanotrophs Possessing Methane Monooxygenase
Molecules 2019, 24(3), 591; https://doi.org/10.3390/molecules24030591 - 07 Feb 2019
Cited by 6 | Viewed by 1585
Abstract
The biological production of ethanol from ethane for the utilization of ethane in natural gas was investigated under ambient conditions using whole-cell methanotrophs possessing methane monooxygenase. Several independent variables including ethane concentration and biocatalyst amounts, among other factors, were optimized for the enhancement [...] Read more.
The biological production of ethanol from ethane for the utilization of ethane in natural gas was investigated under ambient conditions using whole-cell methanotrophs possessing methane monooxygenase. Several independent variables including ethane concentration and biocatalyst amounts, among other factors, were optimized for the enhancement of ethane-to-ethanol bioconversion. We obtained 0.4 g/L/h of volumetric productivity and 0.52 g/L of maximum titer in optimum batch reaction conditions. In this study, we demonstrate that the biological gas-to-liquid conversion of ethane to ethanol has potent technical feasibility as a new application of ethane gas. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Article
High-Quality Biodiesel Production from Buriti (Mauritia flexuosa) Oil Soapstock
Molecules 2019, 24(1), 94; https://doi.org/10.3390/molecules24010094 - 28 Dec 2018
Cited by 11 | Viewed by 2626
Abstract
The buriti palm (Mauritia flexuosa) is a palm tree widely distributed throughout tropical South America. The oil extracted from the fruits of this palm tree is rich in natural antioxidants. The by-products obtained from the buriti palm have social and economic [...] Read more.
The buriti palm (Mauritia flexuosa) is a palm tree widely distributed throughout tropical South America. The oil extracted from the fruits of this palm tree is rich in natural antioxidants. The by-products obtained from the buriti palm have social and economic importance as well, hence the interest in adding value to the residue left from refining this oil to obtain biofuel. The process of methyl esters production from the buriti oil soapstock was optimized considering acidulation and esterification. The effect of the molar ratio of sulfuric acid (H2SO4) to soapstock in the range from 0.6 to 1.0 and the reaction time (30–90 min) were analyzed. The best conditions for acidulation were molar ratio 0.8 and reaction time of 60 min. Next, the esterification of the fatty acids obtained was performed using methanol and H2SO4 as catalyst. The effects of the molar ratio (9:1–27:1), percentage of catalyst (2–6%) and reaction time (1–14 h) were investigated. The best reaction conditions were: 18:1 molar ratio, 4% catalyst and 14 h reaction time, which resulted in a yield of 92% and a conversion of 99.9%. All the key biodiesel physicochemical characterizations were within the parameters established by the Brazilian standard. The biodiesel obtained presented high ester content (96.6%) and oxidative stability (16.1 h). Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Review

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Review
Breeding Targets to Improve Biomass Quality in Miscanthus
Molecules 2021, 26(2), 254; https://doi.org/10.3390/molecules26020254 - 06 Jan 2021
Cited by 3 | Viewed by 1347
Abstract
Lignocellulosic crops are attractive bioresources for energy and chemicals production within a sustainable, carbon circular society. Miscanthus is one of the perennial grasses that exhibits great potential as a dedicated feedstock for conversion to biobased products in integrated biorefineries. The current biorefinery strategies [...] Read more.
Lignocellulosic crops are attractive bioresources for energy and chemicals production within a sustainable, carbon circular society. Miscanthus is one of the perennial grasses that exhibits great potential as a dedicated feedstock for conversion to biobased products in integrated biorefineries. The current biorefinery strategies are primarily focused on polysaccharide valorization and require severe pretreatments to overcome the lignin barrier. The need for such pretreatments represents an economic burden and impacts the overall sustainability of the biorefinery. Hence, increasing its efficiency has been a topic of great interest. Inversely, though pretreatment will remain an essential step, there is room to reduce its severity by optimizing the biomass composition rendering it more exploitable. Extensive studies have examined the miscanthus cell wall structures in great detail, and pinpointed those components that affect biomass digestibility under various pretreatments. Although lignin content has been identified as the most important factor limiting cell wall deconstruction, the effect of polysaccharides and interaction between the different constituents play an important role as well. The natural variation that is available within different miscanthus species and increased understanding of biosynthetic cell wall pathways have specified the potential to create novel accessions with improved digestibility through breeding or genetic modification. This review discusses the contribution of the main cell wall components on biomass degradation in relation to hydrothermal, dilute acid and alkaline pretreatments. Furthermore, traits worth advancing through breeding will be discussed in light of past, present and future breeding efforts. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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Review
Catalytic Production of Jet Fuels from Biomass
Molecules 2020, 25(4), 802; https://doi.org/10.3390/molecules25040802 - 12 Feb 2020
Cited by 19 | Viewed by 2456
Abstract
Concerns about depleting fossil fuels and global warming effects are pushing our society to search for new renewable sources of energy with the potential to substitute coal, natural gas, and petroleum. In this sense, biomass, the only renewable source of carbon available on [...] Read more.
Concerns about depleting fossil fuels and global warming effects are pushing our society to search for new renewable sources of energy with the potential to substitute coal, natural gas, and petroleum. In this sense, biomass, the only renewable source of carbon available on Earth, is the perfect replacement for petroleum in producing renewable fuels. The aviation sector is responsible for a significant fraction of greenhouse gas emissions, and two billion barrels of petroleum are being consumed annually to produce the jet fuels required to transport people and goods around the world. Governments are pushing directives to replace fossil fuel-derived jet fuels with those derived from biomass. The present mini review is aimed to summarize the main technologies available today for converting biomass into liquid hydrocarbon fuels with a molecular weight and structure suitable for being used as aviation fuels. Particular emphasis will be placed on those routes involving heterogeneous catalysts. Full article
(This article belongs to the Special Issue Advances in Conversion of Biomass and Waste to Chemicals and Fuels)
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