Sustainable Valorization Research Articles

Sustainable valorization of food waste into a pore-forming agent for ceramic membrane production: Experimental and DFT studies on methylene blue dye removal

Sustainable valorization of food waste into a pore-forming agent for ceramic membrane production: Experimental and DFT studies on methylene blue dye removal

Sustainable valorisation of cigarette butts waste through pyrolysis: An insight into the pyrolytic products and subsequent aqueous heavy metals removal by pyrolytic char

In this study, cigarette butts (CB) waste was pyrolyzed over a wide temperature range (400–700 °C) using Pyro/GC–MS and slow pyrolysis experiments. The feedstock and char products were extensively investigated using TGA, elemental analysis, surface area and porosity analysis, SEM-EDS, XRD, and FT-IR, and subsequently tested for their ability to remove Ni (II) and Cu (II) from aqueous solutions. The Pyro/GC–MS analysis revealed the presence of several useful compounds including acids, esters and hydrocarbons. Char yields ranged from 26.6 to 20.1 wt%, and carbon contents varied from 65.3 to 60.8 wt%. The chars produced at medium temperatures (500-600 °C) were highly porous, with a specific surface area of 272.9–270.8 m2/g. The heavy metal adsorption studies revealed that CB 500 °C had the highest adsorption capacity of 13.8 mg/g with 53.4 % nickel removal, while CB 600 °C had the highest adsorption capacity of 23.4 mg/g with 94.7 % copper removal.

Novel and sustainable valorization of biogenic waste into microbial protein based fish dietary ingredient in bioreactor: process optimization and sustainable utilization

Novel and sustainable valorization of biogenic waste into microbial protein based fish dietary ingredient in bioreactor: process optimization and sustainable utilization

Comparative Analysis of Pretreatment Methods for Fruit Waste Valorization in Euglena gracilis Cultivation: Impacts on Biomass, β-1,3-Glucan Production, and Photosynthetic Efficiency.

This study explored the sustainable valorization of fruit waste extracts from sugarcane bagasse (SB), banana peel (BP), and watermelon rind (WR) for Euglena gracilis biomass and β-1,3-glucan production. The extracts were prepared using water extraction (WE), high-temperature and pressure treatment (HTP), and dilute sulfuric acid treatment (DSA). The DSA-treated extracts consistently yielded the best results. E. gracilis cultured in SB-DSA showed the highest cell density with a 2.08-fold increase compared to the commercial HUT medium, followed by BP-DSA (1.35-fold) and WR-DSA (1.70-fold). Photosynthetic pigment production increased significantly, with chlorophyll a yield being highest in SB-DSA (1.90-fold increase). The chlorophyll a/b ratio and total carotenoid content also improved, indicating enhanced light-harvesting capacity and photoprotection. Photosynthetic efficiency, measured by chlorophyll fluorescence, notably improved. The maximum quantum yield of PSII (Fv/Fm) increased by up to 25.88% in SB-DSA, suggesting reduced stress and improved overall photosynthetic health. The potential photochemical efficiency (Fv/F0) showed even greater improvements: up to 40.53% in SB-DSA. Cell morphology analysis revealed larger cell aspect ratios, implying a more active cellular physiological state. β-1,3-glucan yield also increased by 23.99%, 12.92%, and 23.38% in SB-DSA, BP-DSA, and WR-DSA, respectively. This study demonstrates the potential of pretreated fruit waste as a cost-effective and sustainable medium for E. gracilis cultivation, offering the dual benefits of waste valorization and high-value compound production. These findings contribute to the development of more efficient biorefinery processes and align with the circular economy principles in food biotechnology.

Sustainable Valorisation of Coffee Waste as a Protein Source, Mycelium-Based Packaging Material and Renewable Energy Pellet.

This study investigates the valorization of spent coffee grounds (SCGs) through protein extraction and their application in mycelium-based packaging and renewable energy pellets. Three extraction methods-mechanical stirring, ultrasound-assisted, and CO2-assisted extraction-were applied to SCGs. CO2-assisted extraction yielded the highest protein content at 34.24%, followed by mechanical stirring (31.46%) and ultrasound-assisted extraction (28.51%). The total polyphenol content and antioxidant capacity were also highest in the CO2 extracts, suggesting that this method preserves bioactive compounds most effectively. After protein extraction, SCGs were tested as a component in mycelium-based packaging, with results showing an apparent density of 0.551 g/cm3 and compression resistance of 3.354 MPa, indicating its suitability for structural applications. The energy value of SCGs remained high, with a calorific value of 19,887 J/g DW, slightly decreasing after extraction but still sufficient for renewable energy production. These findings highlight the potential of SCGs as a multi-functional resource, contributing to sustainable solutions across various industries.

Red Mud as a Potential Catalyst for Petrochemicals Production from Oxygenated Aromatic Plastic Wastes via Fast Pyrolysis

The increased rate of post‐use accumulation of the heteroatom‐containing plastic wastes like polyethylene terephthalate (PET), polycarbonate (PC) and polyurethane (PU) in the environment propels the research for effective and sustainable valorization. In this study, PET from bottle waste, PC from compact discs and PU from waste wind turbine blade were characterized and employed for fast pyrolysis experiments. Importantly, red mud (RM), a mixed oxide, rich in Fe, Al, Si, Na and Ca, was used as a catalyst for fast pyrolysis. The effects of temperature and feed‐to‐catalyst ratio on product yields were studied to elucidate the product formation mechanism. Benzoic acid and its derivatives, bisphenol‐A and oxygenated aromatics, and 4,4’‐methylenebisbenzamine were the major products obtained from the non‐catalytic fast pyrolysis of PET, PC and PU, respectively. The use of RM improved the yield of aromatic hydrocarbons from PET to 27.8 wt.% at 550°C, phenolics from PC to 46.6 wt.% at 550°C, and 4,4’‐methylenebisbenzamine to 34.9 wt.% at 650oC. The catalytic activity of RM is ascribed to the presence of active basic sites. The present study paves the path for the catalytic upcycling of challenging plastic wastes using industrial waste like RM as a sustainable catalyst from a circular economy viewpoint.

Co-pyrolysis of plastic waste and macroalgae Ulva lactuca, a sustainable valorization approach towards the production of bio-oil and biochar

To address the pressing demand for sustainable energy in light of environmental challenges, this study explored the synergetic effects of the co-pyrolysis of polyethylene terephthalate (PET) and Ulva lactuca macroalgae to yield bio-oil and biochar. The objective is to enhance the bio-oil quality for wider usability and to combat marine pollution. By employing co-pyrolysis, notable progress has been achieved in bio-oil yield and quality, particularly in hydrocarbon content, through the integration of PET. The highest bio-oil yield of 37.91 % was achieved under optimal conditions at 500 °C with a feedstock mixture consisting of 40 % U. lactuca and 60 % PET. Under these conditions, the bio-oil exhibited a significant increase in hydrocarbon content, reaching 57.16 %, which is essential for improving its energy potential. Biochar quality was also enhanced, with the biochar from a 70 % U. lactuca and 30 % PET blend showing a BET surface area of 20.18 m2/g, compared to the initial 1.38 m2/g of raw U. lactuca, indicating improved surface properties. This study presents a sustainable energy generation and environmental preservation approach, underscoring the potential of synergistically utilizing marine resources and plastic waste.

Sustainable Valorization of CO2 through Nuclear Power-to-X Pathways

Some of the issues concerning energy security and climate change can be addressed by employing nuclear power (NP) to supply the energy required for the conversion of carbon dioxide (CO2) into chemicals, products, and materials. Nuclear energy represents a neutral carbon source that can be generated sustainably, reliably, and consistently. Nuclear power plants (NPPs) could supply energy in the form of heat, electricity, and ionizing radiation to drive CO2 chemical reactions underpinning NP-to-X type of pathways. CO2 conversion processes are either commercially available or emerging technologies at different developmental maturity stages. This work reviews the published literature (articles and patents) that reports R&D results and the understanding and development of chemical reactions and processes, as well as the efforts in integrating NPPs and chemical processes (CPs). As will be made evident, a new industrial era for the manufacturing of decarbonized chemicals, products, and materials will be possible by developing and implementing new (more energy- and carbon-efficient) processes responding to the NP-to-X pathways. This new decarbonizing platform not only contributes to achieving net zero goals but also broadens the NPP product beyond electricity.

Sustainable Valorization of Jarosite as a Concrete Material Investigation of Hydration, Mechanical, and Durability Properties

Sustainable Valorization of Jarosite as a Concrete Material Investigation of Hydration, Mechanical, and Durability Properties

Effect of Ni/tire rubber carbon as catalyst in the hydrodeoxygenation of used vegetable oil: biofuel evaluation in the reduction of atmospheric emissions

Abstract The sustainable valorization of discarded resources remains a challenge, and their requirements are crucial for long-term development. In this sense, we characterize biofuels of the diesel range obtained with used vegetable oils subjected to hydrodeoxygenation with Ni supported on tire rubber carbon obtained by the pyrolysis of waste tires. Under optimal reaction conditions, the vegetable oil conversion was 81.2 % with a selectivity of 82.3 % to C10–C18 alkanes, which is supported by the results of the catalyst characterization. A vertical direct injection engine was used to compare the behavior of the renewable biofuel and petroleum diesel blends. In comparison to petroleum diesel, the blends with renewable biofuel showed minimal power loss. In addition, the use of blends containing biofuels allowed a reduction of 25 % of CO and HC, as well as a decrease of 48 % is smoke compared to petroleum diesel, due to the fact that renewable biofuels improved evaporation after injection, reduced the density, and did not contain aromatic components.

Phenolic profile, cytotoxicity and in vitro antioxidant and enzyme inhibitory properties of the edible halophyte Sarcocornia fruticosa from southeastern Tunisia

This work aims to boost the sustainable valorization of the edible halophyte Sarcocornia fruticosa (L.) A.J. Scott (Amaranthaceae) from Southern Tunisia by assessing its potential as a source of bioactive components. To achieve this, hydroethanolic extracts of S. fruticosa, collected from two distinct Tunisian biomes (Zarzis: SFZ and Djerba: SFDJ), were profiled for total phenolic, flavonoid, and condensed tannin contents, as well as for individual phenolic composition by HPLC-ESI-MS. Then, the extracts were evaluated for in vitro antioxidant properties via complementary methods and for in vitro inhibition of enzymes related to Alzheimer's disease (acetylcholinesterase: AChE, and butyrylcholinesterase: BuChE), type 2 diabetes (α-glucosidase and α-amylase), and hyperpigmentation and food oxidation (tyrosinase). Finally, they were assessed for acute in vitro toxicity. Our findings identified thirteen phenolic compounds, with rutin being the predominant compound and its content being nearly twice as high in SFZ than in SFDJ (1224.51 and 643.61 mg/kg DW, respectively). Salvianolic acid B was also reported for the first time in Sarcocornia genus. The extracts exhibited notable ferric reducing antioxidant power (FRAP), with SFZ displaying an effective median concentration (EC50) value of 0.97 mg/mL. They also showed promising inhibitory effects on acetylcholinesterase (>40%) and tyrosinase (>50%), without any cytotoxicity. The Zarzis ecotype in particular displayed superior bioactive properties, making it an excellent candidate for future cultivation trials under saline conditions, with potentially valuable economic outcomes for the region. These findings highlight the potential of S. fruticosa as a source of functional ingredients with nutraceutical and therapeutic applications.

Sustainable valorisation of freshwater fish by‐products to gelatin and fish oil by hydrothermal extraction

SummaryThis study explores the potential of hydrothermal extraction as an innovative valorisation method for the simultaneous production of gelatin and fish oil from fish byproducts. It offers an environmentally friendly alternative to conventional solvent‐based techniques by minimising the use of chemical solvents and water. We researched various major commercial freshwater fish species: striped catfish, catfish, and tilapia, and achieved a gelatin product that reflects commercial standards in chemical structure, gel strength, and pH level. The striped catfish gelatin showed the highest gel strength and viscosity (66.01 ± 0.83 g bloom and 15.3 ± 0.1 cP), but was produced at a lower yield than the catfish gelatin. On the other hand, striped catfish produced the highest yield of fish oil (13.56 ± 0.21%) and has the highest omega 3 content (3.72 ± 0.02%) than other fish oil. This innovative study demonstrates the potential of hydrothermal extraction as a sustainable method for producing gelatin and fish oil, offering eco‐friendly and nutritional benefits across a range of applications.

Sustainable valorization of waste plastic into nanostructured materials for environmental, energy, catalytic and biomedical applications: A review

The extensive production and utilization of plastic products are inevitable in the current scenario. However, the non-degradable nature of waste plastic generated after use poses a grave concern. Comprehensive efforts are being made to find viable technological solutions to manage the escalating challenge of waste plastic. This review focuses on the progress made in transformation of waste plastic into value-added nanomaterials. An overview is provided of the waste plastic issue on a global level and its ecological impacts. Currently established methodologies for waste plastic management are examined, along with their limitations. Subsequently, state-of-the-art techniques for converting waste plastic into nanostructured materials are presented, with a critical evaluation of their distinct merits and demerits. Several demonstrated technologies and case studies are discussed regarding the utilization of these nanomaterials in diverse applications, including environmental remediation, energy production and storage, catalytic processes, sensors, drug delivery, bioimaging, regenerative medicine and advanced packaging materials. Moreover, challenges and prospects in the commercial level production of waste plastic-derived nanomaterials and their adoption for industrial and practical usage are highlighted. Overall, this work underscores the potential of transforming waste plastic into nanostructured materials for multifaceted applications. The valorization approach presented here offers an integration of waste plastic management and sustainable nanotechnology. The development of such technologies should pave the way toward a circular economy and the attainment of sustainable development goals.

Sustainable valorisation of sand concrete properties using quarry waste as crushed sand

Sustainable valorisation of sand concrete properties using quarry waste as crushed sand

Life cycle analysis of apple pomace biorefining for biofuel and pectin production

This study investigated the environmental impacts associated with converting apple pomace, a globally abundant resource, into biofuels and high-value products using a comparative consequential life cycle assessment. In three developed scenarios, an acid pretreatment method was applied and the pretreated liquid was used for ethanol and pectin production. The pretreated solids were utilized to produce different products: scenario 1 produced biogas, scenario 2 generated butanol, and scenario 3 yielded both biogas and butanol from the solids. The results demonstrated that scenario 1 exhibited the best performance compared to the other two scenarios, imposing the lowest environmental burdens across all damage categories, including human health, ecosystems, and resources. Despite the induced impacts, the benefits of avoided products, i.e., ethanol, natural gas, butanol, acetone, and pectin, compensated for these induced environmental impacts to some extent. The results also revealed that among all products generated through the biorefineries, first-generation ethanol substitution had the most significant positive environmental impacts. Overall, the biorefinery developed in scenario 1 represents the most feasible strategy for a circular bioeconomy. It performs 84.38 % and 72.98 % better than scenarios 2 and 3 in terms of human health, 85.34 % and 74.54 % better in terms of ecosystems, and more than 100 % better in terms of resources. Conversely, scenario 2 resulted in the highest net impacts across all damage categories. Furthermore, in scenario 1, the midpoint results showed 83.10 % and 71.08 % lower impacts on global warming, 85.15 % and 74.17 % lower impacts on terrestrial acidification, and 99.26 % and 98.53 % lower impacts on fossil resource scarcity compared to scenarios 2 and 3, respectively. In conclusion, the first scenario shows promise for the sustainable valorization of apple pomace.

Catalytic Approaches to Tackle Mixed Plastic Waste Challenges: A Review.

Plastics are widely used materials in our daily lives and various industries due to their affordability and versatility. The massive production of plastic waste, however, has recently emerged as a pressing environmental concern across all media. To address this, emerging technologies are being explored for the sustainable valorization of postconsumer plastic wastes including thermochemical, physical, and catalytic processes aimed at transforming them into higher value-added products. However, the chemical recycling of mixed plastic wastes poses a formidable challenge due to the diverse array of monomers and catalyst systems involved, each employing distinct mechanisms. Complicating matters further is that contaminants reduce catalytic efficacy, requiring rigorous and labor-intensive separation and purification processes to extract individual plastic streams from practical plastic waste mixtures. Consequently, the majority of such mixtures often end up in incineration and landfills, perpetuating environmental and societal challenges, such as leachate, carbon dioxide emissions, and other air pollutants. This review will introduce current technical developments available for recycling practical plastic waste mixtures through catalytic processes. The current challenges in process performance, low selectivity of the desired products, and catalyst deactivation from the catalysis of plastic waste mixtures are also discussed. Promising approaches to overcome the problems are suggested in future research directions.

Microwave-assisted extraction of valuable phenolics from sunflower pomace with natural deep eutectic solvents and food applications of the extracts

AbstractA green process, both in terms of solvent (natural deep eutectic solvents, NADES) and extraction method (microwave-assisted extraction, MAE) for the recovery of bioactive components from sunflower pomace (SFP, a by-product of oil extraction process), was designed to contribute to their sustainable valorization. For the extraction of valuable phenolics from sunflower pomace, nine potential NADES were prepared. Among them, choline chloride-urea-water (CC-U-W) at a molar ratio of 1:2:4 was selected for extraction, showing better yield and physicochemical properties. Operational parameters (extraction temperature, time, water ratio, and solvent-to-solid ratio) for MAE were optimized and modeled utilizing response surface methodology. Under optimal conditions, the antioxidant properties of SFP extract were evaluated by CUPRAC, ABTS, and DPPH methods. The total phenolic contents of extracts were evaluated by the Folin–Ciocalteu method. Phenolics were characterized by using the HPLC–PDA system. The results showed that SFP NADES extract had potential antioxidant activity which was higher than that of traditional solvents. In order to better evaluate SFP extract as a valuable food ingredient, SFP extracts at a ratio of 5, 10, and 20% added smoothie-like beverages with strawberries and yogurt were prepared. Fortification of beverages with NADES extract enhanced antioxidant efficiency, increasing total antioxidant capacity in a range of 12.4 to 68.6% and free radical scavenging capacity between 0.4 to 67.9% during both the initial and the in vitro gastrointestinal digestion stages. The addition of SFP NADES extract to food samples made a positive contribution in terms of the antioxidant activity of the final product. The results of this study revealed that sunflower by-products can be evaluated as a potential antioxidant source which is easily accessible, and the proposed extraction process has an important potential to recover bioactive compounds with high efficiency.

Sulfonated graphitic carbon catalyst derived from coffee waste: A sustainable valorization approach for highly efficient production of 5-hydroxymethylfurfural (5-HMF) from fructose

According to recent research, a sulfonated 2D graphitic carbon catalyst for the dehydration of fructose to the platform chemical 5-Hydroxymethylfurfural (5-HMF) can be made from used ground coffee. By carbonizing and activating at different temperatures, sulfonated graphitic carbon (SC) catalysts with varied chemical compositions and textural characteristics were obtained. The physical and chemical characteristics of the SC catalysts were assessed using XRD, Raman, SEM-EDX, HR-TEM, BET analysis, and XPS. Due to its microporous structure, SC-900 exhibited a high specific area and demonstrated selective and efficient production of 5-HMF from fructose. All in all, the surface acidity of catalysts was measured by NH3-TPD, and acid-base titration methods. The SC-900 catalyst, designed through carbonization at 900 ℃, achieved a fructose conversion rate of 100 % and a 5-HMF yield of 97.91 % without generating any by-products. This indicates the catalyst essentially produces 5-HMF under the specified optimal conditions (140 ℃, 90 min) observed in this study. To determine the origins of the highly efficient and highly selective conversion of fructose to 5-HMF, the performance of the SC catalysts was systematically investigated vi-a-vis their physical and chemical properties. The development of microporous SC catalysts and their application as catalysts not only enhances the value of waste coffee but also provides an environmentally friendly approach for converting carbohydrates into 5-HMF.

Mapping the Sustainability of Waste-to-Energy Processes for Food Loss and Waste in Mexico—Part 1: Energy Feasibility Study

Mexico generated 8.9 Mt of food loss and waste (FLW) at food distribution and retail centers in the year 2022. Traditional management methods in Latin America primarily involve final disposal sites, contributing to national greenhouse gas emissions of 0.22 Mt CO2 eq y−1. This creates an urgent need for sustainable valorization strategies for FLW to mitigate environmental impacts. This comprehensive study analyzes the geographical distribution of FLW generation and proposes a valorization approach using WtE-AD plants. Geographic information systems were employed for geographical analysis, life cycle assessment was used for environmental evaluation, and circular economy business models were applied for sustainability assessment. The primary objective of this first part of the contribution is to evaluate the technical feasibility of implementing waste-to-energy anaerobic digestion (WtE-AD) plants for FLW management in Mexico considering their geographical locations. The results demonstrate that WtE-AD plants with treatment capacities exceeding 8 t d−1 can achieve positive energy balances and significantly reduce greenhouse gas emissions. Specific findings indicate that these plants are viable for large-scale implementation, with larger plants showing resilience to increased transport distances while maintaining energy efficiency. The results highlight the critical influence of methane yields and transport distances on plant energy performance. This study underscores the importance of strategically placing and scaling WtE-AD plants to optimize resource efficiency and environmental sustainability. These findings provide essential insights for policymakers and stakeholders advocating for the transition of Mexico’s food supply chain toward a circular economy. Future parts of this study will explore detailed economic analyses and the policy frameworks necessary for the large-scale implementation of WtE-AD plants in Mexico. Further research should continue to develop innovative strategies to enhance the techno-economic and environmental performance of WtE-AD processes, ensuring sustainable FLW management and energy recovery.

Sustainable valorization of mining waste: Phosphate sludge repurposing for advanced ceramic production

Managing the vast quantities of waste constantly generated by mining activities is one of the major environmental and economic problems facing mankind today. Fluorapatite is separated from the associated gangue minerals by a series of crushing and screening, washing, and flotation processes. These processes produce a significant amount of phosphate sludge, which is stored on the mine site in drift rock and large surface ponds. One possible environmental option is to reuse it as an alternative raw material in ceramics and building materials. Consequently, two phosphate sludges from two different Moroccan towns, Youssoufia and Khouribga, were studied. Due to the complexity of these raw materials resulting from long geological processes, in-depth physical, chemical, mineralogical, and thermal characterization is required. Dry compressed powder pellets were sintered at 900 °C, 1000 °C, and 1100 °C for 2 h. The study focuses on the effect of sintering temperature on mineralogical transformations and ceramic properties such as apparent porosity, water absorption, and mechanical strength. At 1100 °C, a slight increase in density was observed for both phosphate sludges. Water absorption was reduced by 2.51 % in both sludges for pellets sintered at 1100 °C compared to those sintered at 900 °C. Mechanical strength improved significantly, with an increase of about 60 % for samples sintered at 1100 °C, recording 227 N for Youssoufia sludge and 247 N for Khouribga sludge. This work has provided new data on the physical, chemical, mineralogical, and thermal changes in ceramics as the sintering temperature increases. These data will be useful for the manufacture of high-value ceramics.