Search Results (59)

This study presents an innovative approach to the production of hydrogen from liquids following hydrothermal treatment of biowaste, offering a potential solution for renewable energy generation and waste management. By combining biological and hydrothermal processes, the efficiency of H₂ production can be significantly improved, contributing to a reduced carbon footprint and lower reliance on fossil fuels. The inoculum used was fermented sludge from a wastewater treatment plant, which had been thermally pretreated to enhance microbial activity towards hydrogen production. Kitchen waste, consisting mainly of plant-derived materials (vegetable matter), was used as a substrate. The process was conducted in batch 1-L bioreactors. The results showed that higher pretreatment temperatures (up to 180 °C) increased the hydrolysis of compounds and enhanced H₂ production. However, temperatures above 180 °C resulted in the formation of toxic compounds, such as catechol and hydroquinone, which inhibited H₂ production. The highest hydrogen production was achieved at 180 °C (approximately 66 mL H₂/g_TVSKW). The standard Gompertz model was applied to describe the process kinetics and demonstrated an excellent fit with the experimental data (R² = 0.99), confirming the model’s suitability for optimizing H₂ production. This work highlights the potential of combining hydrothermal and biological processes to contribute to the development of sustainable energy systems within the circular economy. Full article

Catalytic methane decomposition (CMD) is an environmentally friendly method of hydrogen production that, unlike other conventional processes, such as steam methane reforming, partial oxidation of methane, and dry reforming of methane, can convert methane into hydrogen with a simultaneous generation of solid carbon without CO₂ emissions. This study mainly focused on the application of carbon-based catalysts derived from biomass and biowaste for the CMD process. For this purpose, eight catalysts were produced from three carbon materials (wood, sewage sludge, and digestate) through the subsequent processes of pyrolysis, leaching, and physical activation. The comparison of catalysts prepared from the slow pyrolysis of biowaste and wood indicated that carbon materials with a lower ash content achieved a higher initial methane conversion (wood char > digestate char > sewage sludge char). For feedstocks with a high initial ash content, such as digestate and sewage sludge chars, an improvement in the catalytic activity was observed after ash removal through the leaching process with HNO₃. In addition, physical activation through CO₂ fluxing led to an enhancement in the BET surface area of these catalysts, and consequently to a growth in methane conversion. The initial methane conversion was assessed for all chars under operating conditions of 900 °C, a gas hourly space velocity (GHSV) of 3 L/g/h, and a CH₄:N₂ ratio of 1:9, and it was 65.9, 59.1, and 42.6% v/v, respectively, for chars derived from wood, sewage sludge, and digestate; these values increased to almost 80% v/v when these chars were upgraded by chemical leaching and physical activation. Full article

Conventional methods for the synthesis of porous carbons are typically time- and energy-consuming and often contribute to the excessive accumulation of waste solvents. An alternative approach is to employ environmentally friendly procedures, such as mechanochemical synthesis, which holds great potential for large-scale production of advanced carbon-based materials in coming years. This review covers mechanochemical syntheses of highly porous carbons, with a particular focus on new adsorbents and catalysts that can be obtained from biomass. Mechanochemically assisted methods are well suited for producing highly porous carbons (e.g., ordered mesoporous carbons, hierarchical porous carbons, porous carbon fibers, and carbon–metal composites) from tannins, lignin, cellulose, coconut shells, nutshells, bamboo waste, dried flowers, and many other low-cost biomass wastes. Most mechanochemically prepared porous carbons are proposed for applications related to adsorption, catalysis, and energy storage. This review aims to offer researchers insights into the potential utilization of biowastes, facilitating the development of cost-effective strategies for the production of porous carbons that meet industrial demands. Full article

To ensure agricultural safety and ecological security, it is crucial to effectively immobilize emerging organic pollutants, such as plasticizers, to prevent their migration in various environmental matrices. However, the ideal immobilization agent with the advantages of being environmentally friendly is very rare. In this study, low-cost and stable near-natural immobilization agents, char-derived artificial humic acids, CHAs, were proposed and prepared via hydrothermal humification (180 °C) and pyrolysis (300, 500, or 700 °C) of agroforestry biowaste. The resulting CHAs exhibit high purity (composed primarily of C (67.28–81.35%), O (6.65–21.64%), H (1.40–5.28%), and N (0.36–0.58%)) with remarkably low ash content (5.43–10.02%). Characterization revealed a compact structure with a limited porosity with small surface area (0.27–0.32 m² g⁻¹) and pore volume (2.99–3.43 × 10⁻⁴ cm³ g⁻¹). Notably, high-temperature pyrolysis induced consumption of oxygen-containing functional groups while promoting aromatic structure formation. The sorption behavior of diethyl phthalate, a representative plasticizer, on CHAs was well described by both Langmuir isotherm and pseudo-second-order kinetic models. The CHAs exhibited remarkable sorption performance for diethyl phthalate, with a maximum sorption capacity reaching 3345 mg kg⁻¹ as determined by the Langmuir model. The sorption of diethyl phthalate onto CHAs is mainly multi-layer sorption dominated by physical processes, mainly including pore filling, partitioning, hydrogen bonding, and π–π stacking. Mean sorption energies ranging from 2.56 to 4.99 × 10⁻³ kJ mol⁻¹ indicate the predominance of physical sorption mechanisms. This study developed a method to convert the liquid by-product produced during hydrothermal humification of biowaste into stable near-natural and carbon-rich char materials, and the proposed materials show great promise in immobilizing pollutants from various environmental matrices. Full article

Waste cooking oils (WCOs) are generated globally in significant amounts by various sectors including hospitality, households, and industrial operations. Many nations currently lack dedicated legislation for managing WCOs, creating a pressing environmental challenge. At present, WCOs are primarily utilized in industries as raw materials for biodiesel production and energy generation. However, their role in second-generation biodiesel production is contingent on availability, often necessitating imports of either biodiesel or WCOs from other countries. The European Union has emphasized the importance of prioritizing biowaste for high-value alternative products beyond biodiesel to achieve carbon neutrality by 2050. Many reviews have been published in the literature reporting potential WCO applications to produce biolubricants, biosolvents, animal feed, asphalt additives, among others, however, no detailed analysis of industrial trends has ever been presented. Within this panorama, unlike existing reviews that focus on specific polymer classes derived from WCOs, this work sought to present a comprehensive industrial overview of the use of WCOs in creating high-value polymeric materials beyond fuel and energy, providing a general overview of patents published (or alive) in the last 10 years, together with the analysis of which innovative products are being introduced and sold on the market today. Full article

Carbon nanostructures are highly promising materials for applications in a variety of different fields. Besides their interesting performances, the possibility to synthesize them from biowaste makes them an eco-friendly resource widely exploitable within a circular economy context. The present work deals with the green, one-pot synthesis of graphene quantum dots (GQDs) from carbon aerogels (CAs) derived from rice husk (RH). After having obtained CAs upon purification of RH, followed by gelification and carbonization of the resulting cellulose, the one-pot solventless production of GQDs was obtained by ball milling. This method determined the formation of crystalline nanostructures with a diameter of around 20 nm, which were analyzed via scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction, and Raman spectroscopy to obtain a full morphological and structural characterization. GQDs were used as electrode materials for supercapacitors and Li-ion batteries, showing the ability to both accumulate charges over the surface and intercalate lithium-ions. The reported results are a proof of principle of the possibility of exploiting GQDs as support material for the development of advanced systems for energy storage. Full article

Nowadays, there is increasing global demand for activated carbon considering its wide usage as an adsorbent of environmental pollutants. Biowaste rich in lignocellulose, like the cone-like flowers of black alder (A_AC), shows promise as a precursor for novel materials. Building upon previous research and this material’s established applicability for removing cyanobacteria cells and cyanotoxins from water, this study investigates the CNOHS composition of A_AC and its potential to inhibit biofilm formation. A comprehensive CNOHS analysis showed the material composition as 64.5%, 1.77%, 28.83%, 2.05%, and 0.12% for C, N, O, H, and S respectively. The material’s efficacy in inhibiting biofilm formation across eight selected bacterial strains was evaluated. The results showed biofilm formation rates of 62.6%, 22.1%, 73.8%, 12.1%, 40.9%, 24.2%, 9.2%, and 7.6% for Escherichia coli, Pseudomonas aeruginosa, Enterobacter cloacae, Salmonella Typhimurium, Proteus mirabilis, Klebsiella pneumoniae, Acinetobacter baumannii, and Enterococcus faecalis, respectively. Biofilm formation is influenced by biotic and abiotic factors, especially the physicochemical properties of the substrate. This study offers insights into the potential of black-alder-derived activated carbon to prevent biofilm formation, highlighting its role in water purification and environmental protection. Full article

Anaerobic digestion is a feasible solution for the treatment of organic wastes. The process can reduce the amount of biowaste by stabilizing the organic material and producing biogas susceptible to energetic valorization. However, the digestate needs further valorization when land application is considered unfeasible. Thermal treatments, such as gasification, pyrolysis, and hydrothermal carbonization, are alternatives capable of transforming this material into valuable syngas, obtaining, in many cases, a carbonized stream known as biochar. The feasibility of the process depends on the energy demand for the drying stage and the treatments available for removing contaminants from the syngas, attaining high-quality products, and treating the process-derived water. In the present manuscript, these critical aspects were reviewed considering the characteristics of digestates based on their origin, the modifications of this material during anaerobic digestion, and the way digestate structure affects the final thermal valorization outcome. Emphasis was placed on the energy demand of the global approach and byproduct treatments. Full article

Exploring high-performance carbon anodes that are low-cost and easily accessible is the key to the commercialization of sodium-ion batteries. Producing carbon materials from bio by-products is an intriguing strategy for sodium-ion battery anode manufacture and for high-value utilization of biomass. Herein, a novel hard carbon (PPHC) was prepared via a facile pyrolysis process followed by acid treatment using biowaste pomegranate peel as the precursor. The morphology and structure of the PPHC were influenced by the carbonization temperature, as evidenced by physicochemical characterization. The PPHC pyrolyzed at 1100 °C showed expanded interlayer spacing and appropriate oxygen group content. When used as a sodium ion battery anode, the PPHC-1100 demonstrated a reversible capacity of up to 330 mAh g⁻¹, maintaining 174 mAh g⁻¹ at an increased current rate of 1 C. After 200 cycles at 0.5 C, the capacity delivered by PPHC-1100 was 175 mAh g⁻¹. The electrochemical behavior of PPHC electrodes was investigated, revealing that the PPHC-1100 possessed increased capacitive-controlled energy storage and improved ion transport properties, which explained its excellent electrochemical performance. This work underscores the feasibility of high-performance sodium-ion battery anodes derived from biowaste and provides insights into the sodium storage process in biomass-derived hard carbon. Full article

Biopolymers are highly desirable alternatives to petrochemical-based plastics owing to their biodegradable nature. The production of bioplastics, such as polyhydroxyalkanoates (PHAs), has been widely reported using various bacterial cultures with substrates ranging from pure to biowaste-derived sugars. However, large-scale production and economic feasibility are major limiting factors. Now, using algal biomass for PHA production offers a potential solution to these challenges with a significant environmental benefit. Algae, with their unique ability to utilize carbon dioxide as a greenhouse gas (GHG) and wastewater as feed for growth, can produce value-added products in the process and, thereby, play a crucial role in promoting environmental sustainability. The sugar recovery efficiency from algal biomass is highly variable depending on pretreatment procedures due to inherent compositional variability among their cell walls. Additionally, the yields, composition, and properties of synthesized PHA vary significantly among various microbial PHA producers from algal-derived sugars. Therefore, the microalgal biomass pretreatments and synthesis of PHA copolymers still require considerable investigation to develop an efficient commercial-scale process. This review provides an overview of the microbial potential for PHA production from algal biomass and discusses strategies to enhance PHA production and its properties, focusing on managing GHGs and promoting a sustainable future. Full article

Ecofuels and their feedstock come in three main product classes: electrofuels (e-Fuels), biofuels, and non-biowaste-derived fuels. Ecofuels originate from non-fossil sources, derived from circular raw materials such as non-food organic waste, renewable hydrogen, and captured CO₂ through a rapid process of carbon fixation. Proposed regulation drafts under discussion indicate that new fuels would need to reach a substantial degree of climate neutrality. The manufacture of all ecofuels, however, requires energy input to accomplish the conversion of the initial feedstock; their climate neutrality claims stem from the use of renewable electric energy and/or biomasses in the production process, but fossil fuels are still the main primary sources of global (and the EU’s) electric power, and most biofuels consumed in the EU transport mix are still crop-based, with potential conflicts with food and land use. Furthermore, entirely neglecting GHG emissions from renewable energy generation is scientifically debatable, as the impact of the energy (and the related GHG emissions) embedded in the materials used to build renewable energy facilities is small, but not nil. The paper reports ecofuel trends according to the above-mentioned originating technologies and discusses the issues related to their development. Full article

Harmful cyanobacteria blooms and the escalating impact of cyanotoxins necessitates the effective removal of cyanobacteria from water ecosystems before they release cyanotoxins. In this study, cyanobacteria removal from water samples taken from the eutrophic Aleksandrovac Lake (southern Serbia) was investigated. For that purpose, novel activated carbons derived from waste biomass—date palm leaf stalk (P_AC), black alder cone-like flowers (A_AC), and commercial activated carbon from coconut shell (C_AC) as a reference were used. To define the best adsorption conditions and explain the adsorption mechanism, the influence of contact time, reaction volume, and adsorbent mass, as well as FTIR analysis of the adsorbents before and after cyanobacteria removal, were studied. The removal efficiency of P_AC and A_AC achieved for the applied concentration of 10 mg/mL after 15 min was ~99%, while for C_AC after 24 h was only ~92% for the same concentration. To check the safety of the applied materials for human health and the environment, the concentrations of potentially toxic elements (PTEs), the health impact (HI) after water purification, and the toxicity (MTT and Comet assay) of the materials were evaluated. Although the P_AC and A_AC achieved much better removal properties in comparison with the C_AC, considering the demonstrated genotoxicity and cytotoxicity of the P_AC and the higher HI value for the C_AC, only the A_AC was further investigated. Results of the kinetics, FTIR analysis, and examination of the A_AC mass influence on removal efficiency indicated dominance of the physisorption mechanism. Initially, the findings highlighted the superior performance of A_AC, with great potential to be globally commercialized as an effective cyanobacteria cell adsorbent. Full article

The field of material sciences has evolved vastly in the last two decades, largely due to the discovery of carbon nanomaterials such as graphene and its derivatives. Although they offer positive characteristics, the cost of production and material processing of these carbon nanomaterials has limited their application. However, scientists have started searching for cheaper and more environmentally friendly alternatives. Biochar, a carbonaceous material derived from biowaste, is the most viable alternative, as it offers characteristics on par with traditional carbon nanomaterials. This review will discuss the production of biochar from biomass, methods of production, the effects various conditions have on the production of biochar, biomass selection, current biochar applications, and the potential biochar has to produce hydrogen as an energy carrier. Full article

Graphene-based materials have been widely studied in the field of supercapacitors. However, their electrochemical properties and applications are still restricted by the susceptibility of graphene-based materials to curling and agglomeration during production. This study introduces a facile method for synthesizing reduced graphene oxide (rGO) nanosheets and activated carbon based on olive stones (OS) with polyaniline (PAni) surface decoration for the development of supercapacitors. Several advanced techniques were used to examine the structural properties of the samples. The obtained PAni@OS−rGO (1:1) electrode exhibits a high electrochemical capacity of 582.6 F·g⁻¹ at a current density of 0.1 A·g⁻¹, and an energy density of 26.82 Wh·kg⁻¹; thus, it demonstrates potential for efficacious energy storage. In addition, this electrode material exhibits remarkable cycling stability, retaining over 90.07% capacitance loss after 3000 cycles, indicating a promising long cycle life. Overall, this research highlights the potential of biomass-derived OS in the presence of PAni and rGO to advance the development of high-performance supercapacitors. Full article

The paper discusses the perspectives of further implementation of the autocatalytic properties of a soluble biopolymer (SBP) derived from municipal biowastes for the realisation of a biorefinery producing value-added bio-products for consumer use. The reaction of an SBP and water is reported to cause the depolymerisation and oxidation of the pristine SBP organic matter with the formation of carboxyl-functionalised polymers having lower molecular weight and CO₂. These findings demonstrate the oxidation of the SBP via water, which could only occur through the production of O and OH radicals catalysed by the SBP. According to the adopted experimental plan, the anaerobic digestate supplied by an Italian municipal biowaste treatment plant was hydrolysed in pH 13 water at 60 °C. The dry product was re-dissolved in plain water at pH 10 and used as a control against the same solution with hydrogen peroxide at 0.1–3 H₂O₂ moles per SBP carbon mole added. The control and test solutions were kept at room temperature, in the dark or in a climatic chamber under irradiation with simulated solar light, until the pH of the solutions remained constant. Afterwards, the solutions were processed to recover and analyse the crude soluble products. The present work reports the results obtained for the control solution and for the test solutions treated in the presence and absence of H₂O₂, with and without pH control, in the dark and under irradiation with simulated solar light. Full article