This study explores the valorization of olive stones through the production of ZnCl2-activated biochar as carbon-based catalyst supports for CO2 methanation. The objective is to determine how biomass-to-ZnCl2 ratio and activation temperature influence the physicochemical properties of the resulting biochars and their suitability for Power-to-Methane applications. Raw olive stones were characterized by revealing high volatile matter (79 wt%), carbon content (55 wt%), and notable presence of inherent metals (K, Ca, and Na). Activation was conducted via single-step pyrolysis using ZnCl2 as a chemical activation agent, with biomass: ZnCl2 ratios of 1:4, 1:6, and 1:8, and activation temperatures of 400 , 600 , and 800 degrees C. Higher ZnCl2 ratios and activation temperatures increased carbon content and surface area (from 403 to 1409 m2 /g), enhancing porosity and adsorption capacity. Reduction studies showed weak Ni-support interactions, with Ni0 crystallite growth intensifying at higher temperatures. XPS confirmed increased electronic density around Ni, favoring catalytic activity. The CO2 methanation mechanism likely proceeds via *CO intermediates, with CO2 activation and subsequent hydrogenation as critical steps. The best-performing catalyst, 10Ni-1:6-800, achieved a CO2 conversion of approximately 20%. ZnCl2-activated biochar from agro-industrial waste shows strong potential as a value-added catalytic support for CO2 utilization, contributing to biomass valorization and the development of sustainable materials for greenhouse-gas conversion.
Marine shells constitute an abundant, renewable, and low-cost biogenic source of calcium, primarily composed of calcium carbonate (CaCO3). Although this material has been extensively studied as a sustainable resource, the incorporation of high contents of this material into borate glass systems remains insufficiently explored. In this context, this study aims to synthesize borate glasses with the composition 50B2O3-50Na2O-xShell (0 <= x <= 80 wt%, where Shell refers to marine shell powder), in which marine shell powder is used as a source of CaO, in order to investigate the effect of composition on the structural, thermal, and optical properties. The glasses were prepared using the conventional melt-quenching technique. The amorphous nature and structural modifications were confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Differential scanning calorimetry (DSC) results show a non-linear evolution of the glass transition temperature (Tg), increasing from 452 degrees C (0 wt%) to 472 degrees C (80 wt%), with a maximum value of 483 degrees C at 20%, indicating a progressive increase in network rigidity up to a critical composition, followed by structural reorganization. Density measurements reveal an increase from 2.36 to 2.56 g.cm-3 while the molar volume increases from 27.70 to 43.13 cm3 & centerdot;mol-1, indicating a modification of the glass network organization. The evolution of the N4 parameter from 0.696 to 0.771 confirms the progressive conversion of BO3 units into BO4 tetrahedral units, contributing to network strengthening. UV-Visible spectroscopy shows a variation in the optical band gap, increasing from 3.38 to 3.52 eV and then decreasing to 3.28 eV at 40 wt%, reflecting a non-linear structural behavior of the borate network.
This study investigated the effects of temperature (35 °C and 45 °C) and substrate type (potato, Chinese cabbage, radish, apple, tomato, and watermelon rind) on the production and composition of volatile fatty acids (VFAs) during anaerobic fermentation of fruit and vegetable waste. The results showed that the organic composition of each substrate substantially influenced its acidogenic performance. Apple and tomato exhibited superior acid-producing efficiency, attributable to their high organic purity (VS/TS > 0.96) and abundant soluble sugars, achieving VFA concentrations of 6858.96 ± 197.9 mg VFA/g VS and 5740.0 ± 159.33 mg VFA/g VS, respectively. Temperature had a pronounced effect on the fermentation process; at 45 °C, most substrates produced higher total VFA yields than at 35 °C, with an average increase of 25.3
This study evaluated a bioprocess using the thermo-acidophilic red microalga Galdieria sulphuraria to convert shrimp- and sludge-derived residues into biomass and pigments. Shrimp residues contained 57
Horse husbandry in Europe has shifted from agricultural production toward leisure, sport, and therapeutic uses in peri-urban areas. Consequently, horse manure has increasingly become a logistical, regulatory, and economic challenge. Controlled composting has long been recognised as a treatment option for horse manure, offering hygienisation, organic matter stabilisation, and improved nutrient predictability. However, despite its technical feasibility, composting remains underutilised in decentralised and small-to-medium horse-keeping systems. This study investigated the potential of compost-based value chains for horse manure within the EU. It combined a comparative literature analysis of horse manure composting with a systematic mapping of compost products, applications, and business models implemented across EU member states. Feedstock-specific properties of horse manure, including bedding-driven carbon-to-nitrogen ratios, emission dynamics, and hygienisation requirements, were linked to market pathways, regulatory frameworks, and organisational archetypes. Results showed that composting transforms horse manure from a disposal burden into a flexible platform for differentiated products, primarily positioned as soil improvers rather than high-effect nitrogen fertilisers. Effective value creation depends on application-driven compost formulation, process control to ensure hygienic and agronomic quality, and organisational models that match spatial context, scale, and regulatory conditions. Centralised, municipal, and decentralised business models each present distinct advantages and constraints, while product differentiation through compost-biochar blends or growing media components offers emerging opportunities. Overall, the study demonstrated that integrating compost science with business model design is essential for unlocking the economic and environmental potential of horse manure in European peri-urban systems.
