In this study, calcium oxide-magnetite (CaO-Fe₃O₄ NCs) nanocomposites were synthesized from waste inorganic biomass (snail shells) using sequential calcination, hydration, and dehydration processes. The synthesized catalyst was thoroughly characterized using various techniques, including XRD, FTIR, TGA, SEM-EDS, BET, XPS, CO₂-TPD, VSM, and ICP-OES analysis and applied for the transesterification of soybean oil to produce biodiesel. The reaction was optimized using response surface methodology, achieving a high biodiesel yield of 97.7±0.2% (98.0±0.4% conversion). The quality of the biodiesel was confirmed by comparing its physicochemical properties with ASTM standards. The transesterification reaction followed pseudo-first-order kinetics with an activation energy of 42.5 kJ mol⁻1. Furthermore, thermodynamic analysis showed that the process was endothermic (ΔH° = 39.13 kJ mol⁻1) and non-spontaneous. The catalyst was reused for up to seven reaction cycles, and the nature of the reused catalyst after the seventh cycle was thoroughly examined later in the study.

The present study examines the applicability of reaction kinetic mechanisms for predicting NOX emissions from biomass furnaces. These mechanisms are essential for numerical optimization of new innovative combustion technologies and therefore must be computationally affordable and provide reasonable accuracy in predicting NOX emissions. The selection of a suitable mechanism from literature is the goal of this work. The numerical investigations carried out utilized chemical reaction kinetic simulations with continuous stirred tank reactor networks. First, the predictions of a detailed benchmark mechanism are compared to experimental data and analyzed with regard to temperature, air-to-fuel equivalence ratio, residence time and producer gas composition. Then, various hybrid and reduced mechanisms are compared with the benchmark mechanism. The investigation showed a good agreement on the trends of NOX emissions from the detailed mechanism and measurements. The detailed mechanism can therefore be employed to find optimal operation windows in terms of temperature, air-to-fuel equivalence ratio and residence time. Benchmarking of the hybrid and reduced mechanisms showed large differences between the mechanisms. In conclusion, only one reduced mechanism is considered suitable for application in a full-scale 3D CFD simulation, which will be investigated in future studies.

New fuel production alternatives are becoming increasingly necessary to replace fossil energy sources and reduce the environmental implications of carbon emissions. In this context, renewable sources, such as waste cooking oil (WCO), are an excellent choice for producing bio-based fuels. However, to use WCO as fuel, the oxygen content in its triglyceride structures must be removed. To this end, bimetallic Co-Mo and Ni-Mo supported on pristine carbon nanotubes (CNT) and oxidized carbon nanotubes (CNTox) were synthesized to investigate the hydroprocessing of WCO in a batch reactor operating at 350 °C, 70 bar of H2 (evaluated at ambient temperature) for 3 h. The results showed that Ni-Mo/CNTox exhibited superior catalytic performance, mainly producing n-alkanes in the range of C14-C22 with a carbon conversion of about 67 mol.% and being selective for light alkanes (6.6 mol.% of C5-C7), jet fuel (11.4 mol.% of C8-C16) and diesel fuel (81.2 mol.% of C17-C22). On the other hand, a residence time of 5 h was necessary to achieve the same results with the carbon-supported Co-Mo catalysts. Hydrodeoxygenation was the main deoxygenation route followed using CNT based catalysts.

This study aimed to investigate the feasibility of hydrogen production (HP) by Clostridium butyricum NE133 from different fruit and vegetable peels (FVPs) as substrates. In addition, the kinetic parameters of hydrogen production and optimization of the anaerobic dark fermentation conditions were analyzed. Clostridium butyricum NE133 was isolated from domestic wastewater and selected as the front runner hydrogen-producer from glucose with maximum hydrogen production (Hmax) of 1778.00 ± 15.03 mL/L, maximum production rate (Rmax) of 961.95 mL/L/h and lag phase (λ) of 28.12 h. NE133 was genetically identified (accession number PP581793) and shown to harbor the Fe-Fe hydrogenase gene. This isolate showed a high potential to produce hydrogen from anaerobic fermentation of watermelon peels with Hmax of 1062.67 ± 11.92 mL/L, Rmax of 268.01mL/L/h and λ of 33.92 h. The watermelon peels were subjected to different pretreatment methods to enhance the dark fermentation by C. butyricum NE133. It was revealed that the combined physicochemical treatment (0.05 M H₂SO₄/121°C) significantly increased hydrogen yield, with 2300.33 ± 0.88 mL/L, Rmax of 1065.56 mL/L/h and λ of 22.39 h with a high accuracy of R2 (0.9999). The study emphasizes the effectiveness of using C. butyricum NE133 for sustainable biohydrogen production. The findings also indicate the feasibility of converting agricultural waste into valuable energy sources, contributing to waste management and renewable energy solutions.

In this investigation, a hydrogel has been prepared with the filling of lemon peel powder (LP) at three different concentrations of 1, 1.5, and 2 g (CS-PF/LP1, CS-PF/LP1.5, and CS-PF/LP2), in a mixture of phenol formaldehyde resin and chitosan, and they are pyrolyzed at 700°C to get soluble metal and nitrogen-doped carbon as cathode catalysts for oxygen reduction reaction (ORR). Several analytical characterization results confirmed the presence of inherent metallic content (or soluble metal) in the LP power. Among the three, CS-PF/LP1 provides the maximum surface area of 259.38 m2g-1, which is confirmed by the BET analysis. Additionally, the highest conductivity and catalytic activity of CS-PF/LP1 are also confirmed by electrochemical analysis. Thus, CS-PF/LP1 was selected to be used in a single-chamber microbial fuel cell (SCMFC) as a cathode catalyst. A maximum power density of 170.67 mWm-2 is obtained for CS-PF/LP1 which is 5.70 times higher than the base catalyst (without LP). Therefore, the present work uses LP, a waste material to develop a porous carbon material that can be used as an efficient cathode catalyst using solely the soluble metals of LP, for ORR in SCMFC for efficient power generation.

Due to large number of doors used housing and construction products, the greenhouse gas (GHG) footprint related to door manufacturing is an interesting topic. Timber and bamboo products can reduce GHG emission due to their biogenic carbon storage via photosynthesis. The scientific evidence on the climate impact using wood-based door (WBD) and bamboo-based door (BBD) to replace steel-based door (SBD) is limited. In this study, life cycle assessments for WBD, BBD, SBD were conducted to evaluate the carbon impacts of raw materials, production, transport, and end-of-life stages. The GHG footprint of WBD, BBD, and SBD ranged from 270.42–363.24, 285.31–398.31, and 983.8–986.76 kg CO2 e/m3, respectively, indicating that the bio-based doors exhibited lower energy consumption and GHG emissions. The raw material stage (484.78–569.34 kg CO2 e/m3) was identified as a major source of GHG emissions throughout the product life cycle, while hot-pressing and coating processes were identified as emission hotspots in the production stage. Regarding biogenic carbon storage, the use of bio-based materials instead of steel-based materials for fire door manufacturing significantly reduced emissions. Considering disposal methods, recycling and incineration should be prioritized over landfills. Future research should focus on field survey in raw material stage, along with conducting a technical and economic analysis. The results provide valuable guidance for selecting doors in China in term of biogenic carbon storage and resource protection.

Carbon persistence in soil is a key issue in the context of Carbon Dioxide Removal (CDR) policies and regulations: Soil Carbon Accumulation (SCA) is also included in the latest EU regulations on sustainable biofuels, and gaining attention at international level within ICAO and IMO. The long-lived nature of the durable carbon share in biochar can meet the most sever criteria set by relevant and ambitious CDR policies: however, the possibility to quantitatively assess the persistent carbon fraction in biochar has been highly debated in recent years. While lab-scale incubation experiments are intrinsically limited in providing information on long-term permanence, they do not address actual farm-scale persistence under real cultivation management practices. The deployment and combined use of recent analytical techniques allows instead to identify and quantitatively assess the persistence of the durable carbon fractions in biochar, and thus compliance of this carbon removal with the targets of CDR policies. The present work builds on one of the longest, almost unique, biochar experiments in the EU, originally developed for assessing the agronomic performances of biochar amended agricultural soil: for the first time, biochar distributed in a vineyard soil at 22 t/ha scale in 2009 was unearthed in 2024 and collected for full characterization. The agricultural soil was subject to conventional agricultural practices over the 15 years of vineyard cultivation. The scope of this research is to assess the permanence of biochar under these conditions. The present work shows the complexity of unearthing biochar from soil, applying a focused method to recover and clean the material before its characterization, without altering its chemical and physical properties. Both unearthed and original (i.e. before deployment) biochars were washed with water under same condition and procedures, and fully characterized. In addition to analytical practices commonly adopted for biochar characterization, FT-IR, SEM EDX, and Random Reflectance (Ro) techniques were used, quantifying the amount of the inertinite carbon component in biochar. Despite the dilution from the inclusion of exogeneous organic and inorganic matter from soil in the original biochar, the ratio of fixed carbon (Cfix) to total carbon (Ctot) showed minor variations (∼8%). Moreover, the inertinite and semi-inertinite fractions in the washed original and unearthed biochars remained almost unchanged over 15 years of active use in agricultural soil, confirming the permanent nature of the inertinite share of carbon in biochar. This result, together with other recent findings in literature, provides scientific evidence supporting Biochar Carbon Removals (BCRs) as permanent removal in Carbon Dioxide Removal (CDR) regulations.

The efficient cleavage of lignin's inter-unit bonds is essential for its conversion into valuable monophenols. However, conventional Ni-based catalysts often suffer from poor metal dispersion, sintering, and limited catalytic activity. In this study, a series of bimetallic Ni2M/Al2O3 (M=Fe/In/Mn/Cu/Co) catalysts were synthesized using layered double hydroxides as precursors. Among the metal promoters tested, Fe showed the highest efficacy in improving catalytic performance. NixFey/Al2O3 catalysts with varying Ni/Fe molar ratios exhibited superior activity due to the formation of Ni-Fe alloys and defect-rich FeOx species. The optimized Ni1.5Fe1.5/Al2O3 catalyst, characterized by well-dispersed small metal particles, strong Ni-Fe interactions, abundant surface oxygen vacancies, and a high density of strong acid sites, achieved a monophenol yield of 16.6 wt% from the hydrogenolysis of Klason lignin under mild reaction conditions (240°C, 4 hours, 1 MPa initial H2). This work presents a novel approach for developing highly active bimetallic catalysts for lignin depolymerization, offering insights into the design of efficient catalysts for lignin valorization.

Compositional data on vegetable biomass is widely available from research papers and online databases. However, the high diversity of biomass characteristics and composition represents a challenge for researchers and companies willing to produce novel substances from residues, and that should decide on the best and most feasible options for their use as feedstocks. The present study constructed a database with information gathered from the proximate, ultimate, and chemical composition of different biomass residues that can be used for data analysis and classification to elucidate better how they can be valorized. Different data clustering techniques were implemented to determine how compositional data can be segmented. The identified groups, that contained residues with similar characteristics, allowed to have an insight into the valorization of these biomasses, which can be used as an initial tool for biorefinery design. The use of data clustering facilitated the identification of different types of biomasses in a systematic way, which until now has not been reported in the literature.

This research aims to assess the effect of alkaline pretreatments on the antioxidant potential of β-carotene-rich extracts from the microalga Dunaliella salina and the cumulative biomethane production from its spent biomass, within the framework of a circular economy approach using four biorefineries. A solvent screening was performed, with ethyl acetate achieving the maximum β-carotene extraction yield (5.3% ± 0.03%). Alkaline pretreatments were applied to the initial biomass (direct) and extracts after a extraction with ethyl acetate (indirect), using two matrices: water (W) and a mixture water:ethanol (WE). Direct alkaline pretreatments (D) offered extracts with higher potential than indirect pretreatments (I) in terms of: i) antioxidant capacity, as measured by ABTS•+ assay (0.69±0.1 and 0.61±0.1 mmolTE/gDW for W-D and WE-D, respectively, and 0.55±0.1 and 0.53±0.1 mmolTE/gDW for W-I and WE-I, respectively) and •OH scavenging activity (1.89±0.2 and 2.05±0.5 mmolTE/gDW for W-D and WE-D, respectively, and 0.48±0 and 1.2±0.3 mmolTE/gDW for W-I and WE-I, respectively), ii) biomethane production from their spent biomass (301±14 mLCH4/gVS and 289±9.0 mLCH4/gVS for W-D and WE-D, respectively, compared to 235±57 mLCH4/gVS without alkaline pretreatment), and iii) sustainability analysis, which includes the assessment of the biomass exploitation for β-carotene extraction and biomethane production. The most sustainable biorefinery was W-D as it achieved the highest biomass exploitation (33.8%), compared to WE-D (29.1%), W-I (33.1%) or WE-I (32.8%). This underscores the novelty and effectiveness of direct alkaline pretreatments for enhancing both antioxidant potential and energy recovery from D. salina biomass in a biorefinery context.