Soil degradation, declining fertility, and rising greenhouse gas emissions highlight the urgent need for sustainable soil management strategies. Among them, biochar has gained recognition as a multifunctional material capable of enhancing soil fertility, sequestering carbon, and valorizing biomass residues within circular economy frameworks. This review synthesizes evidence from 186 peer-reviewed studies to evaluate how feedstock diversity, pyrolysis temperature, and elemental composition shape the agronomic and environmental performance of biochar. Crop residues dominated the literature (17.6%), while wood, manures, sewage sludge, and industrial by-products provided more targeted functionalities. Pyrolysis temperature emerged as the primary performance driver: 300–400 °C biochars improved pH, cation exchange capacity (CEC), water retention, and crop yield, whereas 450–550 °C biochars favored stability, nutrient concentration, and long-term carbon sequestration. Elemental composition averaged 60.7 wt.% C, 2.1 wt.% N, and 27.5 wt.% O, underscoring trade-offs between nutrient supply and structural persistence. Greenhouse gas (GHG) outcomes were context-dependent, with consistent Nitrous Oxide (N₂O) reductions in loam and clay soils but variable CH₄ responses in paddy systems. An emerging trend, present in 10.6% of studies, is the integration of artificial intelligence (AI) to improve predictive accuracy, adsorption modeling, and life-cycle assessment. Collectively, the evidence confirms that biochar cannot be universally optimized but must be tailored to specific objectives, ranging from soil fertility enhancement to climate mitigation.

The valorization of black liquor, a by-product produced in considerable quantities from the paper manufacturing processes, has demonstrated the effectiveness of thermal reconversion into pyrolysis gas, bio-oil, and bio-char, a sustainable approach placing the feedstock into a circular economy concept. The present study focused on developing disposal solutions through energy recovery via pyrolysis at 300 °C and 450 °C when lignite and nanomaterials (such as Cu-Zn-MCM-41, Ni-SBA-3, or Ni-SBA16) were used as catalysts. The results were compared to those of non-catalytic pyrolysis. The use of the Cu-Zn-MCM-41 catalyst proved to be efficient for pyrolysis gas production, reaching 55.22 vol% CH₄. The increase in the calorific value of the pyrolysis gas was associated with the use of the Cu-Zn-MCM-41, showing a value of 42.23 MJ/m³ compared to that of the non-catalytic process, which yielded 39.56 MJ/m³. The bio-oil resulting from the pyrolysis with Cu-Zn-MCM-41 showed the highest energy value at 6457 kcal/kg compared to that obtained with the other two nanocatalysts, Ni-SBA-3 and Ni-SBA-16, as well as that of the raw material, which had a value of 3769 kcal/kg. The analysis of bio-char revealed no statistically significant differences when comparing the outcomes from using the various nanocatalysts, suggesting their minimal impact on the energy content.

This study presents the development and implementation of an AI-driven control system for dynamic regulation of hydrogen blending in natural gas networks. Leveraging supervised machine learning techniques, a Random Forest Classifier was trained to accurately identify the origin of gas blends based on compositional fingerprints, achieving rapid inference suitable for real-time applications. Concurrently, a Random Forest Regression model was developed to estimate the optimal hydrogen flow rate required to meet a user-defined higher calorific value target, demonstrating exceptional predictive accuracy with a mean absolute error of 0.0091 Nm³ and a coefficient of determination (R²) of 0.9992 on test data. The integrated system, deployed via a Streamlit-based graphical interface, provides continuous real-time adjustments of gas composition, alongside detailed physicochemical property estimation and emission metrics. Validation through comparative analysis of predicted versus actual hydrogen flow rates confirms the robustness and generalizability of the approach under both simulated and operational conditions. The proposed framework enhances operational transparency and economic efficiency by enabling adaptive blending control and automatic source identification, thereby facilitating optimized fuel quality management and compliance with industrial standards. This work contributes to advancing smart combustion technologies and supports the sustainable integration of renewable hydrogen in existing gas infrastructures.

Climate neutrality for the year 2050 is the goal assumed at the level of the EU_27+UK. As Romania is no exception, it has assumed the gradual mitigation of pollution generated by the energy sector, and by 2030, according to ‘Fit for 55’, the share of energy from renewable sources must reach 42.5% from total energy consumption. For the rest of the energy produced from traditional sources, natural gas and/or coal, modern technologies will be used to retain the gaseous noxes. Even if they are not greenhouse gases, NO and SO₂, generated from fossil fuel combustion, cause negative effects on the environment and biodiversity. The adsorption capacity of different materials, three nanomaterials developed in-house and three commercial adsorbents, both for NO and SO₂, was tackled through gas chromatography, elemental analysis, and Fourier-transform infrared spectroscopy. Fe-BTC has proven to be an excellent material for separation efficiency and adsorption capacity under studied conditions, and is shown to be versatile both in the case of NO (80.00 cm³/g) and SO₂ (63.07 cm³/g). All the developed nanomaterials generated superior results in comparison to the commercial adsorbents. The increase in pressure enhanced the performance of the absorption process, while temperature showed an opposite influence, by blocking the active centers on the surface.

Apple pomace represents an important agro-industrial residue with high moisture content and significant environmental burden if improperly managed. This study investigated its thermochemical valorisation into biochar via two processes, followed by comprehensive physicochemical characterization and agronomic evaluation. Elemental analysis revealed carbon enrichment from 47.89% in raw material to 77–78% after the thermal process, evidencing a progressive aromatization. Scanning electron microscopy, Fourier transform infrared spectroscopy, and Raman analysis confirmed a temperature-dependent transition from partially amorphous carbon (400 °C) to more ordered aromatic structures (450 °C), while excessive thermal treatment (550 °C) increased structural defects. ICP-OES revealed an enrichment in thermally stable metals (Fe, Al, Mn) and limited Cd accumulation. Germination assays using Triticum aestivum L. demonstrated that biochar produced at 400 °C significantly improved the germination uniformity and seedling height (14.1 mm), as well as biomass accumulation compared to the control soil sample. The fertilizer addition increased the soluble Na and electrical conductivity (up to 643 µS/cm), potentially inducing transient salinity stress. Soil chemical analysis indicated increased K availability in soils amended with biochar produced at 400 °C, whereas the combination of biochar obtained at 450 °C with fertilizer conducted to elevated concentrations of certain trace metals, mainly Ni and Cr, highlighting the demand for careful monitoring. Overall, the biochar produced at 400 °C yielded to an optimal balance between structural stability, nutrient enrichment, and agronomic performance, evidencing that apple pomace may be a viable feedstock for sustainable biochar production within circular bioeconomy frameworks.

National greenhouse gas inventories commonly apply a single enteric methane emission factor to an entire dairy population, which can obscure meaningful differences between production systems and between feeding seasons. An IPCC Tier 2 assessment was performed for the Romanian dairy herd in the reference year 2024 (1,051,894 cows), stratified into extensive (72.77%), semi-intensive (23.10%), and intensive (4.12%) systems and, for the two grazing-based systems, into a winter indoor and a summer grazing period. Gross energy intake (GE), digestible energy (DE), and the methane conversion factor (Y_m) were derived from national feed composition references, with Y_m estimated from DE using a regression equation. Season-specific emission factors were combined into day-weighted annual values. GE ranged from 153.60 MJ head⁻¹ day⁻¹ to 387.78 MJ head⁻¹ day⁻¹ and Y_m from 5.48% (semi-intensive, grazing) to 6.44% (extensive, indoor). Day-weighted annual emission factors were 144.37 kg CH₄ head⁻¹ year⁻¹, 108.17 kg CH₄ head⁻¹ year⁻¹ and 81.92 kg CH₄ head⁻¹ year⁻¹ for the intensive, semi-intensive, and extensive systems, whereas methane intensity declined in the opposite direction, from 25.32 g CH₄ kg⁻¹ FPCM to 19.98 g CH₄ kg⁻¹ FPCM. National enteric emissions were estimated at 95,260 t CH₄ (2,572,014 t CO₂-eq), 65.8% of which originated from the extensive system. Sensitivity analysis showed that national emissions were more sensitive to gross energy intake (±10% change in emissions for a ±10% change in GE intake) than to digestible energy (±4.3–4.8% change for a ±2 percentage-point change in DE). These results suggest that the methane-related environmental ranking of Romanian dairy systems depends strongly on the functional unit considered and that seasonal variation in Y_m is comparable in magnitude to differences between production systems.