Anca Maria Zaharioiu

This study investigated the application of biochar obtained from black liquor, a residue generated during the Kraft pulping process in the paper industry, as a sustainable soil amendment in barley (Hordeum vulgare L.) cultivation. The biochar was produced through controlled pyrolysis at 450 °C and subsequently characterized with respect to elemental composition, porosity, specific surface area, and chemical stability, confirming its suitability for agricultural use. The experiment comprised three treatments: unamended soil (control), soil supplemented with 3% biochar, and soil fertilized with NPK, all conducted under controlled growth conditions. The results showed that biochar significantly improved key soil fertility indicators, increasing cation exchange capacity from 11 to 19 cmol(+)/kg and soil organic matter from 2.1% to 2.6%. Mineral nitrogen availability increased from 7.0 mg/kg to 10.5 mg/kg in the biochar treatment compared with the control. At the plant level, biochar enhanced early barley growth, with plant height increasing from 25 cm to 27 cm and chlorophyll content rising from 32.35 SPAD units to 39 SPAD units. Although NPK fertilization produced slightly higher immediate growth responses, biochar contributed to improved soil chemical properties and nutrient retention. Overall, the results suggest that black liquor-derived biochar shows potential as a complementary soil amendment under controlled conditions.

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 paper manufacturing process produces liquid and gaseous alternative fuels, as well as solid wastes. These can be subsequently treated through chemical processing, oxidation, and thermal activation, resulting in adsorbent materials with CO2 adsorption capacities. The valorisation of black liquor waste resulting from paper manufacturing was achieved through a catalytic pyrolysis process using two catalysts previously prepared in house (Cu-Zn-MCM-41 and Ni-SBA-16). The HCl-treated adsorbent material, resulting from Ni-SBA-16-catalysed pyrolysis, was selected for use in CO2 adsorption tests as it had the highest specific surface area (224.06 m2/g) and pore volume (0.28 cm3/g). The adsorption experimental setup was linked to a gas chromatograph in order to evaluate CO2 adsorption efficiency using a binary gas mixture consisting of 81% CO2 and 19% N2. With a CO2 adsorption capacity of 1.61 mmol/g, a separation efficiency of 99.78%, and a CO2 recovery yield of 90.02%, it can be concluded that the developed adsorbent material resulting from Ni-SBA16-catalysed pyrolysis and HCl treatment represents a viable solution for black liquor pyrolytic solid waste removal and reduction in greenhouse gases.

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.

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.

Until reaching climate neutrality by attaining the EU 2050 level, the current levels of CO₂ must be mitigated through the research and development of resilient technologies. This research explored potential approaches to lower CO₂ emissions resulting from combustion fossil fuels in power plant furnaces. Different nanomaterials (MOFs versus silica nanoparticles) were used in this context to compare their effectiveness to mitigate GHG emissions. Porous materials known as metal–organic frameworks (MOFs) are frequently employed in sustainable CO₂ management for selective adsorption and separation. Understanding the underlying mechanism is difficult due to their textural characteristics, the presence of functional groups and the variation in technological parameters (temperature and pressure) during CO₂-selective adsorption. A silica-based nanomaterial was also employed in comparison. To systematically map CO₂ adsorption as a function of the textural and compositional features of the nanomaterials and the process parameters set to a column-reactor system (CRS), 160 data points were collected for the current investigation. Different scenarios, as a function of P (bar) or as a function of T (K), were designed based on assumptions, 1 and 5 vs. 1–10 (bar) and 313.15 and 373.15 vs. 313.15–423.15 (K), where the regression analyses through Pearson coefficients of 0.92–0.95, coefficients of determination of 0.87–0.90 and p-values < 0.05, on predictive and on-site laboratory data, confirmed the performances of the CRS.

Mitigating climate change is a challenge that urgently needs to be addressed, as it has an increasing impact on the planet. According to the latest reports, global CO₂ emissions must be neutralized by 2050 in order to limit the rise in temperature to 1.5 °C. This work presents the evolution of Land Use, Land Use Change and Forestry (LULUCF) greenhouse gas (GHG) emissions/removals at the EU-27 + UK level for the 1990–2019 time period, as well as LULUCF emissions/removals forecasts for Romania up to 2040. The results revealed a 23% reduction in GHG emissions for the EU-27 + UK in 2019 compared to 1990. Romania’s yearly average of GHG emissions/removals was 28,000 kt CO₂ eq., representing roughly 9.7% of the EU’s annual average. In terms of projections for Romania, the only scenario that will not be in the target set by the new LULUCF Regulation is WEM (Reference Scenario/With Existing Measures), in which net GHG removals will be reduced by approximately 218 kt CO₂ eq., or 0.9 percent, in 2030 compared to the reference year; in 2040 compared to 1989, the trend will be accentuated both in absolute values, with a decrease of over 3000 kt CO₂ eq., and in relative values of 12%.

The capitalization of agri-food waste is essential for the sustainability of a circular economy. This work focuses on a solution to eliminate such waste, meat and bone meal (MBM), which is produced in large quantities by the food industry and is prohibited for use as animal feed under the European directives. Therefore, with the focus of converting waste to energy, the catalytic pyrolysis of MBM in the presence of mesoporous silica nanocatalysts (SBA-3 and SBA-16 materials and metallic derivates) was investigated in a home-made reactor for the production of renewable energy. The mesoporous silica materials were synthesized using relatively simple methods and then characterized in order to determine their morpho-structural characteristics. The MBM pyrolysis behavior under different experimental conditions was examined in detail, both in the presence and absence of the new catalysts. The resulting MBM-based pyrolysis products, MBM_PYOILs and MBM_PYGASs, were also assessed as potential alternative fuels, highlighting comparable energy values to conventional fuels. The outcomes of this investigation offer a potential pathway to the clean production of gas and oil, thus promoting the high-grade utilization of MBM waste.

The study tried to contribute to solving two serious environmental issues: CO₂ reducing and sewage sludge disposal. Thus, sewage-sludge-derived materials were obtained in order to be evaluated for CO₂ adsorption capacity. Therefore, the char resulted after the sewage sludge pyrolysis was subjected to oxidation and chemical activation processes by using different quantities of alkaline hydroxide. One of the obtained materials, activated with a lower quantity of alkaline hydroxide, was also treated with acid chloride. Further, the materials were structural and texturally characterized, and material treated with acid chloride was used for CO₂ adsorption tests, due to high surface area and pore volume. The handmade system coupled to a gas chromatograph allowed the adsorption efficiency evaluation using different feed gases (rich and poor in CO₂) by completed purge of pipe line and on-line check. Additionally, the adsorption capacity, separation efficiency, and CO₂ recovery were calculated. Taking into account the values for adsorption capacity (separation efficiency and CO₂ recovery), it can be concluded that the sewage sludge derived material could be a promising solution for CO₂ reduction and waste disposal.

Marius Constantinescu, Felicia Bucura, Eusebiu Ilarian Ionete, Daniela Ion-ebrasu,claudia Sandru, Anca Zaharioiu, Florian Marin, Marius Gheorghe Miricioiu, Violeta Carolina Niculescu, Simona Oancea, Roxana Elena Ionete - From Plastic to Fuel - New Challenges