Tannery waste-derived biochar as a carrier of micronutrients essential to plants

Effect of granulated biochar sphere on mineral nutrients in removing potentially toxic elements from contaminated agricultural soils

Biochar (BC) granulation, yielding BC-based spheres, serves as an eco-friendly, cost-effective and efficient adsorbent for the removal of potential toxic elements (PTEs) from contaminated agricultural soils. The effect of BC-based spheres on mineral nutrients while effectively removing PTEs from contaminated soils is worth investigating. In this study, we utilized natural clay minerals, magnetic minerals and BC to produce water-hardened magnetic composite biochar sphere (WMBCS) that was capable of removing PTEs from composite contaminated agricultural soils. We explored the effect of WMBCS on minerals (Al, Ca, Fe, Mn, Na, Mg, Si, K, P, NH4+, and NO3-) in the removal of soil PTEs. WMBCS was a mineral nutrient-rich, recyclable, alkaline BC-based sphere that removes Cd (23.07-29.20 %), Pb (27.68-31.10 %), and As (26.17-37.48 %) from soils after three regeneration cycles. The effect of WMBCS on mineral nutrients varies depending on element type, BC and soil type. Compared to water-hardened magnetic composite phosphate modified biochar spheres (WMPBCS), water-hardened magnetic composite unmodified biochar spheres (WMUBCS) had more significant effect on Ca, Mg, Mn, Al and NH4+ in alkaline soils, but a greater effect on Ca, Mg, Mn, Fe and NO3- in acidic soils. Additionally, WMBCS displayed a more pronounced impact on mineral nutrients in alkaline soils than in acidic soils. The application of WMBCS reduced the accumulation of PTEs in wheat (18.40-84.70 %) and rice (27.96-88.66 %), but significantly inhibited seed germination and altered the uptake of mineral nutrients by seedlings due to its effects on soil physicochemical properties and mineral nutrient dynamics. Overall, WMBCS is suitable as a potential amendment for the remediation of soils co-contaminated with Cd, As, and Pb, but its effects on mineral nutrients cannot be overlooked, particularly in agricultural soils.

Lignocellulosic biomass fertilizers: Production, characterization, and agri-applications

The growing focus on sustainable agriculture and optimal resource utilization has spurred investigations into lignocellulosic biomass as a potential source for producing environmentally friendly fertilizers. This paper reviews recent advancements in the production and application of innovative fertilizers derived from lignocellulose. It highlights potential in enhancing agricultural productivity and reducing environmental impacts such as carbon footprint and water pollution. The paper outlines various methods for conversion, highlighting the unique advantages of chemical, enzymatic, and microbiological processes, for converting lignocellulosic biomass into nutrient-rich fertilizers. The study compares the efficacy of lignocellulosic fertilizers to traditional fertilizers in promoting crop growth, enhancing soil health, and reducing nutrient losses. The results demonstrate the potential of lignocellulosic biomass-derived fertilizers in promoting resource efficiency and sustainable agriculture. While this research significantly contributes to the existing body of knowledge, further studies on long-term impacts and scalability are recommended for the development of innovative and sustainable agricultural practices.

Maximizing the potential of leachate from sewage sludge as a sustainable nutrients source to alleviate the fertilizer crisis

Leachate from separate digesters in biological wastewater treatment plants contains valuable biogenic compounds that can serve as fertilizer nutrients. In this study, a method was developed to utilize leachate from sewage sludge dewatering as a raw material for the preparation of a plant conditioner, providing water, nutrients, and growth-stimulating amino acids. A chemical conditioning procedure (65% HNO₃) was used to prepare the leachate solution for fertilization. The feasibility of producing an amino acid-based fertilizer using shrimp shells and inorganic acids (96% H₂SO₄ and 85% H₃PO₄) was also demonstrated. Microbiological analysis confirmed the safety of the formulations, and chelation of micronutrients with available amino acids was proven (up to 100% chelating degree). The bioavailability of all nutrients was confirmed through extraction tests (extraction in neutral ammonium citrate). Germination tests showed similar fresh plant masses to those with commercial preparations, demonstrating the effectiveness of the developed technology. This approach aligns with circular economy principles and sustainable development and contributes to mitigating the impacts of climate change.

Carbonized Leather Waste: A Review and Conductivity Outlook

The carbonization of collagen-based leather waste to nitrogen-containing carbon is reviewed with respect to the preparation, characterization of carbonized products, and applications proposed in the literature. The resulting nitrogen-containing carbons with fibrous morphology have been used as adsorbents in water pollution treatment, in electrocatalysis, and especially in electrodes of energy-storage devices, such as supercapacitors and batteries. Although electrical conductivity has been implicitly exploited in many cases, the quantitative determination of this parameter has been addressed in the literature only marginally. In this report, attention has been newly paid to the determination of conductivity and its dependence on carbonization temperature. The resulting powders cannot be compressed into pellets for routine conductivity determination. A new method has been used to follow the resistivity of powders as a function of pressure up to 10 MPa. The conductivity at this pressure increased from 9.4 × 10^-8 S cm^-1 for carbonization at 500 °C to 5.3 S cm^-1 at 1000 °C. The conductivity of the last sample was comparable with conducting polymers such as polypyrrole. The carbonized leather thus has the potential to be used in applications requiring electrical conduction.

Sufficient extraction of Cr from chromium ore processing residue (COPR) by selective Mg removal

Chromium ore processing residue (COPR) is a hazardous waste generated during the production of chromate. Currently, approximately 10% of Cr₂O₃ cannot be extracted after chromite sodium roasting and remains in COPR, wasting valuable Cr resources. In this study, Mg was selectively removed by using (NH₄)₂SO₄ roasting in combination with H₂SO₄ leaching. The results showed that the selective removal of 79.55% Mg from COPR could be achieved under the optimum (NH₄)₂SO₄ roasting conditions (80 mmol (NH₄)₂SO₄, 800 °C, 2 h). During the subsequent sodium roasting and acid leaching stages, the Cr extraction rate was 84.63% for the COPR direct roasting and 95.39% for the Mg removal residue roasting. The increased Cr extraction efficiency is attributed to the transformation of Mg-rich spinel and diopside (the Mg & Cr coexisting phases) in COPR converted into easily extractable (Fe,Cr)₂O₃ and Cr₂O₃ after the Mg treatment. This study investigated that the phase transformation of the Cr host phases is crucial for the sufficient extraction of Cr and provides inspiration for the development of efficient and practical Cr extraction techniques. Moreover, the method can be extended to the effective extraction of Cr from other Cr-containing wastes.