Sewage sludge is an effective fertilizer in many soil types. When applied as an amendment, sludge introduces, in addition to organic matter, plant nutrients into the soil. When applied for cropland as a fertilizer, the mass loading of sewage sludge is customarily determined by inputs of N and/or P required to support optimal plant growth and a successful harvest. This study aims to examine the changes in organic matter contents and nitrogen forms in sludge-amended soils, as well as the growth of corn and faba bean plants. The main results indicated that there were higher responses to the corn and faba bean yields when sludge was added. Levels of organic carbon in soil were higher after maize harvest and decreased significantly after harvesting of beans, and were higher in sludge amended soils than unmodified soils, indicating the residual effect of sludge in soil. NO₃⁻-N concentrations were generally higher in the soil after maize harvest than during the plant growth period, but this trend was not apparent in bean soil. The amounts of NH₄⁺-N were close in the soil during the growth period or after the maize harvest, while they were higher in the soil after the bean harvest than they were during the growth period. Total nitrogen amounts were statistically higher in the soil during the growth period than those collected after the corn harvest, while they were approximately close in the bean soil. The total nitrogen amount in corn and bean leaves increased significantly in plants grown on modified sludge soil. There were no significant differences in the total nitrogen levels of the maize and beans planted on the treated soil.

Environmental pollution is a global phenomenon and troublesome fact that poses a grave risk to all living entities. Via coupling carbonaceous feedstocks with outstanding microbial activity, kinetic experiments were established using the consortium of Proteus mirabilis and Raoultella planticola, biochar-derived sunflower seed husk (SHB) and rice straw (RSB), and their composites, which investigated at 30 °C (150 rpm) to eliminate 700 mg L⁻¹ lead (120 h) and phenol (168 h) from synthetic wastewater. The derived biochars physicochemical properties of were studied. According to adsorption capacity (q_e), consortium-SHB composites and consortium-RSB composites removed lead completely (70 mg g⁻¹) within 48 h and 66 h, respectively. Besides, phenol was remediated entirely after 42 h and 48 h by both composite systems (69.90 mg g⁻¹), respectively, comparing with bacterial consortium only or parent SHB and RSB. Moreover, four kinetic models were studied to describe the bioremediation process. Fractional power and Elovich models could be recommended for describing the adsorption kinetics for lead and phenol removal by the studied biomaterials with high correlation coefficient (R² ≥ 0.91 for Pb²⁺ and ≥ 0.93 for phenol) and lower residual root mean square error (RMSE) and chi-square (X²). Overall, bacterial consortium-biochar composites exhibited greater remediation of lead and phenol than the sum of each single bacterial consortium and biochar systems; reflecting synergistic interaction of adsorptive capability of biochar and metabolic performance of bacterial consortium, as denoted by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The current study addressed the successful design of employing functional remediating consortium immobilized on waste biomass-derived biochar as a conducive alternative eco-sorbent and economic platform to detoxify organic and inorganic pollutants.

Adding organic amendments to agricultural systems as sustainable practices is one of the most important stages toward creating a more sustainable and environmentally friendly food system. By increasing soil fertility and nutritional content, organic fertilizers increase plant productivity. Cation Exchange Capacity (CEC) is a vital indicator of soil fertility and plant nutrient availability, which is considered one of the most significant chemical parameters that affect agricultural soil quality. The main goals of the present study were to generate protein lysate from discarded feathers (enriched in different amino acids) through solid-state fermentation using Box-Behnken design (BBD). Then, assess the efficacy of hydrolyzed feather product (as an organic amendment), time, and N-P fertilizers on soil-CEC planted with maize in calcareous soil utilizing an optimization strategy that employed the central composite design and the response surface methodology (RSM). The results revealed that the protein concentration in the customized conditions was 1173.53 µg ml⁻¹. With a predicted CEC of 31.416 cmol_c kg⁻¹, the ideal circumstances for the three variables under investigation of feather hydrolysate, time, and chemical fertilizer were 20.147 ml kg⁻¹ soil, 27 days, and 42.3% of the recommended dose, respectively. Using keratin hydrolysate (20 ml kg⁻¹ soil) as a soil amendment significantly improved the growth parameters of maize. The leaf surface area (SA, m² gm⁻¹) was increased by 695% and 37% compared to the control (without any addition) and N-P fertilizer treatments (100% of the recommended dose), respectively. Keratin hydrolysate as a sustainable production of value-added organic fertilizer applied to calcareous soil shows a synergistic effect on soil-CEC and plant growth parameters.

The quality and properties of biochar are generally influenced by the nature of the raw materials and pyrolysis techniques. To assess the quality of sesame biochar production, a disc chamber reactor set on a solar parabolic dish concentrator was proposed as a modified slow pyrolysis technique. To evaluate the physicochemical characterizations of the produced biochar, two pyrolysis settings were used: 470 °C for 1 h (T1) and 440 °C for 2 h (T2) to produce biochar from sesame stalk feedstock (SS) using the proposed solar disk chamber reactor. Ash content, mass fraction of elements (C, H, and O%), pH, surface area, zeta potential, Fourier transform infrared (FTIR), and scanning electron microscope (SEM) were investigated. The results showed that the mass of T1 biochar decreased by 5% when compared to T2, while ash content, pH, fixed carbon, and volatile gases for both biochars were relatively close. The H/C and O/C molar ratios were below 1.00 and 0.4, respectively, indicating a loss of degradable polar contents and the formation of aromatic compounds. The surface area of T2 biochar was three times the surface area of T1, with the opposite trend in mean pore diameter. Two biochars showed the same FTIR peaks and SEM data, with small differences in their characteristics, demonstrating that pyrolysis time and temperature had a tight relationship. Both biochars showed approximately similar properties. The reactor’s efficiency is mainly affected by solar energy and atmospheric conditions during operation, which influence the average surface temperature. In Egypt, climatic conditions would be more favorable in the summer to improve the efficiency of parabolic solar dish concentrators for producing high-quality biochar. Graphical abstract

The main factors influencing biochar properties are feedstock biomass and pyrolysis operational conditions. A solar parabolic dish collector was proposed as a new green approach to the pyrolysis process. The technique of this reactor was designed to produce biochar from sesame feedstock (SF) by concentrating solar radiation. This research aims to compare the main physical and chemical properties of biochar produced by the solar reactor to those of the conventional reactor (muffle furnace, SB-3). Biochar produced by the parabolic dish collector was a heterogeneous brown color. Depending on color intensity, biochar was divided into the biochar formed around the inner sidewalls of the internal chamber (SB-1) and the biochar formed in the upper part of the internal chamber (SB-2). Generally, the physiochemical properties of the SB-2 biochar were similar to the SB-3 biochar, while SB-1 biochar was similar to SF. This was because the temperature distribution was not uniform in the solar reactor. The proposed solar parabolic dish collector needs some modifications to upgrade the biochar production to be close to that produced by the electric instrument. SB-2 is preferred as a soil amendment depending on its pH, cation exchange capacity (CEC), elemental composition, ion molar ratio (H/C, O/C, and (O+N)/C), and acidic functional groups.