Waste milk humification product can be used as a slow release nano-fertilizer

Alkaline-thermal synergistic activation of persulfate for sawdust hour-level humification to prepare fulvic-like-acid fertilizer

Sawdust is a by-product of wood processing and it was rapidly humified with K2S2O8 under alkaline-thermal synergistic activation to produce a fulvic-like-acid (FLA) organic fertilizer (SFOF) in this study. The optimum conditions were K2S2O8: KOH mass ratio of 1:2 and 150°C, meanwhile FLA yield could reach 180.3 mg/g in 2 h. The carboxylation, Maillard reaction, and aromatization processes occurred during sawdust humification. And then, SFOF was mixed with attapulgite and modified starch binder to get an organic fertilizer (SAM), and coated with amino silicone oil (ASO) to create a slow-release granule (SAM@ASO). The release mechanism of FLA from SAM@ASO was consistent with Ritger-Peppas release kinetics. SAM@ASO, with high biosafety, could promote water spinach growth and remediate acidic soil (pH from 4.9 to 6.3). This method offers a promising approach for sawdust utilization and a novel FLA-based organic fertilizer for acidic soil remediation.

Multi-omics analysis to a sludge composting system reveals thermophilic bacteria promote free amino acid production and compost quality

Recycling waste nutrients from waste activated sludge (WAS) back to agricultural land through composting embodies the core principle of circular economy. However, large quantities of nitrogen are lost as nitrogenous gases during composting, reducing the fertilization performance of the final products. Here, the N cycle and amino acid (AA) biotransformation profiles in an industrial-scale sludge composting plant (130t/d) were investigated using replicated and temporally sampled multi-omics datasets. The results revealed that 44.4 % of nitrogen was lost to nitrogenous gas after composting, and the enhanced N cycle - specifically, (i) glutamate → NH3 +α-ketoglutarate, (ii) glutamate + NH3→ glutamine, and (iii) glutamine + aspartate → asparagine + glutamate, mainly mediated by thermophilic Pseudoxanthomonas. sp, are responsible for nitrogen loss. During thermophilic stage, 71.4 % of enzymes involved in AA transformation were upregulated, leading to a peak free AA content of 10.60 mg/g-TS, with glutamate comprising 51.8 % of the total. When composting reached cooling stage, free AA content dropped quickly to 5.74 mg/g-TS. Based on nitrogen monitoring and AA-centered transformation, a novel short-term composting strategy was proposed for AA-rich compost production. Then, plant experiments demonstrated that AA-rich compost outperformed conventional compost in promoting plant growth under both pot and hydroponic conditions, likely by improving root amino acid transport. Sustainability analysis revealed that the total cost and greenhouse gas emissions of AA-rich compost production were 31.9 % and 74.9 % lower than those of conventional compost, respectively. These findings provide a potential solution to make WAS more sustainable by regulating free AA production.

Built-in electric field of Ag2Se thermoelectric effect activated persulfate for humic acid decomposition in water: Molecular transformation mechanism

Water temperature fluctuations directly impact pollutant decomposition processes in wastewater. Thermoelectric effect is considered an alternative to utilize these temperature variations for pollution control. In this study, a system for persulfate (PS) activation by Ag2Se thermoelectric catalyst under water temperature gradients (Ag₂Se/ΔT/PS) was developed for humic acid (HA) degradation in water. The experimental results showed that the Ag2Se/ΔT/PS system achieved a 90.7 % HA removal efficiency, outperforming both PS/ΔT (PS with temperature gradients) and Ag2Se/ΔT systems. Thermoelectric simulations indicated that Ag2Se generated an electric field under temperature variations, with higher current density at surface pores where polarized charges efficiently activated PS. Density functional theory calculations revealed that the thermoelectric effect of Ag2Se lowered the energy barriers for PS activation and ·SO4- generation. Different from ·OH-led decomposition of HA in the Ag₂Se/ΔT system, ·SO4- and ·OH dominated HA decomposition in the Ag₂Se/ΔT/PS system, and ¹O₂ also contributed this process. Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed that oxidation, decarboxylation, and sulfidation were the primary pathways driving HA degradation, leading to decreases in CHO-containing compounds and formation of S-rich byproducts. These findings highlighted the potential of thermoelectric catalysts in advancing water treatment technologies.

Nanofertilizers for Sustainable African Agriculture: A Global Review of Agronomic Efficiency and Environmental Sustainability

As Africa's population continues to grow, the need for sustainable agricultural practices has intensified, sparking greater interest in nanofertilizers This review critically evaluates the agronomic efficiency and environmental sustainability of nanofertilizers in the African context. It combines existing research on nanofertilizers' effectiveness, nutrient-use efficiency, and environmental impact. Nanofertilizers have shown a nutrient-use efficiency boost of up to 30% compared to conventional fertilizers. This review also highlights benefits such as enhanced crop yields (up to 25% increase in maize production), reduced chemical fertilizer requirements (up to 40% reduction in nitrogen application), and improved soil health. The analysis informs policy, research, and practice aimed at optimizing nanofertilizer deployment for sustainable African agriculture. The projected global population of 2.4 billion by 2050 highlights that the need for sustainable agricultural solutions has never been more important. Our review conveys an assessment of nanofertilizers' potential contribution to Africa's agricultural sustainability and food security.

Efficient resource recovery from food waste digestate via hydrothermal treatment and its application as organic fertilizer

With the continuous recognition of green, organic and non-polluting products, organic fertilizers play an increasingly vital role in agricultural production. Among them, hydrochar-based organic fertilizer has attracted widespread attention recently. The present study evaluated the potential of digestate from anaerobic digestion of food waste for the preparation of hydrochar-based organic fertilizer by straw-based, FeCl3-catalyzed hydrothermal carbonization (HTC). Under the optimal conditions, a hydrochar-based organic fertilizer with > 25 wt% humus content and limited pollution risk was successfully prepared. The pot experiment demonstrated the feasibility of improving the physicochemical properties of red soil and promoting crop growth after adding hydrochar in place of commercial fertilizer. In addition, the function of zeolite on nutrient recovery in hydrothermal liquid (HTL) was analyzed, and preparing the slow-release organic fertilizer by mixing the nutrient-rich zeolite with hydrochar in a mass ratio of 1:4 was proposed. This work has significant implications for achieving the efficient resource recovery of digestate.

Multifaceted impacts of nanoparticles on plant nutrient absorption and soil microbial communities

With the growth of the global population and the increasing scarcity of resources, the sustainability and efficiency improvement of agricultural production have become urgent needs. The rapid development of nanotechnology provides new solutions to this challenge, especially the application of nanoparticles in agriculture, which is gradually demonstrating its unique advantages and broad prospects. Nonetheless, various nanoparticles can influence plant growth in diverse manners, often through distinct mechanisms of action. Beyond their direct effects on the plant itself, they frequently alter the physicochemical properties of the soil and modulate the structure of microbial communities in the rhizosphere. This review focuses intently on the diverse methods through which nanoparticles can modulate plant growth, delving deeply into the interactions between nanoparticles and plants, as well as nanoparticles with soil and microbial communities. The aim is to offer a comprehensive reference for the utilization of functionalized nanoparticles in the agricultural sector.

Unlocking the roles of wheat root exudates in regulating laccase-catalyzed estrogen humification

While laccase humification has an efficient capacity to convert estrogenic pollutants, the roles of wheat (Triticum aestivum L.) root exudates (W-REs) in the enzymatic humification remain poorly understood. Herein, we presented the research into the effects of W-REs on 17β-estradiol (E2) and bisphenol A (BPA) conversion in vitro laccase humification. W-REs inhibited E2 removal but promoted BPA conversion in the enzymatic humification, and the first-order kinetic constants for E2 and BPA were 0.27-0.69 and 0.28-0.55 h-1, respectively. Specialized small phenols and amino acids in W-REs were susceptible to laccase humification, resulting in increased copolymerization of estrogen and W-REs. In greenhouse hydroponics, the accumulated amounts of E2 (BPA) in the roots and shoots were estimated to be 0.87 (2.15) and 0.43 (0.51) nmol·plant-1 at day 3, respectively. By forming low- and eventually non-toxic copolymeric precipitates between estrogen and W-REs, laccase humification lowered the phytotoxicity and bioavailability of estrogen in the rhizosphere solution, consequently relieving its uptake, accumulation, and distribution in the wheat cells. This work sheds light on the roles of W-REs in regulating laccase-catalyzed estrogen humification, and gives an insight into the path of addressing organic contamination in the rhizosphere and ensuring food safety.

Response of humification process to fungal inoculant in corn straw composting with two different kinds of nitrogen sources

Inoculation is widely used in composting to improve the mineralization process, however, the link of fungal inoculant to humification is rarely proposed. The objective of this study was to investigate the effect of compound fungal inoculation on humification process and fungal community dynamics in corn straw composting with two different kinds of nitrogen sources [pig manure (PM) and urea (UR)]. Structural equation modeling and random forest analysis were conducted to identify key fungi and explore the fungi-mediated humification mechanism. Results showed that fungal inoculation increased the content of humic acids in PM and UR by 71.76 % and 53.01 % compared to control, respectively. High-throughput sequencing indicated that there were more key fungal genera for lignin degradation in PM especially in the later stage of composting, but a more complex fungal (genera) connections with lower humification degree was found in UR. Network analysis and random forest suggested that inoculation promoted dominant genus such as Coprinus, affecting lignocellulose degradation. Structural equation modeling indicated that fungal inoculation could promote humification by direct pathway based on lignin degradation and indirect pathway based on stimulating the indigenous microbes such as Scedosporiu and Coprinus for the accumulation of carboxyl and polyphenol hydroxyl groups. In summary, fungal inoculation is suitable to be used combining with complex nitrogen source such as pig manure in straw composting.

Facet-engineering strategy of phosphogypsum for production of mineral slow-release fertilizers with efficient nutrient fixation and delivery

Phosphogypsum (PG) presents considerable potential for agricultural applications as a secondary primary resource. However, it currently lacks environmentally friendly, economically viable, efficient, and sustainable reuse protocols. This study firstly developed a PG-based mineral slow-release fertilizer (MSRFs) by internalization and fixation of urea within the PG lattice via facet-engineering strategy. The molecular dynamics simulations demonstrated that the binding energy of urea to the (041) facet of PG surpassed that of the (021) and (020) facets, with urea's desorption energy on the (041) facet notably higher than on the (021) and (020) facets. Guided by these calculations, we selectively exposed the (041) dominant facet of PG, and then achieving complete urea fixation within the PG lattice to form urea-PG (UPG). UPG exhibited a remarkable 48-fold extension in N release longevity in solution and a 45.77% increase in N use efficiency by plants compared to conventional urea. The facet-engineering of PG enhances the internalization and fixation efficiency of urea for slow N delivery, thereby promoting nutrient uptake for plant growth. Furthermore, we elucidated the intricate interplay between urea and PG at the molecular level, revealing the involvement of hydrogen and ionic bonding. This specific bonding structure imparts exceptional thermal stability and water resistance to the urea within UPG under environmental conditions. This study has the potential to provide insights into the high-value utilization of PG and present innovative ideas for designing efficient MSRFs.

Mechanistic insights into chemical conditioning on transformation of dissolved organic matter and plant biostimulants production during sludge aerobic composting

Inorganic coagulants (aluminum and iron salt) are widely used to improve sludge dewaterability, resulting in numerous residues in dewatered sludge. Composting refers to the controlled microbial process that converts organic wastes into fertilizer, and coagulant residues in dewatered sludge can affect subsequent compost efficiency and resource recycling, which remains unclear. This work investigated the effects of two typical metal salt coagulants (poly aluminum chloride [PAC] and poly ferric sulfate [PFS]) conditioning on sludge compost. Our results revealed that PAC conditioning inhibited composting with decreased peak temperature, microbial richness, enzymatic reaction intensities, and compost quality, associated with decreased pH and microbial toxicity of aluminum. Nevertheless, PFS conditioning selectively enriched Pseudoxanthomonas sp. and resulted in more fertile compost with increased peak temperature, enzymatic reaction intensities, and humification degree. Spectroscopy and mass difference analyses indicated that PFS conditioning enhanced reaction intensities of labile biopolymers at the thermophilic stage, mainly comprising hydrolyzation (H2O), dehydrogenation (-H2, -H4), oxidation (+O1H2), and other reactions (i.e., +CH2, C2H4O1, C2H6O1). Unlike the common composting process primarily conducts humification at the cooling stage, PFS conditioning changed the main occurrence stage to the thermophilic stage. Non-targeted metabolomics revealed that indole (a humification intermediate) is responsible for the increased humification degree and indoleacetic acid content in the PFS-conditioned compost, which then promoted compost quality. Plant growth experiments further confirmed that the dissolved organic matter (DOM) in PFS-conditioned compost produced the maximum plant biomass. This study provided molecular-level evidence that PFS conditioning can promote humification and compost fertility during sludge composting, enabling chemical conditioning optimization for sustainable management of sludge.