Alkali lignin and sodium lignosulfonate additives promote the formation of humic substances during paper mill sludge composting

The influence of biochar from animal and plant on the transformation of phosphorus during paper mill sludge composting

Biochar has effect on phosphorus adsorption, release, and transformation. This study compared the influence of biochar derived from animal (AB) and plant (PB) during paper mill sludge composting. Results indicated AB not only accelerated sludge decomposition but also had significantly higher levels of available phosphorus (AP) than PB and CK (no biochar), with AP contents in the order of AB > PB > CK. Compared to CK, AB was found to increase the relative abundance of thermophilic bacteria, and PB diversified the microbial community. Based on Pearson and RDA results, TOC/TN ratio (C/N) and organic matter (OM) explained above 50% of the variance in microbial community and phosphorus fractions. Thermophilic bacteria with high levels of OM and C/N promoted the conversion among labile and moderately labile organic phosphorus, moderately labile inorganic phosphorus, and AP. Biochar could enhance the AP conversion pathway, leading to increased levels of AP.

Release and Redistribution of Arsenic Associated with Ferrihydrite Driven by Aerobic Humification of Exogenous Soil Organic Matter

Humification of exogenous soil organic matter (ESOM) remodels the organic compositions and microbial communities of soil, thus exerting potential impacts on the biogeochemical transformation of iron (hydr)oxides and associated trace metals. Here, we conducted a 70-day incubation experiment to investigate how aerobic straw humification influenced the repartitioning of arsenic (As) associated with ferrihydrite in paddy soil. Results showed that the humification was characterized by rapid OM degradation (1-14 days) and subsequent slow maturation (14-70 days). During the degradation stage, considerable As (13.1 mg·L-1) was released into the aqueous phase, which was reimmobilized to the solid phase in the maturation stage. Meanwhile, the low-crystalline structural As/Fe was converted to a more stable species, with a subtle crystalline phase transformation. The generated highly unsaturated and phenolic compounds and enriched Enterobacter and Sphingomonas induced ferrihydrite (∼3.1%) and As(V) reduction, leading to As release during the degradation stage. In the maturation stage, carboxylic-rich alicyclic molecules facilitated the aqueous As reimmobilization. Throughout the humification process, organo-mineral complexes formed between OM and ferrihydrite via C-O-Fe bond contributed to the solid-phase As/Fe stabilization. Collectively, this work highlighted the ESOM humification-driven iron (hydr)oxide transformation and associated As redistribution, advancing our understanding of the coupled biogeochemical behaviors of C, Fe, and As in soil.

Nanoscale Biochar for Fertilizer Quality Optimization in Waste Composting: Microbial Community Regulation

Conventional composting faces challenges of nitrogen loss, product instability, and limited humic substance formation. This study investigated the effects of nanoscale biochars (nano-BCs) derived from rice straw (nano-RSB) and corn stover (nano-CSB) on manure composting. A randomized design with five treatments was used: control, regular biochars (RSB and CSB), and nano-BCs. Nano-BCs, especially nano-CSB, significantly improved compost maturity and reduced phytotoxicity, achieving a 146.20 % germination index. They increased total nitrogen (55.09-63.64 %) and phosphorus (10.25-12.33 %) retention, reduced NH4+-N loss, and promoted nitrification. Nano-CSB showed the highest final NO3--N content (8.63 g/kg). Bacterial richness and diversity increased by 25-30 % in nano-BC treatments, with selective enrichment of beneficial species. The unique properties of nano-BCs, including high surface area and microporous structure, improved nutrient retention and compost quality. Nano-BCs offers a promising solution for sustainable waste management and high-quality compost production in agriculture, significantly enhancing nutrient retention and microbial community regulation during composting process.

Improved humification and Cr(VI) immobilization by CaO2 and Fe3O4 during composting

The current research studied how Fe3O4 nanomaterials (NMs) and CaO2 affect humification and Cr(VI) immobilization and reduction during the composting of oil-tea Camellia meal and Cr-contaminated soil. The results showed that Fe3O4 NMs and CaO2 successfully construct a Fenton-like reaction in this system. The excitation-emission matrix-parallel factor (EEM-PARAFAC) demonstrated that this Fenton-like treatment increased the generation of humic acids and accelerated the humification. Meantime, RES-Cr increased by 5.91 % and Cr(VI) decreased by 16.36 % in the treatment group with CaO2 and Fe3O4 NMs after 60 days. Moreover, the microbial results showed that Fe3O4 NMs and CaO2 could promote the enrichment of Cr(VI) reducing bacteria, e.g., Bacillus, Pseudomonas, and Psychrobacter, and promote Cr(VI) reduction. This study gives a novel view and theoretical reference to remediate Cr(VI) pollution through composting.

Unveiling the effect of PFOA presence on the composting process: Roles of oxidation stress, carbon metabolism, and humification process

Perfluorooctanoic acid (PFOA), an emerging pollutant, has been frequently detected in organic solid waste. It becomes a major concern for compost application, but studies on its toxic effects during composting are rare. This study evaluated the impact of PFOA presence at the environmentally relevant level on the humification process and microbiology during composting. The results showed that the PFOA presence (15.5 μg/kg dry) caused 45.5 % and 40.5 % decreases in the total organic carbon and humic acid-like substances, respectively. PFOA negatively affected microbial activity during the thermophilic period, as evidenced by the increases in reactive oxygen species and lactate dehydrogenase concentration. It altered the microbial community with an enrichment of Bacteroidota, conducive to resisting press. Unexpectedly, the PFOA presence induced hormesis at the maturity period, consistent with stimulated carbon metabolism (i.e., glycolysis and oxidative phosphorylation). The modulated microbial metabolism stimulated the catabolic metabolism of small-molecule humus precursors and reduced intracellular quinone availability. Furthermore, the secretion of auxiliary activities for crude fiber degradation was suppressed, which decreased the generation of extracellular quinone, and thereby impeded the humification process. These findings deciphered the metabolic response of composting to PFOA presence and highlighted the potential carbon loss of PFOA-containing composting.

Biochar derived from animal and plant facilitates synergistic transformation of heavy metals and phosphorus in sewage sludge composting

This study investigated the influence of plant-derived biochar (PB) and animal-derived biochar (AB) on behavior of heavy metals and phosphorus fractions during sewage sludge composting. PB was highly effective in reducing the bioavailability of Zn and Cu by 39% and 50%, respectively, while AB decreased the bioavailability of Pb (30%) and Cd (12%). Both biochar increased available phosphorus by over 38%. Acid extractable and bioavailable Pb in AB, and water-soluble, oxidizable and total Zn, acid extractable and oxidizable Cu in PB were positively correlated with moderately resistant organic phosphorus (MROP). Besides, in AB, Cd had strong and positive correlation with highly resistant organic phosphorus (HROP). This suggested biochar facilitated the formation of stable organometallic complexes through binding metal ions to phosphorus fractions, with notable differences based on biochar source. FT-IR showed biochar promoted humification, with PB enhancing carboxyl and polysaccharide formation, while AB encouraged quinone and aryl ether structures. These surface functional groups on the biochar likely contributed to heavy metals and phosphorus binding through chelation, adsorption, and electron shuttling.

Novel Lignin-Functionalized Waterborne Epoxy Composite Coatings with Excellent Anti-Aging, UV Resistance, and Interfacial Anti-Corrosion Performance

Developing high-performance lignin anti-corrosive waterborne epoxy (WEP) coatings is conducive to the advancement of environmentally friendly coatings and the value-added utilization of lignin. In this work, a functionalized biomass waterborne epoxy composite coating is prepared using quaternized sodium lignosulfonate (QLS) as a functional nanofiller for mild carbon steel protection. The results showed that QLS has excellent dispersion and interface compatibility within WEP, and its abundant phenolic hydroxyl, sulfonate, quaternary ammonium groups, and nanoparticle structure endowed the coating with excellent corrosion inhibition and superior barrier properties. The corrosion inhibition efficiency of 100 mg L-1 QLS in carbon steel immersed in a 3.5 wt% NaCl solution reached 95.76%. Furthermore, the coating maintained an impedance modulus of 2.29 × 106 Ω cm2 (|Z|0.01 Hz) after being immersed for 51 days in the high-salt system. In addition, QLS imparted UV-blocking properties and thermal-oxygen aging resistance to the coating, as evidenced by a |Z|0.01 Hz of 1.04 × 107 Ω cm2 after seven days of UV aging while still maintaining a similar magnitude as before aging. The green lignin/WEP functional coatings effectively withstand the challenging outdoor environment characterized by high salt concentration and intense UV radiation, thereby demonstrating promising prospects for application in metal protection.

Quinones-enhanced humification in food waste composting: A novel strategy for hazard mitigation and nitrogen retention

The harmless and high-value conversion of organic waste are the core problems to be solved by composting technology. This study introduced an innovative method of promoting targeted humification and nitrogen retention in composting by adding p-benzoquinone (PBQ), the composting without any additives was set as control group (CK). The results indicated that the addition of exogenous quinones led to a 30.1% increase in humic acid (HA) content during the heating and thermophilic phases of composting. Spectroscopic analyses confirmed that exogenous quinones form the core skeleton structure of amino-quinones in HA through composting biochemical reactions. This accelerated the transformation of quinones into recalcitrant HA in the early stages of composting, and reduced CO2 and NH3 by 8% and 78%, respectively. Redundancy analysis (RDA) revealed that the decrease in carbon and nitrogen losses primarily correlated with quinones enhancing HA formation and greater nitrogen incorporation into HA (P < 0.05). Furthermore, the compost treated with quinones demonstrated a decrease in phytotoxicity and earthworm mortality, alongside a significant increase in the relative abundance of actinobacteria, which are associated with the humification process. This research establishes and proposes that co-composting with quinones-containing waste is an effective approach for the sustainable recycling of hazardous solid waste.

Different crystalline manganese dioxide and biochar co-conditioning aerobic composting: Reduced ammonia volatilization and improved organic fertilizer quality

Aerobic composting is a sustainable and effective waste disposal method. However, it can generate massive amounts of ammonia (NH3) via volatilization. Effectively reducing NH3 volatilization is vital for advancing aerobic composting and protecting the ecological environment. Herein, two crystal types of MnO2 (α-MnO2 and δ-MnO2) are combined with biochar (hydrochar (WHC) and pyrochar (WPC), respectively) and used as conditioners for the aerobic composting of chicken manure. Results reveal that α-MnO2 (34.6%) can more effectively reduce NH3 accumulation than δ-MnO2 (27.1%). Moreover, the combination of WHC and MnO2 better reduces NH3 volatilization (48.5-58.9%) than the combination of WPC and MnO2 (15.8-40.1%). The highest NH3 volatilization reduction effect (58.9%) is achieved using the combination of WHC and δ-MnO2. Because the added WHC and δ-MnO2 promote the humification of the compost, the humic acid to fulvic acid ratio (HA/FA ratio) dramatically increases. The combination of WHC and δ-MnO2 doubled the HA/FA ratio and resulted in a net economic benefit of 130.0 RMB/t. Therefore, WHC and δ-MnO2 co-conditioning can promote compost decomposition, improving the quality of organic fertilizers and substantially reducing NH3 volatilization.

Accelerating the humification of mushroom waste by regulating nitrogen sources composition: Deciphering mechanism from bioavailability and molecular perspective

Regulating nitrogen source composition is efficient approach to accelerate the spent mushroom substrate (SMS) composting process. However, currently, most traditional composting study only focuses on total C/N ratio of initial composting material. Rarely research concerns the effect of carbon or nitrogen components at different degradable level and their corresponding decomposed-substances on humification process. This study deciphers and compares the mechanism of mixed manure-N sources on SMS humification from bioavailability and molecular perspective. Two different biodegradable manure-N sources, cattle manure (CM) and Hainan chicken manure (CH), were added into the SMS composting with the different CM:CH ratio of 1:0, 3:1, 1:1, 1:3, and 0:1, respectively. The physicochemical properties and humic substances were determined to evaluate the compost quality. Coupling analysis of spectroscopy, fluorescence, and humic intermediate precursors were conducted to characterizing molecular formation process of humic acid (HA). The results indicated that regulating the carbon-nitrogen nutrient biodegradability of composting material by adding mixed nitrogen sources is an effective strategy to accelerate the SMS humification process. The C1H3 (CM:CH ratio of 1:3) and CH treatments obtained great physicochemical properties and the highest growth rate of HA (31.96% and 27.02%, respectively). The rapid reaction of polysaccharide, ketone, quinone, and amide in DOM (LCP1) might be the key for the fast humification in C1H3 and CH. The polyphenol, reducing sugar and amino acid originated from the labile-carbon-proportion I (LCP1) and recalcitrant-carbon-proportion (RCP), labile-carbon-proportion II (LCP2) and RCP, and labile-nitrogen-proportion I (LNP1), respectively, were the main driving intermediate precursors for the formation of HA. This study deciphers the SMS humification mechanism at molecular level and provides a strategy in accelerating-regulating the composting process. which will be beneficial for enhancing the disposing efficiency of SMS, producing high-quality organic fertilizer, and even popularizing to the similar types of organic waste in practical field.

Effect of the addition of biochar and wood vinegar on the morphology of heavy metals in composts

In the experiment, the morphology of heavy metals (Pb, Cr, Cd, and Ni, HMs) was characterized using flame atomic absorption spectroscopy. In addition, Fourier transform infrared spectroscopy (FTIR) and three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) were used to characterize the correlation between environmental factors and metal morphology in the rotting compost from several angles. The results showed that the humus treated with wood vinegar solution had a high degree of humification and rich aromatic structure. FTIR spectroscopy confirmed that the degree of humus aromatization gradually increased during the composting process, which enhanced the complexation of humus (HS) with HMs but had less effect on Ni. In addition, the optimum concentration of wood vinegar (WV) was determined to be 1.75%. The results of the study showed that in the Pb passivation treatment group, the proportion of soluble (Red) and exchangeable states (Exc) converted to oxidized (Oxi) and residual states (Res) was 8%, 14%, 6%, 1%, and 12% in the CK, T1, T2, T3, and T4 treatment groups, respectively; in the Cr passivation treatment group, the proportion of Cr-Red and Cr-Exc converted to oxidized and residual states was 31%, 33%, 25%, 29%, and 25%; in the Cd passivation treatment group, the proportions of Cd-Red and Cd-Exc converted to oxidized and residual states were 5%, 15%, 4%, 9%, and 11%, respectively; whereas the Ni treatment group did not show any significant passivation effect. The proportion of Pb-Oxi was relatively stable, Cr-Oxi was converted to Cr-Res, whereas Cd showed the conversion of Cd-Oxi to Cd-Exc. SUVA254 and SUVA280 showed significant positive correlations with Pb-Res, Cr-Res and Ni-Res, and significant positive correlations with moisture content (MC); whereas MC was significantly negatively correlated with each form of HMs. Total potassium (TK), total nitrogen (TN), and both carbon (TOC) were negatively correlated with Pb-Res and Pb-Exc. Structural equation modeling verified the relationship between environmental factors and HMs, and the composting results showed that the addition of biochar (BC) and a higher percentage of WV could increase compost decomposition and passivate HMs to improve its agronomic function.

Molecular insight into the transformation of dissolved organic matter during sewage sludge composting: An investigation of a full-scale composting plant

The aim of the study was to explore the molecular dynamics and transformation pathways of dissolved organic matter (DOM) in sewage sludge (SS) during composting, and the DOM of raw material, material experiencing thermophilic phase and material collected from humification phase were characterized using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry. The results indicated that there were approximately 85% of aliphatic/proteins and 75% of carbohydrate preferentially decomposed in the thermophilic phase. Moreover, lignins/carboxylic-rich alicyclic molecules (CRAM) were the main N-containing substances evolved in the decomposition, which leading to a reduction of N/C ratio from 0.073 to 0.041. Whereas aliphatic acids and tryptophan in lignins/CRAM with high oxidizing capacities are preferentially decomposed in the thermophilic phase. As for maturity phase, the carbon of the newly generated compounds (belonging to lignins/CRAM and tannins), possessed an oxidation state that similar to sulfonates and sulfonamides, and these DOM are beneficial for the humic substances formation. Moreover, it was found that the newly formed N2Ox and N3Ox compounds had a more significant contribution to the double bond equivalent (DBE) of the compost, corresponding to 1.0 and 1.7 DBE, respectively. The results would help explore the understanding of DOM transformation and humification during SS composting in the microscopic molecular level.

Black soldier fly pretreatment promotes humification and phosphorus activation during food waste composting

Black soldier fly (BSF) and thermophilic composting (TC) treatments are commonly adopted to manage food waste. In this study, 30 days of TC of food waste following seven days BSF pretreatment (BC) was compared to 37 days of TC of food waste (TC, the control). Fluorescence spectrum and 16S rRNA high-throughput sequencing analysis were used to compare the BC and TC treatments. Results showed that BC could decrease protein-like substances and increase humus substances more quickly, and that the humification index of compost products was 106.8% higher than that of TC, suggesting that the humification process was accelerated by BSF pretreatment resulting in a 21.6% shorter maturity time. Meanwhile, the concentrations of total and available phosphorus rose from 7.2 and 3.3 g kg-1 to 44.2 and 5.5 g kg-1, respectively, which were 90.5% and 118.8% higher in compost products from BC as compared to those in TC. Furthermore, BC had higher richness and diversity of humus synthesis and phosphate-solubilizing bacteria (PSB), with Nocardiopsis (53.8%) and Pseudomonas (47.0%) being the dominant PSB. Correlation analysis demonstrated that the introduction of BSF gut bacteria contributed to the effectiveness of related functional bacteria, resulting in a rapid humification process and phosphorus activation. Our findings advance understanding of the humification process and provide novel perspectives on food waste management.

Recycling of Waste Bamboo Biomass and Papermaking Waste Liquid to Synthesize Sodium Lignosulfonate/Chitosan Glue-Free Biocomposite

The development of the paper industry has led to the discharge of a large amount of papermaking waste liquid containing lignosulfonate. These lignin black liquids cause a lot of pollution in nature, which runs counter to the current environmental protection strategy under the global goal. Through the development and use of lignosulfonate in papermaking waste liquid to increase the utilization of harmful substances in waste liquid, we aim to promote waste liquid treatment and reduce environmental pollution. This paper proposes a new strategy to synthesize novel glue-free biocomposites with high-performance interfacial compatibility from papermaking by-product sodium lignosulfonate/chitosan (L/C) and waste bamboo. This L/C bamboo biocomposite material has good mechanical properties and durability, low formaldehyde emissions, a high recovery rate, meets the requirements of wood-based panels, and reduces environmental pollution. This method is low in cost, has the potential for large-scale production, and can effectively reduce the environmental pollution of the paper industry, promoting the recycling of biomass and helping the future manufacture of glue-free panels, which can be widely used in the preparation of bookcase, furniture, floor and so on.

Hydrothermal carbonization aqueous phase promotes nutrient retention and humic substance formation during aerobic composting of chicken manure

The aqueous phase (AP) of hydrothermal carbonization is rich in humic substances (HSs), which could influence the poultry manure composting process and the product quality. Here, raw AP and its modified product (MAP) with different nitrogen (N) contents were added into chicken manure composting at low (5%) or high (10%) rate. Results showed that all APs addition decreased the temperature and pH but AP-10% increased total N, HSs, and humic acid (HA) of compost by 12%, 18% and 27%, respectively. MAP applications increased the total phosphorus by 8-9% and MAP-10% enhanced the total potussium content by 20%. Additionally, both AP and MAP additions increased the contents of three major components of dissolved organic matter by 20-64%. In conclusion, both AP and MAP can generally improve the chicken manure compost quality, which provides a new idea for the recycling of APs derived from agro-forestry wastes during hydrothermal carbonization.

Insight into humification of mushroom residues under addition of Rich-N sources: Comparing key molecular evolution processes using EEM-PARAFAC and 2D-FTIR-COS analysis

Accelerating the humification of organic solid waste is one of the most important issues in composting. This present study aims to study and compare the humification process of different rich-N sources (chicken manure, cattle manure, and urea) addition during the composting of mushroom residues, from macro physicochemical properties to micro humic molecular structure evolution process. The physicochemical elements and humic components were determined for evaluating the compost quality and humification degree as composting proceed. The coupled analysis of excitation-emission matrix with parallel factor analysis (EEM-PARAFAC) and two-dimensional correlation with Fourier transform infrared spectrum (2D-FTIR-COS) were used to characterize the functional molecular structure evolution of dissolved organic matter during humification process. The results indicated that the rank order for humification level were the treatments of chicken manure (HM), urea (UM), cattle manure (CM), and single mushroom residue treatment (CK), with their humification index of 22.18%, 22.05%, 18.47%, and 16.52%, respectively. Humic substance, humic acid, and fulvic acid were obtained the highest in HM treatment with contents of 35.41 ± 0.86%, 23.32 ± 1.57%, and 10.97 ± 0.52%, respectively. The rich-N source addition enhanced the degradation of protein-like and polysaccharides-like substances in dissolved organic matter, thus accelerating the humification process of mushroom residues. The key structure evolution of dissolved organic matter in the HM treatment, in which the CO and CC stretching of quinone, amide, or ketone, and the C-O stretching of polysaccharides may be responsible for the faster formation of humus compared to the other nitrogen treatments. In this study, redundancy analysis indicated that the total nitrogen (TN) and nitrate nitrogen (NO₃^--N) may be the potential indicators for determining the humification level as composting proceed. The result provides significant insight into the humification mechanism of mushroom residue under different types of nitrogen sources at the molecular level, and will be reference for improving the composting technique in practical field.

Augmentation in polyhydroxybutyrate and biogas production from waste activated sludge through mild sonication induced thermo-fenton disintegration

In this study, an innovative approach was developed to enhance the hydrolysis through phase-separated pretreatment by removing exopolymeric substances via mild sonication followed by thermo-Fenton disintegration. The exopolymeric substances fragmentation was enhanced at the sonic specific energy input of 2.58 kJ/kg total solids. After exopolymeric substance removal, the disintegration of biomass by thermo-Fenton yield the solubilization of 29.8 % at Fe²⁺:H₂O₂ dosage and temperature of 0.009:0.036 g/g suspended solids and 80 °C as compared to thermo-Fenton alone disintegration. The polyhydroxybutyrate content of 93.1 % was accumulated by Bacillus aryabhattai at the optimum time of 42 h, while providing 70 % (v/v) pre-treated supernatant as a carbon source under nutrient-limiting condition. Moreover, the biogas generation of 0.187 L/g chemical oxygen demand was achieved using settled pretreated sludge. The pretreated sludge sample thus served as a carbon source for polyhydroxybutyrate producers as well as substrate for biogas production.

New insight and enhancement mechanisms for Feammox process by electron shuttles in wastewater treatment - A systematic review

Ammonium oxidation coupled to Fe(III) reduction (Feammox) is a newly discovered iron-nitrogen cycle process of microbial catalyzed NH₄⁺ oxidation coupled with iron reduction. Fe(III) often exists in the form of insoluble iron minerals resulting in reduced microbial availability and low efficiency of Feammox. Electron shuttles(ESs) can be reversibly oxidized and reduced which has the potential to improve Feammox efficiency. This review summarizes the discovery process, electron transfer mechanism, influencing factors and driven microorganisms of Feammox, ang expounds the possibility and potential mechanism of ESs to enhance Feammox efficiency. Based on an in-depth analysis of the current research situation of Feammox for nitrogen removal, the knowledge gaps and future research directions including how to apply ESs enhanced Feammox to promote nitrogen removal in practical wastewater treatment have been highlighted. This review can provide new ideas for the engineering application research of Feammox and strong theoretical support for its development.

Continuing progress in the field of two-dimensional correlation spectroscopy (2D-COS), part II. Recent noteworthy developments

This comprehensive survey review compiles noteworthy developments and new concepts of two-dimensional correlation spectroscopy (2D-COS) for the last two years. It covers review articles, books, proceedings, and numerous research papers published on 2D-COS, as well as patent and publication trends. 2D-COS continues to evolve and grow with new significant developments and versatile applications in diverse scientific fields. The healthy, vigorous, and diverse progress of 2D-COS studies in many fields strongly confirms that it is well accepted as a powerful analytical technique to provide an in-depth understanding of systems of interest.

Continuing progress in the field of two-dimensional correlation spectroscopy (2D-COS): Part III. Versatile applications

In this review, the comprehensive summary of two-dimensional correlation spectroscopy (2D-COS) for the last two years is covered. The remarkable applications of 2D-COS in diverse fields using many types of probes and perturbations for the last two years are highlighted. IR spectroscopy is still the most popular probe in 2D-COS during the last two years. Applications in fluorescence and Raman spectroscopy are also very popularly used. In the external perturbations applied in 2D-COS, variations in concentration, pH, and relative compositions are dramatically increased during the last two years. Temperature is still the most used effect, but it is slightly decreased compared to two years ago. 2D-COS has been applied to diverse systems, such as environments, natural products, polymers, food, proteins and peptides, solutions, mixtures, nano materials, pharmaceuticals, and others. Especially, biological and environmental applications have significantly emerged. This survey review paper shows that 2D-COS is an actively evolving and expanding field.

In situ generated oxygen distribution causes maturity differentiation during electrolytic oxygen aerobic composting

Electrolytic oxygen aerobic composting (EOAC) is an effective treatment with greater technical superiority and cost advantages for organic solid waste using in situ electrolytic oxygen as a feasible strategy to replace conventional aeration. However, the unclear effects of distribution and variation of in situ electrolytic oxygen on compost maturation in different depth zones of EOAC need further exploration. This study demonstrated that the humification of organic matter was faster at the bottom than in the middle and at the top. The main reason was that the higher oxygen content and lower moisture content in the bottom promoted microbial degradation and heat production, resulting in higher temperatures. The microbial analysis showed that the abundance of typical thermophilic bacteria (such as Cerasibacillus, Lactobacillus, and Pseudogracilibacillus) that could promote compost maturation was higher at the bottom than in the middle and at the top. The finding provided in-depth molecular insights into differentiated humification from bottom to top in EOAC and revealed its further practical engineering applications.

Deciphering the structural characteristics and molecular transformation of dissolved organic matter during the electrolytic oxygen aerobic composting process

Electrolytic oxygen aerobic composting (EOAC) effectively treats organic solid waste by using in-situ electrolytic oxygen for aeration. However, the fundamental mechanism of compost maturity is still unclear. Therefore, we comprehensively characterized dissolved organic matter (DOM) transformation closely related to compost maturity during EOAC. Excitation-emission matrix-parallel factor (EEM-PARAFAC) and Fourier transform infrared (FTIR) analysis confirmed that EOAC quickly decreased organic matter and increased humus substances, accelerating the compost humification process compared with conventional aerobic composting. Electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis reveals that the double bound equivalent and aromaticity index during EOAC are higher than in conventional aerobic composting (CAC), suggesting more aromatic compounds in EOAC. DOM's detailed transformation investigation suggested that low O/C and high H/C compounds were preferentially decomposed during EOAC. Our investigation firstly extends the in-depth molecular mechanisms of humification during EOAC, and reveals its practical engineering applications.

Differentiated strategies of animal-derived and plant-derived biochar to reduce nitrogen loss during paper mill sludge composting

This work aimed to reveal the differences of nitrogen (N) transformation between animal-derived and plant-derived biochar during paper mill sludge composting. Three treatments were established, including CK (no biochar), ABC (animal-derived biochar), and PBC (plant-derived biochar). Results showed that N loss was reduced by 24.43% and 35.50% in ABC and PBC, respectively, compared with CK. Moreover, the contents of acid-insoluble N (AIN) in ABC and bioavailable organic N (BON) in PBC were 6.180 g/kg and 9.269 g/kg higher than in CK (2.602 g/kg and 8.988 g/kg). The protease activity and bacterial abundance associated with the generation of humic N-containing precursors increased in ABC. Low urease activity and a more complex bacterial N-cycling network were found in PBC. Structural equation model confirmed that AIN formation and BON retention were the dominant strategies for animal-derived and plant-derived biochar, respectively. The findings provided multiple pathways to produce N-enriched compost products.

The role of (bio)degradability on the management of petrochemical and bio-based plastic waste

In order to mitigate the social and ecological impacts of post-consumer plastic made of conventional petrochemical polymers, the market of (bio)degradable plastics have recently become more widespread. Although (bio)degradable plastics could be an environmentally friendly substitute of petrochemical ones, the consequences of their presence in the waste management system and in the environment (if not correctly disposed) are not always positive and plastic pollution is not automatically solved. Consequently, this work aims to review how plastic (bio)degradability affects the municipal solid waste management cycle. To this end, the state-of-the-art of the intrinsic (bio)degradability of conventional and unconventional petrochemical and bio-based polymers has been discussed, focusing on the environment related to the waste management system. Then, the focus was on strategies to improve polymer (bio)degradability: different types of eco-design and pre-treatment approach for plastics has been investigated, differently from other works that focused only on specific topics. The information gathered was used to discuss three typical disposal/treatment routes for plastic waste. Despite many of the proposed materials in eco-design have increased the plastics (bio)degradability and pre-treatments have showed interesting results, these achievements are not always positive in the current MSW management system. The effect on mechanical recycling is negative in several cases but the enhanced (bio)degradability can help the treatment with organic waste. On the other hand, the current waste treatment facility is not capable to manage this waste, leading to the incineration the most promising options. In this way, the consumption of raw materials will persist even by using (bio)degradable plastics, which strength the doubt if the solution of plastic pollution leads really on these materials. The review also highlighted the need for further research on this topic that is currently limited by the still scarce amount of (bio)degradable plastics in input to full-scale waste treatment plants.

Moisture migration driven by the electric field causes the directional differentiation of compost maturity

Electric field-assisted aerobic composting (EAC) has been recently believed as a novel and effective process for the resource utilization of organic solid waste. However, the effect of electric field in composting process needs to be further clarified. Herein, moisture migration and compost maturity along electric-field-direction (from anode to cathode) in EAC was first to be explored. It was found that moisture content and compost maturity changed regularly from anode to cathode. At the end of composting, the moisture content of S3 (cathodic zone) was 30% and 62% higher than that of S2 (middle zone) and S1 (anodic zone), respectively. The germination index (a key parameter for compost maturity) in S3 (138.92%) was significantly higher than that of S2 (104.98%) and S1 (84.45%). However, temperatures in S3 were lower than that of S1 and S2, indicating the moisture content played a more important role than temperature for compost maturity in EAC. Furthermore, the microbial activities in S3 were also higher than that of S1 and S2, supporting the trend of compost maturity. This pioneering study demonstrates the electric field can drive moisture gradient migration to control the directional differentiation of compost maturity, showing a great application potential in aerobic composting.

Lignin reinforced hydrogels with fast self-recovery, multi-functionalities via calcium ion bridging for flexible smart sensing applications

Hydrogels have found applications in many different fields. However, poor mechanical properties, such as low elasticity and lack of rapid recovery under large deformation, can severely limit their applications. In this study, we developed lignin reinforced hydrogels made of calcium ion containing ternary polymers (lignosulfonate (LS), alginate (Alg), and polyacrylic acid (PAA)). The resultant hydrogel has excellent elasticity, rapid self-recovery, and multi-functionalities. The covalent PAA network acts as the elastic scaffold of hydrogel, while calcium bridging networks of LS, Alg, and PAA, as well as the strong hydrogen bonding network in the system, function as sacrifice bonds to dissipate energy and transfer stress. The PAA/LS/Alg/Ca hydrogels exhibit rapid and durable elastic recovery ability under large deformation with the highest compressive stress of 835 kPa (95% strain), highest tensile fracture stress of 357 kPa, and highest tensile strain of 1144%. In addition, these tough hydrogels show UV resistance, self-healing, antifreeze, and excellent electro-conductivity. When assembled into a strain sensor, stable and reliable electrical responses with 375 ms response time are demonstrated. The PAA/LS/Alg/Ca hydrogel strain sensors can monitor human movements with responsive and accurate physiological signals. These results support the conclusion that the PAA/LS/Alg/Ca hydrogel strain sensors have great application potential in flexible wearable electronics and smart devices.

When dewatered swine manure-derived biochar meets swine wastewater in anaerobic digestion: A win-win scenario towards highly efficient energy recovery and antibiotic resistance genes attenuation for swine manure management

This work explored the feasibility of dewatered swine manure-derived biochar (DSMB) as an additive to facilitate anaerobic digestion (AD) of swine wastewater for energy recovery and antibiotic resistance genes (ARG) attenuation enhancements. With 20 g/L DSMB assistance, the methanogenic lag time of swine wastewater was shortened by 17.4-21.1%, and the maximum CH₄ production rate increased from 40.8 mL/d to 48.3-50.5 mL/d, among which DSMB prepared under 300 °C exhibited a better performance than that prepared under 500 °C and 700 °C. Integrated analysis of DSMB electrochemical properties, microbial electron transfer system activity, and microbial community succession revealed the potential of DSMB-300 to act as redox-active electron transfer mediators between syntrophic microbes to accelerate syntrophic methanogenesis via potential direct interspecies electron transfer. Meanwhile, DSMB preparation by pyrolysis dramatically reduced ARG abundance by almost 4 logs. Adding DSMB into AD not only strengthened the attenuation efficiency of ARG in the original swine wastewater, but also effectively controlled the potential risk of horizontal gene transfer by mitigating 74.8% of the mobile gene elements abundance. Accordingly, we proposed a win-win scenario for bio-waste management in swine farms, highlighting the more advanced energy recovery and ARG attenuation compared to the current status.

Bacterial dynamics for gaseous emission and humification in bio-augmented composting of kitchen waste

Using high-throughput sequencing and Functional Annotation of Prokaryotic Taxa (FAPROTAX), this study aimed to elucidate the effect of bacterial dynamics on gaseous emission and humification of kitchen and garden wastes during composting augmented with microbial inoculants. Microbial inoculant addition at up to 0.9% resulted in a diverse bacterial community with more functional bacteria to amend gaseous emission and enhance humification. Microbial inoculation facilitated the enrichment of aerobic bacteria (e.g. the genus Bacillus and Thermobifida) to enhance cellulolysis and ligninolysis to advance organic humification. By contrast, several bacteria, such as the genus Weissella and Pusillimonas were inhibited by microbial inoculation to weaken fermentation and nitrate respiration. As such, bio-augmented composting with 0.9% microbial inoculant reduced the emission of methane by 11-20% and nitrogen oxide by 17-54%. On the other hand, ammonia and hydrogen sulphide emissions increased by 26-62% and 5-23%, respectively, in bio-augmented composting due to the considerable proliferation of the genus Bacillus and Desulfitibacter to enhance ammonification and sulphur-related respiration. Results from this study highlight the need to further develop efficient and multifunctional microbial inoculants that promote humification and deodorization for bio-augmented composting of kitchen waste as well as other carbon and nutrient rich organic wastes.

Influences of humic-rich natural materials on efficiencies of UASB reactor: A comparative study

Two humic-rich natural materials namely peat soil and lignite were supplemented in up-flow anaerobic sludge blanket (UASB) bioreactors for the treatment of phenolic wastewater. Peat soil improved phenol degradation and resistance to shock load; ultimately, contributing to higher COD removal efficiency (83.3%), methane production (4532 mL d^-1), and better reactor's stability. Accordingly, the amount of extracellular polymeric substances (EPS) and coenzyme F₄₂₀ in sludge were increased to 1.3-fold and 2.5-fold, respectively, as compared to the control treatment. The addition of lignite however displayed poor phenol degradation and no effects on the secretion of EPS and F₄₂₀. The peat soil significantly influenced the microbial community structures, whereas the effect of lignite was inconspicuous. In the presence of peat soil, the abundance of syntrophic fermentation bacteria and methanogens was significantly increased. This study illustrates the potential use of peat soil in UASB for the treatment of phenolic wastewaters.

Effects of swine manure composting by microbial inoculation: Heavy metal fractions, humic substances, and bacterial community metabolism

This study aimed to investigate the effect of swine manure composting with microbial inoculation (MI) and without MI (CK) on heavy metal (Cr, Cd, and Pb) fractions, humic substance (HS), and metabolism pathway. The results showed that MI could passivate the heavy metal Cr and reduce the proportion of exchangeable (EXC) fraction of Cd, but it does not affect the EXC fraction of Pb. Compared to CK, HS, humic acid (HA), and fulvic acid (FA) were significantly increased with MI at the maturity stage. The propagation of Proteobacteria (day 4) and Firmicutes (days 12 and 24) was strengthened with MI. Canonical correlation analysis found that HA and Firmicutes were positively correlated with heavy metal (Cr, Cd, and Pb) residual (RES) fraction, and FA was positively correlated with Proteobacteria. Moreover, MI can significantly increase amino acid metabolism and carbohydrate metabolism by day 4, enhance the metabolism of enzyme families and glycan biosynthesis by day 12, and improve membrane transport. Overall, MI could facilitates the increase in HA and FA content and transfer of heavy metal (Cr, Cd, and Pb) fractions, it particularly helps increase the RES fraction.

Formation of Humic-Like Substances during the Technological Process of Lignohumate® Synthesis as a Function of Time

The composition, structure, and biological activity of humic-like substances (HLS) synthesized in the process of lignosulfonate conversion for the production of the humic product Lignohumate® (LH) were examined. It is shown that during the hydrolytic-oxidative process, the transformation of raw material and accumulation of HLS occur. Data on the chemical (elemental content, functional groups, FTIR) and spectral (absorbance and fluorescence) parameters and biological activity (in phytotest) combined with PCA show that the LH samples can be divided into three groups, depending on the duration of synthesis: initial raw material (0-time sample); “young” HLS (15–30 min), and “mature” HLS in 45–120 min of treatment. During the first 30 min, reactions similar to the ones that occur during lignin humification in nature take place: depolymerization, oxidative carboxylation, and further polycondensation with the formation and accumulation of HLS. After 45–60 min, the share of HLS reaches a maximum, and its composition stabilizes. Biological activity reaches a maximum after 45–60 min of treatment, and at that stage, the further synthesis process can be stopped. Further processing (up to 2 h and more) does not provide any added value to the humic product.