Comparison between UV spectroscopy and Nirs to assess humification process during sewage sludge and green wastes co-composting

Multi-stage aeration regime to regulate organic conversion toward gas alleviation and humification in food waste digestate composting

Aerobic composting has been considered as a pragmatic technique to convert food waste digestate into high-quality biofertiliser. Nevertheless, massive gaseous emission and immature product remain the primary challenges in food waste digestate composting. Thus, the performance of multi-stage aeration regimes to improve gaseous emissions and organic humification during food waste digestate composting was investigated in this study. In addition to continuous aeration with a constant intensity of 0.3 L kg·dry mass (DM)-1·min-1, two multi-stage decreased aeration regimes were designed as "0.3-0.2-0.1" and "0.3-0.1-0.1" L·kg·DM-1·min-1 from the thermophilic to cooling and then mature stages, respectively. Results showed that the decreased aeration regimes could alleviate nitrous oxide (N2O) and ammonia (NH3) emission and slightly enhance humification during composting. The alleviated N2O and NH3 emission were mainly contributed by abiotically reducing gaseous release potential as well as biotically inactivating denitrifers (Pusillimonas and Pseudidiomarina) and proliferating Atopobium to reduce nitrate availability under lower aeration supply. The "0.3-0.2-0.1 L kg·DM-1·min-1" regime exhibited a more excellent performance to alleviate N2O and NH3 emission by 27.5% and 16.3%, respectively. Moreover, the decreased aeration regimes also favored the enrichment of functional bacteria (Caldicoprobacter and Syntrophomonas) to accelerate lignocellulosic biodegradation and thus humic acid synthesis by 6.5%-11.2%. Given its better performance to improve gaseous emissions and humification, the aeration regime of "0.3-0.2-0.1 L kg·DM-1·min-1" are recommended in food waste digestate composting in practice.

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.

Hydrochar and Its Dissolved Organic Matter Aged in a 30-Month Rice-Wheat Rotation System: Do Primary Aging Factors Alter at Different Stages?

Hydrochar, recognized as a green and sustainable soil amendment, has garnered significant attention. However, information on the aging process in soil and the temporal variability of hydrochar remains limited. This study delves deeper into the interaction between hydrochar and soil, focusing on primary factors influencing hydrochar aging during a 30-month rice-wheat rotation system. The results showed that the initial aging of hydrochar (0-16 months) is accompanied by the development of specific surface area and leaching of hydrochar-derived dissolved organic matter (HDOM), resulting in a smaller particle size and reduced carbon content. The initial aging also features a mineral shield, while the later aging (16 to 30 months) involves surface oxidation. These processes collectively alter the surface charge, hydrophilicity, and composition of aged hydrochar. Furthermore, this study reveals a dynamic interaction between the HDOM and DOM derived from soil, plants, and microbes at different aging stages. Initially, there is a preference for decomposing labile carbon, whereas later stages involve the formation of components with higher aromaticity and molecular weight. These insights are crucial for understanding the soil aging effects on hydrochar and HDOM as well as evaluating the interfacial behavior of hydrochar as a sustainable soil amendment.

Biological and Chemical Characterization of Musa paradisiaca Leachate

There is a growing demand for molecules of natural origin for biocontrol and biostimulation, given the current trend away from synthetic chemical products. Leachates extracted from plantain stems were obtained after biodegradation of the plant material. To characterize the leachate, quantitative determinations of nitrogen, carbon, phosphorus, and cations (K+, Ca2+, Mg2+, Na+), Q2/4, Q2/6, and Q4/6 absorbance ratios, and metabolomic analysis were carried out. The potential role of plantain leachates as fungicide, elicitor of plant defense, and/or plant biostimulant was evaluated by agar well diffusion method, phenotypic, molecular, and imaging approaches. The plant extracts induced a slight inhibition of fungal growth of an aggressive strain of Colletotrichum gloeosporioides, which causes anthracnose. Organic compounds such as cinnamic, ellagic, quinic, and fulvic acids and indole alkaloid such as ellipticine, along with some minerals such as potassium, calcium, and phosphorus, may be responsible for the inhibition of fungal growth. In addition, jasmonic, benzoic, and salicylic acids, which are known to play a role in plant defense and as biostimulants in tomato, were detected in leachate extract. Indeed, foliar application of banana leachate induced overexpression of LOXD, PPOD, and Worky70-80 genes, which are involved in phenylpropanoid metabolism, jasmonic acid biosynthesis, and salicylic acid metabolism, respectively. Leachate also activated root growth in tomato seedlings. However, the main impact of the leachate was observed on mature plants, where it caused a reduction in leaf area and fresh weight, the remodeling of stem cell wall glycopolymers, and an increase in the expression of proline dehydrogenase.

Rotifer distribution patterns in relation to dissolved organic matter in the middle reaches of Huai River Basin during the dry season

Increased dissolved organic matter (DOM) may induce water browning and affect zooplankton communities by changing photochemical environment, microbial food web, and bioavailability of organic carbon supply. However, little is known about the relationship between DOM components and rotifers in natural rivers, relative to the cladocerans and copepods. Here, we investigated the spatial patterns of rotifer distribution in relation to DOM by collecting forty-four water samples from four areas in the middle reaches of Huai River Basin. Results revealed that DOM was described by two humic-like and two protein-like components. There were significant differences in the composition and diversity of rotifer communities among areas, which might be related to autochthonous and allochthonous DOM as well as geographical distances. Specifically, rotifer communities were mainly related to molecular weight, substituents on the aromatic ring, humification level, and protein-like materials. Autochthonous and fresh DOM was positively associated with rotifer abundance and richness, and terrigenous humic-like substances were positively associated with rotifer diversity and evenness. There was a reciprocal effect between rotifer and DOM. Our findings will contribute to the understanding of the possible effects of water browning on rotifer communities, providing new insights into the key role of DOM and rotifer in the energy transfer of aquatic systems.

Intermittent aeration to reduce gaseous emission and advance humification in food waste digestate composting: Performance and mechanisms

This study investigated the performance and mechanisms of intermittent aeration to regulate gaseous emission and humification during food waste digestate composting. In addition to continuous aeration, three intermittent aeration regimes were conducted with the on-off interval ratio at 3:1, 2:1, and 1:1 within each 30 min, respectively. Results showed that intermittent aeration regimes reduced gaseous emission and enhanced humification during composting. In particular, intermittent aeration with the on/off ratio of 1:1 was more effective to reduce organic mineralization than other regimes, which alleviated the emission of nitrous oxide and ammonia by 63.1% and 75.7% in comparison with continuous aeration, respectively. In addition, this aeration regime also enhanced the content of humic acid by 24.1%. Further analysis demonstrated that prolonging aeration-off intervals could enrich facultative bacteria (e.g. Atopobium and Clostridium) from digestate and inhibit the proliferation of several aerobic bacteria (e.g. Caldicoprobacter and Marinimicrobium) to retard organic mineralization for humification.

Effect of biochar addition on copper and zinc passivation pathways mediated by humification and microbial community evolution during pig manure composting

The mobility and bioavailability of Cu and Zn are the main threats associated with the land application of pig manure (PM) compost products. This study investigated the impacts of biochar (BC) concentration on passivation of Cu and Zn associated with the compost maturity. The results indicated that 15% and 10% BC favoured the passivation of Cu and Zn, respectively. BC promoted passivation of Cu by accelerating HA production and optimized the abundance of Firmicutes. BC promoted the passivation of Zn by increasing the high temperature peak and the corresponding pH (8-8.5). A higher level (15% and 20%) of BC altered the dominant bacterial phylum from Firmicutes to Proteobacteria. 20% BC inhibited the passivation of Cu and Zn by reducing the highest temperature and lowering the alkalinity of substrate. These results offer new insights into understanding how the addition of BC could reduce the risk of hazardous products during PM composting.

Impact of compost methods on humification and heavy metal passivation during chicken manure composting

Livestock manure is one of the main sources of heavy metals (HMs) in agricultural soil. So, it is necessary to reduce its bioavailability before used as organic fertilizer. In this study, the passivation effect of HMs and the evolution of dissolved organic matter (DOM) during four composting processes were explored. Results showed that different composting methods had a great effect on HMs passivation rate and humification degree. HMs were released during the thermophilic phase, and were bound by resynthesized humus during the cooling period. The best passivation effect of HMs was found in FV + T treatment, the passivation rate of Cu, Zn, Cd and Pb reached 63.80%, 34.07%, 86.54% and 45.14%, respectively, then followed by the treatment of NV + T and SC. UV-Vis spectra and excitation-emission matrix (EEM) spectra indicated that humus precursors were produced during thermophilic phase and the accumulation of humus mainly occurred in cooling period. This study can be used as a theoretical support for the safe utilization livestock manure.

Effect of ventilation quantity on electron transfer capacity and spectral characteristics of humic substances during sludge composting

Humic substances (HSs) can ameliorate soil pollution by mediating electron transfer between microorganisms and contaminants. This capability depends on the redox-active functional structure and electron transfer capacity (ETC) of HS. This study mainly aimed to analyze the effects of different ventilation quantities on the ETC and spectral characteristics of HS (including humic acids (HAs) and fulvic acids (FAs)) during sludge composting. HS was extracted from compost with different ventilation quantities (0.1, 0.2, and 0.3 L kg^-1 dry matter min^-1, denoted as VQ1, VQ2, and VQ3, respectively). The ETC of HS was measured by electrochemical method. Excitation-emission matrix (EEM) spectroscopy, ultraviolet and visible (UV-Vis) spectrophotometry, and Fourier transform infrared (FT-IR) spectroscopy were conducted to understand the evolution of HS composition during composting. Results indicated that the ETC of HA and FA increased during composting, and VQ2 had stronger ETC and electron recycling rate than VQ1 and VQ3 at the end of composting. UV-Vis analysis revealed that the humification degree, aromatization degree, and molecular weight of HA and FA increased during composting, while the content of lignin decreased. EEM-PARAFAC results suggested that VQ2 accelerated the degradation of protein-like substances. FT-IR revealed a decrease trend in polysaccharide and aliphatic, and the carboxyl content increased in VQ2 and VQ3 while decreased in VQ1. Correlation analysis was used to study the relationship between HS components and ETC. The results advance our further understanding of the pollution remediation mechanism of HS.

Optimization of tomato waste composting with integration of organic feedstock

Valorization of waste by composting converts organic waste into valuable organic supplements. Physicochemical characteristics of tomato waste (TW) limit the efficiency of the composting process. To overcome these challenges, different mixtures were investigated by integration of olive pumice (OP), sheep manure (SM), chicken manure (CM), and sawdust as bulking agents for the optimization of the composting process. Evaluations of the composting process and compost quality were carried out to measure the temperature profile, organic matter (OM) losses, concentrations of humic substances, and macro-nutriments. The results showed that the type and ratio of feedstock in the mixture influenced the temperature of the composting process. In mixtures with SM and OP, the temperature exceeded 55 °C for more than 2 weeks, ensuring hygienization. Additionally, phosphorus and potassium significantly increased when SM and CM were added to the composting mixture. The addition of OP increased the concentrations of humic acid-like carbon (C_HA) and fulvic acid-like carbon (C_FA). Higher content of humic substances was recorded when SM and OP were used as composting feedstock. Using SM in the mixture was found to be more efficient than CM and constitutes a suitable feedstock for composting of tomato waste, achieving successful co-operation of agronomic and animal farm sectors.

Advanced Characterization of Organic Matter Decaying during Composting of Industrial Waste Using Spectral Methods

To date, compost maturation monitoring is carried out by physical-chemical and microbiological analysis, which could be considered an overweening consumption of time and products. Nowadays, spectroscopy is chosen as a simple tool for monitoring compost maturity. In the present investigation, spectroscopy analysis was performed in the interest of corroborating the compost maturity. This goal was achieved by using the X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. X-ray diffraction analysis showed the presence of the cellulose fraction in compost samples. At the same time, the intensity of pics decreased depending on composting time, thus proving that there was organic matter degradation. Infrared and scanning electron microscopy analysis allow for confirming these results. The correlation between spectroscopies analysis and physical-chemical properties was employed by partial least squares-regression (PLS-R) model. PLS-R model was applied to build a model to predict the compost quality depending on the composting time, the results obtained show that all the parameters analysis are well predicted. The current study proposed that final compost was more stabilized compared with the initial feedstock mixture. Ultimately, spectroscopy techniques used allowed us to confirm the physical-chemical results obtained, and both of them depict maturity and stability of the final compost, thus proving that spectral techniques are more reliable, fast, and promising than physical-chemical analyses.

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.

Magnetite-Functionalized Horse Dung Humic Acid (HDHA) for the Uptake of Toxic Lead(II) from Artificial Wastewater

Magnetite-functionalized horse dung humic acid (HDHA) has been successfully prepared by the coprecipitation method, and the as-prepared adsorbent (MHDHA) has been applied as an easy-handling adsorbent for toxic Pb(II) in artificial wastewater. The MHDHA was characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), and vibrating sample magnetometer (VSM). The FT-IR study showed that the MHDHA had the characteristics peaks of HA and Fe-O stretching. The XRD analysis revealed that the MHDHA had the $2\theta$ characteristic for magnetite. The TEM image and EDX analysis exhibited that the MHDHA with an average size of ∼14 nm was partially aggregated and contained ( $w/w$ ) 9.89% carbon, 2.89% nitrogen, and 32.74% oxygen based on functional groups of HDHA. The stability improvement of MHDHA was showed by decreasing HDHA dissolved from 95% to less than 30% at pH 12 after magnetite functionalization. The post-adsorption handling improvement was evidenced by easy and quick retraction by an external magnet with a 62.95 emu/g magnetic strength value. The adsorption capacities were influenced by the pH and ionic strength, whilst the adsorption rates were well simulated by the Ho pseudo-second-order model. The removal uptake of Pb(II) ions increased when the initial concentration was increased and fitted well with the Langmuir isotherm model when the monolayer adsorption capacity was $2.78\times {10}^{-4}\text{mol}/\text{g}$ (equal to 57.64 mg/g). The value of Dubinin-Radushkevich adsorption energy ( $E_{D-R}$ ) found in this study was 14.78 kJ/mol, which implied that ion exchange is the main mechanism involved in the adsorption process. The regeneration studies of MHDHA show that there was no significant change in composition, morphology, crystallinity, and functional group after five consecutive cycles of the adsorption-desorption process.

Applying synchronous fluorescence and UV-vis spectra combined with two-dimensional correlation to characterize structural composition of DOM from urban black and stinky rivers

UV-visible spectroscopy and synchronous fluorescence spectroscopy (SFS) combined with two-dimensional correlation spectroscopy (2D-COS) were applied for extracting fluorescence components, tracing organic functional groups, and revealing variations of dissolved organic matter (DOM) in Puhe River. Water samples were collected from the mainstream and two tributaries (Nanxiaohe River and Huangnihe River). DOM in three rivers was composed of protein-like fluorescent (PLF), microbial humus-like fluorescent (MHLF), fulvic-like fluorescent (FLF), and humic-like fluorescent components, which were relative to aromatic groups, phenolic groups, carboxylic groups, and microbial products. The PLF and MHLF were dominated in DOM fractions in the rivers, and the average content of the PLF was the highest in Nanxiaohe River. Humification degree of DOM was the highest in Puhe River, followed by Huangnihe River and Nanxiaohe River. However, molecular mass of DOM in Puhe River was the lowest, followed by Huangnihe River and Nanxiaohe River. Based on the 2D-COS of the SFS and UV-visible spectra, the variation order of DOM fractions in Puhe River was PLF → MHLF → FLF, and the PLF was consistent with the phenolic groups, aromatic groups, and carboxylic groups, but the adverse trend with the microbial products. The variation order in Nanxiaohe River was MHLF → PLF → FLF, and the MHLF was consistent with the aromatic groups, phenolic groups, carboxylic groups, and microbial products. The variation order in Huangnihe River was MHLF → PLF → FLF too, and the PLF was consistent with the carboxylic groups and aromatic groups. The results of the present study demonstrate that UV-visible spectroscopy and SFS combined with 2D-COS are useful methods to characterize structural composition of DOM from urban black and stinky rivers so as to investigate their pollution status.

Characteristics of Fluorescence Spectra, UV Spectra, and Specific Growth Rates during the Outbreak of Toxic Microcystis Aeruginosa FACHB-905 and Non-Toxic FACHB-469 under Different Nutrient Conditions in a Eutrophic Microcosmic Simulation Device

Microcystis aeruginosa is the dominant alga forming cyanobacteria blooms, the growth of which is limited by available nutrients. Thus, it is necessary to study cyanobacteria blooms and explore the growth of Microcystis aeruginosa under different nutrient conditions. In this paper, we take Microcystis aeruginosa, including toxic Freshwater Algae Culture of Hydrobiology Collection (FACHB)-905 and non-toxic FACHB-469 strains, into account. The strains were cultured using a simulation device under different nutrient conditions. Ultraviolet spectra, three-dimensional fluorescence spectra, and kinetic parameter indicators of the two species are studied. Compared to FACHB-469, the results show that the specific growth rate of FACHB-905 is much higher, in particular, FACHB-905 is the dominant species under low nutrient conditions. Furthermore, the UV spectral characteristics indicate that the molecular weight of dissolved organic matter in the culture tank of toxic FACHB-905 is greater than that of FACHB-469. Additionally, the humification index of toxic FACHB-905 is slightly higher as well, which suggests that it is more stable in the presence of dissolved organic matter during blooms. Therefore, the toxic Microcystis strain is more likely to become the dominant species in water blooms under lower eutrophic conditions and water blooms formed by the toxic Microcystis strain may be more difficult to recover from.

Effect of pyrolysis temperature on the composition of DOM in manure-derived biochar

Dissolved organic matter (DOM) plays an important role in the migration and transformation of nutrients and pollutants. Recently, DOM derived from biochar has the potential to determine the application of biochar and has attracted much researcher's attention. However, the effects of pyrolysis temperature on the composition evolution of DOM in manure-derived biochar are still unclear. In this study, DOM solutions extracted from a series of biochars derived from three kinds of manure (chicken, swine and dairy) at six pyrolysis temperature (200-700 °C) were analyzed using UV-Visible, Fourier transform infrared and fluorescence spectroscopy, aiming to investigate the effects of pyrolysis temperature on the composition evolution of DOM. The results showed that, with the increased of pyrolysis temperature, the dissolved organic matter (DOC) content sharply declined to reach stable. High DOC content was obtained at low pyrolysis temperature. Moreover, the DOM mainly contained humic acid-like and protein-like substances. With the pyrolysis temperature increased, the protein-like substances firstly decreased and then increased, while there was an opposite trend for the humic acid-like substances. Moreover, functional groups evolution of DOM depended on the pyrolysis temperature and manure type, evidenced by the Fourier transform infrared spectroscopy with two-dimensional correlation analysis. This study highlights the importance of optical analysis and may provide valuable information regarding the characteristics evolution of biochar-derived DOM.

Evolution of Microbial Composition and Enzymatic Activities during the Composting of Textile Waste

The production of stable and mature compost often depends on the performance of microbes and their enzymatic activity. Environmental and nutritional conditions influence the characteristics of microbial communities and, therefore, the dynamics of major metabolic activities. Using three waste mixtures (textile waste mixed with either green, paper, or cardboard waste), the maturity of the compost produced was assessed by following the physico-chemical parameters and enzymatic activities provided by the microorganisms that were identified using next-generation sequencing (NGS). Among the three mixtures used, it was found that the two best mixtures showed C/N ratios of 16.30 and 16.96, total nitrogen of 1.37 and 1.39%, cellulase activities of 50.62 and 52.67 Ug−1, acid phosphatase activities of 38.81 and 68.77 Ug−1, and alkaline phosphatase activities of 51.12 and 56.86 Ug−1. In addition, several lignocellulosic species, together with those that are able to solubilize phosphate, were identified. Among those known for cellulase and acid/alkaline phosphatase activities, bacteria belonging to the Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes phyla were shown. The presence of species belonging to the Ascomycota and Basidiomycota phyla of Fungi, which are known for their ability to produce cellulase and acid/alkaline phosphatases, was demonstrated. These findings provide a basis for the production of stable and mature compost based on textile waste.

Investigation of eluted characteristics of fulvic acids using differential spectroscopy combined with Gaussian deconvolution and spectral indices

The characteristics of subfractions of soil fulvic acid (FA₃, FA₅, FA₇, FA₉, and FA₁₃) using stepwise elution from XAD-8 resin with pyrophosphate buffers were investigated by differential absorption spectroscopy (DAS) and differential fluorescence spectroscopy (DFS) combined with mathematical deconvolution and spectral indices. The log-transformed absorbance spectra (LTAS) exhibited three regions for both acidic-buffer-eluted subfractions (AESF) and neutral-buffer-eluted subfraction (NESF) and four regions for basic-buffer-eluted subfractions (BESF) according to the differences in spectral slopes. The DAS spectra of FA subfractions were closely fitted with seven Gaussian bands with maxima location at 199.66, 216.18 ± 1.50, 246.20 ± 3.85, 285.22 ± 7.26, 345.64 ± 5.30, 389.27, and 307.37 nm, respectively (R² > 0.993). The content of salicylic-like and carboxyl groups in FA subfractions decreased, while the phenolic chromophore increased with elution sequence. From the 11 spectral indices, AESF had greater molecular weight, condensation, polymerization, hydroxyl radical production, humification degree, and terrigenous contribution, as well as contained more conjugated aromatic structures and less N-containing groups than NESF and BESF. The humification degree and humic characters of FA subfractions were closely associated to the aromaticity, molecular condensation, and DOM-metal-bound functional groups. The proper separation of FA into subfractions is beneficial for reducing its complexity and heterogeneity, which helps us to further explore its chemical properties and interactions with various contaminants in soil environments. Graphical abstract.

Study of the morphological changes of copper and zinc during pig manure composting with addition of biochar and a microbial agent

Intensive and unregulated use of feed additives in China has led to high levels of heavy metals such as copper and zinc in fertilizers, considerable quantities of which find their way into the environment. Studies have shown that composting could significantly decrease the bioavailability of heavy metals. This study was to investigate the effects of addition of biochar and a microbial agent on the morphological changes in copper and zinc during composting. Results show that treatment T8 successfully immobilized 70.36% of copper as a result of biochar addition. Treatment T3 successfully immobilized 40.76% of zinc; transformation of zinc to a higher stable state was found to be closely related to the formation of fulvic and humic acids. Results of fluorescence spectrum analysis also corroborate that the conversion of copper and zinc to forms with higher stability was associated with the formation of fulvic and humic acid-like substances.

The Structural Arrangement and Relative Abundance of Aliphatic Units May Effect Long-Wave Absorbance of Natural Organic Matter as Revealed by 1H NMR Spectroscopy

The objective of this study was to shed light on structural features which underlay intensity of long wave absorbance of natural organic matter (NOM) using ¹H NMR spectroscopy. For this purpose, a set of the NOM samples was assembled from arctic and nonarctic sampling sites (the Kolyma river basin and Moscow region, respectively). It was to ensure a substantial difference in the humification degree of the isolated organic matter-the biogeochemical proxy of the long-wave absorbance of NOM. The assembled NOM set was analyzed using solution-state ¹H NMR spectroscopy. The distribution of both backbone and exchangeable protons was determined using acquisition of spectra in three different solvents. The substantially higher contribution of nonfunctionalized aliphatic moieties CHn (e.g., materials derived from linear terpenoids, MDLT) in the arctic NOM samples was revealed as compared to the nonarctic ones. The latter were characterized with the higher content of CHα protons adjacent to electron-withdrawing groups which belong to carboxyl rich alicyclic moieties (CRAMs) or to aromatic constituents of NOM. We have calculated a ratio of CHn to CHα protons as a structural descriptor which showed significant inverse correlation to intensity of long wave absorbance assessed with a use of E₄/ E₆ ratio and the slope of absorption spectrum. The steric hindrance of aromatic chromophoric groups of the NOM ensemble by bulky nonfunctionalized aliphatic moieties (e.g., MDLT) was set as a hypothesis for explanation of this phenomenon. The bulky aliphatics might increase a distance between the interacting groups resulting in inhibition of electronic (e.g., charge-transfer) interactions in the NOM ensemble. The obtained relationships were further explored using Fourier transform mass spectrometry as complementary technique to ¹H NMR spectroscopy. The data obtained on correlation of molecular composition of NOM with ¹H NMR data and optical properties were very supportive of our hypothesis that capabilities of NOM ensemble of charge transfer interactions can be dependent on structural arrangement and relative abundance of nonabsorbing aliphatic moieties.

Composting of smuggled cigarettes tobacco and industrial sewage sludge in reactors: Physicochemical, phytotoxic and spectroscopic study

The maturity of smuggled cigarette tobacco (SCT) and industrial sewage sludge (ISS) compost during composting in reactors was evaluated through physicochemical, phytotoxic and spectroscopic parameters. The temperatures reached peaks above 52 °C in the three reactors and were enough to achieve the stability of the compounds. The electric conductivity was in the optimal interval for farming uses and the pH alkaline band was favorable to produce inorganic nitrogen. The reduction in the C∕N ratio and the increase in cation exchange capacity (CEC) indicated an increase in the compost humification. After 120 days, the seed germination index (SGI) reached 95 % in reactor 3. In the three treatments, the reduction in E2/E6 and E4/E6 ratios (UV/Vis), the increase in humification indices, obtained through FTIR and the aromatic carbon resonance (13C NMR) indicated a high degree of aromaticity. The composting process in reactors was efficient to degrade different proportions of SCT and ISS, resulting in mature composts.

Fluvial dissolved organic carbon composition varies spatially and seasonally in a small catchment draining a wind farm and felled forestry

Assessing whether land use, from activities such as wind farm construction and tree-felling, impacts on terrestrial C delivery to rivers has focused on quantifying the loss of dissolved organic carbon (DOC), and not the composition changes. Here we explore how land use influences DOC composition by considering fluvial DOC concentration, [DOC], and spectrophotometric composition of a river draining a peat-rich catchment. We find that in this 5.7km² catchment differences occur in both the concentration and composition of the DOC in its sub-catchments. This is attributed to differences in how land was used: one tributary (D-WF) drains an area with wind farm construction and forestry in the headwaters, and one tributary (D-FF) drains an area with felled plantation trees. Generally, [DOC] in both streams showed similar seasonal variation, and autumn maxima. However, the felled catchment had greater mean [DOC] than the wind farm catchment. The SUVA₂₅₄ and E₄/E₆ indicated DOC in both streams had similar aromaticity and fulvic:humic acid for most of the time, but SUVA₄₁₀ and E₂/E₄ indicated less DOC humification in the felled catchment. This may be due to young DOC from the breakdown of residual branches and roots, or more humification in soils in the wind farm area. During the dry months, DOC composition showed more spatial variation: the D-WF DOC had smaller SUVA₂₅₄ (less total aromatic material) and SUVA₄₁₀ (fewer humic substances). The decreased E₂/E₄ in both streams indicated the total aromatic carbon decreased more than humic substances content. Moreover, the larger E₄/E₆ for D-WF in summer indicated that the humic substances were richer in fulvic acids than humic acids. Soil disturbance associated with forestry-felling likely contributed to the higher [DOC] and release of less-humified material in D-FF. This research indicates drivers of different DOC concentration and composition can exist even in small catchments.

Variation in the Humification Degree of Dissolved Organic Matter from Cattle Manure during Composting as Analyzed by Ultraviolet-Visible and Fluorescence Spectroscopy

This study investigated the degree of humification of dissolved organic matter (DOM) during different periods of cattle manure composting using ultraviolet-visible (UV-vis) and fluorescence spectroscopy (emission, synchronous scan, and excitation-emission matrix) and determined which method is more suitable for analysis of the humification degree of DOM. Two composting piles were prepared by mixing manure and corn straw. One pile (Pile A [PA]) contained inoculated exogenous composite agents at a ratio of 2% (v/v), and a pile without the addition of inoculants (PNA) served as the control treatment. The results showed that ultraviolet integrated absorption intensities in the range of 226 to 400 nm and 260 to 280 nm and specific ultraviolet absorbances at 254 and 280 nm of both PA and PNA gradually increased with composting time. Based on the fluorescence regional integration analysis and parallel factor analysis, the humic-like substances became the main components of the DOM after composting. Our study demonstrated that the humification degree of DOM was enhanced during composting and that the inoculation composite agent was beneficial for the humification of DOM at the mesophilic and thermophilic phases of the composting process. Moreover, the results of correlation analysis and principal component analysis demonstrated that the fluorescence spectral parameters evaluated the humification degree of DOM during the whole cattle manure composting process better than the UV-vis spectral parameters.

Characterization of dissolved organic matter in Dongjianghu Lake by UV-visible absorption spectroscopy with multivariate analysis

UV-visible absorption spectroscopy coupled with principal component analysis (PCA) and hierarchical cluster analysis (HCA) was applied to characterize spectroscopic components, detect latent factors, and investigate spatial variations of dissolved organic matter (DOM) in a large-scale lake. Twelve surface water samples were collected from Dongjianghu Lake in China. DOM contained lignin and quinine moieties, carboxylic acid, microbial products, and aromatic and alkyl groups, which in the northern part of the lake was largely different from the southern part. Fifteen spectroscopic indices were deduced from the absorption spectra to indicate molecular weight or humification degree of DOM. The northern part of the lake presented the smaller molecular weight or the lower humification degree of DOM than the southern part. E_2/4, E_3/4, E_2/3, and S₂ were latent factors of characterizing the molecular weight of DOM, while E_2/5, E_3/5, E_2/6, E_4/5, E_3/6, and A_2/1 were latent factors of evaluating the humification degree of DOM. The UV-visible absorption spectroscopy combined with PCA and HCA may not only characterize DOM fractions of lakes, but may be transferred to other types of waterscape.

Evaluation of dredged sediment co-composted with green waste as plant growing media assessed by eco-toxicological tests, plant growth and microbial community structure

Dredged sediments have currently no broad reuse options as compared to other wastes due to their peculiar physico-chemical properties, posing problems for the management of the large volumes of sediments dredged worldwide. In this study we evaluated the performance of sediment (S) co-composted with green waste (GW) as growing medium for ornamental plants. Analysis of the microbial community structure, eco-toxicological tests, were conducted on sediments at 1:1 and 3:1S:GW composting ratios. Sediment-based growing media were then reused to growth the ornamental plant Photina x fraseri in a pilot-scale experiment and plants' physiological and chemical parameters were measured. The results showed that co-composting with green waste increased the diversity of bacteria, fungi and archaea as compared to the untreated sediments, and that both the 1:1 and 3:1 S:GW composted sediments had no substantial eco-toxicological impacts, allowing an excellent plant growth. We concluded that co-composted of sediment with green waste produce a growing medium with suitable properties for growing ornamental plants, and represent a sustainable option for beneficial use of dredged sediments.

Role of biochar on composting of organic wastes and remediation of contaminated soils-a review

Biochar is produced by pyrolysis of biomass residues under limited oxygen conditions. In recent years, biochar as an amendment has received increasing attention on composting and soil remediation, due to its unique properties such as chemical recalcitrance, high porosity and sorption capacity, and large surface area. This paper provides an overview on the impact of biochar on the chemical characteristics (greenhouse gas emissions, nitrogen loss, decomposition and humification of organic matter) and microbial community structure during composting of organic wastes. This review also discusses the use of biochar for remediation of soils contaminated with organic pollutants and heavy metals as well as related mechanisms. Besides its aging, the effects of biochar on the environment fate and efficacy of pesticides deserve special attention. Moreover, the combined application of biochar and compost affects synergistically on soil remediation and plant growth. Future research needs are identified to ensure a wide application of biochar in composting and soil remediation. Graphical abstract ᅟ.

Assessment of mobility and bioavailability of mercury compounds in sewage sludge and composts

Content of heavy metals, including mercury, determines the method of management and disposal of sewage sludge. Excessive concentration of mercury in composts used as organic fertilizer may lead to accumulation of this element in soil and plant material. Fractionation of mercury in sewage sludge and composts provides a better understanding of the extent of mobility and bioavailability of the different mercury species and helps in more informed decision making on the application of sludge for agricultural purposes. The experimental setup comprises the composing process of the sewage sludge containing 13.1mgkg^-1 of the total mercury, performed in static reactors with forced aeration. In order to evaluate the bioavailability of mercury, its fractionation was performed in sewage sludge and composts during the process. An analytical procedure based on four-stage sequential extraction was applied to determine the mercury content in the ion exchange (water soluble and exchangeable Hg), base soluble (Hg bound to humic and fulvic acid), acid soluble (Hg bound to Fe/Mn oxides and carbonates) and oxidizable (Hg bound to organic matter and sulphide) fractions. The results showed that from 50.09% to 64.55% of the total mercury was strongly bound to organo-sulphur and inorganic sulphide; that during composting, increase of concentrations of mercury compounds strongly bound with organic matter and sulphides; and that mercury content in the base soluble and oxidizable fractions was strongly correlated with concentration of dissolved organic carbon in those fractions.

Composting technology in waste stabilization: On the methods, challenges and future prospects

Composting technology has become invaluable in stabilization of municipal waste due to its environmental compatibility. In this review, different types of composting methods reportedly applied in waste management were explored. Further to that, the major factors such as temperature, pH, C/N ratio, moisture, particle size that have been considered relevant in the monitoring of the composting process were elucidated. Relevant strategies to improve and optimize process effectiveness were also addressed. However, during composting, some challenges such as leachate generation, gas emission and lack of uniformity in assessing maturity indices are imminent. Here in, these challenges were properly addressed and some strategies towards ameliorating them were proffered. Finally, we highlighted some recent technologies that could improve composting.

Wastewater Biosolid Composting Optimization Based on UV-VNIR Spectroscopy Monitoring

Conventional wastewater treatment generates large amounts of organic matter-rich sludge that requires adequate treatment to avoid public health and environmental problems. The mixture of wastewater sludge and some bulking agents produces a biosolid to be composted at adequate composting facilities. The composting process is chemically and microbiologically complex and requires an adequate aeration of the biosolid (e.g., with a turner machine) for proper maturation of the compost. Adequate (near) real-time monitoring of the compost maturity process is highly difficult and the operation of composting facilities is not as automatized as other industrial processes. Spectroscopic analysis of compost samples has been successfully employed for compost maturity assessment but the preparation of the solid compost samples is difficult and time-consuming. This manuscript presents a methodology based on a combination of a less time-consuming compost sample preparation and ultraviolet, visible and short-wave near-infrared spectroscopy. Spectroscopic measurements were performed with liquid compost extract instead of solid compost samples. Partial least square (PLS) models were developed to quantify chemical fractions commonly employed for compost maturity assessment. Effective regression models were obtained for total organic matter (residual predictive deviation-RPD = 2.68), humification ratio (RPD = 2.23), total exchangeable carbon (RPD = 2.07) and total organic carbon (RPD = 1.66) with a modular and cost-effective visible and near infrared (VNIR) spectroradiometer. This combination of a less time-consuming compost sample preparation with a versatile sensor system provides an easy-to-implement, efficient and cost-effective protocol for compost maturity assessment and near-real-time monitoring.

Comparison of the bacterial composition of two commercial composts with different physicochemical, stability and maturity properties

Previously, two municipal solid waste commercial composts (MSW1 and MSW2) were characterized. Although sharing the same type of raw material, most of their physicochemical, stability and maturity properties differed. The present study aimed to characterize them at a microbiological level, and to infer on possible relationships between the composts properties and the structure of their bacterial communities. Both the 16S rRNA gene-based PCR-DGGE profiling and 454-pyrosequencing technology showed that the structure of the bacterial communities of these composts was distinct. The bacterial community of MSW1 was more diverse than that of MSW2. Multivariate analyses revealed that the high electrical conductivity, Cu content as well as the low phytotoxity of compost MSW1, when compared to MSW2, contributed most to shape its bacterial community structure. Indeed, high abundance of halophilic (Halomonadaceae and Brevibacteriaceae) and metal resistant organisms (Brevibacteriaceae and Bacillaceae) were found in MSW1. In addition, Pseudonocardiaceae, Streptomycetaceae, Bacillaceae, and Brevibacteriaceae may have contributed to the high humic-like acids content and low phytotoxicity of MSW1. In contrast, the high organic matter content and the high density of the cultivable fungi population were the parameters most correlated with the structure of the bacterial community of compost MSW2, dominated by Corynebacteriaceae and mainly Aerococcaceae, taxonomic groups not commonly found in composts.

Characterization of Matured Vermicompost Derived from Valorization of Palm Oil Mill Byproduct

The valorization process involves transforming low-value materials such as wastes into high-value-added products. The current study aims to determine the potential of using a valorization process such as vermicomposting technology to convert palm oil mill byproduct, namely, decanter cake (DC), into organic fertilizer or vermicompost. The maturity of the vermicompost was characterized through various chemical and instrumental characterization to ensure the end product was safe and beneficial for agricultural application. The vermicomposting of DC showed significantly higher nutrient recovery and decreases in C:N ratio in comparison with the controls, particularly in the treatment with 2 parts DC and 1 part rice straw (w/w) (2DC:1RS). 2DC:1RS vermicompost had a final C:N ratio of 9.03 ± 0.12 and reasonably high levels of calcium (1.13 ± 0.05 g/kg), potassium (25.47 ± 0.32 g/kg), magnesium (4.87 ± 0.19 g/kg), sodium (7.40 ± 0.03 g/kg), and phosphorus (3.62 ± 0.27 g/kg). In addition, instrumental characterization also revealed a higher degree of maturity in the vermicompost. Ratios of 2921:1633 and DTG2:DTG3 also showed significant linear correlations with the C:N ratio, implying that those ratios could be used to characterize the progression of vermicompost maturity during the valorization process of DC.

Transformation of dissolved organic matters in swine, cow and chicken manures during composting

The changes of dissolved organic matters (DOMs) extracted from swine, cow and chicken manures were assessed by Fourier transform infrared, ultraviolet, gel permeation chromatography (GPC), excitation-emission-matrix fluorescence (EEM-FL), Biolog Eco and (1)H NMR during 60-day composting. Pumice was adopted to eliminate the disturbing of common organic bulking agents. The results showed chicken manure had the highest DOC, DTN (dissolved total nitrogen) and lowest DOC/DTN among the three manures; cow manure had the highest volatile solids, lowest DTN, slowest DOMs hydrolysis rate and the fastest bio-stabilization rate. (1)H NMR showed the decrease rates of OC band and saturated carbon chain were distinctly faster than that of olefinic and aromatic structures. The molecular size distribution of DOMs in the three manures was in the range of 1-10 kDa detected by GPC. Microbial carbon utilization capacity decreased in cow manure with composting time, but the contrast was observed in the chicken and swine manures.

Compost and crude humic substances produced from selected wastes and their effects on Zea mays L. nutrient uptake and growth

Production of agriculture and timber commodities leads generation of enormous quantity of wastes. Improper disposal of these agroindustrial wastes pollutes the environment. This problem could be reduced by adding value to them. Therefore, a study was carried out to analyse and compare the nutrients content of RS, RH, SD, and EFB of composts and crude humic substances; furthermore, their effect on growth, dry matter production, and nutrient uptake for Zea mays L., and selected soil chemical properties were evaluated. Standard procedures were used to analyze humic acids (HA), crude fulvic acids (CFA), crude humin (CH), soil, dry matter production and nutrient uptake. Sawdust and RS compost matured at 42 and 47 days, respectively, while RH and EFB composts were less matured at 49th day of composting. Rice straw compost had higher ash, N, P, CEC, HA, K, and Fe contents with lower organic matter, total organic carbon, and C/N and C/P ratios. The HA of sawdust compost showed higher carbon, carboxylic, K, and Ca contents compared to those of RS, RH, and EFB. Crude FA of RS compost showed highest pH, total K, Ca, Mg, and Na contents. Crude humin from RS compost had higher contents of ash, N, P, and CEC. Rice straw was superior in compost, CFA, and CH, while sawdust compost was superior in HA. Application of sawdust compost significantly increased maize plants' diameter, height, dry matter production, N, P, and cations uptake. It also reduced N, P, and K based chemical fertilizer use by 90%. Application of CH and the composts evaluated in this study could be used as an alternative for chemical fertilizers in maize cultivation.

Recovery of humic-like susbtances from low quality composts

The quality of four commercial composts produced from poultry litter and municipal solid wastes was assessed based on their physic-chemical, stability and maturity parameters. These properties varied among the analysed composts; it was found that electric conductivity, heavy metals content and maturity were the parameters that limited the composts quality. Therefore, the feasibility of using them to obtain liquid fertilisers rich in humic-like substances (HS) was assessed. The HS yield, phytotoxicity, heavy metals co-extraction and chemical characterization were carried out. The linkage of the HS chemical composition with the compost properties was assessed by multivariate analysis. Among the compost properties, germination indices, Cr and Cu contents were the parameters that correlated most with the HS chemical composition. The low levels of metals and absence of phytotoxicity in all the analysed HS extracts indicate that composts with low quality may be used to produce liquid organic fertilisers, substituting those from natural resources.

Bioaugmented composting of Jatropha de-oiled cake and vegetable waste under aerobic and partial anaerobic conditions

This study was conducted to assess the effect of microbial inoculation in Jatropha cake composting with different vegetable waste. The microbial inoculums composed of fungal strains (Aspergillus awamori, Aspergillus nidulans, Trichoderma viride, Phanerochaete chrysosporium) and bacterial inoculums (Pseudomonas striata as phosphorus solublizer and Azotobacter chroococcum as nitrogen fixer) were added to the compost mixture after the thermophilic phase was over for bioaugmenting of Jatropha cake under aerobic and partial anaerobic conditions. Addition of both fungal and bacterial inoculum with mixed substrate (Jatropha cake + vegetable waste) during composting (aerobic and partial anaerobic) showed, better results as compared to compost with only fungal inoculants. Increased enzymatic activity initially, during composting (like dehydrogenase, alkaline phosphatase activity and FDA) proved role of inoculated microbes in rapid decomposition. Analysis of compost (with both bacterial and fungal inoculum) showed presence of high humus (12.7%), humic acid (0.5%), fulvic acid (5.68%), soluble protein content and low C/N ratio. Decreased in concentration of extractable metals (Cu, Fe and Mn) were recorded at maturity in all the substrate composts. The C/N ratio was significantly correlated to parameters like humic acid, humus, fulvic acid, protein and also microbial activity parameters. We conclude that the composting of de-oiled Jatropha cake with different vegetables waste could be feasible and sustainable approach in recycling of agricultural and industrial residues in huge quantities.

Co-composting of physic nut (Jatropha curcas) deoiled cake with rice straw and different animal dung

To address the dispensing of this growing volume, a study on utilization of jatropha (Jatropha curcas) deoiled cake through compost production was carried out. The deoiled cake was composted with rice straw, four different animal dung (cow dung, buffalo dung, horse dung and goat dung) and hen droppings in different proportions followed by assessment, and comparison of biochemical characteristics among finished composts. Nutrient content in finished compost was within the desired level whereas metals such as copper, lead and nickel were much below the maximum allowable concentrations. Although a few finished material contained phorbol ester (0.12 mg/g), but it was far below the original level found in the deoiled cake. Such a study indicates that a huge volume of jatropha deoiled cake can be eliminated through composting.