Compost Humic Acid Research Articles

Study the effect of two organic fertilizers, methods of fertilization on productivity, pests and predatory insects associated with eggplant under modified climatic condition

This study investigated the effects of two organic fertilizer (compost tea and humic acid) compared to chemical fertilizer on plant growth, productivity, pests and predatory insects associated with eggplant Solanum melongena var. Black beauty under net house in 1st of April at 2019 and 2020 seasons. Application of fertilizers through fertigation enhanced significantly number of leaves, stem fresh weight, average fruit weight and total fruit yield. Moreover, stem diameter, nitrogen content in leaves (%), phosphorus content in leaves (%), potassium content in leaves (%), number of fruits and total yield were enhanced significantly due to using compost tea. However, using the humic acid cause a significant enhancement in number of shoots, number of leaves, stem diameter and leaves fresh weight. In addition, application of compost tea through the fertigation cause a significant superiority in number of shoots, nitrogen content in leaves (%), phosphorus content in leaves (%), potassium content in leaves (%), number of fruits, average fruit weight and total yield. The highest significant values of leaves fresh weight and stem dry weight were mainly due using humic acid through foliar application. Three main pest species and seven different predators' species were recorded associated with pests on eggplant. The application of foliar and fertigation compost tea increased pest populations significantly compared with humic acid and control. But also, increase the predators' population.

Effects of amendments on the bioavailability, transformation and accumulation of heavy metals by pakchoi cabbage in a multi-element contaminated soil.

This study aims to assess the effect of green waste compost (GWC), biochar (BC) and humic acid (HA) amendments of an alkaline heavy metal-contaminated soil. In this study, amendments with GWC, GWC + BC and GWC + HA were applied to the heavy metal-contaminated soil in four application rates (0, 1, 2 and 5%), and was aimed at substantially mitigating the bioavailability of heavy metals for pakchoi cabbage from the sewage irrigation soils. The addition of different ratios of amendments can increase the pH of the soil by 0.11–0.30 units and also increase the organic matter content by 3.1–35.1%. The concentration of available arsenic (As), cadmium (Cd), zinc (Zn) and copper (Cu) in the CaCl2 extract was decreased effectively by all the amendments, except for the increase in the available concentration of As by compost–humic acid (T8) in the soil. Compared with the control, the CaCl2 extractable Cd was decreased by 33–48% after the addition of different ratios of amendments in the soil. Moreover, by increasing the content of compost and compost–biochar in combinations, easily exchangeable fractions of As, Cd, Zn and Cu were decreased, while the oxidation fraction and residual fractions were increased. When the soil amendments were applied, fresh weight of the root and shoot increased by 29–63% and 39–85%, respectively. Cd concentration in the roots and shoots of the pakchoi cabbage decreased by 21–44% and 26–53%, respectively, after adding different ratios of amendments. All the amendments were effective in reducing the Cd, Zn and Cu uptake by the roots and shoots of the pakchoi cabbage, and simultaneously reduce the absorption of As in the roots of pakchoi cabbage. As soil amendments, GWC alone or GWC + BC/GWC + HA application can significantly reduce the heavy metal levels in pakchoi cabbage while increasing the biomass production and higher application rate is more effective than the lower application rate.

Biodegradation and Structural Modification of Humic Acids in a Compost Induced by Fertilization with Steelmaking Slag under Coastal Seawater, as Detected by TMAH-py-GC/MS, EEM and HPSEC Analyses.

The compost's humic acid (HA) content decreased when it was fertilized in coastal seawater with steelmaking slag, as confirmed. This study clarified the cause for this change by a detailed analysis of the structural changes in HAs based on the TMAH-py-GC/MS, HPSEC, and 3D-EEM spectra. An increase in the levels of pyrolysates of tannic acid with a low polymerization degree was attributed to the biodegradation of a high polymerized aromatic structure. Moreover, analyses of 3D-EEM, supported by HPSEC, indicated that approximately 20 kDa of the fluorescent matter was generated at the protein-like peaks (Ex/Em = 220/340 and 275/350 nm) in HAs derived from a mixture of compost with steelmaking slag. It would be caused due to the formation of HAs from the bacterial by-product by a catalytic reaction of the steelmaking slag. From these findings reported herein, we conclude that bio-degradation was a major reason for the decreased HA content, and the formation of HA from a part of the degradation products. This would be a reason for the structural modification of HA under the seawater condition.

Hydrothermal oxidation method to synthesize nitrogen containing carbon dots from compost humic acid as selective Fe(III) sensor

Residual sludge which is generated as a by-product during wastewater treatment needs efficient and environmentally friendly disposal. In this work, nitrogen containing carbon dots (N-CDs) was synthesized via one-step hydrothermal oxidation of humic acid for the first time, which was alkalinely extracted from the compost of sludge. The successful doping of the functional groups (hydroxyl, carboxyl and amino) on the surface of N-CDs were characterized by x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The optical properties of the synthetic N-CDs were obtained from Ultraviolet-visible spectroscopy and Photoluminescence spectra. The N-CDs had an average diameter at 1.88 nm and exhibited a well-defined spherical shape. The aqueous solution of N-CDs with excitation-dependent properties showed a strong blue emission with 8.8% quantum yield (QY) under an excitation wavelength of 340 nm, which indicate the synthesized N-CDs a promising sensing probes for iron ions in aquatic system. Moreover, the mechanism of the N-CDs sensing technique was investigated in detail, which can be explained by the fluorescence static quenching effect and a ground-state complex formed in this process. This research demonstrates an extremely sensitive method for detecting heavy metal Fe3+ at a lower 1.9 nM level by using N-CDs as fluorescent probes without a complicated procedure.

Pengaruh Komposisi Pupuk Organik Terhadap Pertumbuhan Bibit Budchip Tanaman Tebu (Saccharum officinarum L.)

Breeding of bud chip cane is an application of ratoon unloading program which often get difficulty fulfilling the requirement of certified seed. Efforts to increase production and restoration of soil fertility can be done application of organic fertilizer compost humic acid, kiambang, and manure. The study aims to get the best bud bud chips. Getting the most effective dose of organic fertilizer composition. and get the interaction of seed bud bud part and organic fertilizer composition. The research method used Group Random Design. The first factor is 3 parts of seedlings (B1) bud seed bud chip (B2) bud seed bud chips the middle, (B3) bud seed bud chip, and second factor amount of composition of organic fertilizer (P) comparison Humic Acid: Kiambang: : (P0) 10%: 70%: 20% (P3) 20%: 10%: 70%, (P4) 30%: P0) without organic fertilizer (P1) 30%: 40%, (P5) 100% humic acid organic fertilizer, (P6) 100% kiambang compost, and (P7) 100% manure. the results of the observations were analyzed by the analysis of variance with the F test, in the Advanced Test with the BNT Test at the 5% level of confidence. The results showed bud buds chip B1 growth faster than B2 and B3. The provision of organic fertilizer P2 composition was significantly better to plant height, while the organic fertilizer composition of P7 showed an increase in leaf number and stem diameter better than other organic composition

The influence of compost humic acid quality and its ability to alleviate soil salinity stress

Purpose Soil salinization is one of the most severe abiotic stresses which threaten sustainable agriculture in arid and semi-arid regions including Morocco. The application of organic amendments like composts to saline soils has been confirmed to alleviate soil salinity stress. The present work aims to study the effect of humic acids (HA), as one of the products resulting from organic matter decomposition, on soil salinity reduction. Methods In this perspective, four composts made from mixtures corresponding to initial C/N ratios of 25, 30, 35 and 40 were tested. The four composts were made from mixtures of different proportions of greenhouse wastes, olive mill waste and sheep manure in Souss-Massa region. Representative samples underwent physicochemical analysis, extraction, purification and analysis of HA. The maturity of compost was assessed through some maturation index, prior to the main trial of the interaction between extracted HA and sodium carbonates salt (Na2CO3), largely encountered in saline soils. Results The results showed that the compost with initial C/N ratio of 35 is the most recommended for application as an amendment to alleviate soil salinity. Conclusion The salt stress alleviating effect of compost may be advocated to compost humic acids and their ability to chelate sodium on their carboxylic sites.

Co-composting of seaweed with lignocellulosic substratum: effect of the compost composition on compost humic substances

Seaweed is one of Latvia's underexploited natural resources. Green and brown algae collected after stranding on beaches were co-composted with lignocellulosic substratum - grass and/or hardwood sawdust. Six different compost compositions were prepared. Composting was carried out indoors in the autumn-winter season. The correspondence of the obtained composts to the national and EU legislation was evaluated. The best results were obtained for compost prepared from green algae, grass and sawdust mixture. Compost raw material, compost and compost humic acids were characterised by elemental analysis, UV and Fourier transform infrared spectroscopy and monosaccharides analyses. The compost humic substance composition was found to be dependent on the compost raw materials. Compost humic acids constituted of recognisable algae and plants biomolecules structures, including lignin-derived structures and carbohydrates. Humic acids of the obtained compost contained around 8% monosaccharides. Fucose is a deoxy sugar typical for algae and not for higher plants, and can be used as a chemical indicator of algae biomass in compost.

Co-composting of seaweed with lignocellulosic substratum: effect of the compost composition on compost humic substances

Seaweed is one of Latvia's underexploited natural resources. Green and brown algae collected after stranding on beaches were co-composted with lignocellulosic substratum - grass and/or hardwood sawdust. Six different compost compositions were prepared. Composting was carried out indoors in the autumn-winter season. The correspondence of the obtained composts to the national and EU legislation was evaluated. The best results were obtained for compost prepared from green algae, grass and sawdust mixture. Compost raw material, compost and compost humic acids were characterised by elemental analysis, UV and Fourier transform infrared spectroscopy and monosaccharides analyses. The compost humic substance composition was found to be dependent on the compost raw materials. Compost humic acids constituted of recognisable algae and plants biomolecules structures, including lignin-derived structures and carbohydrates. Humic acids of the obtained compost contained around 8% monosaccharides. Fucose is a deoxy sugar typical for algae and not for higher plants, and can be used as a chemical indicator of algae biomass in compost.

Fungistatic Activity of Multiorigin Humic Acids in Relation to Their Chemical Structure.

Humic acid (HA) has an inhibitory effect on phytopathogenic fungi, but the structure-activity relationship remains unclear. HAs were extracted from 14 different materials, and their fungistatic activities and elemental C, N, S, and O contents were measured. Cross-polarization magic-angle spinning 13C nuclear magnetic resonance (CPMAS 13C NMR) was used to measure the organic carbon composition. The results showed that all HAs suppressed phytopathogenic fungi growth, with Yunnan lignite HAs showing the highest inhibition (85.3%) against Physalospora piricola. The soil and compost HA aromaticity (ARO) was <50%, except for black soil HAs, while the ARO of all coal HAs was >60%. The ARO of meadow and moss peat HAs was <50%, while the ARO of woody peat HAs was 50.61%. Mantel test and redundancy analysis (RDA) were applied to evaluate the structure-activity relationship. The Mantel test revealed that the N, S, O, N/O, carbonyl C, aromatic C-O, and anomeric C contents were significantly correlated with fungistatic activity. The RDA analysis showed that the S content was positively correlated with fungistatic activity, while the O content was negatively correlated. The carbonyl C content had a positive correlation with fungistatic activity, while the anomeric C and aromatic C-O content had a negative correlation. A high S content and an active composition (carbonyl C) in HAs would lead to a high degree of fungistatic activity. Phytotoxicity test indicated all HAs were beneficial to plant growth. This work identified the basic properties of HAs from various raw materials that control their fungistatic activities.

Adsorptive removal of ascertained and suspected endocrine disruptors from aqueous solution using plant-derived materials

The present study deals with the use of low-cost plant-derived materials, namely a biochar, spent coffee grounds, spent tea leaves, and a compost humic acid, for the adsorptive removal from water of two estrogens, 4-tert-octylphenol (OP) and 17-β-estradiol (E2), and two pesticides, carbaryl and fenuron, each spiked at a concentration of 1mgL-1. Kinetics and adsorption isotherms have been performed using a batch equilibrium method to measure the sorption capacities of the adsorbents towards the four molecules. Adsorption constants were calculated using the linear, Freundlich, and Langmuir models. Kinetics data obtained evidenced a rapid adsorption of each compound onto both biochar and coffee grounds with the attainment of a steady-state equilibrium in less than 4h. Significant differences among the adsorbents and the compounds were found regarding the model and the extent of adsorption. In general, the estrogens were adsorbed more quickly and in greater amounts than the less hydrophobic pesticides, following the order: OP>E2>carbaryl>fenuron. The ranges of Freundlich constants obtained for OP, E2, carbaryl, and fenuron onto the sorbents were 5049-2253, 3385-206, 2491-79, and 822-24Lkg-1, respectively. The maximum values of constants were obtained for biochar, except for OP that was more adsorbed by spent coffee grounds. Adsorption kinetic data followed a pseudo-second-order model, thus indicating the occurrence of chemical interactions between the compounds and the substrates. The remarkable sorption capacities of all adsorbents towards the four molecules suggest the valuable exploitation of these materials for decontamination purposes, such as the treatment of wastewater before a feasible recycle in soil.

GROWTH AND DRY MATTER YIELD OF MAIZE (ZEA MAYS L.) AND RYEGRASS (LOLIUM PERENNE L.) PLANTS AS AFFECTED BY THE APPLICATION OF LIQUID AND SOLID ORGANIC AMENDMENTS IN A CU CONTAMINATED SOIL

The main objective of this study was to evaluate the effect of the application of two solid and one liquid organic amendments (OA), i.e., turkey manure, vineyard compost, and compost-derived humic acids (HA), on the growth and dry matter (DM) yield of maize and ryegrass plants grown in pots (5 L and 2 L) using a contaminated soil. Maize and ryegrass plants were consecutively cultivated during the experimental period (140 days) using a complete random design. Amendments were applied 10 days before the first crop (maize), at three different application rates, and both plant species were chemically fertilized (NPK). Control treatments with and without chemical fertilization were also included. Aerial dry matter (DM) yield of maize was enhance by manure and compost addition in comparison to the fertilized control, while HA had a negative impact on the DM production due to increased soil electrical conductivity (EC). In average, compost and manure applications increased maize DM about 1.2 and 2.7 fold over the control, respectively. DM yield of ryegrass was proportionally increased by the C rate for the three amendments, with few significant differences (p<0.05) among them at the higher application rates. In average, compost, manure and HA applications increased ryegrass DM about 1.5, 1.9, and 1.4 fold over the control. Significant modifications (p<0.001) of the soil available Cu were noted. Correlation analyses indicated that the lower DM production of plants was related to a higher damage of root membranes (malon-dialdehyde [MDA] test) induced by the higher levels of DTPA-Cu. The observed differences in DM would be also explained by the input of different nutrients (like N-NH4) contained in the OA, especially in the manure. Using a stepwise procedure, a regression model was generated for predicting the total maize + ryegrass DM production as a function of soil properties. This model incorporated as predictive variables: TPA-Cu and FA-C.

Bioavailability of lead using chemical extractants in soil treated with humic acids and activated carbon

Palavras-chave: Poluicao do solo. Metais pesados. CaCl 2 . Mehlich 1. DTPA. ABSTRACT - Soil contamination by lead in the town of Santo Amaro, in the state of Bahia, Brazil, originated with the installation of a metal plant in the city in the 1960s, and poses a serious risk to the local population. Determination of the available Pb levels in the soil is an important tool in monitoring the risks of this contamination. However, different methods are used to determine the available Pb content of the soil, resulting in differing values for the extractants. The aim of the present work was to compare the efficiency of extraction using Mehlich 1, DTPA and CaCl 2 solutions in the evaluation of Pb availability in soil treated with different soil amendments. The soil sample used in the experiment was collected near the metal plant. The dosages of soil amendments were set up based on the carbon content of the materials (compost humic acid, commercial humic acid and charcoal), being: 0, 0.75, 1.5, 3 and 7.5 g C kg -1 . The available Pb content was extracted by Mehlich 1, DTPA pH 7.3 and CaCl 2 10 mmol L -1 . Soil fractionation was carried out to determine the metal attached to the exchangeable and organic matter fractions of the soil. The addition of AHv reduced the Pb content of the soil by 60, 89 and 47% for extractions carried out with Mehlich 1, CaCl 2 and DTPA respectively. The Pb content of the organic matter fraction was directly proportional to the dosages of soil amendments. The three extractants under evaluation were efficient in predicting the available Pb content.

Analysis on the impact of composting with different proportions of corn stalks and pig manure on humic acid fractions and IR spectral feature

Using pig manure and corn straw as raw materials for high-temperature composting, setting three different treat- ments: C/N 15, C/N 25, and C/N 35. Composting period is 120 days, which contains 30 days for ventilation cycle by forced continuous ventilation. Sampled on 0, 22, 30, 60, 90, 120th days, they were analyzed by elemental analysis and IR spectroscopy to study effect of different lignin content on compost humic acid (HA) composition and molecular structure. The results showed that the change in composting humic acid C focused on the first 30 days, while after composting, the O/C of compost HA increased, H/C decreased, and N content increased. Low C/N (15) and higher C/N ratio (35) had higher degree of oxidation than the C/N 25 in compost HA. FTIR indicated that the infrared spectrum shapes with different lignin content treatment are similar during the composting process, but the peak intensity is obviously different. Research results proved that the composting stage is more conducive to enhanced aromatic in compost HA. After composting, C/N 15 had less polysaccharide and fat ingredients and more aromatic structural components in compost HA, compared with C/N 25 and 35. In addition, compost HA of C/N 15 had higher degree of humification and its structure was more stable.

Effects of rhamnolipid on the adsorption of Pb2+ onto compost humic acid

Biosurfactants can be applied to improve the micro-environment and efficiency of composting, but their biosurfactant effects on the adsorption of heavy metals and humic acid (HA) remain undefined. This study aims to deal with the effects of biosurfactant rhamnolipid (RL) on the adsorption of Pb2+ onto compost HA at various concentrations, temperatures, and pH values. Adding RL solution influenced the adsorption of Pb2+ onto compost HA without fitting the Langmuir or the Freundlich isotherm. Moreover, Pb2+ adsorption onto compost HA was accelerated by RL at low concentrations until maximum at 40 mg L−1. However, the adsorption was weakened at sufficiently high RL concentration. Furthermore, Pb2+ adsorption was enhanced with increasing pH values and was weakened with rising temperature. This study provides reference for applying biosurfactants in compost.

Soil and compost humic fractions regulate the response of Sclerotinia sclerotiorum to exogenously added allelochemical compounds

Allelochemical compounds released by plants to signal their presence and needs interact in soils with very important macromolecules, such as humic acids (HAs), which are able to modulate the ultimate effects on target organisms. Most of the available studies on plants and microorganisms report the effects of allelochemicals or those of humic fractions, separately. In this study, we investigated the combined activity of these two types of compounds on the soil-resident fungus Sclerotinia sclerotiorum. Thus, ferulic acid (FA), caffeic acid (CA), benzoic acid (BA), salicylic acid (SA), gallic acid (GA) and phthalic acid (PA), exogenously applied to the fungal growth medium, were tested both alone and in combination with a soil HA (SHA) and a compost HA (CHA). The two HAs were also tested alone on the fungus. When the allelochemicals were applied alone, only FA, BA and SA evidenced a significant inhibition of mycelial growth, whereas FA, BA and CA increased the number of sclerotia formed. The two HAs alone reduced the early growth of the fungus and markedly stimulated sclerotia formation. A significant attenuation or, in some cases, suppression of the allelochemical effect on mycelial growth was caused by the coexistence in the medium of the allelochemical and each HA, especially CHA. Moreover, in general, the combinations of HA-allelochemical significantly stimulated sclerotia formation, with respect to the sole allelochemical, but decreased it with respect to HA alone. Thus, investigations on the response of fungi to plant-released allelochemicals should not exclude interactive aspects of these compounds with ubiquitous coexisting humic macromolecules.

Separation and characterization of the constituents of compost and soil humic acids by two-dimensional electrophoresis

To investigate the chemical heterogeneity of humic acids (HAs), we applied two-dimensional (2-D) electrophoresis to HAs from a compost and two types of soils. In this method, HAs are first separated by isoelectric focusing (IEF) and then separated by polyacrylamide gel electrophoresis (PAGE). IEF and PAGE were carried out in the presence of 7 M urea. Upon 2-D electrophoresis of HAs, dark-colored substances were spread out across the gel mainly in the isoelectric point (pI) range of 3.0–4.5. Green fluorescence was observed in the smaller molecular size region of the gel, especially in the pI range of 3.0–4.5, and the most intense fluorescence was found at the moving front. The gels were divided into 36 sections, and then HA constituents were extracted from the individual sections and recovered by precipitation with acid. The distribution of organic carbon (C) among the gel sections coincided with that of the dark-colored substances on the gel. The total C recoveries were only 43–50%, suggesting that a considerable amount of HA constituents was lost during the extraction from the gels and purification. High-performance size-exclusion chromatography confirmed that the constituents of HAs were separated based on their molecular sizes by PAGE. The measurement of diffuse reflectance infrared Fourier transform (DRIFT) spectra indicated that the chemical properties of the HA constituents differed depending on the position on the gels and were affected by the molecular size rather than the pI. The fractions of the compost HA were characterized by higher proportions of aliphatic, proteinous and polysaccharide moieties and by the presence of lignin-derived structures. For the soil HAs, the fractions were characterized by a high proportion of the carboxyl group and a low proportion of aliphatic moieties. The proportion of proteinous and polysaccharide moieties in the fractions of soil HAs decreased with decreasing molecular size. The chemical properties of the green fluorescent substances remained unclear, since there was not enough of the substances to measure the DRIFT spectra. The present study showed that 2-D electrophoresis in the presence of concentrated urea offers an effective method for fractionating and isolating the constituents of HAs.

Comparative evaluation of compost humic acids and their effects on the germination of switchgrass (Panicum vigatum L.)

Purpose This study aimed to investigate comparatively the main chemical and physico-chemical properties of the humic acid (HA) fraction of three different composts and to evaluate the bioactive effects of these HAs on the germination and early growth of four populations of switchgrass.

Characterisation of humic substances formed during co-composting of grass and wood wastes with animal grease

Meat processing grease wastes were composted with lignocellulosic material. Judging by the reduction in the yield of compost lipophilic extract, grease was degraded during the first 20 days of composting. Compost humic acids (HA) and fulvic acids (FA) were characterized by elemental analysis, Fourier transform infrared (FT-IR) spectroscopy and analytical pyrolysis. The compost HA and FA fractions contained a ligno-protein complex. The presence of grease (6.7% dry weight) during composting had a slight influence on the chemical composition of HA and FA. Analytical pyrolysis indicated that, during composting, major changes were observed in the FA fraction, namely, the proportion of nitrogen-bearing compounds increased and carbohydrate-derived products decreased drastically in the final compost. In addition, the shortening of the aliphatic chains of lignin-derived compounds was observed with an increase in the C6C(0−2)/C6C3 ratio in pyrolysates.

Biodecontamination of water from bisphenol A using ligninolytic fungi and the modulation role of humic acids

Bisphenol A (BPA) is an endocrine disruptor compound (EDC) of xenobiotic origin occurring in natural waters and wastewaters, especially in the most industrialized and urbanized areas. Recent investigations report the use of ligninolytic fungi for the removal of aromatic contaminants, including some EDCs, from different matrices. Humic acids (HA) are widely spread in all natural systems and their presence is ascertained to interfere with microbial growth and activity. The objective of this study was to assess the capacity of three ligninolytic fungi, Trametes versicolor, Stereum hirsutum and Pleurotus ostreatus, to remove BPA at the concentration of 4.6mgL−1 from water. Fungal growth on potato dextrose agar (PDA), in the absence and in the presence of a leonardite HA or a green compost HA, was evaluated during the biodecontamination process. The methodological approach adopted in this study excluded the presence of the mycelium in the contaminated water. Results obtained evidenced a relevant removal of BPA by any fungus when PDA only was used as growing medium. The addition of leonardite HA and compost HA stimulated the mycelial growth of any fungus, especially T. versicolor, and significantly enhanced the removal of the contaminant from water by, respectively, T. versicolor only and T. versicolor and S. hirsutum.

Enhanced humification by carbonated basic oxygen furnace steel slag – I. Characterization of humic-like acids produced from humic precursors

Carbonated basic oxygen furnace steel slag (hereinafter referred to as “steel slag”) is generated during iron and steel manufacturing and is often classified as waste. The effect of steel slag on humification process was investigated. Catechol, glycine and glucose were used as model humic precursors from degraded biowastes. To verify that humification occurred in the system, humic-like acids (HLAs) were isolated and characterized structurally by elemental analysis, FTIR spectra, solid-state CP-MAS 13C NMR spectra, and TMAH-Py-GC/MS. Characteristics of the steel slag-HLA were compared with those of HLAs formed in the presence of zeolite and birnessite, and with that of mature compost humic acid. The results showed that steel slag-HLA, like zeolite- and birnessite-HLA, is complex organic material containing prominent aromatic structures. Steel slag substantially accelerated the humification process, which would be highly significant for accelerating the stabilization of biowastes during composting (e.g. municipal solid waste, sewage sludge, and food waste).