Degradation mechanism of lignocellulose in dairy cattle manure with the addition of calcium oxide and superphosphate

Synthesis, characterization and thermoluminescence of MgO:Li,Tb,Sm phosphor for high dose gamma dosimetry applications

A detailed TL investigation on MgO:Li,Tb,Sm phosphor has been carried out by studying several TL characteristics - TL glow curve structure, dose response, linearity dose behaviour, fading and reproducibility. TL glow curve structure of the phosphor reveals the presence of two TL glow peaks. The main TL glow peak of high intensity is observed at high temperature side i.e. at 162 °C and another peak of low intensity is observed at 316 °C. Further, the effect of dose on TL response of the phosphor has been studied and a new behaviour is noticed. With increasing doses, the position of main TL glow peak is similar while the second TL glow peak vanishes at higher doses. A linear TL response is observed from 10 Gy-700 Gy and becomes sublinear above 700 Gy. Low TL fading characteristics and good reproducibility have also been observed. Encouraging results suggest the applicability of doped MgO phosphor for the detection of gamma rays.

Effects of adding steel slag on humification and characteristics of bacterial community during phosphate-amended composting of municipal sludge

This study aimed to investigate the effects of different proportions (0%, 5%, 7.5%, and 10%) of steel slag (SS) on humification and bacterial community characteristics during phosphate-amended composting of municipal sludge. Compared with adding KH2PO4 alone, co-adding SS significantly promoted the temperature, pH, nitrification, and critical enzyme activities (polyphenol oxidase, cellulase, laccase); especially organic matter (OM) degradation rate (25.5%) and humification degree (1.8) were highest in the 5%-SS treatment. Excitation-emission matrix-parallel factor confirmed that co-adding SS could promote the conversion of protein-like substances or microbial by-products into humic-like substances. Furthermore, adding 5%-SS significantly improved the relative abundances of Actinobacteria, Firmicutes and the genes related to carbohydrate and amino acid metabolism, and enhanced the interactions of bacterial community in stability and complexity. The partial least squares path model indicated that OM was the primary factor affecting humification. These results provided a promising strategy to optimize composting of municipal sludge via SS.

Improving the humification by additives during composting: A review

Humic substances (HSs) are key indicators of compost maturity and are important for the composting process. The application of additives is generally considered to be an efficient and easy-to-master strategy to promote the humification of composting and quickly caught the interest of researchers. This review summarizes the recent literature on humification promotion by additives in the composting process. Firstly, the organic, inorganic, biological, and compound additives are introduced emphatically, and the effects and mechanisms of various additives on composting humification are systematically discussed. Inorganic, organic, biological, and compound additives can promote 5.58-82.19%, 30.61-50.92%, 2.3-40%, and 28.09-104.51% of humification during composting, respectively. Subsequently, the advantages and disadvantages of various additives in promoting composting humification are discussed and indicated that compound additives are the most promising method in promoting composting humification. Finally, future research on humification promotion is also proposed such as long-term stability, environmental impact, and economic feasibility of additive in the large-scale application of composting. It is aiming to provide a reference for future research and the application of additives in composting.

Research on the electrochemistry synergied cellulase enzymes strengthens the anaerobic fermentation of cow dung

Lignocellulose degradation (LCD) was the key factor limiting the development of anaerobic fermentation (AF) by the cow dung (CD). In the research, the effects of cellulase pretreatment (CP) and microvoltage (MV) alone and combination on the gas production and LCD during the AF were investigated. The results showed that both CP and MV had an significant effect on the AF, though the synergistic reaction was more pronounced. The total biogas yield (TBY) could reach 11521 mL, and the highest methane production rate was 73% in the synergistic reactions, which was increased by 18.7% and 10.0% compared to CP and MV alone respectively. Meanwhile, the degradation rates of cellulose and lignin could be increased by 33.44% and 22.23%, respectively. The results of SEM, FT-IR and excitation emission matrix demonstrated that CP and MV played an important role in improving the fermentation efficiency. The microbial biomass change results indicated that the synergistic effect of CP and 0.8 V MV on the LCD was achieved by promoting the growth of lignocellulose-degrading bacteria. Moreover, the electricity could not only accelerate the movement of microorganisms and enzymes, but also promoted and enhanced the activity of enzymes, which provided an important reference for further development of the AF technology and the biogas industry.

Impact of biochar, calcium magnesium phosphate fertilizer and spent mushroom substrate on humification and heavy metal passivation during composting

The effects of exogenous additives (biochar, calcium magnesium phosphate fertilizer, and spent mushroom substrate) on humification process and heavy metal passivation during pig manure composting were investigated. The aerobic composting trial were carried out in 60 L reactors for 49 d. The calcium magnesium phosphate fertilizer, biochar, and spent mushroom substrate amendment treatments all accelerated the organic matter degradation and increased the temperature, decreased the volatile fatty acid content by 45%-49.0% and promoted humification of the compost (increasing the humic acid content and humus index). The biochar passivated Cu best, calcium magnesium phosphate fertilizer passivated Zn best (passivation rate 13.85%), and spent mushroom substrate passivated Cd, Cr, and Pb best (passivation rates 25.47%-47.91%). The additives amendment improved Cu, Zn, Cd, Cr, and Pb passivation performance by promoting composting humification process.

Quicklime and Superphosphate Alleviating Apple Replant Disease by Improving Acidified Soil

A two-year field experiment was carried out in order to study the effect of different soil modifiers on alleviating apple replant disease (ARD) in the apple orchards. Four treatments were as follows: replanted apple orchard soil (CK), replanted apple orchard soil treated with quicklime 1.0 g·kg^-1 (T1), replanted apple orchard soil treated with 1.0 g·kg^-1 quicklime and 1.0 g·kg^-1 superphosphate (T2), and replanted apple orchard soil treated with 1.0 g·kg^-1 plant ash (T3). Soil pH, plant biomass, soil bacteria, soil fungi, Fusarium oxysporum, soil enzymes, plant chlorophyll, and photosynthetic parameters were measured to detect the improvement effects of different soil amendments on acidified soil and to alleviate the ARD. The three treatments stably raised the pH of acidified soil and improved the conditions of the plant rhizosphere environment. Compared with the control, T1, T2, and T3 treatments significantly increased growth and plant biomass indexes, such as plant height and ground diameter, as well as photosynthetic parameters. Among the three treatments, T2 had the strongest effects. In July 2018 and July 2019, the number of bacteria was 151.3 and 190.5% higher in T2-treated soil than in control soil, and the number of soil fungi was 53.6 and 53.3% lower. In 2018 and 2019, the copy number of Fusarium solani was 63.6 and 58.6% lower and that of F. oxysporum was 51.8 and 55.7% lower. The T1, T2, and T3 treatments significantly increased soil enzyme activity and leaf chlorophyll content, and their effects were generally ranked T2 > T1 > T3. In conclusion, a combination of 1.0 g·kg^-1 quicklime and 1.0 g·kg^-1 superphosphate added to acidified replant soil increased the soil pH, improved the soil environment, increased the number of bacteria, reduced the number of fungi, increased soil enzyme activity, and improved plant photosynthetic capacity, thereby promoting the growth of replanted seedlings and effectively reducing ARD.

Enhancing rice straw compost with an amino acid-derived ionic liquid as additive

To improve the quality of lignocellulose compost, the effect of a potential new-generation additive-amino acid-derived ionic liquid-on a compost pile comprising 50% rice straw was studied preliminarily. The addition of 1% 1-carboxymethanaminium chloride (glycine hydrochloride [Gly][Cl]) caused observably positive changes in the physical, chemical, and microbiological properties of the compost. After 30 days of composting, the humus and total nitrogen concentrations were 130.85 and 28.8 g/kg, showing an increase of 93.28% and 67.44%, respectively, compared with the concentrations in the beginning of composting; these concentrations were 76.97% and 41.69%, respectively, for the control group (without [Gly][Cl]). Thus, amino acid-derived ionic liquids can be promising additives for enhancing the quality of composts for which straw is used as the primary component.

Regulating bacterial dynamics by lime addition to enhance kitchen waste composting

This study examined bacterial dynamics in response to lime addition to enhance kitchen waste composting using modular network analysis. Bacterial communities could be separated into three meta-modules corresponding to the mesophilic, thermophilic, and mature stage of composting. Lime addition at 1% (wet weight) suppressed acidogens and denitrifiers (e.g. Lactobacillus and Acinetobacter) at the mesophilic stage to reduce greenhouse gas emissions. The matrix pH and temperature were also increased by lime addition via hydrogen reaction to favor bacterial growth and activity. Thus, thermophilic bacteria (e.g. Thermoactinomycetaceae and Planifilum) were enriched with lime addition to facilitate lignocellulose biodegradation for humus formation at the thermophilic stage. Further lime addition to 1.5% reduced ammonia emission at the thermophilic stage via chemical fixation. Moreover, lime inhibited denitrifiers but proliferated nitrifiers at the mature stage to decrease nitrous oxide emission and enhance nitrate content, respectively. As such, lime addition improved both biotic and abiotic composting performance.

Hydrogen peroxide plus ascorbic acid enhanced organic matter deconstructions and composting performances via changing microbial communities

This work aims to investigate the influence of hydrogen peroxide (H₂O₂) and ascorbic acid (ASCA) on the physicochemical characteristics, organic matter (OM) deconstructions, humification degree and succession of bacterial communities for co-composting of bagasse pith and dairy manure. The results indicated that H₂O₂ and ASCA accelerated the degradation of lignocellulose, improved the transformation of dissolved organic matter (DOM), and enhanced the content of humic substance (HS) and the degree of its aromatization. The bacterial communities were significantly changed in the presence of additives, in which the relative abundances of Firmicutes and Actinobacteria significantly increased. Redundancy analysis (RDA) indicated that the degradation of OM and lignocellulose more influenced the bacterial community compositions. Conclusively, adding H₂O₂ and ASCA accelerated lignocellulose degradation efficiency, and improved the composting process, which provided an optimized method to dispose of lignocellulose wastes and livestock manure.

Carbon and Nitrogen Dynamics, and CO2 Efflux in the Calcareous Sandy Loam Soil Treated with Chemically Modified Organic Amendments

In Saudi Arabia, more than 335,000 tons of cow manure is produced every year from dairy farming. However, the produced cow manure is usually added to the agricultural soils as raw or composted manure; significant nitrogen losses occur during the storage, handling, and application of the raw manure. The recovery of ammonia from cow manure through thermochemical treatments is a promising technique to obtain concentrated nitrogen fertilizer and reducing nitrogen losses from raw manure. However, the byproduct effluents from the recovery process are characterized by different chemical properties from the original raw manure; thus, its impact as soil amendments on the soil carbon and nitrogen dynamics is unknown. Therefore, a 90-day incubation experiment was conducted to study the impact of these effluents on CO₂ efflux, organic C, microbial biomass C, available NH₄⁺, and NO₃⁻ when added to agricultural soil. In addition to the two types of effluents (produced at pH 9 and pH 12), raw cow manure (CM), composted cow manure (CMC), cow manure biochar (CMB), and control were used for comparison. The application of CM resulted in a considerable increase in soil available nitrogen and CO₂ efflux, compared to other treatments. Cow manure biochar showed the lowest CO₂ efflux. Cumulative CO₂ effluxes of cow manure effluents were lower than CM; this is possibly due to the relatively high C:N ratio of manure effluent. The content of P, Fe, Cu, Zn, and Mn decreased as incubation time increased. Soil microbial biomass C for soil treated with cow manure effluents (pH 12 and 7) was significantly higher than the rest of the soil amendments and control.

The degradation of organic matter coupled with the functional characteristics of microbial community during composting with different surfactants

The purpose of this study was to investigate the effects of anionic and cationic surfactants on the physico-chemical properties, organic matter (OM) degradation, bacterial community structure and metabolic function during composting of dairy manure and sugarcane bagasse. The results showed that the surfactant could optimize the composting conditions to promote the degradation of OM. The most OM degradation and humic substances (HS) synthesis were observed in SAS. Firmicutes and Proteobacteria were more abundant in SAS and CTAC, and Actinobacteria in CK. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) showed that SAS and CTAC are more abundant than CK in genes related to metabolism, environmental and genetic information processing. The correlation analysis showed that the dominant bacteria had more significant correlation with environmental factors. In general, the anionic surfactant could better promote the degradation of OM, change the structure of microbial community, and improve the quality of compost.

The removal of moisture and antibiotic resistance genes in dairy manure by microwave treatment

To characterize the drying of dairy manure during microwave (MW) heating, and to determine the impacts of microwave radiation on reductions of antibiotic resistance genes (ARGs), this study investigated on understanding the effects of microwave heating on solid streams of flushed dairy manure. A series of experiments were performed to determine the rate of drying, moisture removal percentages, change in solids, and the level of ARGs. Manure was exposed to microwave radiation for 30-300 s at a frequency of 2450 MHz. The results showed moisture removal rate (U) up to 0.63-g water per minute per gram of dairy manure. During MW treatment, volatile solid (VS) content was relatively stable. The MW treatment resulted in reduction of ARGs such as sulII, intI1, and tnpA. The ARG concentrations (sulII, intI1, and tnpA) were reduced by 2 orders of magnitude in less than 1 min of microwave heating. The preliminary results of this study showed that MW treatment can be a viable option for drying of dairy manure and reducing ARGs in manure.

Thermal pretreatment enhances the degradation and humification of lignocellulose by stimulating thermophilic bacteria during dairy manure composting

This study investigated the effect of thermal pretreatment (TP) on the lignocellulose degradation and humification during dairy manure composting and the underlying microbial mechanism. The results showed that TP accelerated temperature rise and elevated composting temperature by increasing 26% initial content of simple organics. The degradation of cellulose, hemicellulose and lignin was 78, 10 and 109% higher in thermal pretreatment composting (TPC) than traditional composting (TC), respectively. Moreover, TP significantly improved the humification degree of composts, as indicated by 14 and 38% higher humus content and humification indexes in TPC, respectively. 16S rRNA sequencing showed that TP increased the relative abundance of thermophilic bacteria in TPC, of which Thermobifida, Planifilum, Truepera and Thermomonospora were potentially involved in lignocellulose biodegradation and humification. Canonical correspondence analysis revealed that TP changed the main factor determining the bacterial community evolution from dissolved organic carbon (DOC) in TC to temperature in TPC.