Humification improvement by optimizing particle size of bulking agent and relevant mechanisms during swine manure composting

Optimizing extraction conditions to enhance the humification and soil remediation potential of compost-derived dissolved organic matter

Compost tea (CT), primarily composed of dissolved organic matter derived from compost, is widely used in various environmental and agricultural applications. Nevertheless, limited information is available regarding how extraction parameters influence the quality of CT and its efficacy in soil remediation. In this study, a multi-factor orthogonal design L16 (43) was employed to investigate the effects of compost-to-water ratio (CWR), extraction time (ET), and aeration pattern (AP) on nutrient extraction and humification of CT, aiming to optimize the extraction conditions. Results showed that N, P2O5, and K2O extraction efficiencies in all treatments ranged from 10 to 25 %, 10-20 %, and 50-85 %, respectively. The comprehensive humification score was in the range of 1.27-1.60. Among the three parameters, ET showed the most significant influence on CT quality. The optimal treatment for nutrient extraction was T15 (CWR 1:60, ET 48 h, and stirring), while T17 (CWR 1:30, ET 48 h, and aeration) exhibited superior performance on humification. Furthermore, the total Cd removal efficiency of T17 was 83.64 % after multiple washing cycles, which was attributed to an increased number of hydroxyl, carboxyl, and carbonyl functional groups that provided additional binding sites for Cd.

Electric field as an activator of inoculated Bacillus clausii enhances humification during electric field-assisted aerobic composting

A novel electric field-assisted aerobic composting (EAC) method effectively facilitates compost disposal by applying a low electric field to conventional aerobic composting (CAC). The humification effect of inoculation with Bacillus clausii in the EAC system was better than that in the CAC system, so this study focused on the enhancement effect of microbial inoculation in the EAC system. Compared with EAC, EAC with microbial inoculation (AMI-EAC) increased the degradation of cellulose, hemicellulose, and lignin. Furthermore, AMI-EAC improved the humification index by 42.89 % relative to EAC. AMI-EAC also increased the relative abundance of Bacillus, enriched thermophilic and electroactive microorganisms, and enhanced the activity of associated degradative enzymes, which promoted the decomposition and humification of organic matter. Partial least squares-path model analysis showed that Bacillus inoculation during AMI-EAC enhanced the direct positive effect of microorganisms on enzyme activity and strengthened the positive impacts of substance degradation and enzyme activity on compost maturation. This study provided new insights for inoculating microbial agents to enhance composting efficiency in future engineering applications of EAC.

Interactions between fungi and bacteria hosts carrying MGEs is dominant for ARGs fate during manure mesophilic composting

The mycelial networks of fungi promote the interaction between the originally isolated bacteria, thereby potentially enhancing the exchange of nutrients and the horizontal transfer of genetic materials. However, the driving effect of fungi on antibiotic resistance genes (ARGs) during mesophilic facultative composting is still unclear. This study aims to elucidate the changes in ARGs and underlying mechanisms during the mesophilic composting of manure. Results indicated that reduction rates of ARGs in sheep and pig manure over a 90-day composting period were 34.68% and 60.10%, respectively. The sul1, sul2 and tetX were identified as recalcitrant ARGs in both composting treatments, with the additional unique recalcitrant gene addA observed in sheep manure. Fungal communities appeared to have a more significant influence on the cooperation between bacteria and fungi. Massive fungi interacted intensively with bacterial hosts carrying both ARGs and mobile genetic elements (MGEs). In sheep and pig manure, there were 53 and 38 potential bacterial hosts (genus level) carrying both ARGs and MGEs, associated close interactions with fungi. Structural equation modeling revealed that compost properties influence ARGs by affecting the abundance of core fungi and the hosts carrying MGEs, and that core fungi could also impact ARGs by influencing the bacterial hosts carrying MGEs. Core fungi have the potential to facilitate the horizontal transfer of ARGs by enhancing bacterial network interactions.

Innovation for recycling of organic matter through composter with automatic and sustainable temperature recording accessed via Bluetooth/mobile app

Compost reactors, commonly used in experiments, industrial assays, and home residue treatment systems, have the potential to facilitate composting. Challenges persist in the realm of small-scale composting, encompassing facets such as temperature monitoring, homogenization of the compost mass, management of moisture with the control of leachate generation, and integration with a renewable energy source. This study assesses a pioneering composter prototype endowed with essential features to ensure a pragmatic and secure composting process. This includes the facilitation of remote access to temperature data via Bluetooth and a mobile application. Across successive trials, the scrutinized composter prototype consistently yielded reproducible outcomes, exhibiting a coefficient of variation below 25% for the majority of appraised parameters. In comparison to a conventional reactor, the decomposing residue mixture within the examined prototype manifested elevated temperatures (p < 0.05). Moreover, the tested prototype demonstrated C/N ratio lower than 20/1 within 45 days, a higher final nitrogen concentration, and enhanced germination of seeds that served as phytotoxicity bioindicators. Notably, the prototype needed 46.6% less space, offering improved leachate control, three times faster turning time, temperature monitoring, and reduced fly attraction.

Elucidating carbon conversion and bacterial succession by amending Fenon-like systems during co-composting of pig manure and branch

The essential point of current study was to investigate the effect of a Fenton-like system established by oxalic acid and Fe(II) on gas emission, organic matter decomposition and humification during composting. Branches were pretreated with Fenton reagents (0.02 M FeCl2·4H2O + 1.5 M H2O2) and then adding 10 % oxalic acid (OA). The treatments were marked as B1 (control), B2 (Fenton reagent), B3 (10% OA) and B4 (Fenton-like reagent). The results collected from 80 d of composting showed that adding Fenton-like reagent benefited the degradation of organic substances, as reflected by the total organic carbon and dissolved organic carbon, and the maximum decomposition rate was observed in B4. In addition, the Fenton-like reagent could improve the synthesis of humus characterized by complex and stable compounds, which was consistent with the spectral parameters (SUVA254, SUVA280, E253/E203 and Fourier transform-infrared indicators) of DOC. Furthermore, the functional microbial succession performance and linear discriminant effect size analyses provided microbial evidence of humification improvement. Notably, compared with the control, the minimum value of CH4 cumulation was reported in B4, which decreased by 30.44 %. Concluded together, the addition of a Fenton-like reagent composed by OA and Fe(II) is a practical way to improve the humification. Furthermore, the mechanisms related to the promotion of humification should be investigated from free radicals, functional genes, and metabolic pathways.

Humification and fungal community succession during pig manure composting: Membrane covering and mature compost addition

The objective of this study was to elucidate the combined effect of a semi-permeable membrane (M) and mature compost (MC) on humification and fungal community succession in pig manure composting. Compared with the control, the concentrations of humic substances (HSs) increased by 44.54 % (M + 15 % MC) and 43.90 % (M). During the thermophilic phase, Aspergillus (67.26 %) was the dominant genus in the M + 15 % MC treatment. Membrane covering increased the relative abundance (RA) of other phyla (except for Ascomycetes and Basidiomycetes) on the 14th day and Basidiomycetes on the 80th day in M treatment. Humic acid, HSs were positively correlated with the RA of genera Myceliophthora, Kernia, and Mycothermus. Myceliophthora was the key genus in the M + 15 % MC treatment on the 80th day. The results showed that 15 % MC addition under membrane covering optimizes the quality of composting products.

The efficient solution to decline the greenhouses emission and enrich the bacterial community during pig manure composting: Regulating the particle size of cornstalk

In present study, four lengths of chopped cornstalks were amended with pig manure respectively for 100 days aerobic fermentation, which aimed to evaluate the impact of different length of agricultural solid wastes on gaseous emission and dominating bacterial community succession and connection. The result revealed that the maximum ammonia volatilization was observed in 5 cm of straw samples attributed to the prominent mineralization, which was opposite to the emission of CH4 and N2O. As for global warming potential, the minimum value was detected in 5 cm of straw samples, which decreased by 5.03-24.75% compared with other samples. Additionally, the strongest correlation and complexity of bacterial community could be detected in 5 cm of straw treatment, representing the most vigorous bacterial metabolic ability could be recorded by optimizing the microbial habitat. Therefore, in order to decline the greenhouse effect in livestock manure composting, the 5 cm of corn straw was recommended.

Exploring gaseous emissions and pivotal enzymatic activity during co-composting of branch and pig manure: The effect of particle size of bulking agents

The purpose of current study was to probe the effect of various length of branch on gaseous emissions and vital enzymatic activity. Four lengths (< 2 cm, 2 cm, 5 cm, and > 5 cm) of clipped branch were mingled with collected pig manure for 100 days aerobic fermentation. The consequence demonstrated that the amendment of 2 cm of branch showed conducive to decline the greenhouse gas emissions, which the CH4 emissions decreased by 1.62-40.10%, and the N2O emissions decreased by 21.91-34.04% contrasted with other treatments. Furthermore, the peak degree of enzymatic activities was also observed in 2 cm of branch treatment by the optimizing living condition for microbes. In view of microbiological indicators, the most abundant and complex bacterial community could be monitor in 2 cm of branch composting pile, which verified the microbial facilitation. Summing up, the strategy of 2 cm branch amendment would be recommended.