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•Chicken manure biochar and combined with microorganism culture was studied for chicken manure composting.•CMB and CMMC addition promoted the organic matter degradation and reduced ...the period of maturity.•Chicken manure biochar addition reduced the greenhouse gases and ammonia emission.•Chicken manure biochar improved the quality of end product.
The effects of chicken manure biochar (CMB) and chicken manure integrated microbial consortium (CMMC) as co-amendments were assessed on compost maturity and reduction of greenhouse gases and ammonia (NH3) emissions during chicken manure composting. Composting was conducted using six combinations of CMB and CMCC (0 % CMB + 0 % CMMC, 0 % CMB + 10 % CMMC, 2 % CMB + 10 % CMMC, 4 % CMB + 10 % CMMC, 6 % CMB + 10 % CMMC, 10 % CMB + 10 % CMMC added on a dry weight basis) in six polyvinyl chloride composting reactors for 42 days under an aerobic environment. Co-amendment of CMB and CMMC extended the thermophilic stage and promoted compost maturity. The release of greenhouse gases nitrous oxide (N2O) and methane (CH4) and NH3 from treatments co-amended by CMB and CMMC were reduced by 19.0–27.4 %, 9.3–55.9 % and 24.2–56.9 %, respectively, compared with the control. In addition, a redundancy analysis showed that the C/N ratio and temperature had a significant relationship with greenhouse gases and NH3 emissions among all physiochemical characteristics.
The process of harmless treatment of livestock manure produces a large amount of odor, which poses a potential threat to human and livestock health. A vertical fermentation tank system is commonly ...used for the environmentally sound treatment of chicken manure in China, but the composition and concentration of the odor produced and the factors affecting odor emissions remain unclear. In this study, we investigated the types and concentrations of odors produced in the mixing room (MR), vertical fermenter (VF), and aging room (AR) of the system, and analyzed the effects of bacterial communities and metabolic genes on odor production. The results revealed that 34, 26 and 26 odors were detected in the VF, MR and AR, respectively. The total odor concentration in the VF was 66613 ± 10097, which was significantly greater than that in the MR (1157 ± 675) and AR (1143 ± 1005) (P < 0.001), suggesting that the VF was the main source of odor in the vertical fermentation tank system. Methyl mercaptan had the greatest contribution to the odor produced by VF, reaching 47.82%, and the concentration was 0.6145 ± 0.2164 mg/m3. The abundance of metabolic genes did not correlate significantly with odor production, but PICRUSt analysis showed that cysteine and methionine metabolism involved in methyl mercaptan production was significantly more enriched in MR and VF than in AR. Bacillus was the most abundant genus in the VF, with a relative abundance significantly greater than that in the MR (P < 0.05). The RDA results revealed that Bacillus was significantly and positively correlated with methyl mercaptan. The use of large-scale aerobic fermentation systems to treat chicken manure needs to focused on the production of methyl mercaptan.
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•The odor concentration and SOAV in the VF were much higher than in the MR and AR.•Methyl mercaptan was the major odor contributor in the VF.•Cysteine and methionine affect methyl mercaptan emissions.•Bacillus were positively correlated with the emission of methyl mercaptan.
Moisture content (MC) influences substance transformation during composting and the function of exogenous microbial agents. Unsuitable MC could cause leaching, nutrient loss, and secondary ...contamination. In this study, chicken manure composting with varied MC (45–61%) was conducted under functional microbial agent inoculation to explore the optimum condition for composting and the potential mechanism. Due to the enhanced decomposing, nitrosation, and nitrification effect lead by the functional microorganism, treatment with the optimal MC (53%) exhibited the highest composting temperature (61 °C) and longest high-temperature period (15 days), achieving a final carbon-nitrogen ratio (C/N), humic acids and fulvic acids ratio (HA/FA), and NH4+-N/NO3−-N at 19.20, 2.00, and 0.93, respectively. After composting, the total nitrogen (TN) increased by 13.01–22.10% in the treatments with microbial agent inoculation compared with original stack, while it decreased by 7.76% in control. The highest nutrient (5.63%, 5.63–14.20% higher than the other composts) and better product safety (11.43–23.58% higher seed germination than others) were observed in treatment with MC at 53%, exceeding the Chinese national standard for organic fertilizer. Obviously, under optimum MC, microbial agent augmentation lead to high quality and safe compost products after a short composting period (25 days) without any leaching, which suggested an efficient way to promote the recycling and recovery of husbandry waste.
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•Initial moisture content at 53% is the best for bio-enhanced manure composting.•The initial moisture content of 53% effectively promoted compost quality.•Microbial agent bio-augmentation effectively promoted compost quality and safety.•The low moisture content effectively prevented leaching and nutrient loss.
Because of rapid development in the livestock industry, the production of chicken manure has subsequently increased, which may contribute to environmental pollution. In this regard, in-vessel ...composting of biochar amended chicken manure and sawdust mixtures was investigated to find out the effect of biochar at the ratios of 0% (control), 3% (T1), 5% (T2), and 10% (T3) on ammonia and greenhouse gases (GHGs) emission, compost quality, pathogenic contaminants and phytotoxicity. The composting process was performed in 100-L, pilot-scale, plastic, cylindrical vessels for 50 days. The addition of biochar (3%, 5%, and 10%) increased the thermophilic temperature with a significant reduction in gaseous emissions (ammonia and CO2), microbial pathogens (Escherichia coli and Salmonella sp.), and phytotoxicity (Lepidium sativum seed germination assay) compared with that of the control compost products. However, according to the obtained results with in-vessel composting, the amendment of 10% biochar showed the most significant effects concerning the quality of the compost nutrients. The study reveals that the addition of biochar during in-vessel chicken manure composting is beneficial in the reduction of gaseous emissions and pathogenic microorganisms apart from improvement in plant nutrients.
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•Biochar-assisted in-vessel composting of chicken manure was investigated.•Biochar (10%) addition showed reduction of ammonia and GHGs emissions and pathogens.•Biochar at 10% level enhanced nutrient retention and overall compost quality.•The germination index of cress seeds was >90% in biochar amended compost.
•Seeds from 17 species performed extremely differently in deionized water and compost.•The GI of hybrid cucumber had a better correlation with Characteristicsof compost.•Hybrid cucumber seeds was ...suitable for evaluation of compost maturity.
The seed germination index (GI) is a widely used indicator of compost maturity and is a required index in many national standards. However, seeds of different species vary markedly in sensitivity to the biological toxicity of compost. Therefore, suitable seed selection is essential for evaluation of compost maturity with the GI. This study systematically investigated the germination percentage and root length for seeds of 17 species incubated in deionized water for 48 h at 25 °C in the dark. Based on the germination percentage, seeds of eight species (white radish, cucumber, fruit radish, edible rape, round radish, hybrid cucumber, cress, and Chinese cabbage) were selected for determination of the GI of chicken manure composted with differing proportions of tobacco powder and mushroom substrate. The GI of hybrid cucumber seeds showed a significant positive correlation with temperature and pH, and a significant negative correlation with E4/E6 ratio and ammonium-nitrogen content. The change in GI of hybrid cucumber seeds during composting and the GI value at the completion of composting were consistent with other maturity indicators. Among the tested seeds, the biological toxicity of the compost was best characterized by hybrid cucumber seeds, which thus represented a sensitive and reliable seed suitable for evaluation of compost maturity with the GI.
•Microorganisms were used to inoculate chicken manure at the initial of composting.•Inoculation with microorganisms prolonged the thermophilic stage in composting.•Improvements were seen in the ...humification levels and composting maturity.
The effects of inoculating with microorganisms on chicken manure compost with maize straw were investigated in a self-built aerated static box (0.6 m3) by assessing the influences of temperature, moisture, pH, C/N ratio, transformation of nitrogen, humification levels and composting maturity. Results showed that inoculation with microorganisms prolonged the thermophilic stage in composting compared to control groups, increasing the temperature, pH and germination index as the composting period progressed. This suggests that inoculation with microorganisms were helpful in facilitating the process of composting, as it significantly reduced NH4+ content during the cooling stage. Additionally, NO3− increased after the first pile turning on day 10, continuing until the end of thermophilic stage. Improvements across transformation of nitrogen, humification levels and composting maturity were also seen in inoculation piles. Conclusively, we suggested inoculating using cocktails of microorganisms to increase efficiency and promote maturity in chicken manure composting.
Antibiotic resistance genes (ARGs), prevalent across multiple environmental media, threaten human health worldwide and are considered emerging environmental contaminants. Earthworm gut, a niche for ...bacteria to survive, represents a potential reservoir for ARGs in soil. However, the compositions of ARGs in the earthworm gut microbiota remain elusive, especially under field conditions. In this study, we applied high-throughput quantitative PCR to profile the ARGs in the gut microbiota of earthworms after chronic exposure to fertilizers. To elucidate the factors that impact the ARGs composition, the bacterial community of gut microbiota, mobile genetic elements (MGEs), soil (nutrients, heavy metals, and antibiotics) and the properties of gut content (pH and nutrients) were analyzed. A total of 98 subtypes among 9 major types of ARGs, and 3 different MGEs were detected in the gut microbiota of earthworms. Organic fertilizer (sewage sludge and chicken manure) application significantly increased the diversity and abundance of ARGs. Of the 1123 identified operational taxonomic units (OTUs) at 97% similarity cutoff, most of them were assigned to Firmicutes (55.5%) and Proteobacteria (33.6%) in earthworm gut microbiota. Long-term organic fertilization slightly changed the microbiota composition, but did not impact the diversity. Partial redundancy analysis (pRDA) revealed that bacterial community, combined with environmental factors (soil and gut content properties) and MGEs, explained 72% of the variations of ARGs in the earthworm gut. Furthermore, the co-occurrence pattern between ARGs and MGEs indicated that horizontal gene transfer via MGEs may occur in the earthworm gut. These findings improve the current understanding of the dynamics of soil fauna-associated ARGs and the gut microbiota of earthworms may be an underappreciated hotspot for ARGs in the environment.
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•Earthworm gut harbors diverse ARGs.•Organic fertilization increases the ARGs burdens in earthworm gut.•Gut microbial community contributes to the variation of ARGs.
Biochar is thought to be good sorbent for heavy metal and exploring ways to increase the efficiency of heavy metal adsorption by biochar is of great importance. Chicken manure biochar was modified ...with sulfur, hydroxyapatite and MnFe2O4 respectively. The properties and composition of the pristine and modified biochar was characterized. The pH and ash content of biochar was significantly increased after modification. Energy dispersive spectroscopy results showed that biochar modified with sulfur, hydroxyapatite and MnFe2O4 was successfully loaded on S, Ca/P and Fe/Mn respectively. The adsorption kinetic of Cd2+ absorption by pristine and modified biochar was better fitted by the pseudo second-order kinetic model, suggesting that the adsorption of Cd2+ on biochar followed the process of chemisorption. The Cd2+ adsorption isotherms of sulfur modified chicken manure biochar (SCMB), hydroxyapatite modified chicken manure biochar (HCMB) and MnFe2O4 modified chicken manure biochar (FMCMB) was better fitted by Freundlich model, while the Cd2+ adsorption by pristine chicken manure biochar (CMB) was well fitted by Langmuir model. The maximum Cd2+ adsorption capacity of SCMB, HCMB, FMCMB and CMB was 188.20, 111.53, 109.94 and 19.65 mg·g−1 respectively. Quantitative analysis of Cd2+ adsorption mechanism by biochar showed that the contribution of ion exchange for Cd2+ adsorption of CMB accounted for 58 %, while SCMB, HCMB and FMCMB decreased to only 12 %, 8 % and 4 % respectively. Meanwhile, the contribution of precipitation, complexion and metal-Cπ coordination for Cd2+ adsorption increased after modification. Pot experiment showed that application of SCMB significantly increased soil pH value, decreased the bioavailable Cd in soil and Cd uptake by brassica chinensis shoots, suggesting that SCMB can be a potential material for the safety use of Cd contaminated agricultural soil.
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•Chicken manure biochar was modified by sulfur, hydroxyapatite and MnFe2O4 respectively.•The maximum Cd2+ adsorption capacity of modified biochar significantly increased.•Sulfur modified biochar decreased the concentration of Cd in shoots of brassica chinensis.
In this study, chicken manure biochar (CBC) was prepared and applied as adsorbent for the removal of phenolic pollutants including phenol (Ph) and 2,4-Dinitrophenol (DNP) from wastewaters. The ...feasibility analysis was focused on the adsorption effects of various factors, such as initial concentration, adsorbent dosage and reaction time. The results showed that BC could efficiently remove the Ph and DNP within 90 min of reaction time. Increasing of CBC dosage up to 0.3 g results in the maximum removal efficiency of Ph and DNP and lowers initial concentration which is beneficial for the adsorption of phenolic compounds. The second-order kinetic model and the Langmuir isotherm provided the best correlation with the adsorption data. Based on the Langmuir isotherm, maximum adsorption capacities (qmax) of Ph and DNP were found at 106.2 and 148.1 mg g−1, respectively. The obtained qmax values for CB were higher than those reported in literature on the adsorption of Ph and DNP using different biochar. Analyzing the regeneration characteristics, BC displayed high reusability with less than 20% loss in adsorption capacities of Ph and DNP, even after five repeated cycles. Investigation of the adsorption equilibrium under various conditions suggested several possible interaction mechanisms, including hydrogen bonding, electrostatic interaction and π- π bonding, which were attributed to the binding affinity of the adsorbent-adsorbate interaction.
In the field application, the CBC showed an excellent removal efficiencies of Ph and DNP from industrial wastewaters (around 80% phenolic pollutants were removed). These findings support the potential use of CBC as effective adsorbent for treatment of wastewater containing Ph and DNP.
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•Chicken manure biochar is an effective adsorbent for the removal of phenolic compounds.•Adsorption capacities of phenol and 2, 4-dinitrophenol were 106.2 and 148.1 mg g−1, respectively.•Removal efficiencies of phenol and 2, 4-dinitrophenol in wastewater were 78.5 and 83.4%, respectively.•Chicken manure biochar showed high reuse ability even after 5 times reused.
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•The OTC could inhibit the transformation of NH4+-N to NO3−-N during composting.•The OTC inhibited the growth of core microbial and led to a delay effect.•The Bacillus and ...Thermobifida could inhibited the transformation of nitrogen.•Nitrogen loss could be reduced by regulating core microbes during composting.
This study investigated oxytetracycline (OTC) effects on nitrogen (N) transformation and bacterial community diversity during chicken manure composting. The addition of OTC inhibited nitrifying bacteria, resulted in a decrease in the transformation of NH4+-N to NO3−-N during composting, and affected in the order T3 (32.76%) > T2 (28.76%) > T1 (17.02%) > CK. The OTC could act as an inhibitor against core microbial growth, leading to a delay effect during composting. 16S rRNA sequencing was employed for the functional prediction, and results indicated the bacterial community related to N transformation reconstructed under OTC stress. The core microorganisms were changed after OTC addition, with the emergence of Bacillus and Thermobifida, which could inhibit the N transformation by network analysis. Therefore, core microorganisms could be regulated to reduce the negative of OTC impacts on N transformation and thus reduce N loss during composting.
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