Effect of Different Proportions of Three Microbial Agents on Ammonia Mitigation during the Composting of Layer Manure

Ammonia and greenhouse gas emissions from beef feedlot surface material treated with aluminum sulfate (alum) or microbial amendments

A lab-scale study evaluated ammonia (NH3 ) and greenhouse gases, emissions when aluminum sulfate (alum) or a microbial product were added to beef feedlot surface material (FSM). Three kilograms of FSM and 1.5 kg of water were added to stainless steel pans (50 cm × 30 cm × 6.5 cm). Treatments included a control (no amendment), 450 g alum, or 0.5 g microbial product. The pans were placed in an environmental chamber that was maintained at 23°C and 50%-60% humidity. Emissions were measured three times weekly for 3 weeks. Ammonia, N2 O, and CH4 were lower (p < 0.01) from pans with amendments compared to the control pans; emissions from the FSM that received the microbial treatment were lower than the FSM treated with alum. Methane emissions were similar for the control and alum-treated FSM but lower (p < 0.01) for the FSM that was treated with the microbial product. Nitrate-N was lower, and NH4+ -N and total sulfur concentrations were higher in FSM treated with alum compared to no treatment or the microbial treatment (p < 0.01). Results indicate that both alum and microbial amendments have benefits in reducing emissions from the feedlot surface, with the microbial product providing additional reductions in emissions compared to the alum.

Effects of microbial inoculant and additives on pile composting of cow manure

Composting is an effective method of recycling organic solid waste, and it is the key process linking planting with recycling. To explore the reuse of agricultural organic solid waste as a resource in the Yellow River Delta, the effects of microbial inoculant and different additives (calcium superphosphate, biochar, tomato straw, rice husk, and sugar residue) on pile composting of cow dung were studied to obtain the best composting conditions. The results showed that microbial inoculant and additives all played positive roles in the process of aerobic composting, and the experimental groups outperformed the control groups without any additives. For discussion, the microbial inoculant promoted rapid pile body heating more than the recovery materials alone, and the effects on aerobic composting were related to the organic matter of substrates and biochar. After being composted, all the materials were satisfactorily decomposed. Degradation of additives into humic acid might serve as electron shuttles to promote thorough organic matter decomposition. These results provide a scientific basis data for industrial composting of organic solid waste processed by on-site stacking, and provide a reference for researcher and practitioners for studying the applications of microbial inoculant on aerobic composting.

Feedstock-dependent abundance of functional genes related to nitrogen transformation controlled nitrogen loss in composting

The objective of this work was to explore how selection of feedstock affects nitrogen cycle genes during composting, which eventually determines the nitrogen loss. Four composting mixes (CM: chicken manure; SM: sheep manure; MM_1/3: mixed manure with CM: SM = 1:3 w/w, MM_3/1: CM: SM = 3:1 w/w) were investigated. Results showed that adding 25 % and 75 % SM to CM reduced 26.5 % and 57.9 % nitrogen loss, respectively. CM contained more ammonification genes and nrfA gene, while SM had more denitrification genes. Nitrogen fixation genes in CM were slightly higher than that in SM at the initial stage, but they sharply dropped off as the composting entered the high temperature stage. MM_1/3 showed significantly reduced ammonification genes than CM, and increased nitrogen fixation and NH₄⁺ assimilation genes. Therefore, adding SM to CM could change the abundance of genes and enzymes related to nitrogen cycle to reduce nitrogen loss.

Effects of multiple antibiotics residues in broiler manure on composting process

At present, the effect of multiple antibiotics on aerobic composting process and its mechanism are not clear. So in this study, broiler manure containing different doses of Doxycycline (DOX) and Gatifloxacin (GAT) were used as raw materials and mixed with rice hull for aerobic composting, and the effects of the combination of multiple antibiotics on the process parameters of broiler manure composting and the succession of bacterial and fungal community structures were systematically analyzed. Our results showed that at the initial period of composting, the combination of multiple antibiotics led to a delayed temperature and pH increase (T1: 57.0 °C, T2: 48.3 °C, T3: 45.5 °C on Day 3 for temperature and T1: 7.44, T2: 7.1, T3: 6.88 on Day 5 for pH), and a slow total nitrogen decrease (T1: 1.56%, T2: 1.82%, T3: 1.74% on Day 5). Although these effects decreased gradually with the degradation of antibiotics, the relative abundance of Actinobacteriota (T1: 13.29%, T2: 10.57%, T3: 8.99%) and Bacteroidota (T1:27.52%, T2:40.03%, T3:39.81%)) were still influenced by multiple antibiotic residuals until the end of composting period. Higher levels of antibiotics had more lasting effects on the bacterial community (T3 > T2). However, the combination of these two antibiotics did not significantly promote or inhibit the succession of the fungal community structure. The heatmaps showed that composting stage had a greater effect on the microbial community structures than antibiotics. The results provided a theoretical reference for composting broiler manure containing DOX and GAT.

Isolation and Characterization of Effective Bacteria That Reduce Ammonia Emission from Livestock Manure

Ammonia from livestock manure reacts with chemical components discharged from various emission sources to produce airborne particulate matter. This study aimed to investigate a novel effective microbial agent to suppress ammonia gas emitted from manure. Both isolated L12I and 12III strains, identified as Pediococcus acidilactici (PA), were selected for their superior activity in assays performed with the evaluation criteria such as acid production, ammonia decomposition, and urease inhibition, which are key factors influencing ammonia excretion. The survivability of PA strains was confirmed by an increase in DNA abundance in the manure. PA strains lowered the pH of manure and suppressed the growth of hyper-ammonia-producing bacteria (HAB) possessing urease activity. The L12I and 12III treatment groups showed 23.58% and 38.00% emission reductions, respectively. Especially, the 12III strain was proven to be the more effective strain for reducing ammonia gas emission, with the best ability to reduce pH and inhibit HAB. The strains could have an additive effect in improving the manure quality as a nitrogen fertilizer by preserving the total nitrogen and urea content. These results suggest that PA strains can be used as unprecedented microbial agents to improve manure-derived environmental pollution and improve fertilizer quality.

Dissipation Dynamics of Doxycycline and Gatifloxacin and Accumulation of Heavy Metals during Broiler Manure Aerobic Composting

In this study, broilers were fed with heavy-metal-containing diets (Zn, Cu, Pb, Cr, As, Hg) at three rates (T1: 5 kg premix/ton feed, T2: 10 kg premix/ton feed and T3: 15 kg premix/ton feed) and Doxycycline (DOX) and Gatifloxacin (GAT) at low or high doses (T4: 31.2 mg DOX/bird/day and 78 mg GAT/bird/day, T5: 15.6 mg DOX/bird/day and 48 mg GAT/bird/day) to assess the accumulation of various heavy metals and the fate of two antibiotics in broiler manure after 35 days of aerobic composting. The results indicated that the two antibiotics changed quite differently during aerobic composting. About 14.96–15.84% of Doxycycline still remained at the end of composting, while Gatifloxacin was almost completely removed within 10 days of composting. The half-lives of Doxycycline were 13.75 and 15.86 days, while the half-lives of Gatifloxacin were only 1.32 and 1.38 days. Based on the Redundancy analysis (RDA), the concentration of antibiotics was significantly influenced by physico-chemical properties (mainly temperature and pH) throughout the composting process. Throughout the composting process, all heavy metal elements remained concentrated in organic fertilizer. In this study the Cr content reached 160.16 mg/kg, 223.98 mg/kg and 248.02 mg/kg with increasing premix feed rates, similar to Zn, which reached 258.2 mg/kg, 312.21 mg/kg and 333.68 mg/kg. Zn and Cr concentrations well exceeded the United States and the European soil requirements. This experiment showed that antibiotic residues and the accumulation of heavy metals may lead to soil contamination and pose a risk to the soil ecosystem.

Effect of Microbial Inoculation on Carbon Preservation during Goat Manure Aerobic Composting

Carbon is the crucial source of energy during aerobic composting. There are few studies that explore carbon preservation by inoculation with microbial agents during goat manure composting. Hence, this study inoculated three proportions of microbial agents to investigate the preservation of carbon during goat manure composting. The microbial inoculums were composed of Bacillus subtilis, Bacillus licheniformis, Trichoderma viride, Aspergillus niger, and yeast, and the proportions were B1 treatment (1:1:1:1:2), B2 treatment (2:2:1:1:2), and B3 treatment (3:3:1:1:2). The results showed that the contents of total organic carbon were enriched by 12.21%, 4.87%, and 1.90% in B1 treatment, B2 treatment, and B3 treatment, respectively. The total organic carbon contents of B1 treatment, B2 treatment, and B3 treatment were 402.00 ± 2.65, 366.33 ± 1.53, and 378.33 ± 2.08 g/kg, respectively. B1 treatment significantly increased the content of total organic carbon compared with the other two treatments (p < 0.05). Moreover, the ratio of 1:1:1:1:2 significantly reduced the moisture content, pH value, EC value, hemicellulose, and lignin contents (p < 0.05), and significantly increased the GI value and the content of humic acid carbon (p < 0.05). Consequently, the preservation of carbon might be a result not only of the enrichment of the humic acid carbon and the decomposition of hemicellulose and lignin, but also the increased OTU amount and Lactobacillus abundance. This result provided a ratio of microbial agents to preserve the carbon during goat manure aerobic composting.

Comparative genomics and physiological investigation supported safety, cold adaptation, efficient hydrolytic and plant growth-promoting potential of psychrotrophic Glutamicibacter arilaitensis LJH19, isolated from night-soil compost

BACKGROUND

Night-soil compost (NSC) has traditionally been conserving water and a source of organic manure in northwestern Himalaya. Lately, this traditional method is declining due to modernization, its unhygienic conditions, and social apprehensions. Reduction in the age-old traditional practice has led to excessive chemical fertilizers and water shortage in the eco-sensitive region. In the current study, a bacterium has been analyzed for its safety, cold-adaptation, efficient degradation, and plant growth-promoting (PGP) attributes for its possible application as a safe bioinoculant in psychrotrophic bacterial consortia for improved night-soil composting.

RESULTS

Glutamicibacter arilaitensis LJH19, a psychrotrophic bacterium, was isolated from the NSC of Lahaul valley in northwestern Himalaya. The strain exhibited amylase (186.76 ± 19.28 U/mg), cellulase (21.85 ± 0.7 U/mg), and xylanase (11.31 ± 0.51 U/mg) activities at 10 °C. Possessing efficient hydrolytic activities at low-temperature garners the capability of efficient composting to LJH19. Additionally, the strain possessed multiple PGP traits such as indole acetic acid production (166.11 ± 5.7 μg/ml), siderophore production (85.72 ± 1.06% psu), and phosphate solubilization (44.76 ± 1.5 μg/ml). Enhanced germination index and germination rate of pea seeds under the LJH19 inoculation further supported the bacterium's PGP potential. Whole-genome sequencing (3,602,821 bps) and genome mining endorsed the cold adaptation, degradation of polysaccharides, and PGP traits of LJH19. Biosynthetic gene clusters for type III polyketide synthase (PKS), terpene, and siderophore supplemented the endorsement of LJH19 as a potential PGP bacterium. Comparative genomics within the genus revealed 217 unique genes specific to hydrolytic and PGP activity.

CONCLUSION

The physiological and genomic evidence promotes LJH19 as a potentially safe bio-inoculant to formulate psychrotrophic bacterial consortia for accelerated degradation and improved night-soil compost.

Modified cornstalk biochar can reduce ammonia emissions from compost by increasing the number of ammonia-oxidizing bacteria and decreasing urease activity

This study examined how the addition of modified cornstalk biochar (CB) affected ammonia (NH₃) emissions during composting. Four treatments were established, including a control (CK) with layer manure and sawdust only, and the CK mixtures adding 10% HNO₃ CB (NA), 10% H₂O₂ CB (HP) and 10% HNO₃- H₂O₂ CB (MI). As the results showed, NH₃ emissions was reduced by 47.83% (NA), 61.69% (HP) and 45.69% (MI) when the modified CB used as a compost additive (P < 0.05). According to the data analysis, the addition of modified CB significantly increased the number of ammonia-oxidizing bacteria (AOB), inhibited urease activity and decreased the abundance of narG and nirS at rising temperatures and high temperatures (P < 0.05). Redundancy analysis demonstrated a negative correlation between NH₃ emissions and AOB and a positive correlation with urease activity, narG and nirS. Thus, the modified CB helped reduce NH₃ emissions by regulating nitrification processes.

Effect of Cornstalk Biochar Immobilized Bacteria on Ammonia Reduction in Laying Hen Manure Composting

NH₃ emission has become one of the key factors for aerobic composting of animal manure. It has been reported that adding microbial agents during aerobic composting can reduce NH₃ emissions. However, environmental factors have a considerable influence on the activity and stability of the microbial agent. Therefore, this study used cornstalk biochar as carriers to find out the better biological immobilization method to examine the mitigation ability and mechanism of NH₃ production from laying hen manure composting. The results from different immobilized methods showed that NH₃ was reduced by 12.43%, 5.53%, 14.57%, and 22.61% in the cornstalk biochar group, free load bacteria group, mixed load bacteria group, and separate load bacteria group, respectively. Under the simulated composting condition, NH₃ production was 46.52, 38.14, 39.08, and 30.81 g in the treatment of the control, mixed bacteria, cornstalk biochar, and cornstalk biochar separate load immobilized mixed bacteria, respectively. The cornstalk biochar separate load immobilized mixed bacteria treatment significantly reduced NH₃ emission compared with the other treatments (p < 0.05). Compared with the control, adding cornstalk biochar immobilized mixed bacteria significantly decreased the electrical conductivity, water-soluble carbon, total nitrogen loss, and concentration of ammonium nitrogen (p < 0.05), and significantly increased the seed germination rate, total number of microorganisms, and relative abundance of lactic acid bacteria throughout the composting process (p < 0.05). Therefore, the reason for the low NH₃ emission might be due not only to the adsorption of the cornstalk biochar but also because of the role of complex bacteria, which increases the relative abundance of lactic acid bacteria and promotes the acid production of lactic acid bacteria to reduce NH₃ emissions. This result revealed the potential of using biological immobilization technology to reduce NH₃ emissions during laying hen manure composting.