Exogenous enzyme amendment accelerates maturity and changes microflora succession in horse and wildlife animal manure co-composting

Mitigation of ammonia and hydrogen sulfide emissions during aerobic composting of laying hen waste through NaOH-modified biochar

The impact of NaOH-modified biochar on the release of NH3 and H2S from laying hens' manure was examined for 44 days, using a small-scale simulated aerobic composting system. The findings revealed that the NaOH-modified biochar reduced NH3 and H2S emissions by 40.63% and 77.78%, respectively, compared to the control group. Moreover, the emissions of H2S were significantly lower than those of the unmodified biochar group (p < 0.05). The increased specific surface area and microporous structure of the biochar, as well as the higher content of alkaline and oxygenated functional groups, were found to facilitate the adsorption of NH3 and H2S. This enhanced adsorption capability was the primary reason for the significant reduction in NH3 emissions. Furthermore, during the high-temperature phase of composting, there was a notable alteration in the microbial community. The abundance of Limnochordaceae, Savagea, and IMCC26207 increased significantly which aided in the conversion of H2S to stable sulfate. These microorganisms also influenced the abundance of functional genes involved in sulfur metabolism, thereby inhibiting cysteine synthesis, along with the decomposition and conversion of sulfate to sulfite. This led to a significant decrease in H2S emissions. This study provides valuable data for the selection of deodorizers in the composting process of egg-laying hens. The results have significant implications for the application of NaOH-modified biochar for odor reduction in aerobic composting processes.

Evaluating the potential of different bioaugmented strains to enhance methane production during thermophilic anaerobic digestion of food waste

Bioaugmentation technology for improving the performance of thermophilic anaerobic digestion (TAD) of food waste (FW) treatment is gaining more attention. In this study, four thermophilic strains (Ureibacillus suwonensis E11, Clostridium thermopalmarium HK1, Bacillus thermoamylovorans Y25 and Caldibacillus thermoamylovorans QK5) were inoculated in the TAD of FW system, and the biochemical methane potential (BMP) batch study was conducted to assess the potential of different bioaugmented strains to enhance methane production. The results showed that the cumulative methane production in groups inoculated with E11, HK1, Y25 and QK5 improved by 2.05%, 14.54%, 19.79% and 9.17%, respectively, compared with the control group with no inoculation. Moreover, microbial community composition analysis indicated that the relative abundance of the main hydrolytic bacteria and/or methanogenic archaea was increased after bioaugmentation, and the four strains successfully became representative bacterial biomarkers in each group. The four strains enhanced methane production by strengthening starch, sucrose, galactose, pyruvate and methane metabolism functions. Further, the correlation networks demonstrated that the representative bacterial genera had positive correlations with the differential metabolic functions in each bioaugmentation group. This study provides new insights into the TAD of FW with bioaugmented strains.

Impact of Aspergillus fumigatus inoculation on the composting of wood shaving bedding for horses

Equine farming generates a significant amount of waste, prompting the need for effective management. Composting enhanced by filamentous fungi holds promise for this purpose. This study focused on inoculating Aspergillus fumigatus isolates in composting horse bedding made with wood shavings (Pinus elliottii). The experiment lasted 90 days, with two treatment groups, control and inoculated, analyzing temperature, pH, electrical conductivity, total organic carbon and nitrogen content, and cellulose, hemicellulose, and lignin contents. Both treatments entered the thermophilic phase by the fourth day, reaching temperatures above 55°C and mesophilic maturation at 35 days (41 ± 0.2°C). The inoculated treatment exhibited higher electrical conductivity after 30 days and a more pronounced reduction in the total carbon content (42.85% vs. 38.29%) compared to the control. While there was no significant nitrogen difference, the inoculated treatment had a sharper reduction in carbon/nitrogen ratio, and cellulose and hemicellulose contents. Both treatments showed low coliform counts, no Salmonella sp., and reduced Strongyloides sp. larvae. Inoculating A. fumigatus in saturated horse bedding made from wood shavings improved compost quality, providing a possibility for sustainable equine farming waste treatment.

A review of the definition, influencing factors, and mechanisms of rapid composting of organic waste

Composting is a traditional method of treating organic waste. A growing number of studies have been focusing on accelerating the process to achieve "rapid composting." However, the specific definition and influencing factors of rapid composting remain unclear. Therefore, we aimed to gather more insight into the features of rapid composting by reviewing the literature concerning organic waste composting published in the Web of Science database in the past 5 years. We selected 1615 sample studies with "composting" as the subject word and analyzed the effective composting time stated in each study. We defined rapid composting within 15 days using the median test and quartile method. Based on this definition, we summarized the influencing factors of "rapid composting," namely materials, reactors, temperature, and microorganisms. Finally, we summarized two mechanisms related to humus formation during organic waste rapid composting: high temperature-promoting maturation and microbial driving mechanisms. This literature review compiled useful references to help promote the development of rapid composting technology and related equipment.

Effects of peach branch organic fertilizer on the soil microbial community in peach orachards

Peach branches is a by-product of peach industry. Making peach branch waste into peach branch organic fertilizer (PBOF) is a promising strategy of ecological utilization. In this study, the effects of PBOF on the yield and quality of peach fruit, chemical properties of bulk soil, and soil bacterial communities were investigated in a peach orchard. The results showed that the yield and sugar/acid ratio of two high-level PBOF treatments (SDH.4 and SKR.4) was higher than no fertilization treatment (CK), but there was no significant difference compared to the commercial organic fertilizer treatment (SYT.4). Moreover, the three fertilizer treatments increased soil nutrients such as soil organic matter (SOM) and available potassium (AK), compared to CK. Furthermore, PBOF increased the relative abundance of beneficial bacteria, and enhanced the soil bacterial co-occurrence pattern and the potential function of bacterial communities to degrade exogenous compounds. In addition, thanks to the local policy of encouraging the use of PBOF, the use cost of PBOF is lower than commercial organic fertilizer, which is conducive to the development of ecological agriculture.

Insights into the Applications of Extracellular Laccase-Aided Humification in Livestock Manure Composting

Traditional composting is a well-suited biotechnology for on-farm management of livestock manure (LM) but still leads to the release of toxic micropollutants and imbalance of nutrients. One in situ exoenzyme-assisted composting has shown promise to ameliorate the agronomical quality of end products by improving humification and polymerization. The naturally occurring extracellular laccase from microorganisms belongs to a multicopper phenoloxidase, which is verified for its versatility to tackle micropollutants and conserve organics through the reactive radical-enabled decomposition and polymerization channels. Laccase possesses an indispensable relationship with humus formation during LM composting, but its potential applications for the harmless disposal and resource utilization of LM have until now been overlooked. Herein, we review the extracellular laccase-aided humification mechanism and its optimizing strategy to maintain enzyme activity and in situ production, highlighting the critical roles of laccase in treating micropollutants and preserving organics during LM composting. Particularly, the functional effects of the formed humification products by laccase-amended composting on plant growth are also discussed. Finally, the future perspectives and outstanding questions are summarized. This critical review provides fundamental insights into laccase-boosted humification that ameliorates the quality of end products in LM composting, which is beneficial to guide and advance the practical applications of exoenzyme in humification remediation, the carbon cycle, and agriculture protection.

Effect of thermophilic microbial agents on nitrogen transformation, nitrogen functional genes, and bacterial communities during bean dregs composting

This study explored how a thermophilic microbial agent altered nitrogen transformation, nitrogen functional genes, and bacterial communities during bean dregs composting with (T) and without (CK) a thermophilic microbial agent for 15 days. The results showed that the maximum temperature in T reached 73 °C and remained above 70 °C for 8 days, while that in CK was only 65 °C. The pH in T had essentially stabilized on day 7, while that in CK was still increasing. On day 15, the seed germination index (GI) of T (95%) reached maturity (defined by GI ≥ 85%), while the GI of CK was only 36%. The concentrations of total nitrogen, water-soluble nitrogen, ammonia nitrogen, and nitrate nitrogen in T (2.5%, 18.9 g/kg, 8.75 g/kg, and 1.69 g/kg) were all lower than those in CK (3.6%, 28.9 g/kg, 12.75 g/kg, and 6.82 g/kg). During composting, Bacillus played a major role in nitrogen reduction, nitrogen mineralization, denitrification, and the conversion between nitrite and nitrate. Weissella played a major role in nitrogen assimilation. Komagataeibacter and Bacillus played a major role in nitrogen fixation in CK and T, respectively. Nitrification was not observed during composting. The nosZ gene, which converts nitrous oxide to nitrogen, was found only in T. Network analysis suggested that the average number of neighbours in T was 3.30% higher than that in CK and the characteristic path length in T was 14.15% higher than that in CK. Therefore, the thermophilic microbial agents could cause nitrogen loss but promote the maturity of bean dregs, which have great potential application.

Dynamic Microstructure Assembly Driven by Lysinibacillus sp. LF-N1 and Penicillium oxalicum DH-1 Inoculants Corresponds to Composting Performance

The effects of Lysinibacillus sp. LF-N1 and Penicillium oxalicum DH-1 inoculants (LFPO group) on compost succession and the microbial dynamic structure of co-composting wheat straw and cow manure composting were investigated. The inoculants contributed to longer thermophilic stages, higher temperatures (62.8 °C) and lower microbial diversity in the LFPO treatment compared to the control group (CK). Moreover, LFPO inoculation increased the germination index and accelerated organic matter and lignocellulose degradation in the compost. Microbial analysis confirmed that the inoculants effectively altered the microbial communities. The predominant biomarkers for bacteria and fungi in inoculated compost were members of Lysinibacillus and Penicillium, respectively. Functional prediction showed greater lignocellulose degradation and less pathogen accumulation in the LFPO group. The cooccurrence network analysis showed that the network structure in LFPO compost was greatly simplified compared to that in CK. Bacterial cluster A was dominated by Lysinibacillus, and fungal cluster B was represented by Penicillium, which were significantly correlated with temperature and lignocellulose degradation, respectively (p < 0.05). These results demonstrated that the LF-N1 and DH-1 inoculants drove the bacterial and fungal assemblies to induce physicochemical property changes during cocomposting.

Effect of Geobacillus toebii GT-02 addition on composition transformations and microbial community during thermophilic fermentation of bean dregs

Bean dregs can be prepared into organic fertilizer by microbial fermentation. Geobacillus toebii GT-02, which has promoting effect on bean dregs fermentation, was isolated from horse dung and it grows within a range of 40–75 °C and pH 6.50–9.50. The effectiveness of GT-02 addition on composition transformations and the microbial community in bean dregs thermophilic fermentation at 70 °C for 5 days was investigated (T1). Fermentation of bean dregs without GT-02 served as control (CK). The results showed that T1 (the germination index (GI) = 95.06%) and CK (GI = 86.42%) reached maturity (defined by GI ≥ 85%) on day 3 and day 5, respectively. In addition, the total nitrogen loss of T1 (18.46%) on day 3 was lower than that in CK (24.12%). After thermophilic fermentation, the total organic carbon and dry matter loss of T1 (53.51% and 54.16%) was higher than that in CK (41.72% and 42.82%). The mean microbial number in T1 was 4.94 × 10⁷ CFUs/g dry matter, which was 5.37 times higher than that in CK. 16S rDNA sequencing identified Bacillus, Geobacillus and Thermobacillus as dominant in CK, while Bacillus, Ammoniibacillus and Geobacillus were dominant in T1. A canonical correspondence analysis showed that Geobacillus and Ammoniibacillus were positively correlated with the GI. Thus, thermophilic fermentation with GT-02 can promote the maturity of bean dregs, which indicated the potential application value of GT-02 in thermophilic fermentation.

Bacterial dynamics and functions for gaseous emissions and humification in response to aeration intensities during kitchen waste composting

This study revealed bacteria dynamics and functions for gaseous emissions and humification during kitchen waste composting under different aeration intensities (i.e. 0.24, 0.36, and 0.48 L kg^-1 DM min^-1) using high-throughput sequencing with Functional Annotation of Prokaryotic Taxa. Results show that aeration increase restrained bacteria (e.g. Lactobacillus and Acinetobacter) for fermentation, nitrate reduction, and sulphur/sulphate respiration, but enriched thermophilic bacteria (e.g. Thermomonospora and Thermobifida) for aerobic chemohetertrophy, xylanolysis, cellulolysis, and methylotrophy. Thus, high aeration intensity (i.e. above 0.36 L kg^-1 DM min^-1) effectively alleviated the emission of greenhouse gases and hydrogen sulphide, and meanwhile facilitated the production of humus precursors and ammonia. Nevertheless, humification was limited by the conclusion of composting under high aeration conditions due to the consumption of humus precursors for bacterial activity. Thus, aeration intensity should be regulated at different stages indicated by temperature to balance gaseous emissions and humification during kitchen waste composting.

Keystone Taxa Lactiplantibacillus and Lacticaseibacillus Directly Improve the Ensiling Performance and Microflora Profile in Co-Ensiling Cabbage Byproduct and Rice Straw

Ensiling has been widely applied to cope with agricultural solid waste to achieve organic waste valorization and relieve environmental pressure and feedstuff shortage. In this study, co-ensiling of cabbage leaf byproduct and rice straw was performed with inoculation of Lactiplantibacillusplantarum (LP) to investigate the effects of inoculation on ensiling performance and microflora profiles. Compared to the control, LP inoculation preserved more dry matter (DM) content (283.4 versus 270.9 g·kg^-1 fresh matter (FM) on day 30), increased lactic acid (LA) content (52.1 versus 35.8 g·kg^-1 dry matter on day 15), decreased pH (3.55 versus 3.79 on day 15), and caused accumulation of acetic acid (AA), butyric acid (BA), and ammonia. The investigation showed that LP inoculation modified microflora composition, especially resisting potential pathogens and enriching more lactic acid bacteria (LAB) (p < 0.05). Moreover, Lactiplantibacillus and Lacticaseibacillus were identified as the keystone taxa that influenced physicochemical properties and interactions in microflora. They were also the main functional species that directly restrained undesirable microorganisms (p < 0.05), rather than indirectly working via metabolite inhibition and substrate competition (p > 0.05). The results of this present study improve the understanding of the underlying effect of LP inoculation on improving silage quality and facilitate the bio-transformation of cabbage byproduct and rice straw as animal feed.

Exogenous Probiotics Improve Fermentation Quality, Microflora Phenotypes, and Trophic Modes of Fermented Vegetable Waste for Animal Feed

The fermentation of leaf vegetable waste to produce animal feed reduces the environmental impact of vegetable production and transforms leaf vegetable waste into a commodity. We investigated the effect of exogenous probiotics and lignocellulose enzymes on the quality and microbial community of fermented feed (FF) produced from cabbage waste. The addition of exogenous probiotics resulted in increased crude protein (CP) content (p < 0.05), better odor (moderate organic acid and ethanol, with low ammonia-N, p < 0.05), and a lower relative abundance (RA) of pathogens (below 0.4%, p < 0.05) in FF, compared to without. With the addition of exogenous probiotics, only Pediococcus and Saccharomyces were enriched and symbiotic in FF; these were the keystone taxa to reduce the abundance of aerobic, form-biofilms, and pathogenic microorganisms, resulting in an efficient anaerobic fermentation system characterized by facultative anaerobic and Gram-positive bacterial communities, and undefined saprotroph fungal communities. Thus, inoculation of vegetable waste fermentation with exogenous probiotics is a promising strategy to enhance the biotransformation of vegetable waste into animal feed.