Relating bacterial dynamics and functions to greenhouse gas and odor emissions during facultative heap composting of four kinds of livestock manure

The production of methyl mercaptan is the main odor source of chicken manure treated with a vertical aerobic fermenter

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.

Firmicutes primarily drive odor emission profiles in poultry manure treatments

Odor emission during livestock manure treatment poses a threat to the environment and human health. However, the odor emission profiles and related factors of commonly employed poultry manure treatments have rarely been studied. Here, we explored the odor emission profiles of 3 common poultry manure treatments in China, namely, ectopic fermentation beds (EFB), annular composting troughs (ACT) and air-drying rooms (ADR). The results revealed that the total odor concentrations in the EFB, ACT and ADR groups were 2407.67 ± 512.94, 13444.00 ± 1269.92 and 621.33 ± 59.27, respectively. The ACT had the greatest number of odorants (31), followed by the ADR (27) and the EFB (24). Methyl mercaptan, acetic acid, acetaldehyde, hydrogen sulfide, ammonia and acrolein were the key odorous compounds detected in all the treatments. ACT contained the greatest number of key odorants (11) and exhibited an extensive co-occurrence relationship with the bacterial community. The 3 poultry manure treatments exhibited significant differences in the beta diversities of the bacterial community. The phylum of most bacteria associated with key odorants was Firmicutes, and Enterococcus and Oceanobacillus were significantly positively correlated with methyl mercaptan. The bacterial functional groups were enriched in carbohydrate metabolism, amino acid metabolism and energy metabolism, and the functional genes shaped the odor emission patterns in the poultry manure treatments. Redundancy analysis demonstrated that odor emission in the 3 treatments was positively correlated with Firmicutes abundance, pH, electrical conductivity and moisture. Thus, our study provides a good understanding of odor emission profiles in poultry manure treatments and data for precise odor emission control during livestock production.

Innovative insights into organic nitrogen degradation through protein family domains analysis in chicken and pig manure composting using metagenomic sequencing

The nitrogen loss in composting is primarily driven by the transformation of organic nitrogen, yet the mechanisms underlying the degradation process remain incompletely understood. This study employed protein family domains (Pfams) analysis based on metagenomic sequencing to investigate the functional characteristics, key microorganisms, and environmental parameters influencing organic nitrogen degradation in chicken manure and pig manure composting. 154 Pfams associated with ammonification function were identified. Predominant Pfams: proteolytic peptidase, followed by chitin/cell wall degraders, least involved in nucleic acid degradation. Ammonifying microbial diversity was basically consistent among compost types, particularly in the thermophilic stage with the peak of abundance of dominant ammonifying microorganisms. Viruses played an important role in ammonification process, especially Uroviricota. 26 key ammonifying genera were identified by the microbial network. pH dominated the metabolic activity of ammonifying microorganisms in various manure compost types, primarily consisting of protein-degrading bacteria with stable community structures.

Co-composting of dewatered sludge and wheat straw with newly isolated Xenophilus azovorans: Carbon dynamics, humification, and driving pathways

Composting is a biological reaction caused by microorganisms. Composting efficiency can be adequately increased by adding biochar and/or by inoculating with exogenous microorganisms. In this study, we looked at four methods for dewatered sludge waste (DSW) and wheat straw (WS) aerobic co-composting: T1 (no additive), T2 (5% biochar), T3 (5% of a newly isolated strain, Xenophilus azovorans (XPA)), and T4 (5% of biochar-immobilized XPA (BCI-XPA)). Throughout the course of the 42-day composting period, we looked into the carbon dynamics, humification, microbial community succession, and modifications to the driving pathways. Compared to T1 and T2, the addition of XPA (T3) and BCI-XPA (T4) extended the thermophilic phase of composting without negatively affecting compost maturation. Notably, T4 exhibited a higher seed germination index (132.14%). Different from T1 and T2 treatments, T3 and T4 treatments increased CO2 and CH4 emissions in the composting process, in which the cumulative CO2 emissions increased by 18.61-47.16%, and T3 and T4 treatments also promoted the formation of humic acid. Moreover, T4 treatment with BCI-XPA addition showed relatively higher activities of urease, polyphenol oxidase, and laccase, as well as a higher diversity of microorganisms compared to other processes. The Functional Annotation of Prokaryotic Taxa (FAPROTAX) analysis showed that microorganisms involved in the carbon cycle dominated the entire composting process in all treatments, with chemoheterotrophy and aerobic chemoheterotrophy being the main pathways of organic materials degradation. Moreover, the presence of XPA accelerated the breakdown of organic materials by catabolism of aromatic compounds and intracellular parasite pathways. On the other hand, the xylanolysis pathway was aided in the conversion of organic materials to dissolved organics by the addition of BCI-XPA. These findings indicate that XPA and BCI-XPA have potential as additives to improve the efficiency of dewatered sludge and wheat straw co-composting.

Evaluation of gases emission and enzyme dynamics in sheep manure compost occupying with peach shell biochar

The effect of peach shell biochar (PSB) amendment on sheep manure (SM) composting was investigated. Five different ratios of PSB were applied (0%, 2.5%, 5%, 7.5%, and 10% PSB), and named T1 to T5, and run 50 days of composting experiment. It was found that PSB (especially 7.5% and 10%) could improve the compost environment, regulate the activity of microorganisms and related enzymes, and promote the decomposition of compost. 7.5% and 10% PSB advanced the heap into the thermophilic stage and increased the maximum temperature, while also increasing the germination index by 1.40 and 1.39 times compared to control. Importantly, 10% PSB effectively retained more than 60% of carbon and 55% of nitrogen by inhibiting the excess release of NH3 and greenhouse gases. High proportion PSB amendment increased the activity of dehydrogenase and cellulase, but inhibited protease and urease. The correlation results indicated that PSB changed the key bacterial genus, and there was a stronger association with environmental factors at 7.5% and 10%. Therefore, 7.5% and 10% peach shell biochar can be used as appropriate proportions to improve composting conditions.

Cultivating a sustainable future in the artificial intelligence era: A comprehensive assessment of greenhouse gas emissions and removals in agriculture

Agriculture is a leading sector in international initiatives to mitigate climate change and promote sustainability. This article exhaustively examines the removals and emissions of greenhouse gases (GHGs) in the agriculture industry. It also investigates an extensive range of GHG sources, including rice cultivation, enteric fermentation in livestock, and synthetic fertilisers and manure management. This research reveals the complex array of obstacles that are faced in the pursuit of reducing emissions and also investigates novel approaches to tackling them. This encompasses the implementation of monitoring systems powered by artificial intelligence, which have the capacity to fundamentally transform initiatives aimed at reducing emissions. Carbon capture technologies, another area investigated in this study, exhibit potential in further reducing GHGs. Sophisticated technologies, such as precision agriculture and the integration of renewable energy sources, can concurrently mitigate emissions and augment agricultural output. Conservation agriculture and agroforestry, among other sustainable agricultural practices, have the potential to facilitate emission reduction and enhance environmental stewardship. The paper emphasises the significance of financial incentives and policy frameworks that are conducive to the adoption of sustainable technologies and practices. This exhaustive evaluation provides a strategic plan for the agriculture industry to become more environmentally conscious and sustainable. Agriculture can significantly contribute to climate change mitigation and the promotion of a sustainable future by adopting a comprehensive approach that incorporates policy changes, technological advancements, and technological innovations.

Functional redundancy is the key mechanism used by microorganisms for nitrogen and sulfur metabolism during manure composting

The microbial ecological functions associated with the nitrogen and sulfur cycles during composting have not been thoroughly elucidated. Using metagenomic sequencing, the microbial mechanisms underlying the nitrogen and sulfur metabolism during livestock and poultry manure composting were investigated in this study. The findings demonstrate that functional redundancy among microorganisms is a crucial factor for the nitrogen and sulfur cycling during livestock and poultry manure composting. Processes such as organic sulfur synthesis, assimilatory sulfate reduction, ammonia assimilation, and denitrification were found to be prevalent. Additionally, there was a certain degree of conservation in nitrogen and sulfur conversion functions among microorganisms at the phylum level. All high-quality metagenomic assembly genomes (MAGs) possessed carbon fixation potential, with 86.3 % of MAGs containing both nitrogen and sulfur conversion genes. Except for bin30, other MAGs encoding sulfur oxidation enzymes were found to be associated with at least one denitrification gene. This suggests a potential interplay between nitrogen and sulfur metabolism among microorganisms. 45, 19, 1, 31, 1, and 2 MAGs could completely regulate organic sulfur synthesis, assimilatory sulfate reduction, thiosulfate oxidation to sulfate, glutamine synthase-glutamate synthase pathway (GS-GOGAT), denitrification, and dissimilatory nitrate reduction, respectively by encoding the required enzymes. TN and pH were the key factors driving the functional redundancy in nitrogen and sulfur microbial community.

Impacts of climate change on the fate of contaminants through extreme weather events

The direct impacts of climate change involve a multitude of phenomena, including rising sea levels, intensified severe weather events such as droughts and flooding, increased temperatures leading to wildfires, and unpredictable fluctuations in rainfall. This comprehensive review intends to examine firstly the probable consequences of climate change on extreme weather events such as drought, flood and wildfire. This review subsequently examines the release and transformation of contaminants in terrestrial, aquatic, and atmospheric environments in response to extreme weather events driven by climate change. While drought and flood influence the dynamics of inorganic and organic contaminants in terrestrial and aquatic environments, thereby influencing their mobility and transport, wildfire results in the release and spread of organic contaminants in the atmosphere. There is a nascent awareness of climate change's influence of climate change-induced extreme weather events on the dynamics of environmental contaminants in the scientific community and decision-making processes. The remediation industry, in particular, lags behind in adopting adaptive measures for managing contaminated environments affected by climate change-induced extreme weather events. However, recognizing the need for assessment measures represents a pivotal first step towards fostering more adaptive practices in the management of contaminated environments. We highlight the urgency of collaboration between environmental chemists and climate change experts, emphasizing the importance of jointly assessing the fate of contaminants and rigorous action to augment risk assessment and remediation strategies to safeguard the health of our environment.

Comparing bacterial dynamics for the conversion of organics and humus components during manure composting from different sources

The study aimed to compare the differences in organic fractions transformation, humus components and bacterial community dynamics during manure composting from different sources, and to identify the key biotic and abiotic factors driving the humification process. Five types of manure [pig manure (PM), cow dung (CD), sheep manure (SM), chicken manure (CM), and duck manure (DM)] were used as raw materials for 30 days composting. The results showed the obvious difference of organic fractions decomposition with more cellulose degradation in CD and SM composting and more hemicellulose degradation in PM and CM composting. Composting of PM and CD contained significantly higher humus fractions than the other composts. Fluorescence spectra indicated that SM composting tended to form structurally stable humic acid fractions, while CM and DM tended to form structurally complex fulvic acid fractions. Pearson correlation analysis showed that humification process of composts in category A (PM, CD) with higher humification degree than category B (SM, CM, and DM) was positively correlated with lignin and hemicellulose degradation. Bioinformatics analysis found that Lysinibacillus promoted the degradation of hemicellulose and the conversion of fulvic to humic acid in the composts of category A, and in category B, Thermobifida, Lactobacillus, and Ureibacillus were key genera for humic acid formation. Network analysis indicated that bacterial interaction patterns had obvious differences in composting with different humus and humification levels.