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

Hydrogen peroxide-aged biochar mitigating greenhouse gas emissions during co-composting of swine manure with rice bran

Compared to fresh biochar, aged biochar has a more significant effect on mitigating greenhouse gas (GHG) emissions in farmland soil. However, there is a relative scarcity of research addressing this effect in aerobic composting. In this study, a co-composting of swine manure and rice bran (NBC), with the addition of fresh biochar (FBC) and hydrogen peroxide-aged biochar (ABC), was conducted to investigate the dynamic changes in physicochemical properties, microbial communities, GHG emissions and related functional genes during different periods. In comparison to NBC, FBC led to a 32 % decrease in total GHG emissions (CO2-equiv), including a 29 % reduction in CO2 emissions, a 45 % reduction in CH4 emissions, and a 35 % decrease in N2O emissions. Furthermore, ABC resulted in a 14 % decrease in GHG emission (CO2-equiv), comprising a 47 % reduction in CH4 emissions and a 23 % decrease in N2O emissions compared to FBC. These findings indicated that the addition of aged biochar has a more significant impact on GHG reduction during composting. Network analyses, Mantel tests and redundancy analyses suggested that the mechanism behind the lowest GHG emissions in ABC is the reduction of the relative abundance of fungi associated with CH4 emissions, along with the nirS and nirK genes associated with denitrification. This reduction is associated with the decreasing anaerobic zones resulting from the increased pore volume in biochar after aging. Overall, this study demonstrates that hydrogen peroxide aging enhances the GHG-reducing efficiency in biochar, and provides new insights into the development of GHG-reducing technologies in composting.

Exploring the influence of moisture stress on microbial-driven organic acid synthesis in potato waste fermentation

Anaerobic fermentation of potato leaves and stems for organic acid synthesis, serving as food additives, faces impediments due to misconceptions about the effects of moisture stress on the acid-synthesizing microbiome. An ingenious method, avoiding interference from microbiome and nutrient integrations, was employed in the present study. Results showed that increasing the moisture level from 60 % to 75 % significantly improved lactic acid (182.64 %), acetic acid (163.55 %), propionic acid (1960.43 %), nonprotein nitrogen, free amino acid and ammonia levels but reduced pH value and water-soluble carbohydrate and hemicellulose levels. Microbiologically, the high-moisture groups enriched Lactiplantibacillus, Levilactobacillus and Enterobacter, upregulated glycolysis, nitrogen, pyruvate and propanoate metabolisms, and activated genes for acid-producing and ammonia-forming enzymes. Notably, Lactiplantibacillus and Enterobacter prevailed in glycolysis and nitrogen metabolism, respectively, and Levilactobacillus was more prominent in pyruvate and propanoate metabolism under high-moisture conditions. Collectively, a moisture level of 75 % benefited organic acid synthesis from potato waste via anaerobic fermentation.

Effects of selenate on greenhouse gas release and microbial community variations during swine manure composting

Co-composting of livestock manure and selenate is an effective means to produce selenium-rich organic fertilizer. However the effect of selenate on greenhouse gas emission during composting is still unknown. To probe the influences of selenate on greenhouse gas and microbial community changes during swine manure composting. Various dose of selenate were added to the fresh swine manure and wheat straw for 80 days aerobic composting, sequentially labeled as T1 (control) to T6 (0, 1, 2, 3, 4 and 5 mg kg-1). Results indicated that selenate generally increased the nitrous oxide (N2O) and ammonia (NH3) emissions while presented varying impacts on methane (CH4) emissions. Compared with the control, adding 2 and 5 mg kg-1 selenate reduced the CH4 emission by 39.60% and 13.75%, respectively, while other concentrations presented opposite results. Meanwhile, adding 2 mg kg-1 selenate could reduce the global warming potential and improve the compost maturity. According to the microbial results, adding 2 mg kg-1 selenate enhanced the richness and variety of the microbes and might influence Proteobacteria, Chloroflexi, Actinobacteria and Methylococcaceae_unclassified to decrease the global warming potential.

The measurement and insight of bacterial community structure succession in cyanobacteria biochar co-composting based on basic carbon and nitrogen indices

The effects of cyanobacteria biochar (CB) amendment on microbial community succession (MCS) during pig manure co-composting was evaluated. Conventional composting (T1) and different concentrations of CB co-composting were set up here (T2: 2.5% CB, T3: 5% CB, T4: 7.5% CB, T5: 10% CB, and T6: 20% CB). Core substrate indicators and microbial information were used to gain insight into microbial community succession structure (MCSS) by CB treatments. Low concentrations of CB show higher organic degradation rates (2.4% vs 2.2%; and Y = C ∗(1- e(-k∗x))), while high concentrations increased the content of TKN (T5: 54.40%). An innovative diversity quantization method (pan-γ-diversity T5:42.275, T1: 40.642, and T2: 34.285) was proposed through linear simulation and integration. CB optimized Bacillus and Thermobacillus were key organic degradation genera during succession (collaborate with Caldicoprobacter) and increased the abundance of important nitrogen fixation genera Chelativorans (Day 42: minimun 4.8 times; and Day 72: minimum 1.3 times) and Longispora (Max 10.0%). The existence of bacteria Caldicoprobacter (2.0-9.3%) on mineralization process showed the synergy and co-assembly effects of CB on MCSS. Moreover, mantel test also shows the assembled and cooperation of Firmicutes and Actinobacteria.

Magnetic biochar accelerates microbial succession and enhances assimilatory nitrate reduction during pig manure composting

Biochar promotes microbial metabolic activities and reduces N2O on aerobic composting. However, the effects of magnetic biochar (MBC) on the microbial succession and N2O emissions during pig manure composting remain unclear. Herein, a 42-day composting experiment was conducted with five treatment regimes: pig manure without biochar (CK), 5 % pig manure-based biochar (5 % PBC), 2 % MBC (2 % MBC), 5 % MBC (5 % MBC) and 7.5 % MBC (7.5 % MBC)), to clarify the variation in functional microorganisms and genes associated with nitrogen and direct interspecies electron transfer via metagenomics. Fourier-transform infrared spectroscopy showed that MBC possessed more stable aromatic structures than pig manure-based biochar (PBC), indicating its greater potential for nitrous oxide reduction. MBC treatments were more effective in composting organic matter and improving the carbon/nitrogen ratio than PBC. The microbial composition during composting varied significantly, with the dominant phyla shifting from Firmicutes to Proteobacteria, Actinobacteria, and Bacteroidota. Network and hierarchical clustering analyses showed that the MBC treatment enhanced the interactions of dominant microbes (Proteobacteria and Bacteroidota) and accelerated the composting process. The biochar addition accelerated assimilatory nitrate reduction and slowed dissimilatory nitrate reduction and denitrification. The Mantel test demonstrated that magnetic biochar potentially helped regulate composting nutrients and affected functional nitrogen genes. These findings shed light on the role of MBC in mitigating greenhouse gas emissions during aerobic composting.