NH3 and greenhouse gas emissions during co-composting of lignite and poultry wastes and the following amendment of co-composted products in soil

Ammonia (NH3) and greenhouse gas (GHG) emissions are substantial contributors to C and N loss in composting. Lignite can increase N retention by absorbing N H 4 + and NH3. However, the effects of co-composting on NH3 and GHG emissions in view of closing nutrient cycle are still poorly investigated. In the study, poultry litter was composted without (CK) or with lignite (T1) or dewatered lignite (T2), and their respective composts N H 4 + Com_CK, Com_T1, and Com_T2) were tested in a soil incubation to assess NH3 and GHG emission during composting and following soil utilization. The cumulative NH3 flux in T1 and T2 were reduced by 39.3% and 50.2%, while N2O emissions were increased by 7.5 and 15.6 times, relative to CK. The total GHG emission in T2 was reduced by 16.8% compared to CK. Lignite addition significantly increased nitrification and denitrification as evidenced by the increased abundances of amoA, amoB, nirK, and nirS. The increased reduction on NH3 emission by dewatered lignite could be attributed to reduced pH and enhanced cation exchangeable capacity than lignite. The increased N2O was related to enhanced nitrification and denitrification. In the soil incubation experiment, compost addition reduced NH3 emission by 72%∼83% while increased emissions of CO2 and N2O by 306%∼740% and 208%∼454%, compared with urea. Com_T2 strongly reduced NH3 and GHG emissions after soil amendment compared to Com_CK. Overall, dewatered lignite, as an effective additive, exhibits great potential to simultaneously mitigate NH3 and GHG secondary pollution during composting and subsequent utilization of manure composts.

Modified lignite and black coal reduce ammonia volatilization from cattle manure

Modified lignite and black coal (BC) are potential amendments for animal bedding to abate ammonia (NH₃) emissions due to their large adsorption capacities for ammoniacal nitrogen (N). However, the ability of modified lignite and BC in reducing NH₃ volatilization from livestock manure and the underlying mechanisms remain unknown. The present study has investigated the effect of lignite, modified lignite, BC and modified BC on NH₃ volatilization from cattle manure, biological immobilization of manure ammoniacal N and manure properties. Modified lignite and BC reduced the NH₃ volatilization from manure by 44 and 36%, respectively, which were comparable with original lignite (43%). The biological immobilization of applied stable isotope labelled ¹⁵N in lignite, modified lignite, BC and modified BC amended manures was 15, 18, 11 and 16%, respectively, which were significantly higher than that in unamended manure (4%, P < 0.001). In addition, NH₄⁺-N concentrations of lignite, modified lignite and modified BC amended manures (7.0-7.3 mg g^-1) were significantly higher than that of the unamended and original BC amended manures (3.3 and 4.8 mg g^-1, respectively, P < 0.001). However, the manure pH in all treatments remained alkaline (pH > 8.2). Our results highlight that the adsorption and immobilization of manure ammoniacal N induced by amendments are the key drivers in reducing NH₃ loss from manure, outweighing the pH effect. The findings of this study provide new insights into the mechanisms of coal amendments reducing NH₃ loss from animal manure and their potential applications in intensive livestock systems.

Lignite as additives accelerates the removal of antibiotic resistance genes during poultry litter composting

Antibiotic resistance genes (ARGs) in animal manure are a great threat to human health. This study investigated the effects of lignite addition at three levels (5%, 10%, 15% w/w) on the profiles of ARGs and the bacterial communities during poultry litter composting. Lignite addition effectively promoted the removal of manure-borne ARGs. After 65 days of composting, the relative abundances of ARGs decreased by 8.9% in control (no lignite), and by 15.8%, 27.7% and 41.5% in 5%, 10% and 15% lignite treatments, respectively. Although the total mobile genetic elements were enriched after composting, the enrichment of the intI-1 gene was significantly lower in the 10% and 15% lignite treatments compared with control. Network analysis indicated that Actinobacteria and Firmicutes were potential bacterial hosts for ARGs. Redundancy analysis showed that bacterial community succession played a key role in the shifts of ARGs. Taken together, this study provides evidence that lignite as additives promoted the removal efficacy of ARGs during composting of poultry litter.

Gas emissions during cattle manure composting and stockpiling

Manure composting is a common management practice for cattle feedlots, but gaseous emissions from composting are poorly understood. The objective of this study was to quantify ammonia (NH₃ ), nitrous oxide (N₂ O), carbon dioxide (CO₂ ), and methane (CH₄ ) emissions from windrow composting (turning) and static stockpiling (nonturning) of manure at a commercial feedlot in Australia. An inverse-dispersion technique using an open-path Fourier transform infrared (OP-FTIR) spectrometer gas sensor was deployed to measure emissions of NH₃ , N₂ O, CO₂ , and CH₄ over a 165-d study period, and 29 and 15% of the total data intervals were actually used to calculate the fluxes for the windrow and stockpile, respectively. The nitrogen (N) lost as NH₃ and N₂ O emissions represented 26.4 and 3.8% of the initial N in windrow, and 5.3 and 0.8% of that in the stockpile, respectively. The carbon (C) lost as CO₂ and CH₄ emissions represented 44 and 0.3% of the initial C in windrow, and 54.8 and 0.7% of that in the stockpile, respectively. Total greenhouse gas (GHG) emissions from the manure windrow were 2.7 times higher than those of the stockpiled manure. This work highlights the value that could be accrued if one could reduce emissions of NH₃ -N and N₂ O-N from composting, which would retain manure N content while reducing GHG emissions.

Spectroscopic evidence for hyperthermophilic pretreatment intensifying humification during pig manure and rice straw composting

Hyperthermophilic pretreatment composting (HPC) is superior to traditional composting (CK) with shortened maturity period and enhanced humification degree. However, the chemical and structural evolution of humic substances (HS) at the molecular level is not known. In this study, the impact of hyperthermophilic pretreatment (90 °C, 4 h) on the content and chemical composition of HS during composting were investigated. The HS content of the final compost was 87.8 g/kg and 76.7 g/kg in HPC and CK, respectively. Significantly higher humic acid/fulvic acid ratio (1.27 in HPC v.s. 0.77 in CK) was observed in HPC. ¹³C NMR spectroscopic data showed a higher aromatics percentage and earlier enrichment of aromatic structures in HS extracted from HPC than CK. Intensified humification of HPC was related to the increased levels of HS precursors and degradation of lignocellulose. Redundancy analysis demonstrated that aromatic C, phenolic C and O-alkyl C can be used for evaluation of the humification degree.