Search Results (6)

Chile, one of the top global wine producers, produces a significant quantity of grape pomace waste, composed primarily of peels and seeds, of which their management includes many environmental challenges. Composting offers a sustainable waste management solution, converting organic waste into a rich nutrient and beneficial microorganisms for soil amendment. This study compared traditional turning and static forced aeration composting systems using a mix of grape pomace (70 m³), wheat straw (15 m³), and manure (15 m³). The results show no significant differences in the final compost chemical quality between the two systems. Nevertheless, forced aeration (T1) influenced the bacterial community, particularly during the thermophilic stage, leading to a major differentiation compared to traditional composting (T0). Similar Shannon index values for bacterial diversity across stages suggest that both composting methods support comparable levels of bacterial diversity. However, the fungal communities exhibited more variability, likely due to the differences in temperature and aeration conditions between the windrows, which are known to affect fungal growth and activity. While both composting methods met the Chilean regulatory standards and achieved high-quality compost, the forced aeration system demonstrated advantages in temperature control, microbial diversity, and pathogen suppression, suggesting its potential for more efficient composting in similar agricultural contexts. Full article

With the rapid growth of livestock breeding, manure composting has evolved to be an important source of atmospheric methane (CH₄) which accelerates global warming. Calcium superphosphate (CaSSP), as a commonly used fertilizer, was proposed to be effective in reducing CH₄ emissions from manure composting, but the intrinsic biological mechanism remains unknown. Methanogens and methanotrophs both play a key role in mediating CH₄ fluxes, therefore we hypothesized that the CaSSP-mediated reduction in CH₄ emissions was attributed to the shift of methanogens and methanotrophs, which was regulated by physicochemical parameter changes. To test this hypothesis, a 60-day pig manure windrow composting experiment was conducted to investigate the response of CH₄ emissions to CaSSP amendment, with a close linkage to methanogenic and methanotrophic communities. Results showed that CaSSP amendment significantly reduced CH₄ emissions by 49.5% compared with the control over the whole composting period. The decreased mcrA gene (encodes the α-subunit of methyl-coenzyme M reductase) abundance in response to CaSSP amendment suggested that the CH₄ emissions were reduced primarily due to the suppressed microbial CH₄ production. Illumina MiSeq sequencing analysis showed that the overall distribution pattern of methanogenic and methanotrophic communities were significantly affected by CaSSP amendment. Particularly, the relative abundance of Methanosarcina that is known to be a dominant group for CH₄ production, significantly decreased by up to 25.3% accompanied with CaSSP addition. Only Type I methanotrophs was detected in our study and Methylocaldum was the dominant methanotrophs in this composting system; in detail, CaSSP amendment increased the relative abundance of OTUs belong to Methylocaldum and Methylobacter. Moreover, the increased SO₄²⁻ concentration and decreased pH acted as two key factors influencing the methanogenic and methanotrophic composition, with the former has a negative effect on methanogenesis growth and can later promote CH₄ oxidation at a low level. This study deepens our understanding of the interaction between abiotic factors, function microbiota and greenhouse gas (GHG) emissions, as well as provides implication for practically reducing composting GHG emissions. Full article

This study quantified the potential of farm-scale composting to degrade antibiotics in dairy manure. The compost windrow, consisting of sick cow bedding from a 1000-cow US dairy farm, was managed using the dairy farm’s typical practices and monitored for tetracycline and nutrient composition. Samples were collected over 33 days, which was the time from compost pile formation to land application as fertilizer, and analyzed for solids, antibiotics, and nutrient content. Average tetracycline concentrations at the beginning of the study (452 ng/g DW) were lower than at the end of composting (689 ng/g DW), illustrating that antibiotic degradation was not greater than degradation of the compost solids. Total Kjeldahl nitrogen (TKN) increased from 15.3 to 18.4 g/kg during the composting period due to decreases in solids and likely inhibition of N-mineralization due to the presence of antibiotics. The results indicated that antibiotics were not completely degraded when using the farm’s compost pile management techniques, with antibiotics possibly impacting nitrogen transformation in the compost, which should be considered in nutrient management when using sick cow bedding. Additionally, the results showed that antibiotic degradation during farm-scale composting can vary from reported laboratory-scale due to differences in management, composting duration, and temporal conditions, illustrating the need for more extensive on-farm research including common farm practices and real-world conditions. Full article

Composting is recognized as an effective strategy for the sustainable use of organic wastes, but also as an important emission source of nitrous oxide (N₂O) contributing to global warming. The effects of calcium superphosphate (CaSSP) on N₂O production during composting are reported to be controversial, and the intrinsic microbial mechanism remains unclear. Here, a pig manure windrow composting experiment lasting for ~60 days was performed to evaluate the effects of CaSSP amendment (5%, w/w) on N₂O fluxes in situ, and to determine the denitrifiers’ response, and their driving factors. Results indicated that CaSSP amendment significantly reduced N₂O emissions as compared to the control pile (maximum N₂O emission rate reduced by 64.5% and total emission decreased by 49.8%). CaSSP amendment reduced the abundance of nirK gene encoding for nitrite reductase, while the abundance of nosZ gene (N₂O reductase) was enriched. Finally, we built a schematic model and indicated that the abundance of nirK gene was likely to play a key role in mediating N₂O production, which were correlated with NH₄⁺-N and NO₃⁻-N changing responsive to CaSSP. Our finding implicates that CaSSP application could be a potential strategy for N₂O mitigation in manure windrow composting, and the revealed microbial mechanism is helpful for deepening the understanding of the interaction among N-cycle functional genes, physicochemical factors, and greenhouse gases (GHG) emissions. Full article

Composting is a sustainable alternative for the management of manure. In this study, the effects of bioaugmentation on cattle manure composting was investigated. In this study, two windrow piles were placed at 1.7 m in height, 2.1 m in bottom width, 0.6 m in top width, and 54 m in length. Microbial inoculum was added to pile 1, whereas the second pile was used as the control. After 17 days, the C:N ratio was reduced from 25.6 to 13.6 and the total nitrogen was increased from 1.89% to 3.36% in pile 1. The dominant bacteria identified in the compost samples belonged to the genera Clostridium, Bacillus, and Flavobacterium. Quantitative polymerase chain reaction indicated that the most commonly known pathogenic bacteria, Escherichia coli, Shigella, and Salmonella, were not detected in the finished material, indicating that the pathogenic microorganisms were inactivated by the composting process. Agronomic testing for cured compost indicated a C:N ratio of less than 15 and NH⁺₄-N:NO₃⁻-N ratio of less than 1. The whole process of windrow composting resulted in net greenhouse gas (GHG) emissions of 157.94 tCO₂-e and a global warming factor (GWF) of 1.04 tCO₂-e·t⁻¹ manure composted. This study showed that although bioaugmentation is a feasible treatment method for manure, GHG emissions need to be monitored. Full article

The challenges of accurately measuring in situ ammonia (NH₃) losses from agricultural systems are well known. Using an open path laser coupled with a backward Lagrangian stochastic dispersion model is a promising approach for quantifying both point- and area-sources; however, this approach requires the open path laser to detect low NH₃ concentrations and small concentration differences. In this study, we compared the new GasFinder3 open path laser (Boreal laser Inc., Edmonton, Canada) with the GasFinder2 sensor, the previous version. The study took place at two locations: an outdoor open-air manure compost site, and a field of wheat stubble which was fertilized with urea ammonium nitrate. Results showed the two lasers reported similar concentrations during three days of measurements at the compost site, but differed at the field site, where concentrations were close to the minimum detection limit. The GasFinder3 had a lower standard deviation under all conditions, especially with low wind speed and high relative humidity. Full article