Plant-scale hyperthermophilic composting of sewage sludge shifts bacterial community and promotes the removal of organic pollutants

The dissipation of toxic organic pollutants during plant-scale hyperthermophilic composting and the influence of microbial community remain unclear. The results of plant-scale hyperthermophilic composting of municipal sludge with green waste showed that the residual concentrations of polyaromatic hydrocarbons, phthalates, polybrominated diphenyl ethers were <5 mg/kg and decreased over time, with the removal percentages from 12.1% to 51.2% during seven days of composting. High-throughput sequencingreveals that hyperthermophilic composting significantly reduced the diversity (e.g., observed species, chao1 and Shannon index) of bacterial community, shifting their structure and functions. The relative abundances of dominant phyla Proteobacteria and Firmicutes declined significantly, while those of extremophilic and heat-resisting phyla Deinococcus-Thermus and Chloroflexi increased dramatically. Some genera capable of degrading organic pollutants presented stably in sludge composts. Moreover, hyperthermophilic composting enriched the bacterial functions related to degradation and metabolism of cellulose and xenobiotics pollutants, which promoted the dissipation of organic pollutants and humification.

Evaluating the influence of raw materials on the behavior of nitrogen fractions in composting processes on an industrial scale

Success of composting as an ecological technology for organic waste management has allowed its implementation in the current circular economy models. However, composting on an industrial scale often shows drawbacks and peculiarities. In this work, a comparative analysis of 15 industrial composting facilities was carried out in which different anthropogenic organic waste were processed. Results showed that composting process on an industrial scale did not always evolve in a standard way. Monitoring parameters as well as enzymatic activity depended largely on the raw materials and were strongly linked to the transformation of nitrogen fractions. Despite the heterogeneity of the processes and raw materials, microbial activity managed to the optimal biotransformation, obtaining products that comply with the agronomic quality standards. This work represents a breakthrough in composting and provides new knowledge for better management of this process on an industrial scale.

Diversity, abundance, and persistence of antibiotic resistance genes in various types of animal manure following industrial composting

Aerobic composting is used widely for animal manure recycling, and it may reduce the amount of antibiotic resistance genes (ARGs) that enter the environment. We sampled three types of animal (bovine, chicken, and pig) manure and the corresponding composts from 12 large-scale farms, and tested multiple ARGs and mobile genetic elements (MGEs) by high-throughput qPCR. A total of 109 ARGs were detected in the manure and compost samples, thereby demonstrating that both are important ARG reservoirs. The diversity and abundance of ARGs were significantly higher in chicken and pig manure than bovine manure, but industrial composting was more efficient at reducing the ARGs in chicken manure than pig and bovine manure. Composting universally reduced some ARGs, but inconsistently influenced other ARGs from different types of animal manures. Network analysis detected the widespread co-occurrence of ARGs and MGEs. floR, ermF, catB3, aac(6')-lb(akaaacA4), and aadA were identified as suitable indicator genes for estimating the total abundance of ARGs. Our results suggest that different animal species had significant effects on the diversity, abundance, and persistence of ARGs, where the abundance of transposons, heavy metal concentration, total nitrogen level, and the dosage and duration of exposure to antibiotics may explain these differences.

Fertilizer effects of composted materials from different sources on cultivating Impatiens balsamina L. in municipal solid waste management

At different stages of municipal solid waste management, several technologies such as home composting, industrial composting, and landfill mining could be used to recycle organic matters. Assessing the quality of composted material is crucial for determining where and how for recycling the organic fractions of municipal solid waste (OFMSW). Current studies mainly focused on comparing their biochemical characteristics and environmental impacts; however, comprehensive effects on cultivating plants were rarely compared with composted materials from different sources. Here, the final composting products from home composting (HC), industrial composting (IC), and landfill mining (LM), with different mixing ratios between OFMSW and soil (25, 50, 75, and 100%), were applied for cultivating Impatiens balsamina L. to examine the growing and flowering features under 195 days of observation. We found that all types of composted materials showed positive effects on growth of impatiens; however, their individual profiles were significant different. Generally, compost from HC showed the best comprehensive effects on the plant. Impatiens' dry weight biomass and maximum number of leaves and flowers of HC were1.5 and 2.8 times, 1.1 and 1.6 times, and 1.8 and 4.2 times than those of IC and LM, respectively. Compost from IC was superior in prolonging leaf-growing phase and increasing photosynthesis pigment contents of impatiens. Although comprehensive effect of fine fraction from landfill mining was much lower than HC and IC compost, it still improved impatiens growth and flowering compared to normal sandy soil. The results suggest that direct comprehensive effect on plants growth, flowering, and physiological influences could be introduced as an indicator when we compare different approach to recycle organics from MSW. Comprehensive effect on plants growth, flowering, and physiological influences could be introduced as a direct indicator for assessing organic waste recycling.

Effects of acute NH3 air pollution on N-sensitive and N-tolerant lichen species

Lichens are sensitive to the presence of ammonia (NH3) in the environment. However, in order to use them as reliable indicators in biomonitoring studies, it is necessary to establish unequivocally the occurrence of certain symptoms following the exposure to NH3 in the environment. In this paper, we simulated an episode of acute air pollution due to the release of NH3. The biological effects of acute air pollution by atmospheric NH3 have been investigated using N-sensitive (Flavoparmelia caperata) and N-tolerant (Xanthoria parietina) species. Lichen samples were exposed to ecologically relevant NH3 concentrations for 8 weeks, simulating three areas of impact: a control area (2 μg/m(3)), an area of intermediate impact (2-35 μg/m(3)) and an area of high impact (10-315 μg/m(3)), with a peak of pollution reached between the fourth and fifth week. Ammonia affected both the photobiont and the mycobiont in F. caperata, while in X. parietina only the photosynthetic performance of the photobiont was altered after exposure to the highest concentration. In the photobiont of F. caperata we recorded chlorophyll degradation as indicated by OD435/415 ratio, decrease of the photosynthetic performance (as reflected by the maximum quantum yield of primary photochemistry FV/FM and the performance index PIABS); in the mycobiont, ergosterol reduction, membrane lipid peroxidation (as reflected by the increase of thiobarbituric acid reactive substances), alteration (decrease) of the secondary metabolite usnic acid. No effects were detected on caperatic acid and dehydrogenase activity. In X. parietina, the only signal determined by NH3 was the alteration of FV/FM and the performance index PIABS. The results suggest that physiological parameters in N-sensitive lichens well reflect the effects of NH3 exposure and can be applied as early indicators in monitoring studies.

Home composting versus industrial composting: influence of composting system on compost quality with focus on compost stability

Stability is one of the most important properties of compost obtained from the organic fraction of municipal solid wastes. This property is essential for the application of compost to land to avoid further field degradation and emissions of odors, among others. In this study, a massive characterization of compost samples from both home producers and industrial facilities is presented. Results are analyzed in terms of chemical and respiration characterizations, the latter representing the stability of the compost. Results are also analyzed in terms of statistical validation. The main conclusion from this work is that home composting, when properly conducted, can achieve excellent levels of stability, whereas industrial compost produced in the studied facilities can also present a high stability, although an important dispersion is found in these composts. The study also highlights the importance of respiration techniques to have a reliable characterization of compost quality, while the chemical characterization does not provide enough information to have a complete picture of a compost sample.