Flare exhaust: An underestimated pollution source in municipal solid waste landfills.

Flares are commonly used in municipal solid waste landfills, and the pollution from flare exhaust is usually underestimated. This study aimed to reveal the odorants, hazardous pollutants, and greenhouse gas emission characteristics of the flare exhaust. Odorants, hazardous pollutants, and greenhouse gases emitted from air-assisted flares and a diffusion flare were analyzed, the priority monitoring pollutants were identified, and the combustion and odorant removal efficiencies of the flares were estimated. The concentrations of most odorants and the sum of odor activity values decreased significantly after combustion, but the odor concentration could still exceed 2,000. The odorants in the flare exhaust were dominated by oxygenated volatile organic compounds (OVOCs), while the major odor contributors were OVOCs and sulfur compounds. Hazardous pollutants, including carcinogens, acute toxic pollutants, endocrine disrupting chemicals, and ozone precursors with the total ozone formation potential up to 75 ppmv, as well as greenhouse gases (methane and nitrous oxide with maximum concentrations of 4,000 and 1.9 ppmv, respectively) were emitted from the flares. Additionally, secondary pollutants, such as acetaldehyde and benzene, were formed during combustion. The combustion performance of the flares varied with landfill gas composition and flare design. The combustion and pollutant removal efficiencies could be lower than 90%, especially for the diffusion flare. Acetaldehyde, benzene, toluene, p-cymene, limonene, hydrogen sulfide, and methane could be priority monitoring pollutants for flare emissions in landfills. Flares are useful for odor and greenhouse gas control in landfills, but they are also potential sources of odor, hazardous pollutants, and greenhouse gases.

Gut microbiome alterations in ICU patients with enteral nutrition-related diarrhea.

Enteral Nutrition-related Diarrhea (END) is an extremely common complication in Intensive Care Unit (ICU) patients. However, it is currently unclear whether the patient's gut microbiota is disturbed. Our study aimed to explore the characteristics of gut microbiota changes in END patients. We divided ICU patients into no-END group (n = 7) and END group (n = 7) according to whether they had END, then stool samples were collected separately. The V3-V4 region of stool bacterial 16S rRNA gene was amplified by PCR and sequenced on an Illumina MiSeq PE300 platform. Microbiome data obtained by quality control were analyzed, including microbial community composition, diversity and gene function prediction.The results showed that the dominant gut microbiota in ICU patients who were given total enteral nutrition were Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, and Verrucomicrobia. Bacterial richness and diversity in END patients were all significantly lower than those in no-END patients. In addition, END caused significant changes in bacterial composition. LEfSe found 34 biomarkers represented by Bacteroidetes and Subdoligranulum in the no-END group as well as 11 biomarkers represented by Enterococcus and Klebsiella in the END group. Finally, through PICRUST function prediction, we found that diarrhea led to abnormal changes in numerous KEGG pathways mainly related to immunity and metabolism. In short, ICU patients with END have severe gut dysbiosis, and our study provides a reliable experimental basis for the patient's microbiota therapy.

Efficiency, by-product valorization, and pollution control of co-pyrolysis of textile dyeing sludge and waste solid adsorbents: Their atmosphere, temperature, and blend ratio dependencies.

This study aimed to quantify the co-pyrolytic synergistic effects of textile dyeing sludge (TDS) and waste biochar (WBC) for an optimal utilization of secondary resources and to mitigate environmental pollution and waste volume. TDS and WBC had a strong synergistic effect between 800 and 900 °C in the CO2-assisted atmosphere. With the increased TDS fraction, NH3 emission fell significantly regardless of the atmosphere type. The CO2 atmosphere changed S in TDS char and released SO2 in the range of 800-1000 °C. With the temperature rise, an unstable N structure turned into a more stable heterocyclic N structure in the CO2 and N2 atmospheres. Regardless of the atmosphere type and temperature, the C-containing functional groups in co-pyrolytic biochar existed mainly as C-C/C-H. In the CO2 atmosphere, inorganic S, aliphatic S, and thiophene S in the co-pyrolytic biochar disappeared and became more stable sulfones. The co-pyrolysis inhibited the formation of S-containing compounds. The retention ability of the co-pyrolytic biochar peaked for most of the heavy metals in the N2 atmosphere but was better for Pb and Zn in the CO2 than N2 atmosphere. Simultaneous optimization showed the co-pyrolysis of 10% TDS and 90% WBC at above 950 °C in the N2-CO2 or CO2 atmosphere as the optimal operational settings combined.

Do FeCl3 and FeCl3/CaO conditioners change pyrolysis and incineration performances, emissions, and elemental fates of textile dyeing sludge?

The pyrolysis and incineration performances of sulfur-rich textile dyeing sludge (TDSS) were determined in response to the additions of FeCl3 or FeCl3 + CaO. The emissions of eight air pollutants from the incineration and pyrolysis were systematically identified. The 3-to-8% FeCl3 additions increased the comprehensive combustibility index by 2.14 and 1.62 times, respectively, as opposed to the 5-to-10% FeCl3 + 8-to-15% CaO additions. The CaO addition inhibited the TDSS incineration, while the FeCl3 addition increased HCl emission. NOx, SO2, and H2S emissions decreased initially and increased between 600 and 950 °C. SO2 and NOx emissions rose with FeCl3 but FeCl3 + CaO. FeCl3 catalyzed NOx, while CaO retained SO2. The main pyrolysis gas/liquid products were alkane, alkenes, nitrile, heterocyclic compounds, benzene, and its derivatives. Benzene and its derivatives accounted for 55.33% of the control group and 42.25-57.23% of the treatment groups. The FeCl3 and FeCl3 + CaO additions did not significantly influence the pyrolysis products. The measured versus thermodynamically simulated SOx and HCl emissions were consistent. Neural network-based simultaneous optimizations of the non-linear dynamics of eight kinds of gases pointed to 50% and 14.4% reductions in the emissions and the pyrolytic temperature, respectively, with the 3% FeCl3, relative to the control.

Comparative (co-)pyrolytic performances and by-products of textile dyeing sludge and cattle manure: Deeper insights from Py-GC/MS, TG-FTIR, 2D-COS and PCA analyses.

Not only does pyrolysis recover energy and value-added by-products but also reduces waste stream volume. The low volatiles and high ash contents of textile dyeing sludge (TDS) limit its mono-pyrolysis performance. This study aimed to conduct an in-depth analysis of its co-pyrolytic performance with cattle manure (CM). The co-pyrolysis enhanced the volatiles emission from the early devolatilization stage whose reaction mechanism shifted from a diffusion model to a reaction-order model. The further cracking of macromolecular materials was mainly elucidated by the reaction-order model. The temperature dependency of the co-pyrolytic gases was of the following order: aliphatic hydrocarbons > CO2 > alcohols, phenols, ethers, aldehydes, ketones, and carboxylic acids. The main co-pyrolytic volatile products were coumaran and 4-vinylguaiacol. The relative content of guaiacol-type components could be enhanced by co-pyrolysis and lowering the operational temperature to 450 °C. The interaction of co-pyrolysis enriched the char aromaticity. Our findings provide practical insights into the control and application opportunities and limitations on the high value-added energy and products from the co-pyrolysis of TDS and CM.

Multi-response optimization toward efficient and clean (co-)combustions of textile dyeing sludge and second-generation feedstock.

The rapid growth of textile dyeing sludge (TDS) necessitates feeding it back into a circular economy in an efficient and clean way. This study aimed to optimize the clean and efficient operational conditions to co-combust TDS and incense sticks (IS). The (co-)-combustions exhibited four distinctive stages of thermal degradation. According to the master-plots method, the reaction mechanisms of reaction order (F2.4 and F1.5), three-dimensional diffusion (D3), and nucleation growth (A1.5) best explained the four stages, respectively. The interaction between TDS and IS exerted an inhibition effect in the range of 400-500 °C and a facilitation effect in the range of 600-1000 °C. At 300 °C as the main reaction temperature, the main evolved gas and functional groups such as CO2, H2O, CH4, CË­O, C-O, and C-H were detected. The addition of IS improved the comprehensive combustion index, inhibited SO2, but enhanced CO2, HCN, and NOx emissions. CaO in IS enabled Fe to remain in TDS and fixed more S in ash. Multi-response optimizations based on the best-fit artificial neural networks revealed the range of 545-605 °C and the co-combustion of 25% TDS and 75% IS as the cleaner and more efficient operational conditions.

Catalytic combustion performances, kinetics, reaction mechanisms and gas emissions of Lentinus edodes.

This study aimed to quantify the catalytic effects of CaO, Fe2O3, and their blend on the Lentinus edodes stipe (LES) and pileus (LEP) combustion performances, kinetics and emissions in bioenergy generation. Apparent activation energy (Ea) of LES and LEP increased with CaO, decreased with Fe2O3 and differed with their blend. The catalysts mainly affected the maximum intensity of volatiles combustion and partly the fixed carbon combustion. CaO, Fe2O3, and their blend decreased the release intensity of NOx from the LES combustion. Fe2O3 increased SO2 emission, while CaO, and the blend narrowed the emission temperature to the range of 200 to 450 °C. Kinetic triplets were estimated via the integral master-plots methods, and the best-fit reaction for the three sub-stages were obtained coupled with the model-free models. Our study provides a reference for the catalyzed biomass combustion in terms of pollution control, bioenergy generation, optimal design of incinerator, and industrial-scale application.

Combustion behaviors of pileus and stipe parts of Lentinus edodes using thermogravimetric-mass spectrometry and Fourier transform infrared spectroscopy analyses: Thermal conversion, kinetic, thermodynamic, gas emission and optimization analyses.

The combustion behaviors of both Lentinula edodes pileus (LEP) and stipe (LES) were characterized in response to four heating rates in the air atmosphere using thermogravimetric (TG)-mass spectrometry and TG-Fourier transform infrared spectroscopy analyses. There were two and three main peaks of the derivative TG curves for LEP and LES, respectively, with their main combustion stage occurring between 130 and 620 °C. Four iso-conversional models were compared to estimate activation energy values of their combustions. The main emission peaks of most gases ranged from 200 to 350 °C and from 500 to 600 °C for LEP and LES. Their comprehensive combustion parameters at 20 K/min (1.53 and 2.40 × 10-6 %2/(min2·K3) for LEP and LES, respectively) as well as joint optimizations confirmed their great potential for bioenergy generation. The waste stream of LEP and LES could be well disposed through their combustions with a low level of air pollution.

Thermal degradations and processes of waste tea and tea leaves via TG-FTIR: Combustion performances, kinetics, thermodynamics, products and optimization.

The present study characterized the kinetic, thermodynamic and performance parameters, products, factorial interactions, and optimal conditions of combustions of waste tea (WT) and tea leaves (TL) in N2/O2 and CO2/O2 atmospheres through a thermogravimetric/Fourier transform infrared spectrometry (TG-FTIR). The main combustion occurred in the range of 200-600 °C. The increased heating rate increased all the combustion parameters regardless of the fuel and atmosphere type. Activation energy was shown different change tendency with the increasing conversion (α). CO2, H2O, CH4, CO, CO, NH3, and HCN were the main gas products of WT and TL combustions. A three-way interaction among fuel type, atmosphere type and heating rate was found to be significant. The joint optimization of mass loss, derivative TG, and differential scanning calorimetry was achieved using 1049.3 °C, TL, 40 °C/min, and CO2/O2 atmosphere for the operational settings of temperature, fuel type, heating rate, and atmosphere type, respectively.