Synergistic effects of chemical additives and mature compost on reducing H2S emission during kitchen waste composting.

Additives could improve composting performance and reduce gaseous emission, but few studies have explored the synergistic of additives on H2S emission and compost maturity. This research aims to make an investigation about the effects of chemical additives and mature compost on H2S emission and compost maturity of kitchen waste composting. The results showed that additives increased the germination index value and H2S emission reduction over 15 days and the treatment with both chemical additives and mature compost achieved highest germination index value and H2S emission reduction (85%). Except for the treatment with only chemical additives, the total sulfur content increased during the kitchen waste composting. The proportion of effective sulfur was higher with the addition of chemical additives, compared with other groups. The relative abundance of H2S-formation bacterial (Desulfovibrio) was reduced and the relative abundance of bacterial (Pseudomonas and Paracoccus), which could convert sulfur-containing substances and H2S to sulfate was improved with additives. In the composting process with both chemical additives and mature compost, the relative abundance of Desulfovibrio was lowest, while the relative abundance of Pseudomonas and Paracoccus was highest. Taken together, the chemical additives and mature compost achieved H2S emission reduction by regulating the dynamics of microbial community.

The effect of biochar prepared at different pyrolysis temperatures on microbially driven conversion and retention of nitrogen during composting.

Aerobic composting is one of the most economical ways to produce organic fertilizer from agricultural wastes. In this research, we independently developed a simple composting simulation reactor. The effects of biochar pyrolysised at different pyrolysis temperatures (B1-450 °C; B2-550 °C; and B3-650 °C) on nitrogen conversion (Total nitrogen (TN), ammonium nitrogen (NH4 +-N), nitrate nitrogen (NO3 --N), cumulative amount of ammonia (CEA) and nitrous oxide (CEN) emission, nitrogen loss rate (NLR), etc.) and functional microbial community (cbbL, cbbM and nifH) structure in the composting system were studied. Results showed that the addition of biochar significantly improved the efficiency of composting, increased the NO3 --N concentration and reduced the NLR (%) in the composting system (B3 (31.4 ± 2.73)

Long-term non-phosphorus application increased paddy methane emission by promoting organic acid and methanogen abundance in Tai Lake region, China.

Rice paddy is a significant source of atmospheric methane (CH4), a major global warming source. CH4 emission from paddy fields is greatly influenced by phosphorus (P) management, especially the long-term non-P application on CH4 emission is largely unexplored. In the present study, long-term non-P application (NK) and P application (NPK) treatments of two paddy fields in Suzhou (from 1980) and Yixing (from 2009), Tai Lake region was done. The effect of P application on CH4 emissions and related microorganisms (i.e., methanogens and methanotrophs) from 2019 to 2020 was analyzed. Results revealed that long-term NK treatment didn't alter the seasonal trend of CH4 flux, but significantly promoted CH4 emissions at the tillering stage. The non-P application for >12 years caused the cumulative CH4 emissions of NK treatment in the whole rice season significantly increased by 41.9-221 % in two fields compared to NPK treatment in 2019 and 2020. NK treatment increased the abundance and diversity of methanogens, while reducing the abundance and diversity of methanotrophs. Community composition of soil pmoA gene differed in two experiment sites. Correlation analysis revealed that the CH4 emission was significant and positively related to soil mcrA gene and C/P while negatively related to soil pmoA gene and P. Structure equation model analysis show the low soil available P content was the dominant driving factor for the high CH4 emission under long-term non-P application through its direct impact on soil mcrA and pmoA genes. The increased soil organic acid content was another driver which was positively related to soil mcrA gene and negatively to soil pmoA gene. Our findings demonstrate the important role of soil P in regulating CH4 emissions from paddy fields in the Tai Lake region, China, and suitable P application is necessary for ensuring the yield while reducing CH4 emission.

Synergetic Enhancement of Pb2+ and Zn2+ Adsorption onto Size-Selective Sludge Biochar Portions in Multiple Ion Solution Systems.

Particle size, one of the predominant factors that affect the adsorption capacity of biochar, has been widely investigated. However, correlative studies on a coexistence system containing various ions together with differentiated particle sizes are scarce. In this study, samples of municipal solid waste (sludge) biochar (SB) with different particle sizes were separated and examined for the adsorption performance in bi-cation (Pb2+/Zn2+) and multi-ion (Pb2+, Zn2+ and Cl-) systems. The results showed that the adsorption capacity is influenced by both particle size and ion configurations. The effective stabilization ability of a small size group can be attributed to the most non-bioavailable fraction. Meanwhile, the acidic soluble and non-bioavailable fraction of Pb2+/Zn2+ reached more than 90%. The mixed adsorption experiment showed that Pb2+ would compete for the adsorption sites of biochar with Zn2+, and Cl- intervention could improve the adsorption of Pb2+ (2.33-6.93%) and Zn2+ (16.52-18.01%) on biochar. Further, X-ray diffraction spectra and phosphorus concentration dynamics and kinetics simulations revealed that more abundant active sites in the formatted pyromorphite were able to be exposed in the presence of Cl-. The small-size portion of SB therefore exhibited excellent potential for the long-term heavy metal remediation under practical conditions of multi-ion systems in an actual environment.

Using Ipomoea aquatic as an environmental-friendly alternative to Elodea nuttallii for the aquaculture of Chinese mitten crab.

Elodea nuttallii is widely used in Chinese mitten crab (CMC) rearing practice, but it is not a native aquatic plant and cannot endure high temperature. Thus, large E. nuttallii mortality and water deterioration events could occur during high-temperature seasons. The aim of this study was to identify the use of local macrophytes in CMC rearing practice, including Ipomoea aquatic and Oryza sativa. A completely randomized field experiment was conducted to investigate the crab yield, water quality, bacterioplankton community and functions in the three different systems (E. nuttallii, I. aquatic, and O. sativa). Average crab yields in the different macrophyte systems did not differ significantly. The I. aquatic and O. sativa systems significantly decreased the total nitrogen and nitrate-N quantities in the outflow waters during the rearing period compared to the E. nuttallii system, and the I. aquatic and O. sativa plants assimilated more nitrogen than the E. nuttallii plant. Moreover, the significant changes of bacterioplankton abundances and biodiversity in the three systems implied that cleanliness of rearing waters was concomitantly attributed to the differential microbial community and functions. In addition, principle component analysis successfully differentiated the bacterioplankton communities of the three macrophytes systems. Environmental factor fitting and the co-occurrence network analyses indicated that pH was the driver of bacterioplankton community structure. Functional predictions using PICRUSt (v.1.1.3) software based on evolutionary modeling indicated a higher potential for microbial denitrification in the I. aquatic and O. sativa systems. Notably, the O. sativa plants stopped growing in the middle of the rearing period. Thus, the I. aquatic system rather than the O. sativa system could be a feasible and environmental-friendly alternative to the E. nuttallii system in CMC rearing practice.