Meijing Wang

Heterogeneity of biochar amendment to improve the carbon and nitrogen sequestration through reduce the greenhouse gases emissions during sewage sludge composting

This study was performed to investigate the effects of biochar as an amendment to a gaseous emissions and sewage sludge (SS) composting dynamics. Six dosage of biochar [low dosage of biochar (LDB) - 2%, 4% and 6%; and higher dosage of biochar (HDB) - 8%, 12% and 18%] were amended to a mixture of SS and wheat straw (4:1 ratio on dry weight basis) and compared to control or without additive. The HDB significantly reduced CH4, N2O and NH3 emission by 92.85-95.34%, 95.14-97.30% and 58.03-65.17%, but not the CO2 emission. Meanwhile, humification results indicated that humic and fulvic acid 35-42% and 24-28% higher in the HDB amended treatments than those in the LDB and control treatments. The HDB significantly decreased total nitrogen losses and greenhouse gas emission, while LDB had significantly (p<0.001) higher CH4 and N2O emissions. Due to effective performance of HDB, the 12% biochar was recommended to be used in SS composting practice.

Evaluation of medical stone amendment for the reduction of nitrogen loss and bioavailability of heavy metals during pig manure composting

The purpose of this research was to evaluate the effect of medical stone (MS) on nitrogen conservation and improving the compost quality during the pig manure (PM) composting. Five treatments were designed with different concentrations of MS0%, 2.5%, 5%, 7.5% and 10% (on dry weight of pig manure basis) mixed with initial feed stock and then composted for 60days. The results showed that MS amendment obviously (p<0.05) promoted the organic waste degradation and prolonged the thermophilic phase as well as enhanced the immobilization of heavy metals Cu and Zn. With increasing the amount of MS, the NH3 loss and N2O emission were significantly reduced by 27.9-48.8% and by 46.6-85.3%, respectively. Meanwhile, the MS amendment could reduce the NO2(-)-N formation and increase the NO3(-)-N content. Finally our results suggested that 10%MS addition could significantly reduce the nitrogen conservation as well as improve the quality of compost.

Evaluation of biochar amended biosolids co-composting to improve the nutrient transformation and its correlation as a function for the production of nutrient-rich compost

The influence of biochar amended dewatered fresh sewage sludge (DFSS)-wheat straw co-composting on nutrients transformation and end products quality was investigated. This is the first study to examine the biochar applied compost quality with different kgha-1 TKN on Brassica rapa L. growth. Seven mixtures were composted over 8-weeks period in 130-L reactor using the same DFSS with different concentration of biochar (2%, 4%, 6%, 8%, 12% and 18% on dry weight basis) and without additive added treatment served as control. The results indicated that compost with 8-12% biochar became more humified within 35days of composting, and the compost maturity parameters also showed that this could be much more feasible approach to increased water-soluble nutrients including NO3, DOC, DON, PO43-, K+ and Na+, but bioavailability of Cu, Zn, Ni and Pb content reduced as compared to control. Finally, results showed that 8-12% biochar was recommended for DFSS composting and 150kgha-1 TKN of compost dosages for organic farming.

New insight with the effects of biochar amendment on bacterial diversity as indicators of biomarkers support the thermophilic phase during sewage sludge composting

In this work, the 16S rRNA gene was used to compare the bacterial diversity at thermophilic stage of six different biochar dosage applied SS composting, while compared without biochar added treatment or control. The results showed that biochar amendment affected the structure and succession of bacteria diversity in different ways, and there were 35 prominent genera among all samples displayed in the species abundance heat-map. Among them, Proteobacteria, Firmicutes and Chloroflexi were the main phyla found in genomic libraries from each treatment. The most abundant common genera among the all treatments were Pseudomonas, T78, Acinetobacter and Ureibacillus. In addition, Krona, principal component analysis and β-diversity indices showed a clear difference in bacterial diversity among the biochar added and control treatments. Finally, our results suggested that Planomicrobium, Paracoccus, Agrobacterium and Devosia could be considered as possible biomarkers symbolic of the thermophilic phase during SS composting.

Heterogeneity of zeolite combined with biochar properties as a function of sewage sludge composting and production of nutrient-rich compost

In the present study, biochar combined with a higher dosage of zeolite (Z) and biochar (B) alone were applied as additives for dewatered fresh sewage sludge (DFSS) composting using 130-L working volume lab-scale reactors. We first observed that the addition of a mixture of B and Z to DFSS equivalent to 12%B+10% (Z-1), 15% (Z-2) and 30% (Z-3) zeolite (dry weight basis) worked synergistically as an amendment and increased the composting efficiency compared with a treatment of 12%B alone amended and a control without any amendment. In a composting reactor, the addition of B+Z may serve as a novel approach for improving DFSS composting and the quality of the end product in terms of the temperature, water-holding capacity, CO2 emissions, electrical conductivity, water-soluble and total macro-nutrient content and phytotoxicity. The results indicated that during the thermophilic phase, dissolved organic carbon, NH4+-N and NO3--N increased drastically in all biochar amended treatments, whereas considerably low water-soluble nutrients were observed in the control treatment throughout and at the end of the composting. Furthermore, the maturity parameters and dissolved organic carbon (DOC) indicated that compost with 12%B+15%Z became more mature and humified within 35days of DFSS composting, with the maturity parameters, such as CO2 evolution and the concentration of NH4+-N in the compost, being within the permissible limits of organic farming in contrast to the control. Furthermore, at the end of composting, the addition of higher dosage of biochar (12%) alone and 12% B+Z lowered the pH by 7.15 to 7.86 and the electrical conductivity by 2.65 to 2.95mScm-1 as compared to the control, while increased the concentrations of water-soluble nutrients (gkg-1) including available phosphorus, sodium and potassium. In addition, greenhouse experiments demonstrated that the treatment of 150kgha-1 biochar combined with zeolite and that of 12%B alone improved the yield of Chinese cabbage (Brassica rapa chinensis L.). The highest dry weight biomass (1.41±0.12g/pot) was obtained with 12%B+15%Z amended compost. Therefore, 12%B+15%Z can be potentially applied as an amendment to improve DFSS composting.

Comparison of additives amendment for mitigation of greenhouse gases and ammonia emission during sewage sludge co-composting based on correlation analysis

In this study, the pilot scale co-composting of sewage sludge (SS)+wheat straw amended with 10% (dry weight ratio of basis) of three different additives (zeolite, Ca-bentonite and medical stone) was conducted for 56days to evaluate the greenhouse gases (GHGs) and nitrogen conservation efficacy and its correlation with analyzed physicochemical, gaseous and biological parameters. The results indicated that all of three additives could adequately buffer pH, considerably increase temperature, and enhance organic matter degradation as well as reduce ammonia and GHGs emission. Particularly, zeolite amended treatment showed the maximum reduction of CH4 emission by 88.45% and less amount of nitrogen loss by 28.80%, meanwhile reduced the maturity period by 2weeks. In addition, the redundancy analysis was confirmed most significant relationship between biological, GHGs, bacterial community and nutrients concentration in 10% zeolite applied treatment than other treatments. The result suggested 10% zeolite could be a suitable additive to improve the quality of sewage sludge composting.

Influence of medical stone amendment on gaseous emissions, microbial biomass and abundance of ammonia oxidizing bacteria genes during biosolids composting

This study aimed to evaluate the feasibility of medical stone (MS) on microbial biomass, bacteria genes copy numbers, mitigation of gaseous emissions and its correlation with analyzed parameters during the biosolids composting. Composting of the biosolids by amendment of MS 0%, 2%, 4%, 6% and 10% (on dry weight basis) was performed using a 130-L composting reactor. The results showed that with increasing the dosage of MS, the CH4, N2O and NH3 emission were reduced by 60.5-88.3%, 46.6-82.4% and 38.2-78.5%, respectively. In addition, the 6-10% MS amendment enhanced the organic waste mineralization and prolonged the thermophilic phase. The abundance of ammonia oxidizing bacteria (AOB) and archaea (AOAB) were decreased during the first 28 days, but considerable increment was observed during the maturation phase which indicated that AOB and AOAB were liable for nitrification during the curing phase of composting. A significant correlation was observed among the all analyzed parameters in 6-10% MS blended treatments.

Improvement of pig manure compost lignocellulose degradation, organic matter humification and compost quality with medical stone

The present study aimed to investigate the effect of different concentrations (0%, 2.5%, 5.0%, 7.5% and 10.0%) of medical stone (MS) on the lignocellulose degradation and organic matter humification during pig manure (PM) composting. The results indicated that the addition of MS drastically promoted the organic carbon and lignin degradation. Compared to the control, the decomposition rate of hemicellulose and cellulose was increased by 9.64-27.08% and 2.11-12.07% in MS added treatments. Meanwhile, MS amendment significantly improved the humification of composting process, and the humic acid contents in MS added treatments were 5.58-9.75% higher than control. The FTIR and synchronous fluorescence spectra indicated that the aromatization of final compost was promoted with increasing the MS amount. In addition, the application of MS blended composts could significantly improve the biomass and chlorophyll content of pachoi (Brassica chinensis L.). Due to the effective performance of MS, the 10.0% MS was suggested for PM composting.

Combining biochar, zeolite and wood vinegar for composting of pig manure: The effect on greenhouse gas emission and nitrogen conservation

The effect of enhancing wood vinegar (WV) with a mixture of biochar (B) and zeolite (Z) to compost pig manure (PM) in a 130 L reactor was evaluated to determine the levels of greenhouse gas (GHG) and ammonia emissions. Six treatments were prepared in a 2:1 ratio of PM mixed with wheat straw (WS; dry weight basis): PM + WS (control), PM + WS + 10%B, PM + WS + 10%B + 10%Z, and PM + WS with 0.5%, 1.0% and 2.0%WV combined with 10%B + 10%Z. These were composted for 50 days, and the results indicated that the combined use of B, Z, and WV could shorten the thermophilic phase and improve the maturity of compost compared to the control treatment. In addition, WV mixed with B and Z could reduce ammonia loss by 64.45-74.32% and decrease CO2, CH4, and N2O emissions by 33.90-46.98%, 50.39-61.15%, and 79.51-81.10%, respectively. Furthermore, compared to treatments in which B and B + Z were added, adding WV was more efficient to reduce the nitrogen and carbon loss, and the 10%B + 10%Z + 2%WV treatment presented the lowest loss of carbon (9.16%) and nitrogen (0.75%). Based on the maturity indexes used, nitrogen conservation, and efficiency of GHG emissions reduction, the treatment 10%B + 10%Z + 2%WV is suggested for efficient PM composting.

Biodegradation of food waste using microbial cultures producing thermostable α-amylase and cellulase under different pH and temperature

The aim of this work was to study the biodegradation of food waste employing thermostable α-amylase and cellulase enzymes producing bacteria. Four potential isolates were identified which were capable of producing maximum amylase and cellulase and belong to the amylolytic strains, Brevibacillus borstelensis and Bacillus licheniformis; cellulolytic strains, Bacillus thuringiensis and Bacillus licheniformis, respectively. These strains were selected based on its higher cell density, enzymatic activities and stability at a wide range of pH and temperature compared to other strains. The results indicated that 1:1 ratio of pre and post consumed food wastes (FWs) were helpful to facilitate the degradation employing bacterial consortium. In addition, organic matter decomposition and chemical parameters of the end product quality also indicated that bacterial consortium was very effective for 1:1 ratio of FWs degradation as compared to the other treatments.