Removal of artificial sweeteners in wastewater treatment plants and their degradation during sewage sludge composting with micro- and nano-sized kaolin.

This study surveyed the fates of artificial sweeteners in influent, effluent, and sewage sludge (SS) in wastewater treatment plant, and investigated the effects of Micro-Kaolin (Micro-KL) and Nano-Kaolin (Nano-KL) on nitrogen transformation and sucralose (SUC) and acesulfame (ACE) degradation during SS composting. Results showed the cumulative rate of ACE and SUC in SS was ∼76 %. During SS composting, kaolin reduced NH3 emissions by 30.2-45.38 %, and N2O emissions by 38.4-38.9 %, while the Micro-KL and Nano-KL reduced nitrogen losses by 14.8 % and 12.5 %, respectively. Meanwhile, Micro-KL and Nano-KL increased ACE degradation by 76.8 % and 84.2 %, and SUC degradation by 75.3 % and 77.7 %, and significantly shifted microbial community structure. Furthermore, kaolin caused a positive association between Actinobacteria and sweetener degradation. Taken together, kaolin effectively inhibited nitrogen loss and promoted the degradation of ACE and SUC during the SS composting, which is of great significance for the removal of emerging organic pollutants in SS.

Enhancing C and N turnover, functional bacteria abundance, and the efficiency of biowaste conversion using Streptomyces-Bacillus inoculation.

Microbial inoculation plays a significant role in promoting the efficiency of biowaste conversion. This study investigates the function of Streptomyces-Bacillus Inoculants (SBI) on carbon (C) and nitrogen (N) conversion, and microbial dynamics, during cow manure (10% and 20% addition) and corn straw co-composting. Compared to inoculant-free controls, inoculant application accelerated the compost's thermophilic stage (8 vs 15 days), and significantly increased compost total N contents (+47%) and N-reductase activities (nitrate reductase: +60%; nitrite reductase: +219%). Both bacterial and fungal community succession were significantly affected by DOC, urease, and NH4+-N, while the fungal community was also significantly affected by cellulase. The contribution rate of Cupriavidus to the physicochemical factors of compost was as high as 83.40%, but by contrast there were no significantly different contributions (∼60%) among the top 20 fungal genera. Application of SBI induced significant correlations between bacteria, compost C/N ratio, and catalase enzymes, indicative of compost maturation. We recommend SBI as a promising bio-composting additive to accelerate C and N turnover and high-quality biowaste maturation. SBI boosts organic cycling by transforming biowastes into bio-fertilizers efficiently. This highlights the potential for SBI application to improve plant growth and soil quality in multiple contexts.

[Effects of Vermicomposting on Compost Quality and Heavy Metals：A Meta-analysis].

In order to comprehensively evaluate the effects of vermicomposting on compost quality and the conversion of heavy metals under different control conditions, 109 studies were reviewed. The effects of earthworm species, pre-compost time, ventilation methods, initial C/N, initial pH, and initial moisture of the raw materials on compost quality and the heavy metal toxicity were quantitatively discussed during the vermicomposting process through Meta-analysis. The results showed that the six subgroups of factors all showed obvious influences on the compost quality and heavy metal toxicity. After vermicomposting, the contents of NO3--N (116.2%), TN (29.1%), TP (31.2%), and TK (15.0%) were significantly increased, whereas NH4+-N (-14.8%) and C/N (-36.3%) were significantly decreased. Meanwhile, the total amount of Cu and Cr of the final compost and their bioavailability were significantly reduced. Considering the influences of grouping factors on compost quality and heavy metals, it is recommended to adjust the initial moisture of pile materials to 70%-80%, C/N to 30-85, and pH to 6-7 and to conduct pre-composting for 0-15 d; additionally, vermicomposting should be naturally placed when the composting is aimed at promoting the compost quality. If the main purpose is to weaken the perniciousness of heavy metals in the raw material, it is recommended to adjust the initial moisture of the material to 50%-60%, C/N to less than 30, and pH to 7-8; to conduct no pre-compost; regularly turn the piles; and use the earthworm Eudrilus eugeniae for vermicomposting.

Occurrences of typical PPCPs during wastewater treatment and the composting of sewage sludge with micron-sized and nano-sized Fe3O4.

New pollutants, pharmaceuticals and personal care products (PPCPs), accumulate in sewage sludge (SS) in wastewater treatment plants (WWTPs), posing risks to the environment and to human health. In the present study, the fates of typical PPCPs, carbamazepine (CBZ), triclosan (TCS), ibuprofen (IBU) and galaxolide (HHCB), were examined during WW treatment. Additionally, SS collected from a WWTP was used for aerobic composting to investigate the influences of micron-sized Fe3O4 (M-Fe) and nano-sized Fe3O4 (N-Fe) on the degradation of these PPCPs and the succession of microbial communities during the composting process. The results showed that the mean concentrations of CBZ, TCS, IBU and HHCB in the influent of the WWTP were 926.5, 174.4, 8869, and 967.3 ng/g, respectively, and in the effluent were 107.6, 47.0, 283.4, and 88.4 ng/g, respectively. The removal rate averaged ∼80%, while the enrichment rates of the PPCPs in SS ranged from 37.2% to 60.5%. M-Fe and N-Fe reduced NH3 emissions by 32.9% and 54.1% and N2O emissions by 26.2% and 50.8%, respectively. Moreover, the addition of M-Fe and N-Fe effectively increased PPCP degradation rates 1.12-1.66-fold. During the whole process, the additions of M-Fe and N-Fe significantly shifted microbial community structure, and the abundances of Proteobacteria, Chloroflexi, and Actinobacteria were increased during the thermophilic stage, marking them as key PPCP-degrading phyla. Taken together, our results indicated that the addition of M-Fe and N-Fe is an effective method for improving the quality of end compost and accelerating the degradation of PPCPs.

Sludge disintegration and phosphorus migration in anaerobic fermentation of waste activated sludge by the addition of EDTA-2Na.

The effects of the addition of EDTA-2Na on sludge disintegration and phosphorus (P) migration during anaerobic fermentation (AF) of waste activated sludge (WAS) are investigated. The efficiency of sludge disintegration was positively correlated with the dose of EDTA-2Na from 0.5-2.0 g/g SS, and an enormous quantity of P was liberated into the aqueous phase, accompanied by sludge disintegration. The proper dose of EDTA-2Na for P release from WAS was 1.5 g/g SS, with an orthophosphate concentration of 394.72 mg/L. P release was more consistent with the pseudo second-order kinetic model. The migration of P species during AF with EDTA-2Na addition was also studied. Orthophosphate was the main species in both of the liquid phase and the loosely bound extracellular polymeric substances (EPS), but organic P (OP) was much more abundant in tightly bound EPS. Inorganic P (IP) was the dominant P speciation in the solid and was mainly distributed in the fraction of non-apatite IP, which accounted for more than 62.8% of IP in the presence of EDTA-2Na. In addition, both IP and OP in the solid contributed to the accumulation of P and the former was outperformed. Furthermore, the increased total dissolved P mainly came from cells. However, the fermented sludge tended to be smaller and to have low compressibility, which is detrimental to its further treatment.

Effect of potassium persulphate addition on sludge disintegration of a mesophilic anaerobic fermentation system.

Persulphates, an advanced oxidation process, has been recently used as an alternative pretreatment method to enhance short-chain fatty acids (SCFAs) yield from waste-activated sludge (WAS) anaerobic fermentation (AF). But so far, the effects of peroxydisulphate (PDS) dosages on mesophilic anaerobic fermentation are still not studied fully. Herein, we explored the influences of potassium PDS addition on mesophilic AF of WAS. Notably, the addition of PDS could drastically accelerate WAS solubilization and hydrolysis, which was proportional to the amount of PDS. The maximal total SCFAs yield of 249.14 mg chemical oxygen demand/L was obtained with 120 mg PDS/g suspended solids addition at 6 days of AF, which was 2.2-fold that of the control one. Tightly bound extracellular polymeric substances (EPSs) were transformed into loosely bound EPS and dissolved organic matters, and aromatic proteins and humic-like substances of EPSs were disintegrated, which were caused by the devastating effects of PDS treatments on EPSs disruption. The intracellular constituents of microbial cells in the sludge were released accordingly. As a result, there was release of soluble substrates derived from the disintegration of both EPSs and cells, the amounts of which were proportional to the dose of PDS. Moreover, microbial diversity and richness were both decreased in the presence of PDS, and the relative abundance of phyla Actinobacteria increased with the increase of the PDS dosage. In addition, the stability of sludge flocs was destroyed in the presence of PDS, the distribution of particle size tended to be small and dispersive, and dewaterability of the sludge was deteriorated.

Combined addition of biochar and garbage enzyme improving the humification and succession of fungal community during sewage sludge composting.

The influences of combination of garbage enzyme and biochar on total organic carbon (TOC) degradation, humification and the fungal succession during sewage sludge (SS) composting were established. Results showed that the GE and BC + GE treatments significantly increased the enzyme activity of fluorescein diacetate hydrolase (FDA) and increased the TOC degradation rate by 9.8% and 21.9% relative to control. The excitation-emission matrix (EEM) combined with the percentage fluorescence response (Pi, n) also proved that the combination of BC and GE promoted fulvic acid-like and humic-like substances production, and thus increased humification. Furthermore, the combination of BC and GE effectively decreased the relative abundance of Unclassified_k_Fugni, while increased the abundance of Ascomycota and Basidiomycota compared with control. The four genera, Pseudeurotium, Talaromyces, Trichoderma, and Penicillium, were the main fungi for the humification. Comparatively, the combined of BC and GE showed the optimal performance for TOC degradation and humification during SS composting.

Enhancements of short-chain fatty acids production via anaerobic fermentation of waste activated sludge by the combined use of persulfate and micron-sized magnetite.

The combination of persulfate (PDS) with micron-sized magnetite (Fe3O4) was introduced into the process of anaerobic fermentation (AF) to scrutinize the short chain fatty acid (SCFA) production from waste activated sludge for the first time. The synergetic effect of PDS and Fe3O4 results in the promotion of intracellular and extracellular substance liberation, augment in key hydrolases activities, and enrichment of hydrolytic and acidifying microbial population. Meanwhile, carbohydrate, amino acid, and energy metabolism as well as enzymes, are considerably accelerated. Consequently, the maximum SCFAs yield is significantly enhanced to 391.25 mg COD/L on day 8 of AF with the addition of 0.3 g Fe3O4/g SS and 0.5 g PDS/g SS, which was 2.39-folds than that of the control. The relative abundance of Actinobacteria were highly enriched and reached to 35.76% at the class level. This work affords an effective avenue to evidently boost the production of SCFAs from WAS via AF.

Comparative evaluation of biochar, pelelith, and garbage enzyme on nitrogenase and nitrogen-fixing bacteria during the composting of sewage sludge.

This study investigated the effects of garbage enzyme (GE), pelelith (PL), and biochar (BC) on nitrogen (N) conservation, nitrogenase (Nase) and N-fixing bacteria during the composting of sewage sludge. Results showed that the addition of GE, PL, and BC reduced NH3 emissions by 40.9%, 29.3%, and 67.4%, and increased the NO3-N contents of the end compost by 161.4, 88.2, and 105.8% relative to control, respectively, thus increasing the TN content. Three additives improved Nase, cellulase, and fluorescein diacetate hydrolase (FDA) activities and the abundances of nifH gene, and the largest increase was BC, followed by PL and GE. In addition, the additives also markedly influenced the succession of N-fixing bacteria, and significantly increased the abundance of Proteobacteria during the whole process. The BC and PL additions strengthened the sensitivity of N-fixing bacteria to environmental variables, and FDA, TN, moisture content, and NO3-N significantly affected the N-fixing bacteria at genus level.

Garbage enzymes effectively regulated the succession of enzymatic activities and the bacterial community during sewage sludge composting.

This study evaluated nitrogen transformation, enzymatic activities and bacterial succession during sewage sludge composting with and without garbage enzymes (GE and CK, respectively). The results showed that GE addition significantly increased fluorescein diacetate hydrolase (FDA), cellulase, and nitrogenase activities during the composting process. GE addition reduced the cumulative NH3 emissions by 66.5%, increased the peak NH4-N content by 26.3% and increased the total nitrogen (TN) content of the end compost by 39.2% compared to CK. Microbiological analysis revealed that GE addition significantly increased the relative abundance of Firmicutes during the thermophilic and cooling phases relative to CK. The selected factors affected the bacterial community composition in the following order: NH4-N > TOC > FDA > TN > C/N. Network analysis also showed that the enzymes were secreted mainly by Bacillus and norank_f_Caldilineaceae in GE, while they were secreted primarily by norank_f_Methylococcaceae in CK during the composting process.

Effects of urease inhibitors on enzymatic activities and fungal communities during the biosolids composting.

This study evaluated the influences of urease inhibitors (UIs) on nitrogen conversion, enzyme activities, and fungal communities during aerobic composting. Results showed that UI addition reduced NH3 emissions by 22.2% and 21.5% and increased the total nitrogen (TN) content by 9.7% and 14.3% for the U1 (0.5% UI of the dry weight of the mixture) and U2 (1% UI of the dry weight of the mixture) treatments, respectively. The addition of UI inhibited the enzyme activity during thermophilic stage while increased enzyme activity during the cool and maturity stages. Ascomycota, Basidiomycota and unclassified fungi were the main phyla, and Ascomycota increased significantly during the maturity period. Network analysis showed that Aspergillus, Penicillium, Trichoderma, Talaromyces, Peseudeurotium, and Exophiala were the main "connecting" genera. The redundancy analysis (RDA) showed that the fungal community was mainly influenced by temperature, DOC, pH, and urease. The results suggested that UI was an effective additive for nitrogen conservation and the increase of enzyme activity reduce nitrogen loss and promote enzyme activity during biosolids composting.

Influence of reusable polypropylene packing on ammonia and greenhouse gas emissions during sewage sludge composting-a lab-scale investigation.

Bulking agents are particularly important for sewage sludge composting. In this study, reusable polypropylene packing (RPP) was mixed with sawdust to improve composting. The effect of the mix ratio of sawdust and RPP on the physicochemical characteristics, nitrogen transformation, and emissions of greenhouse gas (GHG) as well as differences in the germination index values was detected in a lab-scale composting experiment. The results showed that the unique use of RPP as a bulking agent increased the moisture content over 70%, which resulted in poorer porosity and a less efficient O2 utilization environment and thus suppressed the degradation of organic matter. The highest CH4 9275.8 mg and lowest CO2 202.6 g emissions were detected after 25 days of composting in the treatment with RPP used as a bulking agent. When the mixing ratio of sawdust and RPP was 1:1, the temperature, oxygen supply, and dissolved organic carbon degradation were improved. The NH3, N2O, and CH4 emissions were reduced by 32.2, 18.3, and 90.7% compared with a treatment with RPP as a unique bulking agent. The RPP had no effect on conserving nitrogen during sludge composting; the total nitrogen loss was reduced from 29.3 to 18.2% when sawdust was mixed with RPP in a ratio of 1:1. Therefore, mixing RPP and sawdust in the dry weight ratio of 1:1 (sawdust: RPP) can be potentially used for reducing composting cost and improving the sewage sludge composting by reducing the amount of sawdust mixed and mitigating GHG and NH3 emissions.

Use of additives in composting informed by experience from agriculture: Effects of nitrogen fertilizer synergists on gaseous nitrogen emissions and corresponding genes (amoA and nirS).

The effects of two nitrogen fertilizer synergists (urease inhibitor, UI; nitrification inhibitor, NI) on NH3 and N2O emissions and the successions of the amoA and nirS genes during composting were assessed. Results showed that the UI and UI + NI treatments reduced NH3 emissions by 26.3% and 24.3%, respectively, and N2O emissions were reduced by 63.9% for UI + NI treatment but were not reduced by UI. The addition of UI and NI significantly reduced the abundance of the nirS gene during thermophilic stage, while significantly increased that of the amoA gene during maturation stage. Crenarchaeota was the principal nitrifying archaeal phylum and was significantly affected by pH. Proteobacteria was the main denitrifying bacterial phylum, whose relative abundance was higher for UI + NI treatment than the other treatments. PICRUSt analysis showed that the addition of UI and NI inhibited enzymatic activity related to N transformation during thermophilic stage while enriching enzymatic activity during maturation phase.

Composting pig manure and sawdust with urease inhibitor: succession of nitrogen functional genes and bacterial community.

Understanding the relationship between nitrogen (N) cycle and N transformation-related functional genes is crucial to reduce N loss during composting process. Urease inhibitor (UI) is widely used to reduce N loss in agriculture. However, the effects of UI on N transformation and related N functional genes during composting have not been well investigated. The goal of this study was to investigate the effects of a urease inhibitor (UI) on N functional genes and bacterial community succession during pig manure composting. Results showed that the addition of UI decreased the ammonium N content during the thermophilic stage and notably increased the total N and nitrite N contents of the final compost. The UI significantly decreased the abundances of amoA, nirS, nirK, and nosZ during the initial composting stage, while the opposite trend was observed at the maturation stage. Bacterial community richness and diversity were increased after the UI amendment, but the relative abundance of the phyla Firmicutes and Proteobacteria significantly decreased compared with control during the thermophilic stage. Redundancy analysis indicated that the evaluated environmental factors and bacterial community showed a cumulative 94.7% contribution to the total variation in N functional genes. In summary, UI addition is a recommended method for N conservation during composting, but the added forms of UI, such as delayed addition, combined with adsorbing materials, or microorganism inoculant, should be further evaluated.

Adding Phosphate Fertilizer and Apple Waste to Pig Manure during Composting Mitigates Nitrogen Gas Emissions and Improves Compost Quality.

Calcium superphosphate and apple ( Mill.) waste can be used for controlling N loss and improving compost quality during composting, whereas integrated addition of the two additives on composting process remains unexplored. Therefore, this study was conducted to investigate the effects of combined use of calcium superphosphate and apple waste on NH and NO emissions and compost quality during pig manure and wheat ( L.) straw composting. Mixtures of pig manure and wheat straw were combined with 6% phosphate fertilizer (PF), 15% apple waste (AW), 3% phosphate fertilizer + 7.5% apple waste (PA1), or 1.8% phosphate fertilizer + 10.5% apple waste (PA2) based on dry weight of the initial mixtures; a treatment with no additives served as a control (CK). The PF treatment took 3 d longer to reach thermophilic phase than the CK, PA1, and PA2 treatments. The treatments of PF and PA1 reduced NH and NO emissions by 67 and 45%, respectively. Moreover, N loss in PF and PA1 treatments (31.8 and 30.1%, respectively) was significantly less than in the CK. A pot experiment showed that application of the compost with PA1 treatment could increase plant height and dried biomass of Chinese pakchoi ( L. ssp.). We recommend adding 3% phosphate fertilizer and 7.5% apple waste to pig manure during composting.

[Concentration Characteristics and Source Analysis of PM2.5 During Wintertime in Zhengzhou-Xinxiang].

To study the pollution characteristics, sources, and transportation process of PM2.5 and its chemical compositions in the Zhengzhou-Xinxiang region, PM2.5 samples were collected using a middle volume sampler, in Zhengzhou and Xinxiang urban areas for 30 consecutive days during the winter of 2016. The mass concentration of PM2.5 was measured gravimetrically. 17 trace metals were determined by inductively coupled plasma-mass spectrometry (ICP-MS), and 7 water-soluble ions were determined by ion chromatography. The enrichment factor (EF) method and principal component analysis were employed to determine the source apportionment. The results showed that the daily mean PM2.5 mass concentration during the winter sampling period of 2016 in Xinxiang and Zhengzhou was 223.87 µg·m-3 and 226.67 µg·m-3, respectively, which indicated that pollution levels were relatively high in both cities. The concentration of three macro elements (Al, Ca, and Fe) accounted for 50% of the total metal elements in both cities, while the heavy metals concentration was higher in Xinxiang than in Zhengzhou. The EFs of Cd, Ag, and Pb in Xinxiang were far higher than 1000, while only Cd was higher than 1000 in Zhengzhou. NO3-, SO42-, and NH4+ were the main ions in the two cities. They exceeded 94% of total water-soluble ions and existed in the forms of (NH4)2SO4 and NH4NO3. The principle component analysis showed that the main contributors to PM2.5 were a mixture of biomass combustion and secondary aerosol in Xinxiang, and a mixture of coal combustion and traffic emissions in Zhengzhou, accounting for 34.94% and 33.99% of total PM2.5 emissions, respectively.

Exploring the mechanisms of organic matter degradation and methane emission during sewage sludge composting with added vesuvianite: Insights into the prediction of microbial metabolic function and enzymatic activity.

Effect mechanisms of organic matter (OM) degradation and methane (CH4) emission during sewage sludge (SS) composting with added vesuvianite (V) were studied by high-throughput sequencing (HTS) and phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt). Results show that the addition of V accelerated the OM degradation and decreased the cumulative CH4 emissions by 33.6% relative to the control. In addition, V significantly decreased the mcrA gene abundance and the methanogen community richness at the genus level. PICRUSt also indicated that V strengthens the microbial metabolic function and enzymatic activity related to OM degradation, and reduced the enzymatic activity related to CH4 production. Methanogens community variation analysis proved the ratio of carbon and nitrogen and moisture content are the significant variables affecting CH4 emissions. Thus, optimizing the ratio of carbon and nitrogen and moisture content will decrease CH4 emission during SS composting.

Beneficial influences of pelelith and dicyandiamide on gaseous emissions and the fungal community during sewage sludge composting.

Reducing the emissions of NH3 and greenhouse gases (GHGs) during composting is essential for improving compost quality and controlling environmental pollution. This paper investigates the effects of pelelith (P) combined with dicyandiamide (DCD) on gaseous emissions and the fungal community diversity during sewage sludge (SS) composting. Results showed that the P and P + DCD treatments decreased the cumulative gaseous emissions by 41% and 22% for NH3, 21% and 34% for N2O, and 31.5% and 33.0% for CH4, respectively. The evolution of the fungal community analysis showed that Ascomycota and unclassified fungi dominated during the thermophilic stage, while only Ascomycota was the dominant fungal phylum during the maturity stage, composing 62%, 66%, and 73% of the total fungal community in the control, P, and P + DCD, respectively. The P and P + DCD significantly increased the fungal community richness at the genus level. Fungal community abundance was found to be significantly related to temperature, pH, organic matter, and total Kjeldahl nitrogen, which also influence the gaseous emissions during SS composting. It suggested that the combined addition of pelelith and dicyandiamide (DCD) was an effective method for reducing the emissions of NH3 and greenhouse gases during SS composting.

A novel method for sewage sludge composting using bamboo charcoal as a separating material.

Traditional composting processes must be conducted with a bulking agent to ensure adequate air space for aeration. The bulking agent and composting materials are always completely mixed. A novel layered structure was introduced in sewage sludge composting, in which no bulking agent was used and bamboo charcoal was used as a separating material. Three lab-scale composting reactors (A: sawdust and sludge; B: bamboo charcoal and sludge; and C: sawdust, bamboo charcoal, and sludge) were continuously operated for 29 days. Several physicochemical parameters were investigated to evaluate the feasibility of layered composting with bamboo charcoal. The results indicated that the maximum temperatures during the thermophilic stage in treatments A, B, and C were 51.4, 50.9, and 51 °C, respectively. Layered composting with bamboo charcoal decreased the pH of the thermophilic stage from 8.98 in A to 8.75 in C, and delayed the peaks by about 120 h. The degradation rates of dissolve organic carbon (DOC) and dissolved nitrogen (DN) were 75 and 71.5% in treatment B, respectively, which were significantly higher than those of control group A (60 and 59.1%, respectively). The total NH3 emissions of treatment C (2127.8 mg) were significantly lower than those of A (2522.8 mg). Our results suggested that layered composting using bamboo charcoal as a separating material could be an alternative strategy to the traditional composting method. Moreover, layered composting combined with sawdust could effectively reduce NH3 emissions and N loss.

Evaluation of total greenhouse gas emissions during sewage sludge composting by the different dicyandiamide added forms: Mixing, surface broadcasting, and their combination.

The aim of this work was to compare the impact of different adding forms of dicyandiamide (DCD) on NH3 and greenhouse gas (GHG) emissions during sewage sludge (SS) composting. Four treatments were set up using SS mixed with sawdust, to which DCD was then added by mixing (M), surface broadcasting (B), and a combination of the two (M+B). The treatment without DCD applied was used as the control. The results indicate that the addition of DCD slightly inhibited the organic matter (OM) degradation, but that it had no significant effect on CO2 emission. The surface mulching of DCD has no significant effect on NH3, N2O, and CH4 emissions. The mixing addition of DCD significantly increased the NH3 emission by 32.5% compared to that of the control. The N2O emission for the M and M+B treatments significantly decreased by 35.1% and 51.8%, respectively. The CH4 emission for the M and M+B treatments decreased by 33.9% and 31.8%, respectively. In addition, the total GHG emissions for the M and M+B treatments were significantly reduced by 16.7-25.7% (P < 0.05) compared to those of the control. Therefore, to reduce the total GHG emissions of the SS composting process, the addition of DCD by a combination of mixing and surface mulching is strongly recommended as a highly efficient solution.