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High humidity and potential threat of pathogen of anaerobic digestates are unfavorable to the environment by direct utilization. To achieve the sustainable utilization of digestates, composting might be a good choice. Meanwhile, the aeration rate of composting has been optimized. Co-composting of digestates and chicken manure was performed under di...
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... and 120 maintained it at around 60% during the whole composting process to support microbial 121 activities ( Liang et al., 2003 which had been reported by Y. Zhao et al. (2016). Briefly, the feedstock in the cylinder was about 16.25 kg. The air compressor was connected with an air flow meter which 130 had a control knob to adjust the air flow (Fig. S1). Thereafter, the fresh air will be 131 pumped into the reactor from the bottom to top. Compost material was dumped for 132 remixing every two days to assure the uniformity of composting aeration. The were stored in a refrigerator at -20 ℃ for further ...
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... petri dishes were cultured at 25 ℃ for 3 days. All the determinations for seeds 145 germinations were carried out by triplicate. Seeds with root lengths <2 mm were not 146 considered germinated. GI was calculated as follows: treatments fulfilled the demands of maturity and non-biotoxicity, even though the GI 231 decreased on day 7 (Fig. 1e). On day 0, the GI was about 32%, it was too low for the 232 raw materials to be directly utilized to soil, which also proved that the raw digestates biological toxicity, composting products derived from T3 might be the best choice for 240 farming utilization. According to the accumulative CO2 emission, the higher the 241 aeration rates ...
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... it was too low for the 232 raw materials to be directly utilized to soil, which also proved that the raw digestates biological toxicity, composting products derived from T3 might be the best choice for 240 farming utilization. According to the accumulative CO2 emission, the higher the 241 aeration rates is, the faster the stability of composting (Fig. 1f). However, there was 242 little difference between T2 and T3 in the accumulation of CO2, indicating that aerations 243 of T2 and T3 had the similar roles in promoting the stability of composting ...
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... This was due to the piles compacted slightly in the initial-material, and the aerobic microorganisms were inactive. The interplay of the change in FAS, MC, and O 2 concentration resulted in high φ, µ 1 and µ 2 values but a low α value during the temperatureincreasing phase (Ge et al., 2016;Yue et al., 2008;Wu et al., 2019). The compost piles were most severely compacted during the thermophilic phase, in which the φ value was the highest. ...
Insufficient O2 concentration in the matrix pores, which is adjusted by air-immobile regions in compost piles, is a main factor in forming anaerobic cores in compost particles and then generating harmful off-gases during composting. However, it is unclear how the change of air-immobile regions affects temporal variation of O2 in the pores during the whole composting process and after turning. In this study, we first used a tracer-inverse calculation protocol to obtain feature parameters (proportional coefficient of gas in the air-immobile region, φ; the first-order mass transfer coefficient, α) of the air-immobile regions in the matrix pores before and after turning during whole composting process, and then predicted the temporal variation of O2 in the pores using two-region model with these measured parameters. The φ values in compost piles for initial-material, temperature-increasing, thermophilic, and curing phases were 0.38/0.40, 0.42/0.40, 0.46/0.46, and 0.41/0.45 before/after turning, respectively, while the corresponding α values were 0.002/0.001, 0.001/0, 0.004/0, and 0.005/0.001 min-1, respectively. The proportion of air-immobile regions was higher in the temperature-increasing and thermophilic phases than in the curing phase. The air-immobile regions caused difference of predicted O2 concentrations between air-mobile and air-immobile regions, and the difference was enhanced during the composting mainly by the rate of organic-matter biodegradation. Turning piles slightly decreased φ in the temperature-increasing phase and had little change in thermophilic phase, while it caused slight increases in φ during other phases. The value of α declined throughout composting process after turning. These findings provide support for reducing the production of harmful off-gases in composting.
... Rasapoor et al. (2009) showed that the aeration rate at 0.6 L/(min · kg organic matter) at the initial stage of composting was the most reasonable for the municipal wastes and was better to decrease to 0.4 L/(min · kg organic matter) at the maturation stage of composting. Therefore, it can be concluded that the aeration rate parameters are appropriate in the range of 0.2 ~ 0.6 L/ (min · kg organic matter) (Chowdhury et al., 2014;Talib et al., 2014;Zhang et al., 2016;Wu et al., 2019). However, there is also an obvious effect of aeration mode on the nitrogen conversion and loss in composting (Peng et al., 2023;Lai et al., 2024). ...
Aeration is an important factor to regulate composting efficiency and nitrogen loss. This study is aimed to compare the effects of different aeration modes (continuous and intermittent) and aeration rate on nitrogen conversion and bacterial community in composting from dehydrated sludge and corn straw. Results showed that the intermittent aeration mode at same aeration volume was superior to the continuous aeration mode in terms of NH3 emission reduction, nitrogen conversion and germination index (GI) improvement. Intermittent aeration mode with 1200 L/h (aeration 5 min, stop 15 min) [K5T15 (V1200)] and 300 L/h of continuous aeration helped to the conservation of nitrogen fractions and accelerate the composting process. However, it was most advantageous to use 150 L/h of continuous aeration to reduce NH3 emission and ensure the effective composting process. The aeration mode K5T15 (V1200) showed the fastest temperature rise, the longer duration of thermophilic stage and the highest GI (95%) in composting. The cumulative NH3 emission of intermittent aeration mode was higher than continuous aeration mode. The cumulative NH3 emission of V300 was 23.1% lower than that of K5T15 (V1200). The dominant phyla in dehydrated sludge and corn straw composting were Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes. The dominant phylum in the thermophilic stage was Firmicutes (49.39%~63.13%), and the dominant genus was Thermobifida (18.62%~30.16%). The relative abundance of Firmicutes was greater in the intermittent aeration mode (63.13%) than that in the continuous aeration mode (57.62%), and Pseudomonas was dominant in composting with lower aeration rate and the lowest NH3 emission. This study suggested that adjustment to the aeration mode and rate could affect core bacteria to reduce the nitrogen loss and accelerate composting process.
... Composting of agricultural waste was conducive to the formation of solid phase macromolecular HS (mainly including humic acids (HA) and fulvic acids (FA)) (Wu et al. 2019;Svensson et al. 2022). Previous studies have shown that HS plays an important role in the passivation of heavy metals, especially HA (Kang et al. 2011;He et al. 2016;Li et al. 2021). ...
... The C/N ratio in the two treatments exhibited a similar decreasing trend during the whole composting process. It may be related to the CO 2 release resulting from the decomposition of OM (Wu et al. 2019). The C/N ratio of B declined more quickly than that of A, which further demonstrated that the inoculation of fungus could improve the composting process. ...
Co-composting with agriculture waste and sediment is an effective method to passivate the heavy metal content of sediment, but it is still unclear whether this passivation will be effective in the long term, and the contribution of different components of humic substances (HS) to the passivation of heavy metals has not been investigated quantitatively.
A 256-day composting experiment was conducted in 165 L reactors. Sediment, vegetables, rice straw, and bran were used as raw materials. Two experiments were set up, with pile A as control and pile B inoculated with Phanerochaete chrysosporium.
The results revealed that the residual fraction of Cd (Res-Cd) increased by 24.22% and 27.04% in pile A and pile B, respectively. During the first 60 days of composting, the contents of humic acids-bound Cd (HA-Cd) both increased in two piles and accounted for 16.54% and 17.69% of the total content of Cd (T-Cd) in pile A and pile B, respectively. The correlation analysis suggested that the Res-Cd exhibited a significantly positive correlation with humic acid (HA) (P < 0.01) and HA-Cd, but a negative correlation with fulvic acid (FA) in both piles. Fourier-transform infrared spectroscopy and excitation-emission matrix fluorescence spectroscopy analysis demonstrated that the inoculation could enhance the chelating capability of HA to Cd and improve the maturity of compost.
This study has demonstrated that composting had a persistent passivation on Cd for 256 days. The contribution of HS to Cd passivation largely depends on the amount of HA-Cd rather than FA-Cd. Moreover, the inoculation of Phanerochaete chrysosporium could enhance the binding ability of HA to Cd and improve the maturity of compost.
... The ultimate and most vital product of the composting process is humic substance. It is a heterogeneous mixture of insoluble humin, acid/base soluble acid including fulvic acid and humic acid, among which humic acid is the most stable [48,49]. ...
The concept of recycling organic matter and waste nutrients back to agricultural land through the process of composting adheres to the basic principle of the circular economy. The studies on composting systems have laid a solid foundation for biodegradable solid waste management, and there are still significant gaps that require attention in future research. Addressing these gaps will lead to a more comprehensive understanding of composting processes, improved compost quality, and sustainable waste management practices with greater benefits for agriculture and the environment. The transition to a blended centralized and decentralized waste management system necessitates the conception of an adaptable system for waste management with higher quality compost production. Furthermore, countless agro-industrial products have emerged during this transition phase including commercial fertilizers, nitrogen fortifiers, phosphocompost, biofertilizers, compost tea, and compost biofilters that use compost as a base. The agro-industries might be engaged to participate in research and development in the forthcoming time to develop compost-based commodities. The current systematic study takes into account the long-term sustainability of composting systems harnessing compost valorization. In addition, this review highlights the various agro-industrial commodities that researchers should be concentrated on.
... The obtained FA solution was filtered with an XAD-8 resin column and discarded the effluent. Next, the XAD-8 resin column was rinsed with deionized water until the pH of the eluate was 7, then rinsed with 0.1 M NaOH and collected the eluate to pass through a hydrogen-type cation exchange resin column to acquire the FA component which also freeze-dried at − 54 • C to store (Wu et al., 2019). ...
The compost-derived humic acids (HA) and fulvic acids (FA) contain abundant active functional groups with strong redox capacity, which can function as an electron shuttles for promoting the reduction of heavy metals, thus changing the form of the pollutants in the environment and reducing their toxicity. Therefore, in this study, UV-Vis, FTIR, 3D-EEM, electrochemical analysis were applied to study the spectral characteristics and electron transfer capacity (ETC) of HA and FA. Upon analysis, the results showed an increasing trend of ETC and hu-mification degree (SUVA 254) for both HA and FA during composting. However, the aromatic degree (SUVA 280) of HA was higher than FA. After 7 days of culture, 37.95% of Cr (VI) was reduced by Shewanella oneidensis MR-1 (MR-1) alone. Whereas, only if HA or FA existed, the diminution of Cr (VI) reached 37.43% and 40.55%, respectively. However, the removal rate of Cr (VI) by HA/MR-1 and FA/MR-1 increased to 95.82% and 93.84% respectively. It indicated that HA and FA acted as electron shuttles, mediating the transfer of electrons between MR-1 and the final electron acceptor, effectively facilitating the bioreduction of Cr (VI) to Cr (III) and also determined via correlation analysis. This study suggested compost-derived HA and FA coupling with MR-1 exhibited excellent performance for the bioreduction of Cr (VI) to Cr (III).
... Therefore, bacteria and fungi with high aromatic synthesis ability should be identified and screened for use in composting as microbial inoculants. Additionally, regulating the key microorganisms of SKP, enhancing enzyme activity through the use of exogenous catalysts, or enzyme activators/co-factors, can also increase aromatic compound production (Wu et al. 2019;Kadri et al. 2017). In summary, regulating the compost microenvironment, improving key microbial activity, and enhancing enzyme activity can become effective strategies to improve SKP metabolic intensity during composting. ...
Microbial shikimic acid is an important intermediate metabolite in the synthesis of aromatic amino acids which are precursors for forming humus during composting process. Generally, the pathways producing shikimic acid and its downstream products are collectively referred as shikimic acid pathway (SKP). Microbial SKP can produce phenols, and tyrosine. Pyrogallol is the precursor of phenols. And, tyrosine can form an ammoniated monomer. Therefore, regulation of SKP can promote shikimic acid production, which is beneficial in promoting humus production and humification. However, SKP present in microbial cells is distinctive because of providing precursors for humification process, which needs to be recognized during composting. Due to the different structures of various organic wastes, it is difficult to control the SKP efficiency and shikimic acid production. Therefore, it is valuable to review the synthesis of shikimic acid by microorganisms and propose how to promote SKP during different materials composting. Furthermore, we have attempted to illustrate the application of metabolites from SKP in forming humus during organic waste composting. Finally, a series of regulating methods has been outlined to enhance microbial SKP, which are effective to promote humus aromatization and to improve humus formation during different materials composting.
... Composting can also help transform OM into a stable humic-like matter (Wang et al., 2022a). Compost with a germination index (GI) greater than 80% is not phytotoxic and can improve the physico-chemical properties of soil (Wu et al., 2019;Zhao et al., 2022). Moreover, several studies have demonstrated that the composts of digestate from sewage sludge or agricultural waste could promote plant growth by improving soil properties, such as pH, conductivity, and nutrient levels (Rossini-Oliva et al., 2017;Carnimeo et al., 2022). ...
The treatment of digestate from food waste (DFW) has emerged as the bottleneck for food waste anaerobic digestion. DFW generally contains abundant nutrients that can be recycled by composting. However, the effect of DFW-based compost on soil improvement has not been extensively explored. In this study, soil properties were improved by adding various amounts of DFW-based compost, and the growth conditions of Pak choi were monitored. The results indicated that the DFW-based compost could provide nitrogen, calcium, magnesium, and organic matter, thereby enhancing the growth of Pak choi, accumulating chlorophyll, and improving photosynthesis efficiency. As the amount of added DFW-based compost increased from 0% to 20%, the fresh biomass, leaf weight, and root weight of Pak choi increased by 242%, 262%, and 99%, respectively. The total chlorophyll content was 2.62 mg g-1 in control and increased to 12.45 mg g-1 in the group with 20% DFW-based compost, benefiting the photochemical efficiency of Pak choi. However, the growth was inhibited when the addition amount exceeded 20%, potentially due to excessive nutrient supplementation. Overall, the addition of 20% of DFW-based compost was suggested to promote the growth of Pak choi by providing proper nutrients.
... Aeration is one of the key parameters in controlling the activities of the waste being composted, as it influences the temperature, moisture, and O 2 supply to the microorganisms (Wu et al., 2019). In the composting process, the predominant microorganisms are aerobic. ...
Organic wastes are considered the most significant components of urban solid waste, negatively affecting the environment. It is essential to use renewable resources to minimize environmental risks. Composting is one of the most sustainable methods for managing organic waste and involves transforming organic matter into a stable and nutrient-enriched biofertilizer, through the succession of microbial populations into a stabilized product. This work aimed to evaluate the efficiency of the new type of composter and the microbial and physiochemical dynamics during composting aiming to accelerate the degradation of organic waste and produce high-quality compost. Two inoculants were evaluated: (1) efficient microorganisms (EM); (2) commercial inoculum (CI), which were compared to a control treatment, without inoculation. Composting was performed by mixing organic waste from gardening with residues from the University's Restaurant (C/N ratio 30:1). The composting process was carried out in a 1 m ³ composter with controlled temperature and aeration. The thermophilic phase for all treatments was reached on the second day. Mature compost was obtained after an average of 120 days, and composting in all treatments showed an increase in the availability of P and micronutrients. The new composter helped to accelerate the decomposition of residues, through the maintenance of adequate oxygen content and temperature control inside the cells, providing high metabolic activity of microorganisms, contributing to an increase in physicochemical characteristics, also reducing the composting time in both treatments. During composting, the bacteria and actinobacteria populations were higher than yeasts and filamentous fungi. The inoculated treatments presented advantages showing more significant mineralization of P-available and micronutrients such as Mn and Zn in terms of the quality of the final product in comparison to the control treatment. Finally, the new composter and the addition of inoculants contributed significantly to the efficiency of the process of composting organic waste.
... The pH value of AR0.2 was always lower than that in AR0.4 and AR0.6, which might be due to the increased accumulation of organic and inorganic acids from organics decomposition and more local anaerobic reactions in groups with lower aeration rate at mesophilic and thermophilic stages (Ge et al., 2020). The pH of AR0.4 and AR0.6 increased rapidly after day 4 compared to AR0.2, which might be related to the enhanced degradation of nitrogen-rich organics and accumulated ammonium nitrogen in higher aeration conditions but incomplete degradation of organics and organic acids formation in lower aeration conditions (Ge et al., 2022;Wu et al., 2019). Since the 15th day, the pH value of AR0.2 raised rapidly result from short-chain organic acids consumption and pH in AR0.4 and AR0.6 was slightly fluctuant in alkali ranges. ...
This study was to investigate the effects of different aeration rates on phosphorus (P) conversion and bacterial community dynamics in P-enriched composting by 16S rRNA gene sequencing, sequential P fractionation, network analysis and structural equation model (SEM). Results indicated that Olsen P content increased by 138%, 150%, 121% after composting with aeration rate (L kg⁻¹ DM min⁻¹) at 0.2 (AR0.2), 0.4 (AR0.4) and 0.6 (AR0.6). AR0.4 was more conducive to enhance P solubilization efficacy and available P accumulation. Redundancy analysis indicated Lactobacillus, Spartobacteria and Pseudomonas were key bacteria associated with HCl-Pi especially in AR0.2 and AR0.4. Network analysis showed that increased aeration rate enhanced the connection and function homoplasy among modules and AR0.4 had more orderly community organization for key bacteria to solubilize P in directly and indirectly biotic way. SEM suggested indirectly biotic P-solubilization had more contribution than directly biotic way mainly by phosphate-solubilizing bacteria.
... In addition to the risk of being inadequate, forced aeration requires greater investments and higher costs for the composting process (Rasapoor et al., 2016). Among the main factors that contribute to inadequate aeration are the ow rate and the distribution of air throughout of material in composting (Wu et al., 2019) and characteristics of waste as composition, and compression ability (Kazemi et al., 2017). ...
The objective of this study was to evaluate the influence of forced aeration and season on hatchery waste composting in static windrows with perforated walls. there were three well-defined thermophilic phases during composting, with the first occurring immediately after the formation of the windrows and the others occurring after turnovers at 50 and 70 days of composting. Aeration resulted in greater degradation (p<0.01) of volatile solids (VS), carbon (C), and lignin in the composting windrows during the summer up to 50 days of process, in comparison to no aeration piles. However, at 70 and 90 days of composting, the results were similar between aerated and nonaerated windrows. The greatest (p<0.01) degradation of nitrogen (N) occurred during the winter and in the absence of aeration (55.25%). Season influenced (p<0.05) the concentrations of humic acids, and they were higher in the compost generated during the summer than generated during the winter. The concentrations of Mg, Fe and Na were influenced by the season, with higher values (p<0.01) in the summer, however they were not affected by aeration. In the winter, aeration is recommended after 50 days of composting, whereas in summer, forced aeration is beneficial for N conservation and humic acid formation.
