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The initial carbon/nitrogen (C/N) ratio is one of the most important factors impacting composting processes, such as methane (CH 4 ) emissions. However, the effects of the C/N ratio on CH 4 emissions and the associated biological mechanisms during vegetable waste composting are largely unknown. In this study, a lab-scale experiment was conducted to investigate the effects of different C/N ratios on CH 4 emissions and the mechanisms associated with methane-metabolizing microorganisms (methanogens and methanotrophs) during capsicum straw composting. The initial C/N ratios were set to 18, 30 and 50 to simulate the low (L), medium (M) and high (H) C/N ratios, respectively. The results showed that CH 4 emissions were mainly concentrated in the thermophilic phase and that the cumulative CH 4 emissions were significantly greater in the L treatment than in the M and H treatments by 10.8 and 15.4 times, respectively. During the methanogenic process, the relative abundance of the dominant genus Methanoculleus (47.59 % ∼ 76.92 %) was higher than in the L treatment than in the M and H treatments at the thermophilic and maturation stages, and the Chao1 index and the mcrA gene abundance followed the order of L > M > H at each composting stage. During the methanotrophic process, the dominant genus unclassified_d_bacteria (51.3 % ∼ 91.87 %), Chao1 index, pmoA gene abundance and CO 2 emissions were in the order of L > M > H at each composting stage. This pattern suggests that a lower C/N ratio simultaneously enhanced CH 4 production and oxidation. A structural equation model further revealed that the methanogenic community, which was driven directly by the relative contents of hemicellulose and cellulose in the substrates, as indicated by the C/N ratio, made greater contributions to CH 4 emissions than did the methanotrophic community. In conclusion, a lower C/N ratio increased CH 4 emissions mainly by regulating the population and composition of methanogen community., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The use of lignocellulosic residues, originating from sawdust, in composting sewage sludge for organic fertilizer production, is a practice of growing interest. However, few studies have explored the effect of the proportion of sawdust and sewage sludge raw materials on composting performance in the humification process. This study assessed the addition of sawdust in the sewage sludge composting process, regarding carbon content, presence of heavy metals, and humification of the organic compost. The experimental design employed was a randomized complete block design with five treatments featuring different proportions of organic residues to achieve C/N ratios between 30-1 (T1: 100% sewage sludge and 0% sawdust, T2: 86% sewage sludge and 14.0% sawdust, T3: 67% sewage sludge and 33% sawdust, T4: 55% sewage sludge and 45% sawdust, and T5: 46.5% sewage sludge and 53.5% sawdust) and five replications, totaling 25 experimental units. The addition of lignocellulosic residue in sewage sludge composting increased the levels of TOC and the C/N ratio, reduced the levels of pH, P, N, Na, Ba, and Cr, and did not interfere with the levels of K, Ca, Mg, S, CEC, labile carbon, and metals Fe, Zn, Cu, Mn, Ni, and Pb. The increase in the proportion of sawdust residue favored the degradation of aliphatic groups, increasing the presence of aromatic structures and reducing humification at the end of composting. The use of sawdust as a lignocellulosic residue in sewage sludge composting is a viable and efficient alternative to produce high-quality organomineral fertilizers., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Nitrous oxide (N 2 O) generation during composting not only leads to losses of nitrogen (N) but also reduces the agronomic values and environmental benefits of composting. This study aimed to investigate the effect of the C/N ratio on N 2 O emissions and its underlying mechanisms at the genetic level during the composting of vegetable waste. The experiment was set up with three treatments, including low C/N treatment (LT, C/N = 18), middle C/N treatment (MT, C/N = 30), and high C/N treatment (HT, C/N = 50). The results showed that N 2 O emission was mainly concentrated in the cooling and maturation periods, and the cumulative N 2 O emissions decreased as the C/N ratio increased. Specifically, the cumulative N 2 O emission was 57,401 mg in LT, significantly higher than 2155 mg in MT and 1353 mg in HT. Lowering the C/N ratio led to increasing TN, NH 4 + -N contents throughout the composting process. All detected nitrification-related gene abundances in LT continued to increase during composting, significantly surpassing those in MT during the cooling period. By contrast, in HT, there was a slight increase in the abundance of detected nitrification-related genes but a significant decrease in the abundance of narG, napA, and norB genes in the thermophilic and cooling periods. The structural equation model revealed that hao and nosZ genes were vital in N 3 O emissions. In conclusion, increasing the C/N ratio effectively contributed to N - O reduction during vegetable waste composting.2 O emissions. In conclusion, increasing the C/N ratio effectively contributed to N 2 O reduction during vegetable waste composting., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The purpose of this study was to examine the effects of replacing urea with inorganic nitrogen on the organic nitrogen sequestration process and the mitigation of nitrogen loss during rice straw composting. These groups include a control group with urea addition (CK), a group with (NH 4 ) 2 SO 4 addition (NH), a group with KNO 3 addition (NO), and a group with (NH 4 ) 2 SO 4  + KNO 3 addition (NN). The results demonstrated that adding NH, NO, and NN significantly increased the content of bioavailable organic nitrogen in the composting. Furthermore, compared to the CK, the NH treatment reduced nitrogen loss by 8.41 %. Structural equation modeling revealed the correlation between bacterial communities and organic nitrogen fractions in different treatment groups. Comparisons of nitrogen efficacy and nitrogen loss indicated that adding (NH 4 ) 2 SO 4 was more effective during composting, which provided a meaningful research basis for rice straw composting., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Studies on compost dissolved organic matter (DOM) previously focus on its composition and humification, without considering DOM bioavailability to understand compost fertility. To decipher the fertility basis of compost, DOM bioavailability in thermophilic compost (TC) and vermicompost (VC) was investigated and linked with its molecular composition. Results showed that DOM bioavailability of VC (36 % BDOC) was generally higher than that of TC (22 % BDOC) due to containing more tannin-like substances. Inversely, only lipid-/carbohydrate-/protein-like substances contributed to DOM bioavailability in TC. Moreover, these differences of bioavailability expanded with C/N decreased in composting materials. Specifically, the %BDOC of VC with N-rich materials (C/N < 25) was 2.1-3.0 times higher than that in TC, while it was only 1.2-1.4 times for C-rich materials (C/N < 25), because N-surplus facilitated the formation of O-/N-containing aromatics (e.g., CHON and tannin) in VC, but inhibited the decomposition of organic materials into small bioactive molecules in TC., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Even though sewage sludge (SS) contains a high level of pollutants, it is rich in essential plant nutrients and has the potential to enhance soil fertility. However, the SS must be further treated through pre-composting plus vermicomposting to make it safe for use on food crops. More research and data are needed to determine how different carbon-to-nitrogen ratios (C/N) affect the feasibility and quality of composting vs vermicomposting of SS. Therefore, in this study we comprehensively evaluated the feasibility and end-product quality of compost and vermicompost produced from SS under different C/N ratios. SS was mixed with pelletized wheat straw (PWS) at various proportions to produce C/N ratios of 6:1, 18:1, 28:1, and 38:1, then pre-composted for 14 days followed by vermicomposting using the earthworm Eisenia andrei for 120 days. Agrochemical properties were measured at 0, 30, 60, 90, and 120 days. Results revealed significantly higher levels of agrochemicals in vermicompost compared to compost, including total potassium (37-88%) and magnesium (4.3-12%), nitrate nitrogen (71-98%), available potassium (53-88%), available phosphorus (79%), available magnesium (54-453%), available boron (48-303%), and available copper (2.5-82%). However, lower levels of ammonium nitrogen by (59-85%), available iron (2.3-51.3%), available manganese (29.7-52.2%), available zinc (10.5-29.8%), total carbon (0.75-4.5%), and total nitrogen (1.6-22.2%) were measured. Comparison of the various C/N ratios, showed that vermicompost with an 18:1 C/N ratio outperformed compost and demonstrated the highest earthworm population (165 pieces/kg). Thus, vermicomposting SS at an 18:1 C/N ratio is strongly recommended as a sustainable technology for producing high-quality vermicompost from SS., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Inc.)

The relationships among the relative abundance of guild-plant pathogenic fungi, compost maturation index, and microbial community variation during vegetable waste composting, which are influenced by the C/N ratio, remain poorly understood. To address this, fungal communities were analyzed in composting treatments with C/N ratios of approximately 15 (CN15) and 25 (CN25), using vegetable waste as the primary raw material. The CN15 treatment showed greater microbial community variation and a better overall compost maturation index value than the CN25 treatment. However, the CN25 treatment had a greater decline in plant-pathogenic fungi than the CN15 treatment. Notably, the relative abundance of guild-plant pathogenic fungi was significantly negatively related to the compost maturity index in the CN25 treatment, while no significant relationship was observed in the CN15 treatment. This study suggests that the moderately delayed maturation of composting is beneficial for reducing guild-plant pathogenic fungi in vegetable waste., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In tanneries, limed fleshing is an unavoidable waste generated in beamhouse operation. Proper management of limed fleshing with protein, fat, lime, and sulfide will help to protect the natural environment and at least reduce the pollution that ends up in it. In this study, excluding any pretreatment, limed fleshing is used for compost production. Chopped and mixed limed fleshing with chicken manure, cow dung, and sawdust was heaped onto a horizontal bamboo frame. Three composting heaps were fabricated weighing 720, 700, and 760 kg. The turning of composting materials in the heaps causes temperature changes in the thermophilic range. The thermophilic temperatures in these heaps were 69.07 °C (heap 1), 69.9 °C (heap 2), and 69.19 °C (heap 3) which ensured the death of the pathogenic organism. The quality of compost was assessed based on the nutrients-nitrogen (N), phosphorous (P), potassium (K), and sulfur (S) content. NPKS in the compost fulfils the requirements of the investigated materials as compost. The largest amounts of metals- zinc (Zn), copper (Cu), chromium (Cr), lead (Pb), and nickel (Ni) of the compost detected in the heaps were, respectively, 200.3, 37.4, 20.3, 12.0, and 3.9 mg/kg. Cadmium (Cd) in the compost was below the detection limit. Scanning electron microscope (SEM) photographs show the decomposing of composting materials. This study indicates that limed fleshing can be converted into nutrient-enriched compost without any pretreatment. Using an easy, simple, and adaptable technique could reduce the volume of solid waste generated in the tannery to reduce environmental pollution., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Current knowledge about the transformation of total mercury and methylmercury (MeHg) in aerobic composting process is limited. In this study, the composition and transformation of mercury and dissovled organic matter (DOM) in aerobic composting process of municipal sewage sludge were were comprehensively characterized, and the differences among the three C/N ratio (20, 26 and 30) were investigated. The main form of mercury in C/N 20 and 26 was organo-chelated Hg (F3, 46%-60%); while the main form of mercury in C/N 30 was mercuric sulfide (F5, 64%-70%). The main component of DOM in C/N 20 and 26 were tyrosine-like substance (C1, 53%-76%) while the main fractions in C/N 30 were tyrosine-like substance (C1, 28%-37%) and fulvic-like substance (C2, 17%-39%). The mercury and DOM varied significantly during the 9 days composting process. Compared to C/N 20 and 26, C/N 30 produced the less MeHg after aerobic composting process, with values of 658% (C/N 20), 1400% (C/N 26) and 139% (C/N 30) of the initial, respectively. Meanwhile, C/N 30 produced the best compost showed greater degree of DOM molecular condensation and humification. Hg fraction had been altered by DOM, as indicated by a significant correlation between mercury species and DOM components. Notably, C/N 30 should be used as an appropriate C/N ratio to control the methylation processes of mercury and degration of DOM., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Aerobic composting is an efficient and environmentally friendly method of converting organic waste into nontoxic fertilizers or soil quality enhancers. The quality of the resultant compost depends greatly upon the composition of the substrate used. The initial carbon-to-nitrogen (C/N) ratio of the substrate is an important factor affecting the composting process. This study elucidated how initial C/N ratios affect the biodegradation of lignocellulose, due to changes in microbial community structure. Four different C/N ratios (20:1, 25:1, 30:1, and 35:1) were examined during a 35-day composting process. The degradation of cellulose, hemicellulose, and lignin was highest (35.7%, 30.6%, and 19.1% respectively) at a 30:1 C/N ratio; after 30 days, the 25:1 C/N ratio ranked second in terms of lignocellulosic degradation rate. The 30:1 C/N ratio further promoted the growth of functional microorganisms responsible for lignocellulose degradation (Luteimonas, Sphingobium, Trichoderma, Chaetomium, and Rosellinia), while the growth of dominant pathogenic microbes (Erwinia and Ulocladium) decreased significantly. These results confirm that the initial C/N ratio of the substrate has a significant effect on the microbial community and degradation of organic matter, during walnut branch composting. This process could therefore offer an alternative means of efficient recycling and recovery of waste branches., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Disposal of animal carcasses by co-composting with animal waste usually selected conventional carbon to nitrogen (C/N) ratio around 25:1, in which the compost is widely used throughout the world. In this study, the pig carcass tissue blocks were sampled for composting at a laboratory scale to evaluate the effect of C/N ratio on the pig carcass compost. The time of thermophilic phase between 60 °C - 70 °C at a lower C/N ratio of 20:1 was significantly longer than that at the conventional C/N ratio, and it was the only one with the temperature beyond 70 °C that lasted for 2 days. Germination index and T value (the final C/N ratio / the initial C/N ratio) of the treatment with a C/N ratio of 20:1 were 94.67% and 0.69, respectively, meeting the standards of animal carcass compost. The degradation rate was 75.67%, and no significant difference was obtained as compared to the conventional C/N ratio groups. Organic fertilizer produced from the treatment with a C/N ratio of 20:1 was selected to evaluate the fertility by pot experiment of Cayenne pepper compared with chemical fertilizer. The results showed that organic fertilizer from this treatment could significantly improve the growth of Cayenne pepper. Overall, the use of the lower C/N ratio of 20:1 in the disposal of pig carcass by co-composting with swine manure could achieve the similar degradation rate as well as the maturity and stability of organic fertilizer as compared with the traditional C/N ratio at lab scale.

The current study evaluated the quality of agricultural waste digestate by composting or co-composting with biogas feedstock (maize silage, food processing waste, or poultry litter). Temperature, phytotoxicity, C/N ratio, water extractable trace elements, and 14 enzyme activities were monitored. Temperature dropped earlier in digestate and maize silage co-composting pile, reducing time to maturity by 20 days. Composting and co-composting reduced phytotoxicity and C/N ratio, but increased immobilization of Al, Ba, Fe, Zn, and Mn at least by 40% in all piles. All the enzyme activities, except arylsulfatase and α-glucosidase, increased at the maturity phase and negatively correlated with organic matter content and most of trace elements. Post-digestate composting or co-composting with biogas feedstock is a promising strategy to improve digestate quality for fertilizer use, and selected enzyme activities can be indicators of compost maturity and immobilization of trace elements., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Composting is an effective method for utilizing agricultural straw waste and livestock manure resources. Using deer manure and corn straw as raw materials, the changes in various indexes were studied during composting under different initial C/N ratios, initial moisture contents, and particle sizes of corn straw, and compost maturity was evaluated. Moisture content, total organic carbon content, and C/N ratio all declined during composting, while total nitrogen, total phosphorus, total potassium, pH, germination index, and electrical conductivity increased. The grey relational analysis method was used to evaluate maturity. The results showed that a mixture of stalk and deer manure with initial moisture content of 55%, initial C/N ratio of 30:1, and a straw particle size of 1.5-3.5 cm constituted the optimal experimental conditions. Taguchi analysis indicated that initial moisture content exerted the greatest influence on compost maturity, followed by initial C/N ratio and crushed straw particle size. This study provides an important reference for the utilization of compost derived from a mixture of livestock manure and straw., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Aiming to assess the efficiency of white clove (WC) as an alternative nitrogen source for composting and to facilitate the utilization of orchard waste, WC as compared with chicken manure (CM) was aerobically composted with apple tree leaves (ATL) in initial C/N ratios of 25(R25), 30(R30) and 35(R35). The results show that WC facilitated the rapid and harmless treatment of ATL with the compost temperature above 55°C for more than 3 days. After composting, for all final products, organic matter content was 69.9%-72.9%, electrical conductivity (EC) 1.48-2.31 ms cm -1 , germination index (GI) more than 80% and C/N ratios less than 20. Among all treatments, the product from R30 was most nutrient-rich. Compared with CM, WC facilitated the harmless treatment of ATL and required less time for high quality compost production. It is concluded that WC is an excellent replacement for animal manure as a nitrogen source in field composting of orchard waste in areas with limited transportation. WC and ATL can produce high quality organic fertilizer and initial C/N ratio of 30 is recommended.

The harvesting of hops (Humulus lupulus L.) generates large amounts of nutrient-rich leaves that can be used in composting mixtures to add value to other organic resources on the farm. In this study, hop leaves were mixed with cow manure and wheat straw in several combinations with the aim of establishing guidelines on how farmers can manage the raw materials and better use these valuable organic resources. The composting process was monitored and the quality of the composts evaluated in relation to the effects on lettuce (Lactuca sativa L.) grown in pots over two consecutive cycles. The mixture of hop leaves with cow manure produced a stable compost after nine months of composting which may be used in horticultural crops, irrespective of the proportion of raw materials, due to their low and similar C/N ratios. However, when using mixtures of leaves and straw in proportions of less than 2:1, the composts did not mature properly, showing high C/N ratios. Their application to the soil led to a strong reduction in plant tissue N concentrations, due to biological N immobilization, which significantly reduced lettuce dry matter yield. Thus, to reduce composting time and increase the quality of the compost, the ratio leaves/straw should be as high as possible, at least 2:1. Alternatively, either the composting process should take longer, or the poorly-matured compost be applied far in advance of sowing a crop so that complementary biological processes can take place in the soil, as recorded in the second cycle of lettuce. Ash from hop stems did not benefit the composting process and proved itself not to be worth using in mixtures., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Accumulating evidence indicates that the functional rather than taxonomic composition of microbial communities is closely correlated to local environmental factors. While composting is a widely accepted practice, specific knowledge of how fungal functional groups interact during the composting process remains limited. To address this, the impact of the initial C/N ratio of composting material on fungal community was analyzed in order to reveal the succession of functional diversity. Compared with the raw materials, the final composting product significantly reduced the relative abundances of plant and animal pathogens. Abundances of plant and animal pathogens, as well as dung saprotrophs, were negatively correlated with compost maturity, while abundances of wood saprotrophs exhibited positive correlations. Specific OTUs that showing highly abundant in each treatment were expected to compete for environmental preferences (niches) and/or interact with each other in positive (facilitative) ways. OTU2 (wood saprotroph) exhibiting the highest occurrence was negatively related to OTU7 (animal pathogen) and OTU4 (plant pathogen) during the mesophilic phase. Taken together, high-efficiency composting is represented as pattern variations of fungal community with a process of gradual decline of plant and animal pathogens as well as dung saprotrophs., (Copyright © 2020 Elsevier B.V. All rights reserved.)

This study aimed to investigate; composting of toxic weed Parthenium with cow dung in (2:1, and 1:1 ratio); and the changes in Escherichia coli and Salmonella population; as well as the antimicrobial property of ready compost. Organic carbon decreased by 45-52% while total nitrogen, total potassium, available phosphorus increased by 1.87- to 3.21-, 1.65- to 1.83-, and 4.03- to 3.33-folds, respectively in Parthenium setups. Germination index value (110-132%) indicates no phytotoxicity of composted Parthenium. E. coli reduced by 6.87 to 6.90 log population (<1000 CFU g -1 , safe limit) while Salmonella was in non-detectable limit in compost samples. Results of the antimicrobial test indicate a strong biocidal activity by non-sterilized compost extract against plant pathogens Xanthomonas citrus, Xanthomonas campestris, and Erwinia carotovora. Xanthomonas spp. It is concluded that thermophilic composting could convert Parthenium into a product with biomanure and biopesticide property for sustainable agriculture production., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

As the composting industry develops rapidly in the world, the compost producers have focused on the efficiency of energy utilization in production without restricting the quality of compost in the forced ventilation systems. Therefore, this experimental study quantified the impacts of initial C/N ratio on aeration requirement and energy consumption due to aeration for reactor composting of rose pomace through kinetics of the process using fifteen 100-l composting reactors. The results of the study showed that initial C/N ratio significantly affected decomposition rate, compost maturity, and dry matter losses and organic matter losses (P < 0.05). The maximum decomposition rate (0.072 day -1 ) and the highest degree of progression of the composting process existed at the mixture with initial C/N ratio of 24.26. The results underlined the importance of the initial C/N of composting of rose pomace in terms of energy consumption due to aeration. In particular, more mature compost within a short time can be obtained when composting was operated with a C/N ratio of 23.7-25.8 in the expense of requiring more airflow rate, fan power, and energy consumption by aeration fan per composting material.

Sewage sludges are problematic due to the constant increase of urban population. The high level of organic matter in sludges can be valorized by co-composting with green waste. Many chemical changes occur in the compost maturation process, resulting on stabilized organic matter by humification which is recoverable as soil amendment. In this way, the knowledge of organic matter stability and maturity of compost is essential. However, estimation of chemical parameters allowing the management of compost quality usually need complex time consuming laboratory measurements. Indeed, there is not yet rapid, simple and robust method for their on site assessment at the moment. Among usual parameters used to monitor compost evolution, the C/N ratio is a fundamental chemical parameter. The aim of this work is the estimation of the C/N ratio using a Partial Least Squares regression based on UV and fluorescence spectroscopic data and pH from compost water extracts at various steps of composting process and measured on site. A mathematical linear model is established based on selected data (pH, spectroscopic indices) resulting on average relative error for C/N estimation of 5.26% (range between 0.5% min. and 9.5% max.). This tool leads to a rapid and simple on site estimation of the compost stabilization, allowing qualification of the end-product resulting on a global spectroscopic index of stability., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The carbon to nitrogen ratio (C/N) is well known for its importance in the composting process, however the fiber degradation and humification associated with enzymatic activity and microbial variation derived from different C/N ratios are poorly studied. Here, we designed two treatments of chicken manure with 15% (initial C/N ratio 9.61) and 50% (initial C/N ratio 17.3) rice husk to adjust the moisture of mixtures for turning feasibly by towable fertilizer turner in industrial level. Compared to the C/N ratio 9.61, the suitable C/N ratio of 17.3 significantly enhanced the composting efficiency and the final germination index (23.7%). Moreover, the suitable C/N ratio increased the relative abundance of Bacilli, which played an important role during the mesophilic and thermophilic phases. Bacilli abundance was related to cellulose and β-glycosidase activities, thus improved fiber degradation and humification. This study not only seeks a swift method in industrial level to process chicken manure but also provides insight into the enzymatic activity of microbial community related to high-efficient composting., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The recalcitrance of green waste, caused by its high lignocellulose content, is a technical challenge for accelerating green waste composting. Adjusting the initial ratio of total carbon and total nitrogen (TC/TN) to the optimal range of 25-30:1 is a common strategy to accelerate the composting process. However, because microorganisms can only utilize hydrosoluble nutrients directly, we investigated whether maintaining the ratio of hydrosoluble carbon and hydrosoluble nitrogen (HC/HN) within the optimal range through continuous urea addition can better accelerate green waste composting. We conducted a pilot-scale composting experiment, in which the aforementioned maintaining started at the beginning of composting, or after the thermophilic phase. The results demonstrate that maintaining the optimal HC/HN ratio starting at both periods can, to some extent, direct the TC/TN ratio toward 25-30:1, and can also significantly improve heat generation, pH, lignocellulose degradation, and humification. Moreover, lignin degradation was improved by 3.15-7.33%, cellulose degradation was improved by 6.48-8.15%, and carbon content of humus was increased by 7.19-16.13%. Although the maturity assessment showed that none of the final compost reached maturity within the limited experimental period (48 days), based on the promoted lignocellulose degradation and humification, we conclude that maintaining the HC/HN ratio within the optimal range is a more efficient method to accelerate green waste composting, compared to the initial TC/TN adjustment only once., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The aim of this work was to investigate how the initial C/N ratio during composting of chicken manure/corn stover mix affected the succession of dominant bacteria in the mix which led to the reduction of the total losses of N and C in the composting process. 16S rDNA sequencing indicated that the succession of predominant bacteria was significantly affected by the temperature and the initial C/N ratio during composting. Redundancy analysis showed that higher C/N appeared to promote the relative abundance of nitrogen fixing bacteria Thermoactinomyces, Planifilum, Flavobacterium, Bacillaceae, Pseudomonas,Sphingobacterium, Paenibacillus, Bacillus and Thermobifida, while compressing the denitrifying bacteria Pusillimonas, Ignatzschineria, Alcanivorax, Cerasibacillus, Truepera and Erysipelothrix. C/N ratio of 30:1 yielded the least C/N losses in the composting process, indicating that adjustment to the initial C/N ratio could affect nitrogen transforming bacteria to reduce the total losses of N and C and improve compost quality., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Sludge composting is increasingly adopted due to its end product for application as a soil nourishment amendment. Although the ratio of C/N is significant in the quality and process of composting, little information has been obtained from the effects of nutritional energy (carbon and nitrogen) on the fate of antibiotic resistance genes (ARGs) during sludge composting. Dynamic variations of ARGs, microbial community as well as functional characteristics during composting of sludge were investigated in this study. Three levels of carbon to nitrogen (20:1, 25:1 and 30:1) were developed for the composting of sludge with fermented straw plus a control which was just sewage sludge (C/N = 9.5:1). A novel finding of this work is that the highest initial C/N ratio (30:1) could prolong the thermophilic period, which was helpful to reduce some target ARGs. Some ARGs (sul1, sul2, and aadA1) had negative correlation with multiple metabolic pathways, which were difficult to remove., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A consortium of key bacterial taxa plays critical roles in the composting process. In order to elucidate the identity and mechanisms by which specific bacterial species drive high-efficiency composting, the succession of key bacterial consortia and extracellular enzymes produced during the composting process were monitored in composting piles with varying initial C/N ratios. Results showed that C/N ratios of 25 and 35 enhanced composting efficiency through elevated temperatures, higher germination indices, enhanced cellulose and hemicellulose degradation, and higher cellulase and dehydrogenase activities. The activities of cellulase and β-glucosidase, cellulase and protease, and cellulase and β-glucosidase exhibited significant relationships with bacterial community composition within the mesophilic, thermophilic, and mature phases, respectively. Putative key taxa, linked to a higher composting efficiency, such as Nonomuraea, Desemzia, Cellulosimicrobium, Virgibacillus, Clostridium, and Achromobacter, exhibited significantly positive relationships with extracellular enzyme activities, suggesting a significant contribution to these taxa to the development of composting maturity., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Worldwide, large amounts of food are wasted every year. Reducing of food waste at European level is taken very seriously and it has been adopted even a target of reducing the amount of food waste in half until 2030. In many countries of the European Union, food wastes are composted, while in countries like Romania, the composting is too little used or not at all, but efforts are being made to apply this process. Food waste composting should take place both at the composting plants and housing level. An important step before starting the composting process is to establish an appropriate recipe. Therefore, the aim of this paper is to develop a composting recipe starting from investigation of food waste like peel and pomace of fruits (apple, banana, orange, and kiwi) and vegetables (potato, cabbage, and carrots) which are very common in waste generated at the housing level. The most important physical-chemical parameters were investigated in this study. Results show that pH of fruit waste is acid (4.0-5.0), while for vegetable waste, the pH is slightly higher (between 6.0 and 6.5). For all types of food waste, a very high moisture content (80-90%) was registered, while the nitrogen content is below 1%. Considering that C/N ratio is one of the most essential parameters, for the process to be carried out in good conditions, we have used regression analysis in order to determine the amounts of fruits and vegetable waste necessary to obtain different C/N ratios.

This study was conducted to determine the effects of C/N ratio and free air space in co-composting of sewage sludge with tomato stalk and dairy manure. Experiments were carried out in 100 L of stainless steel aerobic compost reactors with full automation system and monitored for 32 days. The temperature was controlled according to the Rutgers strategy. During the composting process, moisture content, organic matter content, pH, electrical conductivity, total carbon, total nitrogen, C/N ratio, total phosphorus, potassium, NH 4 + -N and heavy metals contents were determined. For evaluation of the stabilization process, organic matter, dry matter, ammonia and mass and volume losses and temperature index values were taken into consideration. The temperature pattern in the mixtures with dairy manure increased rapidly and reached higher levels depending on dairy manure ratio. The highest organic matter loss was 57.87%, which was in the mixture with a C/N ratio of 20 and a free air space ratio of 37%.3 - -N and heavy metals contents were determined. For evaluation of the stabilization process, organic matter, dry matter, ammonia and mass and volume losses and temperature index values were taken into consideration. The temperature pattern in the mixtures with dairy manure increased rapidly and reached higher levels depending on dairy manure ratio. The highest organic matter loss was 57.87%, which was in the mixture with a C/N ratio of 20 and a free air space ratio of 37%., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Peat is an unrenewable resource. Compost can partially replace peat in the growing seedling substrates due to its high electrical conductivity (EC), bulk density (BD), and pH. This study aimed to assess the potential of substituting peat for seedling substrate with compost made from a mixture of agricultural and agro-industrial wastes. Four compost piles (C1–C4) were constructed as follows: C1: a 1:1:1.5 weight ratio mixture of filter mud, mushroom waste, and date-palm fronds, while C2–C4: a 0.5:1 weight ratio mixture of either bagasse, cutting grassland, or date-palm fronds and cattle dung. After four months of decomposition, the compost's physical, chemical, and biological properties were estimated in comparison to commercial compost (CC), peatmoss (PM), and their ideal ranges (IR) for seed germination and seedling growth. Composts differed significantly in their physical and chemical properties. Some composts revealed property values within the IR. In comparison to PM, Composts have a lower C/N ratio and organic matter, along with higher BD, EC, and pH. Cattle manure enhanced organic matter and carbon, total nitrogen and potassium, and ammonium levels, and reduced ash levels in C2–C4 compared to filter mud in C1. In winter 2018 and 2019, C1–C4 substrates were compared with CC and PM substrates to determine their suitability for producing crisp lettuce 'Big Bell' seedlings under plastic-house conditions. Substrates had significant effects on lettuce seedling traits. Shoots of C2–C4 substrate seedlings grew more rapidly than those of other substrate seedlings due to the increased length and diameter of their stem and leaf area. [ABSTRACT FROM AUTHOR]

The increasing invasion of Rugulopteryx okamurae algae along the coast of southeastern Spain has prompted efforts to explore its potential as a resource. Consequently, composting this alga is considered a viable solution for agricultural applications. This study investigates the composting process of mixtures of R. okamurae seaweed with plant residues and characterizes the final compost for its use as a substrate and/or source of nutrients to determine the most effective composition of the mixture. The composting process was conducted using varying proportions of seaweed (100%, 30–35%, and 15%) combined with plant residues (from vegetable plants, fruits, and gardens) and included both washed and unwashed seaweed. The first trials revealed challenges associated with Rugulopteryx okamurae, such as a low C/N ratio and algae washing. Consequently, a second trial was conducted to optimize the mixtures, aiming for a C/N ratio close to 30. Additionally, it was decided not to wash the algae to reduce the electrical conductivity (EC) in the mixtures. The findings indicate that the composting process remains unaffected by high electrical conductivity when algae are unwashed. However, washing the algae before composting did affect the compost quality, as the composts with washed algae with garden waste (SwP 34.0 dS m−1) had a lower electrical conductivity (EC) than did the unwashed composts with garden waste (SP 51.6 dS m−1 and SFP 64.9 dS m−1). On the other hand, the compost-only horticultural and garden waste (FHP 43.7 dS m−1) had a high EC; therefore, the EC was not increased with low proportions of unwashed algae, as was seen with the compost with 15% unwashed algae (SFHP 47.6 dS m−1). The other quality parameters were not affected by the absence of algae washing at the beginning of the composting process. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) generation during composting not only leads to losses of nitrogen (N) but also reduces the agronomic values and environmental benefits of composting. This study aimed to investigate the effect of the C/N ratio on N2O emissions and its underlying mechanisms at the genetic level during the composting of vegetable waste. The experiment was set up with three treatments, including low C/N treatment (LT, C/N = 18), middle C/N treatment (MT, C/N = 30), and high C/N treatment (HT, C/N = 50). The results showed that N2O emission was mainly concentrated in the cooling and maturation periods, and the cumulative N2O emissions decreased as the C/N ratio increased. Specifically, the cumulative N2O emission was 57,401 mg in LT, significantly higher than 2155 mg in MT and 1353 mg in HT. Lowering the C/N ratio led to increasing TN, NH4+-N, and NO3−-N contents throughout the composting process. All detected nitrification-related gene abundances in LT continued to increase during composting, significantly surpassing those in MT during the cooling period. By contrast, in HT, there was a slight increase in the abundance of detected nitrification-related genes but a significant decrease in the abundance of narG, napA, and norB genes in the thermophilic and cooling periods. The structural equation model revealed that hao and nosZ genes were vital in N2O emissions. In conclusion, increasing the C/N ratio effectively contributed to N2O reduction during vegetable waste composting. [ABSTRACT FROM AUTHOR]

THIS RESEARCH aims to study the degree and duration of the thermophilic phase by changing the available carbon source to reduce the period of composting within a fully equipped reactor with a controllable stirring and ventilation unit and its impact on the quality of the produced compost. The first stage analysis of raw materials used physically and chemically. Then determined the need for nitrogen supplements and the appropriate particle size of the nutrient. Initially, the experiment contained six treatments obtained by mixing agricultural plant residues (pepper and broccoli) with cow manure in different mixing ratios: 95:5, 90:10, 85:15, 60:40, 50:50 and 10:90 respectively. Then from the resulting data of the first experiment, the mixing ratios of 50:50 and 60:40 were chosen as the best ratios that showed the highest temperatures, then other parameters were added to them, which are (20 ml used oil and 20% compost as inoculum). The addition of used oil (50:50) resulted in the record of the highest temperature of 59°C and the thermophilic phase lasted for 5 days. However, with ratios (60:40) recorded 56°C and the thermophilic phase lasted for 4 days and the composting process was completed within 18 days. While when the inoculum was added with (50:50) ratios, the temperature reached 52.7°C and with (60:40) it reached 51°c and the compost was completed ripening after 25 days from the beginning of the experiment. [ABSTRACT FROM AUTHOR]

Composting degradable organic matters with chemical fertilizers produces stable material with the aid of organisms and makes nutrients readily available to plants. A field study was carried out for incorporation of the urea and KOH treatments on composting fresh cattle manure, wheat straw, sawdust, and dried leaves to evaluate the decomposition rate during four months. The mineralization of the organic wastes as increased in microbial biomass carbon (MBC) and organic matter (OM) loss was higher in urea treatments, in contrast with KOH treatments which need more time for optimum decomposition. Laccase activity reduced in the manure but increased in other organic wastes and in the urea treatments. Water-soluble carbon (WSC) decreased in all organic wastes, particularly in urea-treated manure. The fluctuation of pH and electrical conductivity (EC) were observed for four months but increased at the end of the experiment. Total organic carbon (TOC) reduced, and total nitrogen (TN) has risen, especially in the presence of urea treatments; so, the C/N ratio significantly decreased and the trend of composting progressed overtime. Insufficient technical planning in composting has led to changed approaches to increase elements availability with the management of existing plantations. The successive applications of urea were observed to enhance the rate of organic wastes decomposition than KOH treatments. This study further recommends application of urea and KOH with degradable organic materials in which this method should be improved with the ability to mineralize nutrients rapidly, which could make them advantageous to crop growth. [ABSTRACT FROM AUTHOR]

Purpose: In this study, we aim to investigate the suitability of five samples of compost extracted at various concentrations by testing for their phytotoxic response on Lactuca sativa L. We analyze relevant parameters with regards to the quality of the compost. By doing this, we hope to contribute to the attainability of clean, high-value organic fertilizer from local food waste production. Method: We set up a mini composting pilot where raw materials were classified, chopped into bits, and finally mixed. They include residues of Solanum tuberosum (potatoes), Zea mays (corn), Musa Paradisiaca (bananas), Allium cepa (onions), Lactuca sativa (lettuce), Daucus carota (carrots), Solanum lycopersicum (tomatoes), as well as fruits such as Passiflora edulis (passion fruit), Carica papaya (papaya). Composting was run over a period of 90 days. We then measured several bromatological analyses of compost. For phytotoxicity tests of compost relative seed germination (RSG), relative radicle growth (RRG) and Germination Index GI on L. sativa were measured. Results: The prepared compost showed the following parameters: pH (8.6), OM (21.4%), C/N (11.59), EC (7.24 dS/m), Total N (1.72%), P (325.6 ppm), Al (0.1 cmol.kg-1) K (41 cmol.kg-1), Ca (8.12 cmol.kg-1), Mg (5.62 cmol.kg-1), Na (0.76 cmol.kg-1). Minor elements appeared in acceptable ranges, and do not pose any risk. Besides, the compost showed a germination rate of 112.6% on L. sativa, which allowed us to validate its high maturity. Conclusion: The compost produced stands out for its quality and efficiency, due to its low phytotoxicity, specific mixture of the materials and the processing method. The mature compost produced represents a valuable material for the acidic and nutrient-poor soils of the Colombian Piedmont. [ABSTRACT FROM AUTHOR]

Purpose: Co-composting of mango by-products and biogas solid residue eliminates some shortcomings of composting these wastes separately. Specifically, co-composing solves the problem of the low pH values in mango by-products while enhances biodegradable organic matter of biogas solid residues. However, no research report is available on co-composting of mango by-products (MB) and biogas solid residue (BR). Method: This study established three in-vessel lab-scale composting bins with 3 different C/N ratios, including Bin 1: 27.4/1 (156 kg MB + 144 kg BR); Bin 2: 30.23/1 (193 kg MB + 107 kg BR); and Bin 3: 37.7/1 (224 kg MB + 76 kg BR). The raw compost materials underwent 57 days of incubation, including 36 days of raw incubation and 21 days of mineralization. Results: Bin 3 containing larger amounts of mango by-products and less amounts of biogas residue showed a higher percentage of remaining carbon in the final products (17.97%), lower nitrogen loss (17%), and showed 0.5% increase in available P2O5 content, compared to the other bins. From 300 kg of initial raw material, the final compost mass in Bin 1, Bin 2, and Bin 3 were 26.2 kg, 32.7 kg, and 88.1 kg, respectively. Conclusion: Resultantly, an initial C/N ratio of 37.7/1 could be suggested in the aerobic co-composting of biogas residue with mango by-products. [ABSTRACT FROM AUTHOR]

Purpose: In this study, we aim to investigate the suitability of five samples of compost extracted at various concentrations by testing for their phytotoxic response on Lactuca sativa L. We analyze relevant parameters with regards to the quality of the compost. By doing this, we hope to contribute to the attainability of clean, high-value organic fertilizer from local food waste production. Method: We set up a mini composting pilot where raw materials were classified, chopped into bits, and finally mixed. They include residues of Solanum tuberosum (potatoes), Zea mays (corn), Musa Paradisiaca (bananas), Allium cepa (onions), Lactuca sativa (lettuce), Daucus carota (carrots), Solanum lycopersicum (tomatoes), as well as fruits such as Passiflora edulis (passion fruit), Carica papaya (papaya). Composting was run over a period of 90 days. We then measured several bromatological analyses of compost. For phytotoxicity tests of compost relative seed germination (RSG), relative radicle growth (RRG) and Germination Index GI on L. sativa were measured. Results: The prepared compost showed the following parameters: pH (8.6), OM (21.4%), C/N (11.59), EC (7.24 dS/m), Total N (1.72%), P (325.6 ppm), Al (0.1 cmol.kg−1) K (41 cmol.kg−1), Ca (8.12 cmol.kg−1), Mg (5.62 cmol.kg−1), Na (0.76 cmol.kg−1). Minor elements appeared in acceptable ranges, and do not pose any risk. Besides, the compost showed a germination rate of 112.6% on L. sativa, which allowed us to validate its high maturity. Conclusion: The compost produced stands out for its quality and efficiency, due to its low phytotoxicity, specific mixture of the materials and the processing method. The mature compost produced represents a valuable material for the acidic and nutrient-poor soils of the Colombian Piedmont. Research Highlights The generation of agri-food waste is a worldwide problem, especially in Latin America. Waste treatment technologies recover valuable materials. Composting as a circular economy strategy that contributes to sustainable food security. The compost can be highly convenient for its application in acidic and nutrient-poor soils.

Background: As objective of this study was focused on efficacy of composting of a recalcitrant organic waste material, co-composting of coir pith with cow manure and rice bran was endeavored to evaluate influence of initial C/N ratios, i.e., 30, 25, and 20, on physico-chemical changes, e.g., temperature, pH, organic matter (OM) degradation, and total nitrogen (TN) losses. Results: Results showed that OM and TN losses were significantly affected by C/N ratio (p < 0.05), whereas C/N ratio played insignificant role on temperature and pH evolution within the pile (p > 0.05) during composting process. OM and TN losses were highest within the first 2 weeks of thermophilic phase. Through the composting process, pile with 25 C/N ratio showed the highest biodegradation rate constant of organic matter (k = 0.309 dayâ1 ) and the highest TN losses (41.9%), while pile with C/N ratio of 30 showed the lowest N loss (â7.3%). However, for all three compost piles, maturity, as indicated by the pile temperature converging to the ambient temperature, was attained within 1 month post-composting. Conclusion: Results suggested that simple pile turning yielded effective co-composting of coir pith under comparatively low C/N ratio. Considering the composting performance and the amount of coir pith to be utilized, the initial C/N ratio of 30 was considered suitable for coir pith composting.

Purpose Composting has the potential to recycle wastes as a means of conserving natural resources. The study was aimed at examining feasibility of producing nutrient-enriched composts from pest infested cocoa pods with chemical amendments and using manure composts as a fertilizing material in cocoa seedling nursery. Methods Cocoa pod waste was composted in static vessels, aerobically, with chemical enrichments (triple super phosphate charged at 0.4% P or urea charged at 0.8% N or poultry manure charged at 22%) along with a control at the Cocoa and Coconut Institute, Papua New Guinea. The reaction (pH) of the composting mixtures (pH) and macronutrients dynamics was monitored at periodic intervals. Effect of soil incorporation of cocoa pod manure composts at 10 g kg-1 was assessed on the growth and foliar concentration of macro-nutrients in hybrid cocoa seedlings. Results In the finished manure composts, dry matter loss ranged from 30.6 to 63.3%; greatest in composting mixtures charged with super phosphate and poultry manure. Besides, super phosphate enriched mixture lost small fraction of initial N (6.6%) compared to un-enriched cocoa pod waste (30.2%). Composting mixtures with greater pH values during composting process showed higher losses of N. Super phosphate charged manure compost outperformed the control, in terms of C/N ratio and concentration of macro-nutrients (P, K, Ca, Mg and S). Quality parameters for all the manure composts conformed to the Canadian Compost Guidelines indicating satisfactory standards. Waste cocoa pods enriched with superphosphate did not show any deleterious effects on cocoa seedlingsâ growth, rather, improved plant height, dry matter production and foliar N concentration. Conclusion Waste cocoa pods, co-composted with triple super phosphate and poultry manure, produced composts of desirable quality and can be effectively used to fertilize the cocoa seedlings.

Even though sewage sludge (SS) contains a high level of pollutants, it is rich in essential plant nutrients and has the potential to enhance soil fertility. However, the SS must be further treated through pre-composting plus vermicomposting to make it safe for use on food crops. More research and data are needed to determine how different carbon-to-nitrogen ratios (C/N) affect the feasibility and quality of composting vs vermicomposting of SS. Therefore, in this study we comprehensively evaluated the feasibility and end-product quality of compost and vermicompost produced from SS under different C/N ratios. SS was mixed with pelletized wheat straw (PWS) at various proportions to produce C/N ratios of 6:1, 18:1, 28:1, and 38:1, then pre-composted for 14 days followed by vermicomposting using the earthworm Eisenia andrei for 120 days. Agrochemical properties were measured at 0, 30, 60, 90, and 120 days. Results revealed significantly higher levels of agrochemicals in vermicompost compared to compost, including total potassium (37–88%) and magnesium (4.3–12%), nitrate nitrogen (71–98%), available potassium (53–88%), available phosphorus (79%), available magnesium (54–453%), available boron (48–303%), and available copper (2.5–82%). However, lower levels of ammonium nitrogen by (59–85%), available iron (2.3–51.3%), available manganese (29.7–52.2%), available zinc (10.5–29.8%), total carbon (0.75–4.5%), and total nitrogen (1.6–22.2%) were measured. Comparison of the various C/N ratios, showed that vermicompost with an 18:1 C/N ratio outperformed compost and demonstrated the highest earthworm population (165 pieces/kg). Thus, vermicomposting SS at an 18:1 C/N ratio is strongly recommended as a sustainable technology for producing high-quality vermicompost from SS.

Composting is the oldest and most natural form of organic material recycling. Technological parameters are very important because when the process is unbalanced, other gases are produced, some of which have objectionable odours (NH3). Sewage sludge is a valuable material that has accumulated large amounts of nitrogen and phosphorus, which can contribute to improving soil quality. Optimal composting and vermicomposting conditions (C/N ratio, pH, and moisture) can reduce the emissions of gaseous pollutants in the environment. Experimental studies have shown that the volume of ammonia emitted into the environment during vermicomposting of sewage sludge is significantly lower (3 mg/m³ concentration was reached on the 28th day) than that resulting from traditional composting (3 mg/m³ concentration was reached on the 56th day). Vermicomposting of sewage sludge preserves higher amounts of total nitrogen (12.52 mg/kg) compared to traditional composting (10.35 mg/kg). [ABSTRACT FROM AUTHOR]

Composting is the oldest and most natural form of organic material recycling. Technological parameters are very important because when the process is unbalanced, other gases are produced, some of which have objectionable odours (NH3). Sewage sludge is a valuable material that has accumulated large amounts of nitrogen and phosphorus, which can contribute to improving soil quality. Optimal composting and vermicomposting conditions (C/N ratio, pH, and moisture) can reduce the emissions of gaseous pollutants in the environment. Experimental studies have shown that the volume of ammonia emitted into the environment during vermicomposting of sewage sludge is significantly lower (3 mg/m3 concentration was reached on the 28th day) than that resulting from traditional composting (3 mg/m3 concentration was reached on the 56th day). Vermicomposting of sewage sludge preserves higher amounts of total nitrogen (12.52 mg/kg) compared to traditional composting (10.35 mg/kg).

The use of disposable diapers is increasing every year, increasing generated diaper wastes every year. In Surabaya, diaper wastes have become an important issue when they are not treated properly. These diaper wastes will end up in water bodies and cause pollution. One of the technologies that can be used to treat diaper wastes is composting. Disposable diaper wastes consist of high lignocellulose and C content. It is necessary to mix diaper wastes and other wastes with high N content as a co-substrate, so that the optimum C/N ratio of composting can be achieved. In this research, vegetables wastes were used. The Objective of the research was to determine the effect of vegetable wastes adding as a co-substrate in composting of disposable diapers and volatile solid (VS), C-organic, and Total Nitrogen (TN) content changed during the composting process. The research was carried out with three variables mixtures of diaper wastes and vegetable wastes. Two control consist of 100% diaper wastes and 100% vegetables wastes. The Total weight of raw materials was 10 kg for each reactor. The composting process is carried out aerobically with a composting time of 60 days. The results showed that vegetable wastes have the potential to be used as a co-substrate for diaper wastes. The content of C-organic, VS and total nitrogen decreased. All of the parameters include C/N ratio meet the Indonesian Standard of compost.

The use of disposable diapers is increasing every year, increasing generated diaper wastes every year. In Surabaya, diaper wastes have become an important issue when they are not treated properly. These diaper wastes will end up in water bodies and cause pollution. One of the technologies that can be used to treat diaper wastes is composting. Disposable diaper wastes consist of high lignocellulose and C content. It is necessary to mix diaper wastes and other wastes with high N content as a co-substrate, so that the optimum C/N ratio of composting can be achieved. In this research, vegetables wastes were used. The Objective of the research was to determine the effect of vegetable wastes adding as a co-substrate in composting of disposable diapers and volatile solid (VS), C-organic, and Total Nitrogen (TN) content changed during the composting process. The research was carried out with three variables mixtures of diaper wastes and vegetable wastes. Two control consist of 100% diaper wastes and 100% vegetables wastes. The Total weight of raw materials was 10 kg for each reactor. The composting process is carried out aerobically with a composting time of 60 days. The results showed that vegetable wastes have the potential to be used as a co-substrate for diaper wastes. The content of C-organic, VS and total nitrogen decreased. All of the parameters include C/N ratio meet the Indonesian Standard of compost. [ABSTRACT FROM AUTHOR]

Lignocellulosic materials have a complex physicochemical composition and structure that reduces their decomposition rate and hinders the formation of humic substances during composting. Therefore, a composting experiment was conducted to evaluate the effects of different C/N ratios on lignocellulose (cellulose, hemicellulose and lignin) degradation and the activities of corresponding enzymes during aerobic composting. The study had five C/N ratios, namely, T1 (C/N ratio of 15), T2 (C/N ratio of 20), T3 (C/N ratio of 25), T4 (C/N ratio of 30) and T5 (C/N ratio of 35). The results showed that treatments T3 and T4 had the highest rate of degradation of cellulose and hemicellulose, while treatment T3 had the highest rate of degradation of lignin. Among the five treatments, treatment T3 enhanced the degradation of the lignocellulose constituents, indicating a degradation rate of 6.86–35.17%, 15.63–44.08% and 31.69–165.60% for cellulose, hemicellulose and lignin, respectively. The degradation of cellulose and lignin occurred mainly at the thermophilic and late mesophilic phases of composting, while hemicellulose degradation occurred at the maturation phase. Treatment T3 was the best C/N ratio to stimulate the activities of manganese peroxidase, lignin peroxidase, polyphenol oxidase and peroxidase, which in turn promoted lignocellulose degradation. [ABSTRACT FROM AUTHOR]

The objective of this study was to treat dairy sludge through composting, using the combination of natural resources available in the company itself, with regard to the parameters temperature, pH, humidity, C/N ratio and volume and weight. Seven treatments consisting of pure dairy sludge and mixtures of sludge with other residues (bovine manure, grass pruning and boiler ash) were evaluated. For this, a completely randomized design was used, with seven treatments and three replications. Over 123 days of evaluation, the variation in temperature in the compounds remains only in the mesophilic phase. At the end of monitoring, the Ph values were 5.14; 7.16; 9.60; 7.54; 9.96; 10.06 and 9.91 for treatments T1, T2, T3, T4, T5, T6 and T7, respectively. Regarding the moisture of the treatments, with the exception of T1, the evaluated treatments presented values close to those considered adequate for composting. In turn, T4 had a better C/N ratio than the other treatments (7.75). Among the final compounds, it was found that treatments 1 and 4, there were greater reductions in volume (62% and 58.18%) and weight (52.45% and 51.33%) respectively. It is concluded that of the compounds produced with dairy sludge and their combinations, T4 is responsible for the best results in terms of weight and volume reduction, pH, moisture content and C/N ratio. The addition of grass to dairy sludge is recommended as the most suitable technique for reducing and adjusting these parameters. [ABSTRACT FROM AUTHOR]

Aeration is a critical factor for composting which provides oxygen, controls temperature, and removes excess moisture for the biological processes. An experiment was conducted to study the effect of partially aerated static pile approach for ex-situ composting of paddy straw on physical, chemical, C/N ratio and microbial properties of the compost at 60 and 150 days. The pits containing paddy straw mixture were equipped with perforated horizontal and vertical pipes for aeration and water supply. The pits were covered with different materials such as plastic sheets, farmyard manure (FYM), soil, rugs, paddy straw, and 'without cover' to retain the moisture during composting. Covering with FYM, soil, and paddy straw resulted in higher degradation in terms of C/N ratio and higher nutrient content of compost. The use of FYM as cover during composting resulted in the highest values for N(1.9%),P(0.63%), K(2.4%), micronutrients [Fe(202ppm), Zn(288ppm), Mn(1626ppm) and Cu(514ppm)], bacteria, fungi, and actinomycetes count (8.86, 5.54 and 6.94 log CFU/gm, respectively) and highest degradation with C/N ratio of 17.0 after 150 days. It was concluded that partial aeration is an economic option to reduce period of composting from 9 to 5 months with FYM. This practice ensures an opportunity for farmers for ex-situ composting of paddy straw as an alternative to burning. [ABSTRACT FROM AUTHOR]

A dramatic increase in the amount of chicken manure is posing a great challenge on the social community, ecological environment, and human health, as the growing demand of chicken meat and eggs in China. Fortunately, composting process is an effective, sustainable, economic and natural way to recycle the decomposed organic materials, with an emphasis on the manure treatment prior to land application. Nevertheless, there are usually lots of odor emissions during the composting of nitrogen-rich chicken manure. The C/N ratio of raw materials markedly determines the compost maturity and the odor emissions during composting. At present, lots of previous studies focused on the effect of C/N ratio on the compost maturity and quality. However, only a few reports paid attention to the odor (NH3 or H2S) emissions during chicken manure composting. In this study, three C/N ratios, including 14, 18 and 22, were selected from the co-composted chicken manure and cornstalks as the bulking agent, to improve the compost quality, while decrease the odor emissions. An attempt was made to explore the comprehensive effect of C/N ratio on maturity and odor emissions (NH3 and H2S) during chicken manure composting. The aeration was in an intermittent mode (Sated 30 min, stopped 30 min), and the rate was 0.2 m³/h. The composting lasted 35 days, where the sampled on the day of 0, 3, 7, 14, 21, 28, 35, respectively. The basic physicochemical and maturity indexes were measured, including temperature (T), oxygen (O2), inorganic nitrogen content (NH+4-N, NO-3-N), pH value (pH), Electrical Conductivity (EC), C/N ratio, Germination Index (GI), and the element content (C, N and S). Odor emissions (NH3 and H2S) were continuously monitored daily. A canonical correspondence analysis (CCA) was also used to analyze the microbial community composition, as well as their correlation with physicochemical indexes and odor emissions. The results showed that the final compost with the C/N ratio of 14 was not mature, while both the treatment with the C/N ratios of 18 and 22 reached the maturity standard. In terms of odor emissions, the C/N ratio of 18 treatment had the highest NH3 emission, because of the higher degradation of organic matter. When the C/N ratio ranged from 18 to 22, the NH3 emission and total nitrogen (TN) loss decreased with the C/N ratio increased. In addition, the cumulative H2S emission and the total sulfur (TS) loss were the highest in the C/N ratio of 14 treatment, while those in the C/N ratio of 18 and 22 treatments greatly decreased, indicating no significant difference. Moreover, the C/N ratio of 18 treatment had the highest microbial diversity, compared with other two treatments during the whole composting period. Furthermore, the microbial community compositions in the C/N ratios of 14 and 18 treatments (Firmicutes) were significantly different from those in the C/N ratio of 22 treatment (Actinobacteria and Firmicutes). More importantly, the CCA showed high temperature, high pH, and hypoxic environment can be beneficial to the proliferation of Firmicutes, and thereby to promote the emission of H2S and NH3. In an opposite case, high abundance of Actinobacteria can decrease the H2S and NH3 emission. As such, the recommended C/N ratio was 18~22 during co-composting of chicken manure and cornstalk. Specifically, the appropriate ratio can also be determined according to the number of cornstalks. [ABSTRACT FROM AUTHOR]

The properties of digestates generated through anaerobic digestion are influenced by interactions between the digester microbial communities, feedstock properties and digester operating conditions. This study investigated the effect of varying initial feedstock carbon to nitrogen (C/N) ratios on digestate microbiota and predicted abundance of genes encoding lignocellulolytic activity. The C/N ratio had a significant impact on the digestate microbiome. Feedstocks with intermediate C/N ratio (20–27) (where higher biomethane potential was observed) showed higher relative abundance of archaea compared to feedstocks with C/N ratios at 17 and 34. Within microbial networks, four microbial clusters and eight connector microorganisms changed significantly with the C/N ratio (P < 0.05). Feedstocks with C/N < 23 were richer in organisms from the family Thermotogaceae and genus Caldicoprobacter and enhanced potential for degradation of maltose, galactomannans, melobiose and lactose. This study provides new insights into how anaerobic digestion conditions relate to the structure and functional potential of digester microbial communities, which may be relevant to both digester performance and subsequent utilization of digestates for composting or amending soil. [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate composting of poultry manure with or without plant residues as bulking agents. Four piles were carried out with different mixtures: poultry manure alone (p1), 66% poultry manure + 16.5% wheat straw + 16.5% conocarpus leaves (p2), 50% poultry manure + 25% wheat straw + 25% conocarpus leaves (p3) and 33% poultry manure + 33% wheat straw + 33% conocarpus leaves (p4). Composting process was monitored over 14 weeks for physicochemical characteristics: temperature, pH, salinity (EC), total organic carbon, total nitrogen and C/N ratio. Furthermore, field observations of color, odor and loss in weight were obtained at the end of composting. All of the studied parameters were influenced by poultry manure rather than bulking agents, however having same trends. All piles reached a thermophilic stage at 3 weeks of composting. Except pH value, the studied parameters followed the typical pattern during composting process. pH values significantly increased with increasing composting period. Salinity values were lower at the end of composting as compared with initial values, but the values still high than optimum range. At the end of composting process, the total organic carbon decreased, while the total nitrogen increased in contrast with initial values. Also, the initial C/N values were 14.43, 24.77, 26.56 and 31.06 then reached values of 9.38, 12.98, 17.97 and 20.81 at the end of composting process, for p1, p2, p3 and p4, respectively. In conclusion, increasing poultry manure content in the pile is important to improve the biodegradation and produce compost with high quality. [ABSTRACT FROM AUTHOR]

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Purpose Soil salinization is one of the most severe abiotic stresses which threaten sustainable agriculture in arid and semi-arid regions including Morocco. The application of organic amendments like composts to saline soils has been confirmed to alleviate soil salinity stress. The present work aims to study the effect of humic acids (HA), as one of the products resulting from organic matter decomposition, on soil salinity reduction. Methods In this perspective, four composts made from mixtures corresponding to initial C/N ratios of 25, 30, 35 and 40 were tested. The four composts were made from mixtures of different proportions of greenhouse wastes, olive mill waste and sheep manure in Souss-Massa region. Representative samples underwent physicochemical analysis, extraction, purification and analysis of HA. The maturity of compost was assessed through some maturation index, prior to the main trial of the interaction between extracted HA and sodium carbonates salt (Na2CO3), largely encountered in saline soils. Results The results showed that the compost with initial C/N ratio of 35 is the most recommended for application as an amendment to alleviate soil salinity. Conclusion The salt stress alleviating effect of compost may be advocated to compost humic acids and their ability to chelate sodium on their carboxylic sites [ABSTRACT FROM AUTHOR]