Maturation of green waste compost as affected by inoculation with the white-rot fungi Trametes versicolor and Phanerochaete chrysosporium

Microbial agents obtained from tomato straw composting effectively promote tomato straw compost maturation and improve compost quality

Appropriate management of agricultural organic waste (AOW) presents a significant obstacle in the endeavor to attain sustainable agricultural development. The proper management of AOW is a necessity for sustainable agricultural development. This can be done skillfully by incorporating microbial agents in the composting procedure. In this study, we isolated relevant bacteria strains from tomato straw AOW, which demonstrated efficient degradation of lignocellulose without any antagonistic effects in them. These strains were then combined to create a composite microbial agent called Zyco Shield (ZS). The performance of ZS was compared with a commercially effective microorganism (EM) and a control CK. The results indicate that the ZS treatment significantly prolonged the elevated temperature phase of the tomato straw pile, showing considerable degradation of lignocellulosic material. This substantial degradation did not happen in the EM and CK treatments. Moreover, there was a temperature rise of 4-6 ℃ in 2 days of thermophilic phase, which was not the case in the EM and CK treatments. Furthermore, the inoculation of ZS substantially enhanced the degradation of organic waste derived from tomato straw. This method increased the nutrient content of the resulting compost and elevated the enzymatic activity of lignocellulose-degrading enzymes, while reducing the urease enzyme activity within the pile. The concentrations of NH4+-N and NO3--N showed increases of (2.13% and 47.51%), (14.81% and 32.17%) respectively, which is again very different from the results of the EM and CK treatments. To some extent, the alterations observed in the microbial community and the abundance of functional microorganisms provide indirect evidence supporting the fact that the addition of ZS microbial agent facilitates the composting process of tomato straw. Moreover, we confirmed the degradation process of tomato straw through X-ray diffraction, Fourier infrared spectroscopy, and by scanning electron microscopy to analyze the role of ZS microbial inoculum composting. Consequently, reinoculation compost strains improves agricultural waste composting efficiency and enhances product quality.

Brown sugar as a carbon source can make agricultural organic waste compost enter the secondary thermophilic stage and promote compost decomposition

To enhance the efficiency of composting agricultural organic waste (AOW), this study aimed to examine the impact of inoculating tomato straw compost with two distinct microbial agents: ZymoZone (ZZ), a composite microbial agent derived from the straw compost and Effective Microorganisms (EM), a commercial microbial agent. Furthermore, in order to reactivate the microorganisms within the compost during the initial high temperature phase, 10% brown sugar was introduced as a carbon source. The objective of this addition was to assess its influence on the composting process. The findings revealed that compared to the control (CK) group, the ZZ and EM treatments extended the first high-temperature phase by 2 and 1 day, respectively. Furthermore, with the addition of 10% brown sugar, the ZZ and EM treatments remained in the second high-temperature phase for 8 and 7 days, respectively, while the CK treatment had already entered the cooling stage by then. Notably, the inoculation of microbial agents and the addition of brown sugar substantially augmented the activity of lignocellulose-related hydrolases, thereby promoting the degradation of lignocellulose in the ZZ and EM treatment groups. This was confirmed by FTIR analysis, which demonstrated that the addition of microbial agents facilitated the degradation of specific substances, leading to reduced absorbance in the corresponding spectra. XRD analysis further indicated a notable reduction in cellulose crystallinity for both the ZZ (8.00%) and EM (7.73%) treatments. Hence, the incorporation of microbial agents and brown sugar in tomato straw compost effectively enhances the composting process and improves the quality of compost products.

Mechanism of sulfur-oxidizing inoculants and nitrate on regulating sulfur functional genes and bacterial community at the thermophilic compost stage

The emission of H₂S odors predominantly occurred at the thermophilic phase of composting, which could cause odorous gas pollution and reduce the fertilizer value of composting products. And sulfur-oxidizing bacteria (SOB) possess oxidative capacities for inorganic sulfur compounds with nitrate applied as electron acceptors. Therefore, this study aimed to assess the effectiveness of combined additives (SOB inoculants and nitrate) on the bacterial community diversity, sulfur-oxidizing gene abundances, and metabolic function prediction at the thermophilic stage of sewage sludge composting. The highest sulfate contents were increased by 1.02-1.34 folds, and the abundances of the sulfur-oxidizing genes (sqr, pdo, sox, and sor) were also enhanced by adding the combined additives. Network patterns revealed a strengthened interaction of inoculants and sulfur functional genes. Microbial functional pathways predicted higher metabolic levels of carbohydrate and amino acid metabolisms with the addition of combined additives, and the predicted relative abundances of sulfur metabolism and nitrogen metabolism were increased by 19.3 ± 2.5% and 24.7 ± 4.1%, respectively. Heatmap analysis showed that the SOB might have a competitive advantage over the indigenous denitrifying bacteria in using nitrate for biochemical reactions. Correlation analyses suggested that sulfur-oxidizing efficacy could be indirectly affected by the environmental parameters through changing the structure of bacterial community. These findings provide new insights toward an optimized inoculation strategy of using SOB and nitrate to enhance sulfur preservation and modulate the bacterial communities at the thermophilic phase of sewage sludge composting.

Thermophilic-mesophilic biodegradation: An optimized dual-stage biodegradation technique for expeditious stabilization of sewage sludge

The present study investigated the stabilization of fresh sewage sludge through a dual-stage biodegradation process; rotary drum composting in series with vermicomposting. After thermophilic exposure in a rotary drum composter, the partially degraded feedstock was separated into S1 without vermiculture, S2 and S3 with Eudrilus eugeniae and Eisenia fetida vermi-monocultures, respectively. The S3-derived vermicompost exhibited an 80% and 88% reduction in CO₂ and ammonium-nitrogen evolution rates, respectively, demonstrating the expedient stabilization of sludge. The robust, more than 85% seed germination index supported S2 and S3 derived vermicompost viability. A significant decrease in heavy metals was evinced with S2 and S3-derived vermicompost; the S1-derived end product exhibited higher Zn, Cr, and Pb levels in the absence of vermicomposting. Furthermore, soil amended with 20% vermicompost from S3 displayed 50% more plant growth than S1. Thus, the optimized thermophilic-mesophilic dual-biodegradation technique stabilizes sewage sludge quickly, has a lot of potential in sludge management facilities around the world, and produces a marketable end product.

Promoting lignocellulose degradation during green waste composting by maintaining a specific temperature through heap size control

Owing to its high lignocellulose content, the recalcitrance of green waste is a technical challenge obstructing the composting process. This study aimed to identify a temperature that could facilitate efficient lignin and cellulose degradation during green waste composting, and maintain this temperature by controlling the heap size to enhance the degradation. The optimum temperature was determined by conducting a laboratory-scale cultivation experiment under controlled temperatures, and a pilot-scale experiment was conducted to explore heap size control and its influence on green waste composting. The results showed that efficient lignin and cellulose degradation was achieved when the temperature was between 45 and 60 ℃, and maintaining this temperature for at least 150 days maximized the lignin and cellulose degradation rates. This was achieved by constraining the heap size at 0.8 m³ at the beginning of composting; 1.56, 2.60, and 4.00 m³ on days 15, 39, and 96; and then enlarging the heap as much as possible on day 156. Following this approach, the duration of the target temperature was extended by over six times, the lignin and cellulose degradation rates were increased by 18.82-21.38 % and 9.54-11.55 %, and nitrification and humification were enhanced. Correlation analysis showed that lignocellulose degradation, nitrification, and humification were positively and significantly correlated with the duration of the target temperature. Generally, heap size control is an ecological and economic method of enhancing the efficiency and quality of green waste composting and compost, respectively.

Evaluation of Co-Composting as an Alternative for the Use of Agricultural Waste of Spring Onions, Chicken Manure and Bio-Waste Produced in Moorland Ecosystems

Composting is an adequate method for treating and valorizing agricultural waste such as those from spring onion (SO) cultivation and chicken breeding (chicken manure–CM). However, the low content of Total Organic Carbon in the waste from SO and the high concentration of total nitrogen in CM are limitations for the composting process. This research studied the co-composting of SO and CM in a moorland ecosystem, together with locally available co-substrates such as biowaste (BW) and woodchips (WC), focusing on the effect of co-composting in process development and end-product quality. A pilot-scale experiment was carried out using three treatments in triplicated composting piles: (i) Treatment A: 43% CM + 41% BW + 16% WC; (ii) Treatment B: 52% CM + 32% SO + 16% WC, and (iii) Treatment C: 70% SO + 30% WC. Treatments A and B reached thermophilic temperatures after two days of the process start and remained at that level for 17 days. However, treatment B reached environmental temperature during curing in a shorter time (43 days) than treatment A (53 days). Treatment C did not achieve thermophilic temperatures. Tests carried out at the end of the process showed end-product stability and non-phytotoxic characteristics (germination indexes 80%). The fertility index of the products showed that treatments A and B presented values of 4.3 (over 5.0) while treatment C obtained a value of 2.5. From the perspective of agricultural use, products from the three treatments had limitations due to deficiencies in essential nutrients like phosphorus. Still, they had potential as a soil amendment for restoration processes. In summary, we have demonstrated that this waste, in combination with other organic materials, could be a good amendment for the composting process and the end product.

The microbial mechanisms of enhanced humification by inoculation with Phanerochaete chrysosporium and Trichoderma longibrachiatum during biogas residues composting

This study investigated effects of composite microbes (CMs) (Phanerochaete chrysosporium and Trichoderma longibrachiatum) on humification during co-composting of biogas residue, spent mushroom substrate and rice straw. Results showed that CMs inoculation elevated degradation ratios of cellulose, hemicellulose and lignin by 7.86%, 8.87% and 6.45%, and contents of humus and humic acid were correspondingly promoted by 15.5% and 23.6%, respectively. Relative abundances of bacteria associated with refractory macromolecules degradation (Flavobacterium, Anseongella and Actinomadura) and cellulolytic fungi (Hypocreales_Incertae_sedis, Hypocreaceae and Psathyrellaceae) were raised by CMs addition. Redundancy analysis demonstrated a positive correlation between microbial communities and temperature, fulvic acid and lignocellulose contents. Moreover, CMs inoculation promoted pathways of xenobiotics biodegradation and metabolism, and biosynthesis of other secondary metabolites, which was closely associated with lignocellulose degradation and humus formation. These results suggested that biological inoculation could enhance composting efficiency and improve compost quality, benefiting biogas residues composting.

Influence of microbial inoculants on co-composting of lignocellulosic crop residues with farm animal manure: A review

The rapidly developing agro-industry generates huge amounts of lignocellulosic crop residues and animal manure worldwide. Although co-composting represents a promising and cost-effective method to treat various agricultural wastes simultaneously, poor composting efficiency prolongs total completion time and deteriorates the quality of the final product. However, supplementation of the feedstock with beneficial microorganisms can mitigate these negative effects by facilitating the decomposition of recalcitrant materials, enhancing microbial enzyme activity, and promoting maturation and humus formation during the composting process. Nevertheless, the influence of microbial inoculation may vary greatly depending on certain factors, such as start-up parameters, structure of the feedstock, time of inoculation, and composition of the microbial cultures used. The purpose of this contribution is to review recent developments in co-composting procedures involving different lignocellulosic crop residues and farm animal manure combined with microbial inoculation strategies. To evaluate the effectiveness of microbial additives, the results reported in a large number of peer-reviewed articles were compared in terms of composting process parameters (i.e., temperature, microbial activity, total organic carbon and nitrogen contents, decomposition rate of lignocellulose fractions, etc.) and compost characteristics (humification, C/N ratio, macronutrient content, and germination index). Most studies confirmed that the use of microbial amendments in the co-composting process is an efficient way to facilitate biodegradation and improve the sustainable management of agricultural wastes. Overall, this review paper provides insights into various inoculation techniques, identifies the limitations and current challenges of co-composting, especially with microbial inoculation, and recommends areas for further research in this field.

Improving the efficiency of vermicomposting of polluted organic food wastes by adding biochar and mangrove fungi

Vermicomposting of food waste amended with biochar and cow dung was studied during a 90-day composting period. The improvement of the vermicomposting process by adding three mangrove fungal species as additional amendments were studied. The use of mangrove fungi Acrophialophora jodhpurensis as a bio-catalytic actor during vermicomposting proved to be beneficial in terms of final compost quality (available N, P and K) and the shortening of the composting period. All three fungal species, however, reached the neutral pH at the end of the composting period and appeared to be beneficial. Heavy metal (Cd, Ni, Pb, Zn, Cu and Cr) concentrations decreased throughout the composting process. Food waste can be treated using vermicomposting with biochar, cow dung and the mangrove fungi A. jodhpurensis. The final vermicomposting product is suitable for agricultural use.

A Glimpse of the World of Volatile Fatty Acids Production and Application: A review

Sustainable provision of chemicals and materials is undoubtedly a defining factor in guaranteeing economic, environmental, and social stability of future societies. Among the most sought-after chemical building blocks are volatile fatty acids (VFAs). VFAs such as acetic, propionic, and butyric acids have numerous industrial applications supporting from food and pharmaceuticals industries to wastewater treatment. The fact that VFAs can be produced synthetically from petrochemical derivatives and also through biological routes, for example, anaerobic digestion of organic mixed waste highlights their provision flexibility and sustainability. In this regard, this review presents a detailed overview of the applications associated with petrochemically and biologically generated VFAs, individually or in mixture, in industrial and laboratory scale, conventional and novel applications.

Fungal pretreatment facilitates the rapid and valuable composting of waste cardboard

This study investigates the waste cardboard (WCB) fungal pretreatment (Oligoporus placenta and Tremetes hirsuta) under monoculture and mixed culture and then composting for 35 d after mixing with cow dung in different ratios. Fungal pretreatment caused significant reduction in cellulose (28.3-35.8%), hemicellulose (61.4-68.4%), lignin (67.5-69.3%) content in WCB. Pretreated WCB showed better rates of decrement in total organic carbon (26.02-47.92%), carbon-to-nitrogen ratio (19.4-23.5), and lignocellulose contents, as well as incensement in total nitrogen (40.48-63.31%), total potassium (51.92-73.91%), germination index (88.5-102.0%), and elemental (Cu, Fe, Zn, Cr, and Mn) levels. Dehydrogenases (142-210 µg g^-1h^-1), and β-galactosidase (210-256 µg g^-1h^-1) activities indicates high microbial-mediated mineralization in setups. Results suggested that WCB could be used as a valuable substrate for valuable-added compost preparation after pretreating with a consortium of white-rot fungi.

Green waste compost as a substitute for turfy soil in external-soil spray seeding substrate

The scarcity of turfy soil (TS), which is the most commonly used external-soil spray seeding (ESSS) substrate component, has recently increased. The aim of this study was to introduce a substitute for TS as an organic matter additive in substrate. Green waste compost (GWC) that was combined with sandy loam soil, polyacrylamide (PAM), and super absorbent polymer (SAP) was used for preparing the soil substrate. Further, a modified soil-spraying experiment and artificial rainfall experiments with an orthogonal design (L₁₆4³) were conducted. These experiments assessed the feasibility of GWC as a component of ESSS substrate and the optimal formulation. The results indicated that the degree of influence of the three factors controlling the amended substrate is GWC > PAM > SAP. GWC improved the physical and chemical properties of the substrate, as well as the seed germination rate and seedling growth. Significant improvements can be observed with respect to the soil bulk density, soil porosity, steady infiltration rate, and anti-shearing strength (p < .01). Additionally, the runoff and soil loss decreased under heavy rainfall. Except for the soil nutrients and seedling height, all other indicators of the GWC substrates were better than those of the commercially available TS substrates. Principal component analysis and range analysis revealed that the optimum values of various design parameters were 40% for the compost volume content, 200 g m^-3 for PAM and 100 g m^-3 for SAP. Based on these results, GWC can be considered to be an effective alternative to TS for ESSS.

Biogenic stabilization and heavy metal immobilization during vermicomposting of vegetable waste with biochar amendment

Vermicomposting is a traditional technology that produces the best quality of compost, but factors such as maturity, presence of heavy metals, etc. need to be tackled prior to agrarian application. The present study investigates the influence of varying biochar dose (2.5, 5, and 10% on a weight basis) on the maturity of compost and heavy metals during vermicomposting of vegetable waste using epigeic earthworm. Biochar amendment notably enhanced the electrical conductivity (up to 2.7 mS/cm), nitrogen content (up to 3.1%), NO₃-N (up to 630 mg/kg) and nutritional value. The heavy metals, oxygen uptake rate (below 0.96 mg/g VS/day) and CO₂ evolution rate (below 1 mg/g VS/day) were attenuated along with degradation of complex organic crystals as observed in powder X-Ray Diffraction (PXRD) spectra. Furthermore, biochar aid in reducing pathogens (below 1.1 × 10³ MPN/g dry weight) as inferred from the Most Probable Number (MPN) results as well as degrading the complex organics into simpler compounds as revealed from the Fourier-transform infrared spectroscopy (FTIR) spectra. The present study inferred that the vegetable waste was biologically stabilized through biochar amendment during vermicomposting process with improved nutritional and physico-chemical properties.

Maintaining the ratio of hydrosoluble carbon and hydrosoluble nitrogen within the optimal range to accelerate green waste composting

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.

Influence of saprophytic fungi and inorganic additives on enzyme activities and chemical properties of the biodegradation process of wheat straw for the production of organo-mineral amendments

Cellulose and lignin as main components of crop residues have a significant influence on composting operations and composition of the final products. Both are strongly associated, and lignin can be considered an important barrier during the biodegradation process of lignocellulosic materials. Saprophytic fungi are efficient lignin degraders due to their complex enzymatic system. Therefore, the influence of the inoculation of saprophytic fungi (Coriolopsis rigida, Pleurotus ostreatus, Trichoderma harzianum and Trametes versicolor) and the supply of inorganic additives (Al₂O₃, Fe₂O₃ and allophanic soil) that promote the stabilization of carbon (C), were analyzed in the biodegradation of wheat straw (WS). The activity of Laccase (LAC), manganese peroxidase (MnP) and β-glucosidase and changes in temperature, pH and E₄/E₆ ratio were analyzed in a biodegradation process of 126 days. The activity of LAC, MnP and the E₄/E₆ ratio were significantly influenced and increased (enzymes) by fungi species, inorganic additives, and time of inorganic material addition, as well as their interactions (p < 0.05). The WS inoculated with T. versicolor showed the highest average activities for LAC, MnP and β-glucosidase (2000, 220 UL^-1 and 400 μmol pNP g^-1 h^-1 respectively). Furthermore, the addition of Al₂O₃ and Fe₂O₃ increased all the activities regarded to the decomposition of WS and influenced the changes associated with the stabilization of OM in composted WS. In conclusion, the inoculation of WS with T. versicolor in combination with metal oxides improved the enzyme related to the biodegradation process of WS favorizing its stabilization in the medium time, which is of importance in the composting of residues with high C/N ratio.

Application of seasonal freeze-thaw to pretreat raw material for accelerating green waste composting

The recalcitrance of green waste, caused by its high lignocellulose content, is a technical challenge for accelerating green waste composting. However, because lignocellulose degradation in litter (similar to green waste) can be promoted during the freeze-thaw season, and the composting is difficult to implement in this period (due to the low temperature); seasonal freeze-thaw was intended to be used as a pretreatment strategy for the existing technical challenge in the winter of cold regions. In this process, green waste was pretreated with seasonal freeze-thaw to enhance its lignocellulose degradation for subsequent composting. To verify this assumption, two strategies for the pretreatment were used: the green waste was either drenched or immersed in water during the freeze-thaw season, and the effects on subsequent composting were evaluated. The results demonstrated that both strategies can significantly promote the mineralization of TOC (total organic carbon, by 2.73%-8.01% compared with the control, the following comparisons were all based on the control), TN (total nitrogen, by 0.21%-0.52%), and lignocellulose (lignin degradation was promoted by 3.52%-3.73%, cellulose degradation was promoted by 13.23%-14.26%) during composting and that the synthesis of humus was also enhanced (by 19.19%-21.43%). Furthermore, since the loss of NH₄⁺N and NO₃^-N was significantly less in the drenched treatment than in the immersed treatment (by 9.15% for the loss of NH₄⁺N and 7.66% for the loss of NO₃^-N), drenching the green waste during the freeze-thaw season might be a better strategy than immersing for nitrogen conservation. An additional advantage of drenching compared to immersing is water conservation.

Alkyl polyglycoside and earthworm (Eisenia fetida) enhance biodegradation of green waste and its use for growing vegetables

Managing municipal green waste is a challenge to municipalities, partly because of the slow rate of decomposition of green waste during composting due to its high lignin and cellulose contents. Hence, this study evaluated the effect of alkyl polyglycoside (APG), a biosurfactant, and the earthworm Eisenia fetida on the composting process. Addition of APG and E. fetida significantly increased total bacteria, cellulolytic fungi, phosphate solubilizing bacteria and nitrogen fixing bacteria populations, and the activities of cellulase, urease and alkaline phosphatase in composts as compared with the control. The APG and earthworm treatments also increased surface roughness and porosity of the green waste; Compared with control, APG and earthworm addition increased the degradation rate of TOC, lignin and cellulose by 5.9-17.9, 10.3-32.0 and 10.8-18.8%, respectively, and resulted in better compost quality, as was reflected in the neutral pH, higher cation exchange capacity (CEC) and nutrient concentrations (N, P, K, Ca, Mg, Fe, Cu, Zn, Mn). Final germination percentage and growth rate of tomato, eggplant and pepper seedlings were higher (P < 0.05) or similar in all composts produced with the addition of APG and earthworm, while plant growth was lower (P < 0.05) in the compost produced with the control than in peat substrate. The combination of APG+E. fetida enhanced the decomposition of green waste and improved final compost quality the most. Further research is needed to determine the best level of APG addition and optimum earthworm density for composting green waste.

Comparison of chemical and microbiological changes during the aerobic composting and vermicomposting of green waste

This research was conducted to compare chemical and microbiological properties during aerobic composting (AC) and vermicomposting (VC) of green waste. Relative to AC, VC significantly decreased the pH and lignin and cellulose contents, and significantly increased the electrical conductivity and total N and available P contents. For AC, BIrii41_norank (order Myxococcales) was the major bacterial genus at 30 d and again became dominant genus from 90–150 d, with relative abundances of 2.88% and 4.77–5.19%, respectively; at 45 d and 60 d, the dominant bacterial genus was Nitrosomonadaceae_uncultured (order Nitrosomonadales) with relative abundances of 2.83–7.17%. For VC, the dominant bacterial genus was BIrii41_norank (except at 45 d), which accounted for 2.11–7.96% of the total reads. The dominant fungal class was Sordariomycetes in AC (relative abundances 39.2–80.6%) and VC (relative abundances 42.1–69.5%). The abundances of microbial taxa and therefore the bacterial and fungal community structures differed between VC and AC. The quality of the green waste compost product was higher with VC than with AC. These results will also help to achieve further composting technology breakthroughs in reducing the composting time and improving compost quality.

Application of quadratic regression orthogonal design to develop a composite inoculum for promoting lignocellulose degradation during green waste composting

The aims of this study are to determine the feasibility of applying QROD (quadratic regression orthogonal design) to optimize a combination of microorganisms and to develop a composite inoculum for promoting lignocellulose degradation during GWC (green waste composting). This feasibility was studied in a laboratory scale experiment, using three lignocellulolytic microorganisms, isolated from the mature phase of GWC by the dilution plating method. After the feasibility was confirmed, a composite inoculum was developed through the results of the optimization, whose effect was evaluated by comparing it with Phanerochaete chrysosporium and EM (Effective Microorganisms) in a pilot scale experiment of GWC. The use of QROD to finish this optimization was proven feasible, because the p value of the regression equation was less than 0.05 (0.0108), meaning that the quadratic regression model is suitable for describing the relationship between the combination of the three microorganisms and their ability to degrade lignocellulose. Additional proof of this feasibility is that the composite inoculum in the quadratic regression orthogonal experiment demonstrated lignocellulose degradation ability similar to the GWC experiment. Although the lignin degradation ability of the composite inoculum did not surpass Phanerochaete chrysosporium, it was stronger than EM. Meanwhile, cellulose degradation ability and humus synthesis ability of the composite inoculum were stronger than for Phanerochaete chrysosporium and were close to EM. It is hard to tell which inoculum is the best since each inoculum had advantages in different aspects, while the composite inoculum still showed a considerable effect of lignocellulose degradation during GWC.

Bamboo biochar amendment improves the growth and reproduction of Eisenia fetida and the quality of green waste vermicompost

Vermicomposting is a promising method for reusing urban green waste. However, high lignin content in the green waste could hinder the development of earthworm and microorganisms and the vermicomposting process, resulting in a low-quality vermicompost product. The objective of this study was to evaluate the effect of bamboo biochar addition (at 0%, 3%, and 6% on a dry w/w basis) on the activity of Eisenia fetida and the obtained vermicompost. Biochar addition increased (P < 0.05) earthworm biomass, juvenile and cocoon numbers of Eisenia fetida, as well as the activities of dehydrogenase, cellulase, urease and alkaline phosphatase. Compared to the control, lignin degradation rate was enhanced up to 13.89% by biochar addition. Biochar addition also improved the vermicompost quality in terms of cation exchange capacity (CEC), dissolved organic carbon (DOC) degradation, humification, nitrogen transformation, toxicity to germinating seeds (Brassica rapa L., Chinensis group) and heavy metals concentrations. The 6% bamboo biochar addition rate achieved maturity after 60 days of vermicomposting and resulted in the highest quality vermicompost based on parameters such as CEC, DOC, NH₄⁺-N/NO₃^--N ratio, germination index and heavy metal concentration. We conclude that 6% biochar addition promoted earthworm growth and the vermicomposting of green waste.

Mushrooms: from nutrition to mycoremediation

Mushrooms are well known as important food items. The uses of mushrooms in the cuisine are manifolds and are being utilized for thousands of years in both Oriental and Occidental cultures. Medicinal properties of mushrooms show an immense potential as drugs for the treatment of various diseases as they are rich in a great variety of phytochemicals. In this review, we attempted to encompass the recent knowledge and scientific advancement about mushrooms and their utilization as food or curative properties, along with their natural ability to accumulate (heavy) metals/radionuclides, which leads to an important aspect of bioremediation. However, accumulation of heavy metals and radionuclides from natural or anthropogenic sources also involves potential nutritional hazards upon consumption. These hazards have been pointed out in this review incorporating a selection of the most recently published literature.

Effects of Rhamnolipid and Microbial Inoculants on the Vermicomposting of Green Waste with Eisenia fetida

The effects of adding the biosurfactant rhamnolipid, the lignolytic and cellulolytic fungus Phanerochete chrysosporium, and the free-living nitrogen-fixing bacterium Azotobacter chrococcum on vermicomposting of green waste with Eisenia fetida was investigated. The addition of rhamnolipid and/or either microorganism alone or in all combinations significantly increased E. fetida growth rate, the number of E. fetida juveniles and cocoons, the population densities of cellulolytic fungi and Azotobacter bacteria, and cellulase and urease activities in the vermicomposts. The quality of the final vermicompost (in terms of electrical conductivity, nutrient content, C/N ratio, humic acid content, lignin and cellulose contents, and phytotoxicity to germinating seeds) was enhanced by addition of rhamnolipid and/or microorganisms. The physical characteristics of vermicomposts produced with rhamnolipid and/or microorganisms were acceptable for agricultural application. The best quality vermicompost was obtained with the combined addition of P. chrysosporium, A. chrococcum, and rhamnolipid.