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The demand of poultry products like egg, meat and value added products are increasing and to meet the demand their production has seen increasing trend. The biowaste generated from the sector is a concern because highly nutrient rich manure has a great impact on the environmental pollution. Properly managed poultry manure acts as a very good source of nutrients for plants. Composting is one of the methods used and among these, forced aeration helps to improve the manurial value of compost. Carbon, nitrogen, pH and the C:N ratio are the important parameters of concern before applying manure into agricultural land. The present study on poultry manure co-composted with left over fodder has a great impact in reducing the pH and C/N ratio into ideal range. [ABSTRACT FROM AUTHOR]

The attachment strength of bacteria to surfaces can affect the efficacy of sanitizers during washing. This study aimed to determine the effectiveness of chlorination and aeration in the removal of pathogens from the surface of produce. Cucumbers and bell peppers were inoculated with Listeria innocua, Escherichia coli O157:H7, or Salmonella enterica; afterwards, the produce was washed with or without chlorinated water (100 ppm) for 3 min in combination with or without aeration. Cucumbers washed with chlorinated water, with or without aeration, presented significant reductions of L. innocua (3.65 log CFU/cm2 and 1.13 log CFU/cm2, respectively) (p < 0.05). Similarly, bell peppers washed in chlorinated water with aeration (1.91 log CFU/g) and without aeration (2.49 log CFU/g) presented significant reductions of L. innocua. A significant reduction of L. innocua was observed on bell peppers washed with non-chlorinated water with aeration (2.49 log CFU/g) (p < 0.05). Non-chlorinated water was also effective in significantly reducing the level of Salmonella enterica (p < 0.05) on cucumbers and bell peppers. Washing with chlorinated water with aeration reduced Salmonella enterica levels from 4.45 log CFU/cm2 on cucumbers to below the detectable limit (0.16 log CFU/cm2). The highest reduction of Salmonella enterica from bell peppers occurred after washing with chlorinated water with aeration (2.48 log CFU/g). E. coli O157:H7, L. innocua, and Salmonella enterica levels present in non-chlorinated water after washing contaminated produce with or without aeration were significantly greater than those in chlorinated water (p < 0.05). After treatment, the population levels of all pathogens in chlorinated water with or without aeration were below the detectable limit for bell peppers (<1.10 log CFU/mL) and cucumbers (<1.20 log CFU/mL). Using chlorine in combination with forced aeration during washing minimizes cross-contamination of bacterial pathogens. [ABSTRACT FROM AUTHOR]

Three trapezoidal piles of the mixtures consisting of rose oil processing solid wastes, separated dairy and poultry manure, and straw as bulking agents were composted to determine the effects of aeration pattern employing forced aeration on various physical and chemical properties and energy consumption by aeration. Temperature feedback control of aeration fans was performed with Rutgers strategies in the positive mode. Aeration patterns with on/off cycles (minute/minute) of 5/30, 7.5/30, and 12.5/30 were performed for Pile-1, Pile-2, and Pile 3, respectively. The control group was set to 5/30 (on/off time) and the experimental groups were set to 7.5/30 and 12.5/30 (on/off time). The results showed that although composting performance parameters of temperature and O2 as a function of time showed some differences, the similar end-product quality in terms of pH, EC contents and total phosphorus was achieved. The highest energy consumed by fans per Organic Matter Loss (OML, %) of composting (1.044 kWh/OML) was obtained when the fan on/off cycles of 5/30 was applied. When the fan on-time increased to 12.5 min, the energy consumed by the fan was reduced by 12.55% (0.913 kWh/OML). It was concluded that operating the composting process at the higher fan on-time (Pile-3) within acceptable limits appears to be economically convenient in conjunction with energy consumption by aeration fans. [ABSTRACT FROM AUTHOR]

On-farm composting of agro-livestock wastes can be considered the most appropriate method for their recycling. Pile turning (PW) is one of the most widely used aeration systems for composting. However, this system has long composting periods and is inefficient at supplying oxygen and controlling the temperature. To minimize these drawbacks, the combination of turnings with forced aeration (PR) is an option; in this work, this combination was compared to PW as an aeration system for the co-composting of vegetable waste with different manures. In this comparative study, the evolution of the process, the compost quality and the economic and environmental impacts of the process were evaluated. The PR system was more appropriate for obtaining sanitized composts (the temperature was ≥55 °C for at least three consecutive days) with an adequate degree of maturity. Furthermore, this system reduced the organic matter and nutrient losses, yielding composts with higher agronomic value and a higher total combined value of the nutrients than those obtained using the PW system. However, the energy consumption and associated CO2 emissions were lower for the PW system, since this aeration system was based only on turnings without the use of forced aeration, as in the case of the PR system. Agricultural valorization of composts will offset this energy consumption and its impact, since it will contribute to reducing the use of synthetic fertilizers. However, more studies are required on the PR composting system and other agro-livestock wastes for the creation of centralized on-farm composting sites, where all steps of the composting chain are optimized. [ABSTRACT FROM AUTHOR]

Packed-bed bioreactors are often used for aerobic solid-state fermentation, since the forced aeration supplies O2 and removes metabolic heat from the bed. Motivated by the potential for applications in biorefineries, we review studies conducted on packed-bed bioreactors over the last decade, evaluating the insights these studies provide into how large-scale packed beds should be designed and operated. Many studies have used low superficial air velocities and suffer from preferential airflow, such that parts of the bed are not properly aerated. Moreover, some studies have proposed ineffective strategies, such as reversing the direction of the airflow or introducing air through perforated pipes within the bed. Additionally, many studies have used narrow water-jacketed packed-bed bioreactors, but these bioreactors do not reflect heat removal in wide large-scale packed beds, in which heat removal through the side walls makes a minor contribution. Finally, we conclude that, although some attention has been given to characterizing the porosities, water sorption isotherms and volumetric heat and mass transfer coefficients of substrate beds, this work needs to be extended to cover a wider range of solid substrates, and work needs to be done to characterize how these bed properties change due to microbial growth. [ABSTRACT FROM AUTHOR]

The attachment strength of bacteria to surfaces can affect the efficacy of sanitizers during washing. This study aimed to determine the effectiveness of chlorination and aeration in the removal of pathogens from the surface of produce. Cucumbers and bell peppers were inoculated with Listeria innocua, Escherichia coli O157:H7, or Salmonella enterica; afterwards, the produce was washed with or without chlorinated water (100 ppm) for 3 min in combination with or without aeration. Cucumbers washed with chlorinated water, with or without aeration, presented significant reductions of L. innocua (3.65 log CFU/cm2 and 1.13 log CFU/cm2, respectively) (p < 0.05). Similarly, bell peppers washed in chlorinated water with aeration (1.91 log CFU/g) and without aeration (2.49 log CFU/g) presented significant reductions of L. innocua. A significant reduction of L. innocua was observed on bell peppers washed with non-chlorinated water with aeration (2.49 log CFU/g) (p < 0.05). Non-chlorinated water was also effective in significantly reducing the level of Salmonella enterica (p < 0.05) on cucumbers and bell peppers. Washing with chlorinated water with aeration reduced Salmonella enterica levels from 4.45 log CFU/cm2 on cucumbers to below the detectable limit (0.16 log CFU/cm2). The highest reduction of Salmonella enterica from bell peppers occurred after washing with chlorinated water with aeration (2.48 log CFU/g). E. coli O157:H7, L. innocua, and Salmonella enterica levels present in non-chlorinated water after washing contaminated produce with or without aeration were significantly greater than those in chlorinated water (p < 0.05). After treatment, the population levels of all pathogens in chlorinated water with or without aeration were below the detectable limit for bell peppers (

Composting has been recognized as an environmentally acceptable method for treating animal carcasses. This field-scale study was designed to investigate the feasibility of dead pigs in a forced aeration composting system with dimension of 3.92 m length × 5.0 m width. Pig carcass composting was conducted during different seasons to determine the effect of different ambient temperatures on pig carcass degradation. Results showed that the forced aeration composting system was effective in disposal of dead pigs. High degradation of mortalities (> 91.4%) occurred in all treatment after 49 d composting periods. All flesh was completely degraded and only fragments of bones can be found. The days when compost pile temperature of trials in autumn, summer, next autumn and winter was above 50 °C were 32, 47, 34 and 31 days, respectively. In our study, cold season had no significant influence on the carcass decomposition rate, and ambient temperature of < 0 °C did not hinder the use of forced aeration system for the disposal of dead pigs. Turning during composting can promote the complete degradation of pig carcasses. [ABSTRACT FROM AUTHOR]

This study is aimed to evaluate the efficiency of biochar and crude glycerin as additives in N retention throughout the composting of cattle slaughterhouse waste in static piles receiving forced aeration. There were five treatments (control, biochar accounting for 5 and 10%, and glycerin accounting for 5 and 10%, both at total solids) and four times (20, 50, 70 and 90 days of composting). The slaughterhouse waste was composted with a bulking agent at a ratio of 3:1, and the mixtures of waste and the tested additives were placed in nylon bags. The piles reached thermophilic temperatures soon after the process started and following turnings. The reductions of volatile solids, carbon, hemicellulose, cellulose and lignin were not influenced by the additives, resulting in averages of 69.1, 67.1, 62.1, 51.6 and 35.3%, respectively. The control showed greater N losses (58.38%), compared to the treatments with additives. The inclusions of biochar yielded an average loss of 48.47% N, while 10% of glycerin resulted in the lowest N losses (44.83%). The use of biochar and glycerin as additives in the composting of slaughterhouse waste is recommended in order to decrease N losses and improve the concentration of nutrients, without compromising the biodegradation of organic components. [ABSTRACT FROM AUTHOR]

BACKGROUND Conidia from Metarhizium are part of the commercial formulations used worldwide for insect pest control. Among the alternatives proposed to improve conidia production, the use of packed column bioreactors allows controlled processes with higher levels of production and productivity than those obtained with the traditional process in plastic bags. However, problems associated with overheating, low CO2 removal, and inadequate oxygen supply in packed columns limit the scale‐up and operation at an industrial scale. RESULTS: Packed densities, up to 1.5 times higher than those obtained in lab‐scale column bioreactors, negatively affected growth and conidia production by Metarhizium robertsii (ENCB‐MG‐81). Therefore, a spherical‐style packing was added to decrease packed density and improve the culture conditions in packed column bioreactors. The addition of spherical‐style packing reduced the axial temperature gradient (up to 50%), increased the maximum CO2 production rate and the total CO2 production (up to 2.5 times), and enhanced the volumetric conidia productivity in packed column bioreactors from 5.28 ± 1.36 to 6.77 ± 0.89 × 108 conidia cm−3. CONCLUSION: The use of spherical‐style packing within the culture bed in column bioreactors improves the production of conidia by Metarhizium robertsii, as well as the gas exchange and heat removal from the bed. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Bacterial community dynamics and copper leaching with applied forced aeration were investigated during low-grade copper sulphide bioleaching to obtain better bioleaching efficiency. Results illustrated that appropriate aeration improved bacterial concentrations and leaching efficiencies. The highest bacterial concentration and Cu2+ concentration after 14-d leaching were 7.61 × 107 cells·mL−1 and 704.9 mg·L−1, respectively, at aeration duration of 4 h·d−1. The attached bacteria played a significant role during bioleaching from 1 to 7 d. However, free bacteria dominated the bioleaching processes from 8 to 14 d. This phenomenon was mainly caused by the formation of passivation layer through Fe3+ hydrolysis along with bioleaching, which inhibited the contact between the attached bacteria and ore. Meanwhile, 16S rDNA analysis verified the effect of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans on the bioleaching process. The results demonstrate the importance of free and attached bacteria in bioleaching. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this work was to evaluate the composting process of agro-industrial waste (coffee husk, plantain peel, bovine manure, and food waste) with rock phosphate supplementation using static piles with forced aeration. Methods: Three 5-tonne piles of waste were composted in each treatment; supplementation treatment contained 15% (dry basis) rock phosphate and the control did not. Carbon/nitrogen ratio, total and soluble phosphorus, oxygen concentration, pH, and temperature were measured throughout composting. Results: Both treatments reached final C/N ratios about 9.0. Total and soluble phosphorus was higher for supplemented piles (6.4% and 154 ppm, respectively) compared to control (3.1% and 106 ppm, respectively). The lowest oxygen concentrations (below 40% oxygen saturation) was observed in the first 15 weeks. Based on their Solubilization Index (SI), 203 isolations of phosphate-solubilizing bacteria were obtained and characterized. For supplemented piles, molecular identification was made to the two isolates with the highest SI in the mesophilic phase and to one isolate in the thermophilic phase. Mesophilic isolates were identified as Pseudomonas aeruginosa and the thermophilic one as Nocardiopsis spp. (99% probability). Conclusion: Rock phosphate addition did not affect the final product quality, since both treatments comply with the parameters of mature compost. Compost supplementation with rock phosphate is a viable strategy not only to supply phosphorus to the soil, but also to increase its content of phosphate-solubilizing bacteria. [ABSTRACT FROM AUTHOR]

This study aimed to assess the efficiencies of composts and vermicomposts obtained from two different composting methods on the growth, mineral nutrition and nutrient uptake of wheat. Composts and vermicomposts were applied to plastic pots under greenhouse condition with the application doses of 0, 5, 10, 20, and 40 t ha−1. The pot-experiment lasted three months. The results showed that plant dry weight increased with the increase in doses when compared to the control groups where no composts and vermicomposts were applied. However, no differences were found among the doses from 5 to 40 t ha−1 of composts and vermicomposts. Although application doses did not affect significantly on the most of the plant nutrient concentrations, Fe concentration in plant decreased with the increase in application doses. Additionally, no significant differences among the composts and vermicomposts on plant nutrient concentrations except for Mg were detected. Comparing to the control dose (0 t ha−1), nutrient uptakes by plant from the soil significantly increased with the increase of application doses, but no significant differences were determined amongst the doses of 5 and 40 t ha−1, generally. The effect of production methods on the most of investigated parameters including plant dry weight was similar. [ABSTRACT FROM AUTHOR]

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Abstract Hazardous and odorous gas emissions from composting and methanization plants are an issue of public concern. Odor and chemical monitoring are thus critical steps in providing suitable strategies for air pollution control at waste treatment units. In this study, 141 gas samples were extensively analyzed to characterize the odor and chemical emissions released upon the aerobic treatment of 10 raw substrates and five digestates. For this purpose, agricultural wastes, biowastes, green wastes, sewage sludge, and municipal solid waste (MSW) were composted in 300 L pilots under forced aeration. Gas exhausts were evaluated through dynamic olfactometry and analytical methods (i.e., GC/MS) to determine their odor concentration (OC in OU E m−3) and chemical composition. A total of 60 chemical compounds belonging to 9 chemical families were identified and quantified. Terpenes, oxygenated compounds, and ammonia exhibited the largest cumulative mass emission. Odor emission rates (OU E h−1) were computed based on OC measurements and related to the initial amount of organic matter composted and the process time to provide odor emission factors (OEFs in OU E g−1OM 0). The composting process of solid wastes accounted for OEFs ranging from 65 to 3089 OU E g−1OM 0 , whereas digestates composting showed a lower odor emission potential with OEF fluctuating from 8.6 to 30.5 OU E g−1OM 0. Moreover, chemical concentrations of single compounds were weighted with their corresponding odor detection thresholds (ODTs) to yield odor activities values (OAVs) and odor contribution (PO i , %). Volatile sulfur compounds were the main odorants (PO i = 54–99%) regardless of the operational composting conditions or substrate treated. Notably, methanethiol was the leading odorant for 73% of the composting experiments. Graphical abstract Image 1 Highlights • Terpenes, oxygenated compounds, and ammonia were actively emitted upon composting. • Odor emission factor (OEFs) were computed for substrates treated. • Digestates composting exhibited lower odor emission potential than raw substrates. • An odor activity value (OAV) strategy was implemented. • Methanethiol and hydrogen sulfide were the major odor contributors along composting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Membrane-covered coupled with aeration effectively reduced GHG emissions. • Membrane-covered coupled with aeration could create a stable aerobic environment. • Membrane-covered coupled with aeration enhanced metabolism function. • O 2 concentration was key to affecting bacterial community function and CH 4 emission. • GHG emissions were regulated by anaerobic bacteria during aerobic composting. Greenhouse gas (GHG) emissions from manure management processes deserve more attention. Using three industrial-scale experiments, this study comprehensively evaluated the effects of different aeration coupled with semi-permeable membrane-covered strategies on the structure and function of bacterial communities and their impact on GHG emissions during dairy manure aerobic composting. The succession of the bacterial communities tended to be consistent for similar aeration strategies. Ruminiclostridium and norank_f__MBA03 were significantly positively correlated with the methane emission rate, and forced aeration coupled with semi-permeable membrane-covered decreased GHG emissions by inhibiting these taxa. Metabolism was the most active function of the bacterial communities, and its relative abundance accounted for 75.69%–80.23%. The combined process also enhanced carbohydrate metabolism and amino acid metabolism. Therefore, forced aeration coupled with semi-permeable membrane-covered represented a novel strategy for reducing global warming potential by regulating the structure and function of the bacterial communities during aerobic composting of dairy manure. [ABSTRACT FROM AUTHOR]

Animal manure is a source of the greenhouse gas nitrous oxide (N 2 O), therefore understanding the mechanisms underlying its production is essential for developing mitigating strategies and sustainable livestock production system. In this study, microbial communities potentially involved in multiple emission peaks during initial stage of laboratory-scale dairy manure composting with forced aeration system were investigated. Mature compost was used for the bulking agent. Change of overall bacterial community and nitrification-denitrification gene abundance were monitored by using 16S rRNA gene amoA , nirS , nirK or nosZ genes, respectively. Three N 2 O emission peaks were observed when the temperature reached at 45, 60 and 72 °C, at the same timing of oxygen consumption peaks. The maximum N 2 O emission peak was 3.86 mg h −1 kg −1 TS when the temperature reached at 60 °C. The shift of bacterial community among these experimental periods was significant, orders Flavobacteriales , Burkholderiales and Xanthomonadales increased, while orders belong to Bacillales , Lactobacillales , Clostridiales and Bacteroidales decreased. In addition, abundance of two denitrification genes ( nirS and nosZ ) significantly increased during this period. Clone library analysis of these genes showed that significantly increased sequences belonged to Pseudomonas -like clusters for both genes, indicates that denitrifiers possesses these genes are involved for these N 2 O emission peaks caused by mature compost addition. [ABSTRACT FROM AUTHOR]

Microbial degradation is an important pathway during the removal of pharmaceuticals in constructed wetlands (CWs). However, the effects of CW design, plant presence, and different plant species on the microbial community in CWs have not been fully explored. This study aims to investigate the microbial community metabolic function of different types of CWs used to treat ibuprofen via community-level physiological profiling (CLPP) analysis. We studied the interactions between three CW designs (unsaturated, saturated and aerated) and six types of mesocosms (one unplanted and five planted, with Juncus , Typha , Berula, Phragmites and Iris ) treating synthetic wastewater. Results show that the microbial activity and metabolic richness found in the interstitial water and biofilm of the unsaturated designs were lower than those of the saturated and aerated designs. Compared to other CW designs, the aerated mesocosms had the highest microbial activity and metabolic richness in the interstitial water, but similar levels of biofilm microbial activity and metabolic richness to the saturated mesocosms. In all three designs, biofilm microbial metabolic richness was significantly higher ( p  < .05) than that of interstitial water. Both the interstitial water and biofilm microbial community metabolic function were influenced by CW design, plant presence and species, but design had a greater influence than plants. Moreover, canonical correlation analysis indicated that biofilm microbial communities in the three designs played a key role in ibuprofen degradation. The important factors identified as influencing ibuprofen removal were microbial AWCD (average well color development), microbial metabolic richness, and the utilization of amino acids and amine/amides. The enzymes associated with co-metabolism of l -arginine, l -phenyloalanine and putrescine may be linked to ibuprofen transformations. These results provide useful information for optimizing the operational parameters of CWs to improve ibuprofen removal. [ABSTRACT FROM AUTHOR]

Agro-industrial waste byproducts are commonly inexpensive organic nutritional sources for production of filamentous fungi, and selection of an optimal bioreactor is a key factor for attaining satisfactory biomass yield and quality. The insect-pathogenic fungus Beauveria bassiana (Hypocreales: Cordycipitaceae) has been extensively mass produced by solid-state fermentation using precooked cereal grains. Here, we propose low-cost palm oil residues as the main substrate using a cylindrical packed-column aerobic bioreactor prototype designed for conidial production of B. bassiana. Fermentation treatments using B. bassiana strain CG1229 assessed the impact of temperature, air flow, substrate moisture content, and ratio between palm fiber (PF) and palm kernel cake (PKC) on conidial yield and desiccation tolerance. Results showed significant enhanced productivity (2 ×1010 conidia g−1 dry matter) and reduced fermentation time (from 168 h to 120 h) by this method compared with the conventional tray bioreactor. Optimal substrate conditions were 60% initial moisture and 30% PF + 70% PKC content, fermentation at 26 °C with aeration rate ≥ 0.2 L min−1. Air drying conidia inside the column yielded > 95% germination. Maximum spore production was achieved in 120 h. Our findings demonstrate the feasibility of using a packed-column bioreactor for mass production of B. bassiana conidia using low-cost agricultural residues, which contributes to a sustainable production method of this biopesticide in Brazil. [Display omitted] ● Packed-column bioreactor allowed production and drying of B. bassiana conidia. ● Spore production was optimized with palm oil residues and moisture content. ● Spore viability was most affected by temperature, moisture and aeration rate. ● Valorization of palm residues into a bioproduct is demonstrated. [ABSTRACT FROM AUTHOR]

The production of γ-decalactones as aroma compounds is highly dependent on the access of the biocatalyst to substrate and co-substrate (oxygen). In this work, the potential of solid state fermentation (SSF) is investigated for this production with Y. lipolytica W29. Luffa sponge was used as an inert support and the investigation focused on the impact of aeration on metabolites. In that goal, experiments were carried out in three different SSF reactor types, wide-mouth Erlenmeyer flask (static aeration), forced aeration mini-reactor, and small-headspace bottle (without aeration). Four lactones were detected by GC–MS during the degradation of ricinoleic acid from castor oil by Y. lipolytica W29: 3-hydroxy-γ-decalactone, which reached the high concentration of 5 g/L (in wide-mouth Erlenmeyer flask), γ-decalactone, dec-2-en-4-olide and dec-3-en-4-olide. In this study, some yeast cells changed their morphological properties from the yeast-like shape to pseudo-mycelium and mycelium. These cells may undergo a metabolic shift resulting in the high production of 3-hydroxy-γ-decalactone. The yield of lactone in the small-headspace bottle was very low suggesting insufficient oxygen availability. For their part, forced-aeration conditions in mini-reactors resulted in the stripping of lactone compounds. From the present work, an alternative process is proposed as a novel model for lactone production. [ABSTRACT FROM AUTHOR]

The aim of this study was to optimise airflow rate for glucoamylase and protease production from waste bread via solid state fermentation by Aspergillus awamori in packed bed bioreactors. Airflow rates, between 0.40 and 3.00 vvm, were tested. In all experiments, the fungal growth was almost uniform throughout the solids. Fungi grew both on and within the substrate and fungal cakes were formed. The highest glucoamylase and protease activities were recorded as 130.8 U/g bread (db) and 80.3 U/g bread (db) in the experiments with 1.50 wm airflow rate, respectively. These values are 27.2% and 32.3% higher than the glucoamylase and protease activities obtained in petri dish experiments with static air. At 1.50 vvm airflow rate, the dry weight of the solids had decreased to 46% of the initial value at the end of the fermentation. The temperature of the solids increased up to 37.5 °C with high axial temperature gradients due to high metabolic activity. The average moisture content of the solids first decreased to 150% (db) and then increased to 275% (db) by the end of the fermentation. Both above and below 1.50 wm airflow rate, enzyme production and fungal growth were affected significantly. Also, a Gaussian-based mathematical model was developed to model the effects of airflow rate on enzyme production. The model fitted almost seamlessly to the experimental data. Thus, this study clearly showed the effects of aeration on glucoamylase and protease production from waste bread under solid state fermentations. [ABSTRACT FROM AUTHOR]

The aim of this study was to uncover ways to mitigate greenhouse gas (GHG) emissions and reduce energy consumption during the composting process. We assessed the effects of different aeration rates (0, 0.18, 0.36, and 0.54 L/(kg dry matter (dm)·min)) and methods (continuous and intermittent) on GHG emissions. Pig feces and corn stalks were mixed at a ratio of 7:1. The composting process lasted for 10 weeks, and the compost was turned approximately every 2 weeks. Results showed that both aeration rate and method significantly affected GHG emissions. Higher aeration rates increased NH3 and N2O losses, but reduced CH4 emissions. The exception is that the CH4 emission of the passive aeration treatment was lower than that of the low aeration rate treatment. Without forced aeration, the CH4 diffusion rates in the center of the piles were very low and part of the CH4 was oxidized in the surface layer. Intermittent aeration reduced NH3 and CH4 losses, but significantly increased N2O production during the maturing periods. Intermittent aeration increased the nitrification/denitrification alternation and thus enhanced the N2O production. Forced aeration treatments had higher GHG emission rates than the passive aeration treatment. Forced aeration accelerated the maturing process, but could not improve the quality of the end product. Compared with continuous aeration, intermittent aeration could increase the O2 supply efficiency and reduced the total GHG emission by 17.8%, and this reduction increased to 47.4% when composting was ended after 36 days. [ABSTRACT FROM AUTHOR]

Highlights: [•] The gaseous emissions produced by various composting process conditions were characterized and quantified. [•] Nine compounds were potentially odorous: TMA, NH3, 2-pentanone, 1-propanol-2-methyl, acetophenone and sulphur forms. [•] The tested composting process conditions reduced odour emissions by a factor of 5–10. [•] A reduction of 105 to 106 is required to reach an odour threshold limit at peak event emissions. [•] Both aeration rate and bulking agent had the most impact on reducing odour emissions. [Copyright &y& Elsevier]

The objective of this paper was to study the influence of process conditions (aeration rate, bulking agent (BA) particle size distribution, BA incorporation ratio and process duration) on the quality (moisture, stability, disinfection as per the temperature regime and nitrogen conservation) of mechanically aerated pig slaughterhouse sludge (PSS) compost. The waste and wood chips as BA were composted in 300 L mechanically aerated reactors. The range of process conditions tested were: aeration rate from 1.68 to 13.04 L/h/kg of wet sludge; BA particle size distribution of <10 mm, 10-20 mm and 20-30 mm, and; BA:PSS incorporation ratio of 0.55-1.11 (kg of wet wood chips/kg of wet sludge). The results showed that a high aeration rate and a high BA:PSS ratio produced a faster stabilization whereas BA of small particles size distribution increased the amount of biodegradable matter and slowed down stabilization. The composting temperature regime was positively correlated to O consumption with a high BA:PSS ratio and a small BA particles size. A low aeration rate, without being O limiting, optimized the composting process since too high or too low an aeration rate favored heat losses through respectively convection and water evaporation. Water loss was positively correlated with temperature regime and a higher BA:PSS ratio as opposed to a small BA particle size distribution. Similarly, medium to high aeration rates favored water removal. The composting process duration was reduced with a high aeration rates of 6.22 or 9.8 L/h/kg of wet sludge and a high BA:PSS ratio of 1.11. Finally, process condition had no influence on compost nitrogen conservation. [ABSTRACT FROM AUTHOR]

Abstract: The aeration rate is a key process control parameter in the forced aeration composting process because it greatly affects different physico-chemical parameters such as temperature and moisture content, and indirectly influences the biological degradation rate. In this study, the effect of a constant airflow rate on vertical temperature distribution and organic waste degradation in the composting mass is analyzed using a previously developed mathematical model of the composting process. The model was applied to analyze the effect of two different ambient conditions, namely, hot and cold ambient condition, and four different airflow rates such as 1.5, 3.0, 4.5, and 6.0m3 m−2 h−1, respectively, on the temperature distribution and organic waste degradation in a given waste mixture. The typical waste mixture had 59% moisture content and 96% volatile solids, however, the proportion could be varied as required. The results suggested that the model could be efficiently used to analyze composting under variable ambient and operating conditions. A lower airflow rate around 1.5–3.0m3 m−2 h−1 was found to be suitable for cold ambient condition while a higher airflow rate around 4.5–6.0m3 m−2 h−1 was preferable for hot ambient condition. The engineered way of application of this model is flexible which allows the changes in any input parameters within the realistic range. It can be widely used for conceptual process design, studies on the effect of ambient conditions, optimization studies in existing composting plants, and process control. [Copyright &y& Elsevier]

Four composting systems for aerobic treatment of olive residues were evaluated during 140 days: T1 with windrows 100% olive residues and manual turning, T2 with windrows 100% olive residues and forced aeration, T3 with windrows 75% olive residues and 25% chips pruning and manual turning, and T4 with windrows 75% olive residues and 25% pruning chips with forced aeration combined with manual turning. Treatments with bulking agent (T3 and T4) reached thermophilic phase at the seventh day, whereas T1 and T2 at the twenty-first day of composting. Thermophilic phase lasted approximately 130 days in T1, T3 and T4, while in T2 lasted 30 days. A subsequent drop in the temperature of compost windrows was observed. Noticeable differences among treatments were found demonstrating that olive residues can not be treated exclusively with forced aeration since this system facilitates the compaction of the wastes. [ABSTRACT FROM AUTHOR]

Abstract: Composting of two-phase olive mill waste (TPOMW) mixed with sheep litter and grape stalks was performed using two different aeration systems: forced aeration and windrow turning. The aim was to find out which of these technologies was the most appropriate for the composting of these materials. The efficiency of each aeration method was evaluated by monitoring the evolution of parameters such as temperature, biodegradation of organic matter fractions (carbohydrates, lipids, phenols, lignin, cellulose and hemicellulose) and nitrogen loss. Besides, the quality of the final composts was compared in terms of their main chemical characteristics (total N, N-NH4 +, N-NO3 −, P2O5, K2O, pH, electrical conductivity, polymerisation degree, humification degree and germination index) and their hygienisation degree (faecal coliforms and faecal streptococci). The study revealed that forced aeration of static pile presents several drawbacks for the composting of two-phase olive mill waste due to its physical properties. Several windrow turnings were required to avoid the formation of preferential air path-flows, the compaction and heterogeneous drying of the material. Piles elaborated by windrow turning showed a longer thermophile phase which lead to a higher degradation of fibres and a greater loss of nitrogen. The quality of the end products obtained by both methods was quite similar, although the organic matter of composts prepared by windrow turning had a higher humification degree. Turnings of TPOMW composting piles are necessary for the normal development of the process and the high investment necessary to implement the forced aeration could be avoided. The benefits that forced aeration introduces by means of the control of temperature can be obtained by optimising pile size and turning frequency. [Copyright &y& Elsevier]

When municipal solid waste (MSW) with high content of food waste is landfilled, the rapid hydrolysis of food waste results in the imbalance of anaerobic metabolism in the landfill layer, indicated by accumulation of volatile fatty acids (VFA) and decrease of pH value. This occurrence could lead to long lag time before the initiation of methanogenesis and to the production of strong leachate. Simulated landfill columns with forced aeration, with natural ventilation, and with no aeration, were monitored regarding their organics degradation rate with leachate recirculation. Hydrolysis reactions produced strong leachate in the column with no aeration. With forced aeration, the produced VFA could be effectively degraded, leading to the reduction in COD of the leachate effluent since the week 3. The CH_4 in the landfill gas from the column with aeration rate of 0.39 m^3/(m^3· d) and frequency of twice/d, leachate recirculation rate of 12.2 mm/d and frequency of twice/d, could amount to 40% (v/v) after only 20 weeks. This amount had increased up to 50% afterward even with no aeration. Most of COD in the recirculated leachate was removed. Using natural ventilation, CH_4 could also be produced and the COD of the leachate effluent be reduced after 10 weeks of operation. However, the persistent existence of oxygen in the landfill layer yielded instability in methanogenesis process. [ABSTRACT FROM AUTHOR]

Degradabilities of four kinds of commercial biodegradable plastics (BPs), polyhydroxybutyrate and hydroxyvalerate (PHBV) plastic, polycaprolactone plastic (PCL), blend of starch and polyvinyl alcohol (SPVA) plastic and cellulose acetate (CA) plastic were investigated in waste landfill model reactors that were operated as anaerobically and aerobically. The application of forced aeration to the landfill reactor for supplying aerobic condition could potentially stimulate polymer-degrading microorganisms. However, the individual degradation behavior of BPs under the aerobic condition was completely different. PCL, a chemically synthesized BP, showed film breakage under the both conditions, which may have contributed to a reduction in the waste volume regardless of aerobic or anaerobic conditions. Effective degradation of PHBV plastic was observed in the aerobic condition, though insufficient degradation was observed in the anaerobic condition. But the aeration did not contribute much to accelerate the volume reduction of SPVA plastic and CA plastic. It could be said that the recalcitrant portions of the plastics such as polyvinyl alcohol in SPVA plastic and the highly substituted CA in CA plastic prevented the BP from degradation. These results indicated existence of the great variations in the degradability of BPs in aerobic and anaerobic waste landfills, and suggest that suitable technologies for managing the waste landfill must be combined with utilization of BPs in order to enhance the reduction of waste volume in landfill sites. [Copyright &y& Elsevier]

A novel design of a solid-state bioreactor, operated with periodic pressure oscillation coupled with forced aeration through the medium, gave efficient control of temperature. The evaluation of the bioreactor assembly with respect to temperature and cellulase production by Penicillium decumbens JUA10 showed that, at 4 atm and the bed depth of 6 cm, the maximal temperature variation in the reactor was +1.5 °C at a set value of 30 °C compared with +6.8 °C in a static tray system. The highest cellulase and β-glucosidase activities were 15 IU g-1 and 51 IU g-1 substrate dry matter at 96 h, respectively, while only 10 IU g-1 and 24 IU g-1 were obtained in the static tray culture system. [ABSTRACT FROM AUTHOR]

Quantifying the biodegradation rate of organic contaminants is important in designing and evaluating bioremediation treatments and facilities. To study the effects of temperature and forced aeration on the biodegradation rate, a soil collected from a pipeline break site and contaminated with crude oil was bioremediated in a field-operated bioreactor near Nevis, AB, Canada under four treatments: a control with ambient temperature (averaging 20 deg. C) and no forced aeration; heating alone (averaging 35 deg. C); forced aeration alone (air flux was 0.41 min-1 m-2); and both heating and forced aeration. The soil was aggregated, amended with N and P fertilizers and packed 15-cm deep to a bulk density of 0.65 Mg m-3 in the bioreactor. The effect of temperature on the biodegradation rate of hydrocarbons was also studied under laboratory conditions fortemperatures ranging from 5 to 50 deg. C. Both heating and forced aeration significantly affected the biodegradation of hydrocarbons, butthe effect of the former was greater. Under laboratory conditions, the biodegradation rate of hydrocarbons increased with temperatures, peaking between 30 and 40 deg. C. The half-lives of the hydrocarbons remaining in soil in the field-operated bioreactor were 105 d for boththe heating alone and the heating and forced aeration treatments, 182 d for the forced aeration treatment and 248 d for the control. [ABSTRACT FROM AUTHOR]