Forced Aeration System Research Articles

A multi-criteria approach to test and evaluate the efficiency of two composting systems under two different climates

ABSTRACT The selection of the appropriate composting system, climate conditions, and duration of the composting process are important parameters for municipal solid waste composting. Therefore, this research aimed to design, test, and evaluate two different static composting systems under two different climate regions, Palestine and India, following a multi-criteria approach. A forced-aeration composting system was designed for use in Palestine, and a naturally aerated one was used in India. Three experiments were conducted, two of them in Palestine and one in India. The operational parameters were controlled and monitored during the composting process, while the physio-chemical and biological parameters were tested to evaluate the compost end quality. The results showed that both systems provide good efficiency toward formation of final compost (39–43 days in Palestine, and 31 days in India), and the average materials’ volume reduction was almost 60%. The physio-chemical analysis showed that most of the parameters comply with the threshold limits specified by the Palestinian Standards Institution (PSI) and Indian Fertilizer Control Order (FCO) except for minor deviations. Both systems provided a high fertility index (4.3, 4.7, and 4.8), and a high clean index (4.6, 5.0, and 4.7). However, the results of the biological parameters showed that all the experiments met PSI, but none of them met FCO, suggesting that the outer edges of the composting system didn’t heat enough to inactivate pathogenic microbes, therefore, developing the system by adding turning option could overcome this shortcoming. It was concluded that the forced aeration system is suitable for Palestine, while the natural aeration system is suitable for India. Implications: Municipal solid waste management is facing technical and financial challenges worldwide due to the increasing generation of solid waste following the population growth. The current improper management of this waste stream through landfilling is adding pressure on the environment as a result of methane emissions and landfill leachate. Therefore, composting of the organic fraction through selection of an appropriate composting system can solve many waste management problems and contribute to environmental sustainability. This research focuses on design, test and evaluate two composting systems in two regions with different climatic conditions, Palestine and India as both are facing waste management problems. The outcome of this research optimized the composting process which can be replicated and scaled up in other countries worldwide with similar climatic conditions.

Evaluating the Performance of Yarrowia lipolytica 2.2ab in Solid-State Fermentation under Bench-Scale Conditions in a Packed-Tray Bioreactor

Solid-State Fermentation (SSF) offers a valuable process for converting agri-food by-products (AFBP) into high-value metabolites, with Yarrowia lipolytica 2.2ab (Yl2.2ab) showing significant potential under laboratory-scale controlled conditions; however, its assessment in larger-scale bioreactor scenarios is needed. This work evaluates Yl2.2ab’s performance in a bench-scale custom-designed packed-tray bioreactor. Key features of this bioreactor design include a short packing length, a wall-cooling system, and forced aeration, enhancing hydrodynamics and heat and mass transfer within the tray. Preliminary studies under both abiotic and biotic conditions assessed Yl2.2ab’s adaptability to extreme temperature variations. The results indicated effective oxygen transport but poor heat transfer within the tray bed, with Yl2.2ab leading to a maximum growth rate of 28.15 mgx gssdb−1 h−1 and maximum production of proteases of 40.10 U gssdb−1 h−1, even when temperatures at the packed-tray outlet were around 49 °C. Hybrid-based modeling, incorporating Computational Fluid Dynamics (CFD) and Pseudo-Continuous Simulations (PCSs), elucidated that the forced-aeration system successfully maintained necessary oxygen levels in the bed. However, the low thermal conductivity of AFBP posed challenges for heat transfer. The bioreactor design presents promising avenues for scaling up SSF to valorize AFBP using Yl2.2ab’s extremophilic capabilities.

Effect of forced aeration on the biogeochemical cycle of nutrients and metal(loid)s as a remedy for hypoxia in a permanently stratified estuary (Gulf of Trieste, northern Adriatic Sea)

The Timavo River estuary (northern Adriatic Sea) is characterised by strong thermohaline stratification that keeps the deep waters hypoxic. The consequence is an harmful algal bloom at the surface in summer that can be mitigated with a forced aeration system installed at the bottom to improve water oxygenation. The nutrient and metal(loid) cycle was investigated, before and during reoxygenation, using an in situ benthic chamber coupled with sampling and analyses of the water column, sediments and porewater.Dissolved oxygen (DO) decreased along the water column and quickly within the benthic chamber when aeration was not in operation, resulting in hypoxia (2.29 mg L−1) at the bottom and consequent increase in nutrient and metal(loid) concentrations. In contrast, DO levels increased during the activation of the forced aeration system, which proved effective in mitigating oxygen depletion and the efflux of metal(loid)s and nutrients into the overlying water.

A forced aeration system for microbial culture of multiple shaken vessels suppresses volatilization.

Shake-flask culture, an aerobic submerged culture, has been used in various applications involving cell cultivation. However, it is not designed for forced aeration. Hence, this study aimed to develop a small-scale submerged shaking culture system enabling forced aeration into the medium. A forced aeration control system for multiple vessels allows shaking, suppresses volatilization, and is attachable externally to existing shaking tables. Using a specially developed plug, medium volatilization was reduced to less than 10%, even after 45h of continuous aeration (~ 60mL/min of dry air) in a 50mL working volume. Escherichia coli IFO3301cultivation with aeration was completed within a shorter period than that without aeration, with a 35% reduction in the time-to-reach maximum bacterial concentration (26.5g-dry cell/L) and a 1.25-fold increase in maximum concentration. The maximum bacterial concentration achieved with aeration was identical to that obtained using the Erlenmeyer flask, with a 65% reduction in the time required to reach it.

Pig carcass composting using a forced aeration system during different seasons: a field study

Pig carcass composting using a forced aeration system during different seasons: a field study

Study of forced aeration system for fruit and vegetable waste composting

Composting of fruit and vegetable waste (FVW) was investigated in a forced aeration system to determine the effects of aeration rate (AR) and aeration method (AM) on compost quality. Rice husk was mixed with FVW as bulking agent to compost for seven days and aerated in continuous and intermittent at rates of 0.3, 0.6, and 0.9 L min−1. Intermittent aeration at rate of 0.3 L min−1 was observed to have higher initial temperature increasing rate and peak temperature compared to continuous aeration. Moisture loss at rate of 0.3 L min−1 was found smaller than other two rates regardless of AM. With comparison made for similar AR, intermittent aeration had experienced less moisture loss with an average of 17.15 %. The pH of compost was found to vary in aeration method where higher peak pH was found in intermittent aeration at low rate, corresponding to their temperature profile. Largest carbon-to-nitrogen (C/N) ratio reduction was attained by compost treated in intermittent aeration at rate of 0.3 L min−1. Further optimization was performed at a rate of 0.1 L min−1, 0.2 L min−1, and 0.4 L min−1. The result showed an improvement at rate of 0.2 L min−1 in intermittent aeration.

Lignite Improved the Quality of Composted Manure and Mitigated Emissions of Ammonia and Greenhouse Gases during Forced Aeration Composting

Lignite amendment of livestock manure is considered a viable ammonia (NH3) emission mitigation technique. However, its impact on the subsequent composting of the manure has not been well studied. This work compared changes in biochemical parameters (e.g., organic matter loss and nitrogen (N) transformation) and also the emissions of NH3 and greenhouse gases (GHGs) between lignite-amended and unamended cattle manure during forced aeration composting. Amending manure with lignite did not alter the time to compost stability despite delaying the onset of the thermophilic temperatures. Lignite treatments retained N in the manure by suppressing NH3 loss by 35–54%, resulting in lignite-amended manure composts having 10–19% more total N than the unamended compost. Relative to manure only, lignites reduced GHG emissions over the composting period: nitrous oxide (N2O) (58–72%), carbon dioxide (CO2) (12–23%) and methane (CH4) (52–59%). Low levels of CH4 and N2O emissions were observed and this was attributed to the continuous forced aeration system used in the composting. Lignite addition also improved the germination index of the final compost: 90–113% compared to 71% for manure only. These findings suggest that lignite amendment of manure has the potential to improve the quality of the final compost whilst mitigating the environmental release of NH3 and GHGs.

Production of potato (Solanum tuberosum, L.) microtubers using plastic culture bags.

We have developed a system using plastic culture bags with forced aeration system for both liquid medium and gaseous phase to produce microtubers of potato (Solanum tuberosum L.). The production of microtubers under sterile conditions is a good way to produce disease-free materials for crop production, and bioreactors have been used for this purpose. However, bioreactors are expensive and difficult to handle. The plastic culture bags are relatively inexpensive and are easy to store and sterilize because they can be flattened. Microtuber production involves two stages: plant proliferation in one medium, followed by microtuber production in a different medium. Both steps are carried out using the same culture bag. Using this system, we produced 100 to 300 microtubers per 8 l culture bag, depending on the potato cultivar. We varied the nutrient concentrations in the media and found that a lower sucrose concentration in the plant proliferation medium and lower nitrogen concentration in the microtuber production medium both increased the total numbers of microtubers per bag. Notably, a higher concentration of potassium phosphate increased the numbers of larger microtubers. This is beneficial because larger microtubers are much more tolerant to field conditions. We produced about 250,000 microtubers per year in a 66 m2 tissue culture room using the culture bag system. These microtubers have been planted directly in the field and utilized for seed potato production.

EFFECT OF TWO AERATION SYSTEMS ON THE PHYSICOCHEMICAL PARAMETERS DURING COMPOSTING OF THE CATTLE AND POULTRY MANURES

The evaluation of the most suitable aeration technology for cattle and poultry manures composting was carried out using two identical two piles prepared of both manures. Forced ventilation was employed in one of the piles of each manure, whereas mechanical turning was used in the other two piles. The temperature, pH, EC, bulk density, organic carbon, organic matter total nitrogen and C/N ratio were investigated at 0, 1, 7, 20, 35, 50, 65 and 80 days of composting of cattle (CM) and poultry (PM) manures piles under and MTS techniques. In the piles, temperatures degree were 70 and 65 °C at seven days of composting and remained stable up to 40 days. Whereas, the temperatures of MTS piles, peaked 51.0℃ and 58.1 at 7 days of composting period for the CM and PM, respectively, it approximately remained stable up to 50 day. The had a significant impact on the content of organic carbon and OM, of both poultry and cattle manures,in compared to the During the composting periods of all piles showed that, the increase in percentage of total nitrogen was mostly observed in 35 day for forced aeration System FVS piles with poultry and/or cattle manure.The C/N ratio of poultry and cattle manure piles significantly affected with the forced aeration system (Forced Ventilation System FVS) than with the Mechanically Turned System MTS.

Evaluation of the Physical–Chemical and Microbiological Characteristics of the Phospho-Compost Produced Under Forced Aeration System at the Industrial Scale

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. 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. 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). 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.

Structural and construction design of the system and structures of the supply and distribution of air in the treatment of waste

Introduction. Neutralization methods (including composting) are widely used in the technologies of chemical and biothermal oxidation of organic matter. A promising method of waste management is their biothermal composting using controlled gas flows. The methods of process intensification are described: the introduction of inoculating additives, increasing the homogeneity of the mixture, recycling of composts, natural and forced low-pressure and high-pressure aeration, and several others. One example of the implementation of these technologies is the disposal of oil-contaminated soils. Materials and methods. The description of the implemented complexes of biothermal composting of oil-contaminated soils: functional zoning, design solutions. The main functional zones are shown: input control section, intermediate placement area, continuous forced aeration zone (inoculation), periodic forced aeration zone (stacked cavalier biodegradation), and natural aeration zone without mixing (ripening zone). The main element of the complex is the combined aeration system (forced from blower devices and natural mechanical mixing). The expediency of using high-pressure forced aeration to intensify the composting process is shown. Results. The developed mode of operation of the aeration system of the composted mass is described: the initial process of incomplete oxidation of organic matter in stacks of inoculation with a constant air flow and the final decomposition of organic matter with a periodic air flow. The constructive design of the high-pressure forced aeration system used to intensify the composting process is given. Aerobic biothermal composting is performed in aerated piles, which are formed on sites with a waterproof coating. Aeration, necessary to accelerate the decomposition of organic matter in the composts, is carried out in natural (mixing with a ladle) and artificial (purging) conditions. For purging use a system of perforated pipes and blower station. Describes measures to protect pipelines (ducts) from aggressive environmental exposure and increase their service life, to ensure the efficiency of the aeration system in an emergency. Conclusions. The possibility of practical implementation of gas flow control technology in the design, construction and operation of biothermal treatment of waste is shown. The implementation of the projects described in the article showed the need to create a generalized mathematical model that would describe in general terms the behavior of gas flows in heterophase wastes.

Response of the denitrifier community and its relationship with multiple N2O emission peaks after mature compost addition into dairy manure compost with forced aeration

Animal manure is a source of the greenhouse gas nitrous oxide (N2O), 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 N2O emission peaks were observed when the temperature reached at 45, 60 and 72 °C, at the same timing of oxygen consumption peaks. The maximum N2O 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 N2O emission peaks caused by mature compost addition.

A Field-Scale Evaluation of Compost Biofiltration of Ammonia Volatilized from Swine Manure Composting in a Forced-Aeration System

A Field-Scale Evaluation of Compost Biofiltration of Ammonia Volatilized from Swine Manure Composting in a Forced-Aeration System

Composting Roadkill: Research and Implementation by the Virginia Department of Transportation

More than 1.2 million deer–vehicle collisions occurred in the United States in 2014. Transportation departments are the primary agencies responsible for the removal and disposal of millions of wildlife killed on roads each year. In 2009, researchers at the Virginia Transportation Research Council began investigating composting as a means of roadkill management. This research was a response to the shortcomings of landfill and burial (the most common means of disposal in the United States) cited by transportation maintenance staff. Disposal challenges with these methods included long travel distances to landfills, landfill restrictions and costs, and the lack of viable burial areas. This paper summarizes a series of composting studies and describes the implementation efforts that led to a successful composting program for the Virginia Department of Transportation (Virginia DOT). Three roadkill composting methods were found to be effective: static compost windrows, a forced aeration system, and a rotary drum. The study findings of high temperatures, pathogen destruction, and nominal contaminant concentrations in leachate established that these composting methods are not sources of water contamination or pathogen spread. Successful pilot studies at Virginia DOT maintenance facilities led to a growing interest in adopting this method of roadkill management. Implementation efforts included coordination and training within the Virginia DOT and a regulatory agreement with the state environmental agency that allows the Virginia DOT to conduct composting without the more stringent requirements that apply to other types of material. The research findings, implementation efforts, and lessons learned described in this paper will be useful for transportation departments interested in composting as a means of roadkill management.

Effects of aeration rate on degradation process of oil palm empty fruit bunch with kinetic-dynamic modeling

The effect of different aeration rates on the organic matter (OM) degradation during the active phase of oil palm empty fruit bunch (EFB)-rabbit manure co-composting process under constant forced-aeration system has been studied. Four different aeration rates, 0.13Lmin-1kgDM-1,0.26Lmin-1kgDM-1,0.49Lmin-1kgDM-1 and 0.74Lmin-1kgDM-1 were applied. 0.26Lmin-1kgDM-1 provided enough oxygen level (10%) for the rest of composting period, showing 40.5% of OM reduction that is better than other aeration rates. A dynamic mathematical model describing OM degradation, based on the ratio between OM content and initial OM content with correction functions of moisture content, free air space, oxygen and temperature has been proposed.

돈분뇨의 호기적 액비화 과정에서 암모니아 휘산량 평가

BACKGROUND: Composting is the most frequently used waste management process for animal manure in Korea’s livestock industry. In the composting process, a large amount of nitrogen (N) is volatilized to the atmosphere as amonia (NH3). However, quantitative information of NH3 emission from composting of liquid manure is required to obtain emission factors for management of livestock manure in Korea. METHODS AND RESULTS: To evaluate the NH3 emission from composting of liquid manure affected by aeration, we conducted composting of liquid pig manure with three forced aeration systems. The aeration conditions were continuous (A60), cycle of 30 min aeration and 30 min pause (A30S30) and without aeration(A0). All treatments were aerated 12 hour per day with these aeration systems. The total ratio of NH3 volatilization loss to total N content in liquid manure throughout composting period was estimated to 19.9% for A0 treatment, 25.9% for A30S30 treatment and 36.3% for A60 treatment. The A30S30 and A60 aeration systems increased NH3 volatilization by 30.2 and 82.3% compared with systems without forced aeration. CONCLUSION(S): Ammonia emission during liquid pig manure composting was highly affected by forced aeration. The development of liquid pig manure composting systems with forced aeration would be considered both reducing ammonia emission and efficiency of composting.

Influence of Aeration on NH<sub>3</sub>, CH<sub>4</sub> and N<sub>2</sub>O Emissions during Kitchen Waste Composting

Because of high moisture content and compact structure, composting kitchen waste would discharge by-products such as leachate, ammonia (NH3), and greenhouse gases, and these can cause secondary environmental pollution. In this study, continuous measurements of gas emissions were carried out and detailed gas emission patterns were obtained using forced aeration system at aerations of 2·10-4 (T1), 4·10-4 (A2) and 6·10-4 ( (A3) m3·kgDM-1·min-1. During the experiment, temperature and oxygen content were determined, and continuous measurements of NH3 and gaseous emissions (CH4, N2O, and NH3) were taken. The results indicated that the aeration had a significant effect on NH3, CH4 and N2O emission (p<0.05). The highest concentration of NH3, CH4 and N2O were all observed in the treatment of T2. The productions of NH3 were reduced by 59.6% and 33.7%, and greenhouse gases (GHG) were reduced by 50.8% and 40.5% for T1 and T2 that compared to T3, respectively. Obviously, the aeration has great influence on NH3 and GHG emissions. In this study, the aeration was 2·10-4 m3·kgDM-1·min-1 in favor of NH3 and GHG reduction.

Effect of phosphogypsum and dicyandiamide as additives on NH3, N2O and CH4 emissions during composting

A laboratory scale experiment of composting in a forced aeration system using pig manure with cornstalks was carried out to investigate the effects of both phosphogypsum and dicyandiamide (DCD, C2H4N4) as additives on gaseous emissions and compost quality. Besides a control, there were three amended treatments with different amounts of additives. The results indicated that the phosphogypsum addition at the rate of 10% of mixture dry weight decreased NH3 and CH4 emissions significantly during composting. The addition of DCD at the rate of 0.2% of mixture dry weight together with 10% of phosphogypsum further reduced the N2O emission by affecting the nitrification process. Reducing the phosphogypsum addition to 5% in the presence of 0.2% DCD moderately increased the NH3 emissions but not N2O emission. The additives increased the ammonium content and electrical conductivity significantly in the final compost. No adverse effect on organic matter degradation or the germination index of the compost was found in the amended treatments. It was recommended that phosphogypsum and DCD could be used in composting for the purpose of reducing NH3, CH4 and N2O emissions. Optimal conditions and dose of DCD additive during composting should be determined with different materials and composting systems in further study.

Low greenhouse gas emissions during composting of solid swine manure

Methane and N2O fluxes during composting of solid swine manure were studied using three aeration systems being, forced aeration (FA), wire mesh (WM) and turnover (TO) and no aeration, for 85d to suggest strategies of mitigating GHG emissions during composting. Manure was collected from a swine research barn by a scraper system and mixed with sawdust as a bulking agent. The manure sawdust mixture was placed in linear low density polyethylene containers for each composting method. A steady state chamber covering each container was used to measure CH4 and N2O fluxes during composting in order to sample temporal and spatial heterogeneous fluxes. Air samples were continuously analyzed for CH4 and N2O by a high frequency trace gas analyzer. Mean CH4 fluxes from FA, WM, TO, and no aeration were 5.2, 3.8, 7.5, and 34.6μg/m2/s, respectively. Mean N2O fluxes from FA, WM, TO, and no aeration were 1.6, 3.1, 7.9, and 11.4μg/m2/s, respectively. Ratios of CO2-equiv. emitted from FA, WM, TO and no aeration were 0.14, 0.24, and 0.59, respectively. Nitrous oxide was the main contributor to CO2-equiv. fluxes. The FA system had the lowest emissions, but WM had the advantage of not requiring electricity for aeration.This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.

Influence of aeration on CH 4, N 2O and NH 3 emissions during aerobic composting of a chicken manure and high C/N waste mixture

Co-composting of chicken manure, straw and dry grasses was investigated in a forced aeration system to estimate the effect of aeration rates on NH 3, CH 4 and N 2O emissions and compost quality. Continuous measurements of gas emissions were carried out and detailed gas emission patterns were obtained using an intermittent-aeration of 30 min on/30 min off at rates of 0.01 (A1), 0.1 (A2) and 0.2 (A3) m 3 min −1 m −3. Concentrations of CH 4 and N 2O at the low aeration rate (A1) were significantly greater than those at the other two rates, but there was no significant difference between the A2 and A3 treatments. CH 4 and N 2O emissions for this mixture could be controlled when the composting process was aerobic and ammonia emissions were reduced at a lower aeration rate. Comparison of CH 4, N 2O, NH 3 emissions and compost quality showed that the aeration rate of the A2 treatment was superior to the other two aeration rates.