Biodrying Process Research Articles

The Bioconversion of Municipal Solid Waste in the Biodrying Reactor

The bioconversion process of municipal solid waste was assessed on the basis of the results obtained from the biodrying reactor working at a full industrial scale. The bio- reactor is a part of mechanical-biological installation following mechanical stage. The bio-reactor was equipped with measuring devices allowing the analysis of the parameters like: temperature both inside the waste and also air above the waste and also the humidity of waste during the 14 days of the biodrying process. The kinetics of bioconversion was assessed basing on measured the loss of ignition (LOI) parameter detected during the biodrying process. The LOI value of the samples varied from 17.03% d.m. to 30.34% d.m. depending on the location inside the reactor. The estimated kinetic rate constant kT of the bioconversion of biomass in the industrial reactor was kT = 0.3141.In analyzed case study the calorific value of product leaving the full-scale bio-reactor is too low to use this product as an alternative fuel. As was stated, the reason of this is too low a share of the carbon-rich fraction in the feedstock.

Biodegradation of volatile solids and water mass balance of bio-drying sewage sludge after electro-dewatering pretreatment

Using pressurized electro-osmotic dewatering (PEOD) as the pretreatment process for sewage sludge (SS) bio-drying can improve the dewatering performance, but the kinetics of volatile solids biodegradation and the water mass balance are still unknown. These processes were first investigated in this study. Experiments were conducted with three different initial materials, which were composed of SS, bio-dried product and SS dewatered by PEOD (EDSS) as different mass ratios. Six kinetic models and a nonlinear regression method were used to estimate the kinetic parameters, and the models were analyzed using four statistical indicators. Satisfactory fitting of the proposed kinetic model to the experimental data was achieved. Through the water mass balance, the results showed that EDSS had the best dewatering performance for bio-drying. EDSS provided the most appropriate conditions for the bio-drying process; the highest correlation coefficient was 0.9291 and the total water removal rate was 51.13% in the bio-drying of all EDSS.

Effect of sludge char addition on drying rate and decomposition rate of organic waste during bio-drying

To reduce energy consumption in a sludge drying process, sludge treatment process combined with bio-drying and carbonization was newly developed, which reduced the moisture content of the sludge by less than 30%-wet through bio-drying process without adding any auxiliary fuel. In this experiment, bio-drying of dog food, as simulated organic waste sample, in a lab-scale was carried out and effect of sludge char addition on the drying rate and decomposition rate of wet dog food during bio-drying was analyzed. Addition of sludge char to dog food in bio-drying experiment was found to increase the drying rate and to promote decomposition of organic matter. It was also clarified that the drying rate of dog food and decomposition rate of organic matter increased with increasing amount of char addition. Initial amount of filled dog food also influenced drying rate and decomposition rate; the drying rate and decomposition rate increased with increasing dog food amount.

Energetic valorization of MSW compost valorization by selecting the maturity conditions

MSW compost valorization under combustion, at two different composting process conditions, have been studied by thermogravimetric analysis (TGA). The composting operating parameters such as aeration and moisture affect the biodegradability of compost and results of the combustion (different gross heating values for each reactors). The obtained TGA showed that maximum weight loss for 10–12% (245–247 °C), 32–34% (407–411 °C) and 44–46% (760–769 °C) in correspondence to hemicellulose, cellulose and lignin-humic-fulvic acids decomposition for each reactor are observed. Obtained valued in kinetic study (Flynn-Wall-Ozawa method) results in suitable coefficients of determination. In that form, to establish the assumption that combustion of compost under a first-order reaction may be appropriate. Moreover, in both reactors, the conversion rate increased and the activation energy decreased with composting time is found. The maximum gross heating value versus minimum activation energy (for α = 0.25 and α = 0.5) corresponds to final composts and under aeration of 0.050 and 0.175 Lair kg−1 d−1 and moisture of 40% and 55% for R1 and R2 reactors respectively. For MSW, under proper conditions, composting could be used as a suitable biodrying process, stabilizing and concentrating the heating value.

Electro-dewatering pretreatment of sludge to improve the bio-drying process.

In this study, the feasibility of electro-dewatering (EDW) as a pretreatment of the subsequent bio-drying process (EB process) was investigated from the point of view of the influence of EDW on the microbial biodegradability of sludge. The results showed that suitable EDW pretreatment was beneficial for microbial growth in the sludge cake, and in the subsequent bio-drying process it increased the metabolic activity of microorganisms. However, electric field strength impacted microbial activity and soluble chemical oxygen demand (SCOD) of the sludge. As the applied electric field strength increased from 20 to 60 V cm−1, the microbial activity of sludge decreased gradually but SCOD of sludge increased. The specific oxygen uptake rate (SOUR) at electric field strength of 20 V cm−1 was 8.7% higher than that of raw sludge. EDW pretreatment accelerated the drying rate of bio-drying process, and the final water content of sludge (44%) was 6.3% lower than that of non-pretreated sludge. It was observed that in the bio-drying process with an EDW pretreatment, the first peak temperature of the sludge pile was 58.7 °C at 36 h and the second peak temperature was 48.7 °C at 56 h, whereas that of the non-pretreated sludge was only 46.5 °C at 42 h and 40.3 °C at 62 h, respectively. The EDW sludge incorporating straw as a bulking agent showed promising results during bio-drying. In addition, EDW pretreatment of sludge to improve the bio-drying process showed lower energy consumption and cost.

Exploiting community structure, interactions and functional characteristics of fungi involved in the biodrying of storage sludge and beer lees

In this study, the dynamic changes in fungal biodiversity, community structure, fungal associations and functional characteristics were investigated in the biodrying of storage sludge and beer lees by using high throughput sequencing, network and correlation matrix analyses, and FUNGuild database. Additionally, a hypothetical model was provided to better understand the biodrying system. The results showed that fungal diversity decreased after biodrying, while community richness increased in the mesophilic stage and decreased as biodrying progressed. Fungal communities differed in different stages of the biodrying process. Ascomycota and Basidiomycota were the dominant phyla throughout the biodrying process, while Pichia was the dominant genus in the thermophilic stage. Network and correlation matrix analyses provided useful tools for insight into the fungal interactions, allowing us to propose a conceptual model of how succession in fungal associations regulates the dynamics of biodrying systems. Biodrying treatment had a significant effect on fungal trophic modes, with most pathogenic fungi fading away over the process, illustrating that biodrying is an effective bio-treatment method to eliminate pathogenic fungi. These findings provide information that elucidates the fungal interactions and functional characteristics during the biodrying process.

Performance and Bacterial Communities for Bio-drying with Thermophili Bacteria of Sewage Sludge

This study was conducted to evaluate the effect of the sewage sludge treatment method using bio-drying with Ultra-Thermophilic Aerobic Microorganisms (UTAMs). Twelve specific odorous compounds and various sources of bacteria were tested using the sewage sludge treatment method. Sewage sludge was mixed with a seed material and was composted for 47 days. During composting, the temperature was maintained at 80-90oC. The concentrations of the 12 specific odorous compounds after composting did not exceed the allowable exhaust standard for odor. In terms of the bacterial community number after composting, the thermophile bacterial number was 60% of the total bacterial number. The thermophile bacterial ratio after composting increased by 23% compared to the initial composting. The 16S rRNA gene demonstrated that the change in the bacterial community structure was coupled with shifts in the bio-drying process. Therefore, both stable composting operation and economic benefit can be expected when an ultra-thermophilic composting process is applied to sewage sludge.

Thermally assisted bio-drying of food waste: Synergistic enhancement and energetic evaluation

Recently, bio-drying is becoming a promising method to treat the slurry-type food waste together with recovering refused derived fuels (RDFs). In practice, however, conventional process frequently encountered low temperature and inefficient drying performance due to the low microbial activity and organics degradability. In order to improve bio-drying performance, in this study, an externally thermal assistant strategy was proposed to increase water evaporation and stimulate microbial degradability. Based on this idea, a series of experiments were conducted to establish, evaluate and optimize the thermally assisted bio-drying system. It was found that staged heating acclimation was an effective strategy to obtain a superior thermophilic inoculum with high metabolic activity and microbial consortia. In thermally assisted bio-drying process, an extremely high metabolic activity [cumulative OUR, 38.98 mg/(g TS·h)] was obtained, which was greatly higher than that of conventional bio-drying [19.74 mg/(g TS·h)]. Furthermore, thermally assisted bio-drying exhibited a high water-evaporation capacity as thermal drying (157.9 g vs. 147.8 g), which was 3-fold higher than conventional bio-drying. Heat balance calculation indicated that externally supplying a small fraction (12.94%) of thermal energy triggered conventional bio-drying, thus greatly promoting water removal with high energy utilization efficiency as conventional bio-drying (Qevapo 60.30% vs. 64.62%). In addition, the increased air-flow rates greatly accelerated water removal with high bio-energy efficiencies, especially at 0.8 L·min−1·kg−1. The drying effect after 4 days was close to that of 20 days in conventional bio-drying. This research suggests that thermally assisted bio-drying is a promising approach to upgrade conventional bio-drying with high efficiency and low energy cost.

Effect of waste matrix for the optimization of moisture content and calorific value of biodried material using Taguchi DOE

In this study, Taguchi approach was used to determine the influence of waste composition for the optimization of moisture content (MC) and calorific value (CV) of food waste via bio-drying process. The objective was to reduce MC and increase CV of the bio-dried material. The effect of three different levels of four factors including food (FW), paper (Pa), plastic (Pl) waste, and bulking agent (BA) were studied and optimized. The moisture content of the bio-dried material varied between 8.59 and 50.93%, whereas that of the calorific value was 11–25 MJ/kg. The results revealed optimum configurations for MC and CV as FW1Pa3Pl3BA3 and FW1Pa1Pl3BA1, respectively. Regression analysis revealed MC as a positive function of FW and BA with plastic positively correlated with calorific value. ANOVA analysis indicated that FW had more prominent effect on both MC and CV. The predicted and measured values were very close to each other. Additionally, the results realized in the confirmatory experiments at optimized conditions of CV was found to be higher than the test runs of Taguchi design, suggesting that Taguchi method was very successful in the optimization of bio-drying factors for MC and CV.

Insights into the succession of the bacterial microbiota during biodrying of storage sludge mixed with beer lees: Studies on its biodiversity, structure, associations, and functionality

Biodrying was first used for post-treatment of storage sludge mixed with beer lees. In this study, dynamic changes in dissolved organic matter (DOM), bacterial community structure, bacterial associations as well as metabolic functions were investigated using Excitation-Emission Matrix (EEM) spectra, high-throughput sequencing, network and correlation matrix analyses, and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt). Furthermore, a hypothetical model was proposed to better understand the biodrying process. The results showed that desired performance was obtained and DOM variations revealed that biodrying can increase biostability of the matrix. The bacterial communities differed among different stages of the biodrying. At the phylum level, the dominant phyla were Proteobacteria and Bacteroidetes in the mesophilic and cooling phases, whereas Firmicutes became the most dominant phylum in the thermophilic phase. At the genus level, the dominant bacteria in the mesophilic and cooling phases were not obvious, while Ureibacillus and Bacillus were the dominant genera in the thermophilic phase. Network and correlation matrix analyses were useful tools for insights into the bacterial interactions. PICRUSt metagenome inference indicated that metabolism, genetic information processing, and environmental information processing were the primary metabolic pathways. These results allowed us to advance a hypothetical model explaining how succession in bacterial associations regulates the dynamics of a biodrying system.

Bio-drying Technology of Solid Waste to Reduce Greenhouse Gas

Bio-drying technology is a solid waste treatment with a decentralized system, in which solid waste will undergo biological-mechanical bioconversion. The heat generated from the aerobic decomposition process of organic compounds combined with excess air serves to drain solid waste. The bio-drying process will emit VOCs and other gases that potentially cause global warmings such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) gases. The research method used variation of airflow from 0, 2, 3, 4, 5, and 6 l/m. N2O gases were analyzed using Chromatography gas. The results showed that the bio-drying process was able to reduce the water content from 69% to 40% by the thirtieth day. N2O concentration difference between control (no aeration) and waste with bio-drying processing is 534.69 ppb and 175.48 ppb respectively at 1st day. N2O concentration are known when the bio drying process uses a 4 l / m discharge.

The effect of mixing ratio variation of sludge and organic solid waste on biodrying process

In this study, organic waste was co-biodried with sludge cake to determine which mixing ratio gave the best result. The organic waste was consisted of dried leaves and green leaves, while the sludge cake was obtained from a waste water treatment plant in Bekasi. The experiment was performed on 3 lab-scale reactors with same specifications. After 21 days of experiment, it was found that the reactor with the lowest mixing fraction of sludge (5:1) has the best temperature profile and highest moisture content depletion compared with others. Initial moisture content and initial volatile solid content of this reactor’s feedstock was 52.25% and 82.4% respectively. The airflow rate was 10 lpm. After biodrying was done, the final moisture content of the feedstock from Reactor C was 22.0% and the final volatile solid content was 75.9%.The final calorific value after biodrying process was 3179,28kcal/kg.

Microbiological and Energetic Assessment of the Effects of the Biodrying of Fuel Produced from Waste

Abstract Biological drying (biodrying) is one of the methods of biological processing of waste, used mainly as part of the mechanical biological treatment of mixed municipal waste. Biological drying uses the heat released during the decomposition of organic matter to reduce the amount of water in dried waste. The aim of the analyses was to provide a microbiological and energetic (fuel) assessment of the process of biodrying of alternative fuel (RDF) obtained by mechanical sorting of mixed municipal waste. The resulting alternative fuel (obtained with just sorting) is characterised by varied moisture content and the presence of diverse groups of microorganisms. The analyses were intended to assess 3 alternative methods of biodrying of alternative fuel in order to produce a stable end product for utility power generation and the cement industry. The analyses were performed using special bioreactors equipped with custom (innovative) fluidised bed, aeration system (air flow rate 500 m3 · h−1), effluents drain systems, post-process air offtake and 4 temperature sensors. The assessment of the impact of the employed bed aeration methods on the quality of the alternative fuel was performed in 3 repetitions with the same external parameters. The obtained results show that after 8 days of biodrying, in the most favourable option, the moisture content in the fuel was reduced to the level of 18.7%, i.e. by 39%, the resulting fuel was microbiologically stable and the calorific value of the fuel was increased on average by 3.2 MJ · kg−1.

Pre-treatment and utilization of food waste as energy source by bio-drying process

In this study, three different sets of experiments were conducted with the aim of evaluating the effects of initial moisture content and bulking agent on bio-drying efficiency of food waste as well as weight reduction. Results showed that initial moisture content has a significant impact on bio-drying, affecting temperature and water removal rate as well as volatile solid degradation, with higher maximum temperature obtained in Trial 3 (initial moisture content of 44.95 %) and lowest maximum temperature obtained in Trial 1 (initial moisture content of 69.29 %). The bio-drying index indicated that Trial 2 had higher water removal efficiency (72.96 %) with less organics consumption (bio-drying index = 10.1). On the whole, Trial 1, 2 and 3 saw a weight reduction of 54.63 %, 42.56 % and 35.33 % alongside a moisture reduction of 53.26 %, 47.46 % and 64.51 % respectively. This finding suggests that the use of bulking agent has significant effect on the initial moisture content with subsequent impact on bio-drying efficiency which could provide some promising approach to pre-treat organic waste to reduce the moisture content, weight and volume and increase the energy value for solid recovered fuel generation (SRF).

Bio-drying of green waste with high moisture content

Abstract In this study, the effect of bio-drying process on green waste was investigated. Four different sets of bio-drying processes were conducted and the impact of bulking agent (BA) evaluated. The laboratory experiment consisted of a 0.8 m3 bio-drying reactor equipped with a matrix temperature measuring and air supply system. A 50 kg of green waste was placed in the reactor with an uninterrupted airflow rate of 0.3 m3/kg h. The results obtained indicated that the bio-drying process reduced the moisture content (MC) of waste with BA by 27% more than green waste alone after 7 days. Thus, allowing the production of bio-dried waste with a net calorific value of 6265 kJ/kg wet weight, 54% higher than its initial value with 37% decrease in weight in the original mass of the waste. Although on the average, bio-drying of green waste alone showed significant reduction in volume (87%), weight (54%) and increase in calorific value (118%), bio-dried matrix with BA was the most preferred option since the process produced no leachate and generated the highest calorific value.

Lignocellulose biodegradation in the biodrying process of sewage sludge and sawdust

ABSTRACTLignocellulose degradation is important when applying biodrying treatment to sewage sludge intended for land use. This study investigated the lignocellulose degradation in the biodrying of sewage sludge and sawdust. The experiment analyzed lignocellulose content, lignocellulase activity, humic substances, and fungal communities. After biodrying, lignin, cellulose, and hemicellulose degradation rates were 48.4, 38.8, and 45.0%, respectively. Carboxymethyl cellulase, lignin peroxidase, and xylanase played key roles. During the thermophilic phase, more than 80% of the microorganisms in the sample contributing to lignocellulose degradation were Ascomycota. The lignocellulose degradation and a rate of increase in humic acid/fulvic acid of 380% benefit land use of biodrying product.

The effectiveness of biodrying waste treatment in full scale reactor

AbstractThe differences between the composting, stabilization and drying processes were discussed. The law criteria for mechanical-biological treatment plant were presented. The purpose of the article was to assess the effectiveness of biodrying MSW (municipal solid waste) in a full scale reactor taking into account the degree of biological decomposition of organic matter and its suitability for RDF (refuse derived fuel). Therefore the microbial activity was measured as the O2/96 h uptake. CO2/96 h production and the respiration activity AT4 for untreated and biodried waste were compared. The decomposition of organic matter was measured by loss on ignition (LOI) and total organic carbon (TOC). The product after the biodrying process was assessed according to the EURITS and PN-EN 15359 criteria for the quality of RDF (residual derived fuel). The result 8.48 MJ/kg of calorific value shows that bio- dried waste is ranked below the EURITS minimum level and can be classified as fifth class by PN-EN 15359 requirements. The amount of chlorine, mercury and lead fulfil the EURITS criteria. The microbial activity after processing in the biodrying reactor expressed as oxygen uptake exceeded the permissible level of 10 mg O2/g d.m. in the time range ten months. The regulatory parameters TOC < 20% d.m. and LOI < 35% d.m. criteria were not met.

A new model of batch biodrying of sewage sludge, Part 1: Model development and simulations

ABSTRACTThis study proposes a new model of batch biodrying of sewage sludge. This model divided the matrix into two phases (gas and solid), generating 9 · N equations which were solved numerically with Matlab software. A sensitivity analysis was also performed. It was found that the model can represent the experimental trend reported in the literature for the biodrying process, such as higher temperatures (T) for higher initial moisture content (MC) and higher T differences at lower initial MC. The sensitivity analysis shows that the model is mainly affected by changes in parameters kh,rb, kh,sb, µmax, UA, dp, Xsb,0, and XH,0.

Full-scale biodrying process of municipal solid waste

The paper presents the results obtained in the full-scale waste biodrying reactor. The studied facility includes in the biological stage a rectangular-shaped, galvanized steel reactor equipped with a module for active aeration connected with a stove and a bio-filter for removing odours. The undersize fraction (O days in the 150 m3 capasity reactor. Initial moisture content of the untreated waste was 54.65%. Moisture content was declined gradually during biodrying process. Temperature changes during 14th days of biodrying process were monitored with the maximum temperature 70°C. To assess the degree of stabilization of the biodried waste, the determination of the O2 uptake was measured. The oxygen demand of untreated waste was 53.16 mg O2 /g d.m. and after 14th days for biodried waste oxygen consumption was 19.78 mg O2 /g d.m. The results obtained in studies by respirometric dynamic method of oxygen uptake (expressed as O2 /96h parameter) had been compared to the results performed using the static method, where AT4 is the applied indicator.

Effect of air Recirculation on Moisture Removal Efficiency in Combined Hydrolytic–Aerobic Rotary Bio-Drying Process

Rotary bio-drying is the process to reduce moisture from Municipal Solid Waste (MSW) by using the heat from aerobic bio-degradation. This study aimed to investigate the effects of air recirculation on moisture removal efficiency in combined hydrolytic–aerobic rotary bio-drying process for drying high initial moisture content MSW, allowing satisfied moisture content to convert a waste into biofuel energy. The results from the laboratory scale experiments were indicated that increasing the exhaust air recirculation ratio, more moisture increased in the end product. However, while the air recirculation ratio was equals or greater than 50 %, the moisture content of the end product was not significant different.