Biodrying Of Municipal Solid Waste Research Articles

Development of solid recovery fuel for power generation with bacterial bio-drying of municipal solid waste in Lombok Island West Nusa Tenggara

Abstract The growth of waste in big cities in Indonesia increases sharply every year. The Government’s ability to manage solid waste only reaches 40.09% in urban areas and 1.02% in rural areas, so the right policies are needed so that Municipal Solid Waste (MSW) does not save potential problems that will impact the future. The waste problem is no longer just a matter of cleanliness and the environment but has become a social problem that has the potential to cause conflict. The most likely solution to solving the MSW problem is to use it as a source of alternative fuel, which can be done by a mechanical-biological treatment technology into Solid Recovery Fuel (SRF). The proposed SRF processing method is straightforward and requires a little technology; thus, it could be developed at the community level. The MSW is collected and processed by communities and then sold to power plants or factories or used in communities to replace solid fuels such as wood or charcoal. Compared with the standard RDF and SRF specifications, MSW SRF falls under medium-grade Refuse Derived Fuel (RDF) or SRF specifications. Further comparison with coal, water hyacinth SRF, and sorghum shows that MSW SRF has several advantages, such as low fixed carbon, sulfur, and moisture, that could be beneficial for combustion performance, which concludes that MSW has potential and meet the specification as an alternative fuel for thermal power plant or other industry that utilizes thermal energy. This paper proposes a processing methodology for municipal solid waste into alternative energy. The method could guide local people in using biomass resources to improve local economic prosperity.

Carbon conversion during biodrying of municipal solid waste generated under tropical Asian conditions

Carbon conversion during biodrying of municipal solid waste generated under tropical Asian conditions

Development of mathematical model and experimental Validation for batch bio-drying of municipal solid waste: Mass balances

Bio-drying of solid waste is a complex process that involves anoxic hydrolysis, aerobic oxidation, evaporation, absorption, and condensation. To understand the interaction between different variables (concentration of volatile matter, moisture, microbial biomass, and temperature) and to predict the system performance, a powerful tool is necessary for improved drying rates. Hence, a mathematical model of mass balances of the batch bio-drying of municipal solid waste (MSW), associated with rate equations of evaporation of moisture from the waste matrix and absorption of leachate on absorbents is developed which is the novelty of the present study. This model integrates 18 first-order differential equations based on process kinetics for mass balances of components in the solid, liquid, and gas phases, comprising the specific degradability of food, paper, and inert material of the MSW. The proposed model is simulated using MATLAB ode15s solver and validated with experimental data from the pilot-scale bio-drying reactor. The model predicted values are in good agreement with experimental values with a deviation of ±10%.

Comparison of temperature and oxygen concentration driven aeration methods for biodrying of municipal solid waste

In this study, we used a model bio drying reactor to optimize the drying of municipal solid waste (MSW). Two methods of aeration were used: one involved controlling the concentration of oxygen (16–20%) and the other the temperature in the upper part of the reactor (temperature 42–45 °C, oxygen concentration 16– 20%). In terms of moisture content, the highest increase recorded was 0.94% and the highest decrease was 27.54%. The highest decrease in lower calorific value recorded was 9.23% and the highest increase was 41.12%. The energy balance in all the trial runs was positive. We noted that aeration using different concentrations of oxygen is strongly influenced by organic content. Thus, it is suitable only for drying wastes with known and stable compositions. The outcomes of the different methods used were influenced by ambient relative air humidity. Moisture gradients, which are often described in the literature, were not consistently reproduced in this study.

Biodrying of Municipal Solid Waste

Biodrying of Municipal Solid Waste

Effects of inoculation amount and application method on the biodrying performance of municipal solid waste and the odor emissions produced

The effects of inoculation amount and application method on the biodrying of municipal solid waste (MSW) was investigated in this study. Results showed that a low level (5%) of inoculation with mature compost significantly improved the biodrying index (4.96), while adding greater amounts decreased the biodrying performance by increasing the volatile solid degradation rate. Covering the pile with inoculation material resulted in the highest water removal (72.7%) and greatest water content reduction (from 60.2% to 17.7%). Meanwhile, first covering and then incorporating the inoculation material into the biodrying pile did not improve biodrying performance. Clearly, addition of varying amounts of inoculation material via different application methods enhanced cellulose degradation rates by 2.3–14.2%. Using 10% inoculation material reduced the NH3 emissions by 39.1–54.3% regardless of inoculation method, inoculation amount had a greater effect on NH3 emissions than that of inoculation method. The covering inoculation material could reduce 65.08% H2S emission, the inoculation method had a greater effect on H2S emissions than that of inoculation amount. Given the comprehensive considerations of emission reduction and biodrying performance, a covering of 10% inoculating material is a suitable approach to improve biodrying performance and mitigate odorous gases emissions.

Biological drying of municipal solid waste from landfill

The aim of this work was to investigate the process of biodrying of municipal solid waste from the old landfill to preparing it for pyrolysis or gasification. New aspect of this research is biodrying of waste from old landfill. Biodrying of wastes was carried out at different aeration rates (7, 35, and 175 dm3/kg dry matter/d) at two temperatures (23 and 50 °C). The research was carried out in the laboratory bioreactors of special design (lysimeters), which simulated the conditions prevailing in the landfill. The optimal conditions for reduction of moisture in waste (63.2%) has been attained for the highest aeration rate (175 dm3/kg dry matter/d) and temperature equal to 50 °C. The final moisture content of the obtained biodried product was 23% w/w. In the bioreactor, in which the greatest reduction of moisture was obtained, the total amount of produced CO2 was 44.9 gC/kg dry matter, and the biodrying efficiency was equal to 0.89. During biodrying of wastes in optimal conditions, higher heating value of waste increased from 4.3 to 11.0 MJ/kg. As a result of the performed pyrolysis of biodried waste at 900 °C, char, oil, and gas were obtained the respective yields of 47, 32, and 21% w/w. The gas emerging in the gasification process was characterized by higher heating value equal to 11.3 MJ/m3.

Biodrying of municipal solid waste under different ventilation periods

Biodrying is a pre-treatment method that applies biological and mechanical concepts to drying solid waste. In Malaysia, municipal solid waste (MSW) is unseparated and contains a high level of moisture, making the use of technology such as solid waste burning unsuitable and harmful. MSW containing organic material can be processed naturally until the moisture content of the waste is reduced. This study on MSW biodrying was carried out on a laboratory scale to measure the percent moisture content reduction and to monitor temperature patterns under different ventilation periods. This work was conducted using five biodrying reactors volumes of 50 liters each. Reactors were ventilated for 5, 10, 15, 20 and 30 min every 3 h, with a 3 bar air supply. The duration of this process was 14 days for all samples. The results showed that the optimum ventilation time was 10 min, with an 81.84% reduction in moisture content, and that it required almost half of the electricity cost required for the 20 and 30 min ventilations.

Impact Of Aerobic Biostabilisation And Biodrying Process Of Municipal Solid Waste On Minimisation Of Waste Deposited In Landfills

Abstract The article discusses an innovative system used for aerobic biostabilisation and biological drying of solid municipal waste. A mechanical–biological process (MBT) of municipal solid waste (MSW) treatment were carried out and monitored in 5 bioreactors. A two-stage biological treatment process has been used in the investigation. In the first step an undersize fraction was subjected to the biological stabilisation for a period of 14 days as a result of which there was a decrease of loss on ignition, but not sufficient to fulfill the requirements of MBT technology. In the second stage of a biological treatment has been applied 7-days intensive bio-drying of MSW using sustained high temperatures in bioreactor. The article presents the results of the chemical composition analysis of the undersize fraction and waste after biological drying, and also the results of temperature changes, pH ratio, loss on ignition, moisture content, combustible and volatile matter content, heat of combustion and calorific value of wastes. The mass balance of the MBT of MSW with using the innovative aeration system showed that only 14.5% of waste need to be landfilled, 61.5% could be used for thermal treatment, and nearly 19% being lost in the process as CO2 and H2O.

Influence of Aeration Modes on Aerobic Bio-Drying of Municipal Solid Waste (MSW)

The process of biodrying could be a good solution for municipal solid waste management, allowing the production of fuel with an interesting energy content. In this study, bio-drying the mixed municipal solid waste (with the size among 15-80 mm) with different aeration modes were conducted. During the experiment, temperature, oxygen content and moisture content were determined, and continuous measurements of H2S and CH4 were taken. The results indicated that the thermophilic phases of all treatments beside T1 were met the Chinese standard of >55°C for 5-7 days for sanitation. The aeration mode of T4 was in favor of reduced the H2S and CH4 emission during MSW bio-drying. Under the condition of this study, the bio-drying cycle should be determined for 18 days. Intermittent ventilation mode is more effective to reduce the moisture content in MSW bio-drying process. So the aeration mode of T4 (2.0L/min, 30min run/30 min stop) was the first choice during MSW bio-drying.

Optimization of biodrying pretreatment of municipal solid waste and microbial fuel cell treatment of leachate

The biodrying pretreatment of municipal solid waste (MSW) and the treatment of leachate were investigated. The biological oxygen demand (BOD) and NH4+-N concentration of leachate from MSW biodrying pretreatment were measured, and the optimal conditions for MSW biodrying pretreatment and microbial fuel cell (MFC) performance were established. The results show that the optimal temperature and time for biodrying pretreatment of MSW were 40°C and 6 day, resulting in 30% weight loss of MSW, 20,800 mg/L leachate BOD, and 1,410 mg/L leachate NH4+-N. Effects of leachate properties on MFC performance were then studied. The optimal conditions for electricity generation of the MFC were neutral pH, 5,093 mg/L leachate BOD, and 341 mg/L leachate NH4+-N. The stable voltage of MFC generated using diluted leachate was 0.32 V, and the removal efficiencies of BOD and NH4+-N by the MFC were 86.0 and 88.8% after 7 day of treatment, respectively. These findings provide guidelines for the pretreatment of MSW and the treatment of leachate, and for further research and actual engineering application.

Biodrying of municipal solid waste under different ventilation modes: drying efficiency and aqueous pollution

Ventilation is very important during the biodrying process because it affects the biodrying efficiency and secondary pollution. In this study, three ventilation modes-intermittent negative ventilation (IN), continuous negative ventilation (CN) and intermittent positive ventilation (IP)-were used to provide the same amount of total air during biodrying of municipal solid waste (MSW). During the entire 16-day experiment, 68.4%, 68.7% and 67.2% of water contained in the initial waste was removed under IN, CN and IP trials respectively. The ratio of water loss to volatile solid loss was used to evaluate the biodrying efficiency, with values of 5.35, 5.93 and 4.82 being observed for IN, CN and IP trials respectively. The total organic carbon concentrations of the leachate generated from the biodrying of waste were as high as 25,000 mg/l, while those of the condensate were not higher than 3500 mg/l. During the entire process, the average ammonia concentrations of leachate and condensate were 1350 mg/l and 2140 mg/l respectively. From the aspect of biodrying efficiency, continuous negative ventilation was the most preferable ventilation mode for biodrying of MSW, while special care should be taken to prevent aqueous pollution if it is used in a MSW treatment plant.

Release of volatile organic compounds during bio-drying of municipal solid waste

Three treatments were tested to investigate the release concentrations of volatile organic compounds (VOCs) during the bio-drying of municipal solid waste (MSW) by the aerobic and combined hydrolytic-aerobic processes. Results showed that VOCs were largely released in the first 4 days of bio-drying and the dominant components were: dimethyl disulfide, dimethyl sulfide, benzene, 2-butanone, limonene and methylene chloride. Thus, the combined hydrolytic-aerobic process was suggested for MSW bio-drying due to fewer aeration quantities in this phase when compared with the aerobic process, and the treatment strategies should base on the key properties of these prominent components. Malodorous sulfur compounds and terpenes were mainly released in the early phase of bio-drying, whereas, two peaks of release concentrations appeared for aromatics and ketones during bio-drying. Notably, for the combined hydrolytic-aerobic processes there were also high concentrations of released aromatics in the shift from hydrolytic to aerobic stages. High concentrations of released chlorinateds were observed in the later phase. For the VOCs produced during MSW bio-drying, i.e., malodorous sulfur compounds, terpenes and chlorinateds, their release concentrations were mainly determined by production rates; for the VOCs presented initially in MSW, such as aromatics, their transfer and transport in MSW mainly determined the release concentrations.

Bio-drying of municipal solid waste with high water content by aeration procedures regulation and inoculation

To improve the water content reduction of municipal solid waste with high water content, the operations of supplementing a hydrolytic stage prior to aerobic degradation and inoculating the bio-drying products were conducted. A ‘bio-drying index’ was used to evaluate the bio-drying performance. For the aerobic processes, the inoculation accelerated organics degradation, enhanced the lignocelluloses degradation rate by 10.4%, and lowered water content by 7.0%. For the combined hydrolytic–aerobic processes, the inoculum addition had almost no positive effect on the bio-drying efficiency, but it enhanced the lignocelluloses degradation rate by 9.6% and strengthened the acidogenesis in the hydrolytic stage. Compared with the aerobic processes, the combined processes had a higher bio-drying index (4.20 for non-inoculated and 3.67 for the inoculated trials). Moreover, the lowest final water content occurred in the combined process without inoculation (50.5% decreased from an initial 72.0%).

Biodrying of municipal solid waste with high water content by combined hydrolytic-aerobic technology

The high water content of municipal solid waste (MSW) will reduce the efficiency of mechanical sorting, consequently unfavorable for beneficial utilization. In this study, a combined hydrolytic-aerobic biodrying technology was introduced to remove water from MSW. The total water removals were proved to depend on the ventilation frequency and the temporal span in the hydrolytic stage. The ventilation frequency of 6 times/d was preferable in the hydrolytic stage. The hydrolytic span should not be prolonged more than 4 d. At this optimal scenario, the final water content was 50.5% reduced from the initial water content of 72.0%, presenting a high water removal efficiency up to 78.5%. A positive correlation was observed between the organics losses and the water losses in both hydrolytic and aerobic stages (R = 0.944, p < 0.01). The evolutions of extracellular enzyme activities were shown to be consistent with the organics losses.

Modelling of PCDD/F release from MSW bio-drying

In the present work, an experimentation was carried out to study the behaviour of PCDD/F during the process of municipal solid waste (MSW) bio-drying. This process belongs to the biological mechanical treatment (BMT) options and is aimed to the dewatering of MSW thanks to the biological exothermal reactions (thermal drying, on the contrary, needs an external heat source as methane). The result is a decrease of waste weight and an increase of lower heating value (as the energy content refers to a lower amount of waste). Of course, the overall energy availability does not increase, but the characteristics of bio-drying are interesting as a way for refuse derived fuel generation: glass, metals and inert removals are easier after bio-drying. The literature of the sector shows only few data on PCDD/F emission to air from BMT. Anyway, in the present work an original theory has been put forward in order to explain the enrichment of PCDD/F in the air exiting the biological processes. The role of the initial PCDD/F concentration in the ambient air entering the plant is obviously taken into account. The results of the developed experimentation and the following elaborations point out that PCDD/F could be freed from the volatile solids consumed during the process. The different amount of PCDD/F in the waste and the different consumption of volatile solids depending on the biological process can explain the different PCDD/F emission factors available in the literature.

Lower Heating Value Dynamics during Municipal Solid Waste Bio-Drying

In agreement with the new European Union directives concerning the valorization of materials and energy recovery, Municipal Solid Waste (MSW) management is, in general based on an integrated approach characterized by a combination of different treatment processes. The bio-mechanical treatment (BMT) of MSW is an increasing option in Europe either as a pre-treatment before landfilling or as a pre-treatment before combustion. In this context the research on the bio-drying process is not fully developed. In the present paper the Lower Heating Value (LHV) dynamics during MSW bio-drying has been assessed. Measurements were made using a pilot scale bio-dryer that allows the recording of data as air flow, temperature (at the entrance, at the exit and inside the waste), and weight loss. An initial characterization of the MSW completes the input data. Results give information on the dynamics of the main process parameters (humidity, volatile solids, ammonia, Lower Heating Value) and also of additional parameters.