Composting And Biogas Production Pdf
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- Design of biogas digester with thermophilic pretreatment for reducing fruits wastes
Biogas is the mixture of gases produced by the breakdown of organic matter in the absence of oxygen anaerobically , primarily consisting of methane and carbon dioxide.
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Microwave assisted with alkaline MW-A condition was applied in the pretreatment of swine manure, and the effect of the pretreatment on anaerobic treatment and biogas production was evaluated in this study. The two main microwaving MW parameters, microwaving power and reaction time, were optimized for the pretreatment. Response surface methodology RSM was used to investigate the effect of alkaline microwaving process for manure pretreatment at various values of pH and energy input.
Results showed that the manure disintegration degree was maximized of Anaerobic digestion results demonstrated that MW-A pretreatment not only significantly increased cumulative biogas production, but also shortened the duration for a stable biogas production rate.
Therefore, the alkaline microwaving pretreatment could become an alternative process for effective treatment of swine manure. Animal manure is one of the major wastes in many agricultural countries due to their intensive animal breeding industry, and it has become a big challenge that should be appropriately treated 1. Moreover, it contained nutrients and heavy metals which will impact the quality of surface and ground water if they are discharged directly 2.
Traditionally, animal manure is treated by anaerobic digestion. The results showed pathogens were destroyed and wastes were stabilized through the process.
However, the high content of fiber in animal manure was limited the efficiency of anaerobic digestion which cannot be well utilized by anaerobic bacteria 5.
Thus, enhanced biogas production by anaerobic digestion has been paid great attention, and substrate optimization has been focused. Carlsson et al. Generally, pretreatment can be roughly divided into three groups, physical pretreatment, chemical pretreatment, and biological pretreatment 7.
Among them, thermo-chemical pretreatment is a main method used in current studies 8 , 9. Alkaline is a simpler and easier handling chemical pretreatment method compared with others, especially when combined with thermal effect.
Currently, MW pretreatment is a favorable thermal pretreatment method. Compared with traditional heating techniques, MW has the advantages of shorter reaction time and lower energy consumption Furthermore, microwave pretreatment when combined with other technologies shows better degradation performance This study was used microwave as pretreatment under alkaline condition MW-A.
By combination of the two different technologies, the performance of pretreatment was significantly improved 12 , Currently, MW was successful used in activated sludge and anaerobic digestion pretreatment 13 , It has great potential to apply in animal manure. However, few research has been reported on MW pretreatment of animal manure.
This study was to investigate the mechanism of MW-A by treating animal manure and consider combination effects of microwaving duration, microwave power, and alkaline dosage.
Furthermore, this study deeply researched the effects of combining pretreatment of alkaline and microwave on anaerobic digestion at various values of pH and ammonium nitrogen AN concentrations. RSM was involved which is a systematic research strategy for studying the interaction of various parameters effect using statistical methods The main objective of this study was to evaluate the effect of pH and energy input on swine manure pretreatment and the effects of pH and AN concentration on the consequent anaerobic digestion of swine manure with various pretreatment by RSM.
The highest DD reached The corresponding second order polynomial fitting equation was as follows:. When P-value is less than 0. The smaller value shows the greater effect In the study, the P-value of model was less than 0. The trend of DD of manure was increase to peak and dropped after. The peak of DD was In order to investigate model accuracy and practicability, the predicted value and actual value were compared in Fig.
The maximum experimental DD of manure was The correctness and validation of the simulation model is demonstrated. The results showed that during anaerobic digestion, The MW-A remained weak alkaline environment, while the microwaving pretreatment and control group turn to acidic.
As shown in Fig. The trend of control group was slightly reduced in the whole process, compared others. The protein concentration of MW-A pretreatment was higher than other two groups.
The protein concentration after alkaline microwaving pretreatment remained a relative high level during the whole anaerobic digestion. The AN concentration during the anaerobic digestion by different pretreatments was recorded and shown in Fig.
As it can be seen in Fig. When pH was more than 8, AN density made little change with the increasing of the reaction time. By the stronger alkaline condition, the AN hardly released from manure. Methane content and cumulative biogas production of manure after different pretreatments. The effect of different pretreatments on total biogas production is shown in Fig. The cumulative biogas production was the highest in MW-A pretreatment group, and then in MW only group, and it was the lowest in control group.
The biogas production rate for MW-A, MW and control groups began to stabilize in 8 days, 14 days and 14 days, respectively. The daily biogas production after different pretreatments is shown in Fig. So the duration for a stable biogas production rate on three groups was 8 days, 4 days, 4 days, respectively. The results showed MW-A pretreatment was not only effectively increased the total biogas production, but also shortens the time for a stable biogas production rate.
This could due to microwave radiation break down the complex structure of the polymer substances, and it can make proteins and sugars enter into a soluble phase 16 , meanwhile alkaline effectively solubilize particulate organic matter and improve the digestibility There was a positive correlation among the DD of manure, the alkaline degree and the energy input.
The 3D response surfaces plot also revealed that the DD of manure increased along with enhancing energy input and alkaline degree see Fig. The results confirmed that the high pH value was benefit for pretreatment. For example, the energy input remained the same but pH levels increased from 8 to 12, the DD rose from The comparison of predicted value and actual value Fig. In general, the appropriate pH is 6. Therefore, if the initial pH was higher than 10 NaOH dose was 0.
In anaerobic digestion process, organic acids were accumulated when the rate of hydrolysis and acidification stages were over methane-producing stage, and this would cause pH decline. On the contrary, pH would enhance when organic acids could not effectively accumulate with similar rate of two stages Methanogens showed more sensitive to pH than acid formation bacteria 22 , though few acidophilic methanogens had been found 23 , most of which could only survive in neutral or weak alkaline environment, the accumulation of organic acids in the process of anaerobic digestion would inhibit the growth of methanogens In Fig.
The protein is the main constituent of manure, and the manure proteins converted to soluble proteins and in hydrolysis and acidification process, respectively. The soluble organics were mainly produced by microwave effect, and absorbed by acid formation bacteria rapidly After burning up initial organics, the hydrolysis of manure began to release soluble organic gradually. The protein content of combined alkaline microwaving pretreatment was relatively higher in Fig.
According the results presented in Fig. Many earlier studies had investigate that pH and AN concentration could affected the methane production By adjusting pH to 8.
The high-solids sludge digester could be operated satisfactorily at pH of 9. The methane yields in mesophilic Anaerobic Digester were optimum at pH of 7. But few studies showed that the relationship between pH and AN concentration. As a results, the AN content was lower in the digester.
The result of Fig. The disintegration degree of manure was the highest after combining alkaline microwaving pretreatment, the substrate of methanogens was plenty and the hydrolysis rate grew rapidly in the beginning of the anaerobic digestion 5. This study showed MW-A group achieved the highest total biogas production than others. The biogas production mainly relies on methanogen.
However, the methanogen was inhibited when excess concentration of AN existed Even though ammonia is an essential nutrient for bacterial growth, it may inhibit methanogenesis during anaerobic digestion process if it is available at high concentrations The MW-A pretreatment seemed to improve the recovery speed and stability of an ammonia-inhibited biogas digester fed with cattle manure The AN concentration was lower and pH presented weak alkalinity during anaerobic digestion process, which was suitable for methanogen growth and consequently improved biogas production.
This study demonstrated that the MW-A pretreatment improved performance of anaerobic digestion by increasing biogas amount and accelerating the reaction rate. The device of microwave reaction includes the microwave power system, reactor chamber and condenser.
The reaction time was controlled by a timer. The microwave reactor schematic is shown in Fig. The swine manure for the experiment was obtained from the rural family swine farms. Fresh manure was smashed and filtered through a 0. Anaerobic digestion experiments were conducted in three glass amber bottles. The control group was set by adding untreated manure to one reactor and keeping the pH value at 7.
In order to maintain strict anaerobic condition, oxygen was removed by nitrogen gas sparging before fermentation. Soluble protein was determined by the Folin phenol method with bovine serum albumin BSA as standard AN was determined by Nessler reagent spectrophotometry
Design of biogas digester with thermophilic pretreatment for reducing fruits wastes
The United States produces more than 70 million tons of organic waste each year. While source reduction and feeding the hungry are necessary priorities for reducing needless food waste, organic wastes are numerous and extend to non-edible sources, including livestock manure, agriculture wastes, waste water, and inedible food wastes. When these wastes are improperly managed, they pose a significant risk to the environment and public health. Pathogens, chemicals, antibiotics, and nutrients present in wastes can contaminate surface and ground waters through runoff or by leaching into soils. Excess nutrients cause algal blooms, harm wildlife, and infect drinking water.
In developing countries, biogas energy production is seen as a technology that can provide clean energy in poor regions and reduce pollution caused by animal manure. Laboratories in these countries have little access to advanced gas measuring equipment, which may limit research aimed at improving local adapted biogas production. They may also be unable to produce valid estimates of an international standard that can be used for articles published in international peer-reviewed science journals. This study tested and validated methods for measuring total biogas and methane CH 4 production using batch fermentation and for characterizing the biomass. Degradation rate assessed by methane formation rate showed wide variation within the batch method tested. The first-order kinetics constant k for the cumulative methane production curve was highest when two animal manures were fermented using the VDI method, indicating that this method was able to reach steady conditions in a shorter time, reducing fermentation duration.
PDF | Production of 'Green gas (Biogas)' generated from 'Hostel Food wastes' (total solids %, moisture content %, volatile solids
Pig manure utilization and valorization is an important topic with tightening regulations focused on ecological and safety issues. By itself pig manure is a poor substrate for biogas production because of its excessive nitrogen content relative to available organic carbon. Such substrate is alkaline, and methanogenesis can be suppressed, and so additional substrates with high organic carbon must be added. The most promising is straw, which is available from adjacent biogas plant cultures.
This study aimed to design a biogas digester that works thermophilically and mesophilically and tested its performance to produce biogas and digestate. This study used some experimental methods, which consists of: 1 design and construction process of the digester which can facilitate the thermophilic process as a pretreatment of the feedstock and the anaerobic digestion process of the substrate; 2 determination of the quantity of biogas, liquid digestate, and compost; and 3 testing digestate quality as a liquid organic fertilizer for Ipomoea reptans. The built biogas digester was able to accommodate thermophilic digestion that runs intensely in the pretreatment tank, where the complex organic compounds, namely cellulose and hemicellulose, decomposed intensively, so that it becomes a suitable substrate.
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