Biofuels
Mojtaba Malekzadeh; Reza Yeganeh; Bahram Ghamari; shaban ghavami jolandan
Abstract
Introduction: Biogas is a natural and cost-effective source of energy that leaves significant impacts on the environment and industries, widely produced and utilized in many countries. This gas is generated through the anaerobic digestion of organic materials, including animal manure, food waste, and ...
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Introduction: Biogas is a natural and cost-effective source of energy that leaves significant impacts on the environment and industries, widely produced and utilized in many countries. This gas is generated through the anaerobic digestion of organic materials, including animal manure, food waste, and sewage. Microorganisms play a crucial role in the biogas production process by feeding on biomass. The digestion carried out by these microorganisms produces methane, constituting approximately 50-70% of biogas, which is flammable and used for cooking, cooling and heating, electricity generation, methanol and steam production, waste management, and mechanical power. Given these benefits, biogas production holds special significance, and extensive research has been conducted globally in this field, yielding valuable results. In the present study, we aim to investigate and evaluate the influence of lentil skin as a biomass on the quantity and constituents of produced biogas.Materials and Methods: This research was conducted in the Biosystems Mechanics Workshop of the Faculty of Agriculture, Ilam University. The objective of this study was to investigate the effect of lentil skin on biogas production and analyze its constituent components. The workflow typically comprised four stages. In the first stage, fresh lentil skins were broken down into smaller pieces and stored in a suitable environment to be used as digester feedstock for the experiment. Shredding organic waste aids in the digestion process. The second stage involved providing optimal conditions for microbes, which require warmth. Accordingly, the temperature was maintained at an average of 28-30 degrees Celsius during the experiment.The third stage involved the actual digestion process, where anaerobic digestion took place in large tanks, resulting in real biogas production. For this purpose, materials were combined in predetermined proportions (1:1) and loaded into the digesters. In each stage, 5 kilograms of lentil skin were combined with 5 kilograms of water and added to the digester. The experiment was conducted in three repetitions, employing fixed digesters, digesters with agitation every three days, and digesters with daily agitation as influencing factors. The quantity of biogas production and its components were examined over a 30-day period. Gas sampling occurred every 10 days, while pH and gas pressure were measured every 72 hours. In the final stage, the gas underwent purification by removing impurities and carbon dioxide. The amount of gases produced from lentil skin was measured using a chromatograph with a TCD detector. This instrument employs chromatography-based separation. It's worth noting that 9 gas capsules specifically designed for automobiles were used to construct the digesters. The construction stages of the digesters included cleaning, coloring, and installing connections. Moreover, to create uniform temperature and concentration conditions inside the tank, inlet and outlet connections were carefully designed and installed. A safety valve was also installed to ensure the safety of the digesters.Results and Discussion: The obtained results, including loading conditions, pH levels, and internal pressure within the digester during the experiment, and the quantity and components of biogas, were examined across all samples. Statistical methods, including Analysis of Variance (ANOVA) and Duncan's mean comparison test, were employed for data analysis. The results indicated that digester agitation directly influences the pH levels, with the highest pH observed in digesters with daily agitation, displaying the most significant fluctuations. Furthermore, digester agitation has a direct impact on the biogas production levels, enhancing structural effects within the digester. However, frequent agitation repetition has a negligible effect on the amount of biogas produced. The average methane production rates in this process were 34.06% mol for digesters with daily agitation, 23.09% mol for digesters with agitation every three days, and 17.32% mol for fixed digesters.Conclusion: Currently, a significant portion of the world's energy demand is met through fossil fuels, the combustion of which releases carbon dioxide and various pollutants, including sulfur and nitrogen oxides, which are highly harmful. Consequently, in recent years, there has been a growing inclination towards utilizing various renewable energy sources. One crucial energy source that also provides a solution for waste reduction is biogas. Given the increasing importance of sustainable energy development and the need for waste management, anaerobic digestion technology and biogas production have rapidly grown. Therefore, the findings of this research underscore the importance of exploring innovative methods and utilizing diverse biological resources in managing and optimizing the biogas production process.
Biofuels
Mostafa Parsaee; Mostafa Kiani Deh Kiani; Zabiollah Mahdavifar
Abstract
Introduction Anaerobic digestion has progressed rapidly since the late 1960s. With the progress of the anaerobic fermentation process in the world, anaerobic reactors have been developed to digest different types of organic wastes in each country. So various types of reactors have been built, and that ...
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Introduction Anaerobic digestion has progressed rapidly since the late 1960s. With the progress of the anaerobic fermentation process in the world, anaerobic reactors have been developed to digest different types of organic wastes in each country. So various types of reactors have been built, and that they have been in different shapes, dimensions, and operating conditions. One of these reactors is the static granular bed reactor (SGBR). SGBR with its granular bed digests a substrate in less hydraulic retention time (HRT). SGBR is a downstream reactor that consists of active anaerobic granules. The biomass contacts the granular surfaces and does not require the use of mixers, gas, solid, and a separator. The reactor startup is very short since there is no need for some operations, such as extra time to grow microorganisms in the granule. One of the most important residues in the alcohol production plant from molasses is vinesse which has become a major problem in this industry. The conversion of vinasse to biogas and using it to supply the energy of the industry is one of the basic ways to solve this problem. Several studies have been conducted in this field by using various reactors, but there is no research about SGBR. In this study, an SGBR producing biogas from vinasse has been designed and constructed. Also, the performance of the reactor was investigated at three HRTs (2, 3, and 4 days) and the thermophile temperature of 55 °C. Materials and Methods The best diameter to height ratio (reactor volume) in the SGBR is 1:7. Accordingly, the shape of the reactor is a pipe. Based on the volume of the reactor and the maximum pressure inside it, a 4-inch polyethylene tube with a height of 1 meter was selected to carry out the testes. According to the thermophile temperature (55 °C) and the accuracy of the element (0.9 °C), the maximum temperature of the reactor is 329 K. Therefore, the minimum power for obtaining this temperature is 405.316 watts. The water displacement method was used to measure the amount of biogas. An iron sponge was used for removing hydrogen sulfide gas from biogas. Sodium hydroxide solution was used to remove carbon dioxide from biogas. Results and Discussion The reactors were loaded daily with organic matter (86002, 28667, and 21500 mgCOD/L.d) for different HRTs (2, 3, and 4 days). For three HRTs, the amount of methane production was high during the first day which is due to the thermal shock caused by the microorganisms in the granule. Methane production in HRT of 2 days had fewer variations than HRT of 3 and 4 days, and after 13 days, it reached a nearly constant value of 4600 ml/day. For HRT of 3 days, the daily rate of methane production reached a constant value of 4800 ml/day after 12 days and for HRT of 4 days, it reached 4,900 ml/day after 10 days. For HRTs of 2 and 3 days, the rate of methane production per unit of volatile solids had less variation and remained constant approximately after 7 days. The average methane production per unit of volatile solids at HRT of 4 is days higher than the other HRTs. The average methane production for HRTs of 2, 3, and 4 was 379, 380, and 433 CH4 (L)/VS (kg), respectively. The maximum value of methane production was 582 m3/kgCOD, which was obtained at HRT of 2 days. In this study, 31 liters of methane were produced per one liter of vinasse at HRT of 4 days, which was more than other studies. Conclusion In this study, the required heat power and pressure inside the SGBR laboratory have been calculated. The minimum required heat is 261 watts. Also, this reactor should be able to bear at least 4.34 bar for biogas production. The average amount of methane production per unit of volatile solids was 379, 380, and 433 CH4 (L)/VS (kg) at HRTs of 2, 3, and 4 days, respectively. The maximum amount of produced methane was 582 m3/kgCOD, which was achieved at HRT of 2 days, and the maximum percentage of COD reduction was 39%, which was achieved at HRT of 4 days. In general, the results indicated that SGBR produced higher biogas from vinasse than other reactors, but it is not suitable for reducing pollutions.
