This work aimed to assess the production of biogas from locally widely available food waste likes; potatoes, tomatoes and carrots that are extensively used in Iraqi cuisine. Three digesters were used in the fermentation process, as well as two small digesters, where the effect of the buffer solution was tested. The effect of cellulose and starch content were studied since they are dominant in these food types. The highest amount of the biogas production was obtained from potatoes which contain a high amount of starch and an ideal ratio of carbon to nitrogen ratio. The lowest amount of biogas was from tomatoes which contain a high percentage of cellulose as well as the lowest carbon to nitrogen ratio. Tomato fermentation continued for 90 days, while potato and carrot continued for 105 days. Digestion in the smaller reactors gave better production by controlling the PH value. The production was 280 ml in 23 days while the uncontrolled digestion was 240 ml in 34 days. The production in the seventh week began to rise gradually until the end of the experiment. The proportion of methane in the digestion of tomato was almost 59. The digestion of potatoes associated with higher PH than that in tomato digestion. It began to produce methane in the fifth week of the experiment giving higher methane production of 69 proportion. Carrots produced methane in the fourth week of the experiment in a less period than potatoes. The proportion of methane was about 64. Potatoes production was better than carrot and tomatoes. The use of bio-active bacteria in the second test gave better results compared to the first test in reducing fermentation period as well as increase production.
The present study outlines a mathematical framework for evaluating the energy and exergy efficiency of charging operations involving two distinct phase change materials (PCMs) denoted as PCM1 and PCM2, as well as various heat transfer fluids (HTF) and thermal energy storage (TES) systems. Using a phase change material (paraffin wax RT55 and lauric acid) in a concentric thermal storage system is investigated experimentally herein using a triple pipe heat exchanger (TPHX). As part of a three-pipe (TPHX) system, the innermost pipe transports water (hot water). The inside pipe of the exchanger is coated with paraffin wax, while the outer pipe is constructed of lauric acid. To this end, experiments were conducted to examine how changes in flow rates, input temperatures, and Stefan numbers (selected in response to charge situations) affect PCM's energy and exergy calculations. Energy-exergy efficiency and entropy generation were both found to be enhanced by increasing the intake flow rate and temperature. As the intake flow rate is increased from 11 L/min to 52 L/min, the complete melting time is reduced by 12%, 15.7%, and 19.09% for PCM1, while reduce by 23.25%, 24.5%, and 25% for PCM2, while as the input temperature is increased from 316 K to 328 K, the melting time is reduced by 36.2%. Also, the results show that the energy stored, energy efficiency and exergy efficiency at PCM1 is bigger than PCM2 at same flow rate. Where energy storge increase by 15% at minimum flow rate and 12.85% at maximum flow rate, the energy efficiency of PCM1 increase by 47% then PCM2 at maximum flow rate, while increase by 43% at minimum flow rate, while exergy efficiency of PCM1 increase by 9.45% then PCM2 at maximum flow rate, while increase by 8.47% minimum flow rate. Evaluating the Nusselt number and the entropy generation number can also help boost the efficiency of a thermal storage system.
The disposal of organic waste is one of the most important problems facing society at the present time, as letting it ferment in the open produces unpleasant odors and causes many diseases. It also contributes significantly to increasing the phenomenon of global warming as it helps to produce toxic gases that affect the environment and cause global warming Including methane gas resulting from the process of decomposition of waste. Therefore, the process of anaerobic decomposition is the best solution for disposing of waste in a safe way and at the same time biogas is produced that can be used for the purpose of cooking and heating, as this process produces good quality fertilizer that is used for the purpose of fertilizing the soil. This research is subjected to studying the effect of different pH on biogas production and studying the concentrations of methane and carbon dioxide during the fermentation period, which reached 55days. The results are presented in clear curves to facilitate the study. The substrate used is corn with the addition of suitable primers to speed up the fermentation process. The results showed that the highest production of biogas and methane gas was at the digester whose pH was 7, followed by the digester that had pH 6.5, 5.5 and 4.5, respectively.
The household batch reactor using cow manure as the substrate generates methane gas used as fuel. This paper presents two-dimensional (3D) axisymmetric using commercial COMSOL 5.5 Multiphysics software. This is a computational fluid dynamics (CFD) model based on conservation equations with the chemical reaction model of anaerobic digestion (AD) processes to investigate the influence of different horizontal circular extended surfaces augmented to the inside digesters on the performance of the anaerobic digestion. Using four batch digesters, D1 with no extended surfaces and D2, D3, and D4 have augmented with four horizontal circular extended surfaces of width 2,4 and 6 cm, respectively. The numerical results showed that the cow manure's velocity distribution depends on the chemical reaction's heat, which produces natural convection currents. Furthermore, the temperature and species profiles of the anaerobic digestion process depended on the extended surface area. The D4 has a maximum methane molar concentration, augmented with a higher extended surface area than other digesters. Simulation results agreed with the experimental literature results of various anaerobic digestion processes: for all cases, the mean absolute present error (MAPE) was less than 10%, which is acceptable.
Anaerobic co-digestion of food wastes process is represents an active technique to enhance the production of biogas as one of the clean energy sources. The effects of adding lipids as substrate material to the food waste mixture for producing biogas by anaerobic co-digestion are experimentally investigated and evaluated at various mixing ratios in the present work. The influence of lipids and food waste (potatoes, tomato, Carrots, Cellulose) mixing ratios, digestion time and other factors on production of the biogas and CH4, CO2 and H2S percent are investigated experimentally. Seven samples of substrate mixtures (used edible oil, waste food, cow dung and water) with various mixing ratios were tested during 32 days as digestion period to investigate the influence of lipids percent compared to food waste on biogas yield. The results show that, average biogas production was in range of 100-160 ml per day and the maximum percent of Ch4 and CO2 were 52% and 46% respectively for the produced biogas. Increasing the lipids percent in the substrates mixture could enhanced the biogas and CH4 production. The mixing sample containing 70% lipids and 30% food waste percent was produced significantly higher biogas and CH4 yields compared to the other mixing samples. Best digestion time of the food waste-lipid mixtures was observed in range of 12-16 days for the tested samples. The maximum cumulative biogas was 5120 ml which was produced by substrate mixture (70% lipid and 30% solid waste) during digestion time 32 days.
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