A. Mirzaee; M. Soleymani; H. Bahrami; M. Norouzi Masir
Abstract
Introduction: Almost 18 percent of emitted greenhouse gasses in Iran come from livestock industries, especially from manure decomposition. With the anaerobic digestion of animal wastes, in addition to eliminating its disadvantages, biogas as a clean and renewable energy carrier is produced. In addition, ...
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Introduction: Almost 18 percent of emitted greenhouse gasses in Iran come from livestock industries, especially from manure decomposition. With the anaerobic digestion of animal wastes, in addition to eliminating its disadvantages, biogas as a clean and renewable energy carrier is produced. In addition, the resulting sludge is a more healthy and nutritious fertilizer for use in agriculture. One of the challenges of the bio-gas industry is to increase gas production efficiency. Various approaches are proposed to enhance manure digestion efficiency and increase biogas production, which can be mentioned below: Changing operating parameters such as temperature, hydraulic retention time (HRT), and particle size of the substrate; adding some effective additives; returning the resulting sludge into the digestion process and using bio-filters. Therefore in this study, in order to increase biogas production from poultry manure, two methods (co-digestion with rumen contents, and chicken intestine and its contents, and returning the slurry into the reactor) were tested. The alkaline composition of chicken manure and its high content of ammonia makes it difficult to digest alone, and co-digestion with high-carbon organic matter improves its digestibility.Materials and Methods: Polyethylene bottles were used as batch reactor units. In order to the possibility of gas exit, as well as taking samples of the digester, two valves were placed on the bottle cap. All digesters were placed in a hot water bath and a 700 watts electric heater and a thermostat were used respectively to supply heat and to keep the temperature constant. A U-shaped tube, connected to the reactor output pipe was used to measure the amount of produced gas. The volume of water removed from the tube was an indicator of produced gas. The experiment was carried out in two stages. In the first stage 21 reactors were used according to the design of the experiment which was a completely randomized design with 7 treatments (adding rumen fluid in three levels (10, 20, and 30 percent of chicken manure (weight basis), respectively), adding chicken intestines and its content in three levels (10, 20, and 30 percent of chicken manure (weight basis), respectively), and control treatment), and three replicates of each treatment. During the whole experiment period, the pH and temperature were kept constant, respectively between 7.2-8.2 and 40-35 °C (mesophilic range). In the second stage of the experiment, after all the treatments reached the end of their hydraulic retention time, the resulting sludge was filtered and the liquid part was returned to the cycle. Three treatments were also provided here (supplying 50% of the water required by sludge liquid, supplying 100% of the water required by sludge liquid, and control treatment (no liquefied sludge).Results and Discussion: Based on the results, although the type of organic supplementation had a significant effect on the amount of biogas production, the quantity of them had not. Treatments of chicken manure + 20%, 30%, and 10% of chicken intestines resulted in the highest amount of biogas production, respectively. But these three treatments were not significantly different. Also, the co-digestion of chicken manure with chicken intestines was more effective than the co-digestion of chicken manure with rumen fluid. The return of sludge, resulted from anaerobic digestion of chicken manure, again into the cycle, in addition to enhancing the amount of produced gas, can reduce the waiting time to start gas production by at least six days (in the treatment of providing 100% of required water from returned sludge). This can lead to continuous gas production and availability of sufficient gas in commercial gas-producing units. The effect of treatments on the time of reaching the cumulative gas production index to 100 mm was significant (α= 5%) and treatment of S100 reduced this duration by approximately 17 days (65%) and S50, for approximately 16 days (74%). Conclusion: According to the results of this study, co-digestion of chicken manure with cow rumen fluid did not have a significant effect on the increase of biogas production, but co-digestion of chicken manure with chicken intestine and its contents (at least by 20% of chicken manure (weight basis)) can have a significant effect on the increase in the production of biogas and can increase the amount of gas at least twice. The highest amount of gas volume was about 305 Ml.gr-1 VSadded and came from the treatment of co-digestion of chicken manure with 20% (weight base) chicken intestine and its contents. The return of the resulting sludge of anaerobic digestion of chicken manure, back into the cycle, in addition to increasing the amount of gas, can minimize the time it takes to start to produce gas and help to produce gas continuously. Moreover, the water used for digestion will also be significantly reduced (at least 50%).
Modeling
S. Mirzamohammadi; A. Jabarzadeh; M. Salehi Shahrabi
Abstract
IntroductionThe increasing global population on the one hand and limited water and soil resources on the other hand, contribute to the need for the supply of agricultural products by adopting modern methods. One of the modern methods of farming is the cultivation of products in commercial greenhouses. ...
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IntroductionThe increasing global population on the one hand and limited water and soil resources on the other hand, contribute to the need for the supply of agricultural products by adopting modern methods. One of the modern methods of farming is the cultivation of products in commercial greenhouses. Despite favorable performance of greenhouses in the agricultural sector, high demand for direct and indirect energy is among the main considerations of developing them because the energy supply of greenhouses has the highest influence on the performance of greenhouses, quality of products, and market price of products. In this study, the energy supply of greenhouses in the case of using renewable resources is done in a grid connection state. Trading energy with main grid is enabled. Decision-makers’ objective is determining the optimal number of renewable resources and energy storage units for the purpose of income maximization.Materials and MethodsBasically, the supply of energy for greenhouses or in other terms supply of electric, cooling, and heating loads required by greenhouses is intended to cover lighting, internal temperature, emission of CO2, and relative humidity. Since many greenhouses have proper access to the main grid for the supply of their demanded load, the problem seeks maximum use of renewable energy rather than buying power from the grid for supplying the loads which greenhouses need to its secure revenues. To this, mathematical modeling has used to determine the optimal number of energy sources and storage units that revenues of using renewable energy resources be optimized based on existing limitations. These limitations include balancing generation and consumption of thermal and electrical power in each hour, logical relationship between charging and discharging of batteries, limit of power generation of renewable sources in each hour of the day and the level of capital available for investment.Results and DiscussionBased on the collected data, 9 different issues have been defined in terms of the proportion of costs of solar energy and wind energy and the proportion of purchasing and selling price of power. The obtained results suggest that in the case of equality of investment and maintenance costs of solar and wind energies, the use of wind energy rather than solar energy will be justified. The most significant reasons for this is considering proper conditions of wind speed which causes its inclusion in optimal solution of the problem since using solar energy during nightly hours is impossible. In addition, in the case of the equality of above costs, when purchasing and selling price of power cost is the same, the generated energy is completely used in the greenhouse. In the case of increasing the selling price, energy supply to the main grid will be economically justified. Since investment and maintenance costs of wind power are two times and 1.5 times higher than those of solar energy, using wind energy is cost-effective.ConclusionThe results suggest that in the case of an equal price of selling power to the grid and buying power from it, all of the energy will be consumed in the greenhouse. In the case of an increase in selling price, the supply of energy to the main grid will be economically justified. In addition, the results imply the significant effect of geographic conditions of the region, since sometimes concurrent use of renewable energies is unjustified. Since the lack of supply of energy to greenhouses significantly influences the cultivation of products, considering the cost of lack of energy supply in modeling is one of the contributions of the present study. Another significant aspect of the study is the generalization of modeling from the greenhouse to greenhouse complexes. To do so, using the notion of micro-hub for greenhouses and their management will be useful.
M. Shabanzadeh; R. Esfanjari Kenari; A. Rezaei
Abstract
Introduction
While the world's population is growing, agricultural production is still based on the use of limited and non-renewable resources. In addition to the scarcity of resources, their continuous using over the long term, causes the widespread pollution, loss of soil fertility and low agricultural ...
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Introduction
While the world's population is growing, agricultural production is still based on the use of limited and non-renewable resources. In addition to the scarcity of resources, their continuous using over the long term, causes the widespread pollution, loss of soil fertility and low agricultural production capacity, eventually. The main causes of the increase in energy consumption include the increase of world population, limited arable land, low price of fuel and fertilizer and noted increased levels of human life. Attention to limited resources and adverse effects resulting from the appropriate use of different energy sources on human health and the environment, has been required examining the energy consumption patterns and the flows of energy in the agricultural sector. Checking the share of input and output energy in different agricultural ecosystems, with attention to the type of product and the type of materials used in production, can help to identifying defects and play a fundamental role in the sustainable production, optimization of economic system, maintaining reserves of fossil fuels and mitigate air pollution. With this approach, in this present study energy consumption and energy indices for tomato production in Khorasan Razavi were studied.
Materials and Methods
The energy efficiency of units was analyzed using the stochastic frontier technique (SFA). Energy inputs from two perspectives have also been divided. In the first view of energy inputs, including inputs that have a direct energy (DE) and indirect energy (IDE). The second approach as well includes inputs that have renewable energy (RE) and non renewable energy (NRE).The data for this study was collected through interviews and completing 156 questionnaires using two-stage random sampling from tomato producer of Khorasan Razavi province in 2012.
Results and Discussion
The results showed that the energy consumption for tomato production in Khorasan razavi province of Iran were 43.2 GJha-1. Water for Irrigation was attributed the greatest share of energy inputs (30%). The average amount of diesel fuel consumption was 152 lha-1, Human resources and machinery were 987 hha-1 and 44.6 hha-1 respectively. The average amount of water needed for irrigation was 12,596 m3ha-1. Average energy output of the system was determined to be 35.3 GJha-1. The share of different forms of energy inputs such as direct energy was 53.9 %, indirect energy was46.1renewable energy was 50.5, and renewable energy was49.5%. According to the results, the share of indirect energy was higher than direct energy and the share of renewable energy was higher than renewable energy. Also the result of the study revealed that energy productivity and efficiency in the investigated units were 0.68 and 0.82MJha-1, respectively. The results show that the Cobb-Douglas function to calculate the efficiency has more consistency and adaptation with the data. In other words, Cobb-Douglas function is superior to the translog function. Average of technical efficiency was calculated 57%.
Conclusions
The results indicated that although a significant percentage of the investigated farms are inefficient, farmers with higher acreage have favorable energy consumption and technical efficiency of these farms was higher than that the other ones. Considering the obtained results, the main drawback associated with the technical efficiency of energy use and production of tomato in Khorasan Razavi is inappropriate use of inputs due to mismanagement, lack of information and also the small size of the farms. Based on the results the better management in the use of inputs and the enlargement of the size of agricultural land can improve energy efficiency in the region. Also, for improving the measures of energy flows in growing tomatoes, determining the appropriate amount of fertilizer (particularly phosphates) to grow tomatoes, conducting classes and printing the brochures for farmers to implement correct procedures in the use of inputs and the use of machines, correction of the system to reduce water consumption and cultivation of new varieties of tomato seeds in the region are recommended.
M. A. Ebrahimi-Nik; A. Heidari; H. Younesi
Abstract
Fast pyrolysis is an attractive technology for biomass conversion, from which bio-oil is the preferred product with a great potential for use in industry and transport. Corn wastes (cob and stover) and eucalyptus wood are widely being produced throughout the world. In this study, fast pyrolysis of these ...
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Fast pyrolysis is an attractive technology for biomass conversion, from which bio-oil is the preferred product with a great potential for use in industry and transport. Corn wastes (cob and stover) and eucalyptus wood are widely being produced throughout the world. In this study, fast pyrolysis of these two materials were examined under the temperature of 500 °C; career gas flow rate of 660 l h-1; particle size of 1-2 mm; 80 and 110 g h-1 of feed rate. The experiments were carried out in a continuous fluidized bed reactor. Pyrolysis vapor was condensed in 3 cooling traps (15, 0 and -40 °C) plus an electrostatic one. Eucalyptus wood was pyrolyised to 12.4, 61.4, and 26.2 percent of bio-char, bio-oil and gas, respectively while these figures were as 20.15, 49.9, and 29.95 for corn wastes. In all experiments, the bio-oil obtained from electrostatic trap was a dark brown and highly viscose liquid.
