Technical and field performance evaluation of flexi biogas plants Project Completion Report (July, 2013- March, 2014) Submitted to International Fund for Agricultural Development By Prof. Virendra Kumar Vijay Project Investigator Biogas Development and Training Centre Centre for Rural Development and Technology Indian Institute of Technology Delhi Hauz Khas, New Delhi 110016 (India) Phone: +91-11-26596351, 26591157 Fax: +91-11-26591121, 26596351 E-mail: vkvijay@rdat.iitd.ac.in
1. INTRODUCTION: Wastes generated in human habitats, agricultural activities and animal farming impact negatively on human well-being and the environment if not treated and managed appropriately. Lack of safe and hygienic disposal of human, cattle and poultry wastes affects community sanitation and health. As chores related to animal husbandry are generally done by women, they bear the brunt of the above. Biogas can play a vital role in reducing drudgery of women in the kitchen. Biogas is a mixture of gases which is produced by digestion of organic fraction of wastes under an anaerobic environment. In rural areas animal waste based biogas plants would be useful. Much of women s time is devoted towards collection of firewood for direct burning. Promoting biogas as a locally available appropriate means of energy supply can lead to better living conditions. The most common type of biogas system, and the most widely adopted in India, is a floating drum type biogas system and fixed dome type deenbandhu biogas system. Another type of biogas system, developed by an entrepreneur from Kenya, is Flexi Biogas, a flexible above-ground system which is simpler and low cost. This system is simply a 6m x 3m plastic bagmade of PVC tarpaulin. The Flexi Biogas system is portable and expandable. In design it is similar to an open-ended pillow case, it consists of a plastic digester bag housed in a greenhouse tunnel. The tunnel acts like an insulated jacket, trapping heat and keeping the temperature between 25 and 36 degrees Celsius so as anaerobic digestion can be facilitated by mesophilic microbes. The project was undertaken to evaluate the performance of flexi biogas system in field and give feedback on its technical and social aspects.
2. OBJECTIVES OF PROJECT: For this project Indian Institute of Technology, Delhi was facilitator in this project for sourcing of equipment materials, installation management and technical evaluation. The Environment and Climate Division (ECD) at IFAD has signed institutional contract for this project. More specifically objective for IIT were: 1. To conduct preliminary assessment activities and collect baseline data on target beneficiaries from the IFAD financed project in Odisha State, India to generate baseline information. 2. To evaluate performance of flexi biogas plant and suggest the refinement of the model, if any. 3. To refine the model by building capacity of smallholder farmers and local communities to enhance the implementation and diffusion of Flexi Biogas systems. 3. OUTPUT OF PROJECT 3.1 Nature of Output: The project was related to field scale demonstration of flexi biogas plant. Three Flexi biogas plant have been installed at two locations in India. Two at a tribal village in Raigada District of Odisha State running on cow dung and one at Faculty House at IIT Delhi campus running on kitchen waste. As there were issues with procurement of sufficient kitchen waste, it was decided to supplement that it was supplemented by non-edible deoiled cake of Jatropha plant seeds. The later one which is installed at IIT Delhi campus served the purpose of continuous monitoring for performing research and development studies, while the other two which were installed in a village served the purpose to meet cooking energy demands of the tribal families. Earlier women of families spend much of their time in collecting fire wood in the absence of easily accessible and affordable fuel. Countless working days of these women were lost in such activities resulting in stagnation of their progress and productivity. Biogas plant provided tribal families
a locally available appropriate means of energy generation which helped to promote better living condition's apart from providing organic manure and most importantly helped in mitigating drudgery of these women while reducing pressure on forests and preventing climatic change. The advantage of this type of plant is a greenhouse canopy to maintain temperature which is advantageous for winter season when temperature dips below 10 degree Celsius in Northern and eastern part of India. 3.2 Performance Specifications: Performance assessment of the installed biogas plants were done on daily basis for few parameters while at regular intervals for determining several other parameters. A brief description of parametric studies performed is discussed below. A. ph in the digester: Anaerobic digestion of biodegradable materials for biogas production is performed by set of different microbes. Microbes responsible for initial breakdown of larger molecules into smaller one through hydrolysis are known as hydrolytic microbes. These smaller molecules are further converted to volatile fatty-acids by the action of acetogens and acidogens, later methanogenic microbes convert these fatty-acids to methane and carbon dioxide. To facilitate uninterrupted biogas production, the ph growth media of these consortia of microbes (in this case growth medium for these bacteria is waste) should lie between 7.2-7.8 (~0.2) ideally. Any deviation from this range can prove fatal for microbial growth, which may stop the biogas production process. In the digesters the ph was kept in the range of 6.5-7.5 B. C/N Ratio: The relationship between the amount of carbon and nitrogen present in organic materials is represented by the C/N ratio. Microorganisms need nitrogen for the production of new cell mass. Optimum C/N ratios in anaerobic digesters should be between 20 30 in order to ensure sufficient nitrogen supply for cell production and the degradation of the carbon present in the wastes.
A high C/N ratio with in the digester is an indication of rapid consumption of nitrogen by methanogens and results in lesser biogas production. On the other hand, a lower C/N ratio causes ammonia accumulation and ph values exceeding 8.5, which is toxic to methanogenic bacteria. Optimum C/N ratios of the digester materials can be achieved by regular biogas digester monitoring and co-digestion with other substrates. C/N ratio of the feed material was maintained around 25-30 in both the cases. C. Temperature inside the reactor and inside greenhouse tunnel: As temperature plays an important role in any biological process, anaerobic digestion of feed stock is best done under mesophilic temperature range of 35-37 degree Celsius. During regular monitoring it was found that average temperature inside the green house tunnel was 37-38 degree Celsius while that inside the digester it was between 30-33 degree Celsius. Month Average Temperature in Raigada ( o C) Average Temperature in Delhi ( o C) July, 2013 32.2 34.7 August, 2013 31.6 33.6 September, 2013 32.1 34.2 October, 2013 32.2 33.0 November, 2013 30.4 28.3 December, 2013 28.4 22.9 January, 2014 28.7 21.0 February, 2014 31.4 23.5 March, 2014 34.9 29.2 Table.1 Average table recorded in Raigada, Odisha and New Delhi, Delhi D. Feeding of total solid and biogas production: Field biogas plants: In field biogas plant was fed daily with cow dung 15-20 Kg with equal amount of water daily. The average biogas production was noted to be 0.4-0.5 cum/day with 55% methane content. This much gas has a calorific value of ~15 MJ which is equivalent to 0.25 Kg of liquefied petroleum gas or burning 5 Kg of wood in tradition cook-stove.
Biogas plant at IIT Delhi: In this case both Kitchen waste and jatropha deoiled seed cake was fed in the biogas plant. The plant was fed daily with around 2.5-3 Kg of kitchen waste along with ~0.5 Kg of jatropha deoiled seed cake with 5 liter of water. The average biogas production was noted to be 0.2-0.25 cum/day with 58% methane content. This much gas has a calorific value of ~8 MJ which is equivalent to 0.1 Kg of liquefied petroleum gas or burning 3 Kg of wood in traditional cook-stove. 4. IMPACT OF THE PROPOSED OUTPUT 4.1 Carbon Dioxide equivalent reduced/ plant installed A single biogas plant installed at in field and producing biogas which is being used for cooking needs can save 8.081 ton CO2e/year. (See Annex) 4.2 Impact on beneficiary Rural women work as long as 16 hours from dawn till late night. On an average for preparing three meals a day women spend up to 5 hours in cooking. The long hours of work and static muscular efforts result in fatigue and drudgery. They were confronted with a high workload as they have to carry out almost all domestic activities like cooking, washing pots and dishes, fetching water and fuel and fodder collection. In recent years workload of women has been increased due to deforestation, since they have to travel more distance each day to collect firewood for cooking. On an average they used to spend more than 4-5 hours and carry head load of approximately 10 Kg of wood every day. Over the period of time biogas plants installed in tribal village of Odisha will be proved as an important tool for empowerment of women and development of the community. Biogas plants will improve livelihood of these women by; 1. Providing improved health security to women by reducing indoor air pollution caused due to burning of firewood or dung cake during cooking as biogas is a clean cooking alternative,
2. In providing them education and helping them for setting up community small scale industries which run on surplus gas. This will contribute towards better household economy and improve their status within the family. 3. Usage of biogas for cooking saves the time of women and girls spend on collecting firewood and making dung cakes. Girls can continue with their education and women can take part in other family and community development works, which improves the social status of women in the family and community. 5. CONCLUSION Women can play an effective role in earning their livelihood through Biogas by forming self-help groups which can install and maintain biogas plants. Also by learning some technical skills they can start a cottage industry. Therefore, flexi biogas plant is an appropriate biogas model which offers this kind of provision. This would provide income to them through employment. Earlier women of tribal families spend much of their time in collecting fire wood in the absence of easily accessible and affordable fuel. Biogas plant provided tribal families a locally available appropriate means of energy generation which helped to promote better living condition's apart from providing organic manure and most importantly helped in mitigating drudgery of these women while reducing pressure on forests. In the tribal villages people those having cattle s are interested to have the flexi biogas plant in order to save time & forest. The plant contributes to enhancement of vegetable & crops production and additional income. Also the investment to set up such plant is about INR 5,000/- (US$ 85). The villagers are taking keen interest regarding benefits of biogas plant along with utilization of biogas and bio-fertilizer. Among the most significant challenges faced during this project was that only a trained person can install such type of plants. The beneficiaries should also be trained if it gets puncture and its repair and maintenance. It has been found that there is lack of awareness about the maintenance of plants, since the biogas plants have been provided to the families free of cost, they pay little attention. Operation of biogas plant
to gain benefits need certain labour on day to day basis and time, which families are reluctantly serving. During the project an understanding was developed that Biogas should be an important part of self-reliant energy supply system in rural areas. Usually, majority of household in villages have animals and their manure can be used for biogas production however government should provide 50-60 % support to install biogas plants and fuel and fertilizer. The flexi biogas system can be recommended to small and poor families as it is easy and quick to install with temperature controlled condition. 6. PHOTOGRAPHS Tribal Village in Odissa, India Cow shed in beneficiary house Awareness program being conduced among the villagers
Flexi Biogas plants installed at two of the beneficiries in Village in Odissa Women cooking food on stove running with Biogas & Blue flames of Biogas Slurry from the biogas plant is being used as manure
Flexi Biogas plant installed at IIT Delhi Beneficiary feeding biogas plant with kitchen waste at IIT Delhi
Annexure 1. Calculation of Carbon dioxide equivalent reduction: A. CO2 emission from wood burning. Specific carbon dioxide emission of wood = 0.39 Kg CO2/kWh (while 1 kwh=3.6 MJ) Considering calorific value of wood= 18.00 MJ/Kg Amount of wood burned in each house/day for cooking = 5 Kg i.e., 18 x 5 = 90 MJ equivalent Since efficienct of whole system is 10-12%, specific CO2 emissions by burning 5 Kg of wood would be = 9.75 Kg/day B. CO2 emissions from cow dung Before setting up biogas plants cow dung was simple dumped in the near by vicinity adding up CO2 and CH4 due to its degradation 40 Kg dung dumped will produce 1.5 cum of biogas every day (consiting 55% of methane and 45% carbon dioxide) B1. CH4 emission = 825 L/day Density of CH4= 0.656 g/l @ 25 o C at 1 atm. Mass of CH4 emitted/day = 541.2 gm x 21 (CH4 has CO2e of 21) = 11.36 KG CO2 B2. CO2 emission= 0.525 cum/day Density of CO2= 1.977 Kg/cum Mass of CO2 emitted/day= 1.03 Kg CO2 Total CO2/day = A + B (1+2) = 22.14 Kg/day or 8.081 Metric ton/year
2. Installation maual of Flexi-Biogas plants This document explains step by step the construction, installation, operation and maintenance of a Low-Cost flexi-biogas plant. This manual is based on the practice and experience of the GTZ/EnDev project in Bolivia. The manual is edited by Marc Luer (email: marc.luer@t-online.de) and published in February 2010. A. Introduction to Technology: The digester uses a low cost polyethylene tube which is bended at each end around a 6 inch PVC drainpipe and can be wounded with rubber strap of recycled tire-tubes. One of the 6" PVC drain-pipes serves as inlet and the other one as the outlet of the slurry. In the tube digester finally, a hydraulic level is set up by itself, so that as much quantity of added prime matter (the mix of dung and water) as quantity of fertilizer leave by the outlet. Schematic of biogas production system and pipeline
B. Necessary materials and tools The materials for the construction of a Low-Cost Polyethylene Tube Digester are listed in the following tables: 1. Tubular Polyethylene - 300 microns [µm] Black smoke (UV-filter) Width of roll: 1,75 m (Planes) & 1,50 m (Valley & Tropics) 2. Greenhouse Tubular Polyethylene - 250 microns [µm] transparent Width of roll: 2.0 meter 3. PVC drainpipe 6 diameter Number: 2 units of 1 m each 4. PVC tube bend ½ Number: 4 units 5. PVC T-fitting ½ Number: 4 units 6. PVC lock valve ½ Number: 5 units 7. PVC universal coupler ½ Number: 2 units 8. PVC adapter flange ½ Number: 4 units (High Altitude) 3 units (Valley & Tropics) 9. Tubular Polyethylene - 200 microns [µm] - transparent width of roll: 1,0 m 3 biogas-reservoirs (2.5 m each one) (Altiplano) 2 biogas-reservoirs (2,5 m each one) (Valley & Tropics) 10. Number: 7,5 m (Altiplano) 5 m (Valley & Tropics) 11. PVC - tube ½ (irrigation tube) Number: 25 m 12. Teflon band Number: 2 units 13. Steel wool (SH4 filter) Number: 1 unit 14. Biogas - burner (Example - picture) Number: 1 unit 15. PVC plug for T- tube ½ Number: 1 unit
C. Selection of the location where the tube digester is installed The tube digester is installed in a central position between the kitchen and the place where the lives-tock sleep, in order that the collection of the fresh dung is most easily as possible and that the supply line is as short as possible. It is important that the digester is placed above flooding levels. The maximum distance between tube digester and kitchen should not exceed 25 m in order to minimize the pressure leakage. D. Dimensions and completion of the trench in tropical zones For the tropical-zones there is no need to install the adobe walls too. The trench has a length of 5, 0 m and the channels for the in- and outlet have an inclination of around 40 (Figure 8). The dimensions of the trench profile are seen in Figure below. General steps for the completion of the trench 1. Once the work is made, the trench is cleaned from stones and roots, to avoid that they damage the tube digester. 2. After that, the lateral walls are lined with old sacks of jute or old greenhouse plastics to protect the polyethylene of the tube digester. 3. The floor of the trench is covered with fine sand, straw or the mentioned old sacks. Sometimes dung of cows or sheep is used too, with the effect of an increase of temperature for the first days. 4. The trench shouldn t have an incline. The maximum allowed incline is 5 % over the whole length.
E. Construction of the tube digester Once the trench is excavated and completed, the construction of the tube digester can start. The necessary materials for the construction are the followings: a. Tubular polyethylene roll (300 microns) b. Rubber strap - produced from old automobile tire-tubes c. 6 drainpipes for the inlet and outlet of the slurry d. PVC adapter flange ½ for the biogas outlet e. 1.5 m of ½ PVC tube f. 1 unit of ½ PVC lock valve The required tools and auxiliary materials are: a. Saw b. Pipe tap ½ for outside thread c. Pipe tongs d. Teflon e. Shear f. Tarpaulin ( 4 m x 9 m ) It is important to realize the construction of the tube digester, over a ground free of stones and objects, which could damage the polyethylene of the digester. So it is recommended to extend a tarpaulin like a working surface. 1. The double 300 microns polyethylene coat The first is to cut two bags of the 300 microns polyethylene in the The first is to cut two bags of the 300 microns polyethylene in the needed size. At this point it is to mention, that the length of the plastic have 1, 0 m more than the final length of the tube digester. This is needed for the folding of the plastic at the slurry inlet and outlet pipes (0, 5 m each side). One polyethylene bag is to extend completely on the floor (over a tarpaulin), and the second one is to introduce carefully in the first bag. A person has to cross over the whole length inside the extended bag, without dropping the end of the inside bag. The idea is to have just one tube with a double coat. It is important to avoid inside wrinkles and to make the two coats coincident. 2. The Biogas outlet When the tube with the double polyethylene coat is ready, the biogas outlet with the PVC ½ adapter flange is made. A small cut through the double coat of plastic is made. It is fair to make the cut in the mid-dle of the tube digester, but about 0, 5 m closer to the slurry inlet side. This is made, because the trench could have a small incline, so that the gasholder is generating itself closer to the inlet and by this way the biogas can leave out better.
3. The slurry inlet and outlet pipes After finishing the biogas outlet, the two ends of the double coat polyethylene tube are closed, by strapping them with the 6 drainpipes of the slurry in- and outlet. Both cases are identical. 4. Introduction into the trench The constructed tube digester is put in the prepared trench, with the lined walls and the padded floor. The best is to pitch the digester and to transport it with some persons like a train to the trench. Every person has to care for that the plastic never scratch s anything. 5. Security valve The security valve is installed near by the tube digester. In this manner it is possible to review the water level during the daily charging. The valve allows that the biogas can escape, during insufficient consume. 6. The Biogas Stove a. To cook with biogas, it is to install a biogas stove. The stove should be installed in a place without wind like a closed ambience. b. When the flame of the biogas doesn t has the color of a clear blue, it is to control the hydrogen sulfide filter in the t-fitting of the security valve. c. To reduce the cost, in Bolivia the tube digesters are added just with one stove actually. But it is recommended to provide the system with two stoves. It possible to connect a second stove later.