تشكل القمامه في كثير من الاماكن مشكله كبيره و خصوصا مشكله التخلص من المواد العضويه واعاده تدويرها ونتج عن ذلك تراكم المواد العضويه بالشوارع او التخلص منها بالقائها فى اماكن خارج المدينه واحيانا في الماء وهذاما يؤدى الى تلوث التربه والماء و الهواء بالروائح الكريهة والميكروبات نتيجه تعفنها و ايضا تؤدى الى زياده مشكله الاحتباس الحرارى عند تحلل المواد العضويه بالماء اوبالشوارع لاهوائيا فأنها تنتج غاز الميثان وهو ضار بمعدل 28 مره اكثر من ثانى اكسيد الكربون لان نسبه امتصاصه للاشعه تحت الحمراء 15% وايضا توالد وتكاثر الحشرات والفئران وانتشار الامراض والاؤبئه وايضا نقلها للمقالب طريقه مكلفه للنقل و ينتج عنها الغازات المدفئه وان هذه المخلفات هى مصدر اساسى للسماد العضوى و ايضا نظرا لاهميه الكائنات الحيه الدقيقه فى التربه
Introduction to the Zabaleen Biogas Project
Arabic by Hanna Fathy, Solar CITIES director in the Zabaleen Garbage Recycling Community of Cairo Egypt (English translated and interpreted by T.H. Culhane, Solar CITIES co-founder)
Garbage and litter creates serious problems in many places; an especially big problem is the disposal of organic materials which unfortunately are usually not recycled. This results in the accumulation of organic waste on the streets and/or the dumping of these wastes in places outside the city, often in canals, streams, rivers, lakes and oceans. They are also frequently burned. All of this leads to serious contamination of soil, water and air. The lack of efficient recycling of organic wastes creates more than just unpleasant odors and the potential for disease; microbes in the rotting food actually increase the problem of global warming when the decomposition of organic material proceeds anaerobically (as happens in landfills or garbage bins). These microbes produce methane, a gas that, if not burned, is 28 times more powerful than carbon dioxide. It's rate of absorption of infrared wavelengths is 15% greater than that of CO2. In addition to the global environmental impact and the local environmental impact (particularly the breeding of insects and rats and the transmission of diseases), transfer to landfills is an expensive and inefficient way to deal with these wastes. Not only does trucking them to dumpsites and burying them require a considerable amount of fossil fuels, but the resources themselves are wasted -- resources that could be used to actually reduce the amount of fossil fuels we use. Under controlled conditions of anaerobic decomposition, the methane produced can actually be better used for heating or generating electricity and the wastes themselves are a major source of organic fertilizer and provide important micro-organisms to enrich the soil.
Premise of the Project
Our idea is to use anaerobic bacteria to solve urban waste problems at the household level. The bacteria, which are obtained by placing a small quantity of animal dung before it dries into an airtight container (to ensure a viable bacterial population) are used to digest household kitchen wastes on-site so that families no longer have any organic garbage to throw out. This ensures that the streets remain clean and there is nothing that must go to the landfill (everything else, once clean of organic material, can be easily recycled). Anaerobic bacteria that normally live in an animal's digestive system, called "methanogens", once cultured to a suitable concentration outside the animal, will break down and digest organic materials (like spoiled food) in an "artificial stomach" (a plastic container) just as they do within the stomach of the animal and they will produce easily captured and controlled methane (natural gas) and fertilizer and assist in the disposal of organic material in a safe environmental manner.
Food waste feedstock rather than animal manure
We use organic kitchen waste to feed the anaerobic bacteria not only because it solves the problem of urban organic waste (providing an even richer fertilizer than normal aerobic compost) but leads to two different end products -- a rich liquid fertilizer that is easy to bottle and use (or even sell!) and up to two hours of biogas for household cooking almost every day.
Because the organic materials in kitchen garbage contain an enormous amount of energy in the form of rich chemical bonds, the production of biogas from this feedstock, as Dr. Anand Karve has proven at the Appropriate Rural Technology Institute in Pune India, is up to 400 times more efficient than production from animal waste, wherein the food has already passed through the digestive tract of the animal and is thus a "spent fuel". The ARTI system, which we have replicated in Cairo is thus different from the old and traditional biogas method, which depends only on animal dung as a feedstock. We use animal dung only as a "starter kit" on the first day of construction to create our bacterial culture. Once we have assembled the system (which can take as little as two or three hours) we don't need animal dung again (in a community of biogas producers a new system can be started by using the liquid effluent from somebody else's system, just as people share yoghurt and sourdough bacterial cultures).
1 cylindrical barrel of 1000 liters, 1 cylindrical barrel of 750 liters, 2 meters of 3 inch diameter tube, 1 T 3-inch diameter, 1 tank adapter 3 inches, one 3 inch valve, teflon tape, PVC glue , two 3 inch female connectors, two 3 inch male connectors; one 1 inch tank adapter, 1 meter of 1 inch tube, 1 Elbow 1 inch, one 1/2 inch tank adaptor, one 1/2 inch elbow, one 1/2 valve, one 1/2 inch brass hose adapter, 25 meters of clear flexible 1/2 inch plastic tubing.
Project Description: "The Sacred Cow"
You are basically trying to create an artificial cow to be the home of your methanogenic bacteria. You need to give your sacred cow a mouth, a throat, an esophagus, and a stomach, as well as a ureter, intestines, a farting bowel and an anus. From the ureter you will get fertilizer; from the anus you will get biogas. Your blender or insinkerator garbage disposal unit will act as the cows teeth for grinding up food.
The cow's stomach:
Cut the top off of the 1000 liter barrel so that 750 liter barrel can fit inside it upside down with about 1/2 inch to spare. This tank becomes what we call our artificial "cow's stomach".
The cow's mouth, throat and esophagus:
At the bottom of the 1000 liter barrel drill a hole (you can burn one through with a hot section of 3" steel pipe if you don't have a drill) to fit the 3" tank adapter. On the inside connect the female connector and connect it with a piece of 3" pipe leading to the center of the tank. On the outside connect the T and connect to this the drainage valve and a length of vertical pipe that extends at least 25 centimeters above the top of the tank. The pipe inside the tank that extends to the center is the esophagus, the pipe outside the tank is the cows throat. For a better mouth you put a funnel on top of this "feeding tube".
The cow's ureter.
At the very top of the 1000 liter barrel, on the opposite side from where you drilled the hole for the feeding pipe drill (or melt with a piece of hot pipe) a hole for the 1" tank adapter. On the outside of this connect a short length (~ 10 cm) of 1" pipe, then an elbow and then about 20 cm of 1" pipe -- this is for the exit of excess fluid. You place a 20 liter bucket under this "ureter" to capture the fertilizer. You will always get as much fertilizer in liters as the feedstock you put in to the mouth (i.e. if you pour 10 liters of ground up food and water in the mouth you will get 10 liters of "cow pee" out at the same time).
The cow's intestines.
You want to have as much surface area for bacteria to grow on and form their biofilms as possible. Fill the bottom of the 1000 liter barrel with stones and gravel of various sizes up to about 5 cm. You can also throw in plastic chips. One way we improve performance is to place a stone in the bottom of a net or mesh bag, fill the bag with plastic balls or chips and sew a piece of styrofoam at the top so the net bag floats vertically. The bag can be almost as long as your tank is deep and you can put several in. these become what we call "bacterial fuel rods" -- places where the bacteria can breed and form active biofilms. You are basically trying to recreate the villi in a cow's intestines.
The cow's bowels:
Take your 750-liter barrel, which will become your "gas collector" and cut openings in the top in the curved part, leaving enough of a skeleton of plastic to support the center ring of the original opening. Then press this ring in so that it is concave instead of convex. You want to leave this ring of plastic for two reasons -- one so that as the tank moves up and down as it fills with gas and you use the gas it will agitate and mix the water and food slurry to make sure the bacteria at the top get food too and two to provide weight and stability so that the tank rises in a more vertical fashion and has the mass to force the gas out as it descends.
The cow's anus:
Drill or melt a 1/2 inch hole into the bottom of the 750 liter tank (this will now be the top of the gas collector). It doesn't matter where you place this hole, but we generally put it about 5 cm from the edge of what will be the top so it can be closer to the kitchen and so we can place weights (bricks, potted plants, etc.) in the center of the collector to help pressurize the gas. Insert the 1/2" tank fitting and put on the elbow, the valve and the brass 1/2" pipe to barbed hose adaptor. Attach the clear plastic hose to the barb with a hose clamp and run the hose to the kitchen. Attach the other end of the hose to a stove burner.
After the barrels are equipped test them with water to make sure they don't leak. Tighten tank fittings as necessary.
Preparing the system to produce biogas:
Fill the 1000 liter tank with approximately 300 liters of water and then mix between 40 and 80 kg of fresh animal dung with water, breaking up any clumps under water and slowly pour it in. You don't want to expose the bacteria to air so try not to introduce a lot of bubbles as you are mixing. We've used dry animal dung in Palestine and it worked, but you are likely to get better and quicker gas production if the dung is still moist. You can get quicker results if you store the dung for several weeks in an airtight container before adding it to the digestor. You can also avoid the use of dung altogether if you have a source of liquid from somebody else's active biogas digestor. The more you add, the quicker you will get gas because this is all about building up a large healthy population of bacteria.
After you have added all the dung, continue to fill the barrel with water until you reach the overflow hole (the ureter). It is advisable to plug the ureter hole at first so that you can fill the barrel with water all the way to the rim so you can completely submerge the gas collector barrel and drive all the air out.Put the 750 liter barrel upside down into the 1000 liter barrel and open the 1/2" valve at the "anus". Press down on the 750 liter barrel to force the air out and to press it all the way down until it is completely submerged and is nested inside the 1000 liter barrel as far as it can go. If there is still a small airgap because your 750 liter barrel is slightly taller than the 1000 liter barrel (specifically because of the feeding tube or "esophagus" and the gravel, rocks or bricks on the bottom of the tank) this isn't a grave problem but it will slow down initial gas production because the aerobic bacteria need to consume all of the air first and die out before the anaerobes take over.
Wait until the anaerobic bacteria have reproduced and become active and start producing flammable gas before feeding. This can take around 2 to 3 weeks depending on the temperature; we've had systems in colder climates take several months. On the other hand we've had systems in warm environments start within a couple of days. When you use somebody elses active biogas effluent you can achieve flammable gas within 24 to 36 hours.
Regardless of how long it takes, try to avoid feeding the system anything until you are able to ignite the gas. The first days to weeks gas will be produced but it will be mostly CO2 and will extinguish a flame. Do a flame test every couple of days (or just wait if you have the patience). You will see the 750 liter barrel start to rise and when the CO2 concentration drops from 100% to about 40% you will have nearly 60% methane which will burn quite well and safely and will produce a clean clear blue flame.
At this point you can start feeding your system. Start slow -- you have to acclimatize the bacteria to high energy and complex food; actually their are many types of bacteria in your system that need to work together -- hydrolytic bacteria need to break down the food, acidogenic bacteria turn the breakdown products into different acids (propionic acid for example) and carbon dioxide, and acetogenic bacteria break these down into acetate and carbon dioxide which are the real foods for the methanogenic bacteria that make the biogas. To acclimatize them without overwhelming them start out with about 200 grams of food, then work your way up each couple of days by doubling to 400, then 800 then finally between 1 and 2 kg per day. For a 1000 liter system you don't want to exceed 2 kg each day because the water can turn acidic and the low pH will kill your bacteria (if this does happen, either wait for the pH to rise back to between 6.5 and 7.5 or add some baking soda or another buffer -- if some of your bacteria survive the acid event you will just have to wait until their numbers are strong again, if not, re-innoculate with fresh bacteria from either dung or somebody else's effluent. It is a good idea to store some of your own effluent in an airtight jerrycan just in case, and it never hurts to dump dung in from time to time if you have access to it). Do NOT overfeed your system - giving it more food will not give you more gas. A 1000 liter system (1 cubic meter) can give up to 2 hours of cooking gas on 1 burner per day when the temperature is at its optimum of 37 C. In the winter near Mumbai in India they get about 1 hour a day, 2 hours in the Summer. It is best to situate your tank where it gets the most sun each day; black tanks are best; if you only have white tanks, paint them black. In colder climates you will need to put a heat exchanger in the tank and connect it to a solar heater or a compost heater or even use 20 to 40% of your gas to raise the temperature to between 30 and 40 C.
Using your home-made biogas in a kitchen stove:
It should be noted that in order to use butane gas stoves and make them run on biogas you need to make a simple amendments: he first is to expand the gas exit hole (nozzle). This usually simply involves removing the restrictor pin where the gas from bottled gas enters the stove. Because biogas is generally under very low pressure and because it contains about 1/3 carbon dioxide you need to supply gas through a larger opening to get the same amount of thermal energy. The second amendment you might need to make is to minimize the air intake because the biogas won't need to consume as much air as high flow pressurized gas. By adjusting the air you should be able to achieve a clear blue flame with no yellow streaks in it.
Benefits of home biogas:
The home biogas system eliminates your kitchen waste and produces gas and a very rich liquid fertilizer that can be directly applied to plants or your garden. If you let the effluent dry you can use the cakes that remain as a solid fertlizer.
Benefits do not stop at this point --- another application that we have been experimenting with in Egypt is the production of electric power using a modified generator. The modification uses a $190 'tri-fuel' kit from US Carburetion and takes only about 15 minutes to convert. Per cubic meter biogas can generate electricity ranging from 1.3 to 1.5 kilowatts/hr.
Beyond the benefits of using biogas as a waste disposal,solution which is in itself a significant feature, the other benefits of biogas qualify it as a fantastic alternative energy source that can be used without purification or treatments and causes no air pollution -- it can thus replace bottled gas, wood and charcoal and not only reduce respiratory illnesses and the use of fossil fuels, but take pressure off of our dwindling forest resources, saving and protecting habitat for wildlife and protecting watersheds.
Biogas is relatively non-toxic, is colorless and has no odor when it is burned. When it is not burned it has the odor of natural gas (a slight tinge of hydrogen sulfide) so one can easily detect a possible leak and take appropriate action. It has a flame speed of 35 cm per second, slower than natural gas - which actually makes it safe. It has a thermal energy content between 5000 to 6000 kcal per cubic meter. Chinese experiments have proven the following practical applications that 1 Cubic meter of biogas (the normal output per day of a household system using a 1000 liter barrel) can provide:
Run the stove for an average of 2.5 to 3 hours.
Run a lamp of 100 candle power for a period of 8 to 10 hours.
Run an internal combustion engine/generaotor of 1 HP for two hours.
Operate a tractor weighing 3 tons a distance of 2.8 km.
Run a medium-sized runs with a length of 60 cm for two hours.