Biogas - is this the future cooking medium?Aarti NarangFor a villager woman the greatest concerns in her daily work are two major factors: (i) water and (ii) fuel for cooking. These are the items for which women would walk some 5-10 kilometers every day. Even so, the women depend mostly upon the wood that they pick up from the forest and the cow dung cakes they make out of cow dung and straw. The diminishing forests are aggravating the situation as well as the new rules where more and more restrictions are put on the use of forest products even by the local communities. Energy deficit form fossil fuel is creating a massive crisis globally, prompting a number of research institutions to search for alternatives with renewable energy base. In 1998 Tata has shown in a report of renewable energy source that biogas can contribute to eliminate to a very large extent the fuel shortage in the rural region of the under-developing countries. This system is particularly good in the rural regions because this gas is actually created out of the anaerobic digestion of organic waste. In India where biogas has been received as a great success in many villages, there are about three million (households/ communities) when the potential is estimated to be at twelve million. How does the biogas work?The biogas has been very popular from the 60s onward thought he first biogas system was introduced in the country some three decades ago. The biogas is produced through anaerobic digestion of organic waste in three stages. In the first stage a number of extra cellular microbe enzymes (like protease, cellulose, lipase, amylase, and so on). The bacteria then decompose the carbohydrates, proteins and lipids into simpler compounds. When the bacteria do so, they utilize oxygen and carbon by which anaerobic conditions are created for methanogenesis. In the last and third stage, the anaerobes decompose all the compounds with low molecular weight to at last produce methane. This is how the biogas or the 'gobar gas' as it is called in many places in India comes to be produced. This gas has a very high thermal efficiency (60 percent) when compared to the regular fuel (wood - 17 per cent and cow dung - 11 per cent) that man uses in rural areas. The downside of this process that the bacteria that promote the fermentation s a result of which the biogas is produced needs a certain ideal temperature in order to produce gas optimally, and that temperature is about 36 degrees centigrade. This is why where biogas plants have been constructed in places where certain parts of the year it is cold, they need a heater to regulate and maintain the heat at a constant level. Other important factors in the production of biogas are the period of time that the waste retained within the plant and the loading rate. It has been seen the plant will have its peak production in the first four to five weeks, thereby tapering off. It has also been observed that the retention period will reduce if the waste has a higher amount of nutrients. For example, human waste (excreta) does not need any more than 30 days of retentions since it is very high in nutrients. The pH factor is another very important player in the formation of the methane gas. If the acidity of the load is high then the gas produced becomes less. The production of gases can be regulated by adding human and animal urine to the plant. The biogas plantThe biogas plant that you see today in different parts of the world is based on a model developed in China. This has a fixed dome, where the volume of the inlet and outlet tanks can be measured in order to calculate the minimum and maximum pressure of the gas based upon the slurry (waste product) and gas within the system. This model is more than 30 percent less than the first system that had been launched. This model is also improved and easier to maintain because there are no movable parts in it. The problem with this design is that the slurry has to get accumulated inside, making periodic cleaning necessary; this is a dangerous procedure because there could be a good build up of toxic gases (CH4) which can endanger the lives of those who dare to clean it. In China, they measure the toxicity of the gas inside by pacing a small caged bird inside the system 2-3 days prior to the cleaning. If the bird dies, then it is obviously dangerous, if not the cleaning process is commenced. Constraints of the biogas plant Biogas is by and large one of the most economical way to cook or light a home in rural areas. It is like turning nothing into light and fuel fire. However, this is not possible in a number of circumstances because of the following constraints: 1. insufficient amount of waste to run it; unless there are at least four cows/ cattle the plant cannot be operated. 2. insufficient water and/or space required for the plant also make for very important constraints for setting up a biogas plant; if there is no sufficient community land and water the plant cannot remain functional; the correct ratio of cow dung and water would be 1:1 ideally but it could still work with a ration or 4:5; hence you would require higher input where water is less 3. Water scarcity or loading capacity would also be a very important and critical constraint 4. The biogas plant needs a certain of technology savvy handling which is not always possible in very marginalized communities 5. As with water, insufficient production of dung also may highly inhibit the production of the methane gas from the plant. 6. You may have faulty construction when the biogas plant is not constructed by skilled workers. 7. Subsidization of fossil fuel in rural areas actually act detrimentally towards the installation of biogas. 8. Since the gas is coming from waste products, women do not prefer to roast their rotis on the fire Biogas is still the best alternative to fuel we have got today . Inspite of all the above constraints, if the biogas is promoted in an organized manner, rural communities stand to gain a lot, since this is a method which can be sustainable in the long run at the least cost. It is extremely beneficial in terms that it can bring light (illumination) to the households as well as a safe and smoke-free cooking medium for the millions of rural women thereby freeing them of the burden of collecting and carrying loads and loads of wood every day for cooking. 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