Human Excreta as Bio Gas-Working of a Bio Gas Plant

Human Excreta as Bio Gas-Working of a Bio Gas Plant

Introduction



Before the 21st century the usage of coal and petroleum were given the main priority. The exploitation of fossil fuels made the industrial revolution possible. Increasing industrialisation led to an increasing demand for fossil fuels, which was largely met by the use of coal and petroleum. They were economical, viable and easily accessible. Even our technologies were also developed to use them. But they take millions of years to be formed and their reserves are also limited. Thus, these are non-renewable sources and they will be exhausted within 50 or 60 yrs. Moreover, there are several other disadvantages in using them also like burning fossil fuels in air causes air pollution and aggravate the problem of global warming and greenhouse effect. The oxides of carbon, nitrogen and sulphur which are released on burning them are acidic oxides, which further lead to acid rains causing water pollution and damage to the life of several organisms. Since, they will be soon exhausted we need to look for other viable, economical and moreover eco-friendly sources of energy.



In this situation bio gas can prove to be an alternative source. Organic materials like cow dung, various plant materials, vegetable waste and sewage, etc. when decomposed in the absence of air produces a gas called bio gas. Since the starting material is mainly cow dung, it is popularly known as ‘gobar gas’. It is a mixture of gases produced by anaerobic degradation of biomass in the presence of water but in the absence of oxygen.



Working of a Bio Gas Plant



In a bio gas plant a dome like structure is built with bricks. The slurry of organic waste and water is made in the mixing tank from where it is fed into the digester. The digester is a sealed chamber in which there is no oxygen. Anaerobic micro-organisms that do not require oxygen decompose or break down complex compounds of the cow dung slurry. It takes a few days for the decomposition process to be complete and produce gases like methane, carbon dioxide, hydrogen and hydrogen sulphide. The bio gas is stored in the gas tank above the digester from which they are drawn through pipes for use. This gas is used for electricity generation and other domestic purposes like cooking.



Advantages of Bio Gas



It is an excellent fuel as it contains 75% methane, that has a higher calorific value (55kj/g) than that of petro (50kj/g) and thus, has a high heating capacity, it burns without smoke ands leaves no residue like ash in wood, charcoal and coal burning, the slurry left behind can be used as excellent manure as it is rich in nitrogen and phosphorous, also the large scale utilisation of bio waste and sewage provides a safe method of waste disposal, by using bio gas, firewood is saved and deforestation is reduced.



Thus, bio gas is an eco-friendly, viable and economical source of energy.



But unfortunately, despite of its so many advantages, the use of bio gas is limited to rural areas only and also it is not used at a very large scale.



Human Excreta as Bio Gas



Why do we always consider bio gas as gobar gas which is produced from cow dung? Can’t bio gas be produced from human excreta?



Actually, if such plants are set up in rural as well as in urban areas, where the human excreta in the sewage can be utilised to produce bio gas, our many of the serious global problems can be solved as if these plants utilise the sewage-



1. Our rivers will be protected from being contaminated with sewage,



2. The waste that would pollute the rivers and seas could be used as a resource,



3. The slurry can be used in farms as manure,



4. This gas can be used for the generation of electricity and it will also help to replace the use of LPG for cooking purposes, which will soon be exhausted,



5. Since, the calorific value of bio gas is greater than petroleum; it can also be used as a car fuel to run vehicles, when compressed,



6. Moreover, the organic waste present in the landfills in the cities can also be used for the purpose, which will reduce the emission of greenhouse gases and cities cleaner,



7. We will also get an alternative fuel which can replace coal, petroleum, CNG and LPG to fight the global crises of fuels,



8. This usage of bio gas will reduce deforestation as the requirement of firewood will be fulfilled by bio gas.



Such plants can be set up combining a few localities depending upon the population of the area in every cities, towns and villages. With this we will be able to eliminate pollution to some extent, make our cities clean, healthy and hygienic, reduce the number of landfills, develop a new resource which is economical, easily accessible, eco-friendly and non-exhaustible.



For this purpose, the world governments should raise funds and encourage the usage of bio gas, as the problems stated above are the problems of every country and every person.