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Using Biogas as a Motor Fuel

written by: Baby Rani•edited by: Lamar Stonecypher•updated: 10/22/2010

Biogas manufactured from organic material before being used as a fuel for motors has to be free of carbon dioxide and sulfide. Carbon dioxide has to be removed since it does not burn, and sulfide is corrosive in nature. This proves to be costly when considering biogas as a motor fuel.

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    Introduction

    The situation of energy in the world today, whether in emerging or industrialized countries, is regularly discussed in economic, political, and technical terms. Meanwhile the main sources of energy like coal, natural gas, crude oil, and even nuclear energy are becoming scarce. Bioenergy is deriving more and more significance in terms of research and development.

    Hence the technology of gasification to produce biogas is being researched throughout the world. At a gasification installation, the biofuel is first changed into an explosive gas. This "synthetic gas" is distilled and then converted into biogas with features similar to natural gas.

    Biogas is an explosive gas that is brought forth from the anaerobic putrefaction of organic materials. Biogas consists of methane, which is a combustible material, and various other impurities like carbon dioxide and hydrogen sulfides. Hence biogas cannot be used in its raw form and has to be cleaned to remove impurities before it becomes usable.

    Unique wells have to be bored in order to accurately get biogas out of a landfill. When designed properly, landfills will be a primary source of biogas for several years. This is the most efficient method of trapping all gas formed. Apart from this, biogas has practically no other toxic discharges when compared to fossil fuels.

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    Biogas Car

    Biogas Racer
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    Biogas fuel for vehicles

    When used as fuel for cars, buses, and trucks, biogas has to be promoted to a fuel quality fit for vehicles by removing the hydrogen sulfide, water, and carbon dioxide. The energy content in the upgraded biogas is roughly 10 kWh m3, which is equal to one liter of oil.

    When compressed biogas replaces compressed natural gas in vehicles, it aids in fueling an internal combustion engine and it also is a much more efficient displacer of carbon dioxide. Methane contained in biogas can be distilled by means of a biogas upgrader to the same quality as fossil natural gas and become biomethane. If the local gas system permits for this, the manufacturer of the biogas may use the local gas sharing networks. Biogas thus produced has to be very clean to get to pipeline quality, and has to be of the right composition for the home distribution network to consent.

    Even though biogas has several advantages, the disadvantages outweigh the merits. It is also not feasible for all nations to have access to biogas due to limitations in food production resulting in a shortage of essential raw materials for producing biogas. Let us now look at the problems related to the use of biogas as a fuel for internal combustion engines.

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    Disadvantages/Problems

    The most important factor for biogas production is the high capital required in refining biogas to meet the standards of natural gas for use in IC engines. So the procedure is not striking from the economic viewpoint, when compared to other biofuels, on a large manufacturing scale. Apart from this, biogas consists of some gases which are corrosive in nature to metals, which is problematic as the major components of internal combustion engines are metals.

    The real product worth of biogas is exceedingly low, which does not essentially make it economically practical. Special wells have to be drilled which again results in heavy cost. The yields of biogas are lower because of its dilute nature of substrates and thus lead to noise and air pollution. It also results in water pollution since a lot of industrial waste stays on after the process of putrefaction. At the same time it can also cause obnoxious smells.

    The major disadvantage of using biogas in internal combustion engines are its limited quantity and the local production since biogas stations are seldom situated in positions where they are required such as bus depots, etc.

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    Conclusion and references

    The creation and use of biogas as a fuel for internal combustion engines is a wide and multifaceted topic. The applications in treating sewage waste to produce biogas are of course a comparatively new topic. To be utilized as a transportation fuel, biogas has to be putrefied to at the least 95% methane. This can then be utilized in vehicles initially customized to function on natural gas. Even though the technology is convincingly well developed and there is a large range of vehicles obtainable across different countries, a limited refueling infrastructure establishes the deficiency in the growth of the gas vehicle market. The main reason for this is that it is presently not an economically striking option for transport operators. Also changing completely to the biogas fuel requires a high level of dedication and a considerable point of profit to the user, but this is not possible due to the lack of vehicle accessibility and refueling infrastructure.

    References

    Diesel Engine Modification to operate on Biogas, by J. Ortiz Canavate et al, Transactions of the ASAE.

    Engineering Thermodynamics, Work and Heat Transfer, by G.F.C. Rogers and Y.R. Mayhew Longman Publishers, London, U.K.

    George Tchobanoglous, et al "Integrated Solid Waste Management - Engineering Principles and Management Issues", MCGraw-Hill International Editions. Pg.382