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ABSTRACT: The idea of biogas as a diesel fuel substitute is not new. It is a very attractive alternative, especially in countries rich in agricultural products and poor in petroleum resources. It can be concluded from the study that while running a diesel engine in dual fuel mode i-e on diesel and biogas saved almost 62% to 64% diesel fuel, and consequently showing an annual saving of Rs. 3486/m^sup 3^ and 3379/m^sup 3^ capacity when run on dual fuel mode with respect to gas produced from fixed dome and floating drum biogas digesters respectively. The less saving in floating type biogas digester is due to gas losses from plant as compare to fixed dome biogas digester where system is air tight. Fixed dome biogas digester not only save the money but also the environment. Running engine through floating type biogas digester consumed 6.35% more diesel than fixed dome biogas digester in dual fuel mode. A 16 hp dual fuel diesel engine pumped 14 % more water from fixed dome biogas plant as compared floating drum biogas plant. It is therefore recommended that fixed dome biogas digester may be installed in such agroecological zones like Islamabad.
KEYWORDS: Biogas, fixed dome and floating type biogas digesters, diesel engine, centrifugal pump, dual fuel.
1 BACKGROUND
Pakistan is an energy deficient country that's why the interest in use of alternative energy and energy conservation has skyrocketed. The rapidly escalating fuel costs have compelled to move toward renewable and sustainable energy sources. The agriculture sector continues to be an essential component of Pakistan's economy contributing 21% to GDP. Agriculture generates productive employment opportunities for 45 % of the country's labor force and 60 % of the rural population [1]. The agriculture sector is not the largest energy-consuming sector of Pakistan however; it is in transition from the traditional i.e. low energy inputs methods of farming to higher level of energy inputs, of cope the food requirements of the country's population growing at a rate of almost 3% [1]. The price hike in fuel products are increasing the input cost of production, making agriculture as an unprofitable and unattractive business in the country. Shortage of water and energy are two major issues currently faced by irrigated agriculture in Pakistan [2]....