Consider the following statements with reference to bioenergy as a renewable energy source: 1. Plants ensure a continuous supply of gas due to their continuous growth 2. Cost of obtaining energy from biogas is less than that from fossil fuels 3. Digestion of sludge may produce H2S and NOx which am injurious to human health 4. ‘Floating dome’ installation is the preferred option as it supplies gas at constant pressure irrespective of the quantity of gas produced Which of the above statements are correct? Correct Answer 1, 2 and 4 only Bioenergy as a renewable energy source: Plants take solar energy through the process of photosynthesis and convert it into organic matter. Bioenergy is generated when the biomass obtained is burned in the form of wood, charcoal, animal waste and human waste, etc Biomass such as straw, dry vegetables, dry leaves, dry sewage, etc has to be decomposed aerobically. Biomass such as cow dung, leaves, sewage, human excreta, etc has to be decomposed anaerobically. Anaerobic decomposition of organic matters produces biogas such as methane (CH4) and carbon dioxide (CO2). Obtaining energy from fossil fuels is very costly as it requires many costly processes to extract it and purify and also it is a non-renewable energy. On the other hand, energy obtained from biogas is renewable and can be obtained at a low cost While sludge digestion, Out of total volatile solids, 65 % are induced to gasses and 35 % formed in digested sludge. Out of the total gasses formed, 70 % is methane (CH4) and 30 % is Carbon Dioxide (CO2). Traces of other inert gases like nitrogen, hydrogen sulphide, etc. are also produced. Types of biogas plants Different parameters Fixed dome biogas plant Floating dome gas plant Material made of Cement and bricks Mild-steel, Ferro-cement Masonry skills High skills required Low skills required Reliability of structure Low reliability due to high construction failure High reliability Gas pressure Variable gas pressure Constant gas pressure