09-10-2012, 12:35 PM
Fuel from Wastes and Weeds
Fuel from Wastes.doc (Size: 68.5 KB / Downloads: 53)
Introduction
The steep increase in the cost of oil and the uncertainty of its availability is being realized all over the world. In order to meet the future energy need it is necessary to develop and use the non-conventional sources also. Among a number of options available, biomass is one of the potential sources of energy as solid, liquid and gaseous fuel. Fuel from biomass is obtained from a variety of fuel stocks such as wood, charcoal, dung, vegetable, water, etc. More than one third of the world's population depends on wood for cooking and heating. But increased population, industrialization and urbanization have encroached upon forest land, thereby creating wood fuel scarcity. The woods available with us is not sufficient to meet the demands of timber, pulp and paper industries. Therefore, alternatives are to be searched for. Among the biomass sources, wastes and weeds are available in bulk, almost free of cost and the fuel value of these is not utilized properly. If utilized in a right way, they can meet 75% of the demands of the rural population in India. By a number of technologies, wastes and weeds can be converted to solid, liquid and gaseous fuels, which can be used for cooking, lighting, heating, pumping water, fuel for industry, transport and electricity generation. For more details about conversion methods refer booklet No.379 on "Biomass as a source of energy"
Agro-industrial wastes
About 79% of these wastes are available from Uttar Pradesh, Andhra Pradesh, Tamil N adu, Maharashtra, Karnataka, Punjab and Gujarat. Important wastes are rice husk, bagasse, molasses, coconut shells, coconut husk, cotton dust, jute mill waste, etc.
Food industry wastes
During the processes of canning, drying and preservation of fruits and vegetables, their peels, cores, pits, vines, stems and other materials accumulate. A bulk of peelings and fruit cakes (matter left after juice extraction from fruit) are available at fruit juice shops on urban areas. Almost in every house we find vegetable peelings.
Animal wastes
Among animal wastes, dung, poultry, and sheep droppings and other wastes are used for fuel. In our country, about 1300 million tonnes of dung is available annually from all types of animals. Of total dung 84% is cow dung and buffalo dung and 13% goat and sheep droppings. About 58% of the total dung produced in India, is contributed by Uttar Pradesh, Rajasthan, Madhya Pradesh, Maharashtra and Andhra Pradesh. Dung is put to use as dung cakes and biogas for fuel purposes. Other than this, in general, cattle shed wastes, fisheries, prawn and frog wastes, slaughter; house wastes are the other animal wastes.
Rice
Rice husk is more important than bran as it has more calorific value compared to bran which ranges from 2940- 3460 kilo cals/kilogram. Three kilograms of this residue has the same calorific value as 1.5 kg coal or1 kg fuel oil. It has high silica content, ash content and 12-17% carbon and 15- 18.5% ash as fuel properties which makes it easy for complete combustion to produce energy. Rice husk produced energy is useful for furnaces, for large-sized rice mills, for dehydration industries, for tobacco industry, brick kilns etc. In post-harvest operations also rice husk energy is used.
Rice straw has a high energy value of 3000-3500 kcals/ kg which can be devesified to fuel briquettes. It can be hydrolysed and fermented to ethanol. Powcr can also be generated from the straw at a cheaper rate compared to thermal plant. With cattle dung and rice straw (1:2) produces biogas.
Maize
Among maize residues, maize cobs and maize stalks are widely used as fuel in rural India. Maize cobs comprise about 30% of maize grain. They can be directly burnt as fuel having a heating value of 3500 kcals/kilogram. Charcoal from cobs can be made by burning a sack of com cobs in a oil container (drum) completely till a smokeless flame is attained. Then, this completely burnt charcoal is spread over the floor and quenched with water to avoid further combustion. It is allowed to dry under direct sunlight. Sieving can be done to let out the loose portions and charcoal is collected and stored.
Water hyacinth
Eicchornia cvassipes is also a free-floating plant and it can produce 17.8 tonnes of biomass per hectare per day. Its C/N ratio ranges between 18-26 which is optimum for the bio- gas production. For that, the plants are collected and sun-dried. The dried material is powdered in a mill. In the mill, the soil is mixed with water hyacinth powder for proper sedimentation. Introduction of soil increases the micro-flora. In general 4.5-6.3% slurry gives maximum biogas production. One kg of water hyacinth can yield 37 4litres of biogas containing 60-80% methane.
Water hyacinth takes 3 days for decomposition during summer and 4 days in winter season when compared to 8 and 12 days respectively for cow dung decomposition. However, 1:1 ratio of water hyacinth and cow dung gives maximum gas production than either of the substrate.
Utilization of water hyacinth for gas production has gained considerable momentum in India. Agricultural universities are also working On this. Biogas produced from this plant can be used for cooling, heating, lighting and even as a. source of power for engines, tractors, cars, etc.