BIOMASS
Definition
Energy from biomass is the oldest fuel used by humans. Our ancestors burned wood to keep the cave warm. Biomass is a renewable energy resource derived from plants and animal waste. The energy from biomass (biomass conversion) is released on burning or breaking the chemical bonds of organic molecules formed during photosynthesis. Thus, biomass represents an indirect form of solar energy. Biomass fuels can be used directly or they can be transformed into more convenient form and then used.
| More than one million people in the world still use wood as primary source of energy for cooking |
Sources of biomass
- It is derived from numerous sources, including the by-products from the timber industry, agricultural crops and their by products, raw material from the forest, major parts of household waste and wood.
- Biomass can be burnt directly as a source for cooking, heating, lighting, generating steam, for industrial use for producing electricity.
- Can be used to generate gaseous fuels (gasification).
- Can be converted into alcohol (liquid biofuels) by distillation.
Methane and biogas can be produced from urban wastes in landfills and sewage at waste water treatment plants. In some facilities, manure from livestock and other organic waste is converted by microorganisms in specially designed digestion chamber to form methane (CH4), which is burned to produce electricity, used in fuel cell, or used as fuel for vehicles. Molasses obtained from sugarcane is fermented to produce ethanol, that can be used in automobiles.
| Half a kilo of dry plant tissue can produce as much as 1890 K Cal of heat which is equivalent to the heat available from a quarter of kilogram of coal. |
Uses of biomass
- Traditional use of biomass is more than its use in modern application. In the developed world biomass is once again becoming important for applications such as combined heat and power generation.
- In addition, biomass energy is gaining significance as a source of clean heat for domestic heating and community heating applications. In fact. in countries like Finland, USA and Sweden use of biomass energy is increasing biomass fuels used in India account for about one third of the total fuel used in the country, and it amount to 90% of the rural households.
- Instead of burning loose biomass directly, it is more practical to compress it into briquettes (compressing them into blocks of a chosen shape) improve its utility and convenience of use. Such biomass in the biomass briquettes can be used as fuel in place of coal in traditional chulhas and furnaces or in a gasifier. A gasifier converts solid fuels into a more convenient-to-use gaseous fuel called producer gas.
| · Form of Energy: Chemical energy · This energy is being used for: Cooking, mechanical, applications/pumping, power generation, transportation. · Some of the gadgets and other devices: Biogas plant/gasifier/burner, gasifier engine pump sets, sterling engine pump sets, producer gas/ biogas-based engine generator sets, ethanol/methanol. |
Advantages of biomass energy
Burning of biomass does not increase atmospheric carbon dioxide because to begin with biomass was formed by atmospheric carbon dioxide and the same amount of carbon dioxide is released on burning. Biomass is an important source of energy and the most important fuel worldwide after coal, oil and natural gas.
- Biomass is renewable and free from net CO2 (carbon dioxide) emissions and is abundantly available on the earth in the form of firewood, agricultural residues, cattle dung, city garbage etc. Bio-energy, in the form of biogas, which is derived from biomass, is expected to become one of the key energy resources for global sustainable development.
Bagasse as biofuel
- Indian sugar mills are rapidly turning to bagasse, the leftover of cane after it is crushed and its juice extracted, to generate electricity. This is mainly being done to clean up the environment, cut down power costs and earn additional revenue. According to current estimates, about 3500 MW of power can be generated from bagasse in the existing 430 sugar mills in the country. Around 270 MW of power has already been commissioned and more is under construction.
Biogas plant
- The biogas plant consists of two components: a digester (or fermentation tank) and a gas holder. The digester is a cube-shaped or cylindrical waterproof container with an inlet into which the fermentable mixture is introduced in the form of liquid slurry. The gas holder is normally an airproof steel container that, by floating like a ball on the fermentation mix, cuts off air to the digester (anaerobiosis) and collects the gas generated. In one of the most widely used designs, the gas holder is equipped with a gas outlet, while the digester is provided with an overflow pipe to lead the sludge out into a drainage pit.
- Any biodegradable (that which can be decomposed by bacteria) substance can be fermented anaerobically (in absence of oxygen) by methane-producing (methanogenic) bacteria. Cow dung or faeces are collected and put in a biogas digester or fermenter (a large vessel in which fermentation can take place). A series of chemical reactions occur in the presence of methanogenic bacteria (CH4 generating bacteria) leading to the production of CH4 and CO2.
- Methanogenesis is a microbial process, involving many complex, and differently interacting species, but most notably, the methane-producing bacteria and consists of three stages; hydrolysis, acidification and methane formation.
- In India, the dissemination of large–scale biogas plants has begun in the mid-seventies and the process has become consolidated with the establishment of the National Project on Biogas Development (NPBD) in 1981. Against the estimated potential of 12 million biogas plants, 2.9 million family type and 2700 community, institutional and nightsoil-based plants have been set up till December 1999. This is estimated to have helped in a saving of 3 million tonnes of fuelwood per year and manure containing nitrogen equivalent to 0.7.
However, in terms of total dung that is available in the country, the potential is much more. The bovine population in India is 260 millions. As an adult, bovine produces an average of 10 kg of dung per day. If it is assumed that 75% of the dung is collected, nearly 2 millions tonnes of dung would be available everyday. This dung can feed as many as 40 millions biogas plants which can be considered the ultimate potential for biogas technology.
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But even this high potential of biogas is based on animal dung only. However, all organic matter can technically be used to generate methane; if the scientific experiments that are going on in the country to develop alternative feedstocks (such as water hyacinth, kitchen waste, and poultry waste) become successful, potential for biogas generation could be virtually unlimited. It can be mentioned in this context that human waste is an excellent source of biogas which would enhance the potential; substantially. With such high potential, which can be routed to hitherto unemphasized applications of shaft power and electricity generation, biogas can make a significant contribution to the development of small industries and agriculture, and thus to the overall advancement of the rural areas.
Biogas in Rashtrapati Bhavan
GOING Green starts from the top, and in the capital the President’s Estate is taking the lead. Besides lighting an entire auditorium wing with solar power, the Rashtrapati Bhavan is using cow dung-fuelled biogas in its kitchen for the President’s bodyguards. |