BIOMASS

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.1 INTRODUCTION
Biomass as the solar energy stored in chemical form in plant and animal materials is among the most precious and versatile resources on earth. It provides not only food but also energy, building materials, paper, fabrics, medicines and chemicals. Biomass has been used for energy purposes ever since man discovered fire. Today, biomass fuels can be utilised for tasks ranging from heating the house to fuelling a car and running a computer.

THE CHEMICAL COMPOSITION OF BIOMASS
The chemical composition of biomass varies among species, but plants consists of about 25% lignin and 75% carbohydrates or sugars. The carbohydrate fraction consists of many sugar molecules linked together in long chains or polymers. Two larger carbohydrate categories that have significant value are cellulose and hemi-cellulose. The lignin fraction consists of non-sugar type molecules. Nature uses the long cellulose polymers to build the fibers that give a plant its strength. The lignin fraction acts like a “glue” that holds the cellulose fibers together.

WHERE DOES BIOMASS COME FROM?
Carbon dioxide from the atmosphere and water from the earth are combined in the photosynthetic process to produce carbohydrates (sugars) that form the building blocks of biomass. The solar energy that drives photosynthesis is stored in the chemical bonds of the structural components of biomass. If we burn biomass efficiently (extract the energy stored in the chemical bonds) oxygen from the atmosphere combines with the carbon in plants to produce carbon dioxide and water. The process is cyclic because the carbon dioxide is then available to produce new biomass.



BIOMASS - SOME BASIC DATA
* Total mass of living matter (including moisture) - 2000 billion tonnes
* Total mass in land plants - 1800 billion tonnes
* Total mass in forests -1600 billion tonnes
* Per capita terrestrial biomass - 400 tonnes
* Energy stored in terrestrial biomass 25 000 EJ
* Net annual production of terrestrial biomass - 400 000 million tonnes
* Rate of energy storage by land biomass - 3000 EJ/y (95 TW)
* Total consumption of all forms of energy - 400 EJ/y (12 TW)
* Biomass energy consumption - 55 EJ/y ( 1. 7 TW)

BIOMASS IN DEVELOPING COUNTRIES
Despite its wide use in developing countries, biomass energy is usually used so inefficiently that only a small percentage of its useful energy is obtained. The overall efficiency in traditional use is only about 5-15 per cent, and biomass is often less convenient to use compared with fossil fuels. It can also be a health hazard in some circumstances, for example, cooking stoves can release particulates, CO, NOx formaldehyde, and other organic compounds in poorly ventilated homes, often far exceeding recommended WHO levels. Furthermore, the traditional uses of biomass, i.e., burning of wood is often associated with the increasing scarcity of hand-gathered wood, nutrient depletion, and the problems of deforestation and desertification. In the early 1980s, almost 1.3 billion people met their fuelwood needs by depleting wood reserves.

FOOD OR FUEL?
A major criticism often levelled against biomass, particularly against large-scale fuel production, is that it could divert agricultural production away from food crops, especially in developing countries. The basic argument is that energy-crop programmes compete with food crops in a number of ways (agricultural, rural investment, infrastructure, water, fertilizers, skilled labour etc.) and thus cause food shortages and price increases. However, this so-called “food versus fuel” controversy appears to have been exaggerated in many cases. The subject is far more complex than has generally been presented since agricultural and export policy and the politics of food availability are factors of far greater importance. The argument should be analysed against the background of the world’s (or an individual country’s or region’s) real food situation of food supply and demand (ever-increasing food surpluses in most industrialized and a number of developing countries), the use of food as animal feed, the under-utilized agricultural production potential, the increased potential for agricultural productivity, and the advantages and disadvantages of producing biofuels.


LAND AVAILABILITY
Biomass differs fundamentally from other forms of fuels since it requires land to grow on and is therefore subject to the range of independent factors which govern how, and by whom, that land should be used. There are basically two main approaches to deciding on land use for biomass. The “technocratic” approach starts from a need for, then identifies a biological source, the site to grow it, and then considers the possible environmental impacts. This approach generally had ignored many of the local and more remote side-effects of biomass plantations and also ignored the expertise of the local farmers who know the local conditions. This has resulted in many biomass project failures in the past. The “multi-uses” approach asks how land can best be used for sustainable development, and considers what mixture of land use and cropping patterns will make optimum use of a particular plot of land to meet multiple objectives of food, fuel, fodder, societal needs etc. This requires a full understanding of the complexity of land use.
Generally it can be said that biomass productivity can be improved since in many place of the world is low, being much less than 5 t/ha/yr. for woody species without good management. Increased productivity is the key to both providing competitive costs and better utilisation of available land. Advances have included the identification of fast-growing species, breeding successes and multiple species opportunities, new physiological knowledge of plant growth processes, and manipulation of plants through biotechnology applications, which could raise productivity 5 to 10 times over natural growth rates in plants or trees.