Biomass is one of the oldest forms of energy. Wood was the most commonly used source for heat and cooking, and is still the largest biomass energy resource today.

Biomass is an organic matter and is basically a form of solar energy. The term is used for all materials originating from photosynthesis. In one week, the earth receives an amount of energy equivalent to total reserves of non-renewable energy.

In other words, energy in one day’s sunlight is equivalent of 1/5 of the known reserves of fossil fuels. By photosynthesis, solar energy can be converted into biomass, which in turn can be stored and used as fuel in various forms. Many of the microorganisms when they digest the biomass in the absence of air produce alcohol or methane gas, which imparts energy on combustion.

Since biomass is obtained through the process of photosynthesis, biomass energy is considered to be another form of indirect use of solar energy. The reaction of photosynthesis in the presence of solar radiation can be represented as follows:


Solar energy

In this reaction, water and C02 are converted into organic material, i.e., CH0 which breaks at high temperature and releases the amount of heat equal to 112,000 cal. /mole.

CH20 + 02 ————— ► C02 + H,0 + 112 K.Cal./mole

Solar energy ———– ► Photosynthesis ———– »- Energy generation


For direct burning, moisture contents should be less than 30 per cent. Wood and straw is normally used for combustion. Animal wastes, sewage sludges, compost sludges, which contain upto 75 per cent water, can also be used. Pyrolysis, liquefaction and gasification are upgrading processes converting biomass into stable, transportable fuel solid, liquid. Gaseous forms thus produced have similar properties as coal, oil and natural gas.