Non conventional energy sources – Energy from biomass

Biomass is a potential source of renewable energy. This includes all the organic materials such as crop residue, natural vegetation, trees, animal dung and sewage. Biomass energy or bio conversion refers to the use of this material as fuel or its conversion into fuels.

There are many methods used for the conversion of biomass into fuels. But the most common are

1. Direct combustion
2. Fermentation

Direct combustion method is usually applied to get energy from waste products commonly known as solid waste. It will be discussed in the next section.

Biofuel such as ethanol (alcohol) is a replacement of gasoline. It is obtained by fermentation of biomass using enzymes and by decomposition through bacterial action in the absence of air (oxygen).

The rotting of biomass in a closed tank called a digester produces biogas which can be piped out to use for cooking and heating (Fig. 4.16).


Fig: 4.16

For your information

The rapid growth of human population has put a strain on our natural resources. A sustainable society minimizes waste and maximizes the benefit from each resource. Minimizing the use of energy is another method of conservation. We can save energy by.

(i)              Turning of lights and electrical appliances when not in use.

(ii)            Using fluorescent bulbs instead of incandescent bulbs

(iii)           Using sunlight in offices, commercial centers and houses during daylight hours

(iv)           Taking short hot shavers.


The waste material of the process is a good organic fertilizer. Thus, production of biogas provides us energy source and also solves the problem of organic waste disposal.

Energy from waste products

Waste products like wood waste, crop residue, and particularly municipal solid waste can be used to get energy by direct combustion. It is probably the most commonly used conversion process in which waste material is burnt in a confined container. Heat produced in this way is directly utilized in the boiler to produce steam that can run turbine generator.

Do you know?
Pollution can be reduced if

(i)              People use mass transportation

(ii)            Use geothermal, solar, hydroelectrical and wind energy as alternative forms of energy.

Geothermal energy

This is the heat energy extracted from inside the earth in the form of hot water or steam. Heat within the earth is generated by the following processes.

1.         Radioactive Decay

The energy, heating the rocks, is constantly being released by the decay of radioactive elements.

2.         Residues’ heat of the Earth

At some places hot igneous rocks, usually within 10 km f the Earth’s surface, are in a molten and partly molten state. They conduct heat energy from the Earth’s interior which is still very hot. The temperature of these rocks is about 200ᵒC or more.

3.         Compression of Material

The compression of material deep inside the Earth also causes generation of heat energy.

In some place water beneath the ground is in contact with hot rocks and is raised to high temperature and pressure. It comes to the surface as hot springs, geysers, or steam vents. The steam can be directed to turn turbines of electric generators.

At places water is not present and hot rocks are not very deep, the water is pumped down through them to get steam (Fig. 4.17). The steam then can be used to drive turbines or for direct heating.


Fig. 4.17

An interesting phenomenon of geothermal energy is a geyser. It is a hot spring that discharges steam and hot water, intermittently releasing an explosive column into the air (Fig. 4.18). Most geysers erupt at irregular intervals. They usually occur in volcanic regions. Extraction of geothermal heat energy often occurs closer to geyser sights. This extraction seriously disturbs geyser system by reducing heat flow and aquifer pressure. Aquifer is a layer of rock holding water that allows water to percolate through it with pressure.


Fig: 4.18