Bio-fuels are fuels that are formed biological matter decomposes.Most bio-fuels are derived from plants.Bio-fuels exist in all the three states of matter: solid, liquid, and gas.

Difference between bio-fuels and fossil fuels:
• Bio-fuels can be made extremely fast, in a matter of days whereas fossil fuels take a million years to build whereas .
• Bio-fuels are renewable sources of energy.Fossil fuels are not.
• Bio-fuels are comparatively safer while fossil fuels generate huge amounts of pollution.

Different types of bio-fuels
Bio-fuels are categorized into four types: first generation, second generation, third generation, and fourth generation.

The first generation bio-fuels are derived from food-crops like vegetable,starch and sugar. They are also derived from animal fats.Example of first generation bio-fuels includes bio-diesel, bio-gas, and vegetable oil.

The second generation of bio-fuels is mainly derived from waste biomass.Examples of this kind of bio-fuels are different kinds of alcohols and diesel generated from wood.

The third generation comprises of bio-fuels derived from algae. The algae fuels can easily decompose into the soil.They are very environmental-friendly.To create bio-fuels,algae are farmed on large scales.

The fourth generation of bio-fuels are derived by chemical reaction between carbon dioxide and micro-organism.

Advantages of bio-fuels
Bio-fuels prove advantageous in the following ways:
• Bio-fuels make fossil fuels less important.Thus we do not have to afraid even fossil fuels are vanishing.
• Bio-fuels help reduce carbon emissions into the atmosphere.They are environmental-friendly.
• Bio-fuels, especially, bio-diesel are very cost-effective.

Disadvantages of bio-fuels
Bio-fuels are not perfect. Although bio-fuels have a lot of benefits to environment, there are some drawbacks.Some of them are listed below:
• Bio-fuels can be generated from food-crops.This reduce the food supply for human. Some people believe that food should be farmed for human consumption but not for making fuels.
• Making bio-fuels require acres of farming land, thus encroaching upon the natural habitat of plants and animals