Hundreds of forests are found to have been buried one over another. The buried vegetation breaks down, giving out gases. This composition first becomes peat and overtime, eventually changes into coal. Do you know what we use coal for today? In the past, coal was used as the power source for our motor engines, as heat source for our homes and energy source to many industries, etc. Today, the use of coal has been replaced with other cleaner and more environmental friendly sources but it is still in use in some cases. Special technology to harvest and use ‘clean coal’ have been developed over the years.