Energy is produced mainly from non-renewable sources such as petroleum, natural gas, coal and lignite. They are usually referred to as non-renewable, because extraction from the stock depletes the usable quantity remaining. And even if some is being formed, the rate of formation is too slow compared to the time scale of their utilization. The non-renewable sources are also called fund or stock resources. They are also called conventional sources as they use age-old technological for energy generation.
Energy can also be produced from another natural resources, such as living organisms and their products, by trapping solar radiation. Thee resources are called renewable resources or flow resources because they involve organic growth and reproduction, also because they are relatively quickly recycled or renewed in nature, as in case of water in the hydrologic cycle. The renewable sources of energy are also called non-conventional sources of energy because the techniques for their exploitation have been developed comparatively recently. These are also referred to as alternate sources of energy because they offer and alternative to conventional sources of energy.
The energy sources and their manner of use may be categorized as conventional and non-conventional of commercial and non-commercial, renewable and non-renewable, and terrestrial or solar, etc, but the environmental impact of these energy sources cannot be readily understood in isolation.
However, one thing is certain that energy efficient systems will have to be developed to make the goal of self-reliance a reality. The means of conserving energy are by nature fragmented and unglamorous. Use of biogas plants, draught power, bullock-carts, insulated mud houses, collection of rain water on house tops, conservation of polyethylene packets, recycling of solid wastes and so on are not perhaps intrinsically as captivating as atomic with such grandiose energy supply options ha got us into our current predicament. We should now concentrate upon simple but useful alternatives of energy sources, which are conventionally compatible, and economically within our reach.
In the following sections, we will study some of the important means of energy conservation through the incorporation of innovative and imaginative alternatives within conventional rural agricultural technologies.