You may have heard of the use of cattle dung for production of biogas which is used for cooking. Water weeds like water hyacinth, water lettuce, salvinia, hydrilla, duck weeds and algae are found to be useful supplement to cattle dung. Biogas can be used not only as cooking gas, it can also be used to raise steam, which can be used for running engines or machines in the factories or for running turbines to generate electricity. It has been found that large biogas plants can supply the needs of a number of families or even small villages. What is left over after generating the gas, can be used as manure. Hence this is also an economical way of getting more energy. That is why in countries like China or India, great efforts are being made to instal tens of thousands of biogas plants in rural areas. Now that you have studied about various kinds of resources, you would like to know about the methods used for exploring these resources.