The correct answer is option 4: Heating capacity of biogas is very low. This statement is incorrect. Biogas, including gobar gas, actually has a high heating capacity. Biogas is a gaseous fuel that is produced through the decomposition of organic matter such as cow-dung, crop residues, vegetable waste, and sewage in the absence of oxygen. It is primarily composed of methane, which is a potent greenhouse gas and a reliable source of energy.

Biomass is indeed a renewable source of energy, making option 1 correct. It refers to organic materials such as plants, crop residues, wood, and animal manure that can be used as an energy source. Biogas generation, as mentioned in option 3, is indeed beneficial for the environment as it helps in reducing soil and water pollution by utilizing organic waste.

In conclusion, option 4 is the correct answer as it states incorrect information about the heating capacity of biogas. Alert - correct answer should be: 4. Biogas has a high heating capacity, not low.