a) Any system can sustain a limited no. Of organisms on a long term basis which is known its carrying capacity.

b) In case of human beings carrying capacity concept becomes quite complex. It is because unlike other animals, human beings not only need food to live. But so many other things to make a quality life.

Sustainability of system depends largely on carrying capacity .say if carrying capacity of system is crossed (Exploitation to natural resource) environmental degradation starts and continues till it reaches to a point of no return. Carrying capacity has two basic component –1.Supporting capacity (capacity to regenerate) & 2.Assimilating capacity (capacity to tolerate different stress) So, in order to attain sustainability it is very important to utilize resource based on these two property of system.

c) A large amount of waste generation which has to be disposed of properly using energy based techniques.

d) Control and prevention of air and water pollution which need energy dependent technologies.

Due to high population density and high energy demanding activities, urban problems related to energy are magnified as compared to rural problems. Hence resources utilization as per carrying capacity is important.