The second law of thermodynamics states that not all of the energy is used because some of the energy is lost in the form of heat. The lost heat energy is an unusable form of energy, and it causes an increase in the entropy of the universe. Thus, no energy transfer process is efficient due to the loss of energy.
Answer:
Oil
Explanation:
Since, unlike oil, source like wind, solar, water etc. come naturally we don't and can't replace them but when the viscosity in oil has been used up it must be change to allow the proper functioning of the machine.
My guess would be burning the waste
