Nearly 50% of the energy used within the industry is transformed into chemical products. For example, liquefied petroleum gases (a mixture of gases such as ethylene, ethane, propane, propylene) serve as feedstocks for the manufacture of polyethylene, polypropylene, and a host of other products. Also, natural gas is used to produce ammonia, a raw material used in the production of many fertilizers. The chart below shows total inputs for heat and power (no feedstocks). The largest use of energy for heat and power (43%) is in boilers used to produce steam to drive chemical reactions and perform product separation and finishing operations. Other process heating and cooling accounts for about 27% of energy use. Electricity is used to power equipment and drive electrochemical processes, as well as to heat, light, and cool industry facilities. [MECS 1994]