Dry mill ethanol plants have traditionally used natural gas as the process fuel for production. Natural gas is used to raise steam for mash cooking, distillation, and evaporation. It is also used directly in DGS dryers and in thermal oxidizers that destroy the volatile organic compounds (VOCs) present in the dryer exhaust.The industry has made great progress in reducing energy consumption since its start in the 1980s; to produce a gallon of ethanol, today's dry mill plants only use about half of the energy used by the earliest plants. Still, natural gas prices are on the rise, and energy costs are second only to raw material costs in the dry mill process. These factors are driving the industry to undertake further efforts to reduce energy use, or to switch from natural gas to other fuels such as coal, wood chips, or even the use of DGS and other process byproducts.