Fuel oil pollution control and additional maintenance required after burning it often outweigh the low cost of the fuel. Burning fuel oil, particularly residual fuel oil, produces uniformly higher carbon dioxide emissions than natural gas. Heavy fuel oils continue to be used in the boiler "lighting up" facility in many coal-fired power plants. This use is approximately analogous to using kindling to start a fire. Without performing this act it is difficult to begin the large-scale combustion process. The chief drawback to residual fuel oil is its high initial viscosity, particularly in the case of No. 6 oil, which requires a correctly
Oxy-fuel combustion process sets of regenerative flue ducts allowed for the air flow to be reversed at regular intervals, and thus maintain a high temperature in the incoming air. By allowing new furnaces to be built without the expense of regenerators, and especially with the added benefit of nitrogen oxide reduction, which allows glass plants to meet emission restrictions, oxy-fuel is cost effective without the need to reduce CO emissions. Oxy-fuel combustion also reduces CO release at the glass plant location, although this may be offset by CO production due to electric power generation which is necessary to produce oxygen for the combustion