A Pilot Study Of the St.Louis Airshed

Abstract

A linear programming model for air pollution control, adapted to the St. Louis airshed for the year 1975, is described in this paper. It is assumed that air quality goals can be achieved by reducing total emissions of each pollutant to given allowable levels. The pollutants considered are carbon monoxide, hydrocarbons, nitrogen oxides, sulfur dioxide, and particulates. With the exception of carbon monoxide, the allowable levels are related to air quality goals adopted by the Missouri Air Conservation Commission. The computer solution indicates the set of control methods which achieves the required pollutant reductions at the least total cost. The minimal cost of reducing the five pollutants to permissible levels in 1975 is $35 million a year. Of this cost, $15 million is for the control of coal burning sources. The use of low sulfur coal proved to be less important than processes for removing sulfur dioxide from the flue gas of power plants and the substitution of natural gas for coal. The solution indicated that 14 billion cubic feet of natural gas should replace coal in all boilers other than those with travelling grate or pulverized coal stokers. This result was obtained even though the cost of natural gas was increased to account for possible disparity in total reserves between the two fuels. It was found that if 1$ of all natural gas substituted for coal were found to leak into the atmosphere as hydrocarbon pollution, the desirability of natural gas for pollution control would be scarcely impaired. The model has a number of limitations, one of them being that all sources in the airshed are considered equal with respect to location. However, special locational situations can be tested. For example, it was found that a large power plant, located at the perimeter of the airshed should have stack gas cleaning equipment even if 87½% of its emissions never enter the airshed. The model permits reexamination of the air quality goals from a cost viewpoint. For example, it is shown that in 1975 if the allowable level of nitrogen oxides in the airshed were increased 0.1%, there would be a saving in control cost of $99,000, while the allowable level of sulfur dioxide could be decreased by the same percentage for $9000. These trade-off relationships may be useful to scientists evaluating the relative damaging capabilities of the individual pollutants.