Producers of low-sulfur coal, however, view the President's proposal with considerable cheer.

Since low-sulfur coal represents about 35 percent of the reserves in this country, many producers are worried.

Part of the reason for the relatively low costs is the availability of low-sulfur coal.

But most have found it more economical to switch to low-sulfur coal, or use a blend of the two.

Sulfur levels can also be reduced by burning low-sulfur coal.

Such utilities might, for example, be far from sources of low-sulfur coal or have older plants not well suited to renovation.

Many will switch to alternative fuels like low-sulfur coal.

The other big beneficiaries will be producers of low-sulfur coal.

"We are trying to increase our position in low-sulfur coal and broaden our product line."

The plant said it would keep some low-sulfur coal on hand to burn if the blue plume reappeared.