CREATE TABLE table_204_909 (id DECIMAL, "pollutant" TEXT, "units" TEXT, "emission standard" DECIMAL, "coal-fired" TEXT, "petroleum coke-fired" TEXT)

what is the only pollutant that has 0.0 petroleum coke fired ?
SELECT "pollutant" FROM table_204_909 WHERE "petroleum coke-fired" = 0
SELECT "pollutant" FROM "table_204_909" WHERE "petroleum coke-fired" = 0