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

what is the total number of pollutants that are measured with an lb/mmbtu unit ?
SELECT COUNT("pollutant") FROM table_204_909 WHERE "units" = 'lb/mmbtu'
SELECT COUNT("pollutant") FROM "table_204_909" WHERE "units" = 'lb/mmbtu'