An additive for odor control in litter is often sodium bicarbonate or baking soda. Here is a homemade solution for cat owners to help with odor control in the litter box. Sprinkle a couple of tablespoons of baking soda into the litter. You do need to be diligent about doing this and repeating as necessary. It will work in the same way as placing sodium bicarbonate inside a refrigerator to absorb odors which is by simply leaving an opened packet of bicarb soda in the fridge.