Mix baking soda, citric acid, lemon zest and rosemary in a small bowl.  Add the essential oils and mix again using your hands, if needed, to break up chunks. Slowly add the water, mixing as you go, until the mixture sticks together like wet sand (it will fizz slightly but pouring slowly should minimize this). The more essential oils you use, the less water you will need.  If you add too much water by mistake, just add more baking soda until you get the desired texture. 

Scoop the mixture into a silicone mold or ice cube tray and press firmly. Allow to dry overnight until you can remove the tabs without them crumbling.  This recipe makes approximately 12 – 16 tabs depending on the size of your mold.

To use, place 2-3 disposal tabs down the drain and turn the faucet on in a thin, steady stream (for more fizz, use 1 cup white vinegar instead of water). Let the water run for about a minute. When the fizzing stops, flush the drain with hot water while running the garbage disposal.