Automatic Litterbox Central

I had to take my cat to the vet because he was having respiratory problems. After an extensive exam and blood tests, my vet said he was having some kind of an allergic reaction. He recommended that I stop using candles, air fresheners, household chemicals etc. However, I couldn't notice any improvement on my cat. Thus, after an an extensive research on line to find the cause of his allergy, I learned that the crystals contain silica gel which is used for the absorption of pet urine. Then, I visited the Wikipedia encyclopedia on line and found that one of its harmful effects of silica gel is the irritation of the respiratory system on some cats. Thus, I stop using the crystals and noticed that my cat's health has improved considerably.

Since I have to use an environmentally free litter, I can no longer use the rack and have to dispose of everyting manually. Does anyone know of any other litter that may be used with the ScoopFree tray? Many thanks.

Hereiam