Here are some thoughts on the issues:
Clumping litter allows for urine ‘clumps’ to be removed from the litterbox, usually with a scoop. However, the use of a scoop is not best in shelters. Using a litter scoop on more than one cat’s litterbox is an obvious way that diarrhea and other illnesses can be spread. (Our volunteers are trained to use small plastic bags to pick up and discard the waste in litterboxes.)
Litter is usually dumped and discarded once a day, typically in the morning. This practice would make ‘regular’ non-clumping litter a more economical choice, since it costs less per pound. Regular litter would also be easier to dump and would leave less residue on the litterbox surfaces. This would make cleaning and refilling the boxes easier.
Another occasion when the litterbox is emptied completely and the litter is ‘dumped’ is whenever a cat or group of cats is adopted. When this happens the kennel needs to be stripped of all furnishings, including the litter, cleaned and sanitized. A considerable amount of litter is regularly discarded for this reason, costing more than if regular litter was used.
Clumping litter is also designed to form very firm clumps. This factor actually makes it dangerous for kittens and even some adult cats. Kittens are more likely than adult cats to get into the litter box with wet feet or step in a fresh pool of urine and then into the dry litter, so they frequently will get clumps of litter stuck to their feet. As they clean their feet, which they learn to do very early in life, they eat the litter. Rather than passing through their digestive tract, the clay lumps tend to collect in the intestines and form cement-like plaques. In some cases, these can become blockages that can be life-threatening. (Adult cats with very furry feet, like Domestic Longhaired cats and Maine Coon cats are also at risk. One of the Maine Coon cats in my home has ‘bright’ spots on x-rays of her intestines. Her vet believes these are lumps of clumping litter.)
The same factors that allow clumping litter to ‘clump’ also cause it to form a clay ‘crust’ on any damp surfaces, like areas around water bowls in kennels. This coating is very difficult to remove, and takes staff and volunteers additional time in cleaning kennels. Regular, non-clumping litter does not tend to form this crusty coating on kennel surfaces, and is easier to sweep and clean up.
One other aspect of clumping litter is the very perfect tiny spheres it is made of. We have found that these particles bounce and roll for long distances if tossed out by cats that are enthusiastic about ‘covering’ in the litterbox. Kittens are often very vigorous and playful about digging in their litter, so this is especially a factor in kitten season. On a few occasions when only regular litter was available, scattered litter was much less obvious
At home I use a mixture of about 1/3 scooping litter and 2/3 regular litter. This mix still ‘clumps’ lightly, but doesn’t track and scatter like 100% scooping litter does. When litterboxes are filled with the mixture and then shaken lightly from side to side, larger (non-scooping) granules rise to the surface. This practice keeps kittens safer from the hazards of clumping litter, and would still allow for easy removal of ‘clumps’ when volunteers clean litterboxes..
So, my preference would be for EITHER a mix of scooping and regular litters, with the majority being regular litter OR regular, non-scooping litter alone. Switching would save time and money, keep messy litter crusting and scattering under control and be safer for the kittens we will have in shelters soon.