Types of cat litter
Cat litter comes in many forms, and each has its own properties, do you go for ease of use, cost, or environmental impact?
Cats instinctively bury their waste, in the wild they do this in soft soil and it may be to help hide their presence from predators. In the home, the nearest equivalent to soil is the litter in your litter tray, and this is why cat's need little training to use a litter tray - they will use it instinctively.
There are many types of non-clumping and clumping litter made from a clay based medium such as fuller's earth or zeolite. Clay litters are very common and moderately priced. They can be dusty though and bits often get stuck between paws, spreading around the tray and house as the cat leaves (this is known as 'tracking') Clumping litters are better for maintenance - Any wet areas clump to form a solid mass which can easily be removed and solid waste also gets covered, making it less messy to remove. Clumping litters often contain a form of silica, but this is different to, and should not be confused with, silica gel litter
Soil, Earth, or Peat
As cats naturally use soil to do their toileting, why not just use soil in your litter tray? Using soil from the garden costs nothing and is far more environmentally friendly than using commercial cat litter which would have been mined, and transported at great environmental cost. You can simply dig out a hole of soil and when used bury the soil and waste back in. Although cheaper and environmentally friendly, most cat owners prefer the convenience of packaged litter. Another major downside of soil is that your cat is likely to leave muddy footprints around the tray, although a large mat does help.
Wood based cat litter pellets are much more eco-freindly
Paper or wood litter
Sawdust, paper or wood shavings can be used as cat litter in loose or pellet form and are relatively absorbent, environmentally friendly, and often contain natural deodorizing scents. There is often little tracking with these types of litter, although they can be higher maintenance. At first the litter is absorbent and will clump a little, but will then dry and break up, making it hard to distinguish between soiled and clean areas. These litters are often sold as 'biodegradable' or 'eco-friendly' since they are made from waste products and the soiled litter can be composted (but not solid wastes, which could be a health hazard)
Silica Gel litter
More expensive and less eco-friendly than paper, wood, or soil, silica gel is arguably the most absorbent and long-lived cat litter. Silica gel litters can absorb and seal away large amounts of moisture without releasing much odour, leaving just the solid wastes to be removed. There is no dust with silica gel and as long as the solid waste is removed daily and the remaining litter stirred, it can easily last for a couple of weeks.
Most cat litter is made from natural clay and may be given a wide variety of names including Fullers Earth, Diatomaceous Earth, or Sodium Bentonite. The clay is not a by-product and is specifically mined, usually through a very destructive process known as strip-mining where the top layers of soil over vast areas are stripped away. If you have an environmental conscience you may wish to use a more eco friendly litter such as wood based, garden soil, or silica gel.
Choosing a litter
If you want to try out different cat litters you should make any change gradual to see how your cat reacts. If your cat is new you should continue to use the litter it is used to for at least a month, when your cat is settled you can start trying new litters. First try adding some of the new litter in with the old and gradually increase the amount of new litter. You should settle on a litter which is suitable for both you and your cat.