How clumping cat litter is made
Clumping cat litter is altered volcanic ash, a clay that can swell to eight times its volume when wet.
- stations
- 7
- things upstream
- 17
- raw sources
- 10
- steps from the ground
- 6
The short version
Clumping litter is mostly bentonite, a clay formed when volcanic ash weathered in seawater. It is dug from strip mines, dried, crushed and formed into granules. Sodium bentonite swells and sticks together where urine lands, making a lump that can be scooped out. Calcium bentonite can be upgraded with a sodium salt, and some brands add baking soda against odor.
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Strip-mine the clay
Bentonite beds formed from volcanic ash that turned to clay underwater. High-grade sodium bentonite comes mostly from between the Black Hills of South Dakota and the Bighorn Basin of Wyoming, and from Turkey. Miners strip off the ground above and dig out the beds.
Goes in -
Dry the raw clay
Freshly dug clay is wet and sticky, so it is dried before grinding. Dry clay breaks cleanly instead of smearing.
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Crush and grind
Crushers break the clay lumps down, and mills grind them to a fine powder. One patented process grinds every particle to 2 mm or smaller.
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Swap in sodium
Calcium bentonite clumps poorly, so some plants stir in a soluble sodium salt such as sodium carbonate. Sodium trades places with calcium in the clay's layers, and the clay gains much of sodium bentonite's swelling power.
5 to 10% sodium salt
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Form the granules
The damp clay goes through a granulating machine that shapes it into round or cylindrical grains. Additives such as wood powder or diatomite can be blended in first to set the weight and whiteness.
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Kiln-dry the grains
Granules are dried until little water is left. Dry granules soak up urine quickly and clump firmly when it hits.
10% moisture or less
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Screen and blend
Screens pull out dust and oversized grains. Some brands mix in baking soda to absorb odors, or guar gum to strengthen the clumps, before the litter is bagged.
Goes in
Worth repeating
- Edward Lowe started selling clay in bags as Kitty Litter in 1947; before that, sand was the usual choice.
- Cat litter in the US uses about five billion pounds of mined clay a year.
- Clumping bentonite litter was developed in the US in 1984 by biochemist Thomas Nelson.
Back to the ground
Follow every input upstream and clay cat litter starts as these 10 raw sources.
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Sources
Cite this page: "How clumping cat litter is made." Assembly Line, 2026-11-03. https://assemblyline.org/make/cat-litter