Litter Box Mat & Bottom Tray Deodorizing Filler — Fine-Grained Clinoptilolite That Captures the Ammonia from Leaked Urine

In a cat litter box, the most stubborn odor point is not on top of the litter but beneath it. Urine that passes through the litter layer, or runs off the edges before clumping, pools in the lower compartment of a dual tray, the litter base mat, and the gaps at the tray bottom, where it stagnates without ventilation. The ammonia generated as this stagnant urine decomposes is the main culprit behind the lingering odor that persists even after you clean the box.

This page covers the use as a filler placed beneath the litter layer and in mat pockets, distinct from an additive mixed directly into the litter (zeolite for cat litter additive). KMI natural clinoptilolite (97.0% purity) is considered as a bottom-deodorizing-layer raw material that catches the leaked urine and traps ammonium (NH₄⁺) right where it is.

Why the bottom tray and mat need a separate deodorizing layer

A litter additive reduces the surface odor right after elimination, but it cannot reach urine that has passed down through the litter. Urine pooled at the bottom becomes a blind spot in odor management for the following reasons.

• The dual-tray bottom and mat pockets have almost no ventilation, trapping ammonia
• The litter-replacement cycle differs from the bottom-cleaning cycle, so urine residue accumulates
• Urine that leaks out before clumping bypasses the litter's deodorizing function
• Urine absorbed into the tray bottom and mat fibers smells again upon re-wetting, even after drying

Therefore, the design intent of this use is to place a mineral layer that captures ammonium not on top of the litter but at the bottom point where the urine actually pools.

Ammonium adsorption mechanism and quantitative basis

The urea in cat urine is broken down by urease to form ammonia, which in a moist environment becomes protonated and exists as the ammonium ion (NH₄⁺). Clinoptilolite has a negatively charged framework whose charge is compensated by exchangeable cations such as K⁺, Na⁺ and Ca²⁺, giving it high selectivity for the cation NH₄⁺. At the same time, its 4.0-7.0 Å pores physisorb ammonia and amine gases, so ion exchange and adsorption work together.

What matters most for a bottom-filler application is the removal efficiency as a function of particle size and treatment mode. Mažeikiene et al. (2008, Journal of Environmental Engineering and Landscape Management) treated aqueous ammonium with fine-grained 0.315-0.63mm clinoptilolite and reported NH₄⁺ removal efficiencies of 72-86% under static mixing (batch) conditions and 95-99.9% under flow-through (filter) conditions where the medium is passed through, presenting a unit adsorption of about 5 mg NH₄/g under static conditions. This product's recommended particle size, 30×50 mesh (0.3-0.6mm), falls right within that experimental range, making it a meaningful reference for a mat structure where pooled urine passes through and contacts the filler.

The equilibrium and kinetics of aqueous ammonium adsorption were quantitatively characterized for Transcarpathian natural clinoptilolite by Lebedynets, Sprynskyy et al. (2004, Adsorption Science & Technology), and the structural background of ion exchange and cation selectivity is summarized in Ion Exchange in Natural Clinoptilolite (2022, Minerals). The adsorption of the odor gases themselves was addressed, including for natural clinoptilolite, by Cataldo et al. (2024, Materials).

Note: The quantitative values above are based on aqueous-solution experiments; the actual removal performance of a real mat or tray varies with urine concentration, contact time, filler thickness and breathable structure, and the conditions of use.

Safety data to check first

The bottom mat layer is placed beneath the litter, so direct contact is limited, but safety should be verified first on the premise that a cat may touch or lick it.

For reference, uses premised on animal feed intake apply the GRAS designation 21 CFR 582.2729, while general uses not premised on intake — such as this mat and tray filler — apply 21 CFR 182.2729.

Key properties for bottom-filler use

Chemical composition — the safe makeup of a natural mineral

The main components are a natural aluminosilicate based on silicon (Si) and aluminum (Al) — a safe mineral composition that contains no heavy metals or hazardous substances.

An honest limitation regarding anionic odor components

It is not accurate to describe zeolite deodorization as a cure-all for every odor. Unmodified clinoptilolite carries a negatively charged framework, so its adsorption of anions and oxyanions (phosphate, urate, and some sulfur-based anionic species) is inherently weak. Cation exchange is the mechanism for capturing the cation NH₄⁺, and the same logic cannot be applied directly to anion removal.

If anionic components such as phosphate or urate must be targeted, separate treatment such as metal (Ca, La, Fe, Al) ion-exchange modification or surfactant modification (SMZ, surfactant-modified zeolite) is essentially a prerequisite. What this mat and tray filler targets as a verified objective is strictly the cation ammonium (NH₄⁺), and since this ammonia is precisely the main cause of lingering cat-litter odor, its fitness for the application holds.

Recommended product specifications

How it can be applied

Zeolite is considered not as a standalone mat but as a raw material for the bottom deodorizing layer of a mat or tray structure, encapsulated and placed in position.

• Nonwoven-encapsulated deodorizing filler placed in the lower compartment of a dual tray
• A replaceable deodorizing cartridge inserted into the inner pocket of a litter base mat
• An ammonia-adsorbing reinforcement material for the absorbent layer of a step mat
• A blend raw material for pet-mat filler for OEM and white-label products

Points to review when applying

• Encapsulation method: urine contact volume and removal efficiency vary with nonwoven thickness and water permeability
• Fill thickness and area: the more it is arranged as flow-through (filter), the higher the efficiency versus static
• Replacement cycle: set the replacement interval before adsorption saturation to match the conditions of use
• Dust and feel: 30×50 mesh is the baseline, but verify dust and usability after encapsulation
• Drying and re-wetting: confirm odor behavior when dried filler is re-wetted

Related pages

• Zeolite for cat litter additive — surface deodorizing use mixed directly into the litter
• Pee pad deodorizer — ammonia management in the pad's absorbent layer
• Pet odor management — the whole pet environment
• Home & Pet application category — view the entire category

Items worth checking before inquiry

• Mat structure: dual-tray bottom / base mat pocket / step mat absorbent layer
• Objective: controlling lingering bottom odor / reinforcing absorption / making it a replaceable cartridge / OEM development
• Desired particle size (30×50 or 14×40) and packaging unit
• Encapsulation material (nonwoven fabric, etc.) and expected replacement cycle

Frequently Asked Questions (FAQ)

How is a litter box mat / bottom tray filler different from a litter additive?

A direct litter-mix additive blends zeolite into the litter itself to reduce odor right after elimination, whereas the bottom mat / tray filler on this page is placed beneath the litter layer (the lower compartment of a dual tray, the inner pocket of a litter mat, the base mat) to catch and trap urine that passes through the litter or leaks out the edges. The key is capturing, at that point, the ammonia generated as the leaked urine stagnates; because it is not mixed directly with the litter, it does not affect clumping performance.

How does zeolite capture the ammonia from leaked urine?

The ammonia produced as cat urine decomposes becomes protonated and exists as ammonium (NH₄⁺). Natural clinoptilolite, with a cation exchange capacity of CEC 1.6-2.0 meq/g, traps this NH₄⁺ by exchanging it with the framework's K⁺, Na⁺ and Ca²⁺, while its 4.0-7.0 Å pores simultaneously physisorb ammonia and amine gases. Mažeikiene et al. (2008) reported that fine-grained 0.315-0.63mm clinoptilolite removed aqueous ammonium by 72-86% under static conditions and 95-99.9% under flow-through (filter) conditions, and this product's 30×50 mesh (0.3-0.6mm) falls within that particle-size range.

Are anionic odor components such as phosphate and uric acid also adsorbed?

No. Unmodified clinoptilolite carries a negatively charged framework, so its adsorption of anions and oxyanions (phosphate, urate, etc.) is inherently weak. Targeting such components essentially requires separate treatment such as metal (Ca, La, Fe, Al) ion-exchange modification or surfactant modification (SMZ). The verified target of this mat filler is strictly the cation ammonium (NH₄⁺); anion removal cannot be explained by cation-exchange logic.

Is it safe even if a cat touches or licks the mat filler?

KMI natural clinoptilolite (97.0% purity) holds EN-71-3 (European toy safety standard) PASS, USFDA GRAS (21 CFR 182.2729; 582.2729 for dietary-intake use), California Prop 65 compliance, and TSCA compliance. The granular form, with a hardness of 4.0-5.0 Mohs, does not break easily, keeping dust low, and the bottom mat layer is placed beneath the litter so direct contact is also limited. Still, we recommend validating the final mat product for usability, including nonwoven encapsulation, breathable structure and dust.

Notes

Zeolite can be considered as an auxiliary raw material for ammonia deodorization and moisture adsorption in cat litter box mats and bottom trays, but the final product performance varies with the mat structure, encapsulation method, fill thickness, urine contact volume, replacement cycle, and conditions of use. The quantitative values cited in the text are based on aqueous-solution experiments, so before actual commercialization it is advisable to run blending and encapsulation tests alongside usability reviews.

[Inquire about samples and OEM of zeolite filler for cat litter box mats and bottom trays →]