Zeolite for Slurry Nitrogen Retention & Liquid Manure Fertilizer Value

Q: How does adding zeolite to slurry preserve nitrogen?

Most nitrogen loss in manure slurry occurs when ammonium (NH4+) volatilizes as ammonia (NH3) gas. With its negatively charged framework and a cation-exchange capacity of CEC 1.6-2.0 meq/g, natural clinoptilolite temporarily captures the ammonium cations in the slurry within its internal crystal channels, lowering the free ammonium concentration in the liquid phase and the equilibrium ammonia partial pressure. This cation exchange reduces the driving force for volatilization, holding nitrogen in the slurry for longer. Lefcourt & Meisinger (2001) reported changes in ammonia volatilization and chemical composition when zeolite was added to dairy slurry.

Q: Ammonia is a gas with a basic nature, so is it really captured by cation exchange?

This is a common misconception. The nitrogen in slurry exists not as gaseous ammonia (NH3) but, in the dissolved state, mostly as the ammonium cation (NH4+), and it is this ammonium cation that clinoptilolite captures. Because the negatively charged framework exchanges and adsorbs the NH4+ cation, the cation-exchange logic holds precisely. However, when slurry pH rises above 8.5, the equilibrium shifts toward NH3 and the proportion of the gaseous form that cannot be captured by cation exchange increases, so pH management and rapid mixing govern the effectiveness.

Q: How much, and at what particle size, should be added per ton of slurry?

Field trials typically examine a range of 1-10% of the dry weight of slurry or manure, and for storage tank and pit applications a level of around 1-5% is usually tested first. To disperse rapidly in the liquid phase and secure exchange surface area, 100-mesh powder is advantageous, while 14x40 mesh granules are used for surface application on bedding and solid manure. Because dosage and particle size depend on the slurry's solids content, pH, and agitation conditions, it is advisable to confirm the residual NH4-N ratio with a small-scale pilot before scaling up.

Q: Does liquid manure mixed with zeolite have a higher fertilizer value?

By retaining more of the ammoniacal nitrogen that would otherwise be lost to volatilization within the slurry, the amount of nitrogen available to crops at application increases, which works to improve the fertilizer value (nitrogen value) of the same slurry. The captured ammonium can be slowly exchanged and released in the soil, showing slow-release behavior, and the zeolite itself also remains as a soil conditioner. However, since the actual yield increase and nitrogen use efficiency (NUE) effects vary by soil, crop, and application method, it is appropriate to verify them together with a fertilizer recommendation in an integrated crop-livestock liquid manure program.

Q: Is certification documentation available?

KMIZEOLITE holds numerous certifications, including OMRI Listed (KMI-10365), FDA GRAS (general use, 21 CFR 182.2729), TSCA compliance, and EN-71-3 PASS. For uses that add zeolite to manure and liquid manure to be returned to the soil, OMRI Listed status is important from the standpoint of suitability for organic livestock and eco-friendly integrated crop-livestock cycles, so please check it on the certifications page.

The Core Problem: Slurry Nitrogen Leaks Out as Ammonia During Storage and Application

Pig and cattle slurry (liquid manure) is itself an excellent nitrogen resource, but it is difficult to manage because a substantial portion of the nitrogen exists as ammoniacal nitrogen (NH4-N). In slurry collected in storage tanks and pits, organic nitrogen is continuously converted to ammonium by microbial breakdown, and the ammonium (NH4+) in the liquid phase is partly converted, according to equilibrium, into ammonia (NH3) gas that volatilizes into the atmosphere. This volatilization causes two losses at once. First, the nitrogen that crops would use disappears, so the fertilizer value of the liquid manure declines; second, the escaping ammonia becomes an odor and air-quality burden.

In particular, the higher the slurry pH rises, the more the equilibrium tilts toward NH3 and the faster volatilization accelerates. Korean-style swine slurry pits, with long storage periods and frequent agitation and transfer, and the time between surface application and soil infiltration, are the segments where nitrogen leaks out the most. To properly use liquid manure as a fertilizer in integrated crop-livestock cycles, a retention strategy that captures this ammoniacal nitrogen before it volatilizes is needed.

Why Clinoptilolite: The Precise Principle of Ammonium Cation Exchange

Natural clinoptilolite is examined for slurry nitrogen retention because of the mineral's negatively charged framework. As aluminum substitutes for silicon sites, the crystal framework carries a net negative charge, and to offset this charge it holds exchangeable cations (Na+, K+, Ca2+, etc.) within its channels. When added to slurry, these sites exchange with the ammonium (NH4+) cation, drawing free ammonium into the crystal channels. As a result, the concentration of free NH4+ in the liquid phase falls, the NH4+ ⇌ NH3 equilibrium is pulled back toward the liquid phase, and the driving force for volatilization as NH3 decreases. In other words, holding nitrogen in the slurry for longer is the key mechanism.

The important point here is that what is captured is not gaseous ammonia but dissolved ammonium, a cation. This action is therefore explained precisely by cation-exchange logic, not anion adsorption. However, once slurry pH exceeds 8.5, the equilibrium shifts strongly toward gaseous NH3 and the proportion not captured by cation exchange increases, so to see an effect, rapid mixing and suppression of excessive pH rise must go together.

Quantitative evidence has also accumulated. Reported values for the ammonium/ammonia retention capacity of clinoptilolite vary by source, but recent comprehensive reviews summarize an ammonium adsorption capacity of 2.97-4.6 mg/g for natural clinoptilolite, an ammonia removal efficiency of over 80% (>82.97%) under flow conditions, and cases of NH4 removal exceeding 98% under some conditions (Ozdemir & co-workers, Environmental Science and Pollution Research, 2024). Lebedynets et al. (2004), an aqueous-phase adsorption study, also reported that Transcarpathian clinoptilolite effectively exchanges and adsorbs ammonium (Lebedynets et al., Journal of Colloid and Interface Science, 2005). This adsorption capacity does not mean that the very high NH4-N concentration of the slurry itself is all absorbed at once; it is more accurate to understand it as a buffering role that lowers free ammonium in the liquid phase and pushes the equilibrium toward retention.

Among studies applied directly to livestock manure, Lefcourt & Meisinger (2001) measured ammonia volatilization and chemical-composition changes when alum or zeolite was added to dairy slurry and reported the potential for reduced volatilization (Lefcourt & Meisinger, Journal of Dairy Science, 2001), and at the composting stage it has likewise been reported that adding clinoptilolite contributes to manure nitrogen retention and reduced ammonia emissions (Awasthi et al., Agriculture, 2021).

KMIZEOLITE's natural clinoptilolite is 97% pure, mined and processed at the Amargosa Valley mine in Nevada, USA, with a cation-exchange capacity (CEC) of 1.6-2.0 meq/g, a specific surface area of 40.0 m²/g, a stable pH range of 3.0-10.0 (covering slurry pH fluctuations), and thermal stability to 700°C, making it suitable for manure and liquid manure treatment processes. General (non-ingestion) use, adding it to manure and returning it to the soil, falls under FDA 21 CFR 182.2729 (GRAS).

KMIZEOLITE Key Properties

Item	Value
Clinoptilolite purity	97%
Cation-exchange capacity (CEC)	1.6-2.0 meq/g
Specific surface area	40.0 m²/g
Pore diameter	4.0-7.0 Å
Stable pH range	3.0-10.0
Hardness	4.0-5.0 Mohs
Thermal stability	700°C
Specific gravity	1.89
Bulk density	45-54 lbs/ft³
Certifications	OMRI KMI-10365, FDA GRAS, TSCA, EN-71-3

Application Scenarios: Where to Add It, from Storage Tank to Application

Slurry nitrogen retention depends on "at which stage, at what particle size" the material is added. Below are the representative application points examined in integrated crop-livestock and liquid manure fields. Dosage is given as a percentage of the dry weight of slurry or manure; it is usually tested in the 1-10% range, with storage tank applications examined first at 1-5%.

Direct dosing into the slurry storage tank or pit: adding 100-mesh powder at about 1-5% of the slurry dry weight together with agitation to lower free ammonium and suppress volatilization during the storage period
Surface covering and application on manure: spreading 14x40 mesh granules over the surface of slurry or solid manure to partially capture the ammonia escaping from the surface layer
Mixing as a composting amendment: mixing clinoptilolite as a moisture- and ammonia-adsorbing amendment when composting solid manure, to support nitrogen retention and odor reduction at the same time (see Awasthi et al., 2021)
Barn bedding and floor-material application: laying 14x40 mesh granules on the floor to adsorb ammonia and moisture at the point where manure is generated, capturing nitrogen before it collects into the slurry
Pilot validation: applying a small amount to one storage tank or one application plot, comparing the residual NH4-N ratio and post-application crop response against a control, and then deciding on expanded adoption

Recommended Particle Size and Product Specifications

In slurry nitrogen retention, the key is to disperse rapidly in the liquid phase and secure exchange surface area, so Powder (100 mesh) is suitable for storage tank dosing and Medium Granule (14x40 mesh) is suitable for surface application on manure and bedding. Powder exchanges quickly but is hard to recover and separate, while granules are easy to handle as bedding and cover but exchange more slowly in the liquid phase. Refer to the table below to select the product family that fits your application point.

Product family	Mesh	Particle size	Typical use
Powder	100 mesh or finer	<150μm	Pozzolan, feed, powder adsorption
Fine Granule	30×50 mesh	0.3-0.6mm	Water treatment, filtration, soil
Medium Granule	14×40 mesh	0.4-1.4mm	Filter media, bedding, floor material
Coarse Granule	8×14 mesh	1.4-2.4mm	Swimming pools, de-icing, large filtration
Extra Coarse	4×8 mesh	2.4-4.8mm	Packed beds, air scrubbers

→ View products by mesh size · Product selection guide by use

Field Review Points: The Variables That Govern Effectiveness

When applying zeolite for slurry nitrogen retention, the following items should be checked together.

pH management: when slurry pH is 8.5 or above, the equilibrium shifts toward gaseous NH3 and cation-exchange efficiency drops. Rapid mixing and suppression of excessive alkalinization come first
Solids content and agitation conditions: the powder must be sufficiently dispersed in the liquid phase to secure exchange surface area. If solids content is high or agitation is weak, increase the dosage or adjust the dosing method
Quantitative dosage evaluation: in the 1-10% of dry weight range, measure the residual NH4-N ratio and total nitrogen (TN) retention against a control to judge cost-effectiveness (see the Lefcourt & Meisinger, 2001 approach)
Timing of application: design the dosing timing to match the segments where nitrogen leaks the most (late storage, just before and just after application)
Fertilizer-component analysis: since the retention effect must ultimately be verified by the crop-available nitrogen at application, analyze the nitrogen content of treated and untreated liquid manure and reflect it in the fertilizer recommendation
Certification check: to use it as eco-friendly and organic-livestock integrated crop-livestock liquid manure, confirm OMRI Listed (KMI-10365) suitability. Manure addition and soil-return uses fall under general GRAS (21 CFR 182.2729)

→ View TDS (Technical Data Sheet) · View MSDS (Safety Data Sheet)

Slurry Nitrogen Retention FAQ

How does adding zeolite to slurry preserve nitrogen?

Most nitrogen loss in manure slurry occurs when ammonium (NH4+) volatilizes as ammonia (NH3) gas. With its negatively charged framework and a cation-exchange capacity of CEC 1.6-2.0 meq/g, natural clinoptilolite temporarily captures the ammonium cations in the slurry within its internal crystal channels, lowering the free ammonium concentration in the liquid phase and the equilibrium ammonia partial pressure. This cation exchange reduces the driving force for volatilization, holding nitrogen in the slurry for longer. Lefcourt & Meisinger (2001) reported changes in ammonia volatilization and chemical composition when zeolite was added to dairy slurry.

Ammonia is a gas with a basic nature, so is it really captured by cation exchange?

This is a common misconception. The nitrogen in slurry exists not as gaseous ammonia (NH3) but, in the dissolved state, mostly as the ammonium cation (NH4+), and it is this ammonium cation that clinoptilolite captures. Because the negatively charged framework exchanges and adsorbs the NH4+ cation, the cation-exchange logic holds precisely. However, when slurry pH rises above 8.5, the equilibrium shifts toward NH3 and the proportion of the gaseous form that cannot be captured by cation exchange increases, so pH management and rapid mixing govern the effectiveness.

How much, and at what particle size, should be added per ton of slurry?

Field trials typically examine a range of 1-10% of the dry weight of slurry or manure, and for storage tank and pit applications a level of around 1-5% is usually tested first. To disperse rapidly in the liquid phase and secure exchange surface area, 100-mesh powder is advantageous, while 14x40 mesh granules are used for surface application on bedding and solid manure. Because dosage and particle size depend on the slurry's solids content, pH, and agitation conditions, it is advisable to confirm the residual NH4-N ratio with a small-scale pilot before scaling up. Refer to the product selection guide by use.

Does liquid manure mixed with zeolite have a higher fertilizer value?

By retaining more of the ammoniacal nitrogen that would otherwise be lost to volatilization within the slurry, the amount of nitrogen available to crops at application increases, which works to improve the fertilizer value (nitrogen value) of the same slurry. The captured ammonium can be slowly exchanged and released in the soil, showing slow-release behavior, and the zeolite itself also remains as a soil conditioner. However, since the actual yield increase and nitrogen use efficiency (NUE) effects vary by soil, crop, and application method, it is appropriate to verify them together with a fertilizer recommendation in an integrated crop-livestock liquid manure program.

Is certification documentation available?

KMIZEOLITE holds numerous certifications, including OMRI Listed (KMI-10365), FDA GRAS (general use, 21 CFR 182.2729), TSCA compliance, and EN-71-3 PASS. For uses that add zeolite to manure and liquid manure to be returned to the soil, OMRI Listed status is important from the standpoint of suitability for organic livestock and eco-friendly integrated crop-livestock cycles, so check it on the certifications page.

Inquiries and Sample Requests

If you are considering applying zeolite for slurry nitrogen retention and improving liquid manure fertilizer value, please reach out through the channels below.

Disclaimer

Whether the application is appropriate may vary depending on field conditions, regulations, and test results. Before actual application, a test review suited to the specific field conditions must always come first. Zeolite is not a cure-all for this field but should be understood as a material that supports existing manure and liquid manure management processes.

Slurry Nitrogen Retention & Improved Liquid Manure Fertilizer Value