Category: organic fertilizer equipment

Functional/specialty fertilizers are a category of fertilizers that combine nutrient supply with specific physiological functions. Their core is based on macro- and micro-elements like nitrogen, phosphorus, and potassium, with the addition of functional components such as humic acid, seaweed extract, biochar, and silicon, or modified using special processes like magnetization and activation. This achieves the dual goals of “fertilization + solving specific production problems,” meeting the needs of modern agriculture for enhancing crop resistance, improving soil quality, and optimizing agricultural product quality.

Core Categories and Mechanisms of Action

The function of functional/specialty fertilizers is strongly correlated with their added core components. Different categories address different production pain points. Common types include:

Humic Acid-Containing Fertilizers

Core Components: Humic acid (mainly fulvic acid and brown humic acid) extracted from peat, lignite, and weathered coal.

Dual Functions

Nutrient Supply: Can be combined with nitrogen, phosphorus, and potassium to create humic acid compound fertilizer, providing essential nutrients for crop growth.

Soil Improvement + Growth Stimulation: The functional groups of humic acid can adsorb heavy metal ions in the soil, reducing the risk of soil pollution; it also promotes the formation of soil aggregates, improving soil permeability and water and fertilizer retention capacity; and it stimulates root cell division, enhancing root absorption capacity and strengthening crop drought and cold resistance.

Applicable Scenarios: Improvement of saline-alkali land and compacted soil; base fertilizer or top dressing for field crops and fruit trees.

Contains Alginic Acid Fertilizer

Core Ingredients: Natural bioactive substances (algal polysaccharides, amino acids, cytokinins, etc.) extracted from seaweed such as kelp and algae. Dual Functions

Nutrient Supply: Seaweed itself contains nitrogen, phosphorus, potassium, and trace elements such as zinc and boron, which can directly supplement crops with nutrients.

Stress Resistance and Yield Promotion + Quality Improvement: The bioactive substances in alginic acid can activate the crop’s own defense system, enhancing resistance to pests and diseases, lodging resistance; promoting fruit enlargement and coloring, increasing fruit sugar and vitamin content, and improving the flavor of agricultural products.

Applicable Scenarios: Foliar spraying or fertigation for cash crops such as fruits, vegetables, and flowers; restorative fertilization during periods of crop stress (drought, low temperature).

Silicon Fertilizer

Core Components: Soluble silicon compounds such as monosilicic acid, potassium silicate, and calcium silicate (distinct from the insoluble silicon in traditional silicon ores).

Dual Functions

Nutrient Supply: Silicon is a “beneficial element” for crops (especially important for silicon-loving crops like rice, wheat, and sugarcane), participating in cell wall synthesis;

Stress and Disease Resistance + Lodging Resistance: Silicon deposits in crop epidermal cells, forming hard “silicified cells,” enhancing stem toughness and reducing the risk of lodging; it also blocks pathogen invasion, reducing the occurrence of diseases such as rice blast and wheat powdery mildew; and it can reduce fruit deformities and cracking rates in fruits and vegetables.

Applicable Scenarios: Rice, wheat, corn, and other gramineous crops; cucumbers, tomatoes, and other greenhouse vegetables.

Biochar-Based Fertilizer

Core Components: Biochar, produced by high-temperature pyrolysis of biomass (straw, sawdust, livestock manure, etc.) under anaerobic conditions, combined with organic or chemical fertilizers.

Dual Functions

Nutrient Supply: Biochar’s pores adsorb and fix nutrients such as nitrogen, phosphorus, and potassium, slowly releasing them for crop absorption.

Carbon Fixation and Soil Improvement + Fertilizer Retention and Efficiency Enhancement: Biochar’s porous structure improves soil permeability, adsorbs soil salts, and alleviates secondary salinization in greenhouse agriculture soils; it also fixes atmospheric carbon, achieving “carbon sequestration and emission reduction”; and promotes the reproduction of beneficial soil microorganisms, improving soil fertility.

Applicable Scenarios: Soil improvement in greenhouses; fertility enhancement in barren and sandy soils.

Magnetized Fertilizer

Core Technology: Ordinary fertilizers (urea, compound fertilizer) are magnetized using a magnetization device.

Dual Functions

Nutrient Supply: Retains the original fertilizer’s nutrient content, meeting the basic needs of crops.

Nutrient Activation + Enhanced Absorption: The magnetic field alters the form of nutrients in the soil, converting insoluble phosphorus and potassium into soluble forms; it also stimulates root enzyme activity, accelerating nutrient absorption and improving fertilizer utilization.

Applicable Scenarios: Base fertilizer for field crops; areas with severe soil nutrient fixation.

Core Advantages

Multiple Effects in One Application, Solving Specific Production Pain Points

Unlike ordinary fertilizers that only provide nutrients, functional fertilizers can simultaneously achieve “nutrient supplementation + soil improvement + stress resistance + quality improvement and yield increase.” For example, humic acid compound fertilizer can both fertilize and improve compacted soil, saving the cost of applying soil conditioners separately.

Enhancing Crop Stress Resistance and Reducing Pesticide Use

Silicon fertilizers, seaweed extract fertilizers, etc., can enhance the crop’s own disease and stress resistance, reduce the incidence of pests and diseases, and reduce the use of chemical pesticides, aligning with the development direction of green agriculture.

Adapting to Precision Planting Needs

Customized functions for different crops and different soil problems. For example, biochar-based fertilizers are used in greenhouses to improve saline-alkali soils, and seaweed extract fertilizers are used in fruit and vegetable cultivation to improve fruit quality, meeting the differentiated planting needs of modern agriculture.

III. Precautions for Use

Targeted Selection, Avoid Blind Application

Fertilizers should be selected based on soil conditions and crop needs. For example, humic acid fertilizers are preferred for saline-alkali soils, while silicon fertilizers are preferred for paddy fields. Do not blindly pursue “multi-functionality” while neglecting targeted application.

Use in conjunction with conventional fertilizers

Most functional fertilizers have lower levels of macronutrients than ordinary compound fertilizers and must be used in conjunction with conventional fertilizers to meet the nutrient needs of crops throughout their entire growth cycle.

Strictly control the application dosage

Excessive application of some functional ingredients (such as humic acid) can lead to soil microbial imbalance. Follow the dosage instructions on the product packaging to avoid adverse effects.

Conclusion: Integrating Functional Fertilizers into Modern Agriculture

In summary, functional/specialty fertilizers represent a significant advancement in agricultural inputs, moving beyond mere nutrient supply to address specific challenges like soil degradation, crop stress, and quality optimization. Their targeted application—whether humic acid for saline soils or silicon for gramineous crops—enables precise, sustainable crop management.

To fully leverage these advanced formulations, professional fertilizer production machine technology is essential. For instance, a versatile NPK fertilizer production line can be adapted to incorporate functional additives. Critical equipment includes:

• Disc granulatorsor double roller press granulators for shaping uniform, high-integrity granules that encapsulate both macro-elements and functional components.
• NPK blending machinesfor homogeneously mixing base nutrients with additives like biochar or seaweed extract.
• Specialized lines, such as a bio organic fertilizer production linefor humic-acid or biochar-based products, often integrated with windrow composting machines for pre-treatment of organic matter.

Choosing the correct fertilizer granulation processes ensures product stability and efficacy. A roller press granulator production line is ideal for moisture-sensitive materials, while a disc granulator for shaping offers flexibility for organic-inorganic blends.

Ultimately, the synergy between innovative functional fertilizers and professional fertilizer manufacturing equipment paves the way for more resilient, efficient, and sustainable farming systems. By selecting the right fertilizer type and employing precise manufacturing technology, producers can deliver solutions that truly meet the dual goals of nourishment and problem-solving in modern agriculture.

Sulfur-coated urea (SCU) is a matrix-based composite controlled-release fertilizer. Its core feature is a thin film of sulfur coated on the surface of urea granules. Some products also have an additional wax or resin sealing layer. By controlling the decomposition rate of the coating, nitrogen release is slowed down, while simultaneously supplementing crops with essential sulfur. It possesses the dual functions of “nitrogen control and sulfur supply,” making it a commonly used low-cost slow-release fertilizer for field crops and cash crops.

I. Core Preparation Process

The core of sulfur-coated urea production is precise coating spraying technology. Strict control of temperature and spraying rate is required to ensure uniform coating thickness. The specific process is as follows:

Urea Pretreatment:Urea granules with uniform particle size are preheated to a specific temperature to enhance the adhesion between the granules and molten sulfur.

Molten Spraying:Sulfur is heated to a molten state and evenly sprayed onto the surface of the preheated urea granules in a rotating drum. Depending on the product’s release cycle requirements, an additional layer of wax or resin can be sprayed as a sealing layer to improve coating stability.

Cooling and Shaping: After spraying, the granules cool and solidify, forming a two- or three-layer structure of “urea core + sulfur coating (optional wax/resin sealing layer)”.

Thickness Control: The coating thickness is controlled by adjusting the sulfur melting temperature, spraying rate, and roller speed—a thin coating corresponds to rapid release (suitable for short-term growing crops), while a thick coating corresponds to long-term release (suitable for perennial crops or field basal fertilizer).

II. Nutrient Release Mechanism: The release of nitrogen and sulfur from sulfur-coated urea relies on the natural decomposition process in the soil environment. The release process is highly compatible with the crop’s nutrient requirements and consists of two simultaneous stages:

Coating Decomposition Stage: Water vapor in the soil permeates the coating, while soil microorganisms (such as sulfur-oxidizing bacteria) gradually decompose the sulfur coating. If a wax/resin sealing layer is present, it will first break down under microbial or physical action, initiating the decomposition of the sulfur layer.

Nutrient Release Stages

Nitrogen Release: As the coating develops pores, soil moisture enters the granules, dissolving the urea. Nitrogen slowly diffuses into the soil through these pores, with a release cycle controllable within 8-12 weeks, avoiding the problem of “one-time release and massive loss” common with ordinary urea.

Sulfur Release: Decomposed sulfur is converted into sulfate, which is absorbed and utilized by crops. Sulfur is a key medium-element for protein synthesis and enzyme activity activation, promoting crop metabolism and improving the quality of agricultural products.

III. Core Advantages

Extended Nitrogen Supply Cycle, Improved Utilization Rate

Ordinary urea releases a large amount of nitrogen within 1-2 weeks after application, with a utilization rate of only 30%-40%. Sulfur-coated urea releases nitrogen slowly, increasing the utilization rate to over 50%, reducing nitrogen loss due to leaching and volatilization, and continuously supplying the crop’s needs throughout its entire growth period.

Dual-purpose fertilizer, supplementing sulfur

Unlike polymer-coated controlled-release fertilizers, sulfur-coated urea’s coating itself is a sulfur source, effectively addressing sulfur deficiency-related issues such as leaf yellowing and weakened growth in crops. It is particularly suitable for sulfur-deficient soils (such as sandy soils and fields where sulfur-required crops are grown long-term).

Reduced fertilization costs, saving labor and time

The long-lasting nitrogen release allows for single-application as base fertilizer, eliminating the need for multiple topdressings. This significantly reduces labor and fuel inputs, meeting the needs of large-scale mechanized planting of field crops such as wheat, corn, and cotton.

Environmentally friendly, meeting regulatory requirements

The slow-release nitrogen minimizes farmland runoff pollution and ammonia volatilization, reducing the impact on eutrophication of water bodies and the atmospheric environment, aligning with agricultural policies aimed at reducing fertilizer use and increasing efficiency.

IV. Production and Quality Control Key Points

Key control parameters: During production, precise control of the sulfur melting temperature (ensuring complete melting without decomposition), spray uniformity (avoiding excessively thick or thin coatings in certain areas), and cooling rate (preventing coating cracking) is crucial.

Customized Release Curves: By adjusting the coating thickness and sealing layer type, different nutrient release curves can be customized. For example, thin-coated products are suitable for topdressing crops, while thick-coated products are suitable for base fertilizer of perennial crops such as fruit trees and seedlings.

V. Precautions for Use

Impact of Soil Acidity: Long-term, large-scale application of sulfur-coated urea will lower the soil pH due to the decomposition of sulfates, leading to soil acidification. It is recommended to use it in acidic soils in conjunction with alkaline materials such as quicklime or wood ash, or to alternate it with alkaline fertilizers to maintain soil acid-base balance.

Application Method: Trench or hole application is required; avoid surface spreading—high temperature and drought on the surface will accelerate coating damage and impair the controlled-release effect. Also, do not crush it before use, otherwise the coating structure will be destroyed, and the controlled-release function will be lost.

Suitable Crops: Prioritized for field crops such as wheat, corn, and rice, as well as crops with high nitrogen requirements and sulfur needs such as fruit trees and lawns. Not suitable for aquatic crops (such as lotus root), as rapid decomposition of the coating will lead to nitrogen loss.

Conclusion: Integrating SCU into Modern Fertilizer Production Systems

In conclusion, sulfur-coated urea represents a significant advancement in controlled-release fertilizer technology, offering an economical solution for sustainable nutrient management. Its successful npk fertilizer manufacturing process can be integrated into broader npk fertilizer production lines to create specialized formulations. While SCU production primarily employs drum coating, other key technologies like the double roller press granulator are essential in modern npk fertilizer production technology. For NPK compound fertilizers, dry granulation processes using a fertilizer roller press machine offer an alternative for heat-sensitive materials, with the npk bulk blending machine enabling precise nutrient ratio customization.

The scalability of SCU production complements the high NPK compound fertilizer production capacity demanded by global agriculture. When evaluating the NPK fertilizer production price, the long-term agronomic benefits and reduced environmental impact of controlled-release products like SCU justify the investment. Ultimately, integrating SCU technology with npk fertilizer granulator machine equipment and npk granulation machine technology creates versatile production systems capable of manufacturing a spectrum of products—from specialized controlled-release fertilizers to blended NPK formulations—supporting efficient, precise, and sustainable agriculture worldwide.

Stabilized fertilizers are a type of modified fertilizer that regulates nutrient conversion processes by adding chemical inhibitors. The core principle is to incorporate urease inhibitors and/or nitrification inhibitors into ordinary fertilizers (mainly urea and nitrogen-containing compound fertilizers) to slow down the conversion rate of nitrogen in the soil, reducing nitrogen loss in the form of ammonia and nitrogen gas, thereby improving nitrogen fertilizer utilization. While both stabilized and controlled-release fertilizers are high-efficiency nitrogen fertilizers, their technical principles and application scenarios differ significantly.

I. Core Technical Principle: Mechanism of Action of Inhibitors

The core of stabilized fertilizers lies in the synergistic or individual action of two inhibitors to block key pathways of nitrogen loss. Their regulation targets enzyme and microbial activity in the soil, rather than physically blocking nutrient release like coated fertilizers.

Urease Inhibitors (Representative Ingredients: NBPT, NPPT)

Target: Inhibits the activity of urease in the soil.

Principle: When ordinary urea is applied to the soil, urease rapidly decomposes it into ammonia nitrogen, some of which volatilizes into the air, resulting in loss. Urease inhibitors bind to urease, reducing its decomposition efficiency, slowing down urea decomposition, prolonging the residence time of ammonia nitrogen in the soil, and reducing ammonia volatilization loss.

Suitable scenarios: Suitable for alkaline soils and surface application, significantly reducing the risk of ammonia volatilization causing leaf burn to crops and air pollution.

Nitrification inhibitors (representative components: DCD, CP, DMPP)

Target: Inhibits the activity of nitrifying bacteria in the soil.

Principle: Ammonia nitrogen (NH₄⁺) produced by urea decomposition is gradually converted into nitrate nitrogen (NO₃⁻) under the action of nitrifying bacteria. Nitrate nitrogen is easily lost with rainwater or irrigation water and can also be converted into nitrogen gas and released under the action of denitrifying bacteria. Nitrification inhibitors can inhibit the nitrification process, stabilizing nitrogen in the ammonia nitrogen form for a longer period of time. Ammonia nitrogen can be adsorbed by soil colloids and is not easily lost.

Suitable scenarios: Suitable for rainy areas and sandy soils, reducing nitrogen leaching loss.

The current mainstream stabilized fertilizers mostly employ a dual-inhibitor combination technology, combining urease inhibitors and nitrification inhibitors. This simultaneously blocks two pathways: “urea decomposition → ammonia volatilization” and “ammonia nitrogen nitrification → nitrate nitrogen loss,” resulting in superior nitrogen retention and a 20%-30% increase in nitrogen utilization compared to ordinary urea.

II. Core Advantages

Lower Cost and Simpler Process: The production of stabilized fertilizers does not require complex coating or chemical synthesis processes. Inhibitors are simply added during the mixing stage of ordinary fertilizer production. Production costs are significantly lower than polymer-coated controlled-release fertilizers, offering higher cost-effectiveness and making them more suitable for large-scale field application.

Less Nitrogen Loss and Higher Utilization: Effectively reduces nitrogen loss caused by ammonia volatilization and nitrification-denitrification. Nitrogen fertilizer utilization can be increased from 30%-40% with traditional urea to 50%-60%, approaching the level of some slow-release fertilizers.

Flexible application, suitable for field crops. It can be applied as a base fertilizer in one application or as a top dressing in multiple applications, without the structural damage caused by crushing like coated controlled-release fertilizers. It is especially suitable for field grain crops such as corn, wheat, and rice, meeting the needs of large-scale mechanized fertilization.

Environmentally friendly, reducing nitrogen loss and volatilization, lowering pollution to the atmosphere (ammonia pollution) and water bodies (eutrophication due to nitrate nitrogen leaching), aligning with the agricultural policy direction of reducing fertilizer use and increasing efficiency.

III. Product Types and Applicable Scenarios

Main Product Forms

Stable Urea: Urea with added urease inhibitors or dual inhibitors, the most basic stabilized fertilizer.

Stable Compound Fertilizer: Nitrogen-containing compound fertilizer with added dual inhibitors, balancing nitrogen, phosphorus, and potassium supply with nitrogen stability, such as stabilized NPK compound fertilizer.

Dual/Multi-Controlled Fertilizers: Fertilizers with two or more inhibitors added simultaneously, suitable for different soil and climate conditions.

Applicable Scenarios

Preferred for: Field crops (wheat, corn, rice), oil crops (soybeans, rapeseed). Significantly reduces fertilizer and labor costs during large-scale planting.

Suitable Soils: Alkaline soils (reduces ammonia volatilization), sandy soils (reduces nitrogen leaching), and farmland in rainy areas.

Unsuitable Scenarios: Aquatic crops (such as lotus root), and highly acidic soils (inhibitor effectiveness will be affected). IV. Key Differences Between Stable Fertilizers and Coated Slow-Release/Controlled-Release Fertilizers

The key differences between stable fertilizers and coated slow-release/controlled-release fertilizers lie in several aspects: The former relies on the technical principle of regulating nutrient transformation through chemical inhibitors, achieving fertilizer retention by slowing down the rate of nitrogen conversion, rather than directly controlling nutrient release. Its production cost is lower, approaching that of ordinary fertilizers, and its application method is flexible, suitable for both basal and topdressing applications. The fertilizer can also be crushed for use, making it more suitable for field crops such as wheat, corn, and rice. The latter, on the other hand, is based on the technical principle of physically coating to block nutrient release, controlling the dissolution and diffusion rate of nutrients through the coating. Its production cost is higher, 1.5-3 times that of ordinary fertilizers. It is recommended to apply it as a basal fertilizer in one application, avoiding crushing to prevent damage to the coating structure. It is more suitable for cash crops such as fruit trees, flowers, and greenhouse crops.

From Inhibitor Addition to Industrial Granulation

The manufacturing of stabilized NPK fertilizers integrates inhibitor technology into the established npk fertilizer manufacturing process. The process begins with precise formulation in a npk blending machine, where nitrogen sources, inhibitors, and other nutrients are uniformly mixed. This homogeneous blend then enters the core granulation stage of a complete npk fertilizer production line. Advanced npk granulation machine technology is applied here, using equipment such as a npk fertilizer granulator machine or a disc granulator machine to form the powder into durable, market-ready granules.

The efficiency and consistency of this npk fertilizer granulator machine equipment directly impact the NPK compound fertilizer production capacity and final product quality. This integration of chemical innovation (inhibitors) with precision mechanical engineering (npk fertilizer production technology) exemplifies modern fertilizer manufacturing. It enables the scalable production of high-efficiency, environmentally considerate fertilizers that provide field crops with stabilized nitrogen nutrition, enhancing nutrient use efficiency while supporting sustainable agricultural practices.

 Introduction: How is Good Fertilizer “Forged”?

In the field, we want nitrogen fertilizer to release slowly, nourishing crops persistently, rather than leaching or volatilizing quickly. Slow-release urea fertilizers are designed for this purpose. However, manufacturing high-quality slow-release urea granules is not a simple matter of mixing and pressing. It is more akin to a precise “culinary” process, where the raw material formulation is the recipe, and the granulation process is the heat and timing. A recent study delves into how adjusting two key “switches” in a disc granulator—binder concentration and granulation time—can precisely control the final “physical fitness” of fertilizer granules, thereby providing a scientific guide for producing more efficient and environmentally friendly slow-release urea.

I. The Core of the Study: Two Variables, Four Qualities

Imagine a rotating shallow pan where urea powder and a binder solution extracted from cassava starch are mixed and tumbled. The research team set up a clear comparative experiment: they fixed all other conditions like disc speed and inclination, and systematically changed only two factors: the concentration of the starch binder solution and the time the material spends tumbling in the pan for granulation.

They focused on these four “fitness” indicators that determine fertilizer quality:
1. Durability: Are the granules “tough” enough? Can they withstand collisions and friction during long-distance transport without turning into powder?
2. Density: Are the granules “fluffy” or “solid”? This affects the actual weight per bag of fertilizer, transportation costs, and application uniformity in the field.
3. Pelletizing Yield: How much raw material successfully turns into qualified granules? This directly impacts production efficiency and cost.
4. Water Absorption and Dispersion Time: Do the granules disintegrate quickly or release slowly upon contact with water? This is the core measure of their “slow-release” capability. We want them to dissolve like a slow-release candy, providing nutrients steadily in the soil.

II. Finding One: Binder Concentration—The “Glue” Matters

Cassava starch plays the role of “natural glue” here. The study found that the thickness of this “glue” has a decisive impact on granule quality.

When researchers increased the concentration of the starch solution, a positive chain reaction occurred: the granules’ water absorption, density, pelletizing yield, and durability all improved simultaneously. This is because a thicker starch solution forms a stronger, denser binding network around each urea particle. Just like using thicker glue for bonding, the adhesion is firmer, the structure is more compact, and the granules naturally become tougher, heavier, and have fewer internal pores.

More interestingly, granules made with higher concentration starch also “held on” longer in water. They disintegrated and released nutrients more slowly, which is the dream characteristic of slow-release fertilizers. Observations under an electron microscope showed that granules from the high-concentration group had surfaces like smooth, dense pebbles, while those from the low-concentration group had rough, porous surfaces, visually explaining the source of the performance difference.

III. Finding Two: Time—The Art of “Kneading”

Granulation time is like the kneading time when making dough. The study showed that extending the “kneading” time of the granules in the disc also led to comprehensive quality improvements.

Longer granulation time gives the powder more opportunities to collide, adhere, and round off. This results in more regular granule shapes and a more compact interior. Consequently, granule durability, density, and pelletizing yield all increased with time. Simultaneously, sufficient kneading allows the starch “glue” to distribute more evenly, forming a more complete coating. This not only slightly increases the granules’ water absorption capacity but, more importantly, extends their dispersion time in water, further optimizing the slow-release effect.

IV. Insights for Producers: How to “Customize on Demand”

This study turns complex processes into clear multiple-choice questions:

• If you want to produce high-end fertilizers with optimal controlled-release performance and superior storage/transport durability, the answer is: use a higher concentration of cassava starch binder and allow for a longer granulation time.

• If you need to strike a balance between production efficiency and cost to produce the most cost-effective product, you can utilize the data models derived from research to calculate the optimal combination of binder concentration and granulation time based on your specific requirements for granule density, strength, and release period.

It’s like mastering a precise “cooking” formula, allowing fertilizer producers to flexibly “customize” slow-release urea products with different specifications and performance according to market demand.

Optimizing Granulation: The Science Behind Consistent Fertilizer Pellets

The scientific study of binder concentration and granulation time directly applies to the core of npk fertilizer production technology. In a complete npk fertilizer production line, precise formulation using a npk blending machine ensures accurate nutrient ratios. The subsequent granulation stage, which is central to the npk fertilizer manufacturing process, leverages advanced npk granulation machine technology to transform this mix. The principles of optimizing binder properties and process timing are critical for equipment like a npk fertilizer granulator machine, whether it operates as a wet granulator or an alternative system like a fertilizer roller press machine for dry compaction.

Mastering these variables allows manufacturers to fine-tune the NPK compound fertilizer production capacity and the final product’s physical properties—such as density, strength, and dissolution rate. This level of control is essential for producing high-quality slow-release or controlled-release fertilizers. The integration of this scientific understanding into the operation of npk fertilizer granulator machine equipment demonstrates how empirical research translates into practical, scalable manufacturing excellence. It enables the production of consistent, “tailor-made” fertilizers that meet specific agronomic needs, enhancing nutrient use efficiency and supporting sustainable agricultural practices through precision engineering.

Conclusion

The power of science lies in transforming experience into quantifiable, replicable laws. This study on disc granulation process, through rigorous experimentation, reveals how two ordinary operational parameters—binder concentration and granulation time—act like levers to influence the final quality of slow-release urea granules. It not only provides a direct “operating manual” for fertilizer plants to optimize production but also brings us a step closer to the goal of producing more efficient, environmentally friendly, and intelligent “ideal fertilizers.” In the future, by exploring more “variables,” we can hope to design bespoke fertilizers, like precision instruments, perfectly tailored to the needs of every crop and every plot of soil.

In modern fertilizer production, granulation is a crucial process that converts powdered raw materials into uniform granules. The disc granulator and rotary drum granulator are two common types of equipment. Although they differ in design, they share similar basic requirements for raw materials. The selection and pretreatment of raw materials directly determine granulation efficiency, product quality, and equipment lifespan. When choosing between these two types of equipment, global fertilizer producers must pay special attention to particle size, moisture content, adhesiveness, and impurity control of raw materials to ensure stable and efficient production.
   

Core Common Requirements for Raw Materials

Whether using a disc granulator or a rotary drum granulator, raw materials must meet the following basic conditions:

First, the particle size of raw materials should be controlled within a fine range, generally recommended between 80 and 200 mesh (approximately 75–150 micrometers). Fine powdered materials provide a larger contact area between particles, facilitating stable bonding during granulation. Overly coarse particles (e.g., larger than 1 millimeter in diameter) or lumpy impurities can not only affect the uniformity of granules but may also cause equipment clogging or wear.

Second, the moisture content of raw materials is a critical factor for successful granulation. Typically, the base moisture content of raw materials should be maintained between 10% and 20%, with specific values varying depending on the type of fertilizer. If the moisture content is too low, granules may not form properly, requiring the addition of water or binders through the equipment’s spraying system. Excessive moisture, on the other hand, can lead to clumping and uneven granulation. Stable moisture content is essential for ensuring the strength and durability of the final granules.

Additionally, raw materials must possess a certain degree of natural adhesiveness or achieve the required bonding effect through the addition of binders. Completely non-adhesive inert powders (such as quartz sand) cannot be directly used for granulation. Commonly used binders include water, bentonite, starch, cellulose derivatives, and ammonium phosphate solutions. The choice of binder depends on the type of fertilizer: organic fertilizers often use bentonite, while compound fertilizers typically employ ammonium phosphate solutions.

Finally, the raw materials must not contain hard, sharp impurities such as metal fragments or stones. These impurities can not only scratch the inner walls of the equipment (especially the wear-resistant linings of discs and rollers), but may also damage transmission components and affect the normal operation of the equipment.

Types of Fertilizer Raw Materials Suitable for Use

Both disc granulators and rotary drum granulators are suitable for a variety of fertilizer raw materials, including organic fertilizers, inorganic fertilizers, and compound fertilizers.

Organic fertilizer raw materials primarily include decomposed and fermented livestock manure (such as chicken manure, cow manure), agricultural waste (such as straw powder, sawdust, rice husk powder, fungal residue, biogas residue, and distillers’ grains), and harmless-treated municipal sludge. These materials typically exhibit strong natural adhesiveness and generally do not require the addition of large amounts of binders during granulation. Forming is mainly achieved by controlling moisture content.

Inorganic fertilizer raw materials encompass nitrogen fertilizers (such as urea powder, ammonium chloride powder), phosphate fertilizers (such as superphosphate powder, monoammonium phosphate powder), and potassium fertilizers (such as potassium chloride powder, potassium sulfate powder). Compared to organic fertilizers, inorganic fertilizer raw materials have weaker adhesiveness and often require the addition of binders (such as water or ammonium phosphate solutions) for effective granulation.

Compound fertilizer raw materials are usually mixtures of organic and inorganic fertilizer powders, such as blends of urea, monoammonium phosphate, potassium chloride, and humic acid powder. Granulation of these materials requires precise adjustment of moisture content and binder dosage based on the mixing ratio to ensure granule strength and uniform nutrient distribution.

Differences in Raw Material Requirements Between the Two Types of Equipment

Although the two types of equipment share similar basic requirements for raw materials, there are subtle differences in their specific applications.

Disc granulators are better suited for processing raw materials with slightly higher viscosity and moisture content, such as well-rotted organic fertilizer. However, the moisture content of the raw materials should not exceed 22%, as excessive moisture will cause the raw materials to clump together on the inner wall of the disc, affecting the discharge efficiency.

Rotary drum granulators have broader adaptability to raw materials and can handle mixtures with moderate adhesiveness, such as compound fertilizer raw materials. However, rotary drum granulators require greater uniformity in particle size to avoid the deposition of coarse particles inside the drum. By adjusting the rotation speed and tilt angle of the drum, the granulator can adapt to raw materials with different adhesiveness, enhancing granulation flexibility.

Key Steps in Raw Material Pretreatment

To ensure smooth granulation, raw material pretreatment is crucial. First, lumpy raw materials (such as decomposed organic fertilizers or caked inorganic fertilizers) must be processed through crushing equipment to achieve the required particle size. Second, drying or conditioning should be performed based on the moisture content of the raw materials: drying is necessary if moisture content is too high, while a small amount of water or binder can be mixed in advance if moisture content is too low. Next, screening is used to remove coarse particles and impurities, ensuring uniform particle size. Finally, for multi-material formulations, thorough mixing is required to ensure even distribution of nutrients and adhesiveness.

In summary, the selection and pretreatment of raw materials are fundamental to successful fertilizer granulation. Global fertilizer producers should scientifically establish raw material standards and pretreatment processes based on their product characteristics and equipment types to achieve efficient and stable production.

Wet vs. Dry Granulation: Raw Material Pathways

The choice between a rotary drum granulator and a disc granulator for wet granulation is distinct from the technology used in dry fertilizer granules compaction. Both wet methods require careful raw material preparation regarding particle size and moisture. However, the npk manufacturing process often incorporates a third pathway: dry granulation. This method utilizes a fertilizer compaction machine or fertilizer compactor as the core of a roller press granulator production line, which bypasses the need for liquid binders and is suited for different raw material properties.

Similarly, in the organic fertilizer manufacturing process, composted material can be shaped using either wet granulation (e.g., in a disc granulation production line) or dry compaction, depending on the product specification. This diversity in fertilizer production machine technology—from rotary drums for wet agglomeration to roller presses for dry compaction—highlights that raw material suitability is not a single standard but varies according to the chosen granulation principle. Understanding these distinctions allows producers to select the optimal system for their specific raw materials and final product goals.

Introduction: Innovative Opportunities from Dual Challenges

The world faces two urgent challenges: how to manage the surging volume of spent lithium iron phosphate (LFP) power batteries, and how modern agriculture can more sustainably obtain key nutrients, especially phosphorus. Excitingly, cutting-edge recycling technology is connecting these two issues, opening a new “from wheels to soil” pathway for resource circulation. Transforming phosphorus recovered from spent LFP batteries into slow-release fertilizers not only provides a new economic driver for the battery recycling industry but also offers an innovative nutrient source for agricultural green transformation. This is not only a triumph of technology but also a perfect practice of the circular economy concept at the intersection of energy and agriculture.

I. Why Choose LFP Batteries? The Unique Advantage of Recycling Phosphate Fertilizers

Among various lithium-ion batteries, lithium iron phosphate (LFP) batteries have lower traditional recycling economic value due to their lack of expensive metals like cobalt and nickel. However, the chemical essence of their cathode material, LiFePO₄—a compound containing lithium, iron, phosphorus, and oxygen—offers a unique perspective for resource utilization. Phosphorus, as one of the three essential elements for plant growth, is a strategic resource for global food security. Traditional phosphate fertilizer production heavily relies on non-renewable phosphate rock and involves high energy consumption and pollution. Recovering phosphorus from spent LFP batteries is equivalent to opening a new, renewable phosphorus resource library in the urban “mine,” effectively alleviating dependence on natural phosphate rock and reducing the environmental footprint of mining.

II. Technical Core: How to “Release” Phosphorus Nutrients from Batteries?

The technical core of this process is converting phosphorus in LFP cathode materials into a form usable by plants. Latest research reveals several efficient and green technological pathways.

1. Selective Extraction and Transformation

Researchers have developed an in-situ advanced oxidative metallurgy technique based on the Fenton reaction. This technology uses highly oxidative hydroxyl radicals (•OH) to selectively oxidize ferrous iron (Fe²⁺) in LiFePO₄ and promote the complete release of lithium ions (Li⁺), while the phosphate group (PO₄³⁻) framework within the olivine crystal structure is preserved, forming amorphous or crystalline iron phosphate (FePO₄). The key to this process is precise reaction control to retain phosphorus in the solid product, preventing its loss or pollution by entering the solution. Subsequently, these phosphorus-rich intermediates can be further processed, for example, combined with potassium and nitrogen sources to prepare slow-release PK or compound fertilizers with different formulations.

2. Direct Functionalization and Material Design

Besides serving as a phosphorus source, recycled lithium iron phosphate (LFP) materials, due to their unique structure and chemical properties, can be directly designed into fertilizers or soil conditioners with special functions. For example, micronizing blocky LFP materials using technologies such as laser crushing can increase their specific surface area. The iron and phosphorus species on their surface can form active sites; studies have shown that these substances can not only act as catalysts for water electrolysis but also regulate the release rate of nutrients in the soil or engage in beneficial interactions with soil microorganisms. This “material-level” recycling upgrade endows waste batteries with functional attributes far exceeding their elemental value.

III. Product Advantages: How Do Slow-Release Fertilizers Benefit Agriculture?

Phosphate fertilizer products derived from LFP are not simple substitutes for traditional fertilizers; they may possess a range of enhanced properties:

· Slow-Release Features: LFP itself or derived iron phosphate compounds have low solubility in water, which aligns perfectly with the core requirement of slow-release fertilizers. Phosphorus can be slowly released through the action of soil moisture, microbial activity, or weak acids secreted by roots, avoiding the issue of rapid fixation or loss after a single application and significantly improving phosphorus use efficiency.

· Nutrient Synergy: In addition to phosphorus, the products typically contain iron. Iron is a mesonutrient required for plant chlorophyll synthesis and is beneficial for correcting iron-deficiency chlorosis. Lithium, in trace amounts, is also considered by some studies to potentially promote growth in certain crops.

· Environmental Friendliness: This process transforms toxic waste (spent batteries) into an environmentally friendly product (fertilizer). Compared to the acidic wastewater generated by traditional hydrometallurgical phosphorus recovery, the new conversion routes lean toward greener chemical processes with a lower environmental burden.

IV. Closed-Loop System: Building a Battery-Agriculture Circular Economy

This technology paints a complete picture of a circular economy: after years of powering electric vehicles, lithium iron phosphate batteries are retired and enter a recycling system; recycling plants not only extract valuable lithium but also convert phosphorus-rich cathode materials into slow-release fertilizers needed for agriculture; these fertilizers are used in the fields to promote crop growth, thereby producing food or biomass energy. Ultimately, this closed-loop system reduces mining demand, lowers environmental risks, and creates shared sustainable value for two key industries: new energy and agriculture.

Realizing this vision requires cross-sector collaboration: battery designers need to consider “design for recycling” to simplify subsequent separation; recycling technologies must balance efficiency, cost, and product purity; agronomists need to evaluate the actual performance and long-term impact of these new fertilizers in different soil and crop systems.

V. Challenges and Future Outlook

Despite the promising prospects, this path still faces challenges. First, it is crucial to ensure that the final fertilizer product is free of toxic impurities such as heavy metals (e.g., copper and aluminum that may have been introduced from other battery components). This relies on efficient and precise battery dismantling and pretreatment technologies. Second, the economic feasibility of large-scale production needs further validation, balancing collection and logistics costs, processing costs, and the market price of the final fertilizer. Finally, appropriate product standards and regulatory frameworks must be established to ensure the safety and effectiveness of these new fertilizers are scientifically verified.

Looking ahead, with the influx of spent lithium iron phosphate batteries and the growing demand for sustainable agriculture, the resource recycling pathway from spent batteries to slow-release fertilizers will attract increasing R&D and investment. This represents a profound paradigm shift: waste is no longer the end point, but the beginning of another valuable life cycle. Through technological innovation, we can not only solve the e-waste problem but also open up a new, circular, and renewable nutrient pathway to nourish our land.

From Battery Recycling to Precision Fertilizer Manufacturing

The upcycling of lithium iron phosphate batteries into specialized fertilizers presents a novel input for the conventional npk fertilizer production process. To integrate this recovered phosphate into a market-ready product, it must enter the mainstream npk fertilizer manufacturing process. This begins with precise formulation in a npk blending machine to combine it with nitrogen and potassium sources. The uniformly mixed powder then undergoes fertilizer granulation, a core stage that determines the product’s physical properties.

Advanced npk granulation machine technology is essential here. Depending on the desired granule characteristics, equipment such as a disc granulator machine for wet granulation or a fertilizer roller press machine for dry compaction can be employed within a complete npk fertilizer production line. The choice of this npk fertilizer granulator technology directly impacts the NPK compound fertilizer production capacity and the final product’s slow-release profile. This integration of cutting-edge material recycling with established npk fertilizer production technology exemplifies a sophisticated circular economy, transforming industrial by-products into valuable, intelligent agricultural inputs through precise and scalable manufacturing engineering.