In the fertilizer production process, crushing is a crucial step for improving raw material uniformity and facilitating subsequent granulation. Selecting the appropriate crushing equipment based on the characteristics of different raw materials is essential. The half-wet material crusher, chain crusher, cage crusher, and horizontal crusher are four common types of specialized equipment in fertilizer processing. Although they all belong to crushing machinery, they differ significantly in terms of applicable raw materials, moisture tolerance, crushing precision, and application scenarios. This article provides an in-depth analysis of their core differences, advantages, and usage considerations, offering scientific selection and operational guidance for global fertilizer producers.

Common Principles: Core Safety and Maintenance

Regardless of the type of crusher selected, some universal safety and maintenance principles must be followed. First, controlling impurities in raw materials is critical. Foreign objects such as metal blocks and stones can severely damage core components like blades, chains, or cage bars. Therefore, it is recommended to install magnetic separators and grid screens at the feed inlet for pretreatment. Second, uniform and quantitative feeding is essential for ensuring stable equipment operation, as instantaneous overload can easily cause blockages or motor failure. Additionally, different equipment has varying tolerances for raw material moisture. Exceeding the design range can lead to material adhesion, blockages, or reduced efficiency, so raw materials should be appropriately dried or conditioned based on equipment characteristics. In terms of safety, always check fasteners before operation, lubricate bearings regularly, and clean the chamber promptly after shutdown to prevent hardening and caking. Never open the machine cover for maintenance while the equipment is running to ensure personal safety.

Feature Analysis: Unique Advantages of the Four Crusher Types

The Half-Wet Material Crusher is an expert in processing high-moisture organic materials. It can effectively handle semi-wet materials with a moisture content of 20% to 60%, such as decomposed livestock manure, straw, and biogas residue, without issues of adhesion or blockage. Its core advantages lie in its high moisture tolerance and adjustable crushing granularity (1-5 mm), often achieving the desired product in a single pass without secondary processing. This equipment operates on an impact crushing principle, relying on high-speed rotating wear-resistant alloy blades to impact and tear materials. During use, it is important to ensure that the raw material moisture content does not exceed the upper limit and to regularly inspect blade wear.

The Chain Crusher is known for its simple structure and low maintenance costs. It is suitable for processing caked raw materials with a moisture content not exceeding 25%, such as hardened organic fertilizer or returned granules. Its working principle involves high-speed rotating chain groups impacting and kneading materials, achieving both crushing and mixing effects while producing uniformly sized products. It is primarily used for coarse or medium crushing but should avoid processing overly hard lumps to prevent chain deformation.

The Cage Crusher is designed specifically for fine crushing. It excels in refining dry raw materials (moisture ≤20%), producing finely ground products with particle sizes as fine as 80-120 mesh. It operates with low noise and minimal dust. Its core mechanism involves the shearing and grinding action of a double-layer cage bar rotor. It is suitable for fine crushing of inorganic fertilizer and compound fertilizer powders but is not suitable for processing coarse or hard lumps. During operation, raw material moisture must be strictly controlled, and the gaps between cage bars should be cleaned regularly to prevent blockages that could affect precision.

Horizontal crushers are widely used and essential equipment in production. They can process various dry and wet (≤15%) raw materials, and the crushing particle size (1-10 mm) can be flexibly adjusted by changing the screen. With their large-capacity crushing chamber and high output, horizontal crushers are particularly suitable for large-scale production lines. Horizontal crushers are mainly divided into two types: hammer crushers (impact crushers) and belt crushers (kneading and mixing crushers). When processing high-fiber materials, the feed speed must be controlled to prevent entanglement.

Scientific Selection: Based on Raw Materials and Process Needs

Choosing the right crusher depends on clearly understanding the characteristics of the raw materials and the process goals of the production line. If the main task is to process high-moisture organic fertilizer materials after decomposition, the half-wet material crusher is the optimal choice. For coarse crushing tasks such as breaking up caked organic fertilizer or processing returned materials, the chain crusher is more cost-effective and efficient. When the production requires refining inorganic fertilizer or compound fertilizer raw materials into fine powders, the cage crusher should be selected. For comprehensive production lines with diverse raw material types that require handling multiple materials, the versatile horizontal crusher offers the greatest flexibility and output guarantee.

In summary, understanding the core principles and applicable ranges of each type of equipment, combined with strict daily maintenance, can not only improve the efficiency and quality of fertilizer production but also significantly extend equipment lifespan, providing solid technical support for the development of global sustainable agriculture.

From Crushing to Granulation: A Systematic Production Workflow

Selecting the appropriate crushing machine is the critical first step in preparing raw materials for efficient fertilizer production. This choice—whether a half-wet crusher for moist organics or a cage crusher for fine powders—directly impacts the quality of the mixed feed. In a complete npk fertilizer production line, the uniformly crushed materials are then precisely blended using a npk blending machine before entering the core fertilizer granulation processes.

For organic fertilizer, the chain starts with a windrow composting machine, followed by crushing, before the material enters a dedicated organic fertilizer production line or bio organic fertilizer production line. Granulation is the final shaping stage across all types. This utilizes specialized fertilizer processing machine equipment: a disc granulator for shaping is central to a disc granulation production line, while a double roller press granulator forms the core of a dry roller press granulator production line. The synergy between precise size reduction, accurate blending, and advanced granulation technologies ensures the efficient production of high-quality, application-ready fertilizers for global agriculture.

Introduction: Compost is More Than Just Fertilizer

Composting, an ancient yet modern organic waste conversion technology, has long seen its final products evolve beyond the simple concept of “mature organic matter.” Through different processing techniques and formulation designs, compost can be transformed into various fertilizer products with diverse forms and functions, meeting the varied needs from field agriculture to precision horticulture, and from soil improvement to targeted nutrition. Understanding these derived fertilizer types and the scientific principles behind them is crucial for agricultural producers to choose suitable fertilizers and achieve efficient, sustainable cultivation.

Part I: The Four Major Forms of Compost-Based Fertilizers

1. The Basic Form: Mature Bulk Organic Fertilizer

This is the most primitive and purest form of compost. After complete maturation, organic waste is used directly without additional processing. It appears dark brown or black, with a loose texture resembling fertile forest topsoil. It is rich in humus—a stable organic matter that significantly improves soil structure, increasing soil porosity and water retention. Simultaneously, it contains abundant beneficial microbial communities and slowly released basic nutrients like nitrogen, phosphorus, and potassium. This fertilizer is particularly suitable as a base fertilizer for field crops (e.g., wheat, corn) or as a soil amendment for orchards and vegetable gardens. When incorporated into the soil through tillage, it lays a healthy foundation for crop growth.

2. The Advanced Form: Granular Organic Fertilizer

To meet the needs of modern mechanized fertilization, mature compost can be converted into uniform granules through granulation processes (e.g., disc granulation, drum granulation). These granules are typically 2-6 mm in diameter, with moderate strength, facilitating transportation, storage, and precise application via seeders or spreaders. Granulation not only reduces dust during application but also controls nutrient release rate through physical form, achieving longer-lasting effects. A more advanced product is the “organic-inorganic compound fertilizer,” which incorporates fast-acting chemical fertilizers (e.g., urea) during granulation, perfectly combining the soil-improving function of organic fertilizer with the quick-release properties of chemical fertilizer.

3. The Functional Form: Bio/Functional Organic Fertilizer

This represents an intelligent upgrade of composting technology. By inoculating mature compost with specific functional microorganisms (e.g., phosphorus-solubilizing bacteria, potassium-solubilizing bacteria, biocontrol agents), the resulting “bio-organic fertilizer” not only provides nutrients but also mobilizes fixed phosphorus and potassium in the soil or suppresses soil-borne diseases. Another type, “functional organic fertilizer,” is enriched with biostimulants like humic acid, seaweed extracts, and amino acids, which directly stimulate crop root growth and enhance stress resistance. These fertilizers are “value-added” products widely used in high-value cash crops and protected agriculture.

4. The Refined Form: Organic Water-Soluble Fertilizer

Through physical or chemical methods, soluble organic components (mainly small-molecule humic acid, fulvic acid, and amino acids) are extracted from mature compost to produce liquid or powdered water-soluble fertilizers. This fertilizer type has high nutrient concentration and fast dissolution, fully compatible with modern drip irrigation, sprinkler irrigation, and fertigation systems. It can be rapidly absorbed by crops and is especially suitable for quick nutritional supplementation during critical growth stages (e.g., flowering and fruit setting), making it an ideal choice for precision agriculture.

Part II: Two Technological Pathways: Aerobic vs. Anaerobic Composting

The essence of composting is the microbial decomposition of organic matter, divided into two major technological pathways based on oxygen dependence.

Aerobic Composting: The Mainstream Efficient Process

Aerobic composting relies on aerobic microorganisms (bacteria, fungi, actinomycetes) to decompose organic matter in the presence of oxygen. This process releases significant heat, rapidly raising the pile temperature to 55-65°C within days. The high temperature not only accelerates decomposition but also effectively kills pathogens and weed seeds. Aerobic composting has a short cycle (typically 20-40 days), produces minimal odor during the process (mainly carbon dioxide and water), and yields stable product quality, making it the mainstream process for large-scale organic fertilizer production. Its success hinges on maintaining pile porosity, ensuring oxygen supply through turning or forced aeration.

Anaerobic Composting: Harvesting Both Energy and Fertilizer

Anaerobic composting occurs under strictly oxygen-free conditions, led by anaerobic microorganisms like acidogenic bacteria and methanogens. This process does not generate high temperatures, decomposition is slow, and the cycle is long (typically 3-6 months). However, it has a unique advantage: producing biogas (mainly methane), a renewable clean energy source usable for cooking, lighting, or power generation. Therefore, anaerobic composting (especially biogas projects) is popular in rural areas and small farms, achieving the triple goal of “waste treatment – fertilizer production – energy recovery.” However, it requires strict sealing, and poor management can lead to malodorous gases like hydrogen sulfide.

Part III: How to Choose the Right Composting Pathway and Product?

The choice of composting method and final product depends on specific conditions and objectives:

· For large-scale farms or organic fertilizer plants: Aerobic composting is the preferred choice for its high efficiency and high degree of product commercialization. Granular or functional fertilizers can be produced based on market needs.

· For resource-limited rural households or small ecological farms: Anaerobic composting (e.g., household biogas digesters) can treat waste while providing cooking gas, with biogas slurry and residue being high-quality liquid organic fertilizers.

· For protected agriculture and high-value crop growers: Consider using functional bio-organic fertilizers or organic water-soluble fertilizers to achieve precise, efficient nutrient management and soil health maintenance.

· For field crop producers: Basic mature bulk fertilizer or granular organic fertilizer are cost-effective options that can effectively improve soil and lay the foundation for long-term sustainable production.

Integrated Fertilizer Manufacturing: From Composting to Granulation

Modern fertilizer production encompasses two distinct yet complementary pathways. The organic fertilizer manufacturing process, rooted in advanced composting, transforms waste into stable humus. To create a commercial product, this compost is often shaped using equipment like those in a disc granulation production line. Conversely, the conventional npk fertilizer production process follows a different route. It begins with chemical synthesis and precise blending, followed by granulation. Here, technologies like drum granulation using a rotary drum granulator are common in a standard npk production line.

The choice of granulation method is critical. While wet processes like drum granulation dominate for many NPK blends, alternative technologies exist. The principle of fertilizer granules compaction is employed in dry granulation, utilizing a fertilizer compaction machine or fertilizer compactor as the core of a roller press granulator production line. This diversity in the npk manufacturing process highlights the industry’s adaptability. Whether starting from organic waste or synthetic raw materials, modern integrated systems select the optimal processing and shaping technologies to produce efficient, market-ready fertilizers that support sustainable global agriculture.

The single silo single weight automatic batching system is an automated equipment used for precise metering and mixing of multiple materials.  With its core advantages of high precision and high automation, it is widely used in various industrial fields such as chemical, pharmaceutical, food, and building materials. This system precisely measures each material through independent weighing units and then mixes them according to preset formula ratios, fundamentally ensuring the stability of product quality and significantly improving the efficiency of the production process. It is a key equipment for achieving refined batching in modern industrial production.

Equipment Structure and Composition

The single silo single weight automatic batching system adopts a modular design, with each component working together to achieve precise batching. Its core structure mainly consists of the following six parts:

1. Material Bins (Raw Material Storage Unit)

As the core component for raw material storage, the material bins adopt an independent design, with each bin corresponding to one type of raw material, effectively preventing cross-contamination of different materials. The bin material can be selected from stainless steel, carbon steel, etc., depending on the characteristics of the raw materials. In some special scenarios (such as food and pharmaceuticals), polished stainless steel is used to ensure compliance with industry hygiene standards. The top of the bin is usually equipped with a dust cover and a level gauge to monitor the raw material inventory in the bin in real time, preventing material shortages or overflows.

2. Weighing Unit (Core of Precise Measurement)

The weighing unit is crucial for ensuring batching accuracy. Each material bin is equipped with an independent high-precision electronic scale, whose range and accuracy can be customized according to batching requirements (the conventional accuracy range is ±0.1% to ±0.5%). The electronic scale adopts a suspended installation structure to reduce the impact of equipment vibration on measurement accuracy. It is also equipped with a weighing sensor and a data acquisition module, which can transmit weight data to the control system in real time, enabling dynamic weighing monitoring. 3. Conveying Device (Material Transfer Hub)

Responsible for transferring materials from the storage silo to the weighing unit or subsequent mixing equipment.  The appropriate conveying method is selected based on the material form (powder, granules, liquid) and conveying distance:

Screw conveyor: Suitable for powder and fine granular materials; its enclosed structure reduces dust leakage, and it offers stable conveying efficiency;

Belt conveyor: Suitable for larger granular or bulk materials; it has adjustable conveying speed and low maintenance costs;

Pneumatic conveying system: For materials that are easily airborne and require high precision (such as pharmaceutical raw materials), a closed pneumatic conveying system is used to avoid material loss and contamination.

4. Mixer (Material Homogenization Equipment)

Used to uniformly mix multiple materials according to the formula ratio after precise weighing. Different types of mixing equipment can be selected based on material characteristics, such as ribbon mixers (suitable for powder and granular mixing), paddle mixers (suitable for high-viscosity materials), and V-type mixers (suitable for high-precision mixing scenarios in pharmaceuticals, food, etc.). The mixer is equipped with time control and speed adjustment functions to ensure that the mixing uniformity meets production requirements.

5. Control System (Equipment Operation Hub)

Using a PLC (Programmable Logic Controller) or microcomputer control system, this is the “brain” of the entire batching system. The system has the following core functions:

Formula management: Can store hundreds of different formulas, supporting quick formula recall and modification;

Process control: Automatically controls all process actions such as material conveying, weighing, mixing, and unloading, enabling unmanned operation;

Data monitoring: Real-time display of the operating status of each link, material weight, formula execution progress, and other data, supporting data recording and traceability;

Fault alarm: When there is a shortage of materials, overweight, equipment failure, etc., it will promptly issue an audible and visual alarm and display the cause of the fault.

The control system is equipped with a user-friendly human-machine interface (HMI), using a touch screen for operation. Parameter settings are simple and intuitive, making it easy for operators to use.

6. Safety Protection System (Ensuring Operational Safety)

To ensure the safety of equipment and operators, the system is equipped with comprehensive safety protection devices:

Overload protection: When the weight of the weighing unit exceeds the rated range, the power supply to the conveying device is automatically cut off to prevent equipment damage;

Emergency stop device: Emergency stop buttons are installed at critical positions of the equipment for quick shutdown in case of emergencies;

Dustproof and explosion-proof design: For flammable and explosive environments such as chemical and pharmaceutical industries, explosion-proof motors and sealed structures are used, meeting explosion-proof rating requirements;

Protective barriers and warning signs: Protective barriers are installed for moving parts, and operation warning signs are posted at critical positions of the equipment.

Working Principle

The single-bin automatic weighing and batching system achieves automated batching through a closed-loop process of “preset formula → precise metering → coordinated conveying → uniform mixing → automatic unloading”. The specific working steps are as follows:

Formula parameter setting: The operator inputs the types of materials required for production, the proportion of each material, and the total batching amount through the human-machine interface. The system stores the parameters and generates a production task order;

Material conveying and weighing: After the system starts, it controls the opening of the discharge valve of the corresponding material bin according to the formula sequence, and the material enters the independent weighing unit through the conveying device. The electronic scale collects material weight data in real time and feeds it back to the control system. When the weight reaches the preset value, the control system precisely closes the discharge valve, completing the metering of that material;

Multi-material coordinated metering: Following the above steps, the independent weighing of all formula materials is completed in sequence, ensuring that the weight error of each material is controlled within the allowable range;

Mixing and unloading: After all materials are metered, the control system controls the opening of the discharge door of the weighing unit, and the materials enter the mixer. The mixer operates according to the preset time and speed. After the materials are uniformly mixed, the mixed materials are automatically unloaded to the subsequent process (such as packaging machine, granulator, etc.);

Cyclic operation: After one batching is completed, the system automatically cleans the residual materials in the weighing unit (some equipment is equipped with an automatic blowing function), and executes the next batching task according to the production plan, achieving continuous production. III. Core Features of the Equipment

The single silo single weight automatic batching system demonstrates significant performance characteristics in industrial production thanks to its advanced design and technological advantages:

1. High Batching Accuracy, Ensuring Stable Product Quality

The independent weighing design of “one bin, one scale” avoids the problem of material interference in traditional mixed weighing.  Combined with high-precision electronic scales and dynamic weighing algorithms, it ensures that the batching error for each material is controlled within ±0.1% to ±0.5%. Precise batching ratios effectively prevent product quality fluctuations caused by deviations in raw material ratios, improving the product pass rate.

2. High Degree of Automation, Improving Production Efficiency

The entire process, from formula setting, material conveying, weighing, mixing to unloading, is automatically controlled, requiring no manual intervention, significantly reducing the intensity of manual labor. Compared with traditional manual batching, production efficiency is increased by 30% to 50%, while avoiding human errors in the manual batching process (such as weighing errors, incorrect batching sequence, etc.), making it suitable for large-scale continuous production.

3. Strong Adaptability, Meeting the Needs of Multiple Scenarios

It can flexibly adapt to different forms of materials (powder, granules, liquids, blocks, etc.), supports rapid switching of multiple formulas, and meets the production needs of different industries such as chemical, pharmaceutical, food, and building materials. The equipment’s weighing range, conveying speed, mixing time, and other parameters can be customized according to actual production needs, providing strong scalability.

4. Convenient Operation and Low Maintenance Costs

The user-friendly human-machine interface makes parameter setting, formula management, and equipment monitoring simple and intuitive. Operators can be trained quickly. The equipment adopts a modular structure design, making the assembly and disassembly of components convenient. Key wear parts (such as conveyor belts and weighing sensors) are highly interchangeable, facilitating maintenance and reducing maintenance costs.

5. Safe and Environmentally Friendly, Compliant with Industry Standards

A complete safety protection system ensures the safety of equipment and personnel, reducing the risk of production accidents. The enclosed material bins and conveying system effectively reduce dust leakage and material volatilization, meeting environmental protection requirements; for industries such as food and pharmaceuticals, the equipment materials and structural design comply with GMP and other industry hygiene standards, preventing material contamination. IV. Typical Application Scenarios

Chemical Industry: Used for the raw material blending of products such as coatings, dyes, and rubber, precisely controlling the proportion of each component to ensure stable product performance;

Pharmaceutical Industry: Suitable for high-precision ingredient dispensing of pharmaceutical raw materials (powders, granules), complying with GMP standards and avoiding cross-contamination;

Food Industry: Used for the mixing and blending of food raw materials such as flour, starch, and additives, ensuring consistent food taste and quality;

Building Materials Industry: Applicable to the raw material proportioning of building materials such as concrete, mortar, and tile adhesive, improving performance indicators such as material strength;

Fertilizer Industry: Used for the mixing of raw materials for products such as NPK compound fertilizers and organic-inorganic compound fertilizers, precisely controlling the proportion of nutrients such as nitrogen, phosphorus, and potassium.

Integrating Precision Batching into Modern Granulation Systems

The single silo single weight automatic batching system is the critical first step in ensuring formula accuracy for modern fertilizer production. In a complete npk fertilizer production line, this precision is realized by a npk blending machine, which ensures the exact N-P-K ratio before the material enters the granulation stage. The uniformly blended powder then proceeds to the core fertilizer granulation processes, where it is shaped into final product form.

The choice of granulation technology depends on the product type. For standard compound fertilizers, a disc granulator for shaping spherical pellets is often used in a disc granulation production line. Alternatively, a double roller press granulator forms the basis of a dry roller press granulator production line. This same principle of precise batching and subsequent shaping applies to the organic fertilizer production line and the bio organic fertilizer production line. Whether the final shaping is done by a disc granulator machine or another type of fertilizer granulator, the integration of automated, high-accuracy batching with advanced granulation is fundamental to producing consistent, high-quality fertilizers that meet specific agricultural nutrient requirements.

Malaysia is a core region for global palm oil production, and its processing generates a large amount of waste, including empty fruit bunches (EFB), palm oil mill effluent (POME), and oil palm defatted cake (OPDC). Traditional methods of handling these wastes often lead to serious environmental problems, such as water pollution and greenhouse gas emissions. To address this challenge, co-composting technology has emerged, aiming to transform these wastes into valuable organic fertilizers, achieving a transformation from “pollution source” to “nutrient source.”

Experimental Design and Methods

A systematic study was conducted at the composting plant of the FELCRA palm oil mill in Maran. The experiment used shredded EFB with a moisture content of 60% as the base material and set up four treatment groups: a pure EFB control group (1:0), an experimental group with an EFB to POME ratio of 1:2, an experimental group with a ratio of 1:3, and an experimental group with the addition of OPDC (EFB: POME: OPDC = 1:3:0.2).  POME was used as a moisture regulator and auxiliary nutrient source, while nitrogen-rich OPDC was used to optimize the carbon-nitrogen ratio of the compost. During the experiment, the compost piles were turned weekly to ensure good ventilation and promote the activity of aerobic microorganisms.

Dynamic Changes in the Composting Process

After ten weeks of fermentation, all experimental groups successfully matured, exhibiting the typical characteristics of a deep brown color and earthy smell. Key physicochemical indicators revealed the dynamic patterns of the composting process:

pH Value: The pH value of all compost piles continuously increased, changing from a weakly alkaline to a strongly alkaline environment. This not only conforms to the natural law of alkali production during organic matter decomposition but also effectively inhibits the activity of pathogenic bacteria and weed seeds.

Temperature: In the early stages of fermentation, the temperature of the compost piles increased significantly due to the heat released by microorganisms decomposing organic matter. As fermentation progressed to the later stages, the temperature gradually returned to ambient temperature, indicating a decrease in microbial activity and the stabilization of the compost.

Carbon-Nitrogen Ratio: The carbon-nitrogen ratio of all experimental groups decreased significantly. This is because microorganisms consumed carbon as an energy source during the decomposition process, while nitrogen was retained more in the compost pile. The carbon-to-nitrogen ratio is a core indicator for measuring the maturity of compost, and its decrease indicates more thorough decomposition of organic matter.

Nutrient content: The nitrogen, phosphorus, and potassium content of the final compost product is significantly increased. This is due to the mineralization and decomposition of organic matter, which converts nutrients from complex organic forms into inorganic forms that are easily absorbed by plants, achieving nutrient enrichment and transformation.

Outstanding Performance of the Optimal Ratio Group

Among all treatments, the experimental group with EFB, POME, and OPDC mixed in a ratio of 1:3:0.2 performed the best and was identified as the optimal ratio scheme. Its advantages are reflected in several aspects:

First, the final carbon-to-nitrogen ratio of this group was 23.64, which falls perfectly within the ideal range for mature organic fertilizer (20-25). This is far superior to other experimental groups, indicating the highest degree of compost maturity. Such an ideal carbon-to-nitrogen ratio means that the compost will not compete with crops for nitrogen after being applied to the soil, which is beneficial for crop growth.

Secondly, the pH value of the compost reached 8.4, showing strong alkalinity. This characteristic not only meets the soil acidity and alkalinity requirements of most crops but also has good sterilization and weed control effects, improving the safety of the compost product.

In terms of nutrients, the nitrogen, phosphorus, and potassium content of this group’s compost reached 1.57%, 0.21%, and 0.65%, respectively.  The nutrients are not only balanced but also significantly higher than the control group and the experimental group with only POME added, showing superior fertilizer efficiency.

The addition of OPDC was the key to success. As a high-nitrogen raw material, OPDC effectively neutralized the excessively high carbon-to-nitrogen ratio of EFB, providing sufficient nitrogen sources for microorganisms, thereby accelerating microbial metabolism and reproduction, shortening the composting cycle, and improving overall efficiency.

Value and Prospects of Technological Application

This research has significant technological application value. In terms of environmental benefits, the co-composting technology simultaneously processes three major palm oil processing wastes, greatly reducing environmental pollution caused by incineration, landfill, or direct discharge, especially avoiding the eutrophication of water bodies that may be caused by the direct discharge of POME, strongly promoting the palm oil industry towards a “zero-emission” goal.

The economic benefits are also significant. The high-quality organic fertilizer produced can be directly reused in oil palm plantations, replacing some chemical fertilizers and reducing cultivation costs. At the same time, the resource utilization of waste materials opens up new revenue streams for the company.

More importantly, this research provides a replicable and scalable waste management technology solution for global palm oil producing regions. By identifying the optimal ratio, it sets an example for the industry to achieve a win-win situation of environmental sustainability and economic viability, contributing valuable practical experience to the green transformation of global agriculture.

From Co-Composting to Commercial Fertilizer Production

The co-composting of palm oil wastes such as oil palm empty fruit bunch (EFB) demonstrates a high-value uses of oil palm empty fruit bunch, leveraging its unique oil palm empty fruit bunch composition for sustainable organic fertilizer manufacturing. The optimized fermentation process for EFB, POME, and OPDC is a prime example of efficient organic fertilizer fermentation. To scale this successful laboratory process, the stabilized compost must be integrated into a complete organic fertilizer production line. This requires specialized equipment to handle the industrial scale.

Efficient is critical for large-scale decomposition and is implemented using machines like the chain compost turning machine. Following complete maturation, the compost proceeds to granulation, where equipment such as a new type two in one organic fertilizer granulator can be used to mix and shape the material into uniform pellets. This entire system can be configured as a bio organic fertilizer production line to further enhance the product with beneficial microbes. This integrated approach closes the loop in palm oil production, transforming problematic waste into a valuable, market-ready soil amendment that supports the industry’s sustainability and circular economy goals.

Introduction: Seeing the Unseen World of Granulation

Imagine inside a rotating drum, thousands of fertilizer particles are undergoing complex collisions, mixing, and agglomeration. This process determines the final size, shape, and strength of fertilizer granules, directly impacting fertilizer quality and application effectiveness. However, this dynamic process occurs inside enclosed equipment, invisible to the naked eye. Traditional experimental methods can only see the final result, making it difficult to understand what happens in between. The Discrete Element Method (DEM) acts like a “digital microscope,” capable of precisely simulating the motion trajectory and collision process of each particle, allowing researchers to “see” the microscopic world of granulation, thereby optimizing equipment design and process parameters.

I. What is the Discrete Element Method? A Digital Laboratory for Granulation Research

The Discrete Element Method is a numerical simulation method based on Newton’s second law of motion. It treats each particle inside the granulator as an independent individual, calculating the forces acting on each particle (gravity, friction, collision force, cohesive force, etc.), then determines the particle’s position and velocity at the next moment based on these forces. By tracking changes every microsecond for millions or even billions of particles, DEM can reconstruct the dynamic scenario of the entire granulation process.

For studying drum granulators, a DEM model needs to include three key components: first, the equipment model—accurately replicating the drum’s dimensions, inclination angle, and internal lifter structure; second, the particle model—defining physical properties like particle size, density, and friction coefficients for seed cores and coating powders; and finally, the bonding model—simulating how binders “glue” particles together to form agglomerates. This digital laboratory can repeatedly conduct “virtual experiments,” changing parameters like rotation speed, inclination angle, and feed rate to observe how these changes affect granulation outcomes, without consuming real materials and energy.

II. Revealing Three Motion States Inside the Drum

Through DEM simulation, researchers have discovered three distinct motion states of particles inside the drum, with drum rotation speed being the key determinant:

1. Sliding State (High Speed)

When the rotation speed is too high (typically over 20 rpm), centrifugal force causes particles to cling tightly to the drum’s inner wall, sliding as the drum rotates, like riding a roller coaster. In this state, there is almost no relative motion between particles; coating material cannot uniformly adhere to seed surfaces. It’s like a crowd squeezed in a rotating Ferris wheel, unable to interact with each other. Granulation effectiveness is poorest in this scenario.

2. Slumping State (Low Speed)

When the rotation speed is too low (typically below 10 rpm), particles cannot be lifted to a sufficient height and merely slide slowly down the drum’s inner wall, like sand in an hourglass. Collision frequency between particles is low, mixing is insufficient, and coating is uneven. This is like gently shaking a can of mixed nuts—large and small particles tend to separate.

3. Cataracting State (Medium Speed)

At moderate speeds (typically 10-20 rpm), lifters carry particles to a certain height before they cascade down like a waterfall. In this state, particles gain maximum mixing energy, collision frequency is moderate, and coating material can uniformly adhere to seed surfaces. This is the “golden zone” for granulation, and DEM simulation helps precisely identify this optimal speed range.

Besides rotation speed, the drum’s inclination angle also plays a significant role. The inclination angle determines the “travel” time of particles through the drum: a steeper angle means faster particle movement from feed to discharge, with shorter residence time; too shallow an angle causes particles to accumulate near the feed end. DEM can precisely calculate the residence time distribution of particles at different inclination angles, helping find the optimal balance between granulation effectiveness and production efficiency.

III. Binders: How Does the Invisible “Glue” Work?

Binders are the “invisible heroes” of the granulation process. In DEM models, the effect of binders is simulated through special “cohesive force models.” For liquid binders (like starch solutions), the “liquid bridge force model” is commonly used: when two particles are connected by a thin liquid film, the liquid’s surface tension creates a force pulling the particles together, much like how two wet glasses are difficult to separate.

DEM simulation reveals the subtle relationship between binder concentration and granulation effectiveness: concentration too low results in insufficient liquid bridge force, causing particles to disperse easily and preventing stable agglomerate formation; concentration too high causes excessively strong cohesive forces, making many particles stick together into large clumps, leading to a wide particle size distribution. Through simulation, the optimal binder concentration for specific materials can be found.

Interestingly, DEM also discovered that collision energy significantly impacts agglomerate strength: moderate collisions help compact the agglomerate, increasing granule strength; but excessive collision energy destroys already formed granules. This is like kneading dough—moderate kneading makes the dough more elastic, but over-kneading damages the gluten structure.

IV. Lifter Design: The “Architect” Inside the Drum

Lifters are bars fixed to the drum’s inner wall; their shape and number directly influence particle motion trajectories. By comparing DEM simulation results for different lifter designs, researchers found:

· Straight Lifters: Simple but less efficient, prone to creating “dead zones” in front of the lifter where particles accumulate without participating in mixing.

· Curved Lifters: Can lift particles more smoothly, reducing energy loss, making particle cascading trajectories more uniform, and increasing particle sphericity by 10%-15%.

· Number of Lifters: More is not always better. Too many lifters reduce the lifting height of particles, actually decreasing mixing effectiveness; too few lifters provide insufficient lifting capacity. DEM simulation can help determine the optimal number and arrangement of lifters.

These findings directly guide equipment manufacturers in optimization design. Many modern drum granulators already employ lifter configurations optimized based on DEM simulation results.

V. From Virtual to Reality: The Practical Value of DEM

The value of DEM simulation lies not only in understanding mechanisms but also in guiding practice:

Reducing R&D Costs and Risks

Traditional granulation process optimization requires repeated physical experiments, each consuming a large amount of raw materials and energy, and adjusting equipment parameters is both time-consuming and labor-intensive. Discrete element method (DEM) simulation allows for rapid testing of dozens or even hundreds of parameter combinations on a computer, enabling the selection of the most promising ones for physical verification. This can shorten the development cycle by more than 60% and reduce costs by more than 50%.

Optimizing Performance of Existing Equipment

For granulation equipment already in use, the Discrete Element Method (DEM) can diagnose performance problems: Is the rotation speed inappropriate? Is the lifting blade design unreasonable? Or are there problems with the binder addition method? Through “digital twin” technology, a virtual model is created for each piece of equipment, allowing for the development of personalized optimization plans.

Accelerating New Product Development

When developing new types of fertilizers (like slow-release or functional fertilizers), DEM can predict the granulation behavior of new materials in existing equipment, identifying potential problems in advance and reducing trial-and-error attempts.

VI. Future Outlook: More Realistic, Smarter Simulations

Although DEM has achieved significant success, there is still room for improvement. Current models mostly assume particles are perfect spheres, while actual material particles are often irregularly shaped. Future DEM will integrate more complex non-spherical particle models. More importantly, researchers are developing “CFD-DEM coupling methods,” combining Discrete Element Method with Computational Fluid Dynamics to simultaneously simulate particle motion and fluid flow (binder liquid, air), achieving true multiphase flow simulation.

With increasing computational power and improved algorithms, future DEM simulations will become more accurate and efficient. Perhaps soon, before designing a new production line, fertilizer manufacturers will conduct comprehensive digital simulations to ensure successful commissioning on the first attempt. The Discrete Element Method is bringing the ancient craft of granulation into a new era of digitalization and intelligence.

The Digital Revolution in Fertilizer Granulation Technology

The Discrete Element Method acts as a “digital microscope,” transforming our understanding and optimization of fertilizer granules compaction and other npk fertilizer production technology. This advanced simulation allows engineers to probe the complex dynamics inside a rotary drum granulator or a fertilizer compaction machine, moving from empirical trial-and-error to predictive science. By modeling particle interactions in a virtual environment, it enables the precise design and refinement of equipment, such as optimizing the pressure distribution in a roller press granulator production line or the flow patterns in a disc granulation production line.

This computational power is revolutionizing the entire npk manufacturing process. It allows for the virtual testing of different raw material properties and machine parameters before physical prototypes are built, accelerating innovation in fertilizer production machine development. The shift towards such digital, predictive engineering is a powerful driver for creating more efficient, energy-saving, and intelligent granulation systems, ultimately supporting the goals of sustainable agriculture and precision manufacturing through smarter, science-driven production.