The Growing Challenge of Agricultural Plastic Waste
The global agriculture industry relies heavily on plastic films. From mulch films that suppress weeds and conserve water to greenhouse and tunnel covers that extend growing seasons, these materials—primarily Low-Density Polyethylene (LDPE) and Linear Low-Density Polyethylene (LLDPE)—are essential for modern food production.
However, this reliance generates millions of tons of highly contaminated waste plastic annually. Unlike post-consumer packaging, agricultural film is notoriously difficult to recycle. It is burdened with heavy contamination, often accounting for 50% to 80% of the bale weight, including soil, sand, rocks, moisture, pesticides, and organic residue.
Disposing of this material through landfilling or incineration is an environmental and economic failure. The only sustainable solution is processing it through a specialized, industrial-grade agricultural film recycling line. This process is complex, requiring robust machinery designed specifically to handle heavy soiling and abrasive materials.
This article provides a detailed, step-by-step workflow of a complete agricultural film recycling line, from contaminated bale to high-quality, marketable pellets.
Understanding the Input Material: Why Ag-Film Is Different
Before analyzing the workflow, we must understand the input material. An agricultural film recycling line is not a one-size-fits-all solution. The design of the line, particularly the washing segment, depends entirely on the type of film and its contamination level.
- Mulch Film: This is the most challenging category. Used directly on the ground, it is collected with extremely high levels of soil, sand, and stones.
- Greenhouse Film: This material is generally cleaner than mulch film but is often thicker and contains UV stabilizers. Contamination includes dust and organic residue.
- Silage Bags/Bunker Covers: These are heavy-duty, often multi-layer films contaminated with animal feed residue, moisture, and organic waste.
A successful recycling operation requires a line engineered to separate this contamination efficiently, protecting downstream equipment and ensuring the purity of the final product.
The Complete Workflow: A Step-by-Step Breakdown
The transformation of waste farm plastics into reusable resources involves two primary systems: the Washing and Drying Line and the 펠렛화 라인. These systems work in sequence to shred, scrub, separate, dry, melt, filter, and pelletize the material.
Phase 1: Pre-Processing and Size Reduction
The initial stage prepares the bulky, contaminated material for the washing process.
- Debaling and Feeding: Waste film arrives in tightly compressed bales. A Bale Breaker (or Debaler) is used to break these bales apart, loosening the material. This mass is then fed uniformly onto a conveyor belt to prevent overloading the system. Manual sorting may occur here to remove obvious, large contaminants like metal wiring, large rocks, or wood.
- Initial Shredding (Primary Size Reduction): The loose film is fed into a heavy-duty Single-Shaft or Double-Shaft Shredder. The goal here is not to create the final flake size, but to tear the film into larger (e.g., 4–10 inch) pieces. This “opening” process is critical: it exposes the contaminated surfaces, allowing water and friction to penetrate the material in the subsequent washing stages.
Phase 2: The Washing Line (Cold and Hot Washing)
This is the most critical phase of the entire system. Failure to adequately clean the material here will result in poor pellet quality and catastrophic damage to the pelletizing extruder.
- Pre-Washing and Soaking: The shredded film pieces enter a Pre-Washing Drum or a soaking tank. This step uses water to perform an initial rinse, loosening caked-on mud and allowing heavy contaminants like stones and small metal fragments to drop out early.
- Wet Crushing (Secondary Size Reduction): The pre-washed material moves into a Wet Crusher or Granulator. Unlike a dry shredder, this machine operates with a constant flow of water. It cuts the film into smaller, uniform flakes (e.g., 1–2 inches) while simultaneously beginning the scrubbing process. The water spray cools the blades and flushes away liberated contaminants.
- High-Speed Friction Washing: This is the core scrubbing engine of the line. Flakes are fed into a High-Speed Friction Washer, which uses paddles rotating at high RPM (over 1,000 RPM) inside a screened cylinder. This high-velocity agitation creates intense friction between the plastic flakes, scrubbing them against each other and the screen, effectively scouring off paper labels, adhesives, and embedded dirt.
- Float-Sink Separation: The scrubbed flakes enter a Float-Sink Tank (also called a Separation Tank). This is the key separation stage. Based on density, LDPE/LLDPE (with a specific gravity <1.0) floats on the water. All heavy contaminants—sand, soil, glass, metal, and other plastic types like PET (polyethylene terephthalate)—sink to the bottom, where they are removed by a screw auger. Paddles gently push the floating, clean LDPE film toward the exit. This step is often repeated (using multiple tanks) to achieve high purity levels.
- Hot Washing (Optional but Recommended): For film contaminated with oils, agricultural chemicals (pesticides/herbicides), or stubborn adhesives, a Hot Washing Tank is necessary. Flakes are steeped in hot water (60–80°C), often with detergents or caustic soda. This process dissolves glues and emulsifies oils, ensuring a completely clean surface necessary for high-quality pelletizing.
Phase 3: Dewatering and Drying
Before the clean plastic can be melted, nearly all moisture must be removed. Efficient drying is essential for energy efficiency and final product quality. Any moisture remaining will turn to steam in the extruder, causing bubbles (voids) in the final pellets and process instability.
- 기계적 탈수: The wet flakes first enter a mechanical dewatering machine, typically a Screw Press or a Centrifugal Dryer. The Screw Press uses high pressure to squeeze water out, while the centrifugal dryer spins the flakes at high speed, flinging water off through a screen. This mechanical step efficiently removes the bulk of free-flowing water.
- Thermal Drying System: The mechanically dried flakes, which still retain surface moisture (approx. 10-15%), are fed into a thermal drying system. This typically involves a hot air pipeline where the flakes are tumbled through a stream of hot air, reducing the final moisture content to less than 5% (and ideally below 1%).
Phase 4: Pelletizing (Extrusion and Filtration)
The final phase converts the clean, dry flakes into dense, uniform, and marketable pellets (also called granules).
- Densification and Feeding: The light, fluffy flakes (often called “film fluff”) have a low bulk density, making them difficult to feed directly into an extruder. They are first fed into an Agglomerator or Compactor, which uses friction and heat to densify the material into a warmer, heavier “popcorn-like” consistency. This material is then fed directly into the extruder screw.
- 압출 및 탈기: The material enters the main Extruder. The rotating screw melts, mixes, and homogenizes the plastic. This stage is crucial for agricultural film, which often contains residual moisture and inks. The extruder must be equipped with one or more Vacuum Degassing (Venting) ports. These vents apply a vacuum to the molten plastic, sucking out any remaining moisture, volatiles, and trapped gases.
- 용융 여과: This is the final purification step. The molten plastic is forced through a high-pressure Melt Filtration System. This system contains fine mesh screens that capture any remaining non-plastic contaminants (carbon residue, unmelted particles, residual metal) that survived the washing line. For heavily contaminated agricultural film, a continuous back-flushing screen changer is recommended to avoid downtime associated with manual screen changes.
- Pelletizing and Cooling: The clean, filtered molten plastic emerges from the extruder die head. The most common method for LDPE film is a Water-Ring Pelletizer. Blades spin directly against the die face, cutting the strands of plastic into small pellets, which are immediately quenched by a circulating water ring and transported to a cooling/drying system. The resulting pellets are uniform, dense, and ready for bagging.
Buyer’s Guide: Key Factors for Your Recycling Line Investment
When sourcing an agricultural film recycling line, buyers must look beyond the price tag. The efficiency and longevity of the line depend on engineering tailored to your specific needs.
- Define Your Input: Provide your supplier with accurate data. What is the average contamination percentage by weight? Is it mostly sand and soil (requiring robust float-sink tanks) or oils and chemicals (requiring hot washing)?
- Washing Is Paramount: Do not cut costs on the washing line. Insufficient washing (e.g., too few friction washers or separation tanks) will send dirt and sand into your pelletizer. Abrasive contaminants will destroy the extruder screw and barrel, leading to astronomical maintenance costs and constant downtime.
- Water Treatment: An industrial washing line uses a significant amount of water. A closed-loop water filtration and treatment system is essential. This system cleans and recirculates the process water, drastically reducing water consumption and managing the discharge of contaminated sludge.
- 자동화 및 통합: A modern line should be integrated, allowing the throughput of the washing line to match the capacity of the pelletizing line. Look for systems with sensors and PLC controls to manage feed rates, temperatures, and motor loads efficiently.
Conclusion: Turning Waste into Value with Rumtoo
The workflow for recycling waste agricultural film is one of the most demanding processes in the plastics industry. It requires a sophisticated, sequential system of robust machinery capable of shredding, scrubbing, separating, drying, melting, and filtering heavily contaminated material.
A successful operation is not built on individual machines, but on a complete, integrated solution engineered to work together.
At Rumtoo, we specialize in designing and manufacturing complete plastic recycling lines tailored to the specific challenges of our clients. Our agricultural film recycling solutions are engineered for durability and efficiency, focusing on maximizing purity in the washing stage to protect your investment in the pelletizing stage. We provide systems that turn challenging waste streams into high-quality rLDPE pellets, creating value and supporting a true circular economy.
Contact our engineering team today to discuss your specific agricultural waste stream and request a quote for a custom-designed recycling line.
