In-plant recycling and reclamation of extruded scrap for improved sustainability

Sustainability: The ability to be maintained at a given rate or level; avoidance of the depletion of natural resources to maintain an ecological balance. 

By definition, sustainable plastics should be managed within a sustainable materials management system or circular economy that avoids creating waste, toxins and pollutants. Unlike a linear economy that takes resources, makes products, uses these products and disposes of them, creating waste, materials in the circular economy are collected and reused after each use. 

Plastic producers place heavy emphasis, and rightly so, on a product's ability to be reused at the end of its life cycle as they transition toward a more sustainable, eco-friendly position within the broader circular economy. However, an often-overlooked opportunity for reuse comes within the production of the product itself via in-plant recycling or reclamation of production scrap. Creating and implementing a reclaim program an help a producer become more sustainable and often can be a cost-effective, profitable endeavor.

But an in-plant recycling or reclaim operation is a large undertaking that requires significant analysis to determine if it is a fit for the organization and production process. Producers must understand the type of scrap produced and the economics behind such a program. They must also identify and form an implementation plan for the reclamation of production scrap as well its reintroduction into the production process.

Understanding and defining production scrap

Production scrap comes in all forms, shapes and sizes. Some can be reclaimed online, offline or not at all.

In the case of blown or cast film and sheet, startup purge, trims, bad rolls and loose products should be reclaimed. Blow and injection molded scrap, such as flash, sprues, runners and whole or cut-down parts, should be reprocessed. Other processes, such as compounding and fiber extrusion, also produce considerable production scrap.

Producers often can reclaim production scrap directly online, which is known as direct scrap reclaim. For film and sheet, edge trim can be processed and fed directly back to the extrusion line. In blow and injection molding, scrap such as flash, trimmings and runners can be granulated beside the machine and fed directly back to the process. Producers must handle production scrap offline for all other processes, such as for pipe and profile, compounding and fiber extrusion.

Processors that still need to develop their internal recycling capabilities typically are left with three choices when dealing with their scrap: disposal, resell or toll processing. Disposal is the last resort before incineration, where the scrap can be used as fuel to recover its BTU value. While not ideal, disposal is the only option for scrap that, for various reasons, cannot be reused or converted to energy. Often, size reduction and compaction are used to prepare the material for efficient transport and disposal, which can be critical for cost-effective operations.

Economics and decision-making for in-house scrap reprocessing

The first step is to evaluate the economics of the current production waste handling process. You can then calculate the potential savings per year to substitute the current handling methods, including disposal, resale or toll processing. After calculating these potential savings, you can compare them against the costs associated with an internal scrap reclaim operation, including any process modifications.

To understand the true economics and cost of disposal, you must calculate real and ecological factors. The cost calculation should consider factors such as the carbon footprint from transporting the waste and landfill tipping fees. If you plan to sell the scrap, you must calculate the net profit from the resale, considering costs such as marketing, administration, storage and logistics. These costs can offset a considerable amount of the price per pound received from selling the scrap. When determining an accurate cost analysis for toll processing, producers must also consider additional factors, such as the implications of quality control and material loss.

Once you have established a complete cost profile for the current methods of handling your process scrap, you can calculate the potential cost savings per year to substitute your scrap materials' disposal, resale or toll processing with in-house processing.

The first step is to evaluate the production process to determine the potential reuse of reclaimed materials. You can collect much of the necessary information by running trials on your processing line using reclaimed materials. Identify any detrimental effects that reclaimed materials have in the process, such as reduced output or automation and product quality issues. Study the impact of different reclaim forms, such as regrind, densified particles or repelletized material. Process modifications needed to maximize and optimize reclaim use need to be determined, as well as the costs associated with their implementation.

After identifying the ideal form or forms of the reclaimed material for reintroduction and any process changes needed to accommodate them, you can begin looking at different processes to recover the material.

Photo courtesy of Vecoplan

Once you have decided on the correct processes to convert scrap into the desired form for reprocessing, the associated costs can be determined. Calculate the potential savings per pound of material recovered. Based on the process limitations of your production lines, the maximum percentage of reclaim material introduction should be established, thereby indicating the potential material savings per year.

The final step is to calculate the cost for an internal scrap reclaim operation; this includes the capital equipment and operational cost per pound for the reprocessing line. With this information, you can compare this estimated cost savings per pound and factor in the amount of scrap that can be reprocessed for a projected payback. 

Armed with this information, you can prepare the business plan for upper management to evaluate and make a tentative decision on whether to move forward with the project.

Detailed evaluation for introducing reclaimed material

With the initial cost analysis and justification complete and management's sign-off to move forward, you are ready to dive into the implementation details. Transportation and storage of reprocessed material is your first consideration, knowing that regrind materials and densified scrap handle quite differently from pellets.

All your standard options, such as gaylord boxes, super sacks, hoppers/bins and silos, still are available. Your material conveying systems, however, must be analyzed for these reprocessed material forms, including material line sizes, dust collection systems and material holding bins. If you have decided to repelletize, storage and transportation equipment typically can be used as is.

Blending and feeding systems need to be evaluated. While in most circumstances, you can use existing systems to introduce reclaimed material, new blending and feeding equipment could need to be added or modified to accept the new material stream.

The most complicated step is identifying and implementing any modifications needed to the production process for making your end products. The extruder and or extruder screw could need to be modified to accept higher levels of reclaimed material. Nonpelletized reclaim materials could require a larger feed section, deeper metering flights and improved venting. Melt pumps also can be incorporated into the process. Mixing sections or static mixers can be added to the extruder to improve melt homogenization. Upgraded melt filtration could be required to handle increased material contamination arising from using reclaimed materials. Gauge measurement and control could need to be upgraded or added to better monitor the product's overall dimensions.

Despite best efforts, reprocessed materials can negatively impact the end product. Viscosity loss, gel formation and color degradation can result, as well as loss of mechanical properties. Process output and stability issues can lead to loss of production and gauge control. Contamination and visual imperfections also could be unavoidable. Though the market insists on products manufactured with reclaimed content, the producer must maintain aesthetics and performance at the highest level possible. Therefore, identifying potential adverse effects on the final product early on and implementing solutions to offset them are critical. 

Processes for reclaiming production scrap

Photo courtesy of Vecoplan

A critical initial step in any reclaim process is size reduction. A preshredder could be required for proper sortation, inspection and separation of foreign materials. A second size-reduction step, or reshred, could be needed for further material processing for either densification or re-pelletizing. Further size reduction also could be required to granulate the product to a processable size or even pulverize it to return materials to their original powdered or granulated form. 

Complex material streams, even postconsumer streams, could require sorting for color and polymer type. Contamination removal is a critical last step and often includes ferrous and nonferrous metal removal and soft contamination removal by wash systems, including wet and dry cleaning operations. 

If the recovered material cannot be used in a simple regrind form, either densification or pelletizing must be incorporated. The extrusion process can include traditional single-screw extruders, twin-screw compounding extruders or specialized recycling extruders.

Pelletizing can be done either “strand,” using a bath or water slide, or “die face,” either air or water-cooled. Techniques also are available to help preserve polymer properties during the recovery process, including viscosity recovery or boost, color and odor removal and improvement of mechanical properties.

Future considerations

There's a lot to think about when you want to go green and move toward a more sustainable, circular production process, considering you have to address ecological and economic factors. Consider hiring a sustainability manager responsible for looking into all aspects of production to minimize waste. As your internal recycling capabilities grow, consider bringing in other producers' production scrap and even postconsumer scrap to supplement your own. Grow your sustainability program into a profitable business unit that your competitors will admire and envy and lead the way toward the ultimate goal of zero waste.

The author is the business development ad complex applications manager at Archdale, North Carolina-based Vecoplan LLC. Contact him at dana.darley@vecoplan.com.