densifiers AND RECYCLING
Densifiers are a staple piece of equipment in the recycling and waste management industries. As the name implies, the purpose of a densifier is to create dense material from lighter materials, to facilitate easier storage and/or handling. Whether the end product is to be used as raw material for manufacturing new products or disposed of, densification of some scrap materials is an indispensable step in recycling, reuse and disposal.
Unlike compactors, which are typically made to handle mixed waste, like office or commercial trash, densifiers are usually designed for a specific material or materials. In addition, densifiers can provide volume reduction ratios as high as 50:1, as compared to a typical ratio of 20:1 in high-end compactors. This lower ratio is also typical of balers, which are sometimes referred to as densifiers. Balers generally function much the same as compactors, but are usually employed in the processing of one or a few materials, such as cardboard, plastic wrap, bottles and cans.
Various industrial applications call for differences in the type and configuration of densifiers. Application considerations include such details as feed type and rate, heated or non-heated, output type, portability and more. The following information may be of help in determining whether a densifier is right for your particular application and what type would best fit your needs.
MATERIALS SUITABLE FOR DENSIFICATION
(EPS) and Styrofoam® are two of the waste products typically densified before reuse in product manufacturing. In addition to being extremely light in weight, these two plastics are easily moldable, which makes them ideal for a wide variety of packing, shipping and stuffing applications. If you've purchased any kind of new appliances, or other fragile items, chances are you've received it in a cardboard carton, fitted with custom-shaped EPS blocks to prevent damage to the contents. They are also commonly used in disposable containers for food and drink. Both materials also posses high R-factors and have been widely used as building insulation, insulating containers and in other, similar applications.
The difference between Styrofoam and EPS is simple. Styrofoam is a
trademarked name (similar to Kleenex) that is blue in color and is used
primarily in the construction industry for insulation in roofing, floors and
walls while EPS is white in color and used for just about everything else.
EPS is also used as loose packing / stuffing materials, for example, packing "peanuts". Because of the light weight, these styrene foam and EPS packing materials can be extremely difficult to store and handle in recycling or disposal operations. Additionally, varying densities and textures for various purposes – florist's foam, for instance – can create challenges. Densification offers a way to provide a more uniform shape, weight and density for manufacturing feeds, as well as stackability and volume reduction for compact storage and shipping.
Polystyrene foam and EPS are petroleum-based and not readily biodegradable. Recycling of these waste products is clearly the best alternative and densifiers can simplify the process. In cases where the products must be discarded, the volume reduction offered by densification is a clear advantage. In either case, Styrofoam and EPS products are ideally suited to densification, due to the large percentage of air cells in their structure, which allows for a great reduction in volume.
Plastic films and textiles are also difficult to dispose of and should be recycled. Grocery bags are one example of a recyclable plastic film product. The number of bags that end up in landfills, water sources and water treatment plants is an issue of ever-increasing importance.
Proper recycling of these lightweight, thin materials usually involves shredding, then melting and extruding the material into a more practical size for the manufacture of new products. Unfortunately, shredded plastic films scatter easily, are prone to static attraction and can be very difficult to feed to extruders. Creating a denser material from the shredded film is the task of a specialized densifier type, known as an agglomerator. The functional differences of these will be addressed later in this guide.
Plastic bottles are among the most widely known "problem" waste products on the planet. Soft drink bottles manufactured of Polyethylene Terephthalate (PET) and containers such as milk jugs, detergent bottles, etc. manufactured of High-Density Polyethylene (HDPE) are not environmentally-friendly as trash, but highly recyclable.
Bottles are typically baled at collection points, to facilitate shipment to recycling facilities. Obviously, the more compact the individual bottle, the more solid and compact the bale. The term "densifier" is often applied to first stage of the baling process, in which the bottles are perforated and flattened. These units are available separately and as add-ons for balers, but will not be addressed in this guide.
Aluminum and steel cans are among the most commonly recycled waste items. While you will often hear the term "can densifier" used for can recycling equipment, the finished slug from these units generally is not as dense as the output from a typical EPS densifier. We classify these as balers or compactors and will not address them in this guide.
EPS and Styrofoam
As mentioned briefly above, the most common type of densifier is used for compaction of EPS and Styrofoam. These units usually accept irregularly shaped feed and most often can process both EPS and Styrofoam. Depending on the application, they may be hand fed or fitted with a feed conveyor. Thanks to the low density of the plastic foams, any pieces that might be too large for the feeder can simply be broken by hand.
Most foam densifiers operate without the addition of heat, because overheating may break down polymers in the material and weaken the material. Densification is achieved through extreme pressure, applied by hydraulic or electric rams. The air cells in the plastic foam are collapsed, resulting in a great reduction in volume and resiliency.
The output of these units is usually formed into continuous, squared "logs", which can be easily cut or broken into convenient lengths for storage. The unique shape is ideal for stacking and easily arranged in palette ties for storage and/or shipment.
Specialized densifiers intended for processing plastic films are often referred to as agglomerators. These units shred and heat thermoplastic film just to the melting point, so that it fuses into larger pieces. Heating is usually performed strictly by the friction of the shredding knives. This prevents overheating, which can break down polymers and lower the quality of the end product. Most of these machines use a force feed, often by means of a screw or auger.
The heated material is then quickly cooled, sometimes using water injection and sometimes by air. The resulting granules are sorted by size and smaller particles return to the feeder, to be re-processed to achieve the optimal size. The end result is granules of uniform size and density, suitable for feeding to manufacturing equipment.
THE ADVANTAGES OF DENSIFICATION
Perhaps the most important gains to be achieved through the application of densifiers are the environmental ones.
EPS, Styrofoam and thermoplastic films do not readily biodegrade. Although EPS is generally considered safer for the environment and is often used as loose fill, Styrofoam and thermoplastic films contain polymers that are harmful to the environment in many ways.
Estimates place the amount of Styrofoam in public landfills in the US at 25 to 30 percent by volume. Styrofoam can release contaminants into the atmosphere and the soil upon exposure to sunlight. The practice of burning landfills to reduce overall volume creates further hazards when Styrofoam is present, since it produces even more dangerous chemicals when ignited. The EPA has initiated and enforces regulations concerning the burning of landfills.
Thermoplastic films pose many of the same problems. In addition, plastic remanufactured from these films are said to be responsible for the demise of a large number of and marine animals annually through accidental ingestion. The use of plastic bags and similar products is a topic of much controversy throughout the world today.
Because densification greatly aids recycling and remanufacturing of EPS, Styrofoam and plastic film products, responsible individuals and companies are employing densifiers as part of their manufacturing and/or waste disposal processes.
Even in rare cases where these waste products will be disposed of in landfills, densification offers a waste product that is easier to manage, more compact. Densified EPS foam may even be used as a loose fill or retaining material.
Because petroleum is used in the manufacturing processes of both Styrofoam and plastic films, the recycling of these products will help to lower oil production demands. Among other things, this has a positive effect on the global economy. Although the difference may seem negligible on an individual basis, as awareness and action increases globally, so will the economical impact. By utilizing densifiers to preprocess waste products for easier recycling, business owners can contribute to this economic growth.
On the "home front", industries that manufacture products with these materials may see significant fiscal advantages in the use of densifiers. Because of the difficulty presented in handling small pieces of foams, densifying them may decrease the number of man-hours involved in transporting waste material and returning it to the manufacturing process. Likewise, cast-off material from the manufacture of polymer films is much easier to reuse if densified into larger, uniform, easier to handle particles.
The amount of actual savings realized will, of course, vary according to the product produced, the material used and other factors in the individual manufacturing methods. Each manufacturer should analyze complete production costs and factor in the cost of densification equipment to determine the long-term gains.
Savings may also be realized in reduced energy consumption in the manufacturing process. Again, the amount of savings, or lack thereof, can only be determined through a thorough analysis of the manufacturing process and the associated energy costs.
For industries that simply receive large amounts of plastics as packing material, etc. there may be an income stream available through the sale of these products to the manufacturing industry. As environmental consciousness increases, more and more manufacturers are purchasing recycled materials from consumers for use in their factories. Densified material is more desirable to these manufacturers, and easier to store and transport.
Several states in the US now offer tax incentives for recycling, so this may also offer savings that translate into financial gains for some businesses.
Increased use of plastic foams and films in manufacturing industries worldwide has created a tremendous surplus of non-biodegradable waste to be dealt with. Thousands of consumer products made from these materials are used throughout the world. Because of their resistance to degradation and the complications caused by the toxic materials in some of the materials, proper disposal of these goods is a multi-faceted problem.
Recycling of these materials to remanufacture the product or manufacture new products is the most ecologically sound method of disposing of consumer goods made from materials such as EPS foam, Styrofoam and plastic film. The low density and highly moldable properties of these substances creates many products that present challenges in recycling because of their resiliency, size and shape.
Densifiers offer a means of producing a raw material of uniform shape and higher density that is easier to store, ship and feed. Foam densifiers usually create "logs", while those intended for processing plastic films often produce granulated plastic. Because of their increased weight and reduced volume, the densified products are less likely to end up contaminating the environment and less material is required for the production of new products.
In addition to environmental concerns, there may be fiscal advantages in recycling plastic foams and films for many industries. These include those that use large quantities of these products, as well as those that manufacture them. Because of the benefits provided in the recycling of these materials, these industries may realize savings by installing and using densifiers.
Business owners and managers should carefully analyze the costs involved in purchasing, operating and maintaining densifiers and compare these to the possible gains to determine whether to invest in them. Initial gains may be small, so long-term projections should be considered.
We sincerely hope that this guide has been helpful to our visitors in explaining the functions, applications and possible advantages of densifiers. For those who are considering purchasing densification equipment, we hope this information proves valuable in making your decision.
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