De-mingling the Mix

Msw Bug Web

According to the most recent data available on the collection and recycling of plastics in the US, all indicators point to an increase in recovery. Municipal collection programs are growing, and as they do, communities are increasingly moving to commingled curbside collection. Increased efficiency and accuracy in separation is needed now more the ever as demand for post consumer resin (PCR) continues to rise. Additionally, PCR is increasingly being used for high-end applications, such as bottle-to-bottle recycling, and the upper threshold of PCR in products continues to be driven higher. This trend means greater demand for near pure-resin streams, and obtaining that level of purity means greater reliance on automated sorting.

To better understand the current technology available to perform the task of “de-mingling” the mix of plastics received by MRFs and reclaimers, the American Chemistry Council funded an assessment of commercially available sorting technologies. The intent of the study was to provide the industry with a practical, side-by-side comparison of the available technologies. With this information, MRFs and reclaimers can quickly narrow down the equipment options that will best fit their operational needs.

Managing municipal solid waste is more than landfilling: publicity, education, engineering, long-term planning, and landfill gas waste-to-energy are specialties needed in today’s complex environment. We’ve created a handy infographic featuring 6 tips to improve landfill management and achieve excellence in operations.  6 Tips for Excellence in Landfill Operations. Download it now!

Need for Automated Sorting Technology
In the hopes of capturing more PET and HDPE, many communities are casting their nets wider, allowing residents and businesses to divert all plastic bottles (numbers 1–7), and in some cases non-bottle rigid containers as well. The Association of Postconsumer Plastic Recyclers (APR) and ACC reported total pounds of US plastic bottles recycled reached a record high 2.425 billion pounds in 2009, an increase of 46 million pounds over 2008 levels. Of those, 1.44 billion pounds were PET bottles, and 981.6 million pounds of HDPE bottles were recycled. And as of 2006, over 2,000 communities throughout the US offered “all bottle” collection programs. That number has likely grown in the past four years with the expansion of single-stream collection service.

Additionally, new efforts are focusing on expanding the collection of non-bottle rigid plastics, through both curbside programs and drop off locations. Approximately 55% of the non-bottle rigid plastics come from durable goods, such as pallets, crates, buckets, and electronic housings. According to a study done for the ACC by Moore Recycling Associates, in 2008, 361 million pounds of non-bottle rigid plastics were collected for recycling. The same study indicated 28 of the 100 largest communities collect non-bottle rigids through curbside collection, with 16 of those collecting rigid plastics beyond bottles and containers.

Managing municipal solid waste is more than landfilling: publicity, education, engineering, long-term planning, and landfill gas waste-to-energy are specialties needed in today’s complex environment. We’ve created a handy infographic featuring 6 tips to improve landfill management and achieve excellence in operations. 6 Tips for Excellence in Landfill Operations. Download it now!  

According to Governmental Advisory Associates, as of 2008, about 120 of the 570 MRFs in the US were receiving single-stream, or fully commingled, material. To handle this mixed material, MRFs have begun employing automated sorting systems to more efficiently separate the more valuable HDPE and PET containers from the remaining numbers 3–7, and non-resin mix. When installed in a MRF, automated sorting equipment is most commonly used to generate streams of PET and HDPE, or PET and natural HDPE and colored HDPE. By 2006, 50 MRFs in the US were using automated sorting technology to separate plastics. That number has likely grown, and future demand for sorting equipment is expected to be strong from MRFs in coming years.

In addition to automated sorting technology saving significant labor costs in material sorting, optical and mechanical sorting technology can be highly accurate. Manual sorting can yield higher contamination, particularly in the event that resins are present in the stream that can visually be easily mistaken for another resin. This is particularly the case for PET, PLA, and PVC bottles, all of which can easily be mistaken for one another by the human eye.

Findings in 2006
Ron Perkins (R.W. Beck) conducted a study of sorting equipment for the ACC’s predecessor that was similar in scope. Building on the foundation of Perkin’s assessment, this study standardizes and expands the evaluation criteria for sorting equipment, and includes hand-held units and equipment developed for sorting plastics from electronics.

Growth in Technology
In just four years, technology offerings increased significantly. In 2006, Perkins identified eight manufacturers of 23 systems. The breakdown of systems was 17 whole-container sorters and six flake-sorting systems. Just four years later, 4R identified 19 manufacturers of 54 sorting systems. The aggregated systems breakdown into 27 whole-unit sorters and 27 flake-sorting systems. While both categories of systems grew, the availability of flake sorters grew exponentially. This 2010 calculation includes nine e-plastic sorting systems, while those systems were not included in the 2006 study. However if you normalized the data by removing those ten systems, the industry saw a three-fold increase in flake sorting systems, from six systems in 2006 to 17 systems presently available.

Technology Assessment
While each system is different, all automated sorting technologies have three core aspects. Each has a conveyor with some sort of feed regulator. The material is fed through a sensor that analyzes the material and the information is inputted into a computer system that determines how the material will be sorted. The final component is a pneumatic system that segregates material into the desired streams. Each system was evaluated based on seven criteria:

  • Basis of technology
  • Primary application
  • Resins identified
  • Colors sorted
  • Throughput
  • Accuracy upgrades
  • Optional features

When reviewing the information, keep in mind that most of these systems are scalable. Many of these units can be sized with wider belts, or other configurations, that can increase capacity. Second, all automated sorting equipment must be maintained and cleaned to attain optimal function and sorting accuracy. Routine upkeep on these units is essential to maintaining optimal performance. Third, the quality of material input will affect purity of output. It is best to sort bottles before grinding them into flake. This will help reduce levels of contamination in the flake. Depending on the level of contamination, it may be necessary to double-sort flake. This can be particularly true for applications that require very high levels of purity, such as bottle-to-bottle recycling. And lastly, in terms of flake sorters, units are designed for an optimal range of flake sizes. Flake that falls outside of that range can negatively impact sorting accuracy.

Basis of Technology
Two primary forms of technology are employed to sort plastics by resin: spectroscopy and x-ray. In short, equipment that uses spectroscopy emits light and each type of plastic reflects that light with a unique signature, or wavelength. A sensor reads that signature and the processing unit decides how the plastic should be sorted. Some examples of spectroscopy technologies include near infrared (NIR), laser raman, and midrange infrared.

The second technology, x-ray, looks at the plastic on an elemental level. These units include both traditional x-ray and xrf, or x-ray fluorescence, which uses secondary (fluorescent) x-rays to analyze material. X-ray technology is particularly useful in detecting elements such as chloride (PVC) and bromine additives, such as the brominated flame-retardants, often found in plastics used in electronics. While PVC can be identified by spectroscopy, additives such as bromine cannot.

Two primary technologies are employed for color sorting. These consist of vision technology, which uses cameras, such as CCD linear cameras, and spectroscopy, including visible-range spectrometers (VISs). Many of these technologies can see any shade that is seen by the human eye and can differentiate between slight differences in clear PET, such as blue versus green.

What to Expect When Buying Equipment
Pricing for equipment varies based on capacity and features. Buyers can expect to pay in the range of $100,000 to $300,000 for a system that sorts whole containers. Flake sorting can be more expensive with the range averaging $150,000 to $350,000. Flake units can cost upwards of $600,000 depending on the features and manufacturer. This is the estimated cost of buying a piece of equipment from a manufacturer. Keep in mind there are additional costs that are incurred in terms of installation, shipping of the unit, employee training, and downtime that may occur during installation and startup.

In terms of lifespan, most of these units are built to last. Manufacturer warranties typically extend into the 10 to 15 year range; however, some manufacturers report systems remaining in operation 17 years or longer after initial installation. Much of the life span of a unit depends on adherence to routine maintenance and cleaning. While many of these systems will operate for years, obsolescence is an issue that can force a unit into early retirement. Obsolescence seems to be less of an issue for MRFs, which are often seeking to maximize the value of PET and HDPE bales, and more of an issue for reclaimers, who desire to remove contaminants down to the lowest levels. One way system manufacturers are addressing the threat of obsolescence is to provide customers with regular software updates that recognize new or unfamiliar packaging that may be introduced into the marketplace and end up in the plastic recycling stream.

Whole-Unit Sorting Equipment
There are currently 13 manufacturers offering 27 different units that will sort whole plastic containers. Two of those units are singulated feed, where containers are metered through the sensor individually, and the rest are mass-feed systems. Those manufacturers of singulated feed systems include:

Specifics regarding the technology, capacity and performance of each unit can be found in the updated 2nd edition of the report, which can be downloaded at, http://www.americanchemistry.com/s_plastics/doc.asp?CID=1579&DID=10919.

Flake Sorting
Currently, 14 manufacturers offer 27 different units that sort shredded plastics (this includes plastics commonly referred to as plastic flake), as well as size-reduced non-bottle rigid plastics, such as plastics from electronics. Manufacturers of flake sorting equipment include:

Hand-Held Devices
In addition to automated sorting technology, a number of hand-held resin identification devices are on the market. These devices serve a different function than automated sorting technology, which identify and sort high volumes of mixed plastics. Rather, these hand-held units are used to identify large volumes of similar material. Many hand-held units are used to identify products such as carpet and other flooring, electronic housings and other large or bulky items. These portable devices can provide important information for buyers and reclaimers during inspection of material, providing information so they know exactly what materials they are accepting. Likewise, hand-held devices are an efficient way to identify material in bulk. Companies offering hand-held scanning devices include:

Outlook for Automated Sorting Technology
Demand for automated sorting technology for plastics will continue to grow over the next 10 years. A number of factors will drive demand for these systems, including continued trends in commingled collection of materials, the move by more MRF toward automation, and increasing labor costs that will necessitate a switch to automation. Efforts are also underway to expand the resins that are recycled, and those efforts are reaching far beyond just PET and HDPE. As collections increase, new opportunities are created for optical sorting installations. Industry experts predict a number of trends will shape the demand and use of automation in plastics recycling.

Industry consolidation will continue. Since 2006, a number of consolidations and mergers have occurred amongst equipment manufacturers. In the past four years, Buhler acquired Sortex, TiTech purchased Commodas, a joint venture between Innov-X and BT-Wolfgang Binder GmbH was born, and a merger between RTT and Stienert occurred. Much of this activity is viewed as a result of industry maturation, and this trend will continue. More activity is expected in the development of partnerships to offer turnkey operations and installations. Such alliances have already been forged between Bulk Handling Systems and NRT, and CP Manufacturing and MSS. Alliances of this nature are expected to grow, particularly to meet the needs of MRFs as they modernize and expand.

Adoption of sorting equipment in export markets (China, India, etc.) will be slow in the near-term, but grow in next 10 years. Automated sorting technology has largely not been adopted in developing countries, such as China, because low labor costs do not justify the capital investment in equipment. However, labor costs are rapidly increasing in China, rising up to 25% a year in some industries. As labor costs climb, and an increased push is made by the Chinese government to modernize the recycling industry, a huge opportunity may develop for equipment manufacturers to sell into China over the next 10 years.

New companies offering technology for flake and size-reduced sorting will emerge. Growth in flake sorting technology is the result of a number of factors. For instance, more food sorting equipment manufacturers are diversifying into the plastics industry (the same technology that is used to sort beans can be modified to sort plastic flake).

Multilayer bottles and barriers, and new types of labels will likely continue to present challenges for automated sorting equipment. The current generation of optical sorting technology largely cannot identify and segregate bottles with barrier layers. Units that claim to be able to identify barriers are beginning to come to market. PVC and PETG labels also continue to be a problem for sorting equipment, causing misidentification of PET bottles with those labels, resulting in the loss of PET in the sorting process.

Technological improvements are on the horizon for black plastics. The technology behind automated sorting systems has changed drastically in 10 years. The NIR capabilities of today are much broader than those offered by the last generation of equipment.

Despite these advancements, there remains one fraction of plastic stream that spectroscopy cannot properly identify, and that is black plastic. Black carbon, which is the most common pigment additive for black plastic, absorbs the infrared signal, or light, rather than reflecting it back, so the plastic can be identified. New technologies are being commercialized that can better identify black plastic.

All of the data is self-reported information from the manufacturers. While it is reliable, it should be verified by any potential buyer. Research for this report was conducted by 4R Sustainability (4R) with funding support from the Plastics Division of the American Chemistry Council (ACC). Msw Bug Web

More in Collection