MBA Polymers, based in Richmond, Calif., has gained a reputation for operating some of the world’s most advanced plastics recycling plants. The company has a test facility in Richmond as well as joint venture operations in Austria with partner Muller-Guttenbrunn GmbH and in China with partner Guangzhou Iron and Steel Enterprises Holdings Ltd. (GISE). Most recently, MBA has selected a site in the United Kingdom for a facility in partnership with European Metal Recycling Ltd.
MBA Polymers recovers marketable plastics from complex waste streams, including shredded household appliances, computer and business equipment and automobiles. The company has developed a proprietary process to recover and separate these high-value plastics from each other and from residual materials. The result, according to the company, is plastic that can be recycled and used in making new durable goods.
While MBA has found success in recovering plastics from shredded streams of mixed materials, its progress in this area has involved a good deal of time and proprietary technology. “In our case, we’ve spent 15 years and tens of millions of dollars to develop it,” Michael Biddle, founder and president of MBA Polymers, says of the technology MBA employs. “You can image with that type of time and financial investment, we are rather protective of it.”
Biddle is willing, however, to discuss the difficulties associated with sorting plastics from waste electrical and electronic equipment (WEEE).
Recycling Today (RT): What are the most popular techniques employed in sorting plastics from waste electrical and electronic equipment (WEEE)?
Michael Biddle (MB): I believe that if you consider the entire world, then it would be a combination of hand sorting and density sorting.
Hand sorting is mostly used in developing countries with low labor rates and is most effective at removing non-plastics from the plastic “residue” that typically comes from the recycling of WEEE, such as metals, foils, film, paper, foam, cardboard, wood, rubber, glass, stones, sand, dirt, etc.
Hand sorting or even vision [sorting] is often attempted for separating plastic bottles and other human or machine recognizable items, but this is very difficult for WEEE. Any plastic part can be many different types of plastics. Any plastic also can be any color. Spectroscopic techniques, such as NIR (near infrared), are used for automated bottle sorting and have been offered by a number of equipment suppliers for WEEE, but these separations are limited to light colors and also are imperfect. (For more information on optical sorting technology, see page 54).
Some recyclers might try to sort plastics by the “feel” of the plastics, how it sounds when dropped and/or by using a “burn and sniff” technique. These can have reasonably high success rates in concentrating different material types depending on the skill of the “sorter,” but it is certainly not foolproof, and the last technique is not recommended for obvious health reasons.
Many WEEE parts have molded-in labels identifying the type of plastic… However, there are a number of limitations for relying on this sorting method:
- The labeling must be correct. Most recyclers know that part labeling is often incorrect due to the molder forgetting to change the label after a material change and the molder substituting the specified/labeled material with another material happens much more often than one might think.
- You must find the label and this can take time.
- If the parts are shredded through an automated recycling approach to recover the metals, which is how the majority of WEEE is recycled in the world, only some of the plastic pieces will have the labels.
RT: How can density-based sorting best be put to use in the recovery of plastics from WEEE?
MB: Many recyclers use density sorting to create “enriched streams of plastics.” For example, polyolfefins (polyethylene and polypropylene—PE and PP) are less dense than water. Higher density solutions are often created with various salts such as sodium chloride (table salt), and some recyclers attempt to recover plastics such as PS (polystyrene) and ABS (acrylonitrile butadiene styrene) using higher density
separations.
The advantage to density separations is that the technology is well known, and various types of density sorting equipment are readily available.
The biggest drawback to density sorting is that all plastics cover a density range, not a single density, and there are many plastics with overlapping densities. Unlike metals that have very large density differences, most plastics have very similar densities. The overlap problem is exacerbated by the fact that most plastics contain a variety of additives, fillers and pigments that broaden the density range at which any plastic might appear. Other drawbacks to density separation include:
- Common contaminants appear at broad and overlapping density ranges, especially wood and rubber.
- Not only do plastics have wide ranges of additives, they can have various degrees of porosity, intentionally (in structural foam, for example) or unintentionally. This can dramatically change the density of the plastic part or fragment.
- It’s a wet process, so this increases the complication of the sorting operation.
- Water treatment will be required to remove any contamination that entered the water from these systems.
- Many of the contaminants in typical WEEE streams can cause “foaming” of wet systems.
- You must then dry the plastics, which requires energy; and some plastics, if not fully dried, can experience degradation upon re-melting/extruding into pellet.
- Residual salts on the surface of plastics can lead to degradation.
- Corrosion of equipment is a common problem.
RT: How can optical sorting technology be employed in sorting plastics from WEEE? What are the strengths of such technology?
MB: I talked about optical sorting above. The advantages are that it is dry and can be deployed in many environments.
RT: What are the drawbacks associated with sorting plastics using optical sorting technology?
MB: The draw backs include:
- Cost
- It can be fooled by surface contamination such as dirt, oils, metal coatings, paint coatings, etc.
- It must use ejection techniques (mostly compressed air ejectors), meaning that there are functional limits to how many different sorts can be made unless many units are used (usually one or two at a time).
- Available techniques today don’t work at all or well with darkly colored plastics, and most of the plastics in WEEE, except major appliances (“white goods”), are darkly colored.
RT: How do investments in the various sorting technology compare? (Please rank them from most expensive to least expensive.)
MB: This is much too complicated to do, but the main point is that we know of no single technique that sorts plastics well enough to create plastics for reuse back into demanding applications, such as electronics, appliances and automobiles.
MBA employs many different technologies to remove contaminants and sort plastics by type and grade. And they each have an important purpose.
RT: How has the earlier market downturn affected the economics of sorting plastics from WEEE?
MB: As with metals, plastics prices have dropped significantly since their highs of last year. This makes all recycling more challenging, but still worthwhile for most materials, we believe. This is one of the reasons MBA has focused on several somewhat unique aspects from a business strategy standpoint that we believe makes it different from most plastics recyclers from WEEE (and more stable):
- We developed technology to handle a wide range of complex mixes of “residues” from the recycling of durable goods, including WEEE and automobiles. This gives us access to a wider range of raw materials.
- We sell directly to sophisticated end-users, so we are much less subject to the ups and downs of the “broker market.”
- To be able to sell to such customers, we have very strict quality requirements and, therefore, employ very sophisticated sorting, upgrading and QA (quality assurance) technology. To pay for this investment, we build at large-scale to get economies of scale. This is also required to sell to large customers.
- We are multinational to serve multinational customers. There are very few recyclers, especially of plastics, that have a footprint in North America, Europe and Asia.
Michael Biddle is founder and president of MBA Polymers of Richmond, Calif. He can be contacted at mbiddle@mbapolymers.com.
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