By Jan H. Schut
At the SPE’s Global Plastics Environmental Conference (www.sperecycling.org) in Atlanta in October, two new recycling operations were introduced along with a brand new algae bioplastic. The new recycling processes are sophisticated closed-loops for complex post-consumer materials—shredded plastic from household appliances in Japan and PVC roofing in North America–both driven initially by legislation. The new bioplastic is possibly the first directly plasticized from algae. Non-attendees can buy the papers from GPEC 2011 on CD ROM for $75.00 (email: email@example.com).
Mitsubishi Electric Corp. in Japan (www.mitsubishielectric.com) took over 10 years to develop technologies in house to recycle plastic from shredded air-conditioners, TVs, refrigerators and washing machines into 99% pure PP, PS and ABS, all used in new Mitsubishi air conditioners. Mitsubishi’s website posts English language reports on the technology, but GPEC was its first presentation outside of Japan.
The first stage of the technology is wet separation of mixed plastic flakes into three densities: unfilled PP with under 1.0 specific gravity separated by float/sink; a mixture of PS and ABS with 1.0 to 1.1 specific gravity separated by oscillating water flow; and everything heavier than 1.1 specific gravity (PC/ABS alloys, PVC and highly filled plastics) burned for energy recovery. PS and ABS are then separated from each other electrostaticly.
Mitsubishi also developed a patent-applied-for X-ray transmission separation technology (WO 2010/092645 and JP2009198387) to remove bromine-containing flake from the PP, PS and ABS, which otherwise wouldn’t comply with the European Union’s RoHS Directive. The directive restricts the presence of bromine, chiefly polybrominated diphenyl ether flame retardant, to below 1000 PPM in new electrical appliances and electronics. “We developed a line-scanning and rapid screening system using the X-ray transmittance difference of bromine content. This system can screen and separate plastic flakes 100 times faster than the florescent X-ray method,” reports Koji Hamano, manager of eco materials at Mitsubishi Electric’s advanced technology R&D center. The separated flakes pass on a conveyor at 100 m/min. between an X-ray transmitter over the conveyor and an X-ray line sensor under it. Brominated flakes transmit less radiation than unbrominated flakes and appear darker. A data processor instructs an array of 124 individually controlled air jets to remove brominated flakes. The technology won the 2010 Environmental Award from Japan’s Ministry of the Environment.
Green Cycle Systems Corp (a unit of Mitsubishi) in Chiba, Japan, opened in April, 2010, using the new process to recycle 22 million lb/yr of incoming shredded appliance plastic, yielding 14 million lb/yr of purified plastic. Green Cycle gets all feedstock from another Mitsubishi subsidiary, Hyper Cycle Systems Corp., set up in 1999 to comply with Japan’s Home Appliance Recycling Law. Hyper Cycle crushes used appliances, removes metals and other impurities, shreds the plastic into 10 mm flakes, and removes fines. The mix is 30% PP, 40% ABS and PS combined, and 30% heavier plastics.
Only a few other companies in the world tackle mixed post-consumer durable plastics, which often include WEEE (waste electrical and electronic equipment) and ASR (auto shredder residue) and are more complex. MBA Polymers in Richmond, Calif., has about 300 million lb/yr of processing capacity for mixed WEEE plastics and ASR, producing ABS, HIPS, PP, HDPE, rubber, and mixed plastics for lower-end applications. MBA assembled a proprietary series of recycling technologies, but didn’t invent the components. Mitsubishi could have bought available components too, but wanted high volumes and started from scratch.
FIRST N. AMERICAN RECYCLING OF POST-CONSUMER PVC ROOFING
The Sarnafil Services division of Sika Corp. in Canton, Mass. (www.sarnafil.sika.com), a maker of industrial vinyl roofing, is believed to be the first in North America to recycle post-consumer vinyl roofing back into new PVC roofing. Sarnafil collects used roofing in 40,000 lb truckloads from contractors installing new Sarnafil roofs. The concept only works with large roof areas, but 80% of Sarnafil’s business is replacement of industrial roofs. Contractors cut old roofing into 3 ft wide sections, roll them tightly, and pack them in reusable Gaylord containers provided by Sarnafil and collected for free, initially to support customers in areas with landfill restrictions on construction waste.
European roofing manufacturers operate a similar closed loop recycling program for members, called Roofcollect (www.roofcollect.com), of which Sarnafil’s Swiss parent Sika is a member. Roofcollect has been active for over 10 years and reports collecting over 3 million lb of post-consumer PVC roofing in 2010. Sarnafil, which started its program in 2005, will recover close to 600,000 lb of post-consumer PVC roofing this year, using the material as a mineral filler at up to 4.5% in the back ply for new vinyl roofing. Several of Sarnafil’s customers have won awards for participating, but GPEC was the first presentation of the program itself.
Sarnafil’s post-consumer roofing is recycled on a toll basis by Norwich Plastics in Cambridge, Ont. (www.norwichplastics.com), which has specialized in post-consumer PVC recycling, primarily from wire and cable, since the 1980s. Norwich almost turned down the job at first because of the cross-linking challenge. Post-consumer PVC roofing is all different durometers based on age. Roofs are exposed to extreme UV radiation, so over time thermoplastic PVC cross-links and doesn’t melt any more. Sometimes roofs are replaced that are under 10 years old and still have good melt properties; sometimes roofs are so old and brittle that they are just mineral filler and backing; and they can be anywhere in between.
Norwich tests each incoming lot for durometer, washes the roofing, then grinds and elutriates it to remove fluff from old polyester backing. Initial testing, grinding and elutriation are done at any of several Norwich plants, based on proximity. Ground and elutriated material then goes to Norwich’s Woodstock, Ont., plant to be cryogenically ground a second time into 20-mesh powder and blended for uniform properties. Norwich has also begun compounding and pelletizing post-consumer powder with pre-consumer PVC into masterbatch with about 30/70 post-consumer and pre-consumer PVC. Sarnafil says this should enable them to increase recycled content in new roofing.
NEW SOURCE OF ALGAE PLASTIC
Algix LLC in Bogart, Ga. (www.algixllc.com), is blending high-protein-content algae with thermoplastics to make new bioplastics for disposable and durable applications. A spin-off from the University of Georgia in Athens, Algix co-owns patents on algae technology (relating mostly to biofuels) with the university and licenses the concept of direct plasticization of algae from Kimberly-Clark Corp., Dallas, Texas (www.kimberly-clark.com). Kimberly-Clark’s patent-applied-for technology (U.S. Pat. Applic. # 20100272940) focuses on blends of thermoplastic algae and polymers like PE or polyesters.
Algix and Kimberly-Clark aren’t the only companies to blend algae directly with thermoplastics. Cereplast in Hawthorne, Calif. (www.cereplast.com) in early 2009 announced plans to commercialize up to 50/50 blends of algae and PP when sufficient supplies of algae biomass became available. Cereplast sources dried algae as residue after extraction of oils from the algae. Kimberly-Clark’s patent also refers to future algae fuel production as a possible source.
Algix, however, is working on a different source. Ryan Hunt, director of R&D at Algix, wants dairy farmers to raise algae as a new cash crop, while remediating water runoff. Instead of causing algae blooms in local ponds and streams, farmers can use a commercial remediation system called an Algal Turf Scrubber, available from HydroMentia Inc., Ocala, Fla. (www.hydromentia.com). It has a large 3.5 acre PE mat graded at a slight 2-degree angle, over which polluted water flows constantly. In about a month a thick mat of algae grows, which can be removed by a tractor pulling a scraper. Mats of algae are currently composted, landfilled, or fed to cattle. Algix wants to make them into bioplastics.
Algix works with Ven Consulting LLC in Melbourne, Fla. (www.venconsultingllc.com) to harvest, dry and mill algae biomass for conversion into plastics. The best protein sources, Algix says, are two micro algae, Chlorella vulgaris and Spirulina Platensis, and filamentous algae and macrophytes from the Lemna and Cladophora genuses. Chlorella is 55 dry wt % protein, 15% starch, and 18% fat with low ash and fiber. Spirulina is 55% protein, 11% starch, and 5% fat, also with low ash and fiber. Cladophora can have up to 40% protein, 20% fiber and 30% ash. Kimberly-Clark’s patent also describes plasticizing a third micro algae, Nanochloropsis, a popular strain for algal oil production. All are less than 115 microns in size. Research at the University of Georgia has also shown that nano-cellulosic fibers from Duckweed have similar performance to aramid fibers (Kevlar).
Pure algae plastic made by compression molding is hard like PS, but brittle. Algix blends powdered algae with powdered HMW HDPE (53-75 micron) with a melt temperature of 144 degrees C, and glycerol as a plasticizer for flexibility. Algae biomass burns at 200 degrees C, which limits formulations to polymers with melt temperatures below 190 degrees C. Algix presented data on compression molded blends of 30/50/20 HDPE/algae/glycerol, but has tested over 30 formulations for extrusion compounding and injection molding, including blends of algae and macrophytes with PLA to make 100% bioplastics. Compounding was done on a 21-mm-diameter Theysson twin-screw extruder in the Polymers Center of Excellence (www.polymers-center.org) in Charlotte, N.C.
Algix’s algae plastics are black or dark brown, unless made into thin film, which can be blue green. Cereplast’s compression molded algae plastic from biomass after oil extraction is olive green. Algix still needs to overcome problems with color and odor. Kimberly-Clark’s patent describes bleaching algae to produce off-white or light yellow plastic. Cereplast reports that it has solved the odor problem. Chlorella smells earthy, Spirulina smells like fish food, and macrophytes smell like fresh cut grass when processed. Algix’s target price for finished algal bioplastics is $1/lb. It is looking for strategic partners for scale up and distribution.
Several student posters presented at GPEC 2011 reflect the same themes, notably “Algae biocomposites produced from biomass co-product” by Alejandra Constante from the University of Alabama at Birmingham; “Duckweed Aquatic Macrophyte with the Potential for Sustainable Materials Production” by Renuka Dhandapani from the University of Georgia, Athens (the same group that spawned Algix); “Morphology and properties of thermoplastic sugar beet and PLA” by Peng Zhan from Washington State University, Pullman; and “Bio-renewable Carbon fiber precursor from lignin” by Keke Chen from Iowa State University, Ames. Information on student posters can be downloaded from http://www.sperecycling.org.