Citrus-gel method lowers barriers to recycling polystyrene foam.

Foamed PS just became easier to recycle thanks to a citrus-based solvent that reduces the foam's bulk by 90% and converts it to an easily transported gel. The solvent and plastic can later be separated by evaporation so that both components can be reused. No dangerous chemicals are involved and no hazardous waste is produced, according to Harvey Katz, CEO of the new firm International Foam Solutions (IFS), Inc., Boca Raton, Fla. His patented method readily handles PS packaging contaminated with food waste, paper, or other plastics and eliminates the expense of washing and sorting, Katz reports. The system also recycles solid PS articles such as disposable knives, forks, and spoons, and even video cassettes.

According to Katz, his "polygel" technology makes it economically feasible for any business or institution that generates substantial amounts of PS waste to densify the waste on site and dispose of it at no cost. Using Katz's concept, recyclers would pick up the densified PS waste for free and transport it at their own expense to their facilities. There they would reconstitute the polymer, which comes out virtually as good as new, and then resell the solvent to IFS to help defray costs. Neither the waste generator nor reclaimer needs major capital investment to get started. Katz hopes to establish a network of PS-recycling joint ventures around the country that will utilize his technology. He plans to start with a demonstration plant to be set up in the vicinity of Fort Lauderdale, Fla., within a few months.

ALL-BIODEGRADABLE SOLVENT

IFS (which is moving this month to a larger facility in Delray Beach, Fla.) supplies both the solvent, called Styro Solve, and a densification device called the Solution Machine. Styro Solve is a blend of natural terpenes derived from oranges, grapefruits, and limes, together with a small amount of a biodegradable ester. The main active ingredient is d-limonene derived from citrus peels. It kills bacteria and viruses, Katz says, but it generates no hazardous fumes and is at worst mildly irritating to skin or eyes. Rubber gloves are not required, Katz notes.

The Solution Machine, which comes in several sizes, consists of an enclosed granulator that chops the PS waste and simultaneously sprays it with a mist of Styro Solve. At a ratio of 1 lb of solvent to 6-8 lb of PS, the mixture takes on the consistency of gelatin and a mild citrus odor. The gel is stored in a simple trash bag in the base of the machine. One bag holds at least 15-35 lb of densified PS, the equivalent of 300-400 meals worth of plates, cups, forks, and spoons.

A small Solution Machine, such as would be suitable for installation in a school cafeteria, could digest 15 lb of plates plus 11 lb of flatware and 6 lb of cups and dessert plates - enough for 400 students - in less than 5 min. A larger unit can densify 2000 meals worth of PS waste in the same time. An industrial-size unit can process 550 lb/hr of solid PS or more than 2000 lb/hr of foam.

In addition to school cafeterias, potential users of the Solution Machine include university and business cafeterias, sports complexes, airlines, caterers, hospitals, nursing homes, grocery stores, military bases, cruise ships, automotive and other manufacturing plants that use PS-foam packaging, construction sites that use foam concrete forms, and fish and produce markets. (For example, the Tokyo fish market reportedly uses 10,000 lb/day of PS-foam fish boxes.)

HOW TO GET THE PLASTIC BACK

PS can be reconstituted from the gel in at least two ways. In one successful trial run, the polygel was devolatilized in a twin-screw compounding extruder and then pelletized. A second method is to dump the gel into a hot (108 F) vat of pure Styro Solve. The gel becomes liquefied, permitting food, paper, and other plastics to be strained out. Ink from printed packaging floats on the surface of the liquid.

After filtration, the liquid is pumped through small spinnerette nozzles submerged in a bath of alcohol. From the thin liquid streams that emerge from the spinnerettes, the Styro Solve immediately dissolves into the surrounding alcohol bath while the PS precipitates into solid spaghetti-like strands. A conveyor belt draws the PS strands out of the alcohol bath and into a drying oven, followed by a dicer. The PS suffers only slight degradation of molecular weight, Katz claims. Tests at a major packager reportedly showed a change in MFR from the polymer's original 2.5 g/10 min to 3.3 g/10 min after reclamation.

Meanwhile, the alcohol can be distilled at 128 F to separate it from the Styro Solve, which boils at 208 F.

WHAT IT COSTS

Two sizes of Solution Machines suitable for cafeterias and commercial kitchens cost $4000-5000 to purchase or $100-120/month to lease. An industrial-size gelation unit costs $12,000 and up or it leases for $375/month.

Styro Solve typically costs $2730/gal (8 lb), which can gel 48-64 lb of polystyrene. That comes out to a solvent cost of roughly 44-60 [cents]/lb of PS. Offsetting this cost to the waste generator is the elimination of polystyrene trash-hauling expenses.