|University Federico II
of Naples, Italy
Easy Rider, a trolley bag from recycled plastics
Is it possible to reutilize plastics for uses different from the original ones? Yes, it is! By recycling procedures!!
Progress is ongoing: Maybe someday we will sleep under sheets made up from recycled bottle caps....
Many commercially available objects today are obtained from recycled plastics
The first sailing boat entirely made of recycled plastics
The boat is lighter if the hull is ecosustainable.
Recycling can be done in three different ways:
1- Mechanical recycle. Have you ever heard that a sweater is made out of 10 plastics bottles, or a chair, and a freesbee from just 2 bottles? Some TV spots advertise this. How is it possible?
Both bottles and synthetic fiber (so-called "pile") sweaters are made of the same material, a polymer called PET (polyethylene terephthalate) that, processed in different ways, is able to yield either a bottle or a sweater. This is mechanical recycle: bottles are transformed into flake, a synthetic fiber which can be woven and converted to a pile jumper or to couch and car seat stuffing.
With like procedures, one can get a garden bench from just 45 plastics trays, or a Christmas tree from 31 bottles.
2- Heterogeneous recycle. Quality of recycled plastics is better if the starting material is of one kind. If it is obtained from heterogeneous plastics it is of lower value, however it is equally tough. Indeed, by recicling mixtures of different plastics (heterogeneous recycle), one obtains a "mixed" highly endurable plastic which can find unlimited uses, ranging from urban furniture (benches, wastebaskets), to building (bridges and fences), sports equipment, placards.
Another example from Japan: Toshiba has been operating for two years a plastics recycling plant, which transforms 250 kg of mixed plastics into fuel oil in 11 hours. Costs are still very high, but researchers are studying the way to make such recycling process convenient.
3- Chemical recycle. It consists in depolymerization of plastics and recovery of the starting materials ("monomers") that are used to prepare new plastics. This is nearest to the ideal "ecocompatible" recycling process, providing loop closure and no waste production.
How can chemical recycle be fulfilled?
At present all technical problems connected with plastics depolymerization and re-use of products can be solved. The critical problem lies on economic ground.
Chemical industries can find chemicals they need in the market, derived from oil at relatively low prices. Of course, they don't like to pay for recovery and selection of chemicals they can get cheaper. In other words, recycling costs are at present higher than disposal costs. Only in some favourable cases can recycle be economically convenient, for instance, when plastics scraps are collected and used in the same plant where new plastic is produced.
Another problem with chemical recycle is that it can be done only for a few materials (PET, polyurethanes, polyamides (nylon)).
Scientific researchers have to work hard in this field and propose a reasonable trade-off that balances market and environment requirements.