Do Plastics Belong in Green Buildings?
Our lives are surrounded, engulfed, saturated in plastics, from the seats in our vehicles to the cellphones at our hips, to the keyboard beneath our fingertips. But this wonder material also has a dark side. It hangs around long after its service life as a manmade object is over.
With discovery of the vast, floating waste dump known as the Pacific Gyre a couple of years ago, we're beginning to understand that plastic is not the "forever" material that we once imagined. Plastic bottles and vinyl deck chairs don't last for centuries--far from it--but the polymer molecules they're made of do. And those molecules can enter the food chain at a very low level, finding their way into our bodies.
What happens next? We're just beginning to find out. We know, for example that plastic water bottles leach hazardous chemicals, and that canning companies have been using similar material to line the inside of their metal cans. Plastic also has many other drawbacks, not least of which is the perception that it's a "throwaway" material. Despite the hype, a very small percentage of plastic is recycled. And some materials--notably PVC, one of the most problematic of all plastics--have almost no recycling prospects.
On the other hand, plastic composites have been one of the most promising building advances to come along in decades. I put an HDPE-based deck on my house five years ago (CorrectDeck), and it looks much the same as it did the day I installed it, aside from a few mold blotches.
Of course HDPE is a more stable form of plastic--and one that's easier to recycle. Therein lies the a new way of thinking about plastics. Manufacturers must stop treating plastics as if they're all created equal. Some are more stable, more durable, and less potentially toxic than others. The chemists have already done the research. It's time for the industry to phase out more dangerous plastics such as PVC, and base their composite offerings on thorough life-cycle analysis--not the bottom line.
The image above shows how plastic recyclers identify various types of plastics. Ecolect offers the following definition of each type of plastic--a helpful first step in identifying which plastics to include in future green products:
2 - HDPE High density Polyethylene : HDPE is also a readily recyclable plastic that can be found in numerous household products and is recycled in most curbside programs. It is primarily used for heavier packaging such as detergents, bleach, milk containers, hair care products and motor oil. It can be recycled into more bottles or bags, recycled into toys, piping, plastic lumber, rope, pens, and drainage pipe.
3 - PVC Polyvinyl Chloride: PVC is an abundant yet difficult plastic to recycle, and can be a major environmental and health hazard. The production of PVC releases toxins and other persistent organic pollutants into the air and when burned releases hydrogen chloride gas that is fatal when inhaled. PVC is used in pipes, toys, furniture, packaging, wire jacketing, and windows.
4 - LDPE Low-density Polyethylene: LDPE lacks the stiffness, hardness and strength of HDPE do to its lower density, yet it is very ductile. LDPE is used for many different kinds of wrapping, squeezable bottles, grocery bags, sandwich bags and clothing, LDPE can be recycled back into many its original products and is commonly used in curbside recycling programs.
5 - PP Polypropylene: PP can be used in bottles, tubs, caps, straws, rigid containers like Tupperware and fabric for clothing. It can be recycled into fibers, bins, pallets, and trays.
6 - PS Polystyrene: PS (Styrofoam) can be used in cups, foam food trays, packing peanuts. Polystyrene can be a real problem as it's bulky yet very lightweight and not always cost effective to recyclers. Discarded polystyrene does not biodegrade, and its low scrap value does not lend itself to widespread use in curbside pickup programs.
7 - Other: These could be a mixture of any and all of the above, or plastics not readily recyclable such as polyurethane. Compostable plastic made from corn, bagasse, or potatoes is also labeled as number 7 as it doesn't fall into any other categories. Many recyclers avoid plastics labeled as #7 and deem them destined for the waste stream. Other types of #7 plastics include acrylic, PLA, polycarbonate, nylon, fiberglass, and others. This category contains many thermoset plastics that cannot be melted down once they have been cured.