The Dragonpipe (Mariner East 2 pipeline) carries fracking byproducts, mostly ethane, from western Pennsylvania to Marcus Hook, for shipment to Europe. There, the ethane is converted to ethylene which, in turn, is made into plastic. Several people have asked me about the resulting plastic products, so here’s a run-down.
The cracking process (technical details—feel free to skip this section). For all the ethane-based plastics, the first step is “cracking” the ethane to produce ethylene. This process, which involves very high temperature steam, is done in a large refinery (a “cracking plant” or just “cracker”). For efficiency, the scale has to be huge. These plants cost billions of dollars. In the US, they are almost exclusively located in Texas and Louisiana, near the traditional sources of oil and gas supply. There are no cracking plants on the east coast (but if the Dragonpipe is built, we may eventually get one in Marcus Hook).
Ethylene has a double bond connecting its carbon atoms (which ethane does not). The double bond allows it to be used in a variety of chemical reactions. Three of these reactions are used to make different types of plastic: polymerization (to make polyethylene), halogenation (to make polyvinyl chloride), and alkylation (to make polystyrene). The most common plastic items we use are all made from one of these three types of plastic.
Often, the type of plastic in an item can be determined by looking at its “recycling triangle” code, which contains a number that identifies the plastic.
Polyethylene. Polyethylene comes in several variations distinguished by density. Products made of polyethylene are marked by a “1”, “2”, or “4” recycling code. These products include plastic pipes, toys, bottles, food packaging, tubing, and sporting goods.
Grocery bags and packaging film are also polyethylene, but they can’t be recycled in the same way as solid items, so they don’t carry the recycling code and should be taken to a store for recycling. Heavier-weight plastic bags, often with printing, are usually polyethylene too, but they generally can’t be recycled at all.
Polyvinyl chloride. Polyvinyl chloride (often called “PVC” or just “vinyl”) is identifiable by a recycling code of “3”. Among the products produced using it are plastic pipe, bottles, credit cards, electrical insulation, signage, records, “blister pack” display packaging, and inflatables.
Polystyrene. The recycling code for polystyrene is “6”. It is used for plastic cutlery and toys and for “styrofoam” (packaging peanuts, restaurant take-out boxes, and the like).
Plastic that is not made from ethane. All of the above are made from the ethane carried by the Dragonpipe. So what’s left? The major remaining plastic category is polypropylene, code “5”. It also made by cracking, but propane (not ethane) is the starting material in this case. It is used primarily for plastic dishes, food containers (such as yogurt containers), and auto parts.
Then there are a variety of other, more specialized plastics, such as acrylic, nylon, and polycarbonate. They carry the recycling code “7” but are generally not recycled.
We need to get serious about reducing the amount of plastic we use. Recycling is a good place to start, but it is not enough. As people in the path of the Dragonpipe have learned, the ingredients that go into plastic (like ethane) are risky to transport and store, and the end products are damaging our wildlife and our oceans.