The primary purpose of the Dragonpipe (Mariner East pipeline system) is to transport ethane for the production of single-use plastic by European refineries. Sunoco has never seriously disputed that. Ethane is the primary component of the highly volatile “natural gas liquids” (NGLs) carried by the system, and the petrochemical giant Ineos commissioned eight “dragon ships” specifically to carry ethane to its refineries in Scotland and Norway, where it is converted to ethylene for the manufacture of plastic.
But the capacity of the pipelines, stated in “barrels per day”, doesn’t really provide a sense of the quantities of plastic that will result from this ethane flow. That’s what I want to do in this post. Instead of “barrels per day”, I want to provide a sense of the volume in “plastic bottles per day”. The volume, when stated in terms of plastic bottles, is almost unbelievable.
This calculation is meant to be illustrative, and it involves several simplifications that I want to state right up front. Here are the main ones:
- Ethane isn’t the only highly volatile NGL being transported (although it is the most abundant). I will focus on ethane because it is the predominant product and because it is almost exclusively used for making plastic. The other NGLs (propane and butane) have additional uses. Sunoco doesn’t reveal what fraction of the system’s final capacity will be used for carrying ethane (and that depends to a large degree on its customers), but I am assuming that it will be 45% ethane, since that is roughly the proportion of ethane present in the NGLs that emerge from the wells in western Pennsylvania.
- Ethane is used to make three kinds of single-use plastic (polyethylene, vinyl, and polystyrene/Styrofoam). The largest volume, by far, is polyethylene. For simplification, in this calculation I am assuming that all the ethane is used for making polyethylene.
- Not all polyethylene is used for bottles. It is used for many forms of single-use packaging, but bottles are the most common and familiar one.
Given these simplifications, it would be more accurate to say that this is a calculation of the pipeline system’s capacity in terms of “equivalent number of polyethylene bottles per day, if all the ethane were used exclusively for polyethylene bottle production”. But that’s too much of a mouthful, so let’s just call it “plastic bottles per day”.
So how many plastic bottles per day could be made using the Dragonpipe’s ethane, at full planned capacity? The approximate answer is 971 million bottles per day. Think about it: enough ethane for almost a billion bottles, every single day. (For those who want to check my arithmetic, it is available at the bottom of this post.)
That’s the equivalent of 3 bottles for every man, woman, and child in the entire US, every day, 365 days a year.
Could this estimate be off? Of course it could. It might be off by 100 million bottles in either direction. But no matter what, we are talking about the production of something in the vicinity of a billion bottles-worth of plastic every day.
Let me reiterate (because I know there will be criticism of this calculation): I do not claim that the Mariner East ethane will be entirely used for plastic bottles. But it will be used entirely for single-use plastic items (many of them bottles). Thinking of the ethane in bottles-only terms is a useful way to visualize the magnitude of the flow and the volume of plastic produced.
Is it any wonder that landfills around the world are overflowing and rivers and oceans everywhere are being poisoned with single-use plastic? This is yet another reason why the Mariner East system, even more than any other pipeline in our area, needs to be shut down.
I want to express my gratitude to Linda Yu, candidate for Township Supervisor in Edgmont Township, Delaware County. It was Linda who had the brilliant idea of stating the Dragonpipe’s capacity in terms of plastic bottles. And I am grateful to Todd Speese, the engineer who helped gather the data for the calculations below, and who reviewed the calculations for me. Any errors, however, are completely my responsibility.
How I calculated “polyethylene bottles per day”. For those of you who are really interested, here are the details of my calculations. I started by calculating “bottles per barrel”, since Sunoco states its pipelines’ capacities in barrels.
- 1 barrel = 159 liters
- Weight of ethane at room temperature = 0.41kg/liter
- Multiplying these two values to get the weight of a barrel of ethane = 64.82kg
- Because ethylene is only 93.3% as heavy as ethane, and because the conversion process is only 60% efficient, a conversion factor of 0.56 must be applied to get the weight of ethylene, given the weight of ethane.
- So the ethylene derived from a barrel of ethane weighs 64.82kg x 0.56 = 36.3kg
- There is no weight change when ethylene is polymerized into polyethylene.
- A typical plastic bottle weighs about 10g, so 1kg of polyethylene yields about 100 bottles.
- Therefore, a barrel of ethane can produce 100 x 36.3 = 3,600 bottles.
How many barrels/day of ethane will the Dragonpipe carry? The remaining value needed to complete the calculation is the number of barrels of ethane per day carried by the Dragonpipe system. This is a moving target, since Sunoco has given different numbers at different times. But we can get a fair approximation.
Let’s start by calculating the overall capacity of the pipelines for all products. Currently, Sunoco is saying that Mariner East 1 carries 70,000 barrels per day. Mariner East 2 will carry 275,000 barrels/day “upon full completion”, which Sunoco now claims will be in 2020. (The company says there is the “capacity to expand further as needed”, presumably by adding pumping stations and/or increasing pressures.) Sunoco has stopped giving any capacity numbers for ME2x, but it has previously given 250,000 barrels/day. Adding these together, you get a total capacity of 595,000 barrels/day (without expansion of ME2).
Not all of those barrels will be ethane, of course. Currently, ME1 carries mostly ethane, and the so-called “ME2” cobbled-together pipeline carries only propane and butane. But ultimately, all three pipeline systems will carry whichever products Sunoco’s customers require. For this blog post, I have chosen to assume that the products carried will be in the same proportion as they emerge from the wells in western Pennsylvania. Ethane is the most abundant. It comprises about 45% of the NGLs coming from western PA wells.
Just to be clear: NGLs comprise a minority of the gas from these wells. The majority is methane (ordinary natural gas). But once the methane is removed, ethane is about 45% of the NGLs that remain.
So let’s assume that the Dragonpipe system will carry 45% ethane. 45% of 595,000 barrels per day is 268,000 barrels/day. And, given that each barrel produces 3,600 bottles, those 268,000 barrels provide the raw material for 971 million bottles.