Monday, May 30, 2011

Plastic Is a Gas

The latest buzz from the big multinational bottlers is plant plastics. Giants like Coke and Pepsi have unleashed a flurry of press releases touting this "green" invention. And self-professed green blogs eat up the writings of PR/marketing departments as fact. Or worse, misunderstand the facts, spreading misinformation.
From -- in an article that gets
its facts badly wrong about Pepsi's new product
So is this invention actually green? Set aside the logic of locking nature's nutrients and compost into polymers that nothing in nature will break back down. Just look at the argument that plastic from plants reduces our use of fossil fuels.

Since plastic is petroleum-based, switching to plants will free us of a major source of petroleum dependency, right?


There's a lot of confusion & spin about this, and it's time to clear that up. #1, #2, #4, and #5 plastic comes from ethane. Ethane is a waste by-product found in natural gas fields and oil wells. It is a volatile, hot-burning natural gas. It is so unstable burns so hot that, by U.S. & UK law, it must be separated and removed from the methane that constitutes "normal" natural gas before that methane is piped around the land. And we've all seen images of oil refineries flaring off gas:
Gas flare in Thailand
(picture from Wikimedia Commons)
That's ethane (p. 6 in the PDF file). It's so useless to this refiner that it's just burned right into the air. Junk.

As the plastics industry was being born in the years leading to World War II, someone learned that ethane can be converted to ethylene (and propylene) by steam-cracking. Basically, a hydrocarbon like ethane is mixed with steam, then flash-heated in an oxygen-free furnace to a very high temperature. By tweaking the temperature & hydrocarbons, you can come out with a whole laundry list of petrochemicals. But most of what you get is ethylene & propylene. These can then be polymerized into the polyethylene that makes up #1, #2, and #4 plastics, or the polypropylene that makes up #5. **

At last, some refiners finally had an outlet for all that ethane. (Though as the picture above makes clear, the world still produces far more of it than can be used.)

In short: Nobody drills an oil well to make plastic. Nobody fracks a gas field to make plastic. Plastic comes from the unavoidable, and otherwise mostly unusable, waste by-product of fossil fuel refining. If plastic were suddenly, miraculously removed from the world tomorrow, not one well or field would close shop.

Steam-cracking is energy intensive. There's an agument that getting plastic from plants is less so. That somehow this reduces fossil fuel use. There's two problems with this line of reasoning:
  1. The science is secret; there's no way to know how much energy it really takes to convert plant matter all the way into polymers.
  2. There's also no breakdown of how much energy it takes to grow the plant material. Agriculture is extremely energy intensive. Stocks must be planted, fertilized, weeded, watered, harvested, dried, processed, transported -- all of which is only to make yet another plastic bottle.
Creating plastic from plants is not about being green, being responsible. It's about being seen as green & responsible. So far, traditional journalism has been far too complacent in helping the process. Don't get fooled.

** Ethylene is also a precursor to creating PVC (#3 plastic), and ethane is now even being used to create styrene, from which #6 plastic, polystyrene, can be produced.


  1. We as a Family living in Wales UK, go to Clear the Rubbish left behind on our Beaches. It's totally Necessary to Clear And Need to get this Message across - so Peeps don't leave it ! A Great Blog ! Love it All X x

  2. Here's a thought...if it was indeed cheaper... manufacturers wouldn't be using a maximum of 30% plant product. I honestly think they do it just to be able to tout "greenness"... the little extra money (or equal amount spent) to make people think they're doing good is (in my opinion) probably worth it for them... hmmm....

  3. I just started researching this to write a blog post in the next few weeks.....Great article! Thanks for the info. :)

  4. Danielle, a lot like dropping a few bucks at the Marine Debris Conference to help keep the term "marine debris" instead of "plastic pollution." (Odd fact: In researching it, I found that gov't actually bravely used to called it "marine plastic pollution" in the 1980s, until dumbing it down as with "marine debris" in the 90s.)

    GGGG, I'll keep an eye out for your post! People deserve to hear the facts instead of a PR machine.

  5. Hi, I read an article saying that plastic companies had spent a fortune on PR to get the general public to call plastic pollution , marine debris instead of plastic pollution. I was looking for the link to that article and landed here on your blog, so I stopped to say hello before I continue on with my search. Hi!