GreenSmart Notebook - Tom Larsen

rPET polyester - Good or Great?

This week I was confronted with a possible mis-perception about rPET polyester, especially when considered for bag making (called industrial grade as opposed to textiles for apparel grade). The question at hand was essentially if one is going to make an item out of some sort of textile, “is rPET polyester a  marginally improved eco-choice or a significantly improved eco-choice”. Especially when compared to alternative materials, both synthetic and natural.

First, to understand just the minimum about textiles, woven ones anyway, you have to go back to the concept of weaving a fabric. Once any material becomes a “yarn” or “filament”, the amount of energy and conversion processes to bring that yarn to a textile are pretty consistent, whether the yarn is wool, cotton, nylon or polyester. There are incremental differences with finer or heavier materials, but, all in all, the process of weaving any textile is largely the same, a bunch of lines of yarn go in a north-south direction and they are “woven” with a bunch of lines of yarn that go in an east-west direction.

What then becomes the core variable of a look into the question above, one that I used as a basis for my GreenSmart filter in creating the Bottles 2 Bags concept, was to look at the conversion of the source material into yarn. In this way, there is a vast difference among the most commonly used materials.

Whether I consider the natural fibers and the practices that go into growing plants or critters, or I look at the synthetic fibers and the practices of converting petroleum into useful polymers, they have very different consumptions of energy and steps to the process. One way to level the awareness is to find a common denominator, in the current parlance, that’s the amount of carbon dioxide emitted to create the fibers. This may include the movement of water to irrigate crops or pastures or the heat required to separate the oil into its parts, or a litany of other work that's being done to produce the material, but, it’s a common denominator when done properly.

Although I have studied this concept over the years, I’m not a practitioner of comparative analysis using CO2 emissions (the carbon footprint). Luckily for me and all of us, there are others that are. In this case, David Morris of the International Rayon and Synthetic Fibers Industry (www.cirfs.org) a European membership organization that does the homework for the synthetic fibers industry. Yes, they have an agenda, but, you’ll understand why I trust this when you see the information, but, also, because there is no other organization pursuing this kind of question.

So here’s the deal. Check out the comparative measure of the kg (that’s kilograms) of CO2 emissions per kg of fiber for the following materials:

Nylon   9

Cotton  6

Polyester 4

Organic Cotton 2

Wool    2

PLA     2

rPET polyester less than 1

What does this tell me? First, of the synthetics, rPET polyester has almost a 90% lower carbon footprint than nylon. rPET polyester has a 75% lower carbon footprint than virgin polyester. And, amazingly, a 50% lower carbon footprint than even organic cotton.

I promised to say why I trust this analysis. The worst carbon footprints for nylon and polyester, are part of the synthetic industry’s bread and butter. By presenting data, Mr. Morris and the CIRFS have done what any respectable European organization does, present the facts. That’s not how it is likely to be done in the U.S., but, that’s a completely different blog post.

As a result of this data, to me, the ONLY choice for bag making, as long as an unlimited supply of PET exists (anyone stopped buying carbonated beverages?), is to convert that into textiles. It’s not just a very good short term solution, it may very well be a great long term solution, too. As long as we consumers want to have something to schlep our stuff around in, whatever that may be, rPET polyester is going to be one of, if not THE lightest carbon footprint available. That is, until GreenSmart finds something better.

What is rPET Polyester Fabric?

This question has been coming up lately, so why not talk about it in a blog? It's not difficult to get, it's just never explained.

rPET stands for recycled PET, the bottles that we are all familiar with used for water and soda. The recycle symbol #1. PET is Polyethylene terephthalate, a member of the polyester family, which most people don't realize. What has always been the case is that PET is the same chemistry as polyester. The difference is that a PET bottle is molded and polyester is a fiber. So in most respects PET and Polyester are synonymous. If that doesn't quite add up, you could think of dough in a loaf pan to make bread or dough in a pasta machine to make linguini. The source of both is dough, but, the result is totally different.

When anyone puts a bottle in the recycle bin, it may go back through the recycle process to become a bottle, or it may become a polyester fiber of some kind. It may come back all kinds of forms. Polyester is tremendously strong, inherently water resistant, and pretty much totally color fast. In outerwear you'll find polyester as polar fleece, in general apparel because it is lightweight and wrinkle resistant, as a component in clothing (cotton/poly blend), bedspreads, sheets, curtains and in all types household fabrics. Additionally, polyester is found in tires, ropes, conveyor belts, safety belts and lots of industrial applications.

Any one of these applications could have rPET origins, but, most don't. What makes rPET fascinating is how much energy is saved in production and of course, it consumes what would otherwise go to landfill, the bottle. So when you see something labeled as rPET, rest assured that it is a recycled material.