Is glass better than plastic?

Published: October 11, 2020

Environmental Impact of Glass Vs Plastic

In the last post, we talked about the sustainability of raw materials used to make glass bottles and containers and talked about how many times glass can be recycled. 

There was some nuance to that conversation because even though glass is infinitely recyclable, virgin raw materials are always consumed in every new batch of glass made.  If you missed that post, it's definitely one worth reading:

In this post, we're jumping in with both feet with a big question.  Is the carbon footprint of glass bottle manufacturing really smaller than the carbon footprint of plastic bottle manufacturing?

Energy Required to make Glass & Plastic Bottles

To answer that question, we have to know how much energy it takes to make a bottle.  You'll notice I've limited this discussion to just two types of plastics - polyethylene, both high density and low density, and polypropylene.

There's a reason for that - namely, they're the plastics we use at Rain Organica.

 Material

Energy of Bottle (Jar) Production

Glass

16.6 MJ/kg

Polyethylene (HDPE or LDPE)

77 MJ/kg

Polypropylene (PP)

69 MJ/kg


The energy requirements suggest that glass packaging is much less energy intensive to create, but this overlooks the fact that glass packaging is HEAVY.

Why does that matter?  Well, you'll notice the energy is listed in terms of MegaJoules per kilogram, so the energy is normalized on a weight basis (yeah, don't worry, I'll stop talking statistics talk here, but normalized IS important, and anytime anybody's trying to fool you with data, make sure they're speaking in terms of normalized data - it matters, and here's why:

A 4 ounce glass bottle is just over four and a half times heavier than a comparable 4 ounce polyethylene bottle.  This means that roughly the same amount of energy is required to produce a glass bottle as a polyethylene bottle.

Yeah, I know.  TOTALLY NOT the answer you were wanting.

Carbon Footprint of Glass vs. Plastic Containers

Since coal is really dirty, let's just assume coal is used for all container production because it's just the dirtiest type of electric generating 1000 g CO2 (a full kilogram aka 2.2 pounds) emitted per kiloWatt hr (kWh). 

You'll notice energy in the previous table is listed in terms of mJ and here, we're talking in terms of kilowatt hours, don't worry, here's the conversion:  1 kWh = 3.6 MJ (megaJoules).  And, I did the math for you in the table below.

Pulling that table down again from above and adding one more column shows the amount of carbon emitted for glass and plastic packaging on a weight basis.

 Material

Energy of Bottle (Jar) Production

kg CO2 emitted per kg of bottles  made

bottles made per kg* kg CO2 emitted per bottle

Glass

16.6 MJ/kg

4.6

8 0.56

Polyethylene (HDPE or LDPE)

77 MJ/kg

21.4

32 0.67

Polypropylene (PP)

69 MJ/kg

19.2

32 0.60

 *assumes we're making 4 ounce bottles (or jars)

When we break it down by the amount of carbon emitted per bottle made, the carbon footprint of glass is painfully close to that of a plastic bottle. And, here we're only looking at carbon emitted during manufacture and not carbon emitted during shipping the bottles after they're made.

We'll take a closer look at shipping in an upcoming post.  In the mean time, I hope you'll swing back and take a look at the environmental impact of glass manufacturing.

Did you know Rain Organica offsets its carbon footprint?  So far in 2020, we've purchased 4 tons of carbon offsets.  If you prefer eco-friendly products, be sure to shop our site for your skincare needs and follow us on Pinterest.

Brandy Searcy founder Rain Organica

About the Author

Brandy Searcy is an outdoor girl who loves hiking, gardening, bird-watching, and body boarding.  Her innate curiosity means she's constantly researching something, and she's likely sharing what she's learned here on the blog. 

Nearly obsessive about her skincare, she started developing products to pack with her on day hikes and soon realized her backpacking friends were searching for a portable skincare routine as well, and that's how Rain Organica started.

Brandy's LinkedIn Bio

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