Packaging's role in Walmart’s Project Gigaton

Earlier this year, around Earth Day, Walmart announced an ambitious plan to work with its supply chain to reduce greenhouse gas (GHG) emissions by one gigaton. I decided to run the numbers to see what role source reduction, specifically in Walmart's packaging, could play.

First, what’s a gigaton? A gigaton is 1 billion tons or 1 billion times 2,000 pounds, which equals 2 trillion pounds of greenhouse gases, or GHGs. That represents 20 times more pounds of greenhouse gases than there are stars in the Milky Way. 

This is a serious amount of GHG reduction. Because of the scale of this goal, no one product or company can get Walmart to its goal. It will take the hard work of many companies and a multitude of products and operations to achieve.

As a thought experiment, I wondered how changes in packaging could contribute to this goal. We’ve all seen changes in packaging in past decades, especially when it comes to source reduction and use of lighter materials. One example of this shift is pasta sauce. We’re beginning to see a move to lighter-weight glass jars and to PET plastic containers. And while not common in pasta sauce, we’re seeing more sauces in flexible pouches.

Running the numbers

So, how could pasta sauce packaging contribute to Walmart’s goal? First, we need to know how much pasta sauce is sold. According to Statista, 718 million units of pasta sauce are sold in the U.S. each year. The dominant size is 24 ounces, plus or minus an ounce. Yes, there are big 64- and 48-oz jars and some smaller 12- and 15-oz packages, but 24 ounces and glass is the current consumer choice.

According to Andrew Wolf, an analyst at Loop Capital, Walmart has a 21.5 percent market share in grocery, thus we’ll assume it sells 21.5 percent of the pasta sauce in the United States. By weighing a few jars and pouches, plus checking historical weights from ULS Packaging Efficiency Reports from 2007 and 2016, we estimate that a 24-ounce package weighs:

  • Glass: 320 grams
  • PET plastic: 38.6 grams
  • Steel: 80.3 grams
  • Flexible pouch = 15.8 grams (two 7.9 gram 12 oz. pouches)

Next, we need to know the GHG emissions for the various materials. For this, we look to the source reduction values from U.S. EPA Documentation of Greenhouse Gas Emission and Energy Factors Used in the Waste Reduction Model (WARM) — Containers, Packaging, and Non-Durable Good Materials Chapters February 2016 (PDF). Essentially, this resource quantifies how much GHG emissions would be saved if a given material wasn’t produced.

  • Glass: 0.60 MT CO2e/ton of material
  • PET plastic = 2.24 MT
  • Steel = 3.67 MT
  • Flexible Pouch = 1.788  MT(assumes the pouch is a mix of LDPE, PP & PET)

Calculations are provided in the table below. What do they mean? Although steel has a small and shrinking portion of this market and is very recyclable, it doesn’t make sense to switch back. Steel has the highest GHG footprint.

Next, we can see that continuing the transition from glass to PET will more than double the GHG savings for pasta sauce packaging. If we assume all packaging is glass today and we move to PET, it would reduce almost 20,000 tons CO2e every year just at Walmart. If we look at the whole U.S. market it would result in more than 92,000 tons of CO2 being avoided every year.

Finally, our calculations show that moving from glass to flexible pouches would result in a massive 143,000 tons (167,511 – 24,623 = 142,888) reduction. Even though glass emits a lower amount of CO2 on a per-ton basis, the amount of material (or mass) required per unit of glass packaging creates a much larger overall CO2 footprint.

Now, these results make huge assumptions, such as a 100 percent shift from glass to PET or pouches. But we have seen many products shift from steel and glass to plastics and flexibles. While baby boomers are comfortable with traditional packages, millennials are quick to pick up a pouch or a carton if it will help them with convenience.

After just seven years, the switch from glass to pouches would save 1 million tons of CO2. It might seem like one little step forward in Walmart’s Project Gigaton. But consider that this is just one package.

What about all those other packages that can be optimized? Source reduction of packaging can play a key role in getting Walmart to its gigaton goal.