Life Cycle Assessment and Materiality Assessment Part 2 – Setting up the study

In Part One of this blog series we covered what a Life Cycle Assessment (LCA) is and the importance of a materiality assessment. We will now explore some of the aspects that go into an LCA.

We’ll work from the milk container example explored in Part One. Which is the most environmentally-friendly milk container option – a glass bottle, a plastic bottle or an aseptic pack?

A life cycle carbon assessment of the three different materials discloses the greenhouse gas emissions (GHG) associated with the production of the raw materials, plus the impacts of transportation and distribution. Unlike milk sold in plastic or glass, milk sold in aseptic packaging does not have to be refrigerated until it is opened. This means the use of aseptic packaging avoids the energy used to refrigerate transport trucks and the energy used in refrigerated grocery stores shelves. The rectangular aseptic packages also allow for more product transport in the truck than irregularly shaped containers and require less tertiary packaging to prevent breakage. Furthermore, aseptic packaging reduces spoilage losses of milk during transport and distribution. In addition, a shelf-stable product can remain in the grocery store longer than a refrigerated product, making it more likely to be consumed rather than discarded. These aspects are all taken into account in an LCA, but how does all of this information come together in materiality assessment?

A materiality assessment questionnaire might ask: “On a scale of 1 to 10, how would you rate the importance of each aspect of the container?” I would rate product waste as very important (10), GHG emissions as important, but slightly less so (8) and recyclability as important, but slightly less so than GHG emissions (7). Someone else might rate recyclability as very important (10), GHG emissions as middle-of-the-road (5) and product waste as not very important (2).

A life cycle carbon assessment of the production, transport and distribution of glass, plastic and aseptic milk contains reveals that the GHG emissions per 1-liter container are 265, 101 and 36 gCO2eq, respectively, for each container type.[1] Even though glass and plastic milk containers are recyclable, that doesn’t guarantee that they are recycled. According to the EPA’s website, glass and plastic beverage containers are recycled at a rate of 34% and 31.4%, respectively. Aseptic packaging is actually recyclable, but many locations in the U.S. do not accept it for recycling. According to the Tetra Pak website (a major producer of aseptic packaging), 20% of all of their cartons are recycled worldwide. Specific data on the recycling rate of aseptic packaging in the U.S., however, were not available, so a more conservative estimate is that none of it is recycled there.

Highly perishable products, like milk, are prime sources of food waste in the system, therefore it is reasonable to assume that, if the packaging does not reduce the likelihood of spoilage, an average of the 35% of food waste could apply in this case. That is not to say that milk in an aseptic pack is not wasted, but it is likely wasted at a lower percentage than 35%, around 10% as a conservative estimate.

Read Part 1 – Life cycle assessment and materiality assessment – should I cry over spilled milk.

Read Part 3 – Life cycle assessment and materiality assessment – what do the numbers mean to you?


[1] For aseptic: adding in the biogenic carbon that will eventually be released at EOL and for glass and plastic

2 responses to “Life Cycle Assessment and Materiality Assessment Part 2 – Setting up the study”

  1. Thanks for this! I’m interested to also know the comparison of returnable glass milk containers. They are offered in the area that I live in. Would that be better or worse than the Tetra Pak containers (when taking into account cooling and transportation)?

    • That is a good question! The type of milk container used and its end of life impacts (e.g., returning a glass bottle instead of recycling it), all factor into the comparative environmental impacts of packaging in general. The purpose of materiality assessment is to determine what you mean by “better or worse”. Returning the glass bottle may have lower GHG emissions than the aseptic packaging, but washing the glass bottle might use more water than the aseptic pack or some other packaging. If one is higher in GHG emissions, but lower in water consumption, which one is “better”?