Evaluating alternative products is key and unavoidable when we want to replace ones with better environmental performance.

Usually, the process entails having to consider more than one aspect – product performance may be key but there are several other.  To have the environmental aspect comprehensively covered, we use life cycle assessment (LCA), which is considered the ‘holy grail’ for that purpose.

The results of such an assessment do not lie, as it provides an absolute answer considering scientific facts. Yet, we may need to interpret it correctly for our purpose and ask the correct questions from the specialized practitioners who perform it, to ensure that it covers all the angles of a product evaluation that we intend to cover.

Let’s take a popular product evaluation problem – An everyday product which we collectively call – grocery bags.

What are the product alternatives?

There are many types of grocery bags in the market, and some are for single-use while some are reusable.

Following are some of the most popular types of grocery bags among consumers.

What do the life cycle assessment results say?

Many LCA studies have been conducted with a combination of alternatives of different types. Most of the results indicate that LDPE and HDPE bags have lower environmental impacts compared to other alternatives. This may seem counter-intuitive and contradict our general understanding, as there are several negative associations made with “plastic” specifically.

Here are some facts and results:

• In a life cycle assessment that was conducted in Denmark (2018) it showed that the environmental impact of reusable low-density polyethylene (LDPE) bags was less than other alternatives, such as
• A similar assessment that was conducted in the United States (Kimmel, 2014) concluded that reusable LDPE bags have a lower impact compared with single-use HDPE bags
• Bags made of polyethylene (specifically LDPE and HDPE bags) have a much lower environmental footprint compared to cotton bags (which need to be used 52 times (to match the impact on climate change of LDPE bags) or PET bags (which need to be reused 8 times to match similar) (Schlanger, 2019)

At the same time, most of these studies highlight that reusing these LDPE or HDPE bags even as a liner for the waste bin (Edwards and Fry, 2011), may improve the environmental performance by a couple of fold.

In using results from the life cycle assessment, we need to critically question a few aspects in each study, in order to better compare them for decisions. The three main things would be 1) the boundary for analysis, 2) the method used and 3)the data source/s.

What are some of the other key considerations?

The reason for most plastic products (usually single-use plastic products) to be considered as “demons” isn’t to do with the product or the material itself, but the problems created with its end-of-life disposal. Litter created with these bags has not a common topic for discussion.

All or most of the studies assume that the product gets collected and goes in a recovery pathway as intended, so the impact of littering needs to be looked at separately

A study that was conducted in Spain (Civancik-Uslu et al., 2019) considered the littering scenario for the following grocery bags and developed a littering potential (LP) indicator for different types of grocery bags.

The results say a different story compared to the LCA studies we discussed above. If we have the Littering Potential and Global Warming Potential of grocery bags hand in hand, here is what we see.

Figure extracted from (Civancik-Uslu et al., 2019)

As the results suggest littering potential is highest in LDPE and HDPE bags as the litter gets accumulated in the environment and waterways causing environmental damage which goes unaccounted in LCAs.

While litter is completely a man-made, behavioral problem, which has nothing to do with the material itself, the flaws in behavior and the collection systems lead to a bad perception created about LDPE bags overall.

What else should we consider?

Here are a few other aspects we need to consider when interpreting LCA data in combination with other aspects to reach a decision.

1. Do the bags have reuse potential and are they actually being reused?

In the above study by (Civancik-Uslu et al., 2019) LDPE is assumed to be reused 10 times, whereas the actual times reused is much lower in real life. That makes their littering potential even higher.

Having reuse potential comes with the responsibility to design for reuse and pass on that information to the consumer and provide instructions on how to do it.

We do not see this happening currently for grocery bags.

2. What is the ability of the bags to regenerate in line with the principles of a circular economy?

The question here is whether they can be designed to have multiple useful reuses (such as using as a wrap, garbage liner or cover) or several useful economic lives following upcycling. With the weight of material content in a bag being very low, collecting it using a segregated approach is not a profitable exercise for collectors. On the other hand, collection of bags in a municipal bin rather than the recycling bin is encouraged due to the troubles it causes in recycling stream during processing. (Elejalde-Ruiz, 2015)

3. Is there a significant difference between recyclability and actual amounts being recycled?

The difference between these two is ascribed to poor disposal behavior, causing cross-contamination and the inefficiency of the collection and recovery systems resulting due to that.

Summing up all

If we bridge the gap between two schools of thought regarding Polyethylene grocery bags…

Yes, they create a negative environmental impact with litter compared to others, yet they are a better alternative even if they are used once compared to alternatives such as paper and cotton bags, with the impact decreasing even less when used multiple times.

Having LCA data provides an excellent foundation to start with comparing environmental performance. The ideal would be that all the above scenarios we considered outside LCA, can be used in environmental data modeling through LCA to provide a representative answer.

We often tend to do nothing when the domain knowledge, information, or the decision they lead to, in front of us are not clear. Breaking it into simple segments and progressive improvement in measurement is what we should aim to achieve in evaluating alternatives such as this.

What solutions can this information lead to?

It is important to remember that LCA data guides us to a decision as a key parameter, as the footprint of a material or a product cannot be altered significantly unless the production technology and raw materials are changed drastically.

Our decision may be shaped by seeking of additional information through questions.

As an example, some of the strategic alternatives to deal with the situation may come up through exploring answers to questions such as:

• Can we achieve alternative product designs with LDPE to have high reusability and promote reusability more?
• Can we have financial instruments that discourage litter (e.g. penalties), so that the intended recovery pathways are followed for LDPE bags?
• Should we discourage their use as the excess trouble for the recovery system is not worth it?
• Should we have better pricing for plastic to reflect the external cost and create affordability through product-service systems by providing access to products rather than ownership?