Technological watch

Life-Cycle Assessments of Plastic Products Have Blind Spots

A week-long conversation thread on SPE’s The Chain brought up some interesting comments regarding life-cycle assessments (LCAs). It began with a question from Conor Carlin of Illig LP, who wanted to discuss the following statement: “The value of using a material with a lower environmental impact has yet to be quantified as a reliable numerical value that can be incorporated into material selection, and probably such a metric cannot be created.”

Companies often send me life-cycle assessments of their materials, as these assessments are provided to their customers to encourage them to buy a certain material based on the environmental impact and its end-of-life or recycling value. Carlin asked, “Are LCAs the only tools available? Are there other, current visual tools/systems that allow designers to fully understand trade-offs between performance and environmental sustainability?”

BASF recently published an LCA for its ChemCycling technology, noting in its summary, “At the end of the life of a plastic product, it is necessary to select the method of recovery with the best performance by means of a scientific life cycle assessment. For plastics where there are large volumes of single-stream waste arising without significant impurities, such as PET from water bottles, mechanical recycling has a smaller carbon footprint than chemical recycling.

“However, especially with mixed and contaminated plastics it may be impossible or very inefficient to recycle them mechanically. This means that they are most likely incinerated, and the resulting energy is used to generate steam or electricity.” (In some European countries, they make larger use of incinerating waste than we do in the United States.)

BASF’s LCA concluded that, in cases where plastic waste may be incinerated, chemical recycling is the better option, as it “complements mechanical recycling and can be a more sustainable solution than incineration or landfill of plastic waste. It, thus, contributes to a circular economy.” This has been an ongoing discussion in Europe — is chemical recycling conducive to a true circular economy?

An LCA study conducted by Sphera for BASF, which was reviewed by three independent experts, comes to the clear conclusion that chemical recycling (pyrolysis) of mixed plastic waste emits 50% less CO2 than incineration of mixed plastic waste, said BASF’s statement.

Chemical recycling results in lower CO2 emissions

Companies perform LCAs in order to determine the environmental impact of materials produced using fossil fuels (oil or gas for energy), as well as other resources such as water. BASF’s study compared the “CO2 emissions of plastics produced with pyrolysis oil under a mass balance approach with conventional plastics made from fossil naphtha. It arrived at the conclusion that chemically recycled plastics cause significantly lower CO2 emissions than those produced from primary fossil resources. The lower emissions result from avoiding the incineration of mixed plastic waste.”

BASF’s LCA study also found that “manufacturing of plastics via either chemical recycling (pyrolysis) or mechanical recycling of mixed plastic waste results in similar CO2 emissions. It was taken into account that the quality of chemically recycled products is similar to that of virgin material and that usually less input material needs to be sorted out than in mechanical recycling.”

The environmental impact of a material, in my opinion, is not an inherent property in the same way that notched izod strength or chemical resistance would be for plastics. Additionally, the environmental impact of any material must take into consideration the actions of consumers: Will they put the used product into the proper container, or will they throw it into the environment?

Too often a life cycle analysis only looks at end-of-life options such as recycling and what type of recycling is best (mechanical or chemical), when an evaluation of material selection is also needed, i.e., biodegradable or compostable. We’ve seen many examples of companies attempting to be “green” by replacing plastic in their packaging with materials that turn out to be less eco-friendly when the entire manufacturing process is taken into account. A life cycle analysis has to include more than just end-of-life considerations.

I found a Sustainable Materials Management (SMM) statement dated April 19, 2018, from the Plastics Industry Association (PLASTICS) in my files addressing the issue of LCAs. Here’s what it said:

“Taking a systemic approach to using and reusing materials more productively over their entire lifecycles affords the opportunity to improve environmental outcomes, conserve resources, and reduce costs. Accordingly, PLASTICS embraces Sustainable Materials Management (SMM) as a framework to evaluate resource usage during the design, manufacture, use, and recovery of plastic products and packaging. PLASTICS recognizes the value of Circular Economy principles when circularity of materials yields the greatest environmental benefit over a product’s lifecycle. In making this assessment, however, PLASTICS advocates for the use of SMM as a guiding policy principle, one which considers the entire ecosystem of the product, and prioritizes the use of materials and processes that consider total energy and resource inputs throughout the entire lifecycle of a product, and minimizes associated waste. SMM’s holistic approach achieves this goal by measuring metrics like greenhouse gas emissions, water usage, and transportation efficiencies for different materials, and comparing their advantages while meeting economic, social, and environmental requirements.”

Kim Holmes, Vice President of Sustainability for PLASTICS at the time this statement was released, commented: “Every material carries some environmental impact. But through a life-cycle analysis approach, we find that, in so many instances, plastics are the most efficient and sustainable choice, particularly when the plastics are recovered and their value can continue to be realized. The SMM approach represents the smartest way forward for the industry, the environment, and the economy, and we look forward to using it as a blueprint for how we can continue to make a positive impact.”

In response to Carlin’s discussion statement, it may be that actually “quantifying a reliable numerical value” for the sustainability of a particular material will remain an inexact science given the many variables that we deal with in plastics. To the traditional plastic material variables, add bio-based, bio-degradable, and compostable materials to the mix to accommodate a range of end-of-life options and the task is made that much more difficult. As I’ve often said over the years, it isn’t easy being green.

Image: Christian Horz/Adobe Stock

Publication date: 04/07/2020

Plastics Today

This project has been co-funded with the support of the LIFE financial instrument of the European Union [LIFE17 ENV/ES/000438] Life programme

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Last update: 2020-07-14