In a review article published on March 24, 2022, in the journal Nature Sustainability, Nathalie Gontard from INRAE, the French Research Institute for Agriculture, Food and Environment, Montpellier, France, and co-authors outline the current practice in life-cycle assessments (LCAs) of disregarding the impacts from plastic particles and associated knowledge gaps and discuss the consequences of this on decision-making.
LCAs are a widely used method to analyze the environmental impacts of plastics by considering all life cycle stages from cradle to grave, comparing them with alternative materials, and deriving policy decisions from the comparisons. Despite the ubiquitous environmental presence and potential impact of particulate plastics, Gontard and co-authors assert LCAs currently do not account for short- or long-term effects of particulate plastics pollution. One reason for this is that current fragmented scientific knowledge prevents a proper risk assessment. In general, the long-term fates of plastics (exported, landfilled, or leaked) would usually not be included in LCAs. The scientists find that this neglect influences the outcome of LCAs comparing plastic with alternatives materials and could distort efforts to fight plastic pollution.
To illustrate their concerns, Gontard et al. compared the environmental impacts of polyethylene terephthalate (PET) and polyhydroxyalkanoates (PHAs), two polyesters which share functional properties but strongly differ in long-term fates. While PET is very persistent and pervasive, PHA has been shown to fully biodegrade even under natural conditions. They performed an LCA according to current practice and also included the uncertainties from damage beyond common end-of-life options (landfilling, recycling, incineration, composting). Driven by the large end-of-life uncertainties of PHA converting into methane and of PET’s “monetized damage” (market reaction to environmental damages), PET was found to be preferable when considering “global warming potential” while PHA performed better with regard to “monetized damage,” respectively. This demonstrated that current data gaps and their neglection can determine the outcome of LCA’s and with it also political actions. “Underestimating the benefit of biodegradability of materials, whether they are plastic-like (for example, PHA) or fiber-based (for example, paper), is only one example among many potential consequences of omitting persistent plastic particulate impacts in LCA.” Another example Gontard and co-authors outline in this regard is plastic recycling in Europe.
A recent paper, published on March 30, 2022, in the journal Sustainability, focused on the recyclability topic specifically by investigating how design of single-use plastic packaging can positively and negatively affect the products recyclability and the outcomes of an LCA (carbon footprint). Investigating 14 different packaging designs, Jonas Keller and co-authors from the University of Stuttgart found that large labels, fillers, dark colors, and insoluble adhesives reduce recyclability. The researchers also compared existing methods for recyclability assessment. In all their assessed scenarios, a lower recyclability of a plastic container resulted in a larger carbon footprint.
In their review, Gontard et al. also describe the particularities of fossil-based plastics that affect its end-of-life impacts compared to other materials. For instance, as opposed to dense materials (e.g., glass) and natural organic materials (e.g., paper) which slowly solubilize or get digested by microorganisms, respectively, plastics “do not reintegrate into one of the relatively well-known biogeochemical cycles of the elements of our ecosystems.” Furthermore, as opposed to most pollutants, plastic impacts are not mediated by a single chemical but by numerous chemicals (e.g. additives, monomers) that might be released into the environment, as well as by other complex phenomena such as fragmentation and interaction. Consequently, “the conceptualization of the plastic biogeochemical cycle as a novel and holistic paradigm,” according to Gontard et al. “has been an important recent milestone in clarifying the discussion about plastic pollution.”
Gontard and co-authors concluded that “unknowns are essential pieces of the puzzle to solve, especially for plastic pollution, which results from a complex, long-term and poorly understood series of intertwined phenomena.” Until knowledge gaps are closed, they recommend that LCA’s comparing plastic’s long-term impacts are only done when the plastic is completely destroyed in some way through either burning or chemical recycling or when “an indicator of potential plastic particulate footprint” is added.
A previous study has further proposed to extend LCAs to include impacts related to consumer exposure to chemicals in food packaging (FPF reported). Moreover, a review on 71 published LCA studies on food packaging and food serviceware analyzed the correlation of material attributes (e.g., recyclability, compostability) with environmental impacts (FPF reported).
References
Gontard, N. et al (2022). “Recognizing the long-term impacts of plastic particles for preventing distortion indecision-making.” Nature Sustainability. DOI: 10.1038/s41893-022-00863-2
Keller, J. et al (2022). “The Relevance of Recyclability for the Life Cycle Assessment of Packaging Based on Design for Life Cycle.” Sustainability. DOI: 10.3390/su14074076
