EnvPack, an LCA-based tool for environmental assessment of packaging chains: Part 2: influence of assessment method on ranking of alternatives

EnvPack, a tool for assessing the environmental impact of packaging, offers the user four assessment methods. The question arose whether the choice of the method would affect the ranking of packaging alternatives and whether different hotspots in the life cycle would come up.

The EnvPack tool contains three different product types: non-carbonated beverage, shower gel, and ready-to-eat soup; product losses can be included. For each product, three to four representative packaging alternatives are included; the user can also define an own packaging. In total, 11 packaging alternatives are included that can be assessed with four methods having different perspectives. The agreements between methods was assessed with two correlation methods: Pearson’s and Spearman’s. The Spearman’s method is better suited for non-normal distributions as it first ranks the alternatives before computing the correlation coefficients. Pearson’s r and Spearman’s ρ were calculated for the total aggregated scores and for the six life-cycle stages distinguished in EnvPack. Furthermore, the correlation between three most contributing impact categories of the methods was assessed.

Pearson’s r showed very high (positive) correlations (r > 0.9) between the total aggregated score of the four methods using all packaging types, both for the losses included as excluded. All correlations were highly significant with p < 0.00. Spearman’s ρ showed a lower average value, 0.79 over all four methods and a higher variability. The circular economy method showed the strongest decrease in correlation when using Spearman’s. The difference of the correlation coefficients is caused by the non-normal distribution of the total scores of the packaging. On average, the top 3 categories of the two ReCiPe methods showed strong correlations with the top 3 categories of each other and of the CED method. The remaining methods had moderate correlations.

All four methods showed, per product group, the same packaging with the worst and the best total aggregated impact. For the intermediate performing alternatives, the ranking is dependent on the assessment method. Although the raw materials’ life-cycle stage is in most cases the most contributing stage, the choice of the assessment method can affect the hotspots within the packaging life cycle.