For this study, we analyzed the supply chain of cucumbers imported from Spain and sold by retailers in Switzerland. The annual volume of cucumbers imported by a retailer in the Swiss market amounts to 3,408 metric tonnes (or tonnes) of cucumber (Personal communication, 2022). The analysis was conducted for two different scenarios: scenario 1 of a supply chain for cucumbers without plastic wrapping, and scenario 2 of a supply chain for cucumbers with a plastic wrap for each cucumber (Figure 1).

The system boundaries considered were each time from farm to point-of-sale (or grower to grocer), including the stages of agricultural production, packaging, distribution, retail, and end-of-life. The consumption stage was neglected due to the lack of data on food waste and consumer behavior in households. This assumption implies that the indirect effect of prolonged shelf life of the packaged cucumber after purchase is neglected, which would have, in turn, lowered the likelihood of food waste in households. The disposal of the packaging material, as well as the end-of-life of food waste during retail, were included in the analysis according to the current practice in Switzerland. For food waste disposal, we considered that 95% is composted (including the fraction actually used for feeding livestock), 3% is incinerated, and the remaining 2% is disposed of in landfill (Baier et al., 2016; Kawecki et al., 2018).

The functional unit chosen in our analysis was 1 metric tonne (i.e., 1 tonne) of cucumbers sold at retail. The functional unit was selected to compare the two systems (with and without plastic wrap) based on the function that is delivered (Cucurachi et al., 2019). For a cucumber supply chain, this function is to deliver a certain quantity of cucumbers to the consumer. Therefore, we defined our functional unit from a retail perspective. Based on this functional unit, we modeled the value chain of cucumber backwards, from retail to cultivation. It was assumed here that 5.5 g of low-density polyethylene (LDPE) is required for wrapping 1 kg of cucumber (Davis, 2011). Therefore, a standard-sized cucumber, typically weighing about 350 g, requires 1.93 g of plastic wrapping.

Primary data related to the production and distribution of cucumbers in the Swiss market were obtained directly from a Swiss retailer. The distance for land transport of cucumbers in refrigerated trailers from suppliers in Spain to distribution centers in Switzerland was approximately 1,200 km (Georg, 2019). The data of the food waste of Austrian retailers (based on a 6-month observation period in 250 stores) were used to estimate the difference in food waste at retail for cucumbers without plastic wrap (9.4%) and with plastic wrapping (4.6%) (Denkstatt, 2017). The estimated share of food waste at retail was used to back-calculate the starting volume of cucumbers cultivated (1103.75 and 1048.22 kg cucumber for scenarios 1 and 2, respectively), so that resultantly 1 tonne of cucumber is sold at retail for both the scenarios. Such an approach provides a better assessment of environmental impacts due to the embodied upstream resources and energy invested in food.

The end-of-life for plastic packaging waste was evaluated considering the amount of plastic used to wrap all the cucumbers, including those sold and wasted. Pre-harvest food losses during agricultural production were not considered, as we assumed that these losses do not differ between both scenarios. The losses occurring during transportation were omitted due to lack of specific information, acknowledging that this might underestimate the impacts of food waste along the supply chain. Secondary data for energy supply, packaging production, refrigerated transport, and waste treatment were calculated or obtained from literature for similar supply chains (Girgenti et al., 2014; Vinyes et al., 2017). The life cycle inventory of the supply chain of cucumbers according to the scenarios considered in this study is presented in Table 1.

We assessed the environmental impact of the cucumber supply chain by focusing on climate change. Here, we selected the global warming potential (GWP, kg CO₂-eq) as a measure of the environmental impact from greenhouse gas emission (IPCC, 2013). The GWP for the cultivation of cucumbers in a greenhouse was considered to be 2.13 kg CO₂-eq/kg cucumber, as obtained from collected meta-analysis data (Clune et al., 2017). This study primarily focuses on the GWP, although the trade-off between food waste and plastic packaging will also manifest itself in other impact categories. However, for impact categories such as land use, water use, and eutrophication, the impact of producing food (and consequently food waste) is very large relative to the impacts of plastic wrapping; therefore, these categories were not chosen for a comparative study (Nemecek et al., 2016). Note that in this study, we omitted the impact of eco-toxicity due to microplastics, as their fate and impacts are still not fully understood (Koelmans et al., 2019).

Dealing with the trade-off between food waste and plastic waste highlighted the importance of pinpointing exactly when it is ecologically better to use plastic wrapping. To this end, we calculated the environmental break-even point. This break-even point corresponds to how much reduction in food losses the plastic wrapping must induce, so that the use of plastic wrapping results in a net environmental benefit. These calculations were implemented using the Solver add-in of Microsoft Corporation (2016).

Table 2 presents the climate change-related impacts for the scenarios with and without plastic wrapping. Comparing the absolute numbers for the cucumber supply chain from Spain to Switzerland, the scenario with plastic wrapping leads to a 4% lower impact than the scenario without the wrapping. Considering the total volume of cucumbers sold at retail (3,408 tonnes of cucumber), we observe a net benefit of lowering greenhouse gas (GHG) emissions by about 426 tonne CO₂-eq. If we convert this to the social cost of carbon assigned for every tonne of CO₂-eq. emitted (i.e., CHF 150 per tonne CO₂-eq practiced by Swiss retailers; Gold Standard, 2016), the use of plastic wrapping in this supply chain can lower the net CO₂ emissions by about CHF 64 000 (or USD 71 000) annually in monetary terms. Switzerland generates about 4.35 tonnes of CO₂ emissions per capita per year (Global Carbon Atlas, 2018). This implies that the net reduction in GWP due to the use of plastic wrapping for cucumbers already equates to the annual carbon footprint of 98 Swiss persons.

Our analysis for scenario 2 (with plastic wrapping for cucumbers) revealed that a substantial contribution to the environmental impact comes from the energy-related environmental releases of the greenhouse cultivation of cucumbers (74%). Refrigerated transportation contributes to about 20% of the total impact. The impacts of the production and disposal of plastic packaging are comparably small. Plastic wrapping accounts for only 1% of the GHG emissions in the entire life cycle of an imported cucumber (Figure 2). The high climate change impact of cucumber cultivation results in a very high environmental benefit of reducing food waste. Then, every additional cucumber thrown away has a very high environmental cost due to the embodied energy and resources related to its production.

The relevance of plastic packaging within the entire supply chain depends much on the actual impacts of the cultivation phase. Other studies show a relative contribution that varies between 0.5 and 10% (Williams and Wikström, 2011; Wikström et al., 2014; Denkstatt, 2017; Hanssen et al., 2017; Molina-Besch et al., 2019; Wohner et al., 2019). A comprehensive case-by-case analysis is necessary for different fruits and vegetables, as the net environmental impact considering product and packaging systems is very sensitive to small details. Contributing factors include cultivation in open fields instead of greenhouses (Zarei et al., 2019), heat source of the greenhouse, the amount and type of packaging used, and the “food miles” associated with shorter supply chains for locally-sourced produce as opposed to longer supply chains for imported produce (Stoessel et al., 2012; Denkstatt, 2017).

A comparison of the two scenarios revealed that using plastic wrapping for cucumbers clearly reduces the overall climate change impact (Figure 3A). This is primarily because the benefit of a reduction in food waste is much more than the additional impact caused by the plastic wrapping. Indeed, when we explicitly compare the impacts caused by food waste and plastic wrapping, we observe that the use of plastic wrapping lowers the environmental impact due to food waste by 157 kg CO₂-eq per tonne cucumber, while itself having an impact of 32 kg CO₂-eq per tonne cucumber. Thus, the benefit of using plastic packaging in reducing food waste is almost 4.9 times higher than the negative environmental impact due to the packaging itself (Figure 3B). This impact will likely be larger, as we did not account for the reduced food waste at the consumer level due to wrapping. For easier comparison, the impact of one wasted cucumber (i.e., 0.992 kg CO₂-eq) was equated with the impact of the plastic amount required for wrapping a single cucumber (0.0106 kg CO₂-eq). It was found that every single cucumber thrown away equals the impacts of the plastic packaging needed to wrap 93 cucumbers.

The supply chain of cucumbers without plastic wrap has an estimated food waste of 9.4% at retail, which is more than twice higher than the estimated food waste occurring when plastic wrapping is used, namely 4.6% (Denkstatt, 2017). To assess when it would make sense to use plastic wrapping from the ecological perspective, we calculated the environmental break-even point for using plastic wrapping for cucumbers (Figure 4). We quantified the minimum reduction in food loss at retail (ΔW, %) that must be brought about by plastic wrapping, so that the positive impact of food waste reduction exceeds the negative impact due to plastic. The green area in Figure 4 indicates from which point onwards the use of plastic packaging is worthwhile and beneficial for the environment. In this region, the benefits of food waste reduction on climate change surpass the negative environmental impact due to plastic wrapping.

From our analysis, we found that the environmental break-even point is at a food loss of 8.3%, meaning a reduction of 1.1% for the food waste between the scenarios without and with packaging (indicated by the point of crossover in Figure 4). Hence, if the use of plastic wrapping brings down the food loss at retail from 9.4 to 8.3%, it already makes sense to use it from an environmental perspective. Plastic wrapping the cucumbers imported from Spain to Switzerland already lowers food waste at retail by an estimated 4.8% (i.e., from 9.4 to 4.6%) in the current case study (indicated by the dotted blue line in Figure 4), with a net lower environmental impact of 125 kg CO₂-eq per tonne of cucumber sold at retail. This reduction in food waste is clearly much more than the environmental break-even point of 1.1%. Therefore, from a climate change perspective, its use makes sense in the current supply chain. Moreover, plastic wrapping contributes further to indirect food waste reduction in households due to prolonged shelf life (Denkstatt, 2017). This presents a very challenging limit to compete with for any other strategies to preserve cucumbers without plastic wrapping, for example, by increased cooling within the supply chain.