The conscious consumer
As consumers, we face a lot of choices in the supermarket. We have to make trade-offs between costs, our ecological footprint, diversity, and palatability. At the same time, each product comes with multiple properties such as origin, packaging, fair trade labels, or farming methods. But at least, choosing regional produce should always come ahead in terms of sustainability, right?
Using an example of apples, from the perspective of a European consumer, we want to see how this is not always obvious. We will see that the best choice depends on seasonality, and no single source is a clear winner. We also demonstrate how these decisions can be made in the context of supply chain network design.
Trade-off: transportation vs. storage
Apples are produced in most European countries, and local production satisfies a significant amount of local demand. However, a lot of apples are imported from distant sources such as Chile and even New Zealand. This may be surprising if we believe that transportation dominates cost or ecological footprint. A recent study (see: How green are my apples?) has investigated the impact of the various stages of the supply chain for a set of sources.
The key point for our question is the fact that harvest in Europe is concentrated on a short period during late summer. If we want to consume apples throughout the year, we have two basic options. Either we store it for long periods, which requires energy-intensive cooling. Or import it from other locations in the southern hemisphere where the harvest season is offset or is longer because of the wide extent in latitude.
The study provides some average numbers for greenhouse gas emissions, measured in kg CO2eq per kg of product. Let us focus on just two aspects: When importing from Chile, the dominant factor is transportation via ships. For local production in the UK, processing and storage dominates, with storage lasting up to 10 months after harvest. The more time passes after harvesting, the higher the emissions (and costs) of the local apples. The chart below shows that if we want to consume apples six months after the harvest or later in the UK, we’re better off importing them from Chile.
Modelling supply chain costs
Going beyond that simple example, imagine we want to plan a global supply chain for apples, with multiple options for sources globally, and monthly demand profiles for different regions we want to serve.
To each source, we can assign financial per unit costs and capacities, to account for seasonal harvest. Next to each source, we can provide storage options, with financial costs as well as emission factors. Storage can equally be provided next to the demand regions, where we assign prices for potential revenue. Finally, modes of transportation connect the source regions with the demand regions, covering costs, emissions and also lead time. Our two-country example is represented in a schematic drawing below.
When aggregating all flows and stocks in this network, we can calculate the total emissions as well as total profit. The trade-off between these two quantities can be explored as discussed in our post: How to include sustainability in your decision-making process?
Going further
This article has simplified a complex problem to demonstrate how supply chain modelling can help find an answer to questions involving many decisions and potentially conflicting goals.
The study also includes water consumption next to greenhouse gas emissions. The authors further mention that the footprint could also be lowered by improving the energy mix of the involved regions, not just a different choice of sources.
Further, in the context of food items, transportation typically does not play the biggest role in emissions, and what we eat matters more than where it is sourced, as demonstrated by the chart Food: greenhouse gas emissions across the supply chain from Our World In Data.
Finally, the conscious consumer in the supermarket that considers regional products should not forget about the season.