Over the weekend I can across a article about carbon-neutral coffee. The article reported that the Cornish coffee roaster Yallah Coffee are transporting their coffee beans by sailing ship directly from Colombia. This unconventional practice started me thinking about carbon-neutral supply chains and the impact this has on resulting optimisation problems.

In short, a complete supply chain is the transportation of goods, starting from the raw inputs, through all intermediate producers until the finish product reaches the consumer. It is not always necessary to consider the complete supply chain, since an individual producer may only consider a couple of preceding production steps. For example, a beer brewery is concerned about the supply of aluminium cans, but not necessarily the supply of bauxite to the aluminium smelter. Products with a large number of components have more complex supply chains. In such cases, it is difficult for an individual producer to have an oversight of the complete supply chain.

In the context of coffee, there are very few inputs to the final product. As such, it is possible for a coffee roaster to have control over the supply chain. The primary input for coffee is the raw beans. There are other inputs related to the roasting and the packaging, but for this blog we will only consider the supply chains of the beans from farm to cafe.

The supply chain

The coffee supply chain can involve many different players. A nice, concise description of the coffee supply chain is given here. A large proportion of the coffee growers are based in South America. So the chain of the coffee bean is from the farm to the exporter by road. The raw beans are loaded onto a ship for transportation to the UK. These raw beans are unloaded and transported to the coffee roaster by road. Then the packaged beans make their way to the cafe.

The largest contributor of carbon emissions in the coffee supply chain is shipping. It is reported that the trip from Colombia to the UK by ship would emit 2 tonnes of carbon. Thus is makes sense to eliminate this part to reduce the carbon footprint in producing coffee. This is achieved by using sailing vessels, such as those operated by the Blue Schooner Company.

Changes to the supply chain

From the optimisation point of view, there is little change to the modelling when taking carbon out of the supply chain. The major difference is the inputs to the optimisation model. The different inputs are:

  • different shipping options
  • shipping times
  • costs of shipping

Importantly, we must consider the different shipping options. The traditional supply chain would use cargo ships, which are quite robust to weather conditions. By contrast, sailing ships depend on favourable winds, and can be limited by the weather. Also, at present there are not too many sailing ship operators providing cargo routes. When formulating the supply chain optimisation problem, we must properly model the limited nature of using sailing ships.

An important change to the optimisation problem is the consideration of carbon emissions into the objective function. This can be achieved as a single objective, or as multiple objectives. Traditionally, operating cost has been the primary concern when optimising supply chains. The shift to reduce carbon emissions has driven a change in the formulation of optimisation problems.

Greener supply chains

The report on carbon-neutral coffee really shows the growing appetite for considering carbon emissions in optimisation problems. While this has been a research topic for quite some years now, it is great to see how this is being implemented in practice.