While the previous news have focused on the concept of circularity, circular strategies and indicators to measure it; this article focuses on what do we mean by material cycle. One of the key objectives of circularity is to “circulate products and materials (at their higher value)”. But to circulate materials or products, we first need to understand what a material cycle is.

Rankin (2014) defined the material cycle as the one that integrates three components that are interlinked. First, the resource stock, which are the resources present on Earth (i.e., trees, oil); second, the material stock, which is formed by the materials obtained from the resources (i.e., timber from trees, plastic from oil); and, third, the product stock that are goods or products that are made from the materials and used by society. Nevertheless, Rankin’s framework can be further improved (see Figure 1) by, first, distinguishing two types of materials (the virgin one, which comes directly from nature; and the recycled one, that results from the technosphere) and, second, adding the circular strategies (i.e., reusing, repairing, recycling). Having in mind this material cycle, depicted in Figure 1, the key challenge is to ensure the adequate management of these 3 stocks in order to close the material cycle, and, thus, reducing the demand of virgin material and waste generation.

Figure 1: Diagram of a material cycle, adapted from the one of Rankin (2014). The blue rows and words have been added from the original diagram.

Food distribution sector

When applying this theoretical framework to the food distribution sector, four main types of crates need to be analyzed: single use cardboard boxes, single use wood boxes, single use plastic crates and reusable plastic crates. For the cardboard and wood boxes, the key strategy is to optimize the management of the resource stock (trees), since they are made of renewable resource; and for cardboard boxes, moreover, the losses in quality and the degradation of the material needs to be considered as well, since fibers can be recycled only 3 times (Delgado-Aquilar et al., 2015). However, in the case of reusable plastic crates, the key strategy is to maximize the product stock, meaning to enhance the life cycles of the product by reusing, repairing and remanufacturing it, since the resource is nonrenewable (oil).

Moreover, plastic crates can also be recycled in a close or an open loop. While in current scientific articles have been usually considered as an open loop, with a certain loss of quality (as explained in another article), plastic crates can be recycled in a close loop with a 100% of material recovery, as claimed by IFCO in its Cradle to Cradle certification. This helps to maximize the recycled material stock and to decrease the use of virgin material and closing even more the cycle.

Nevertheless, besides the management of these 3 stocks, to achieve circularity we need to keep in mind two key principles: (i) to tighten the cycle (ii) for the longest period as possible (Sazdovski et al., 2021); meaning that all the strategies that enhance the “product stock” component should be prioritized. Hence, as already discussed in a previous article (where we referred to the report from Potting et al. (2018)), all those strategies such as reuse, repair, refurbish, remanufacture and repurpose are preferable than recycling and recovery. In this regard, Erwijk et al. (2020) stated that “recycling of waste cannot create a perfect circle because the growing demand for materials exceeds the waste available from past consumption, materials are lost or degraded during processing, and the energy required for processing escalates with higher collection rates.” Moreover, they conclude that the greater circularity by increasing recycling and recovery does not imply a direct reduction of greenhouse gas emissions due to the energy use for recycling.

In summary, businesses and, in general, supply chains should have a holistic perspective on the materials/products they use/sell when redesigning their system towards circularity; always keeping in mind that the strategies to maintain the product stock are crucial, and that the material cycle should be as tight  as well as long as possible.

By Laura Batlle Bayer, researcher of the ARECO postdoctoral fellowship at UNESCO Chair in Life Cycle and Climate Change.