Aluminium Coffee Capsule Recycling: Improving Metal Recovery

The recycling of aluminium offers significant ecological and economical importance, as secondary aluminium production saves approximately 90 % of the energy required for primary production. With the anticipated rise in energy costs due to decarbonisation efforts and stricter regulations, such as mandatory recycling quotes, the relevance of aluminium recycling is expected to increase further. Currently, clean, coarse, and uncoated aluminium scrap is in high demand as a secondary raw material and achieves prices on the scrap market that correspond to these of primary Al. Consequently, lower-grade scrap materials are gaining more attention.

Among these, aluminium-containing packaging presents unique challenges in melting processes compared to end-of-life materials from sources such as automotive or construction sectors. These packaging materials are typically small in size, with an unfavourable surface-to-volume ratio, and contains other components such as plastics or pigments in addition to aluminium. In the case of coffee capsules, the high organic content, primarily coffee residues, poses additional complications. Even when such materials are collected separately, improper process management during recycling can lead to substantial metal losses and increased salt consumption.

This work investigates how various preprocessing steps like shredding or pyrolysis influence the metal recovery yield of coffee capsules during melting under flux salt conditions in the refiner process. Furthermore, the study evaluates the energy release and calorific value of the non-metallic compounds adhered to these residual materials, as organic residues can serve as alternative fuel source in rotary tilting furnaces under optimised operating conditions, thereby reducing the requirements for gaseous energy carriers.