It is called silverskin, and it is the film that peels away from the coffee bean during roasting. What has been a waste material for centuries is becoming a precious resource for the future, thanks to innovative processes that could transform it into a biomaterial for making car interiors. In a medium-sized roastery, several sacks of this silvery film accumulate every day; it is usually burned or composted. Only a small proportion of it is turned into fertiliser: the large amount of caffeine it contains makes it unsuitable for animal feed and for producing biogas.

A historic German roastery supplies the research

Volkswagen Group Innovation, the German automotive group's incubator for innovative vehicle and mobility solutions, could soon change the course of events: research has shown that silverskin has the right characteristics to be used as a filler material for synthetic leather. "It is a dry substance and is already in an ideal form for processing (it does not need to be dried, so it requires no energy)," explains Martina Gottschling of Volkswagen Group Innovation, who, for this research, sources the material from the historic German coffee roastery Heimbs of Braunschweig, founded in 1880 and in operation since 1954.

The advantage, in short, is threefold: organic materials that are currently being disposed of are reused, the use of animal-derived leather is reduced, and achieving all of this requires no great amount of energy. In other words, it is another small but important step towards the sustainability of the automotive industry.

Coffee in place of synthetic leather

Of course, while sustainability is one of the "guiding lights" of the Volkswagen Group's actions, it is equally true that it is not the only one: before a new material or process can be approved, it must pass stringent quality standards, both in the short term and in the long term. Interior trims must in fact retain their visual and tactile qualities throughout the entire life of a vehicle. "In tests carried out so far, the durability appears to be comparable to that of tried-and-tested forms of synthetic leather," explains Gottschling, adding that the samples tested contain more than 50 per cent organic materials: synthetic leather is in fact made up of a multi-layer structure, consisting of a fabric backing (made from renewable raw materials), filler materials (the silverskin, as mentioned) and, finally, the outer surface.

Potential applications of silverskin

As we have seen, tests so far have shown that the silvery film covering the coffee bean could function only as a "filler" — that is, as a partial component of a trim material. A contribution to the overall sustainability of a car that might seem marginal. In reality, its potential is greater. One need only think of the number of parts — and how extensive they are — that are currently often covered in leather inside a cabin: we are talking about seat upholstery, the steering wheel rim, armrests, door panels and the gear lever. Silverskin could complement the broader commitment the Volkswagen Group made some time ago to minimise the use of materials of animal origin, particularly on the models in the ID. electric range. On the ID.3 and ID.4, and on all models that will come to market, conventional animal-derived leather has been replaced with synthetic leather. A choice that retains ideal tactile and visual properties, offers wear resistance and ease of cleaning, and is increasingly appreciated in many markets, from China to the United States.

Plastic and cars: a bond that is hard to break

The recent study on coffee silverskin — and on organic materials in general — is valuable for improving the carbon footprint of car interiors, by using what were, until now, waste materials within a circular economy framework. The goal is to reduce the use of plastic in cars as much as possible. This will, however, take time: before it can be used on production models, the synthetic leather made with silverskin will need to be made available for large-scale production in several surface grain variants, which are necessary to deliver different tactile sensations.

Coffee could come on board within a few years

"The potential is enormous and could help us further lower the ecological footprint of the ID range," concludes Gottschling. Another advantage of silverskin is that the supply of raw material is not a problem: the volume of silvery film required is not large; moreover, there are very large stocks accumulated by the roastery during the pandemic. For this reason, its use on the Group's next prototypes could become a reality within a couple of years.