It’s amazing what can be produced with leftover pineapple: supported by the DAAD, RWTH Aachen University, the University of Dar es Salaam and the University of Mauritius are exploring an innovative production material.

When Ben Vollbrecht buys a pineapple at the supermarket, he does not look at it in quite the same way as most customers do. “For me, the fruit that ends up in our supermarkets is what is left over from a plant that is a valuable source of raw materials,” the 30-year-old explains. Vollbrecht is a doctoral student and research associate at RWTH Aachen University’s Institute of Textile Technology. Together with partners from the University of Dar es Salaam in Tanzania and the University of Mauritius, the Aachen Institute has been developing new fibre composites made from plant leaves, specifically pineapple leaves, since 2020. They want to use the new material to build parts for an electric scooter, their joint goal being to have a demonstration model ready by 2024.

Entitled WasteDrive, the cooperative project being pursued by the three universities is part of the DAAD programme Partnerships for sustainable solutions with Sub-Saharan Africa – measures for research and integrated postgraduate education and further training. Together with the BMBF’s International Bureau, which is part of the DLR (German Aerospace Center) Project Management Agency, the DAAD is supporting partnerships between African institutions and German universities, non-university research institutions and companies. This involves researchers and practitioners from both continents working together to tackle global challenges, with research and training going hand in hand.

Avoiding carbon emissions

WasteDrive is all about a sustainable circular economy in which waste materials are turned into new resources. “The leaves of pineapple plants contain fibres with much greater tensile strength than those of other plants, yet they have not been used to date,” explains Ben Vollbrecht. Normally, pineapple farmers burn the remaining leaves once the fruits – which grow above ground in a bed of leaves – have been harvested. Although the ash from the leaves, which are 30 to 50 centimetres long, does have a certain fertilising effect, burning the fields is nonetheless problematic from an environmental viewpoint as it generates harmful carbon emissions.

So far, pineapple leaves have been regarded as a worthless agricultural waste product – and yet they can be extremely useful as “waste biomass”, as Professor Hareenanden Ramasawmy from the University of Mauritius calls them. “The WasteDrive project is an example of the synergy between basic research and technical applications that benefit society in general,” the scientist explains. Even before the DAAD-funded cooperative project began, he had already been working to develop new materials from plant leaves. His research had focused on banana leaves. “His team’s experience is very valuable for our project,” says Ben Vollbrecht.

The University of Dar es Salaam contributes its expertise in cultivating and processing the pineapple plant and in the machine-based extraction of fibres to the cooperative project. The long-term objective is to set up a research centre for fibre-based biocomposite materials on the African continent at the university. Besides the fibres from pineapple and banana leaves, those from oil palm leaves and coconuts can also be used to create high-quality composites. Their advantage over other natural fibres such as jute or sisal is obvious: raw materials obtained from agricultural waste products do not block any additional agricultural land and cost very little.

Additional income sources for pineapple farmers

Pineapples and bananas are important crops and exports in Tanzania. The joint research and training being conducted with partners from Germany and Mauritius also entails economic opportunities for the country. “The project offers pineapple farmers additional income sources, either by selling the pineapple leaves or by setting up a sideline business to extract the fibres. This improves their livelihoods and brings the concept of a circular economy to life,” says Hareenanden Ramasawmy.

To get to the fibres inside the leaves, the outer layer of the leaves is removed in a first step. The exposed fibres are then dried and combed using a simple machine. “The technique is similar to a manual lawn mower that separates the biomass of the leaves from the fibres,” explains Ben Vollbrecht. For the purposes of the project, these steps are conveniently performed in Tanzania. In Mauritius, a method of removing any impurities from the fibres is being developed. Rather than using chemicals, the researchers are experimenting with a mixture of lime and wood ash, both of which are waste products from other economic cycles. A machine is then used to combine the pineapple fibres to create a kind of non-woven mat that is infused with a biocompatible resin. This makes it so strong that it can be turned into products.

“This climate-friendly and high-performance natural fibre can be used in all kinds of applications – for example for car interiors in the automotive industry, for sustainable furniture or other lightweight components. In our demonstration product, the electric scooter, we plan to use it to make the footboard and the handlebar,” says Ben Vollbrecht. The industrial engineer oversees the project management for the research partnership. Within the project network, the RWTH is also responsible for developing the scooter and for the final stages of processing the material.

Everyone involved sees considerable future potential – also for teaching in the area of sustainable economic management. The project’s training module is preparing teaching materials and drawing up a curriculum for a series of seminars that will explore the entire process chain, from production and processing of the fibre material to the manufacture of natural fibre-reinforced synthetic materials. In addition, a digital learning platform is being set up. Its concept and content will be trialled in annual summer schools and evaluated during joint workshops with the research partners. Ben Vollbrecht firmly believes: “Our partners from the Global South will be able to avoid making the same mistakes that the North made over the past 100 years. They can become the pioneers in establishing forward-looking circular economies.”

Ulrike Scheffer (26 October 2023)