The GreenFront project, funded by the German Ministry of Education and Research under grant 03XP0285B and running from 1 October 2020 to 31 March 2023, aimed to create a market‑ready sandwich element composed of wood foam and textile concrete. The goal was to develop a more efficient and production‑ready manufacturing process for both materials and to combine their production into a single large‑scale operation. The project was carried out by a consortium of partners: the Institute for Joining and Welding Technology at the Technical University of Braunschweig (TU Braunschweig), the Fraunhofer Institute for Wood Research (WKI), and the industrial partner Fricke and Mallah Microwave Technology GmbH (FM). FM supplied a microwave flow dryer and measurement equipment, WKI contributed expertise in wood‑foam production and conventional drying, and TU Braunschweig provided the scientific framework and coordination.

The work was divided into eight packages. Work package 1 focused on optimizing fiber production, while package 2 addressed continuous foaming and shaping. Package 3, the drying phase, was the core of the technical investigation. FM equipped its laboratory in Peine with a microwave flow dryer and conducted a series of drying trials on wood‑foam samples. The trials were complemented by experiments with other drying methods, including high‑frequency (HF) drying, to benchmark performance. The results showed that microwave drying at 915 MHz was superior: it required only a fraction of the time needed by conventional methods, eliminated skin formation and surface cracking, and prevented internal cracking that had been observed with HF drying. Moreover, the microwave process could reduce the moisture content to zero percent, achieving a fully dry product. The drying curve remained linear without a saturation plateau, indicating a steady moisture removal. Dielectric measurements performed at FM’s measurement station revealed that microwaves penetrate only a limited depth into wet wood foam, a factor that must be considered for industrial scaling.

Beyond drying, the project developed a combined production route for the wood‑foam and textile‑concrete layers, ensuring a stable sandwich element. Subsequent packages evaluated the mechanical properties of the finished element, investigated recycling options, and performed a life‑cycle assessment to quantify environmental benefits. The final reporting package produced two interim reports and a comprehensive final report, documenting all experimental data and analyses.

Collaboration among the partners was continuous throughout the project. FM maintained a consultative role, sharing its industrial microwave expertise and providing the necessary equipment. WKI supplied the wood‑foam formulations and conventional drying data, which were essential for benchmarking the microwave approach. TU Braunschweig coordinated the research activities, integrated the findings into a coherent production concept, and led the dissemination of results. The project’s outcomes are expected to enable a scalable, energy‑efficient manufacturing process for sustainable building materials, with potential applications in large‑scale construction and retrofit projects.