The InKa project set out to transform commercially generated coffee grounds into high‑value intermediates that could improve the performance of end products or address critical raw‑material shortages. The core of the effort was a primary‑raffination scheme that separated valuable fractions from the spent grounds. Two main intermediates were produced: oil‑free coffee grounds suitable for paper and cardboard manufacture, and C18:2 alkyl‑ester epoxides derived from the extracted coffee oil.

The technical work began with defining the target product specifications (AP 1). Optimised extraction of coffee oil from the grounds (AP 2) and subsequent transesterification (AP 3) yielded fatty‑acid methyl esters (FAME). These FAME were epoxidised (AP 4) to produce alkyl‑ester epoxides with high epoxy content. From the epoxidised esters branched polyols were synthesised (AP 5). The polyols were characterised thermally and chemically: differential scanning calorimetry showed that products remained stable up to about 240 °C, indicating suitability for use in biobased polyesters such as polylactic acid (PLA). The glass‑transition temperature and melting behaviour improved with increasing epoxy content, while the enthalpy of melting decreased, suggesting the formation of longer, branched chains. Viscosity measurements revealed a rise with higher epoxy content, and gel‑permeation chromatography confirmed that the molecular weight of the polymers increased proportionally to the epoxy level of the starting material.

Scale‑up experiments (AP 5.2) reproduced the laboratory synthesis on a 300 g scale, with thermal properties matching the small‑scale results. The polymers were then processed into additives for PLA (AP 6). The additives were compatible with PLA chains, forming core‑shell structures when blended at a 50:50 mass ratio of polyol to L‑lactide. Injection‑moulded PLA specimens containing the coffee‑oil‑based additive exhibited a three‑fold increase in elongation at break compared with neat PLA, and a noticeable improvement in impact resistance. These performance gains demonstrate that the additive not only serves as a value‑added product but also addresses a material‑performance gap in bioplastic applications.

The spent coffee grounds, after oil removal, were evaluated for suitability in paper and cardboard production (AP 7). Their fibre content and mechanical properties were found to be compatible with conventional paper‑making processes, offering a route to reduce dependence on scarce recycled paper stock.

The project’s economic assessment (AP 8) used material‑flow analyses to estimate the cost of the intermediates and their downstream products. The findings support the viability of an integrated biorefinery that couples coffee production with waste‑to‑resource conversion, enhancing the value chain for both biopolymers and paper.

In terms of collaboration, the InKa consortium combined expertise from industry and research. The project was funded by the German Federal Ministry of Education and Research (BMBF) under the Technology Initiative Biorefineries, part of the National Research Strategy Bioeconomy 2030. BellePapier GmbH, a small‑to‑medium enterprise, led the material development and conducted application tests in paper manufacturing. The research side provided the chemical synthesis, characterisation, and performance testing, while project management coordinated the activities across the consortium. Over the project period, the partners worked together to move the process from laboratory proof‑of‑concept to pilot‑scale demonstration, laying the groundwork for future industrial deployment.