The "BIOTESS" project pursues the production of bio-based phase change materials (PCM) from liquid waste substrates of biowaste treatment, used cooking oil and fat residues from fat separators. Using waste substrates to produce bio-PCM has in general two advantages: On one hand, there is no competition with the cultivation of food, as it is currently the case with existing bio-PCM from vegetable oils such as coconut or palm oil. On the other hand, the waste substrates used will be upcycled into higher-value products. The use of leachate and process water from biological waste treatment plants can also reduce the treatment costs for biogenic waste. By separating various carboxylic acids from dilute aqueous solution, the organic load on these substrates can be reduced. The latter can significantly turn down the disposal costs, which in turn can affect the total waste disposal fees.

Fatty acids from leachates of waste treatment plants are currently hardly used, in rare cases for biogas production. Used cooking oils and fats from grease separators are currently mainly converted into biodiesel and then used as alternative energy source. Biodiesel is currently struggling with various conflicts that are currently preventing its further development. Through the conversion of biowaste substrates into PCM, high- performance storable products could be reached. As a result, larger amounts of carbon that would otherwise be released as CO2 emissions are stored in the developed PCM material. A corresponding reduction in greenhouse gases from waste treatment plants can therefore be expected.

In further course, the newly produced bio-PCM will be microencapsulated and used as a latent heat storage additive in a thermal energy storage foam (TESS) for the production of mineral, multifunctional insulation boards. This material composite serves as an innovative application technology for the insulation of new and existing buildings. The bio-PCM inside the microencapsulation undergo a soild-liquid phase change at specific temperatures and thereby absorb or release heat energy. The intelligent addition of microencapsulated bio-PCM within the foam can significantly improve the heat storage capacity of the TESS-Foam panels. Due to the phase change and the associated heat storage, the innovative TESS insulation material optimizes the indoor climate of the building while simultaneously reducing CO2 emissions compared to commercial insulation materials.

The currently available solutions for thermal insulation systems and building envelopes are usually based on the assembly of various individual products, which entails unavoidable technical and environmental disadvantages due to the lack of design in the whole wall-system. In this respect, the application of the newly developed TESS technology is simple and essentially consists of a layer of TESS insulation combined with a surface protection layer of a plaster system including a possible color coating. Improved design of envelope elements can also be sought by utilizing the performance of the new insulation material as an integrated system. As part of the project, concepts for a market launch are also being developed for the two product stages in parallel, taking economic and ecological aspects into account.