[en] The aim of this project was the valorisation of used edible oils by co-digestion together with agricultural or food waste, without any risk for human and animal health. It included the technical economical aspects. In the bibliographic part a state-of-the-art on fat digestion in Switzerland and Europe was done. The possible co-substrates were examined, under a biological aspect as well as economical and strategic aspects. Food waste from restaurants and canteens, that are used up to now for pig feeding, were retained. The co-digestion gives a new perspective for the valorisation of this kind of waste, whose traditional way of valorisation is compromised by the new EU directives. The experimental part aimed to define the possibilities and limits for the co-digestion of used edible oil with food waste as co-substrate. The study was done in a 690 litres bio-reactor. The results showed that co-digestion of edible oil with food waste is feasible with interesting performances, if oil doesn't account for more than 15% of the mixture (on dry matter). Biogas production amounted to 400-450 litres per kg input COD (chemical oxygen demand), with 60-65% CH₄. Based on the observed results a tender document was done, in order to consult manufacturers of co-digestion plants. An economical simulation was realised on the basis of the most complete offer. This simulation revealed that a benefit of CHF 3500 per year can be obtained for a plant processing 200 t/y edible oil and 9000 t/y food waste. Co-digestion allows for valorisation of edible oil, together with a co-substrate whose traditional utilisation will not be possible in the future. It leads to the production of renewable energy, with a positive economical balance. (author)