Biorefineries are set to become an important agent in the shift towards a circular economy due
to their potential to valorise organic wastes into marketable products. Anaerobic fermentations
yielding volatile fatty acids are a key process in this production scheme as their products act as
intermediates between the organic wastes and the final biorefinery products. However, their
product selectivity is highly influenced by the environmental conditions and the mechanisms
governing the process remain unknown. In this thesis, predictive tools were developed with
the objective of understanding the mechanisms governing anaerobic fermentations and of
designing processes targeting specific volatile fatty acids with high productivity
