Microbes are the most abundant living forms on earth and constitute "the microbial engines that drives earth biogeochemical cycles". To face current environmental challenges, it is becoming essential to better manage the natural recycling abilities of microbial communities to foster the emergence of appropriate ecosystems services. In this respect, residual organic waste streams can be considered as potential feedstocks that could be used for in microbial processes for the production of useful compounds (methane, hydrogen, organic molecules,…) through anaerobic digestion or future environmental biorefineries. To better design and optimize such processes, engineers need appropriate models stating explicitly the causal relationships between process design parameters, associated selective pressures, resulting microbial community structures and sustained functions. Today however, the modelling of microbial dynamics only relies on many different phenomenological laws (Monod, Contois, Haldane,…). Being very useful in industrial biotechnological settings, where well defined cultures are operated in confined processes, their use for modelling mixed cultures in open systems is more challenging and usually requires intensive parameter fitting on a narrow experimental domain. The lack of knowledge about the basic principles underlying microbial growth is limiting our predictive capacity for biotechnological applications. There is today a need for stating a generic set of theoretical principles, which could be challenged by experiments, and that could give rise to models featuring an increased predictive power for better managing microbial communities. This is precisely the goal of the THERMOMIC project. For that, environmental engineers have provided us with interesting insights by studying microbial growth yields and energy balance in great details. A generic method for deriving energy balances per unit of biomass formed has been established and validated using culture data from many different organisms, which allows the general calculation of growth stoichiometry (Kleerebezem & Van Loosdrecht, 2010). However, until recently, the link between thermodynamic balances and microbial growth dynamics was not understood. We lately made a significant contribution in this direction. We proposed a thermodynamic theory of microbial growth by showing how systems constituted by microbes in contact with molecules could be likened to ensembles described by the laws of statistical physics. A growth equation was proposed, which links a flux (the growth of microbes) to a force (the energy density). Original prediction arose from the mathematical analyses of equations, that were found to be supported by experimental data, allowing the publication of this atypical theoretical work in a highly ranked journal (IF=9,302) (Desmond-Le Quemener & Bouchez, 2014). We today believe that this flux/force relationship between growth rate and energy could constitute the basis for a more generic framework for modelling microbial dynamics: this is the main working hypothesis of THERMOMIC project. We therefore propose to combine skills in general and microbial ecology, statistical physics, applied mathematics and environmental engineering to (i) solidify the theoretical ground of thermodynamic growth models (WP1), (ii) to mathematically explore their characteristic features compared to current phenomenological approaches (WP2) and (iii) to assess their suitability for environmental engineering applications (WP3). The general THERMOMIC objective is to give rise to a comprehensive body of knowledge, relying on solid theoretical grounds, mathematically stated, supported by simulations and experiments, in order to renew our understanding of microbial dynamics and to propose new models featuring increased predictive abilities that could foster the emergence of sound engineering applications.