Photosynthesis engineering is a promising mean to produce both energy carriers and fine chemicals in order to remedy the growing scarcity of fossil fuels. This is a challenging task since it implies to design process for solar biomass production associated with short time constant (few days), while oil formation took hundred million of years. This aim could be achieved by cultivating photosynthetic microorganisms in photobioreactors with optimal surface and volume kinetic performances. Above all, such an optimization necessitate a careful radiative study of the process. A radiative analysis of photobioreactors is here proposed that starts with the determination of the absorption and scattering properties of photosynthetic microorganisms suspensions, from the knowledge their morphological, metabolic and structural features. A model is constructed, implemented and validated for microorganisms with simple shapes ; the extension of this approach for the treatment of complex shapes will eventually be straightforward. Then, multiple scattering radiative transfer analysis is introduced and illustrated through different approximations that are relevant for the conceptualization of photobioreactors, leading to the construction of physical pictures that are necessary for the optimization of the process. Finally, the Monte Carlo method is implemented in order to rigorously solve multiple scattering in complex geometries (geometries that correspond to an optimized design of the process) and in order to calculate the kinetic performances of the reactor. In this trend, we develop a novel methodological development that simplies the treatment of the non-linear coupling between radiative transfer and the local kinetic of photosynthesis. These simulation tools also benefit from the most recent developments in the field of the Monte Carlo method : integral formulation, zero-variance algorithms, sensitivity evaluation (a specific approach for the evaluation of sensitivities to geometrical parameters is here developed and shown to correspond to a simple implementation in the case of a set of academic configurations that are tested). Perspectives of this work will be to take advantage of the developed analysis tools in order to stimulate the reflexion regarding photobioreactor intensification, and to extend the proposed approach to the study of photoreactive systems engineering in general.
