Symbiose

14-10-09  par Symbiose

Dans le cadre de l'évènement "Life cycle conference" à Boston du 29 septembre au 2 octobre 2009, furent présenté les premiers résultats d'un travail portant sur une approche dynamique de l'ACV et appliquée à la méthanisation des microalgues. Ce travail s'inscrit dans la thèse de Pierre Collet (INRA-LBE, SupAgro) et qui participe de l'approche ACV dans le cadre du projet Symbiose (contact collet(at)supagro.inra.fr)

Dynamic Life Cycle Assessment of biogas production from micro-algae
Collet Pierre, Montpellier SupAgro
Arnaud Hélias, Montpellier SupAgro
Laurent Lardon, INRA
Jean-Philippe Steyer, Montpellier SupAgro
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Fossil fuel depletion and climate change have lead many research groups and private companies to focus on use of biomass to produce renewable energy and fuel. Because of their high production yield, micro-algae have been pointed as an interesting alternative. A relevant mean to upgrade the energy value of micro-algae with optimal performances is the anaerobic digestion of the algae. It enables achievement of environmental benefits and production of energy from renewable resources. However such processes only exist at lab-scale. In order to assess and optimize its performances and environmental impacts, one has to stimulate its behaviour through dynamical models. In broad outline the two major compartments of the system (micro-algae culture and anaerobic digestion process) are linked by internal flows (micro-algae, digestates…) and receive external flows (light, cosubstrates…). As a consequence, overall behaviour is determined by the interaction of several time-dependent processes. For example, the temporal availability of winery effluents induces a better anaerobic digestion due to the high C/N ratio of this kind of cosubstrate, and consequently a bigger production of biogas. So, due to the close loop operating, the needs of chemical fertilizers are lower, and the emissions caused by their production too. This shows the necessity to realize a dynamic Life Cycle Assessment. In our context, a pertinent Life Cycle Inventory can not be achieved without taking into account the dynamic of several processes; some economic flows are determined according to the temporal evolution of processes. Consequently, we integrate dynamic system modeling of micro-algae growth and anaerobic digestion of biomass in the LCA in order to obtain dynamic flows. This approach allows us to obtain dynamic data for the Life Cycle Inventory. This is a preliminary step to more accurate impact assessment.