Modeling and integration of a closed loop system for production of SNG from microalgae

Abstract

In recent years 3rd generation of biofuels are recognized as one of the most promising pathways for the reduction of greenhouse gases and the production of renewable energy. SunChem is integrated biological and thermal process in which main aim is to obtain methane, and also electricity and heat. Biological part is performed in photobioreactors (open or closed) and thermochemical process is in fixed bed catalytic gasification (HTG). SunChem system is developed in terms of thermochemical performance (laboratory scale HTG plant in Paul Scherrer Institute premises) on wet feedstock (15-30% dw. biomass), but there is not mastered biological part. Lab scale experiments of closed PBRs are just starting on EPFL. I concentrated on closed loop system, which means that nutrients, water and carbon dioxide is looped in SunChem system with potentially low environmental impact (relation to open ponds). In my master thesis was performed analysis of microalgae strain characteristics. Next was developed biological part of microalgae engineering, where was analyzed two types of closed PBR cultivation. Microalgae cultivation was performed in terms of scenarios, which aims were set up as carbon dioxide utilization and bulk biomass production for feedstock purposes. Obtained results of high productivity scenario, was integrated in thermochemical process of HTG and modeled by Martin Gassner. There was also performed economical estimation of investment motivation in terms of biological part and thermochemical part of SunChem system.The main challenge in SunChem system is to increase its efficiency and decrease the cost of production and conversion into useful energy carrier.