INTEGRATED ALGAE BIO REFINERY: NUTRIENT AND CARBON RECYCLING FROM WASTE

Driven by the sustained growth of resource consumption and waste generation, the circular economy has received much attention as a solution to surmount the consumption and production demand of goods. Microalgae are a key component of circular economy where they can be used as a source of biomass, products and energy. Under this circumstances, this Ph.D thesis aimed to provide the effectiveness of algae-waste based system. Particularly, this work mainly focused on integrating microalgae with various organic waste streams treatment by achieving nutrient recovery of the wastes as well as producing algal biomasses. Instead of applying the microalgae pure species, the innovation of this work (Chapter Ⅱ) explored and demonstrated the potential for isolating and cultivating microalgae-microbial consortia (AC) from different organic wastes as original growing substrates, providing the knowledge of the structure, diversity and population of Eukaryotic and Prokaryotic compositions of these microbial-microalgae consortia communities. The survived and well adapted ACs were analyzed by next generation sequencing technology. Then in Chapter Ⅲ, these ACs have been applied on nutrient rich waste stream (nanofiltrated pig slurry) in autotrophic condition to be evaluated their growth ability for producing biomass and nutrients recovery ability for treating wastes. Furthermore, biochemical compositions have been tested along with the fatty acids and amino acids profiles for further application potential. Microalgae can not only grow under autotrophic condition, but they can also grow under mixotrophic nutrition by combining both the autotrophic and heterotrophic mechanisms by assimilating available organic compounds as well as atmospheric CO2 as carbon source. A difference approach in Chapter Ⅳ using as substrate a similar waste stream studied in Chapter II added of C source to support microalgae growing in mixotrophic, i.e. glycerol, mode was conducted. Phaeodactylum tricornutum was selected since this strain can grow in mixotrophic condition in the presence of diverse organic compounds and it has been included among potential candidates for biodiesel production due to its high lipid content. Thus, this chapter represents an attempt to assess the ability of the algae P. tricornutum to grow mixotrophically and providing comparison with autotrophic condition.