(768d) Techno-Economic Assessment of Microalgae Biorefineries for the Production of High Value Chemicals

Microalgae attract attention over the last years due to the need for alternative sources for fuels, chemicals and energy. Their major advantage over other sources of biomass is their non-competitiveness with the food sector. They require water, sunlight, nutrients and carbon dioxide to grow and their wide product portfolio renders them an exceptional source of biomass for the biorefinery concept. Furthermore, microalgae biorefineries can be integrated with current industrial applications or even other types of biorefineries.

The design of microalgae biorefineries is a challenging field and the valorization of specialty chemicals, in particular, enhances the challenge due to their unknown thermodynamic properties and the advanced technologies employed for their processing. The lack of industrial applications to draw knowledge is a significant drawback, thus extensive interaction with practitioners is of vital importance. This study capitalizes specifically on that and addresses the integrated design of a microalga biorefinery employing commercial simulation software (Aspen Plus v8.6). The design is developed under the D-Factory, an FP7 collaborative project, which aims at developing a commercial scale biorefinery process. Microalga Dunaliella is an exceptional candidate for such an incentive, since it has already been commercialized for its high value chemicals. Additional promising candidates are Nannochloropsis and Haematococcus, both offering wide range product portfolios of specialty chemicals. Nevertheless, challenges concerning the synthesis and the consequent design are evident in this study in regard to involved technologies and formulation of the product portfolio. Both advanced (e.g. high-performance countercurrent chromatography) and more conventional technologies (e.g. distillation) are employed in order to recover the desired products from the microalgal cells. The competitive chemistries present in microalgae add to the challenges related to the formulation of the product portfolio, thus the products selected should coincide with this restriction as well as with any limitations concerning the suitable selection of technologies.

For the purpose of this study, the capacity of each plant is set at 1kt per year of microalga biomass and the product portfolios consist of glycerol, carotenoids (β-carotene, lutein, astaxanthin etc.) and lipids (chlorophylls, EPA, DHA, PUFAs etc.). In their majority they are considered specialty chemicals and can find use in the pharmaceutical, cosmetic and nutraceutical sector. The residue after the recovery of the aforementioned compounds is rich in proteins and it is regarded as a co-product for its use as animal feed. The designed biorefineries are further studied as to their economic sustainability by calculating capital and operating costs. The cumulative cash flow diagram, starting from the construction of each plant, provides a very promising picture. Even though the evaluation is still at an early stage, as is the design of microalgae biorefineries in general, useful information is extracted which can lead to more accurate results in the future.