(424d) Techno-Economic Viability of a Multi-Product Algal Biorefinery

The vast majority of research activities involving algae are focused on the selection and modification of strains as well as cultivation aspects for biofuel purposes. A severely underdeveloped aspect concerning algae is the concept of multi-product biorefinery. These concepts are theoretically able to harvest and valorize all/most algae components optimally. In order to achieve such a biorefinery, algal cell walls need to be opened and all/most components need to be purified. Furthermore, to maintain the functionality of high value compounds, mild disentanglement as well as the development of selective separation technology is a prerequisite. However, most developed algal biorefineries are mere block diagrams in which deeper insight in separation efficiency is lacking.  Moreover, it is of upmost importance to perform accurate techno-economic evaluations on these concepts in order to evaluate the potential of these algae multi-product biorefineries.

Approach

In order to obtain a deeper insight in the separation efficiency and use this knowledge to make accurate techno-economic estimates on the feasibility of an algal biorefinery, a mobile processing plant named VALORIE (the Versatile ALgae On-site Raw Ingredient Extractor) was built. By performing local pilot-scale biorefinery tests in this 20 foot intermodal container, it was possible to scale-up  lab separation technology to industrial scale unit operations. The mobile refinery is able to disrupt and process 1-5 kg DW/h algal biomass. Membrane separations as well as liquid-liquid extractions were performed for further separations between (soluble/insoluble) protein, (neutral/polar) lipids and carbohydrate fractions. Multiple components were purified from demonstration & pilot size (>0.5 Ha) algae cultivation ponds or reactors. Nannochloropsis sp. (grown in horizontal tubular reactors) was evaluated in terms of processing costs and possible ingredients that could be harvested and refined. More accurate biorefinery techno-economic estimates will be based on processing experience obtained from this pilot.

Results & Conclusions

Several crucial parameters within the algal biorefinery have been investigated, being cell disruption, handling large water streams as well as the influence of processing steps on protein functionalities. Initially several cell disruption methodologies were evaluated and, although energy consumptions were high, it was found that a mechanical disruption was the most versatile cell-wall disruption technology. Costs and efficiency of further processing of the algal fractions are assessed. At the conference an outlook is given on the economic viability of multi-product algal biorefineries.