Economical review of Haematococcus pluvialis culture in flat-panel airlift photobioreactors

Abstract

The cultivation of Haematococcus pluvialis NIES-144 in a flat panel airlift photobioreactor (FP-ALPBR) was examined based on its economical performance. Several cost-cutting options were proposed with the objective of maximising the profit. The use of natural lighting was inevitable to avoid the high electricity cost and replacing artificial lighting with sunlight was found to decrease the total production cost by as much as 307 US$ per 0.5kg dry cell in the 50L FP-ALPBR. Nevertheless, the lack of control of diurnal light intensity resulted in a drop in the growth performance with cell density decreasing from 387×104 to 140×104cellmL−1, and specific growth rate from 0.63 to 0.53 day−1. Reactor size appeared to be significant for the profitability of the system, and enlarging the FP-ALPBR from 17 to 200L required significantly lower total costs of production per year (121 US$ per 0.5kg dry cell for 200L culture when compared to 197 US$ per 0.5kg dry cell for the 17L system). Unfortunately this had to be compensated by a drop in the growth performance with cell density decreasing from 290×104 to 147×104cellmL−1 and specific growth rate from 0.49 to 0.47 day−1. Finally the reuse of spent medium with proper replenishment of nutrients (nitrate, phosphate, chromium, selenium and copper) caused an unexpected 30% drop in the growth rate and did not seem to provide an attractive response as the total cost per 0.5kg dry cell was only saved by 8 US$ a year.