PNNL

Abstract

Two innovative culturing systems, the LED-lighted and temperature-controlled 800 liter indoor raceways at Pacific Northwest National Laboratory (PNNL) and the Phenometrics photobioreactors (ePBRs) were evaluated in terms of their ability to accurately simulate the microalgae growth performance of outdoor cultures subjected to fluctuating sunlight and water temperature conditions. When repeating a 60 day long outdoor pond culture experiment (batch and sem-continuous at two dilution rates) conducted in Arizona with the freshwater strain Chlorella sorokiniana DOE 1412 in these two indoor simulators, it was found that biomass growth and productivity in the PNNL climate-simulation ponds was comparatively slightly higher (10-15%) but significantly lower (52-62%) in the ePBRs. Similarly, when the marine Picochlorum sp. was cultured in six replicate ePBRs at Los Alamos National Laboratory (LANL) and duplicate climate-simulation ponds at PNNL, using the same inoculum, medium, culture depth, and light and temperature scripts, the biomass productivity in the ePBRs was only about 65% of that observed in PNNL’s indoor ponds. Potential reasons for the divergence in growth performance in these pond simulators, relative to outdoor raceways, are discussed. In conclusion, the PNNL climate-simulation ponds provide reasonably reliable biomass productivity estimates for microalgae strains cultured in outdoor raceways under different climatic conditions.