Promoting helix pitch and trichome length to improve biomass harvesting efficiency and carbon dioxide fixation rate by Spirulina sp. in 660 m raceway ponds under purified carbon dioxide from a coal chemical flue gas.

The helix pitch and trichome length of Spirulina sp. were promoted to improve the biomass harvesting efficiency and CO fixation rate in 660 m raceway ponds aerated with food-grade CO purified from a coal chemical flue gas. The CO fixation rate was improved with increased trichome length of the Spirulina sp. in a raceway pond with double paddlewheels, baffles, and CO aerators (DBA raceway pond). The trichome length has increased by 33.3 μm, and CO fixation rate has increased by 42.3% and peaked to 51.3 g/m/d in a DBA raceway pond. Biomass harvesting efficiency was increased with increased helix pitch. When the day-average greenhouse temperature was 33 °C and day-average sunlight intensity was 72,100 lu×, the helix pitch of Spirulina sp. was increased to 56.2 μm. Hence the biomass harvesting efficiency was maximized to 75.6% and biomass actual yield was increased to 35.9 kg in a DBA raceway pond.