I agree with the user guru, the dry weight of the algal biomass is roughly about one-tenth of its wet weight.
I guess, the dry weight is usually determined by calculating the difference between the average dry weight retained on algal filter(DWA) and the average dry weight retained on control filter(DWC) )multiplied by the algal concentration (N) and volume of algal culture and filter seawater filtered algal and control filter(V).
Given the great difference in values it seems possible that you are defining your terms differently. 0.3 percent sounds more like the wet weight of the algae obtained per unit weight of the water. Maybe Yanzhou1 should define his terms for us.
Thus, gently stirring a culture, to assure algae get 1/10 sunlight and 9/10 shaded. However, maximum algae growth only requires 1/32 of sunlight. Consequently, you need the following amount of dry algae per year: of culture--water in the culture is very heavy compared to algae dry weight.
According to the method by IAEA. The algae left out after the centrifuge Shud be heated in dry heat sterlizer for 4 hrs @80 C. The mass left out wud be the dry weight of the algae. I am getting a dry mass of 1g/l(dry bases) which is approx. 1/8 of the wet mass.