Determination of Evaporative Loss in Revolving Algal Biofilm Systems

Microalgae has tremendous potential in the production of products ranging from biofuels to pharmaceuticals and food. Algal cultivation has been mainly performed in an open pond or bioreactors, but recently, an attachment based Revolving Algal Biofilm (RAB) cultivation system was developed that not only demonstrated a better biomass productivity, but had more harvestable area. The downside of this system however is the high evaporation rate. The objective of this research was to develop a model to accurately predict evaporation from the developed algal growth systems. A model was developed to evaluate the evaporative water loss rate for varying environmental parameters that include solar irradiance, ambient air temperature, wind speed and relative humidity. A week long simulation of the model was performed using the algal systems at a greenhouse facility at Boone, Iowa, USA. The range of the evaporative water loss from the system was approximately 1.89L/m²day, 0.95 L/m²day, 3.67 L/m²day for the Raceway pond, RAB in Raceway system and Trough RAB respectively. The model was considered to a beneficial tool to explore the performance and utility requirements of a greenhouse raceway and cultivation systems under varying environmental conditions.