Ashiwin Vadiveloo

Sustainable cultivation of microalgae by an insulated glazed glass plate photobioreactor

Microalgae growth in closed photobioreactors is greatly inhibited by elevated temperatures caused mainly by the infra‐red portion of light. Current passive evaporative cooling systems for temperature control in outdoor photobioreactors are neither economical nor sustainable. Here we built a novel flat plate photobioreactor with its illumination surface customized with insulated glazing units (IGP). The IGP design enabled transmission of more than 50% of visible light while blocking 90% of ultraviolet and infrared radiations. The growth and productivity of Nannochloropsis sp. (MUR 267) in the IGP was compared against conventional flat plate photobioreactors subjected to the full spectrum (HLP) and also externally modified spectrum (CLP) of halogen lights. High temperature (up to 42°C) resulted in no growth in the HLP. Biomass productivities of Nannochloropsis sp. grown in the CLP was significantly higher than the IGP due to higher light transmission and lower temperature profiles recorded in the CLP. Lipid content of Nannochloropsis was highest in the CLP (60.23%) while protein was highest in the IGP (42.43%). All photosynthesis parameters were negatively affected in the HLP. The IGPs ability to remove infrared (heat) makes this newly developed photobioreactor a promising and sustainable cultivation system for mass algal production especially for high value products.

Macroalgae culture to treat anaerobic digestion piggery effluent (ADPE).

Environmental consequences of high productivity piggeries are significant and can result in negative environmental impacts, hence bioremediation techniques (in particular using macroalgae) are therefore of great interest. Here, the growth potential of several freshwater macroalgae in anaerobic digestion piggery effluent (ADPE), their nutrient removal rates and biochemical composition of the biomass were investigated under outdoor climatic conditions. A consortium of two macroalgae, Rhizoclonium sp. and Ulothrix sp. was isolated and could efficiently grow in the ADPE. Maximum ammonium removal rate (30.6±6.50mg NH4+-NL-1d-1) was achieved at ADPE concentration equivalent to 248mgNH4+-NL-1. Mean biomass productivity of 31.1±1.14g ash-free dry weight (AFDW) m-2d-1 was achieved. Total carbohydrate and protein contents ranged between 42.8-54.8 and 43.4-45.0% AFDW, respectively, while total lipid content was very low. The study indicates the potential use of this macroalgal consortium for treating ADPE as well as source of animal feed production.