Cultivation of microalgae on artificial light comes at a cost

Microalgae are potential producers of bulk food and feed compounds, chemicals, and biofuels. To produce these bulk products competitively, it is important to keep costs of raw material low. Light energy can be provided by sun or lamps. Sunlight is free and abundant. Disadvantages of sunlight, however, include day/night cycles, changes in weather conditions, and seasonal changes. These fluctuations in irradiance can be prevented by applying artificial lighting. Artificial lighting will not only increase productivity but will also increase costs associated with microalgae cultivation. This cost increase is recognized, but a detailed quantitative evaluation was still missing. The costs and energy balance related to microalgae cultivation employing artificial light was evaluated with a literature study. We calculated that current application of artificial light will increase production costs by 25.3 $ per kilogram of dry-weight biomass. From these calculations, it was determined that 4% to 6% of energy from electric input is fixed as chemical energy in microalgae biomass. Energy loss and increased production cost may be acceptable in the production of high value products, but in general they should be avoided. Microalgae cultivation programs should therefore focus on employing sunlight. (C) 2013 Elsevier B.V. All rights reserved.