Low-cost and versatile sensor based on multi-wavelengths for real-time estimation of microalgal biomass concentration in open and closed cultivation systems

Abstract

Microalgae show great potential as a bioresource for modern agriculture since its farming can be performed in lands with soil, water, or climate that are not suitable for conventional crops. A current challenge in algae farming is the real-time monitoring of biomass production to control parameters which are important to sustain a fast microalgae growth and high biomass productivity. Laboratory-scale methods developed for the determination microalgal biomass concentration lack the scalability required for monitoring large algae farms. Thus, this study proposes a low-cost and versatile sensor for real-time monitoring of the optical density of microalgae cultures in open and closed cultivation systems. The optical density unit of the sensor was based in ultraviolet and near-infrared wavelengths, and the validation of sensor measurements was performed correlating its response with a spectrophotometer. The sensor showed strong linearity and precisely measured the biomass concentration in dry weight basis (DW) in the range of 40–800 mg L⁻¹. The sensor-based on multi-wavelengths was conceived with an automatic sampling unit that works continuously and neither requires manual intervention nor sample dilution. The proposed system is cheaper than usual devices used for microalgae biomass quantification and compatible with the Internet of Things concept, data loggers with RS-232, universal serial bus, and analog inputs.