Economic feasibility study for artificial lighting of microalgal flat-panel photobioreactors

Abstract

Lightning belongs among critical process parameters that significantly affect growth and microalgal yield in photobioreactors. Sunshine or artificial lighting is applied to irradiate photobioreactors. Nevertheless, sunshine lighting is limited by locality and weather conditions. On the contrary, there is a typical demand for nonstop or 8000 annual working hours for industrial biorefineries using photobioreactors as an economic point of view. Thus the paper scopes to evaluate the fundamental economic feasibility of artificial lightning provided by electric energy from fossil fuels, renewable energy systems, or their mutual combinations. The economic feasibility is discussed concerning local annual sunshine hours for a model 1-ha microalgae cultivation plant. It was found that combined sunlight, solar energy- and electric energy-based artificial lighting has a significant positive effect on the economic behavior of a model biorefinery. The mutual combination of sunshine, solar energy- and electric artificial energy-based light evinces a profit increase of 2.18 for microalgal powder, 3.09 for microalgal lipids and 4.11 for microalga carotenoids production technologies all compared only to sun lighted photobioreactors. Nevertheless, capital investments in artificial lightings, solar systems, or photobioreactors, and high operating expenses represent the dominant risk factors of the discussed microalgal biorefinery. Developing cheap and reliable artificial lighting systems, solar and energy storage systems, and improving process characteristics of microalgal cultivation (process stability, high concentrated suspension in thin layer photobioreactors avoiding biofilm formation) were identified as the essential research needs and challenges to improve the economic feasibility of artificially lighted microalgal biorefinery.

Recent advances and fundamentals of microalgae cultivation technology

“…They provide efficient lighting and CO 2 fixation by pushing microalgae through a thin layer. [48,[75][76][77] In a recent study, the light pass and photosynthetic activity of Chlorella vulgaris in variously shaped thin layers were analyzed theoretically and experimentally. [51] The results showed that the V-shaped configuration outperforms the flat panel, increasing productivity from 20.7 to 52.0 g m −1 day −1 in the laboratory settings.…”

“…Energy used for microalgae cultivation and capital expenses represent the major factors contributing to the production cost. [47][48][49] Consequently, CO 2 emissions may be utilized as an indirect measure of manufacturing efficiency for the same final product even though they are not a direct predictor of cost.…”

“…The optimal regions for outdoor algae production are the Middle East, western South America, eastern North America, North and East Africa, the Caribbean, and Oceania; [48,169] in contrast, hotter or colder regions, like the Iranian desert, [64,170] or regions with less light, like Canada or Russia, are less favorable. [50,171] However, microalgae are found everywhere and adaptation of such species for local use can ameliorate weather conditions.…”

“…They provide efficient lighting and CO 2 fixation by pushing microalgae through a thin layer. [ 48,75–77 ]…”

“…[45] Indeed, careful life cycle assessment, optimization of the cultivation conditions and selection of end-products significantly reduce the cost and energy requirements. [43,46,47] Crucially, economic characteristics might fluctuate significantly based on specific circumstances, such as the use of ponds or photobioreactors for cultivation, [41] combinations of natural or artificial light sources, [47,48] or the application of various microalgae strains and drying methods. [49] Therefore, in order to make algae more competitive with conventional food and energy sources, it is crucial to continue developing microalgae strains with the needed properties and to develop novel production procedures.…”