Abstract
Marine macroalgae such as Ulva intestinalis have promising properties as feedstock for cosmetics and pharmaceuticals. However, since the quantity and quality of naturally grown algae vary widely, their exploitability is reduced – especially for producers in high-priced markets. Moreover, the expansion of marine or shore-based cultivation systems is unlikely in Europe, since promising sites either lie in fishing zones, recreational areas, or natural reserves. The aim was therefore to develop a closed photobioreactor system enabling full control of abiotic environmental parameters and an effective reconditioning of the cultivation medium in order to produce marine macroalgae at sites distant from the shore. To assess the feasibility and functionality of the chosen technological concept, a prototypal plant has been implemented in central Germany – a site distant from the sea. Using a newly developed, submersible LED light source, cultivation experiments with Ulva intestinalis led to growth rates of 7.72 ± 0.04 % day−1 in a cultivation cycle of 28 days. Based on the space demand of the production system, this results in fresh mass productivity of 3.0 kg m−2, respectively, of 1.1 kg m−2 per year. Also considering the ratio of biomass to energy input amounting to 2.76 g kWh−1, significant future improvements of the developed photobioreactor system should include the optimization of growth parameters, and the reduction of the system’s overall energy demand.
Highlights
The green alga Ulva intestinalis is a typical representative of Chlorophyta and grows on rocky ground or as an epiphyte in the intertidal zones of nutrient-rich marine waters (Budd and Pizzola 2008)
When developing the presented photobioreactor system, special focus was laid on the provision of optimal abiotic cultivation parameters for marine macroalgae, the reduction of freshwater demand to a minimum, and the realization of an energyefficient production system with limited space demand
The selected process technology allows for the adaptation of parameter values to the physiological needs of the specific macroalgae type being cultivated
Summary
The green alga Ulva intestinalis is a typical representative of Chlorophyta and grows on rocky ground or as an epiphyte in the intertidal zones of nutrient-rich marine waters (Budd and Pizzola 2008). Marine aquaculture is widely established but lacks the means to control cultivation parameters (Hafting et al 2015): Algae growth rates are determined by oceanographic and meteorological parameters as well as the prevailing water quality in the production area (Buck and Grote 2018). The crop quantity and quality are increasingly limited by the effects of climate change and ocean acidification (Kelly and Hofmann 2013) as well as proliferating pathogens, epiphytes, or herbivores (Hurd et al 2014; Hafting et al 2015; Kerrison et al 2015; Fernand et al 2017). These negative factors can be mitigated by cultivating algae in land-based
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