Rethinking glasshouse horticulture with algae
Spirulina, a natural blue dye
Flemish and Dutch greenhouse horticulture have entered a transition phase. Rising costs and increasing global competition puts local farmers under pressure. The blue chain aims to re-boost the greenhouse sector by developing an alternative for current cultures. In particular, the microalgae Spirulina shows great potential because it is rich in phycocyanin, which is a natural blue dye. Phycocyanin is a potential alternative for the more artificial dye brilliant blue (E133), which can be linked with hyperactivity and other health risks. Therefore, several industries like the paper, textile, and food industry have shown great interest in Spirulina.
Valorisation of waste water
The cultivation and valorisation of Spirulina is a first aspect, but valorisation of the spirulina waste water, is a second aspect of the blue chain. The second can be done by cultivating duckweed, as these aquatic plants are naturally adapted to take up nutrients from waste water and in return clean the wastewater. The greatest assets of duckweed are its fast growth (5 – 20 ton dry weight (DW) ha-1 y-1, its high protein content (15 – 45 %), and its excellent amino acid composition for both food as feed. Taking all these assets into account, duckweed has a great potential to valorise waste water.
The blue chain will not only focus on Spirulina waste water, but different agricultural waste waters will be analysed for their use as duckweed and spirulina medium. Up till now, aquaculture effluent of Zander production has shown suitable for duckweed production. In a cascade experiment of 3 cubicontainers (1.2 × 1.2 × 1.2 m) containing this effluent, 2.2 kg DW of duckweed was produced which corresponds with a full scale production of 6 ton DW ha-1 y-1. More effluents from different agricultural sectors are analysed like for example the liquid fraction of swine manure before and after anaerobic fermentation.
Pilot-scale experiment
In the following growing season a pilot-scale experiment will be carried out. The pilot has a size of 140 m² and will contain nutrient rich water. In this way the project will try to reduce the gap between research and practice and also give relevant results for an outside growth in Belgium and the Netherlands in outside conditions.
Author: Reindert Devlamynck