Spirulina is an FDA (Food and Drug Administration) approved human health supplement and a popular superfood that is described as a powerful antioxidant.
Sustenso is an initiative that produces this nutrient-rich food while generating biofuel from green waste. With this new technology, it is possible to capture CO2 waste streams from biogas plants and feed it to spirulina, preventing the CO2 from being released into the atmosphere.
Over a million tonnes of green waste are composted every year in the Netherlands alone. This green waste is mainly converted into a substance called digestate. Its use is severely restricted and only a small portion is re-used as a fertiliser, while the majority is burned. The remaining by-products of green waste digestion are gasses: methane and carbon dioxide. The methane is collected and used as biofuel for household consumption. Currently, the carbon dioxide emitted through the transformation of green waste is simply rejected into the atmosphere.
To harness the potential of the by-products generated during the extraction of biofuel, Sustenso has started the construction of a biomass digester with a unique circular new property. The CO2 produced during the making of biogas is fed to a large tubular system containing algae: with sun and/or led light as the energy source. The photosynthetic algae, feeding on CO2, will then turn the carbon dioxide back into biomass. Once dried these microorganisms are known as spirulina, and find their way on our shelves as a green powder, one of the most nutrient-rich foods on the planet. Spirulina is commonly used as an additive in smoothies, yoghurt and coffee.
By experimenting with alternative bacterial species, this new digester could also produce other products ranging from proteins, vitamins to fodder and dyes.