Mixotrophy to grow more algae at a lower price

Producing algae is valuable, but expensive. Is it possible to raise the amount of algae biomass and lower the cost at the same time?

Thanks to Dr Fabian Abiusi, Algreen is investigating a growing technique that could help algae producers to twice the amount of biomass, spending less money: this is mixotrophy.

How does it work?

The autotrophic process that permits algae to grow needs to convert light and CO2 into carbon compounds, and releases oxygen as by-product. For this reason, ventilation is necessary to provide CO2 and remove oxygen. Some microalgae can be cultivated in heterotrophy, without light and using sugars as carbon and energy source. In this process algae consumes O2 and produced CO2. Also in this case ventilation is necessary to provide O2 and remove CO2. In both cases the required ventilation is an important cost of production.

Mixotrophy combines autotrophic and heterotrophic production of microalgae. In this way, the by-product of one process serves as the resource for the other one. Thanks to experiments on Chlorella sorokiniana and Galdieria sulphurariain close photobioreactor, Dr Abiusi discovered that in mixotrophy dosing the addition of sugar is possible to operate the bioreactor without ventilation. Instead of sugar, also waste streams from the food industry could be used, increasing the sustainability of algae production.

How much can we save?

Mixotrophy allows to use sunlight with the same efficiency that an autotrophic culture while doubling its biomass productivity. According to Dr Abiusi estimation, increasing biomass productivity and removing ventilation is expected to half microalgae production cost.