PhD Project:

Low Cost Algae Harvesting Technologies

The primary constraint to the commercialisation of biodiesel from microalgae is production cost. Harvesting alone can account for 30% of the cost of the biomass product. Harvesting is particularly challenging due to the small amount of algal biomass produced, relative to water volume. This currently exacts high energy and cost demands. Foam fractionation has potential as a low cost and low energy harvesting technology. Microalgal cells adsorb to the surface of a stream of fine air bubbles, which rise up a closed column, discharging the concentrated product at the top. Foam fractionation significantly reduces construction, maintenance and energy costs compared to other harvesting technologies. Current work has demonstrated the efficacy of foam fractionation.

Harvesting Chorella sp. can be optimized with the addition of the surfactant cetyl trimethylammonium bromide (CTAB) as an aid to flotation. Combining low levels of CTAB (10 mg/L) with slow air flow (100 L/h) allowed for long foam residence times within the column, optimizing water drainage. Harvesting concentration factors of 298 were achieved within 25 minutes. Currently the effect of the surfactant on recoverable lipids is being investigated. These results indicate that foam fractionation offers considerable potential as an efficient, low cost and scalable harvesting technology.

For more information please contact Dr Jon Lee.

A dense concentrate of algae cells after harvesting	Microalgae being collected during a foam fractionation experiment
Growing microalgae in the culture room	Foam fractionation unit was featured on BBC One's Country File