Continuous Oscillatory Baffled Photobioreactors

The majority of biodiesel is produced by the transesterification of vegetable oil or animal fat/oil. The majority of the vegetable oil is extracted from rape seeds, sunflower seeds or soya beans. At present 0-20% of diesel sold on the forecourt of garages is biodiesel, depending which country/area you live in. If all diesel sold in the world was 20% biodiesel, it would barely be possible to find enough land on which to grow the necessary oil seed crops. The problem is that in a field only 10 mass% of the plant is oil and the rest is waste vegetable matter. Whilst it may be possible to gasify the waste vegetable matter and ultimately produce bio-ethanol the energy density of the crop remains low.

There are a number of species of algae that also produce vegetable oils as an energy storage mechanism. One species even produces a C34 straight chain hydrocarbon. The oil content of the algae can be as much as 65 mass% of the organism. Even if only 40 mass% of the algae was oil it would be possible to grow the entire world production of oil (800 billion barrels) in a square 1600 km x 1600km (Approximately 2.5% of the available surface area). The reason why algal production of oil has not been adopted as a method of producing biodiesel, is the cost of the very large bioreactors needed to grow the algae over 4-5 days.

Oscillatory Baffled Reactors (OBRs) are an intensified from of plug flow reactor. Their niche application is the performance of long reactions in continuous, plug flow mode. Bioreactions are one class of reaction that is inherently “long”, so should be suitable for processing using an OBR.

Efficient growth of algae for biofuel is a substantial challenge that an OBR-based photobioreactor may be able to contribute to, as, further to the OBR’s suitability for long reactions such as this, it also offers good exposure to light due to its periodic regular mixing patterns, low and controllable shear and a relatively low energy consumption (compared to stirred tanks).

The aim of this project is to design, build and evaluate an OBR-based photobioreactor for algae growth.

For more details, please contact Prof Adam Harvey or Dr Jon lee.