EPSRC Industrial CASE award - Optimisation of lipid productivity and extraction in microalgae

Current research shows that algae have great potential as a resource for bioremediation, energy generation and carbon dioxide mitigation. In comparison to traditional bioenergy crops, they have a number of advantages. They can sequester CO2 at significantly higher rates than terrestrial plants (five per cent solar energy capturing efficiency compared to 0.2 per cent). They can also assimilate nutrients and other micro-pollutants from wastewater and brackish water and therefore do not place the same demands on potable water supplies or supplementary nutrients.

In addition, several strains of microalgae have been found to contain up to 40 per cent by mass of oils (as lipids) which can be converted into biodiesel. This compares to cereal crops which commonly contain between two and five per cent by mass. Despite these characteristics there remains a number of engineering challenges to integrating and optimising the processes of remediation, cultivation and downstream processing. By overcoming these challenges, we aim to substantially improve the commercial viability and the environmental sustainability of producing energy from algae.

This interdisciplinary research will address several key opportunities for achieving sustainable process integration. Wastewater from anaerobic digestion processes contains high concentrations of nutrients together with a wide variety of organic and inorganic contaminants. Wastewaters from a variety of AD processes will be characterised with a view to identifying those sources with optimal nutrient composition and minimal inhibitory or toxic compounds.

While there are benefits to using wastewaters for algal cultivation, issues such as microbiological contamination, fouling and light transmission efficiency may result in modifications to the design and operation of the PBR. These issues will be evaluated using bench scale tests and pilot scale PBR. Results will be used to make recommendations for commercial scale applications.

There is some evidence to suggest that the concentration of lipids within the algae cells increases as a reaction to environmental stresses. Nutrient composition, the quality and intensity of light and temperature can increase lipid productivity within the algae cells. This research will use a pilot scale bioreactor to evaluate the impact of varying operational parameters on lipid productivity. Results will be used to address the balance between effective bioremediation and lipid productivity from a biochemical, economic and energy perspective.

The extraction of oil from algae is generally considered to be the dominant rate limiting step in the production of biofuels from algae. Traditional methods are time consuming, costly and have a number of environmental and health and safety implications resulting from the use of solvents.

This research will evaluate a state of the art ultrasonic cavitation device on the disruption of algae cells and subsequent extraction and separation on oils. This element of the project is dedicated to improving the understanding of the physical and biochemical mechanisms of ultrasonic lipid extraction.

The impact of amplitude and contact time on cell wall structure, lipid extraction, preservation of high value co-products and phase separation will be assessed. The data obtained will be used to make recommendations for an application specific design and operating protocol.

There are currently four industrial partners who are supporting this project both in terms of expertise, access to commercial scale processes and historical data, In additions partners have also contributed equipment to the project (a 400 litre pilot-scale PBR and commercial scale sonicator). All partners are SMEs.

Partners include:

Varicon Aqua Solutions - specialists in aquaculture and algaculture and design/production of commercial scale continuous algae production processes.

Enpure Ltd - Process engineering company in the energy and environment sector.

Organic Resources Agency (ORA) - provides innovative and sustainable waste management solutions to public and private sector.

New Horizons Global - A UK company operating the biotechnology sector, exploiting new technologies and science.

Process integration offers the greatest opportunities for transformative change in the production of energy from algae. This research will make a valuable contribution to knowledge in this area.