Efficient Algae: The Next Biofuel? Microalgae Are Grown in Australia to Produce High-Value Dietary Supplements. Now, They Are Being Touted as a Source of Renewable Energy to Replace Fossil Fuels
Taylor, Robin, Ecos
Plant-based sources of biofuels, such as soybeans, canola and palm oil, compete with food crops for land, water and nutrients. In contrast, microalgae production does not require arable land; it can be grown in saline or waste water. Grown on an industrial scale, microalgae has the potential to produce the same amount of biofuel as current plant-based sources, using significantly less land area.
Like plants, algae use photosynthesis to turn carbon dioxide into carbohydrates, some of which are transformed into complex organic molecules such as lipids (fats and oils). Lipids can be used as feedstock for biofuels. Several Australian groups are already investigating ways to produce biofuels such as biodiesel, biomethane and biohydrogen from microalgae. The next step in the commercialisation process will be pilot plants to test the performance of algal strains and reactors.
Producing algal biodiesel
Algal biodiesel is produced in a similar way to biodiesel from other sources. Algal biomass is grown using an appropriate algal strain and growth conditions, and oil is extracted from the algal biomass in a chemical process known as transesterification. Compounds called triglycerides in the extracted oil have the potential properties of fossil diesel. In a detailed lifecycle analysis, CSIRO scientists have shown that it is theoretically possible to produce algal biodiesel with significantly lower greenhouse gas emissions than fossil diesel.
The cost of producing algal biodiesel is not yet competitive with mineral diesel. Research into lower cost technologies, combined with higher future diesel prices, may allow algal biodiesel to be produced at a competitive cost. However, considerable R&D is needed before these models become a reality.
Dr Tom Beer, of CSIRO's Energy Transformed Flagship, estimates that based on Australia's annual transport fuel consumption of 30 billion litres--and assuming high algal growth rates of 110 t/ha/year and 30 per cent oil content--100 square kilometres of algal ponds could provide all of Australia's fuel needs.
Chair of the Algal Fuels Consortium, Associate Professor Rob Thomas, believes that algal fuels could provide about 10 per cent of Australia's diesel fuel needs. The consortium, made up of CSIRO, Flinders University, the South Australian Research and Development Institute (SARDI) and Flinders Partners, is developing a pilot scale production unit using seawater ponds on Torrens Island, next to a gas-fired power station. The consortium, which is looking for a new industry partner following the withdrawal of their investor, won a $2.7 million research grant from the Department of Resources Energy and Tourism in 2009.
Assoc. Prof. Thomas says the pilot facility will be about 1 hectare in size, and will operate for two years before scaling up to a 10-hectare pre-commercial facility. The consortium aims to produce 10 000 to 20 000 litres per year of algal oil: enough to test the oil as a suitable biofuel feedstock.
As well as the planned project on Torrens Island, SARDI has also recently opened a $5 million photo-bioreactor facility at its Aquatic Sciences laboratories at West Beach. (1)
Biodiesel properties of different strains
Researchers at the Australian National Algae Culture Collection have been studying oils in microalgae since the 1980s, initially for the developing aquaculture industry: microalgae are the source of the omega-3 oils extracted from fish that are sold as fish oil supplements.
Head of the Collection, Dr Susan Blackburn, says one of the reasons for the interest in algae for biofuel and other bio-applications is that they are such an easily renewable source, given the right temperature conditions, light and nutrients. But, until recently, the focus has been on the engineering side of how to grow algae, with little surveying of the best strains for the particular job. …