6. Other Technologies

6.4. Algae

Biodiesel production from Microalgae

Microalgae are microscopic photosynthetic aquatic organisms. Like terrestrial plants, microalgae use energy from the sun for photosynthesis, thereby converting solar energy into stored chemical energy. Microalgae are efficient converters of solar energy because of their simple cellular structure. They are of interest for biofuels production because of their high growth rates, tolerance to varying environmental conditions and high oil content; the oil can be extracted and converted into biodiesel. Algal species have been isolated that have an oil content of up to 50%, which is much higher than any terrestrial plant species1. Yields per hectare from algae are predicted to be at least an order of magnitude greater than any terrestrial crops2 (e.g. oil palm - 6000 litres oil/hectare; algae 90000 litres oil/hectare). The advantage of algaculture over terrestrial crop-based biofuels is that it does not necessitate a decrease in food production as it does not use farmland. Many algal species can grow in brackish water or seawater and will not put a strain on fresh water supplies.

References

1. Sheehan, J, Dunahay, T, Banemann J and Roessler, P. A look back at the U. S. Department of Energy Aquatic species program -Biodiesel production from Algae. NERL/TP-580-24190. National Renewable Energy Laboratory, Golden, CO, 80401, USA. July 1998.

2. Haag, AL. Algae bloom again. Nature 447: 520-1 (31 May 2007).

 

Biogas production from Macroalgae

Anaerobic digestion is a natural process by which microorganisms break down biodegradable material in the absence of oxygen. This process produces "biogas" which consists mainly of methane (50%-80%) and carbon dioxide (20%-50%)1. Methane is the major component of the "natural gas" which is used across Europe for heating, cooking and in power stations to produce electricity. If this process occurs in a controlled environment, so that the resulting gas can be captured and stored, then the methane produced can be used as a renewable fuel source. Nutrient-rich bi-products are produced during the anaerobic digestion process which can be used as an agricultural fertiliser.

Almost any organic material can be processed by anaerobic digestion. This includes biodegradable waste materials, such as waste paper, grass clippings, leftover food, sewage, animal waste and macroalgae (marine seaweed). One advantage of using marine algae as the feedstock over terrestrial plants is that it overcomes the displacement of food crops with biofuel crops, because marine algae need neither land nor fresh water.

References

1. Kelly, MS and Dworjanyn, S. (2008) The potential of marine biomass for anaerobic biogas production. [online] http://www.thecrownestate.co.uk/newscontent/92-marine-biomass-report.htm

llp logoThis project has been funded with support from the European Commission (EU Lifelong Learning Programme Agreement no LLP/LdV/TOI/2009/IRL – 515). This publication reflects the views only of the author, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

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