First test flights using blends with algae oil are already carried out and expectations by the aviation and other industries are high. On the other hand technical data about performance of cultivation systems, downstream processing, and suitability of algae oil as fuel are still limited. The existing microalgae growing industry mainly produces for the food and feed market. Energy efficiency is so far out of scope but needs to be taken into account if the product changes to biofuel. Energy and CO2 balances are used to estimate the potential of algae oil to fulfil the EU sustainability criteria for biofuels. The analysis is supported by lab tests as well as data gained by a pilot scale demonstrator combined with published data for well-known established processes. The algae oil composition is indicator of suitability as fuel as well as for economic viability. Approaches attaining high value fractions are therefore of great importance and will be discussed in order to determine the most intended market. 1. Introduction The energy demand is growing worldwide. The total energy consumption has increased from 196？EJ (1018 Joule) in 1973 to more than 350？EJ in 2009 and the tendency is rising [1]. About 80% of this energy demand is delivered from fossil fuels with the consequence of an increase of greenhouse gas emissions in the atmosphere that provokes serious climate changes by global warming. Furthermore, the fossil fuels supplies are constantly diminishing. In consequence, the development of CO2-neutral fuels is one of the most urgent challenges facing our society and essential in order to meet the planned internationally specified targets, like the reduction of CO2 emissions in the range of 10–20% by 2020 (e.g., European Union). Therefore, there is an acute demand for sustainable, CO2-neutral resources to replace the demand of liquid fuels in the near future. The potential of microalgae as renewable source for biofuel production is very promising due to higher growth rates and the capability to accumulate higher amounts of lipids (from 20% until 80% of dry weight) [2] than conventional oil crops (not more than 5% of dry weight) [3] and therefore the oil yield per hectare obtained from microalgae can greatly exceed the yield from oil plants like rapeseed, palm, or sunflower. Another advantage of microalgae over plants is their metabolic flexibility. That means that a variation in the biochemical composition of the biomass (towards higher lipid, carbohydrates or protein accumulation) can be regulated by varying the cultivation conditions [4]. Photobioreactors
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