Global energy use has reached unprecedented levels and increasing human population, technological integration, and improving lifestyle will further fuel this demand. Fossil fuel based energy is our primary source of energy and it will remain to be in the near future. The effects from the use of this finite resource on the fate of our planet are only now being understood and recognised in the form of climate change. Renewable energy systems may offer a credible alternative to help maintain our lifestyle sustainably and there are a range of options that can be pursued. Biofuels, especially algae based, have gained significant publicity recently. The concept of making biofuels, biochemicals, and by-products works well theoretically and at small scale, but when considering scaleup, many solutions can be dismissed on either economical or ecological grounds. Even if an (cost-) effective method for algae cultivation is developed, other input parameters, namely, fixed nitrogen and fresh water, remain to be addressed. Furthermore, current processing routes for harvesting, drying, and extraction for conversion to subsequent products are economically unattractive. The strategies employed for various algae-based fuels are identified and it is suggested that ultimately only an integrated algal biorefinery concept may be the way forward. 1. Introduction For millennia, the only combustible fuel was wood, a biofuel. It enabled the first civilisations to flourish, powered the furnaces of the Roman Empire, and fuelled the Age of Discovery. Then, in 1698, the invention of the first practical steam engine sparked the Industrial Revolution. Biofuels were replaced by fossil fuels, initially coal and later crude oil and natural gas. Fossil fuels had the critical advantage of a significantly higher energy density (45？MJ？kg？1 for crude oil compared to 15？MJ？kg？1 for wood). The Industrial Revolution led to improved living standards and exponential population growth due to this abundance of cheap energy, eventually giving way to the modern day information revolution and globalisation. Today we live in a world powered by fossil fuels. Global population and energy demand continue to rise rapidly. Global population is projected to increase from 6.6 billion in 2008 to 9.2 billion by 2050, coinciding with a global primary energy demand increase from 13？TW to 28？TW in the same time frame. This comes at a time when we have discovered that fossil fuels are not the panacea that they were once believed to be. Proven crude reserves are dwindling and the end of cheap petroleum and diesel is
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