## 1 Introduction  
The use of microalgal biomass as a source of bulk, commodity chemicals has been of great interest since 1980, when the crude oil price reached almost $125 per barrel [1]. During the following decades, a plethora of companies invested heavily to explore the realities of microalgae-derived biofuels [2], initially claiming that the results were within near reach. In 2008, when the oil price reached its maximum of $163.80 per barrel, despite giving hope to the entire field of research, the harsh reality of process economics failed to overcome the fundamental operational problems with productivity and production costs. Put simply, microalgal biomass productivity was not sufficient, the scales involved were too small and extraction, purification and processing costs were too high. Facing the brutal realities of capitalism, the majority of companies working in this domain went bankrupt or were re-positioned as producers of higher value algae-derived products, predominantly for use as foods, feeds, nutraceuticalals, or cosmetics [2]. There are still a few companies working on biofuels derived from microalgae, but the stark reality is that the process will need to be coupled with the production of one or more additional market-need driven products in order to balance the economics. Indeed, it could be argued it would be a folly to put the lowest value product at the fore-front of the industrial process, and priority should rightly be given to maximising the economic returns on the higher (perceived) value compound(s), rather than the low value product to be burned for energy. Taking this line of reasoning to its logical conclusion,the mass scales often quoted that are required for a single biofuel product from microalgae, are thus moot and irrelevant. For example, the size of land that should be dedicated to microalgae cultivation for bio-oil production in order to produce enough necessary to satisfy USA demand alone, is estimated to be about 30 million acres, which is about the size of the State of Florida (1% of US land) [3]. Barring the whimsical and unprecedented reallocation of terrestrial infrastructure and resources to cultivation of microalgae, smaller production facilities (land or ocean based) are likely to be favoured, with the outputs of significantly higher value than liquid fuels. Most biofuels produced by the process are likely to be consumed by the process itself or used to run the plant (running pumps, heating, cooling, etc.) in a circular energy economy, rather than sold as a product. Alternately, a distributed model of production where biomass is used to produce fuels potentially for use within a local defined radius to power, for instance, municipal vehicles, is coupled to the production of a higher perceived need resource or environmental remediation service, such as nutrient remediation or cleaning water, could lead to an economically favourable operation. Under the latter scenario, any fuel that is generated from the growth of microalgae produced as a result of nitrate and phosphate remediation acts as added value against the operational efficiency of cleaner water production [4]. The process of fractionating products from biomass for different applications is called a biorefinery. A biorefinery is \"the sustainable processing of biomass into a spectrum of bio-based products (food, feed, chemicals, materials) and bioenergy (b biofuels, power and/or heat)\" [5]. While a microalgae biorefinery will take its inspiration from the crude oil refineries where every fraction is used predominantly for fuel-based products [6], the emphasis can never be on simply oxidising carbon chains to release energy but, rather, exploiting the complex organic compounds generated for their metabolic properties.