Microalgae oil production is the subject of intensive worldwide research and development, with several billion dollars invested in the past few years. Many different approaches and technologies are being investigated:
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Growing microalgae on sunlight and CO2 in enclosed photobioreactors (tubes, bags, panels, etc.) or open ponds,
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Growing algae in the dark by fermentations of sugar and starches,
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Hybrid systems using both sunlight and sugar or starches, and even
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Processes using artificial lights.
Microalgae are isolated from nature and then selected or genetically modified for high vegetable oil (triglyceride) content and productivity. Some projects use genetic engineering to design microalgae strains that excrete actual hydrocarbons, which can then be recovered without need to harvest or even produce algae biomass. Many types of microalgae are being investigated, and several companies and projects are currently moving into pilot and even demonstration projects.
Over a score of Life Cycle Assessment (LCA) studies on microalgae oil production have been recently published, with a majority, but not all, concluding that algae biofuels could substantially reduce greenhouse gas emissions, compared to fossil fuels. However, with the exception of fermentation processes (using sugar or starch as inputs), there is essentially no algae oil currently produced beyond small sample amounts for testing purposes. Thus, all LCA studies are based on extrapolations from laboratory experiments, small-scale outdoor studies, and, mainly, on assumptions and projections of future technological advances. A more crucial problem is that these studies have not been based on engineering designs and systems analysis, required to derive energy inputs and mass balances.
A detailed LCA of microalgae oil production using open ponds, based on a recent detailed engineering and economic cost study, will be presented. It concludes that algae vegetable oil could be produced with essentially no fossil energy inputs or net greenhouse gas emissions, based on realistic productivity, scale, site and operating assumptions. This LCA will be compared to others available in the open literature.
