So why make Biodiesel out of Algae?  Why not just continue biofuels out of other plants as well as just continuing to use fossil fuels? Well, the answer lies in what most factories produce, and that is CO₂. The problem with Co₂ is that it's a greenhouse gas and it absorbs a lot of heat and it's the second highest contributor to climate change topped only by water vapor and clouds.  The next problem with it is that it doesn't go away for at the very least 35 years up to 90 years. So want can algae do about all of this? Algae to survive takes in CO₂  and converts it to O₂ and it is one of the most efficient plants. 70-80 % of all air is produced by algae in the ocean.