Yes. 15 times what is currently produced still wouldn't put much of a dent in oil consumption and wouldn't likely even keep up with the rate at which oil consumption increases.
It will need to be produced on a much larger scale than that.
The nice thing about marine algae, it that it can be grown in salt water which doesn't use up fresh water resources which are relatively scarce in some areas. It also doesn't face the same problems of land use because it can be grown in the ocean.
And although the algae is grown from CO2, when algae diesel is compressed in a diesel engine with super heated 02, the byproduct is C02. So if you really want to reduce C02, shouldn't you just grow algae and leave it alone?
When we burn oil, we release CO2 that was removed from the carbon cycle long ago. That increases the amount of CO2 in the atmosphere.
When you burn a biofuel, you release CO2 that was already currently in the carbon cycle, and would be released as the plants decomposed or were used anyway, unless sequestered somehow.
The real benefit of using biofuels in from not using fossil fuels instead which would add more CO2 into the carbon cycle.
However, using C02 to grow algae doesn't sequester CO2 unless the algae, or it's remains are sequestered.
As the appetite for oil grows, it won’t matter where it came from if we reach the tipping point; oh, how many times in my youth, on some overheated assignation, did I long for that sweet tipping point...