Look it up: all the chemical energy in petroleum originally comes from saltwater algae. The original oil industry ran for thousands of years. It involved an indirect method of harvesting saltwater algae called whaling. It was highly profitable although the ancient technology didn't scale well.
We could replace all our current petroleum needs using less than 2% of the ocean surface. The vast majority of Earth's sun, water, and "farm land" resources is ocean. Pursuing genetically engineered saltwater algae as the main replacement for petroleum seems completely obvious.
Same as man has very little to do with global warming. We are a factor but a very puny one when it comes to CO2 output. You are making the same mistake. Duplicating natures process to make oil from algae will take trillions upon trillions upon trillions dollars of exotic apparatus, bulldozers, drying ponds etc etc. Man cannot deal with these colossal to the nth degree inputs, these colossal to the nth degree masses the way nature can over millions and millions of years
What you propose is much smaller project than digging up Mt Everest and reassembling it in New Delhi India. Think in terms of mass mass mass multiplied by millions x millions of years plus heat and pressure...This is how nature turns algae into oil
These algae projects are a bonanza for cynical scientists to milk billons in Federale funding from the idiots in Congress whom are mostly liberal arts majors and affirmative action women and blacks without an ounce of common sense science education in them