Remember that algae are in the plant Kingdom and like I said, if plants could absorb the unbelievably huge amounts of CO2 we put into the atmosphere, they'd already be doing it. The land and oceans are covered with plants (including algae). The reason we have this problem in the first place is that even an entire planet covered in CO2 scavangers can't absorb it all.

Also, CO2 has limited solubility in water so bubbling it through ponds, septic tanks, etc. is also not practical. It's not that it doesn't work in theory, but that the sheer tonnage of CO2 is overwhelming.

I think the only realistic solution is to centralize new-technology fossil-fuel power plants and sequester the CO2 underground.

Let's face it. The only thing that's going to save us is nuclear fusion. Nuclear Fusion is the perfect solution. It's clean and virtually limitless. I still think we ought to put everything we've got into nuclear fusion.

The Europeans are putting a lot of resources into it. Whoever resolves the technical problems will own the world and return the middle eastern oil nations to their lives as nomadic goat herders.