Yeah, can plant a tree? Plant a tree. If you can't, the alternative right now is nothing. This introduces another option.

Trees provide shades that cool down the cities. These algae don't. The main benefit of these "liquid trees" is to reduce pollution. You know what reduces even more pollution? Electrification and public transportation. Combine both. You'll need much less space for motor vehicles lane inside the city and no need for "depolluting" inventions. Add some bike lanes and you'll still have plenty of space for trees. They're better looking and will do the cooling job.

So, as I was saying: praising a less efficient solution that may bring new unexpected issues down the road because the efficient solution requires people to change.