The issue with trees is you need to adapt the city to them, you can't adapt them to the city. And people have proven once and again that they would invent anything to not move by an inch when our way of life is put in question.
So we push forward with absurd solutions one after the other: carbon capture, atmospheric geo-engineering, a damned nuke in antarctica, and now "liquid trees".
Because the alternative is to change our ways, and we can't face that.
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.