Using algae to clean up vehicle emissions

Algae will consume CO2 within this built structure, or in a puddle by the side of the road, if both are well illuminated. So I don't see the point of building the structure.

You have to build something to filter out the algae. Then separate their lipids (to make biodiesel or whatever), from their nitrogen and phosphorus. Put the latter back in the puddle (or structure) to grow more algae.

The other product is mostly cell walls (I suppose) after drying, those can be burned directly. You get heat from this, and it reduces the net CO2 trapping. But I can't think of anything else to do with algae cell walls.

The best plants (algae or something bigger) to use for CO2 trapping would seem to be those with the lowest CO2 compensation points. Essentially this means the ones that can assimilate it at the lowest concentration. Don't know that this has been researched, but some grasses do a variation on photosynthesis that has a very low compensation point. Called C4 but also has more sciency sounding names.

I had another thread in mind concerning high CO2 concentrations in cities. Still thinking about that, but algae farming might fit in there.

 

They could plant some trees? They look nice, give off oxygen and offer shade. Give it a few years and algae and moss will be growing all over the pavement below too

 

My first question, is much higher is the CO2 concentration over a freeway or other road? Is it high enough to increase the algae growth rate than compared to a an algae reactor away from the road?

Now a couple of points. Gas solubility in water is the opposite of solids. The warmer the water, the more salt, sugar, or whatever you can dissolve in it, but the less gasses that the water can hold. Those tubes look like they can get quite warm while in the sun. Tropical aquariums with heavy plantings of higher plants need CO2 fertilization to maintain plant growth.

Then the CO2 algae scrubbers for power plants bubble the exhaust directly through the water. From the few details we got here, this just seems a gimmick, and not any better than a stand alone bioreactor for algae cultivation. Though it is a novel use of otherwise unused space if the cost isn't greater than a stand alone reactor. Both will need other nutrients added, which I think is the hurdle for algae biodiesel. Specific lighting requirements could be an issue when just relying on the sun. It's easy to grow algae. It's harder to grow a specific algae, and make money from doing so.