A European design firm has come up with a novel answer to highway pollution, running tubes of photosynthetic algae alongside the highway to absorb CO2 pollution from the traffic. First unveiled at a garden competition in Geneva, Switzerland, the demonstration model rapidly sucked up emissions from the highway, and the creators claim it can be easily scaled up. The algae can then be used for a variety of purposes such as oil or even food, and, like all photosynthetic organisms, to make oxygen as a byproduct.

Until recently, carbon capture efforts have focused exclusively on pulling carbon out of the air at the point of production and then socking it away. In a 2007 article in Environmental Health Perspectives, Charles Schmitt describes the field of CO2 capture as it currently stands. Carbon Capture and Storage (CCS), as it is known, is practiced only at a handful of demonstration projects and all of them aim to permanently remove the carbon from the air. The idea is to capture emissions from an oil or gas well as the fuel is extracted—not from the burning of the oil or gas—and re-inject it into a nearby rock formation. If successful, the carbon should stay in the rock for at least 10,000 years.

Of course, nobody will be monitoring for 10,000 years, and it is unclear exactly what will happen to underground CO2 over such long stretches. No leakage has been detected yet, but it’s only been a handful of years. Schmidt notes that CO2 can also combine with brackish (briny) water, which is common in the preferred rock types for CCS, and form carbonic acid, just as in ocean acidification. The acid can erode the nearby rock or potentially work its way into water supplies. Both possibilities are problematic.

Even if CCS works perfectly, by its nature the technology is linked with producing more fossil fuels to burn. At best, CCS can slow the rate of emissions growth, which is really not good enough. What makes the Swiss algae farm so appealing is that it makes almost whimsical use of existing infrastructure. It also sets a more modest goal of repurposing of the CO2, rather than trying to take it completely out of circulation. There’s no reason to limit this kind of idea to just highways, either. Why not snake some algae tubes up and over skyscrapers, or maybe along curbs? Green highway? Let’s have a green city.