Algae is rehabilitating its public image. Although we tend to think of it as a water-quality problem—driving away tourists, threatening drinking water supplies, and creating dead zones—different varieties are being put to work for all sorts of beneficial uses. It’s being touted as a sustainable source of protein; proponents claim that algae can produce seven times the amount of protein as soybeans on the same amount of land.
Now architects in Europe are designing living walls incorporating algae to clean the air. These aren’t the attractive, plant-filled walls you might have seen in an upscale hotel or public building. They are actually giant plastic curtains that hang on the outside of buildings; each curtain incorporates a network of tubes filled with algae. Polluted urban air enters through the bottom of the curtain and moves upward, allowing the algae to feed on the carbon dioxide as it goes. Cleaner air is released from the top. The plastic itself is biodegradable, made from plant materials. Such so-called bioplastics can be manufactured from potato starch, corn starch, or even algae.
The London-based designers Claudia Pasquero and Marco Poletto came up with the idea after observing algae growing on ponds near their office.
The algae curtains are decidedly unattractive, and their inventors say they are probably best suited to buildings like warehouses, which are located in urban areas and are not usually designed for appearance. The algae is bioluminescent and glows faintly in the dark.
In a recent demonstration, about a dozen of the curtains were hung on the walls of a building at Dublin Castle, where they removed an estimated two pounds of carbon dioxide from the air each day—about the same amount that would be removed by 20 large trees. And although some critics say trees are by far the preferable option—providing shade, aesthetic, and stormwater benefits in addition to removing carbon dioxide—the curtains do provide some protection from the sun to cool the buildings on which they’re hanging.
The algae curtains are not yet commercially available, but the designers say they would likely cost about $350 a square meter.