Growing up in Dehli, Anirudh Sharma often found his clothes looked grimy after a day's wear. It wasn't dirt soiling his shirts, it was pollution—a dark soot that clung to the fabric like a coat of paint. Years later, visiting India on break from his studies at the MIT Media Lab, Sharma realized just how apt the comparison was. That soot is not so different from carbon black, the pigment used to make black ink. “I wondered, can we use pollution as a source of pigmentation?” he says.

When he returned to MIT, Sharma built a gadget that could capture soot from a candle. He combined the particulates with oil and rubbing alcohol to create a thick ink. He put it through an HP C6602 inkjet cartridge and found that it both looked and worked much like the conventional stuff. It just wasn't terribly efficient. “I wanted to give it the size and scale to solve much harder problems,” he says. Given a large enough operation, Sharma figured, his sooty ink might offer a pollution-fighting alternative to traditional black inks.

Graviky Labs

And so Sharma co-founded Graviky Labs, which is now raising money on Kickstarter for its Air Ink markers and inks. He and Nikhil Kaushik redesigned his soot trap to fit over the exhaust pipes of major emitters like cars and diesel generators. He calls it a Kaalink (a play on the Hindi word for black), and says each one can collect up to 95 percent of the pollutants emitted from a tailpipe, including lung-punishing particulates between 2.5 and 10 micrometers in diameter. One Kaalink can collect enough carbon to produce one fluid ounce of ink, enough to fill a pen, in about 45 minutes.

The Kaalink works by imparting a positive electrostatic charge on particulates exiting an exhaust pipe, which are then drawn to a negatively charged chamber. A bypass system allows air and water vapor to pass through, so there’s no back pressure or impact on engine performance. After a couple of weeks’ worth of driving, a red light alerts motorists that their Kaalink filter is saturated, at which point Graviky transfers the particulates into containers called carbon banks. Sharma and Kaushik remain tight-lipped about what happens next, but say chemists strip their the material of heavy metals and dust, leaving a carbon-rich soot (they follow industry standards to dispose of the excess pollutants). The soot is then ground into an ultrafine powder and combined with solvents and oils to produce five grades of ink for a variety of applications, from screen printing to oil painting.

It’s an intricate process, but Sharma says it’s still far more sustainable than producing typical black carbon ink, which relies on the burning of fossil fuels to produce. And unlike many Kickstarter projects, Kaalink already works; Sharma and Kaushik are raising funds primarily to refine the device and help scale up production.

Sharma and Kaushik acknowledge that Air Ink won’t rid the world of air pollution. So far they've installed 75 of them, and captured about 220 pounds of particulate matter. That’s enough to make a little more than 250 gallons of ink. Eventually, after more testing and certification, Graviky plans to distribute Kaalinks to bus and taxi fleets so they can maximize the amount of carbon being captured. (The plan is for these fleets to empty their own Kaalinks into carbon banks that Graviky will pick up and process.) “Even if just 15 percent of the world’s black ink supply is replaced with Air Ink, we could end up sequestering a lot of air pollution,” Sharma says. It’s a worthy goal—the more ink on the page, the less pollution in your lungs.