British start-up Novacem has developed a "carbon-negative" cement, meaning it absorbs more carbon dioxide over its life cycle than it emits.

Cement is a big ol' polluter - with an annual production of more than 2.5 billion tons, Reuters says, conventional "Portland" cement is responsible for an estimated 5 percent of global CO2
emissions, more than the airline industry.

Yikes. Cement makers are investing in modern kilns and using as little carbon-heavy fuel as possible to alleviate some of their footprint, but the efforts haven't resulted in much of a reduction. Novacem took an extra step and changed the cement formula, using magnesium silicates rather than calcium carbonate, which not only doesn't emit CO2 during manufacturing but actually absorbs CO2 over its lifespan. The process mimics the natural formation of sea corals, using spent CO2 as a raw material.

For every ton of conventional cement replaced by Novacem's "green cement," around three-quarters of a ton of CO2 is saved. The company raised almost $2 million (about 1 million pounds) for a start-up plant in northern England that could be operational by 2011.

Green cement will likely not reach the market for a few years at least, but others are jumping on the bandwagon, Reuters says - Calera of California, Australia's Calix, Carbon Sense Solutions of Canada and British-based Cenin.

*Tip o' the blogging hat to kdawson at Slashdot for the title inspiration and the story.