When my mind wanders, which is fairly often, I sometimes wonder about ways to green-ify the world.  But I must admit I have never given any particular thought to building materials, much less one of the most basic: cement.

But a British company has embarked on a government-sponsored, 1.5 million pound experiment to construct a plant to produce what is supposedly carbon-negative cement.  Carbon-negative, you say?  You read me right.  We’ve all been conditioned, myself included, to think of “carbon-neutral” as the apotheosis of ecological manufacture.  But now we have a new goal — carbon negative!

Standard cement, also known as Portland Cement, uses limestone as its basic element.  As part of the production process, it is heated to 1500 degrees centigrade (which of course uses lots of carbon-producing energy).  Then, once water is added for its use in buildings, it absorbs some carbon as it dries and hardens — but not nearly enough to compensate for the energy used in its manufacture.

The new carbon-hungry cement, which uses magnesium silicates instead of limestone, need only be heated to 650 degrees centigrade — consuming less than half the energy of regular cement.  Then, when drying and hardening, it absorbs more than twice the amount of carbon dioxide.  Making it significantly carbon-negative!  Jackpot!

Many questions remain, of course.  Are there enough raw materials for lots of this new type of cement to be manufactured?  (Advocates say yes.)  Can a new type of cement prove itself just as reliable and strong as the old standby, Portland?  (Hard to say.)  Will this potentially paradigm-shifting product ever see the light of day, unlike so many other good environmental ideas.  (Experience says no, but let’s hope for the best.)

–from the Guardian UK