Paul Harrison wrote to inform us of an Australian process which uses aluminum and waste products such as fly ash, used glass, slag, and even waste paper to create an inorganic geopolymer analog to concrete, one that takes less energy to make than conventional cement-based concrete. A company called Siloxo developed and has commercialized the process. The resulting material is extremely heat-resistant (up to 950°C), resists most acids, and is supposedly ideal for encapsulating heavy metals, organic wastes, and other hazardous materials.

A greener replacement for concrete may not be the sexiest bit of future-friendly technology to pop up, but it certainly could be one of the more important. Tens of millions of tons of concrete are produced every year around the world. If that production could be made more energy-efficient (and make use of materials which would otherwise be considered hazardous waste), we all win. Or, as Paul put it in his email, "if we're building another world, this looks like the stuff to make it out of."