nanoengineering concrete
Cement has been used in construction since the Roman Empire, and according to an MIT report we now manufacture 2.35 billion tons of cement per year. One of the concerns with its widespread use is the huge amounts of energy used in its manufacture.
MIT researchers have found that cement's strength lies in the way its nanostructure is packed, and think it may be possible to find - or nanoengineer - a different mineral to use in cement paste, one that has the same packing density but does not require the high temperatures during production, conceivably cutting world carbon dioxide emissions by up to 10 percent. That would accomplish one-fifth of the Kyoto Protocol goal of a 5.2 percent reduction in total carbon dioxide emissions.