Then there's the research into using calcite precipitating bacteria (Sporosarcina pasteurii -formerly Bacillus pasteurii-,and others) to stabilize sand and to create building blocks, a process similar those which created many of our sandstone mountain chains.
Among the projects I am familiar with is the one to create building blocks or bricks from sand, urea, and some other nutrients, research done by Ginger Krieg Dosier in Abu Dhabi.
See:
http://vergelabs.com/ and click on the photo of the sandy looking brick.
One neat set of experiments with biocemented bricks is to send them up in balloons to very high altitudes to test how they'd react if they were manufactured on the Martian surface:
http://2011.igem.org/Team:Brown-Stanford/REGObricks/Balloon
A slightly more practical line of research for now is to try to solidify sandy subsoils so that the ground underneath buildings ( nuclear reactors, especially...) doesn't liquify during an earthquake.
While these processes cut down on the amount of CO2 produced to make bricks or similar building materials, there is also an increase in off-gassing of ammonia...a much worse greenhouse gas. :-( However, I think there's a solution to that problem. Use a urea-dolomite fertilizer for the Nitrogen source: the dolomite contains magnesium, which helps prevent the ammonia production. ( Note: I don't have the equipment or full set of skills to test this hypothesis...)
At any rate, it is utterly awe-inspiring to think whole mountain chains have been built grain by grain by tiny MICPs critters. (MICP=Microbially Induced Calcite Precipitation)