When it comes to greenhouse gas emissions, the construction industry has a lot to answer for. The construction industry alone is responsible for 38% of global CO2 emissions.
Much of this is to do with concrete, which has an incredibly high carbon footprint. In a bid to bring down the industry's overall emissions, the race is on to find a more sustainable, while equally practical, building material.
Check out this gallery to learn all about the sustainable cities made of mud.