As researcher, designer and MIT professor Caitlin Mueller once said, “The greatest value you can give to a material is to give it a load-bearing role in a structure.” Load-bearing components – foundations, beams, columns, walls, etc. – are designed to resist permanent or variable forces and movements. Similar to the bones of a human body, these support, protect and hold everything together. To fulfill that indispensable function, they must be made from materials with outstanding mechanical properties, which explains the prominence of cement and steel in structures. However, their high performance comes at a high cost: together, they account for 15% of global CO2 emissions. This makes us wonder, is it possible for structural materials to be truly sustainable? We know solutions like greener versions of concrete already exist, but there are many other alternatives to explore. And sometimes, the answer is closer than we expect; in the earth beneath us and the nature that surrounds us.