One of the biggest hurdles to building the structures necessary for a moon base is the cost of sending the materials. It would be much better to use materials already at hand. The moon has plenty of rock and dust, and it might be possible to convert them into building materials using human urine.
“Thanks to future lunar inhabitants, the 1.5 liters (3.2 pints) of liquid waste a person generates each day could become a promising by-product for space exploration,” the ESA says in a statement.
Urea, the most abundant component in human urine after water, can break down hydrogen bonds and reduce the viscosities of fluid mixtures, per the Associated Press. Researchers mixed water, urea and lunar regolith—a powdery soil found on the moon’s surface—together and 3-D printed geopolymer cylinders of the mixture, Jake Parks reports for Astronomy. When urea was used in the mixture, the results were malleable and easy to shape.
Maybe that's what all those children's stories mean when they tell us the answers were always inside ourselves. Read about the lunar building material of the future at Smithsonian.