Space agencies from around the world hope to colonize the moon one day. But building a moon base is expensive work: Bringing just one pound of payload from Earth into orbit costs an estimated $10,000.
This high cost of transport means that researchers are seeking alternative building material to construct a lunar settlement, including raw materials found on the moon or ones generated by the astronauts themselves, like their pee, for instance.
Researchers have devised a way to use urea, an organic compound found in human urine, to create better “lunar concrete,” the European Space Agency announced statement. The team, led by scientists from the Faculty of Engineering at Østfold University College and the European Space Agency (ESA), recently published their findings in the Journal of Cleaner Production.
“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.
“Since urea is the second most abundant component in urine (after water), it is readily available anywhere there are humans,” the authors wrote in the study.
To simulate environmental conditions on the moon, scientists subjected the lunar concrete mixture to vacuum and freeze-thaw cycles. Temperatures on the moon can range from -414 to 253 degrees Fahrenheit, according to NASA.
Future moon-dwellers wouldn’t be the first to use their pee for practical purposes. Urea is a common ingredient in industrial fertilizer as well as "a raw material by chemical and medical companies" here on Earth, the AP reports. Historically, urine has been used to whiten teeth, soften leather, make gunpowder and power electricity, Mohi Kumar reported for Smithsonian magazine in 2013.
“The hope is that astronaut urine could be essentially used as it is on a future lunar base, with minor adjustments to the water content. This is very practical, and avoids the need to further complicate the sophisticated water recycling systems in space,” study co-author Marlies Arnhof said in the ESA statement. “The science community is particularly impressed by the high strength of this new recipe compared to other materials, but also attracted by the fact that we could use what’s already on the Moon.”