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One small step from the bathroom: How astronaut waste could create lunar concrete


Researchers from the European Space Agency have proposed that astronaut biowaste could be used to form concrete on the moon.

With space agencies across the globe setting their sights on the future builds of lunar bases, research from the European Space Agency (ESA) has found human urine could be part of a cost-effective alternative to making concrete on the moon.

Rather than transporting concrete 384,400 kilometres to Earth’s nearest neighbour, there is the potential to source all ingredients for a similar aggregate on the lunar surface known as the “lunar geopolymer mixture” which is primarily made up of the moon’s soil (aka lunar regolith).

Preventing the need to transfer large amounts of aggregates to the moon has huge cost benefits, with just 0.45 kilograms of materials costing $USD10,000 ($AUD15,000) to be launched into orbit.

“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,” Marlies Arnhof, co-author of the study from ESA’s Advanced Concepts Team, told scitechdaily.com.

The main organic compound in urine (urea) has been found to make a more malleable blend of the lunar concrete. Urea acts as a plasticiser for the lunar geopolymer mixture, with the ESA finding it produced a much better aggregate than other common plasticisers such as naphthalene or polycarboxylate. With the use of urea, the 3D-printed geopolymer mixture could retain its shape while under 10 times its own weight.

The study explained that urea has the ability to help break hydrogen bonds which reduces viscosities of fluid mixtures, along with its calcium minerals helping the curing process. Humans produce an average of 1.5 litres of liquid waste per day.

“Urea is cheap and readily available, but also helps making strong construction material for a moon base,” Arnhof said. “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.”

Urea is commonly used as an industrial fertiliser or a raw material for chemical and medical companies back on Earth.

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