Physics KS3 / GCSE: How to recycle urine in space

Kevin Fong asks for a volunteer from the audience who would be happy to drink a sample of his urine.

He is surprised when some children volunteer and explains that urine is a waste product from the body which contains chemicals which in large quantities are harmful to us.

He then demonstrates a urine recycling system based on osmosis.

A concentrated syrup is placed on one side of a semi-permeable membrane and urine is placed on the other side.

Over time, osmosis draws water from the urine into the syrup, which can then be drunk by an astronaut.

Kevin drinks the liquid that results, and concludes that while the output from the urine-recycling bag is safe to drink, it still smells like urine and still tastes a bit like urine!

This clip is from the Royal Institution Christmas Lectures 2015.

Teacher Notes

Key Stage 3

You could ask students where urine comes from and what it contains.

Ask them to suggest why it would be harmful to drink urine.

Then watch the clip and ask them to discuss their thoughts afterwards.

Key Stage 4

Before watching the clip, you could ask students to discuss the principles and applications of osmosis in pairs.

After watching the clip, you could ask them whether they would drink the product from the bag and if they can suggest some explanations for Kevin’s observation that the product still smelled and tasted like urine (e.g. there might have been a leak in the membrane).

Curriculum Notes

This clip will be relevant for teaching Physics.

This topic appears at KS3 and in OCR, Edexcel, AQA, WJEC KS4/GCSE in England and Wales, CCEA GCSE in Northern Ireland and SQA National 4/5 in Scotland.

More from the Royal Institution Christmas Lectures 2015

What is Newton's Canon and Third Law?
Using Earth’s rotation to launch a rocket
How the vacuum of space effects the human body
Resonant Frequency
Orbital Rendezvous
What does gas weigh?
Why are bones weaker in orbit?
How micro-gravity disorientates us
The danger of orbital debris
Demonstrating heat shield material
Why Earth rock is found on the Moon
Demonstrating radiation detectors
How Earth protects us from radiation
Why tardigrades can survive in orbit