Next Challenge: Build a Compost Loo

Watch Video: A compost loo? Are you joking??!! >

It was now time for the group's next major building project - a composting toilet! Rob explains that these are more environmentally friendly than ordinary loos which use large quantities of drinkable water to flush. In fact, if everyone in the world flushed their toilet with drinking quality water there wouldn't be enough clean water to drink!

Composting loos don't use water - each time you go to the loo you mix your waste with straw and pour the result into a composter. Then, hey presto, a few months down the line you'll have perfectly usable compost.

Aaron reacts with horror: 'I found it difficult enough to pooh in the portaloo. And now I have to pooh and compost my own waste!' Sasha is totally disgusted at the thought of a composting toilet that they have to empty themselves. In contrast, Jermaine proudly announces that he can crap anywhere!

Lawrence seizes his chance

Nineteen-year-old Lawrence, the youngest group member, seized his chance and took the lead. With military precision, he divided the group into three teams. The first was responsible for building the toilet (which Lawrence had nicknamed The Shitter). The second group were responsible for the urinal (The Piss Bucket) and the third the composter.

All three groups got to work. The group responsible for the Shitter started making a structure to house their loo out of old doors and fencing panels. They found an old chair frame, attached an old toilet seat to the top to sit on and put a bucket underneath.

Meanwhile, the Piss Bucket group had found an old bathtub which they would use as their urinal trough. They then filled it with straw to absorb the urine, and knocked up some rickety walls around it to give a degree of privacy. And finally the composting team found an old barrel (which, according to the print on the outside had originally been used to transport a huge amount of chutney). This was to be the vessel for the solid waste to be tipped into and mixed with straw and earth to balance the nitrogen and carbon content. Finally, they fashioned a lid for it from an old bucket to prevent flies and other creatures from getting in and feasting on the contents.

The grand opening

Lawrence opened the new composting loos in his own way: 'May God protect them and all who crap in them!' he said.

Aaron was the first person to christen the new composting loo and he emerged beaming with a freshly steaming bucket which he emptied into the composter to great applause!