Visitors to the Royal Oak Zoo in Detroit, Michigan, will soon be able to take home a bucket of poo as a souvenir.

Monkey

Monkey

Free buckets of pure animal manure will be handed out to the first 1,000 guests who visit the zoo's anaerobic digester as part of the Green Fest celebration to show how the zoo recycles waste.

The digester converts 500 tons of animal manure and other organic waste each year into methane-rich gas, which in turn helps provide power to the zoo hospital and creates a natural by-product which can be used for compost.

The zoo says: ''[It] is great for putting in your garden.''