HANK MORGAN / SCIENCE PHOTO LIBRARY HANK MORGAN / SCIENCE PHOTO LIBRARY
A technician checking the temperature of an urban waste compost heap. This compost heap at a plant in Minnesota USA is being used to research recycling of disposable nappies. The nappies are added to the normal compost waste, taking about 7 days to degrade. The temperature of the compost heap must remain between 57 and 65 Celsius during that time. At the end of the process, the compost is used as a fertiliser by a forestry growing Christmas trees.
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