IAN GOWLAND / SCIENCE PHOTO LIBRARY IAN GOWLAND / SCIENCE PHOTO LIBRARY
Human waste fertiliser. Pile of treated sewage sludge in a field. Sewage sludge is a by-product of sewage treatment. If treated it can be used as an agricultural fertilser for food and non-food crops. Although treatment should destroy almost all of the pathogens present in the sludge, there is still some controversy over its use as a fertiliser.
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