Slurry — a mixture of animal faeces, urine and water — and silage liquor, a by-product of the process by which cut grass is compressed and fermented into silage, are polluting water sources.
In the United States, North Carolina's hog population has grown faster than any state in the nation, swelling from 2.6 million to 10 million hogs since 1987. These animals produce 19 million tons of feces and urine a year, or over 50,000 tons every single day. The hogs are concentrated in the eastern coastal plain, an economically important and ecologically sensitive network of wetlands, rivers, and coastline. In June 1998 the State authorities introduced tough new legislation on hog farms to control the dangers caused by the waste products.