The swine industry has undergone substantial structural change over the past 20 years, resulting in more integration of production. There has also been a trend towards production on fewer and larger operations, such that more than half of the total pork produced today is by operations with more than 10,000 pigs. In 2006, there were 62 million pigs on farms, 65% of which were in Iowa, North Carolina, Minnesota, Illinois, and Indiana.
Over 9 million tons (dry matter) of swine manure are generated annually. Most is used as fertilizer for crops and pasture, but could also be used to produce bioenergy and bioproducts. Over 4,200 swine farms (half in North Carolina and Iowa) have been identified as good candidates for biogas collection and bioenergy production.