TY - JOUR T1 - Manure digesters-a sound solution? JF - Journal of Soil and Water Conservation SP - 78A LP - 79A VL - 62 IS - 4 AU - Joseph Hart Y1 - 2007/07/01 UR - http://www.jswconline.org/content/62/4/78A.abstract N2 - Thirty years ago, most Iowa farmers, about 70%, kept a few hogs on the farm. They didn't think of themselves as hog farmers-it was just one income stream of many on small, diversified family farms. Today, only 12% of Iowa farmers raise hogs-but the total number of hogs in the state has remained relatively constant. Instead of penning a dozen pigs behind the barn, these large-scale operations house thousands, even tens of thousands of animals in massive concrete and steel barns. The rest of the country has experienced the same consolidation, and not only for hogs, but for poultry, dairy, and cattle. These concentrated feedlots take a tremendous toll on the environment. A small farm can easily use a truckload of manure here and there to help crops grow. Confinement operations generate many tons of manure, which is typically stored in pits or lagoons and then sprayed or injected into the soil. These practices can stretch the carrying capacity of soil to the breaking point, resulting in contamination of local watersheds and groundwater reserves. Surface runoff into streams and lakes can cause fish kills on a massive scale. Lagoons and holding pits frequently … ER -