The role of treatment in the management of structural surplus of livestock manure

Abstract

Poultry and pig farms produce livestock manure in excess of the crops nutrients requirements because most of the food is not produced by the farm but is bought outside. To restore the link between farm arable crops and livestock manure is therefore the great challenge to take up. Expansion of agriculture has led to livestock manure surplus in some areas (especially in Brittany) where this problem becomes regional. These regions are consequently qualified as "structural surplus areas" ("zone d'excédent structurel"). Processing of pig slurry is necessary in these regions as well as changes in feeding strategies, exportation of raw manure and optimization of land spreading. Currently, development of cattle production does not only deal with nitrate pollution but also can lead to more severe environmental damages. Ammonia emissions bring about air pollution and cannot be under control at the present time. A lower soil fertility can occur in case of increasing concentrations of heavy metals (copper and zinc). Also an excess of phosphorus can bring about water surface eutrophisation. All these phenomena are not well known but must be kept in mind as soon as a treatment plant is planned.