Using solar energy to dry sewage sludge considerably reduces the volume of material that needs to be recycled or disposed of. Depending on how dry the material is at the end of the process, it is possible to reduce its initial volume by up to 70%. A further advantage of using this method to treat residual materials: this drying process increases the calorific value of the sewage sludge to approximately that of brown coal making it a valuable source of energy. Compared to conventional drying technologies, which are often run on fossil fuels, the solar sewage sludge drying process uses the power of the sun and so helps conserve natural resources and cuts carbon emissions.