About 200 dairy farms in Sweden use recycled manure solids (RMS) as bedding material and the number is increasing. Advantages is low price, reliable availability and good cow comfort. The main disadvantage is the risk of increased bacterial growth on the lying area affecting especially udder health and milk quality. The aim of the project is to develop the use of RMS and create guidelines. The project will analyze the effect of using RMS on milk quality and animal health using data from 40 dairy farms and Swedish experiences from RMS by depth interviews on the farms. Bacteriological analysis of RMS from the farms will determine hygienic quality. Furthermore, controlled investigations on the effect of RMS and different treatments (after digestion in biogas plant, hygienized, added with acids or lime) on hygienic quality and ammonia emission will be done. In addition, methane gas potential of the manure, environmental and economical considerations at farm level will be evaluated.