Pelletization of composted swine manure solid fraction with different organic co-formulates: effect of pellet physical properties on rotating spreader distribution patterns

Introduction In Europe, because of the high productionlevels of livestock farming in general and pig farming inparticular, animal waste management has becomeincreasingly important to comply with the required loweringof livestock farming environmental pressure. Usuallymanures undergo solid/liquid separation, which generatesone clarified liquid fraction and one nutrient-rich solidfraction suitable for in farm composting (both raw and inmixture with other bulking agents). This can be used toproduce soil amendments, whose management can befurther improved by pelletization that, againsttechnological and environmental advantages, has the disadvantageof requiring a quite high energy input.Results Four different pelleted organic fertilizer formulationsmade of swine manure solid fraction (SMSF)composted both by itself and with sawdust (SMSF-SD),wood chips (SMSF-WC) and wheat straw were tested tohighlight differences in physico-chemical and land distributionfeatures. They were compared with two pelletedorganic fertilizers ordinarily available at retailers. Resultsshow that, as far as physical and chemical features areconcerned, the greatest difference from the reference productsused in this study is found in pellet size distributionafter spreading since the disintegrating action of therotating vanes does not affect the tested formulation withthe same intensity as the commercial products. Distributiontests showed that SMSF-SD was the formulation withbetter longitudinal and transverse distribution, while SMSFwas the one showing good transverse but poor longitudinaldistribution.Conclusions In farm pelletizing of SMSF compostedwith different organic waste materials as co-formulatescan turn into organic fertilizer formulations comparablewith pelleted organic fertilizers ordinarily available atretailers. SMSF-WC was the formulation with the bestresistance to fragmentation induced by spreader vanes.SMSF-SD was the formulation showing better longitudinaland transverse distribution, while SMSF showed goodtransverse but poor longitudinal distribution. Thesepromising results enhance the importance of co-compostingas a way to increase livestock farming sustainabilityand produce better manure compost for wider agriculturaluses.