Evaluation of a new technology for increasing the quality of a compost

Composting is a treatment process that transforms biodegradable organic waste into compost, a product that is rich in essential nutrients (nitrogen, phosphorous and potassium) and can be used as a fertilizer for the cultivation of agricultural land. By decreasing landfill disposal and avoiding incineration, this procedure is advantageous, and it has a good impact on the environment. In the treatment scheme for the production of compost, a critical issue has been identified that needs a solution: during the final refining process, the compost, which has already passed all the maturation stages, is screened at 12 mm with a drum sieve. In this way, the compost ready for the market is obtained. The oversize > 12 mm of this separation is sent via conveyor belt to a star disc screen with an opening of 50 mm. The product > 50 mm is actually made up of plastic films and paper and is disposed of, the product < 50 mm and > 12 mm (surplus) is used as inoculum as it is rich in bacteria useful for starting biodegradation organic, but still contains a significant amount of plastic film, which thanks to the recirculation as inoculum continues to remain in the process. Therefore, in order to improve the characteristics of the overstock, the following actions were decided:  granulometric and product characterization of the surplus  tests with aeraulic separator and characterization of the products obtained. In collaboration with the companies G.A.I.A. S.p.A. and TOSO S.r.l. this study is focused on the design and construction of a machine capable of removing plastics from organic overflow, improving the quality of the final product. To propose the effective plant solution, the degree of impurity in the compost produced was investigated and tests to improve the design and to evaluate the efficiency of the deplasticizer machine were performed. The final machine proposed consists in a mesh conveyor belt, with beater rollers capable of making the mesh "jump". The fine clean material falls through the mesh, and it is separated of the coarse impure material. The results thus obtained were satisfactory with the recovery of more than 10% of the of fine clean compost and very low percentages of unwanted substances.