Content of heavy metals in the digestate from poultry by-products

Abstract

Content of heavy and other metals, which have the sanitary status of «harmful substances» in various national and European standards and quality guidelines, in the by-products of poultry farming and its processing products — digestate from a biogas station — was determined. Expediency of analyzing the chemical composition of organic raw materials at different stages of the technological process for obtaining high-quality organic fertilizer based on digestate from biogas station is substantiated. Granulation of the solid fraction of the digestate was carried out to obtain granulated organic fertilizer, which made it possible to improve the process of processing byproducts of animal origin. The granulated dry product mass makes 23.1% of the mass of the native digestate from the biogas station. Laboratory analysis of granulated digestate determined compliance with sanitary standards for organic fertilizers approved for use in conventional and organic agriculture. The content of heavy metals in digestate from quail droppings was analyzed in accordance with DSTU 4944:2008. The mass fraction of heavy metals cadmium, lead and cobalt is 285, 342 and 1795 times lower than permissible concentration for agrochemicals in Ukraine, and copper and zinc are 17 and 19 times lower, respectively. According to international standards (Regulation (EU) 2019/1009), actual concentration of cadmium, lead, copper and zinc is 14, 205, 13 and 4 times lower than the maximum permissible levels. Actual content in percent of the permissible value of the toxicological indicators of the organic mixture, which according to DSTU 7527:2014 can be used as a fertilizer in agriculture and forestry and in green construction; for land reclamation and as fuel is: iron — 4.7%, cadmium — 0.5%, cobalt — 0.4%, manganese — 6.9%, copper — 3.1%, lead — 0.2%.