Development of alternative solution for animal mortalities through co-composting using natural clinoptilolite in the framework of circular economy

Abstract

Managing large animal mortalities becomes challenging and potentially inappropriate, particularly within a livestock unit, due to the methods employed. These methods are not environmentally friendly, have the potential to spread diseases to both humans and animals, and do not align with the principles of promoting a circular economy within livestock units. Similarly, the management of green waste (GW) originating from gardens, parks, and tree-lined streets is challenging due to its high lignin content and the absence of efficient management plans by local authorities. Therefore, in most of the cases, GWs are discharged unexploited to landfill sites although composting seem to be a promising method. This study aims to develop a composting methodology of animal mortalities as an alternative management option by exploiting GWs from municipalities and by adding natural zeolite to the feedstock materials in order to control the extreme properties of the final product. The ultimate goal is to produce a safe and environment friendly product, appropriate to be applied to agricultural and forest ecosystems in order to enhance soil improvements. The feedstock materials were sheep mortalities, GWs and clinoptilolite. Three types of composts were produced; one with no zeolite addition, one with zeolite addition in the beginning of the composting process and one by adding zeolite after the 2nd heat cycle was completed. It was observed that the three composts were of high nutritional value, complied with most of the EU and US Standards of Compost Quality and that the addition of zeolite improved the nutritional status of the composts (e.g. N, K, Mg, Mn). A significantly reduced Enterobacteriaceae population was observed in zeolite-amended compost compared to the unamended one. The results are directly useful and applicable to promoting healthy plant growth and sustainable agro-silvo-pastoral practices.