Digestate & fugate - Fertilizers with ecotoxicological risks

Abstract

Increasing number of decentralised biogas plants increases not only the amount of biogas produced, but also the production of digestate. Digestate and fugate are believed to be good fertilizers. However, there is often a tradeoff between other environmental impacts linked to agricultural production like eutrophication or ecotoxicity. Only limited ecotoxicological information is known about the effects of digestate or fugate on terrestrial fauna and flora. This is the first study comparing the survival and reproduction of collembolans as the representative soil fauna and the root growth and photosynthetic activity of Sinapis alba and Panicum miliaceum plants when exposed to digestate and fugate. Comparison of ecotoxicological results with chemical analysis of both digestate and fugate has led to the conclusions that application of digestate and fugate was beneficial neither for tested plants, nor for zooedaphon. Under practically used dosing both digestate and fugate can represent potential ecotoxicological problems, which can affect zooedaphon diversity and reproduction resulting in degradation of soil structure, reduction of microbial activity or water retention capacity of treated soils. That is why we do recommend at least simplified ecotoxicological testing of digestate as presented in this study. Ecotoxicity testing can support decision of direct application on soil, or mixing the digestate with other materials (like compost, manure, pond sediments, or biochar), what will help to utilize nutrients and consequently can prevent degradation of soil fertility.