Hydrochars production from digestates maize grown in a contaminated land

Hydrochars production from digestates of mono and co-digestion of manure from vedows system and maize grown in a contaminated land

Figure 1 – Hydrothermal process exposed through a) preparation of samples b) raw hydrochars c) vacuum separation d) final hydrochars

The hydrothermal process (HTC) is currently being applied in digestates derived from mono digestion and co-digestion of manure (vedows system - https://nutriman.net/farmer-platform/product/id_322) and maize grown in a contaminated land containing zinc and traces of copper and chromium elements. The HTC process occurs at 180-220 °C , hydraulic retention time of 2 and 4 hours, and pressures from 2 to 10 MPa, determined according to previous studies in literature. The resulting in hydrochars have the potential to be used as bio-based fertilisers, as they might have a reduced HMs bioavailability and improved fuel properties compared to the untreated manure and digestates.

The HTC process will also be applied to the initial feedstocks to compare the heavy metals distribution before and after the anaerobic digestion process. The production of hydrochars will be followed by the analyses of their chemical parameters, their HM bioavalability (BCR extraction) and their effect in plant/soil. The heavy metals concentrations have been already determined in feedstocks and digestates, in which copper concentrations exceeded the threshold value according to the Fertiliser Regulation 1009/2019 in mono / co digestates.

By Hellen Luisa de Castro e Silva