Phytotoxicity and genotoxicity of agro-industrial digested sludge hydrochar: The role of heavy metals.

Hydrochar is a new carbonaceous product obtained via hydrothermal carbonization of wet biomass, such as sludges or digested sludges, which often have disposal problems, also due to the presence of contaminants such as heavy metals. The properties of the hydrochar led to an interest in using it as an amendment, but the agro-environmental properties must be considered for its safe use. Raw hydrochar produced by agro-industrial digestate and relative three acidic post-treated hydrochars (for heavy metals removal) have been assessed considering their effect on phytotoxicity, soil, plant growth, mutagenicity, and genotoxicity.

Evaluating the potential of hydrochar as a soil amendment.

In this study, hydrochar (HC), a carbon-rich product originated from hydrothermal conversion treatment (HTC), was obtained from wastes of the wine and dairy industries. The effect of mixing secondary char and compost was tested, before and after the aerobic mixing of compost (COM) and HC at increasing doses (from 15 to 75 Mg ha DM), in an effort to lower the HC phytotoxicity due to potential phytotoxic compounds of secondary char. The results indicated that, after the aerobic stabilization, the mix HC/COM was able to double the plant growth in comparison to COM alone.

Matured Manure and Compost from the Organic Fraction of Solid Waste Digestate Application in Intensive Apple Orchards.

In intensive fruit growing systems, the recovery and maintenance of soil fertility play a crucial role in both environmental protection and sustainable support to plant productivity. The circular economy approach adopted at the EU level strongly promotes the use of organic products instead of mineral fertilizers. This work focuses on two different soil improvers, compost from the organic fraction of municipal solid waste digestate (CO) and "matured" manure, produced after a fast and controlled aerobic treatment in an aerated pile (MM), which were applied in three apple orchards with different soil tillage.

Hydrochar and hydrochar co-compost from OFMSW digestate for soil application: 2. agro-environmental properties.

The work concerns the study of the hydrochar from digestate and hydrochar co-compost characterization as amendments. The processes for hydrochar and co-compost production were described in Part 1 of this work (Scrinzi et al., 2022).

Hydrochar and hydrochar co-compost from OFMSW digestate for soil application: 1. production and chemical characterization.

The best available technique (BAT) for managing the organic fraction of municipal solid waste (OFMSW) is represented by anaerobic digestion (AD) and subsequent composting. This research explored a new industrial model in the framework of the C2Land international project, with the insertion of hydrothermal carbonization (HTC) as a post-treatment for OFMSW digestate. The reaction was set for 3 h at three different temperatures (180 ÷ 220 °C); the wet solid hydrochar obtained after filtration was then co-composted with greenery waste as a bulking agent and untreated OFMSW digestate in four different proportions in bench-scale bioreactors.

Effects of woody biochar on dry thermophilic anaerobic digestion of organic fraction of municipal solid waste.

This study presents the results of semi-pilot scale anaerobic digestion tests conducted under dry thermophilic conditions with the addition of biochar (6% on fresh mass basis of inoculum), derived from an industrial gasification plant, for determining biogas and biomethane production from organic fraction of municipal solid waste. By using two types of inocula (from a full-scale dry anaerobic digestion plant and from lab-scale biomethanation tests), the obtained experimental results did not show significant increase in methane yield related to the presence of biochar (330.40 NL CH kgVS using plant inoculum; 335.