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

Daniela Bona; Donato Scrinzi; Giustino Tonon; Maurizio Ventura; Tiziana Nardin; Fabio Zottele; Daniele Andreis; Gianni Andreottola; Luca Fiori; Silvia Silvestri

doi:10.1016/j.jenvman.2022.114894

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

J Environ Manage. 2022 Jun 15:312:114894. doi: 10.1016/j.jenvman.2022.114894. Epub 2022 Mar 22.

Authors

Affiliations

¹ Technology Transfer Centre, Fondazione Edmund Mach, Via E. Mach, 1, 38010, San Michele a/A, Italy.
² Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento, Italy.
³ Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università, 5, 39100, Bozen-Bolzano, Italy.
⁴ Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento, Italy; Center Agriculture Food Environment (C3A), University of Trento, Trento, Italy. Electronic address: luca.fiori@unitn.it.

PMID: 35334400
DOI: 10.1016/j.jenvman.2022.114894

Abstract

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). The amendment properties of hydrochar (produced at 180-200-220 °C for 3 h) and co-composts (25%, 50%, and 75% hydrochar percentage of digestate substitution) were assessed by phytotoxicity, plant growth bioassay, and soil effect. Different seeds species (Lepidium sativum, Cucumis sativus, and Sorghum bicolor sp.) were dosed at increased concentrations using both wet raw amendments and their water extracts. The chemical characterization showed phytotoxic compounds content depending on both the initial feedstock (digestate) and the HTC process; at the same time, the analysis highlighted the reduction of these compounds by composting (organic acid, polyphenols, salt concentration). The dose-response was analyzed by the Cedergreen-Streibig-Ritz model and the half-maximal effective concentration (EC50) was calculated based on this equation. The soil properties and GHG emissions measurements (CH₄, CO₂, N₂O, and NH₃) highlighted the effect on N dynamics and on soil respiration induced by substrates. The HC200 soil application determined a significant impact on CO₂ and N₂O emission and NH₃ volatilization (10.82 mol CO₂/m²; 51.45 mmol N₂O/m²; 112 mol NH₃/m²) and a significant reduction of total N and TOC (46% of TKN and 49% of TOC). The co-compost (75%) showed specific effects after soil application compared to other samples an increase of available P (48%), a greater content of nitrogen (1626 mg/kg dry basis), and a reduction of organic carbon (17%). Our results demonstrate the good quality of co-compost and at the same time the validity of this post-treatment for addressing many issues related to hydrochar use in the soil as an amendment, confirming the suitability of HTC process integration for digestate treatment in anaerobic digestion plants.

Keywords: Co-compost; GHG emissions; Hydrochar; Phytotoxicity; Plant growth bioassay; Soil effect.

MeSH terms

Carbon
Carbon Dioxide / analysis
Composting*
Nitrogen / analysis
Soil / chemistry

Substances

Soil
Carbon Dioxide
Carbon
Nitrogen