Hydrochars Derived from Spent Coffee Grounds as Zn Bio-Chelates for Agronomic Biofortification

Leslie Lara-Ramos (), Ana Cervera-Mata, Jesús Fernández-Bayo, Miguel Navarro-Alarcón, Gabriel Delgado and Alejandro Fernández-Arteaga
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Leslie Lara-Ramos: Department of Chemical Engineering, University of Granada, 18071 Granada, Spain
Ana Cervera-Mata: Department of Soil Science and Agricultural Chemistry, University of Granada, 18071 Granada, Spain
Jesús Fernández-Bayo: Department of Soil Science and Agricultural Chemistry, University of Granada, 18071 Granada, Spain
Miguel Navarro-Alarcón: Department of Nutrition and Bromatology, University of Granada, 18071 Granada, Spain
Gabriel Delgado: Department of Soil Science and Agricultural Chemistry, University of Granada, 18071 Granada, Spain
Alejandro Fernández-Arteaga: Department of Chemical Engineering, University of Granada, 18071 Granada, Spain

Sustainability, 2023, vol. 15, issue 13, 1-13

Abstract: Previous studies have attributed both phytotoxicity and the capacity to mobilize nutrient elements to the presence of polyphenols and melanoidins in spent coffee grounds (SCG) and SCG-hydrochars obtained through hydrothermal carbonization (HTC). This work aimed to evaluate SCG and two SCG-hydrochars obtained at 160 and 200 °C that were functionalized with Zn salts (bio-chelates), to achieve the in vitro biofortification of lettuce. Two application modes were established: (1) a fixed Zn concentration of 10 mg kg −1 of soil and (2) a fixed dose of 0.5% bio-product. Soil alone (control A) and commercial chelates (control B) were used as controls. Outcomes showed that SCG-hydrochars retain the capacity to mobilize Zn compared to SCG. However, the chelating capacity was reduced (Zn: 94%) and the toxicity was significantly increased ( p < 0.05) with higher temperatures of HTC (200 °C). Both fresh and dry lettuce weights were less affected at doses of 0.5% of bio-product and registered a maximum increase of 136% of Zn in the plant content. The present study approaches the possibility of using these by-products as bioinorganic fertilizers at subtoxic doses, although more research is needed.

Keywords: hydrothermal carbonization; micronutrients; bio-chelates; hidden hunger; agricultural soil; spent coffee grounds; biofortification (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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