This study explored the potential of HTC for transforming olive pomace into a solid biofuel, while also addressing the need to manage the environmental risks associated with process waters. HTC tests were carried out at three temperatures (180°C, 200°C, and 220°C) and two reaction times (1 hour and instantaneous, 0 hours) to produce hydrochar and process water. The hydrochars were extensively characterized to assess their physicochemical properties, focusing on their potential for combustion applications through calorific value analysis, thermogravimetric analysis and elemental composition. Additionally, germination tests using cress seeds (Lepidium sativum L.) were performed to evaluate the potential of hydrochar as a soil amendment. The process waters generated during HTC were analyzed for their toxicity using three bioindicators: cress seed germination, Daphnia magna mobility, and the activity of nitrifying bacteria. These tests provided insights into the environmental impact of the liquid effluents and their suitability for reuse or safe disposal. Results showed that both temperature and reaction time significantly affected the yield and properties of the hydrochar. Higher temperatures led to a more carbon-rich hydrochar with enhanced calorific properties, making it more suitable for energy recovery. The germination tests demonstrated that hydrochars produced at lower temperatures were more favorable for plant growth. Low concentrations of hydrochar result in longer seedlings and higher germination rates. In contrast, process water toxicity varied with temperature, showing higher inhibitory effects on bioindicators at elevated temperatures. At low concentrations, these waters can be biologically treated and show potential as an agricultural resource, thanks to their effectiveness as a soil amendment. Proper dilutions can enhance plant germination and growth, with significantly better results than standard irrigation water.
Hydrothermal Carbonization of Olive Pomace: Exploring Hydrochar Applications and Environmental Toxicity of Process Waters
Farru G
;Ghaslani M;Milia S;Cappai G
2025-01-01
Abstract
This study explored the potential of HTC for transforming olive pomace into a solid biofuel, while also addressing the need to manage the environmental risks associated with process waters. HTC tests were carried out at three temperatures (180°C, 200°C, and 220°C) and two reaction times (1 hour and instantaneous, 0 hours) to produce hydrochar and process water. The hydrochars were extensively characterized to assess their physicochemical properties, focusing on their potential for combustion applications through calorific value analysis, thermogravimetric analysis and elemental composition. Additionally, germination tests using cress seeds (Lepidium sativum L.) were performed to evaluate the potential of hydrochar as a soil amendment. The process waters generated during HTC were analyzed for their toxicity using three bioindicators: cress seed germination, Daphnia magna mobility, and the activity of nitrifying bacteria. These tests provided insights into the environmental impact of the liquid effluents and their suitability for reuse or safe disposal. Results showed that both temperature and reaction time significantly affected the yield and properties of the hydrochar. Higher temperatures led to a more carbon-rich hydrochar with enhanced calorific properties, making it more suitable for energy recovery. The germination tests demonstrated that hydrochars produced at lower temperatures were more favorable for plant growth. Low concentrations of hydrochar result in longer seedlings and higher germination rates. In contrast, process water toxicity varied with temperature, showing higher inhibitory effects on bioindicators at elevated temperatures. At low concentrations, these waters can be biologically treated and show potential as an agricultural resource, thanks to their effectiveness as a soil amendment. Proper dilutions can enhance plant germination and growth, with significantly better results than standard irrigation water.
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