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Agricultural waste is rapidly increasing as the agricultural sector expands, presenting significant environmental challenges if not managed properly. While incineration is a common method for agricultural waste treatment, the high moisture content, low heating value, and high ash content hinder its usage in furnaces. Additionally, although agricultural waste is widely utilized as solid fertilizer, its slow decomposition rate also poses challenges. Hydrothermal treatment emerges as a solution to overcome these challenges, enhancing the characteristics of biomass as solid fuel while also producing nutrient-rich liquid fertilizer.
This study aims to demonstrate the results of hydrothermal treatment on rice husk, empty fruit bunch (EFB), and vetiver waste. Hydrothermal process was conducted within a temperature range of 150–225 °C and holding time of 30–90 min in a 2.5 L batch reactor. Solid products were evaluated for their fuel characteristics such as moisture content, density, high heating value (HHV), proximate, and ultimate analysis, while liquid products were analyzed for macronutrient content.
Results indicated that hydrothermal treatment of rice husk led to reduced inherent moisture content, increased fixed carbon, lowered nitrogen content, and higher HHV of the solid product as the operating temperature increased. Hydrothermal treatment also led to reduction of ash and potassium content in EFB. In the case of vetiver waste, hydrothermal was effective in increasing the density. Liquid products from all waste types were suitable for liquid fertilizer due to their similarity in macronutrient to commercial products.
This study underscores the similar improvement of product characteristics for all agricultural waste inputs. We suggest conducting hydrothermal treatment at temperatures above 175 °C with 30 min holding time to optimize process efficiency and product quality. Overall, the study highlights the potential of hydrothermal treatment for enhancing the utilization of agricultural waste for sustainable agricultural productivity.
Keywords: Agricultural biomass, Empty fruit bunch, Rice husk, Vetiver waste, Hydrothermal treatment, Solid fuel, Liquid fertilizer
