Evaluation of the properties of biochar obtained from rice husk for its application in agricultural soils

The increasing world population boosted the demand for basic needs such as energy, water, and food. In turn, agricultural production has increased, generating a large amount of agro-industrial waste every year. Globally, Brazil is the seventh-largest rice producer, and the State of Rio Grande do Sul is responsible for 70% of the rice production in Brazil. Rice husks are composed of organic compounds (cellulose, hemicellulose, lignin, and extractives) and inorganic elements that include potassium, calcium, magnesium, and sulfur. These inorganic elements are essential nutrients in the soil. Since natural degradation is slow due to the aromaticity of lignin, rice husk (RH) waste accumulates and poses an environmental threat, causing air and water pollution. In this context, in order to return the biochar to the soil, the properties of rice husk and rice husk biochar were evaluated. Parameters such as pH, true density, bulk density, porosity, identification of the composition and concentration of the elements, analysis of the functional groups, total carbon (TC), and cation exchange capacity (CEC) were performed on RH biochar samples. These samples were produced in a laboratory-scale pyrolysis rig, under a con-trolled atmosphere of Nitrogen (N), using three peak temperatures (350 °C, 450 °C, and 550 °C) and three soak times (30, 60, and 120 min).Based on the results obtained in the characterization analyses of the biochar, as well as the yield values found, it is concluded that the best pyrolysis temperature for the production of biochar from rice husks, for application in soils, is 550 °C.