Formation of Dioxins during Energy Cogeneration by Burning Bagasse and Sugarcane Straw Fertilized with Chlorinated Compounds: State of the Art and Presentation of Alternatives

Abstract— Polychlorinated dibenzodioxins (PCDDs), also known as dioxins, are part of a group of organochlorine chemical compounds, highly persistent in the environment, with similar chemical structures. High levels of this compound are found in the burning ashes of the sugarcane and are attributed to the high concentration of chlorine present in bagasse and in the sugarcane straw that are used as a substrate for obtaining energy in the bioethanol production plants. This occurred due to the application of chlorine-containing fertilizers, such as potassium chloride, during the cultivation of sugarcane. Considering the high degree of toxicity of dioxins, the objective of this study was to conduct a literature review on the subject and research alternatives that can control the generation and emission of dioxins in bioethanol production plants, either through the application of appropriate technologies to control emission of dioxins generated during burning, or by substituting the chlorinated fertilizer used in the cultivation of sugarcane. From the analysis of different studies that researched the presence of dioxins in the ash of the bagasse burning boiler, there is a concentration that varies from 2, 2 to 190 picograms of dioxin equivalent toxicity (TEQ) per gram of ash. For the removal of these dioxins, the control systems commonly used in sugarcane plants have not proved to be efficient. In this context, the main alternatives would be the application of technologies for optimizing the combustion process combined with the treatment of end of pipe by means of a scrubber and bag filter or selective catalytic oxidation using NH3-SCR catalysts. Another option is the substitution of the potassium source, which presents itself as the most viable alternative, with the use of non-chlorine sources, such as Glauconitic Siltstone, Potassium Nitrate, Potassium Sulfate or vinasse instead of using chlorinated fertilizers such as Potassium Chloride.