Assessment of the Variations in Characteristics and Methane Potential of Major Waste Products from the Brazilian Bioethanol Industry along an Operating Season

Anaerobic digestion appears to be a favorable option to optimize the energetic exploitation and reduce the environmental impacts of bioethanol waste products. Some analytical characteristics of these waste products are available in various sources. However, these data are too incomplete and unsystematic to be compared among the bioethanol industries. Design of biogas processes based on such data has to deal with considerable unknowns regarding the technical feasibility and operating costs. Therefore, to better understand and assess the applicability of these bioethanol waste products in anaerobic digestion, the micro- and macro-element concentrations, the physicochemical parameters, and the methane potential were analyzed. In addition to the assessment of seasonal variations, the effect of alkaline and mechanical treatments was also investigated for lignocellulosic bagasse samples. Possible deficiencies of the trace elements Ni, Co, Mo, Se, and W in vinasse as a substrate for anaerobic digestion were recorded. The correlation between the gradual increase in methane yields of vinasse and filter cake along the bioethanol operating season and the dynamic changes in the substrate characteristics was shown. Moreover, the methane yield of raw bagasse increased by 50% after applying both treatments in combination.