Biogas production from sugarcane waste has large potential for energy generation, however, to enable the optimization of the anaerobic digestion (AD) process each substrate characteristic should be carefully evaluated. In this study, the kinetic challenges for biogas production from different types of sugarcane waste were assessed. Samples of vinasse, filter cake, bagasse, and straw were analyzed in terms of total and volatile solids, chemical oxygen demand, macronutrients, trace elements, and nutritional value. Biochemical methane potential assays were performed to evaluate the energy potential of the substrates according to different types of sugarcane plants. Methane yields varied considerably (5–181 Nm3·tonFM−1), mainly due to the different substrate characteristics and sugar and/or ethanol production processes. Therefore, for the optimization of AD on a large-scale, continuous stirred-tank reactor with long hydraulic retention times (>35 days) should be used for biogas production from bagasse and straw, coupled with pre-treatment process to enhance the degradation of the fibrous carbohydrates. Biomass immobilization systems are recommended in case vinasse is used as substrate, due to its low solid content, while filter cake could complement the biogas production from vinasse during the sugarcane offseason, providing a higher utilization of the biogas system during the entire year.

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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.

The anaerobic digestion of filter cake and its co-digestion with bagasse, and the effect of gradual increase of the organic loading rate (OLR) from start-up to overload were investigated. Understanding the influence of environmental and technical parameters on the development of particular methanogenic pathway in the biogas process was an important aim for the prediction and prevention of process failure. The rapid accumulation of volatile organic acids at high OLR of 3.0 to 4.0 gvs·L−1·day−1 indicated strong process inhibition. Methanogenic community dynamics of the reactors was monitored by stable isotope composition of biogas and molecular biological analysis. A potential shift toward the aceticlastic methanogenesis was observed along with the OLR increase under stable reactor operating conditions. Reactor overloading and process failure were indicated by the tendency to return to a predominance of hydrogenotrophic methanogenesis with rising abundances of the orders Methanobacteriales and Methanomicrobiales and drop of the genus Methanosarcina abundance.

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