Diversifying the portfolio of sugarcane biorefineries: Anaerobic digestion as the core process for enhanced resource recovery

Abstract

The continuous search to combine clean energy supply with the efficient exploitation of bioenergy sources is one of the most recurring efforts to meet global energy demands on an environmentally friendly basis. Sugarcane biorefineries play a central role in this context by providing sugar, ethanol and bioelectricity. However, the high energy required in ethanol production limits resource recovery efficiency in conventional sugarcane processing, motivating the investigation of approaches that maximize energetic gains. This study proposes the application of anaerobic digestion (AD) as the core processing step in sugarcane biorefineries, providing performance data for the biomethanation of juice, molasses and vinasses from different sources, namely, first generation (1G; annexed and autonomous) and second generation (2G) ethanol production. A detailed scenarization-based assessment was also carried out, comparing the proposed AD-based schemes with conventional production chains. Relatively similar performances were obtained in the experimental step, irrespective of the compositional differences of the substrates. However, the energetic potential of juice- and molasses-based methane production was at least 2-fold higher than the ones of all types of vinasses (282.81–627.84 vs. 57.10–131.52 MJ TC−1). Scenario comparison indicated the production of biogas and sugar as the most efficient energetic exploitation (94.4%) of sugars from sugarcane. Finally, the energy returned on energy invested ratio estimated for biogas-derived electricity exceeded that of ethanol production by 400%. Thus, AD-based biorefineries have great potential to meet the energy efficiency criteria of sustainable development goals in the coming decades.