The conventional production of bioethanol takes place through sugar cane processing. Given that Brazil generates abundant lignocellulosic residues, other bioethanol production routes from residual biomasses have been increasingly considered. In this context, this study aimed to assess the sustainability of two second-generation bioethanol (E2G) production routes, one from sugarcane bagasse and the other from coconut husks. To this end, nine indicators proposed by the GBEP (Global Bioenergy Partnership) methodology, namely GHG emissions, non-GHG emissions, water use and efficiency, income changes, bioenergy sector jobs, incidence of occupational injuries, illnesses and deaths, productivity, net energy balance and increased gross value from bioenergy production, were applied. Following the two bioethanol production route assessments through indicator application, a conclusive graphic outlook was constructed to identify the most sustainable route. The sugarcane bagasse production route derives from the Iogen technology and is employed at Raízen's Costa Pinto Plant, which produces this biofuel on an industrial scale, while the coconut husk production route is currently being improved on a bench scale. The indicator analysis demonstrates that, despite the coconut husk route exhibiting greater social sustainability, with better employee remuneration and less frequent injuries, illnesses and occupational deaths, the sugarcane bagasse route shows greater environmental and economic sustainability, due to lower GHG emissions and water extraction, besides higher productivity, and higher net production income. Therefore, the comparative analysis produced by applying the GBEP methodology demonstrates that the sugarcane bagasse route is the most sustainable regarding the production of second-generation bioethanol.

Considering the importance of the search for sustainability and the growing emphasis given to biofuels, promoted as a promising alternative energy, this study highlights the relevance of research that evaluates sustainability in the bioenergy sector, specifically bioethanol. The present work aims to analyze methodologies aimed at assessing the sustainability of bioethanol using a literature review and, based on this analysis, indicate the most suitable methodology. The most popular methodologies used to assess the sustainability of bioethanol were identified from the bibliographic survey and screened according to pre-established criteria of exclusion, based on keywords, and inclusion, regarding the pillars and biofuel addressed. First, it was found that the studies were conducted in different regional contexts and used different methodologies, which could provide both quantitative and qualitative results. After screening and selection, the evaluation methodologies adopted by each author were analyzed. This analysis made it possible to recognize the factors influencing the choice of methodology, where the suitability of a methodology to the particularities of each case was of great importance. Finally, considering the pre-defined criteria for assessing the sustainability of bioethanol, this paper recommends the GBEP (Global Bioenergy Partnership) methodology as the most appropriate, especially since it was created specifically for the bioenergetic sector and has an accessible application protocol. Lastly, it was also noted that few publications evaluate the sustainability of bioethanol considering its entire three dimensions (social, environmental, and economic), emphasizing the importance of developing more studies with this approach.