Greenhouse gas emissions from sugar cane ethanol: Estimate considering current different production scenarios in Minas Gerais, Brazil

The studies of greenhouse gas (GHG) emissions of sugarcane ethanol production show few scenarios or, in most cases, a single representative scenario of the most common practices for ethanol production. However, the combination of the diverse sugarcane agricultural and industrialization practices lead to a wide variety of production scenarios. Current studies do not show the GHG emissions balance for all these scenarios. This issue is the aim of this study, which presents a GHG emissions balance of ethanol production considering 120 different scenarios related to current sugarcane agricultural and industrial practices in Brazil, with data of Minas Gerais. In order to obtain the ethanol production scenarios, different types of cultivation, fertilization, harvesting and different sugarcane crop cycles were combined. The scenarios were classified by groups, according to their GHG emission levels. The main characteristics of each group were analyzed in order to identify the factors that influence the performance of GHG emissions. The results show GHG emission levels ranging from 2489.38 kg CO2eq∙ha−1∙yr−1 to 3289.95 kg CO2eq∙ha−1∙yr−1, depending on the regime of agricultural practices present in each scenario. The factors that most favor the increase of GHG emission levels are: short sugarcane crop cycle combined with fertigation with stillage. These two factors were present in production scenarios that presented the highest levels of GHG emissions in this study. The factors that most favor the decrease of GHG emissions are: long sugarcane crop cycle, fertilization without stillage on ratoon and mechanical harvesting without sugarcane burning. All these factors were present in scenarios that presented the lowest GHG emissions. On the other hand, in certain agricultural conditions, the mechanical harvesting of green cane showed to be as polluting as manual harvesting of burnt cane. The differences between the types of cultivation showed no significant influence on the final balance of GHG emissions.