Emissão de gases de efeito estufa na obtenção do etanol de cana-de-açúcar: uma avaliação considerando diferentes cenários tecnológicos em Minas Gerais

Abstract

This paper presents a greenhouse gas emissions (GHG) assessment of the agricultural and industrial processes of sugar cane ethanol production in Minas Gerais. The assessment was performed by considering different technological scenarios related to the agricultural and industrial processes. The GHG balance takes into account CO2, CH4 and N2O direct emissions and indirect emissions caused by upstream production processes as agrochemical manufacturing. The preliminary data were obtained by environmental licensing processesdocuments of eleven mills located in the state of Minas Gerais, including both ethanol and sugar cane/ethanol mills. The emissions were estimated by multiplying the input data with specific emission factors obtained by Ecoinvent database and Life Cycle Assessment principles were considered in the emissions quantification. In order to characterize the different technological scenarios for ethanol production, a field resarch was performed at four mills located in Minas Gerais. Input data for all agricultural and industrial processes has been collected directly at the mills. In total, 180 different scenarios were characterized by combining all possible subprocesses. These scenarios were classified by an analysis of variance according to the level of their total GHG emissions. The results demonstrate that the GHG emissions linked to the ethanol production depend on the respective technological scenario. Furthermore, they show that there are significant differences between the level of emissions of different scenario groups. The level of GHG emissins ranges from 1729,24 kg CO2eq ha-1·a-1 to 3257,5 kg CO2eq/ha-1·a-1. The major GHG sources are: sugar cane burning,mechanical harvesting, vinasse application, one half year sugar cane plantation, and filter cake fertilization. The average GHG emissions was 2600,5 kg CO2eq/ ha-1·a-1.