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This work presents the first comprehensive assessment of ethanol dissolved in rainwater of Sao Paulo State's sugar cane belt, considering the period from 2012 to 2017. Ethanol concentrations ranged from 0.25 to 20.9 μmol L−1, with a volume-weighted mean (VWM) of 4.67 ± 0.13 μmol L−1 (n = 410). Despite the increasing use of ethanol fuel in Brazil, during the study period, the ethanol concentration in rainwater showed an average decrease of 0.54 μmol L−1 per year, attributed to technological improvements in vehicular fuel combustion and catalysts. Anthropogenic emissions appeared to overwhelm possible seasonal fluctuations of ethanol in rainwater due to biogenic sources or meteorological conditions such as temperature, solar radiation, rainfall amount, rainfall rate, and air mass origin. Higher VWM concentrations were generally observed in dry months, when the production of ethanol in the distilleries was highest and biomass burning increased. Consideration of ethanol oxidation in aqueous media by OH radicals indicated that secondary formation of highly toxic aldehydes is likely to increase with greater use of this biofuel. Dissolution of gaseous ethanol during cloud formation appeared to be a more important mechanism of atmospheric removal of this alcohol, compared to below-cloud processes. The wet flux of ethanol was ca. 3 kg ha−1 year−1 and there were evidences that atmospheric replenishment of this species was fast. Brazil has used ethanol fuel on a large scale since the 1980s, so better understanding of the behavior of this species in the lower troposphere of the study region can provide valuable information to assist in predicting future worldwide impacts of increasing use of this biofuel.

Currently, many scientists worldwide are studying the recycling or reuse of waste materials to make useful products. For example, silicate-based wastes have been studied for use as raw material in the ceramic industry. Although numerous types of waste have been studied, sugarcane bagasse ash (SCBA) has been overlooked, probably because this type of residue is more common in developing countries that produce sugar and alcohol from sugarcane. Bagasse is a by-product of the cane sugar industry. Brazil is the world’s largest producer of alcohol and sugar from sugarcane and has an extensive alternative program for automobile fuel. The new technology of flex-fuel (alcohol/gasoline) vehicles, developed in the 1990s and applied to new cars in 2003 revived the Brazilian PROALCOOL program. Today, several million flex-fuel cars are in use, and more than 85% of the new cars produced in the country run on this system (ProAlcool 2011; History of ethanol fuel in Brazil 2011; Goldemberg 2008). In the production of sugar and alcohol, sugarcane is ground and the resulting juice is extracted to obtain sugar or used in a fermentation process to produce alcohol. The fibrous matter that remains after sugarcane has been crushed to extract the juice is called bagasse (or “bagaco,” in Portuguese). There are many applications and much research effort is directed at exploring the potential of bagasse as a renewable power generation source, for the production of bio-based materials (for example, bioethanol and briquettes or pellets), cattle feed, building materials, etc. Basically, bagasse is a fibrous material containing cellulose (~50%), hemicellulose and lignin as the major (~95%) compounds. There are also waxes, inorganic materials and/or salts inside the plant tissues that will result in the final ash (oxides and carbonates) after firing (Pandey et al. 2000). Although there is a great deal of research in Brazil on sugarcane bagasse briquetting, showing the many advantages of using briquettes instead of bagasse, factories still burn bagasse. Currently, sugarcane bagasse is used as a primary fuel source in sugar mills. It is burned in a boiler to produce steam which is utilized in the factory’s processes and also to power turbines for the production of electrical energy. Today, the cogeneration of electricity by sugar and alcohol mills accounts for ca. 5% of the total electricity produced in Brazil