A research project is evaluating the environmental impact of sugar-alcohol production in São Paulo

A group of scientists from UNESP wants to investigate why aerosol and ozone particle concentrations in São Paulo did not decrease after the state prohibited burnings; the subjected was highlighted at FAPESP Week France.

By Maria Fernanda Ziegler, from Lyon  |  Agência FAPESP – The burnings that were carried out in the past during sugarcane harvest to eliminate dry leaves have altered for years the air quality in the central region of the State of São Paulo, Brazil. The particles launched into the atmosphere during the process were visible to the region’s inhabitants and were deposited in the streets and on cars.

Atmospheric pollution also caused respiratory problems among the population, impacts on biodiversity and the native vegetation, and contaminated rivers.

Technological advances and pressure from society led to the end of this practice, made official via a state law in 2002. Little by little, sugarcane burning was substituted by more modern techniques, such as the use of mechanical harvesters.

“In 2018, mechanized harvesting was used in 90% of the production. It was hoped, above all, that there would be an improvement in air quality. However, official statistics indicate that aerosol and ozone particle concentrations remain at the same levels as before,” said Arnaldo Alves Cardoso, a researcher at the Institute of Chemistry of the São Paulo State University (UNESP) in Araraquara, in a lecture given at FAPESP Week France.

New practices

Cardoso has been analyzing the consequences of the atmospheric pollution in the sugarcane region of São Paulo since the end of the 1990s. In studies performed in the decades of 1990 and 2000, his team has collected air samples in the city of Araraquara, in the interior of São Paulo, and measured the changes in the composition of the atmosphere between the harvest and inter-harvest period.

“During this period, characterized by less-than-intense mechanization, we have seen, for example, that among the particulate matter there were sugarcane macronutrients. When this material falls on sugarcane plantations, great. However, when it falls on a natural forest, it can modify the soil and cause a loss of biodiversity,” he said.

A change of scenario took place at the turn of the decade. Besides the State Law of 2002, an agreement signed between the sugar-alcohol industry and the State of São Paulo government established the elimination of burning by 2017. According to the researcher, in the 2016/2017 harvest, the production harvested manually was 43.6 million tons, or 10% of the total harvest.

Cardoso highlighted that mechanization in harvests entailed an important change, the use of leaves and other sugarcane parts with less energy value, which were burned before, have been used as raw material for producing electrical energy and second generation (2G) ethanol, which is indicated as a way of increasing bioenergy generation without extending the area under cultivation.

“These facts suggest that the sources of emissions have possibly changed in quality, but not in quantity. It seems that we have merely changed activity, but the pollution remains the same. But there are still many questions that I intend to answer with more studies,” he said.

Brazil is the biggest sugarcane producer in the world. The main producing region is located in the State of São Paulo, which has the highest population density in Brazil and an economy based primarily on agroindustry.

“The State of São Paulo covers 55% of the area planted with sugarcane in Brazil. In the 2017/2018 harvest, 13 billion liters of ethanol were produced, which corresponded to 47% of the Brazilian production,” he said.

The FAPESP Week France symposium took place between November 21st and 27th, thanks to a partnership between FAPESP and the Universities of Lyon and Paris, both in France. Read other news about the event at www.fapesp.br/week2019/france/.