The team looked at three scenarios that would increase the sugarcane footprint in Brazil between 37.5 million and 116 million hectares (144,788 to 447,879 square miles).

We show that Brazilian sugarcane ethanol can provide the equivalent of 3.63–12.77 Mb d⁻¹ of crude oil by 2045 under projected climate change while protecting forests under conservation and accounting for future land demand for food and animal feed production. The corresponding range of CO₂ offsets is 0.55–2.0 Gigatons yr⁻¹. This would displace 3.8–13.7% of crude oil consumption and 1.5–5.6% of net CO₂ emission globally relative to data for 2014.

—Jaiswal et al.

The research relied on a new approach to modeling the precise behavior of sugarcane crops growing in regions that vary in soil composition, temperature, rainfall and numerous other parameters, said Stephen P. Long, a University of Illinois professor of crop sciences and plant biology who led the analysis with colleagues including included scientists from the University of São Paulo in Brazil.

Most models used to predict future crop production are statistical models that really don’t take full account of the way changes in water, carbon dioxide and temperature interact to affect sugarcane production. We’ve used a mechanistic model here that grows the plant, so it’s driven by the factors that the plant is responding to on an hourly basis.

—Stephen Long

The Brazilian government has mapped out ecologically sensitive lands that cannot be used for agriculture, industry or other types of development, Long said. The proposed expansion of sugarcane production is within the area that can be legally converted.

Brazil already has accomplished a lot with its sugarcane-to-ethanol industry, said study co-author Amanda De Souza, a postdoctoral researcher at Illinois and the University of São Paulo.

Unlike in the US, Brazil uses almost all of the sugarcane plant for energy, extracting the sugar to make ethanol but also burning the stem residue, known as bagasse, to power the mill, with the excess being used to generate and sell electricity. The conversion of the cellulose component of the bagasse to ethanol is also likely to become cost-effective in Brazil. Sugarcane-based ethanol production in Brazil today is much more efficient than corn ethanol, and generates only 14%of the carbon dioxide emissions of petroleum.

—Amanda De Souza

To reduce its carbon footprint even further, the government of Sao Paulo, the major ethanol-producing state in Brazil, recently outlawed the burning of sugarcane before harvest. A practice still common in the US sugarcane industry, burning removes the leaves and reduces the bulk of material that must be hauled to the mill, but adds particulate pollution to the atmosphere and reduces soil organic matter, the researchers said.

Resources

• Deepak Jaiswal, Amanda P. De Souza, Søren Larsen, David S. LeBauer, Fernando E. Miguez, Gerd Sparovek, Germán Bollero, Marcos S. Buckeridge & Stephen P. Long (2017) “Brazilian sugarcane ethanol as an expandable green alternative to crude oil use” Nature Climate Change doi: 10.1038/nclimate3410