Study: Huge sugarcane expansion could send CO2 emissions south

Imagine a farming operation that envisions expanding its area under cultivation by the equivalent combined land masses of the American states of Texas and California. That’s more than 1.12 million square kilometres. To put that into perspective, the whole of Queensland measures about 1.8 million square kilometres.

The crop in question is sugarcane, for the production of ethanol, and the country in which such an enormous program is being touted is Brazil. 

In a report this week in the journal Nature Climate Change, researchers say that vastly expanding Brazil’s sugarcane crops for the production of ethanol could reduce current global carbon dioxide emissions by as much as 5.6 per cent. Brazil is already the world’s largest grower of sugarcane, with about 80,000 square kilometres under cultivation.

About half of Brazil’s crop goes into making ethanol, and the country has been an enthusiastic adopter of the biofuel as a replacement for petroleum-based fuels.

Researchers led by Stephen Long, a University of Illinois biologist who worked with a team that included scientists from the University of Sao Paulo, believe the expansion of Brazil’s sugarcane industry can be accomplished without impinging on environmentally sensitive areas while also allowing for the expansion of other agricultural crops.{%recommended 3794%}

Brazil has established a network of protected areas that covers more than two million square kilometres (about 25% of the country) and includes nature preserves, parks and indigenous lands.

“We’ve kept the proposed sugarcane production within the area that can be legally converted,” Long says.

He says the team’s research was based on a new approach to modelling the precise behaviour of sugarcane growing in regions that vary in soil composition, temperature, rainfall and other factors.

Instead of using statistical models to predict future crop production, which don’t take fully into account of the way changes in water, carbon dioxide and temperature interact to affect sugarcane production, the new study used a “mechanistic model” that grows the plant, “so it’s driven by the factors that the plant is responding to on an hourly basis”, Long says.

The carbon-related costs of converting the land to sugarcane fields were included in the analysis.

Study co-author Amanda De Souza notes that the Brazilian ethanol industry extracts sugar to make biofuel, and also burns the leftover cane stalks, called bagasse, to generate electricity and power the mills. 

“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,” she says.

Other reports might temper some of the enthusiasm for sugarcane-based ethanol production, such as this recent study in the journal Energy Research and Social Science that questions the industry’s efforts to portray “ethanol as a ‘green hero’ that helps reduce greenhouses gas emissions and thus saves humanity from climate change”.

Still, Long says: “Our conclusion is that this industry could expand quite a bit and make a significant contribution to decarbonising fuel.”

He adds that the expansion of sugarcane growing “does not have to stop at Brazil. Many acres that once grew sugarcane — from the Caribbean to Hawaii — lie idle today. Sugarcane-to-ethanol production would provide a use for this land again.”

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