October 31, 2017
Could sugar help us be greener?
Could increasing the production of sugarcane ethanol help to cut global carbon emissions?
The 2015 Paris Climate Agreement saw almost every country promise to try and limit global temperature rise to 2 degrees C above pre-industrial levels. Emission reduction poses a significant challenge, so perhaps replacing fossil fuel use with biofuels, which are renewable and emit less net carbon, may be part of the solution. In a paper published this week, scientists have projected that sugarcane ethanol, a biofuel, produced in Brazil alone could offset net emissions by more than 5%. Katie Haylor spoke to author Steve Long, crop sciences and plant biology professor at the Universities of Illinois in the US, and Lancaster in the UK.
Steve - Sugarcane is almost the most productive crop in the world; it produces a large amount of material. Typically, a field of sugarcane will produce up to about 100 tonnes of cane stem per hectare, and about 25% of that stem is sugar. So that is then cut, transported to a mill, and the sugar juice is extracted. That can then be fermented to ethanol; the ethanol distilled and almost all cars in Brazil are flex fuel. That means they can burn ethanol or gasoline and so that allows the Brazilian consumer to use ethanol in their car, usually more cheaply than gasoline.
Katie - This is already taking place in Brazil. Tell us about your prediction - what's novel about this study?
Steve - The core of it was a new model of sugarcane growth. The model actually uses the physiology of the plant: how it responds to rising temperature, rising carbon dioxide, changing soil moisture. We first tested this under present and past conditions and then used it to project forward to work out what productivity we could get in different areas of Brazil in the future. And we overlaid that on knowledge of soil, existing land usage and so what the potential was to expand the crop.
Katie - Tell us about your findings; can you summarise them for us?
Steve - Our finding was that, particularly if we look at land which is underutilised at present, for example, a low intensity pasture, there is considerable opportunity to expand sugarcane production in Brazil, in fact, more than the area of Texas. This would allow Brazil to, if we look at use of fuels in 2014, to displace about over 5% of current emissions by the period of 2040/2050 despite climate change, despite other pressures on land use.
Katie - That’s a very impressive number over 5%, but would this development have other consequences, for example, on people or animals, the environment, the protected environments in those particular areas?
Steve - Not really. This is land that has already been converted for sugarcane use.
Katie - So we’re not talking about the rainforest or protected areas here, are we?
Steve - No. In our particular study we limited this to land which the Brazilian government has mapped out for legal conversion. So we are not talking about the Amazon, the Pantanal, areas of rainforest that have been mapped out for protection.
Katie - Can you summarise the likely significance of this if it were to be adopted in other countries other than just Brazil?
Steve - Sugarcane actually globally has been in decline because demand for cane sugar has been reducing. For example, we see Hawaii and Puerto Rico in the United States, most of the land that was once used for sugarcane production lies idle today. Much of the Caribbean we see the same story and other countries in the north of South America that land is idle. So, if they were to adopt the technology that Brazil has already developed, we could actually displace considerably more than that 5%. We could then be talking about 10% of emissions. Clearly we need many other technologies to reach the targets of the Paris Agreement, but 10% would be a large chunk.