09 Oct 2014

Ensuring sustainable cellulosic bioethanol production

Using a detailed process analysis, we helped Novozymes A/S identify ways to reduce water consumption during cellulosic bioethanol production.

As the world's energy demands grow, cellulosic ethanol is increasingly seen as an important source of renewable energy. The production method behind cellulosic ethanol, however, can be water intensive. To address these concerns, Novozymes A/S asked us to conduct a study to establish reliable, evidence-based data on how much water cellulosic ethanol production consumes compared to conventional gasoline production.  

First, we analysed: 
  • direct water (fresh surface and groundwater) consumption during the fuel production process 
  • direct water consumption allocated to produce raw material, such as crude oil for gasoline production and biomass for the cellulosic ethanol production 
  • indirect water saving allocated to the exported surplus electricity through saved public electricity production 
Next, we used a detailed process analysis to examine the amount of water consumed during cellulosic ethanol production, using two data sources: 
  • a detailed process simulation study on corn stover (the leaves and stalks of corn) conversion conducted by the National Renewable Energy Laboratory (NREL) in the United States 
  • a commercial cellulosic bioethanol production during the implementation stage at Chemtex Italia S.R.I. (now Biochemtex), a large scale bioethanol production facility in Crescentino, Italy 
We then compared near- and long-term water consumption estimates for cellulosic ethanol production with currently accepted figures of water consumption in gasoline production. We found that water consumption during cellulosic ethanol production is comparable to, and in some cases lower than, conventional gasoline production in the long term. 

Our analysis also showed that the ethanol conversion process itself is not a significant water consumer. Instead, utility operations are the most water intensive processes, with cooling tower evaporation responsible for 90-95% of water use.