I am currently writing my dissertation for my Ph.D. entitled "The Use of Canola Oil as a Carbon Feedstock in the Synthesis of Value-Added Materials". One of the things that happens when writing a dissertation is that you do a lot of reading about interesting points tangential to your actual project. Since I am working with canola oil, I devoted a special section of my introduction to biodiesels, since 80% of the biodiesels used in the EU are made of canola oil. (They call it rapeseed, but it is canola oil.) I thought I would share some of the chemistry of biodiesels.
First, let's start with a little history. Did you know that diesel engines were originally designed to run on a renewable fuel source? In 1900, Rudolph Diesel presented his engine, which was powered by peanut oil, believing that biomass fuel was the future of the engine. However, come the 1920s, engines were altered to use the lower viscosity petrodiesel which was much cheaper to produce. This remains one of the huge challenges in sustainable development: economics. How much are you willing to pay for fuel because while the $1.30/L (Canadian pumps in Alberta) is pretty steep, it is still cheaper than biobased fuels because of the mass production infastructure. But I digress; this is a chemistry blog.
Peanut oil is not technically a biodiesel. Biodiesels are transesterified vegetable oils resulting in fatty acid esters, most commonly the methyl ester. The vegetable oil is reacted with an excess of methanol in the presence of an acid or base catalyst (industrially it is usually the base sodium methoxide) to produce 1 equivalent of glycerol and 3 equivalents of fatty acid methyl esters. These are referred to as FAMEs. What is awesome about biodiesels is that they can be used directly in compression engines without modification to the engine and they can also be blended with petrodiesels because they are completely soluble. Because they come from plants, the carbon dioxide and water produced by the burning of the fuel are taken back up by the plants resulting in overall reduction in emissions. There is also a reduction in carbon monoxide, sulphates, particulate, and total hydrocarbon emissions. Which is all pretty great.
But of course there are some major drawbacks. First, cost. As I have alluded, price plays a big role in industrialisation and biodiesels are currently a lot more expensive to produce compared to petrodiesel. Second, poor cold performance. This is actually a concern with diesels in general. But these longer chain fuels begin to solidify at higher temperatures. Huge problem in a place like Edmonton, Alberta where in the winter it is common to get temperatures well below -10 C. This is also why diesel engine vehicles require a block heater. Fuels need to remain liquid and low in viscosity to actually perform well. Third, and I think this is really important, is that the greenhouse gas (GHG) emission savings is much lower than expected, failing the sustainability requirements. The EU's Renewable Energy Directive (RED) demands a 35% reduction in GHG emissions compared with petrodiesels for biodiesels. They have estimated that canola-based biodiesels result in a "typical" 45% reduction while commonly using the default number of 38% in GHG savings.
However, a recent study by Gernot Pehnelt and Christoph Vietze refutes these claims and points to GHG savings of, at best, 29.7%. The authors claim there was a lack of transparency in the calculations performed by the European Commission. Running a life cycle analysis using the same basic methodology and background data as RED, and only utilising publicly available and published data in their calculations, the authors were unable to replicate the numbers reported by RED. Further, these calculations did not take into account for any of the other environmental or social impacts associated with using available agriculture land for fuel, which they argue would further decrease the sustainability of canola oil biodiesel.
Another huge concern with biodiesels is that glycerol is produced as a by-product. The global production of glycerol has grown exponentially, well passed the global demand for this chemical.
As we move toward a more sustainable future, it is important to recognise that the after over one hundred years of industrialisation based on petroleum fossil fuels, our journey has no quick solutions. It will be a long and complex movement, but with every step, even the smallest, we are that much closer to a sustainable future. This must be a global movement.
References:
Brown, B. A. Ph.D. Dissertation, University of Alberta, Not Yet Published.
Bart, J. C. J.; Palmeri, N.; Cavallaro, S. Biodiesel
science and technology; Woodhead Publishing Ltd.: Boca Raton, FL, 2010.
Huber, G. W.; Iborra, S.; Corma, A. Chemical
reviews 2006, 106, 4044–98.
Cheng, J. Biomass to Renewable Energy
Processes; Taylor and Francis Group: Boca Raton, FL, 2010.
Ragauskas, A. J.; Williams, C. K.; Davison, B. H.; Britovsek, G.; Cairney, J.; Eckert, C. A.; Frederick, W. J.; Hallett, J. P.; Leak, D. J.; Liotta, C. L.; Mielenz, J. R.; Murphy, R.; Templer, R.; Tschaplinski, T. Science (New York, N.Y.) 2006, 311, 484–9.
Spellman, F.; Bieber, R. The Science of
Renewable Energy; CRC Press, Taylor and Francis Group: Boca Raton, FL,
2011.
The Economic Impact of Canadian Grown
Canola and its End Products on the Canadian Economy; 2011.
Knothe, G. Energy & Environmental
Science 2009, 2, 759.
Gilbert, N. Nature 2012.
Pehnelt, G.; Vietze, C. Jena Economic
Research Papers 2012, 39, 1–35.
