Blending of Biodiesels with Petroleum Diesel to Reduce Soot Production

Author:Nicole Wongk, nwongk@usc.edu

Co-Authors:

Dr. Daniel Lacks, djl15@case.edu

Dr. Mohan Sankaran, mohan@case.edu

Dr. Clever Ketlogetswe,  ketloget@mopipi.ub.bw

Mr. Jerekias Gandure, gandurej@mopipi.ub.bw

Laone Morebodi, mogbasto@gmail.com

Possible topic categories:

3. Sustainability

8. Fuels, Petrochemicals, and Energy

Blending of Biodiesels with Petroleum Diesel to Reduce Soot Production

In an effort to reduce emissions and the use of non-renewable resources without sacrificing the high calorific value of petroleum diesel, an optimal blend of biodiesel with petroleum diesel is sought.  The project compares four biodiesels produced from plants native to Southern Africa, specifically Botswana, the site of the project. From the following plant sources a biodiesel is produced: Scelerocarya Birrea, Tylosema Esculentum, Schinziophyton, and Jatropha.

Scelerocarya Birrea, also known as Morula, is found in Southern Africa and is a resilient food source when other staple crop yields fail (Mojeremane, W., 2004). Tylosema Esculentum is native to the Kalahari Desert which receives approximately 250 mm of rain each year but may experience drought or excessive rainfall from year to year. The edible seeds of Tylosema Esculentum, from which the biodiesel is produced, are found within the oblong fruit which is initially green and turns brown as it matures (Powell, 1987).

Schinziophyton is also a tree native to the deep sands of the Kalahari Desert. Naturally, Schinziophyton requires 15-25 year before fruit can be harvested, however with use of irrigation, this time may be shortened to four years (Graz, F.P., 2002). Jatropha also grows in the Kalahari Desert and produces fruit after only 2-3 years. Of the four plant sources, Jatropha is the only one that is not a food source and thus removes the food versus fuel controversy. (Kgongwana, S., 2009; "Center for Jatropha," 2013).

 Each biodiesel is individually blended with petroleum diesel in ten percent increments.  A sample of each blend was combusted in a bomb calorimeter and the mass of the crucible and sample were taken both before and after combustion. Taking the mass prior to combustion supplied the mass of the biodiesel blend sample. While taking the mass after combustion supplied the mass of soot produced. The mass of the soot produced per sample was then taken as a percentage of the biodiesel sample mass, thus allowing for a comparison to be made. The calorific values of pure standard petroleum and pure biodiesel were averaged, for each type of biodiesel. Of the blends with a calorific value above this calculated average, the blend producing the lowest soot was taken as the optimal blend for that particular biodiesel.

For Birrea, the optimal blend was B60 with a calorific value of 43.91 MJ/Kg and a proportion of soot of 0.18%. For Schinziophyton, the optimal blend was B50 with a calorific value of 44.34 MJ/Kg and a mass proportion of soot of 0.46%. For Tylosema, the optimal blend was B50 with a calorific value of 44.63 MJ/Kg and a mass proportion of soot of 0.42%. For Jatropha, the optimal blend was B40 with a calorific value of 44.99 MJ/Kg and a mass proportion of soot of 0.70%.

Of the four optimal blends the highest calorific value was Tylosema B50 and the lowest mass proportion of soot produced was Birrea B60. Blends of biodiesel and petroleum diesel are a unique solution for two major environmental problems, reducing use of non-renewable resources and reducing emissions. To use biodiesel blends in cars today, only a few modifications to a current diesel engine are necessary. A possibility for further research includes genetically engineering plant species to increase the energy content delivered without changing the reduced emissions.

Acknowledgements

We would like to thank the following for their assistance in the completion of the research; the National Science Foundation, Case Western Reserve University, the University of Botswana, and the lab technicians.

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