Part I: Why do we need an alternative?
When Rudolf Diesel first developed his engine, one of his visions was that it would be able to use a vegetable oil so that farmers would be able to grow their own fuel. One of the early Diesel engines in the Paris exposition was operated on peanut oil and it apparently ran so smoothly that no one noticed. For better or for worse, though, petroleum distillates soon became the universal fuel for automobiles and we now face the dilemma on how to replace it, now that the oil supply seems to be running out.
In Diesel’s time, it was enough for a fuel to merely provide enough energy and impetus to get the engine running. Eventually, it also had to be cheap and widely available. We now demand more from our fuels. We want our fuel must also be non-toxic and biodegradable, lest it damage the environment if it is spilled. It must come from renewable sources. The entire system, from growing the feedstock to the use of products and by-products and waste disposal, must minimize the impact on the environment. This includes not just emissions with a local impact like smoke and carbon monoxide but also emissions that have a global impact like carbon dioxide and nitrogen oxides which worsen the greenhouse effect. Moreover, any alternative must be compatible with engines and distribution systems that have been highly optimized to take petroleum. These are the challenges that face any alternative fuel.
Among proposed alternatives, biodiesel has become an attractive option for the replacement of petroleum diesel (“petrodiesel”). What is biodiesel? The term could really be applied to any diesel fuel that derives from living matter. Present jargon, however, limits the term to vegetable oil that has been reacted with alcohols so as to lower its viscosity and make it more suited to modern Diesel engines. Its immediate viability as an alternative has been enhanced by the already considerable experience in the oleochemicals industry in biodiesel manufacture. While its overall impact on the greenhouse effect is still hotly debated, other desirable qualities of biodiesel are unequivocally accepted. Biodiesel is biodegradable and, in fact, has been tested for the bioremediation of petroleum spills. It has a superior lubricity to petrodiesel. Because of this, its addition allows the overall reduction of sulfur in the fuel to almost nil. The bulk of the feedstock for its production comes from renewable resources. When biodiesel is used in a blend with petrodiesel, no changes are required for existing diesel engines.
The question, of course, is: if biodiesel has so many advantages, why is it not used more widely? The primary reason for this is cost. It was only during the very peaks of the oil spike of 2008 that biodiesel was able to approach the cost of petrodiesel. Of this cost, about 6085 percent comes from the feedstock.
Availability is another issue. The enormous demand for diesel fuel dwarfs the available supply of vegetable oils. The global production of the top 12 vegetable oils in 2006 was about 126 million metric tons. In contrast, the total consumption of diesel fuel by the transportation industry in the same year was about 693 million metric tons. Thus, even if all of the vegetable oils produced in the world in 2006 were converted to biodiesel, this would fill only about 18 percent of the total demand in the same year for the transportation industry alone. It is necessary that feedstock production be increased dramatically. But, as it turns out, if forestland is converted to farmland, the CO2 absorption capacity of the land is reduced greatly and thus any capacity expansion actually leads to a worsening of the greenhouse effect.
With such high hurdles for alternative sources of vegetable oil, it is not surprising that none have reached commercial success and now the biodiesel industry still relies on the food oils like coconut, palm and soy. In the second part of this series, the candidates to replace the food oils will be discussed
NOTE:
The interested reader may consult my more technically oriented paper “Alternative crops for biodiesel feedstock” which was published in 2009 as Article No. 56 in Volume 4 of “CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources.” Citations and additional support for the statements in this article may be found there. A copy may be found online at http://www.cabi.org/cabreviews/default.aspx?LoadModule=Review&ReviewID=115703&site=167&page=1178
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Luis F. Razon is a full professor of chemical engineering at De La Salle University. He obtained his bachelor’s degree in chemical engineering (magna cum laude) from De La Salle University and his MS and Ph.D. in chemical engineering from the University of Notre Dame, Indiana. His papers on the dynamics and stability of chemically reacting systems are some of the best-cited papers in the chemical engineering literature. He served in the food industry for 14 years, launching several important new products for a major international nutritional products company. He returned to the academe in 2001 and is pursuing research in chemical reactor engineering, alternative fuels and life-cycle assessment. E-mail at luis.razon@dlsu.edu.ph.