Wednesday, March 17, 2010


Man's perennial quest for new sources of energy is driven by the direct relationship that exists between development and efficient and cheap energy. To day practically every aspect of modern life depends heavily on energy. Dependence of non-renewable fossil fuels like coal and petroleum which have been cheap to source pushed mankind further into this "energy trap" and the prospects of these fuel supply dwindling at a fast pace have forced the world to look for other sources of more endurable and sustainable nature. Power from nuclear reactors, hydroelectric generators, solar energy, wind mills, geothermal and wave energy is receiving increasing attention and investments to make viable as alternate sources to fossil fuels.

Ethanol was at one time thought to be a viable alternate source for energy and early foray into this renewable source of energy resulted in its use for blending with diesel and gasoline to varying extent, at least to delay the day of reckoning vis-à-vis fossil fuels. Diverting valuable food resources like corn to alcohol production through yeast fermentation was justifiable as long as world was enjoying food surpluses but the situation dramatically changed during the last few years with food shortages and escalating prices of food grains world wide putting a dampener to this fuel program. Such a contingency led to explore the use of agricultural and plant wastes of cellulosic nature for extracting energy economically through the alcohol route and there are commercial plants now being established to produce cellulose based alcohol.

Butanol, a better energy source compared to ethanol, was known since World War II but economic compulsions never allowed it to get to the center stage, especially when fossil fuels were dirt cheap. The fermentation route using Clostridium acetobutylicum bacteria as the conversion agent and many sugar sources like sugar beets, sugarcane, corn grain,wheat,cassava, straw, corn stalks etc as feed stock, biobutanol is making a come back to compete effectively with bioethanol. The structure of butanol is heavier than ethanol and more similar to gasoline making it a better energy source with much wider range of uses like transportation fuel, blends with diesel, ethanol and gasoline, as jet fuel and for conversion into plastics. Its energy content is 29.2 MJ per liter (MJPL) compares well with gasoline with 32 MJPL or ethanol 19.6 MJPL. Since it does not blend with water, it has the added advantage of fitting into the existing fuel processing facilities.

Like ethanol, biobutanol can be fermented from plant sugars, either food grains or cellulosic plant parts. But because its structure is heavier than ethanol and more similar to gasoline, the advanced biofuel has a wider range of end uses -- it can be burned as a stand-alone transportation fuel; blended with diesel, ethanol or gasoline; converted into jet fuel or plastics; or sold in existing industrial chemical markets. Though the technical feasibility of promoting butanol as an energy source is beyond any doubt, the same argument that goes against ethanol, viz need for diverting food crops for its production, holds good for butanol also. A holistic thinking is imperative in arriving at a logical decision regarding the feed stock for biofuels, if they are going to be the true alternative for future energy supply without upsetting the world food supply.



Anonymous said...

n-butanol melts at -90C. I'm not sure where you got 25.5 from.

Dr. V.H . Potty said...

I stand corrected