Making Bio-based Butanol More Competitive
We all want to live in a clean and green environment and leave this planet in a livable condition for future generations. Scientists are continuously trying to find alternative clean and green fuel for our daily use. These days we hear and read about ethanol and biobutanol as alternative fuels. Biobutanol seems to have several advantages over ethanol. New pipelines are not required for transportation of biobutanol – existing pipelines will do. Biobutanol is less corrosive compared to ethanol. Biobutanol is less prone to water contamination. Biobutanol can be used alone in internal combustion engines or it can be mixed with gasoline. Biobutanol provides more energy per gallon than ethanol.
Using biobutanol as fuel is nothing new. Earlier it was produced from fermented sugars drawn from corn glucose. But large scale commercial production of such biofuels was not possible due to high recovery costs, low yields and easy availability of conventional fuels. But conditions are different now. Our environment is more polluted, reserves of conventional fuels are not going to last forever and gasoline prices keep fluctuating alarmingly.
According to Agricultural Research Service (ARS) chemical engineer Nasib Qureshi tried a modified method of producing biobutanol. His quest for preparing biobutanol from wheat straw started in 2003 because wheat straw is present in abundance and its cost would be lower than corn-glucose dependent feedstock.
Clostridium bacteria is a favorite of scientists for the purpose of fermentation. Nasib Qureshi also used this Clostridium for the important task of fermentation. Preparation of biofuels mainly involves four preparatory steps such as pretreatment, hydrolysis, fermentation and recovery. These steps have to be carried out separately and sequentially. But Qureshi and his team members deviated from this traditional method and combined three of the four steps. They employed a procedure known as “gas stripping” to extract the biobutanol. First the wheat straw has been pretreated with dilute sulphuric acid or other chemicals. Next the material is fermented in a bioreactor containing three different types of commercial enzymes and a culture of C. beijerinckii P260, a strain Qureshi obtained from Professor David Jones of the University of Otago in Dunedin, New Zealand. Here Qureshi has combined the two steps.
The bacteria and enzymes do their jobs simultaneously. First the enzymes hydrolyze the straw and release simple sugars then the bacterias start fermenting those sugars into acetone, butanol and ethanol. Butanol is produced in greatest quantity but other two are also valuable components. “Feb batch feeding” method increased the butanol production. Qureshi says he is planning to scale up production levels in 2009. “Then, we’ll look at the economics of using hydrolyzed wheat straw to see how we’re doing and move this process forward.”