Sep 15 2014
Image Credit: Rost9/Shutterstock.com
Article updated on 18/02/20 by Susha Cheriyedath
Biobutanol is a four-carbon alcohol produced by the fermentation of biomass. It has a long hydrocarbon chain which renders it non-polar. The production of biobutanol can be carried out in ethanol production facilities. The primary use of biobutanol is as a fuel in internal combustion engines.
Its properties are similar to that of gasoline. Some gasoline-powered vehicles can even use biobutanol without being modified. It can be blended with gasoline in concentrations up to 11.5% by volume. However, it has a lower energy content, on average 10-20%, than that of gasoline, which is a major disadvantage of biobutanol.
Biobutanol exhibits the potential to reduce carbon emissions by 85% when compared to gasoline, thus making it a viable and suitable alternative to gasoline and gasoline-ethanol blended fuels.
Biobutanol Production Technologies
Biobutanol is mainly derived from the fermentation of sugars in organic feedstocks. The most common method of producing biobutanol is the fermentation of simple sugars in biomass feedstock.
Butanol is a by-product of this process in addition to ethanol and acetone. The process, known as Acetone Butanol Ethanol, uses the microbial species Clostridium acetobutylicum. However, this microbe can easily be poisoned by butanol when the alcohol concentration rises above approximately 2%.
Biobutanol can also be produced using Ralstonia eutropha H16. This process requires the input of electricity and carbon dioxide, and the use of an electro-bioreactor. It can be produced from algae or diatoms with the help of solar energy.
In recent years, petroleum prices have been steadily increasing yet fermentation remains an inefficient method of producing biobutanol due to the low biobutanol yield of the Clostridium species.
Manipulation of metabolic networks within bacterial species can provide higher yields of biobutanol. Optimization can also be accomplished by the transfer of specific genetic information to other unicellular species to achieve a higher biobutanol production rate.
Advantages of Biobutanol
At high concentrations, biobutanol is blended with conventional petrol rather than ethanol for use in unmodified engines. Experiments have also proved that biobutanol can be used in unmodified conventional engines at 100%. However, no manufacturers have guaranteed use of blends greater than 15%.
Biobutanol has a higher energy content than ethanol. With an energy content of about 105,000 BTUs/gallon, biobutanol is close to the energy content of gasoline, which is roughly 114,000 BTUs/gallon.
Less corrosive and explosive than ethanol, biobutanol is also less susceptible to separation in the presence of water than ethanol. It can be produced domestically from a variety of feedstocks, which can also help drive the economy via the generation of jobs.
Carbon dioxide captured by growing feedstocks minimizes overall greenhouse gas emissions by balancing carbon dioxide released from burning biobutanol. Environmental Protection Agency (EPA) test results show that biobutanol reduces hydrocarbon, carbon monoxide and nitrogen oxide emissions.
Applications of Biobutanol
There is now increasing interest in the use of biobutanol as a transport fuel. Unfortunately, no production vehicle is known to be approved by manufacturers for use with 100% biobutanol.
Biobutanol also shows promise as an industrial solvent and chemical feedstock. In addition to this, possible other applications include paints/coatings, resins, plasticizers, pharmaceuticals, food-grade extractants, chemical intermediates, and herbicides.
The Future of Biobutanol Use
Several breakthroughs in biobutanol processing methods and the development of genetically modified microorganisms have set the stage for biobutanol to topple ethanol as the best renewable fuel. Biobutanol shows great potential as a motor fuel, industrial solvent, and chemical feedstock, owing to its higher energy density and better fuel economy when compared to ethanol.
Apart from the increasing popularity of biobutanol due to its advantages, its yield percentage and production speed are based on the organisms that process the substrates. Efforts are currently in progress to enhance the metabolism of the existing microbes used for fermentation. Another major drawback is the cost of separation of butanol from the fermentation broth. However, several membrane-based separation methods are currently under research, which are likely to reduce the costs of biobutanol by 40-50%. Biobutanol seemingly has a promising future through the integration of genetic engineering and membrane separation.
References and Further Reading