Biobutanol
Butanol is an alcohol that can be used as a transport fuel. It is a higher member of the series of straight chain alcohols with each molecule of butanol (C4H10O) containing four carbon atoms rather than two as in ethanol.
Butanol can be produced by traditional ABE fermentation - the anaerobic conversion of carbohydrates by strains of Clostridium into acetone, butanol and ethanol. However, cost issues, the relatively low-yield and sluggish fermentations, as well as problems caused by end product inhibition and phage infections, meant that ABE butanol could not compete on a commercial scale with butanol produced synthetically and almost all production ceased as the petrochemical industry evolved.
However, there is now increasing interest in use of biobutanol as a transport fuel. 85% Butanol/gasoline blends can be used in unmodified petrol engines. It can be transported in existing gasoline pipelines and produces more power than ethanol. Biobutanol can be produced from cereal crops, sugar cane and sugar beet, etc, but can also be produced from cellulosic raw materials.
To take advantage of these potential benefits, new production processes need to be developed.
Development of biobutanol
A number of companies are now investigating novel alternatives to traditional ABE fermentation, which would enable biobutanol to be produced on an industrial scale.
In June 2006, DuPont and BP formed a partnership to develop new biobutanol production technology using lignocellulosic feedstocks. In July 2009 the partnership was cleared to take over the US company Biobutanol LLC. In 2009, BP and DuPont formed Butamax™ Advanced Biofuels, Wilmington.
Butamax
Advanced Biofuels Fact Sheet (700 Kb)
In November 2009, BP and DuPont announced the formation of Kingston Research Ltd and the establishment of a £25 million advanced biofuels research centre in Hull for demonstration of biobutanol technology (scheduled to become operational in 2010). The first commercial-scale biobutanol facility is expected to begin operating in 2013.
On 25 September 2009, BP and Mazda announced an Ethanol Biobutanol blend would be used in the Petit Le Man Race, US.
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Sam Abuelsamid
Dyson Racing's LMP2 Lola-Mazda fuelled
by a bioethanol/
biobutanol blend. View
at larger size >>
In September 2009, Gevo, Englewood, CO announced that Gevo Integrated Fermentation Technology (GIFT™) will be used in an ICM demonstration plant in St. Joseph, Missouri to produce one million gallons of biobutanol per year by retrofitting an existing ethanol plant. The process can utilise much of the existing ethanol production system, but uses cellulosic yeast strains engineered to produce butanol instead of ethanol. In 2009, Gevo entered a licensing agreement with Cargill granting the company exclusive rights to use Cargill's host organisms in Gevo Integrated Fermentation Technology. Total has also reportedly invested in Gevo.
This builds upon research by James Liao at the University of California, who developed E.Coli strains with genes coding for 2 enzymes that converted keto acides into aldehydes, and aldehydes into 1-butanol. When further manipulated, the microbes were able to produce butanol at much higher efficiencies, suitable for industrial production. In 2008, Gevo acquired an exclusive license to commercialize Liao's technology
In the UK, Green Biologics has also developed butanol-producing GM microbial strains and will integrate these into a novel fermentation process. This technology advance should result in a step change in the economic viability of the fermentation and enable the large scale production of Green Biologics' Butafuel™ product. In September 2008, Green Biologics signed an agreement with Laxmi Organis Industries to build a commercial biobutanol plant in India. The company is also working with a new generation of biobutanol producers in China.
Other companies developing butanol technology include Cobalt Biofuels, Tetravitae Bioscience, and METabolic EXplorer, France.
Butalco GmBH, Switzerland is developing new production processes for biobutanol based on genetically optimised yeasts together with partners in downstream processing technologies.
In November 2009, researchers at UCLA announced that modified strains of Synechococcus elongatus could produce isobutyraldehyde and isobutanol directly from carbon dioxide [Source: Nature Biotechnology 27].
Research is also being carried out into the production of 2,3 butanediol (a potential biofuel) from agricultural residues (e.g. hydrolysis of hemicellulose-rich fractions by Trichoderma harzianum followed by fermentations using Klebsiella pneumoniae). Improved fermentation efficiency is one of the focuses of the FP7 SUPRABIO project.
Various biobutanol researchers are working with GM Colstridium strains.
Hydrolysis of cellulosic raw materials prior to butanol conversion potentially offers greatly increased yields. In research published by the USDA in 2007, wheat straw was hydrolyzed to lignocellulosic component sugars (glucose, xylose, arabinose, galactose, and mannose) prior to their conversion to butanol, by Clostridium beijerinckii P260. The rate of production of wheat straw hydrolysate to butanol was 214% over that from glucose.
Ongoing genetic research is focusing on 'gene knock-out' systems in Clostridium strains, whereby the enzymes that catalyse competing reactions (which produce Acetone, Ethanol, etc) are 'removed'.
Research into the ABE fermentation process has addressed issues of end-product inhibition and control of phage infection.
In the 1980s, hydrolyzates of lignocellulosic material were used to produce butanol on an industrial scale in Russia, and the processes developed have also attracted renewed interest from butanol researchers.