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 was tradionally produced by 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 ABE 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 per litre than ethanol. Biobutanol can be produced from cereal crops, sugar cane and sugar beet, etc, but can also be produced from cellulosic raw materials.

In October 2013, ASTM D7862 was announced for blends of butanol with gasoline at 1 - 12.5 % vol in automotive spark ignition engines. The specification covers three butanol isomers: 1-butanol, 2-butanol, and 2-methyl-1-propanol. The specification specifically excludes 2-methyl-2-propanol (that is, tert-butyl alcohol).

Commercial 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. These are summarised below.

The two leading technology developers in this area, Gevo and Butamax, have been involved in a patent dispute. Up-to-date information on the respective positions of each company is available from their websites. The information presented on this page was believed to be accurate at the time of writing. However, neither the members of the European Biofuels Technology Platform, the Secretariat, the European Commission, nor any other individual or organisation involved with this activity, accept responsibility or liability whatsoever with regard to the material on this web page or the use to which it is put.

pdf Gevo white paper on iso-butanol

On 24 May 2012, announced that it has commenced production at the world's first commercial-scale 18 MGPY biobutanol plant, developed by conversion of the former Agri-Energy corn ethanol plant in Luverne. Ground was broken at the plant in May 2011, and Gevo aims to be producing 1m gallons of isobutanol per month by the end of this year (2012).

As at June 2012, a further seven ethanol plants had expressed an interest in retrofiting isobutanol production technology.

In December 2013, Gevo announced that the U.S. Army succesful trials of a 50/50 blend of Gevo's ATJ-8 fuel in a Sikorsky UH-60 helicopter. The use of 16% isobutanol in UL 87A pumps has also been approved by Underwriter Laboratories, with no need for any equipment modification.

pdf Butamax Advanced Biofuels Fact Sheet

In October 2013, Butamax™ Advanced Biofuels LLC, and Highwater Ethanol LLC, a leading producer of first generation ethanol, commenced a retrofit of Highwater’s ethanol plant in Lamberton, Minnesota for the production of biobutanol. Butamax’s cutting edge technology package will include the installation of novel corn oil separation technology. Butamax and Highwater have entered into definitive agreements for license of Butamax’s patented corn oil separation technology, which is an integral part of a full retrofit to biobutanol production and can also be installed independently as a first phase of the conversion. Installation of the patent protected Butamax separation system has already commenced with commercial production expected this winter.

In April 2012, Butamax entered into collaboration with leading biofuels engineering and construction company Fagen Inc. for commercial-scale biobutanol production (via retrofit of ethanol plants) using Butamax technology.

Steps to commercilisation of butanol as an advanced biofuel

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 technology built 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 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’s business model is to offer current ethanol producers proprietary biobutanol technology to permit improved biofuels growth and plant profitability. In December 2011 Butamax™ Advanced Biofuels announced agreement on commercialization principles with Highwater Ethanol, the first entrant to the Butamax Early Adopters Group [Source: Butamax™ website].

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 2014.

The Abengoa method for production of butanol via catalytic condensation

The Abengoa production method involves catalytic condensation of ethanol to produce butanol through the Guerbet (2CH3-CH2OHCH3- CH2-CH2-CH2OH + H20) reaction. The company has developed and patented a catalyst that enables the manufacture of biobutanol competitively. In November 2013, Abengoa announced that it has produced butanol with 99.8% purity and plans to start commercial-scale produciton of butanol in 2015.

The process allows a butanol plant to be built as an 'add on' to an existing commercial ethanol plant, enabling the production of butanol without having to halt the ethanol production process

Other developments and demonstrations in butanol production

In the UK, Green Biologics has 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 January 2012, Green Biologics Limited announced a merger with butylfuel™ Inc., US. The new company will operate under the Green Biologics name with headquarters in the UK, but with a strong operational presence and commercial focus in the US contributed by Green Biologics, Inc. [Source: Green Biologics]. Previously, Green Biologics was also involved in biobutanol development in India and China.

Other companies developing butanol technology include Cobalt Biofuels, Tetravitae Bioscience, and METabolic EXplorer, France.

In April 2013, it was announced that Cobalt Technologies, Naval Air Warfare China Lake Weapons Division, Show Me Energy Cooperative and NREL will cooperate in a $2.5m pilot plant for conversion of 'switchgrass butanol' to military-grade jet fuel. In March 2012 it was announced that Albermale would manufacture biojet fuel from butanol, provided by Cobalt, using NAWCWD's alcohol to jet technology. Cobalt and Rhodia have formed a partnership to develop a demonstration plant in Brazil to convert sugarcane bagasse and other non-food feedstocks into biobutanol.

Global R&D on production of butanol and use as a transport fuel

Butalco GmBH, Switzerland is developing new production processes for biobutanol based on genetically optimised yeasts together with partners in downstream processing technologies.

Optinol has developed a "patented non-GMO clostridium strain that naturally and prolifically favors the production of butanol, without acetone or ethanol". The technique has been developed by researchers at Louisiana State University, US. Optinol says the method can produce butanol at cost parity with bioethanol.

In August 2013, The United States Department of Agriculture (USDA) awarded Microvi Biotechnologies a grant to "develop a breakthrough technology to dramatically improve the yield and performance of biobutanol processes. The technology overcomes toxic and inhibitory effects on butanol producing microorganisms, a major bottleneck in scaling existing biobutanol processes." [Source: Microvi website].

The Wass Research Group, University of Bristol, UK, is developing improved catalysts with yields of 95% offering lower-cost conversion of ethanol to butanol, and potentially enabling ethanol producers to avoid high retrofit costs. Researchers now plan to scale-up the current lab technology as a first step towards commercialisation [Ref: Catalytic Conversion of Ethanol into an Advanced Biofuel: Unprecedented Selectivity for n-Butanol, Prof. Duncan F. Wass etal, Angewandte Chemie International Edition, Volume 52, Issue 34, pages 9005–9008, August 19, 2013].

University of Michigan is developing a method for butanol production from cellulosic plant material using a combination of Trichoderma reesei and E. coli in a bioreactor. See 'Design and characterization of synthetic fungal-bacterial consortia for direct production of isobutanol from cellulosic biomass', Proceedings of the National Academy of Sciences [19 August 2013].

Archive 'research notes' on biobutanol production

It was reported that State corporation, Russian Technologies, will begin construction of a biobutanol factory in the Irkutsk region in spring 2011. The factory will use wood chips and other timber byproducts [Source: Moscow Times].

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 (the technology pathway for the new biobutanol factory was not mentioned in the news release).

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 was 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 was one of the focuses of the FP7 SUPRABIO project.

Various biobutanol researchers are working with modified Clostridium 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 focused 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, but this technology has now been superceded by more advanced biotechnology, which are now being demonstrated at commercial-scale (as described above).