Gas chromatography of biofuels

Gas chromatography (GC) has long been a primary analytical technique for analyzing petroleum-based fuels, but it is also used heavily in the rapidly developing biofuels industry. Petroleum-based fuels are a nonrenewable resource, and with the rapidly rising price of oil, the push to develop and expand the market for renewable biofuels is stronger than ever.

The most common biofuel currently in use worldwide is ethanol, which is produced via the fermentation of sugars, starches or cellulose, and currently draws quite heavily on corn as a starting product. Combined, the US and Brazil account for the vast majority of fuel ethanol production, as well as consumption. Per ASTM and other international standards, GC is used to determine the ethanol and methanol content of ethanol-based fuels. Despite the reduced pollution from ethanol, there are significant drawbacks to the fuel, such as its lower energy content, higher cost, corrosive nature and susceptibility to absorbing moisture. Although ethanol has become the leading biofuel for the time being, pure and blended ethanol fuels are not likely to be the dominant solution for automotive fuels in the longer term.

The second most common biofuel now in use is biodiesel, which is the primary biofuel used in Europe. Biodiesel, which is a term for Fatty Acid Methyl Esters (FAME), is produced along with glycerides via transesterification from vegetable oils with sodium hydroxide and either methanol or ethanol. Glycerins are harmful to engine performance, and so GC, per the standard approved methods, is used to determine the level of free glycerin and total glycerin in pure biodiesel and biodiesel blends, which is indicative of the fuel quality. Pure and blended biodiesel, like ethanol, produces less pollution, but has fewer drawbacks than methanol, and could conceivably become the more dominant of the two biofuels in the longer term. Other biofuels, such as methanol and butanol, also require GC analysis.

The GC configurations used for standard methods of analysis are relatively simple, and employ a single colum and a flame ionization detector. However, the significant improvements made in GC splitting hardware could make two-dimensional GC (see IBO 3/31/08) a useful method because of its significant time savings.

Although a very small percentage of the more than $1.3 billion global GC market, biofuels analysis is now quite a significant percentage of the petroleum and agricultural end-user segments of the GC market. At least $30 million was spent on GC in 2007 for biofuels analysis applications, which is a figure that is likely to grow rapidly over the next several years. The good news for the GC market is that, while it is questionable just which biofuel will be used in the long run, most, if not all, will rely on analysis by GC. The research into developing more efficient biofuels that produce lower emissions will also be a catalyst for GC demand.

Biofuel GC at a Glance:

Leading Suppliers

• Agilent

• PerkinElmer

• Shimadzu

• Varian

Largest Markets

• Biodiesel

• Ethanol

Instrument Cost

• $10,000–$75,000

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