Biofuels of tomorrow

A new study claims that by 2030 the US could conceivably produce up to 90 billion gallons of biofuels a year, sufficient to replace nearly a third of its gasoline use. The vast majority of this would be made up of cellulosic ethanol, with the remainder conventional corn-based ethanol.

Speaking at the launch of the study on 10 February, Brent Erickson, executive vice president of the US Biotechnology Industry Organization’s industrial and environmental section, said: ‘This new study shows clearly that building US production of cellulosic biofuels is a sound way to significantly reduce US reliance on imported petroleum in the transportation sector.’

The 90-Billion Gallon Biofuel Development Study was conducted by researchers from Sandia National Laboratories and the US car giant General Motors. Its aim was to determine what needs to happen for the US to produce 36 billion of gallons of biofuels by 2022 and 60 billion gallons by 2030.

To find out, the researchers developed a dynamic model of the whole biofuel production process, from growing the plant-based feedstock to distributing the subsequent biofuel. This involved utilising information on various different types of feedstock, such as switchgrass and straw, and biofuel production processes, including both biochemical and thermochemical. This information was provided by numerous biofuel producers, feedstock developers and research laboratories.

Using this model, the researchers discovered that the US should be able to meet the stated biofuel goals, assuming steady advances in biofuel production technology.

Cellulosic biofuels will account for around three-quarters of the 60 billion gallons. This will require 480 million tons of plant biomass, comprising agricultural and forest residue, such as straw and wood chips, and energy crops and small trees grown on land not currently used to grow food crops.

Indeed, the researchers calculated that there should actually be enough biomass to produce 75 billion gallons of cellulosic ethanol by 2030, generating a total of 90 billion gallons of biofuels. Even 60 billion gallons would be a major contribution, however, replacing one-fifth of US gasoline use and reducing carbon dioxide emissions by 260 million tons a year, equivalent to 45 coal-fired power stations.

According to the researchers, there are no fundamental technological or economic barriers preventing this predicted future from coming to pass. With the assumed technological advances, cellulosic biofuels should be able to compete with gasoline at a price of just $70–120 a barrel.

However, the researchers suggest that the path to this predicted future could be smoothed by implementing measures such as carbon taxes and loan guarantees for cellulosic biorefineries, and by continued government investment in biofuel research.

An example of the kind of technological advance envisaged by the researchers was recently provided by two chemists from the University of Wisconsin-Madison. In a paper published in the Journal of the American Chemical Society, Joseph Binder and Ronald Raines report the development of a novel method for converting plant biomass such as corn stover and pine sawdust into liquid fuel.

This method involves immersing the biomass into a special liquid solvent comprising dimethylacetamide and lithium chloride, which dissolves the cellulose in the biomass and converts it into an organic molecule known as 5-hydroxymethylfurfal (HMF). Using a copper-based catalyst, this HMF can then be transformed into a compound known as 2,5-dimethylfuran (DMF), which is already being investigated as a potential fuel.

One of the really interesting aspects of this work is that the biomass doesn’t need to be treated to remove the lignin and expose the cellulose. This is because the solvent molecules are able to squeeze past the lignin to get directly at the cellulose.

But there was also a recent demonstration of the kind of hurdles that still need to be overcome. On 9 February, the US biofuel company Lignol Energy announced that it was abandoning plans to construct a novel cellulosic ethanol biorefinery with Suncor Energy. It attributed this decision to ‘the instability of energy prices, the uncertainty in the capital markets and the general market malaise’.

The construction of the biorefinery had originally been announced a year ago (see Gaining momentum), with the project receiving a $30 million grant from the US Department of Energy. Lignol says that it is now exploring alternative uses for this grant money.

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