Yet Another BioFuel Option: 2,5-Dimethylfuran
Investigators from the University of Wisconsin have presented "a catalytic strategy for the production of 2,5-dimethylfuran from fructose (a carbohydrate obtained directly from biomass or by the isomerization of glucose) for use as a liquid transportation fuel. Compared to ethanol, 2,5-dimethylfuran has a higher energy density (by 40 per cent), a higher boiling point (by 20 K), and is not soluble in water. This catalytic strategy creates a route for transforming abundant renewable biomass resources into a liquid fuel suitable for the transportation sector, and may diminish our reliance on petroleum."
"The team's method for making hydroxymethylfurfural (HMF) and converting it to DMF is a balancing act of chemistry, pressure, temperature and reactor design. Fructose is initially converted to HMF in water using an acid catalyst in the presence of a low-boiling-point solvent. The solvent extracts HMF from water and carries it to a separate location. Although other researchers had previously converted fructose to HMF, Dumesic's research group made a series of improvements that raised the HMF output and made the HMF easier to extract. For example, the team found that adding salt (NaCl) dramatically improves the extraction of HMF from the reactive water phase and helps suppress the formation of impurities."
The DMF contains 90 percent of the energy found in the carbohydrate and hydrogen feed.
Ethanol production creates 1.1 units of energy for every unit of energy consumed. This DMF process creates 2.2 units of energy for every unit of energy consumed.
The big potential drawback: because DMF has had little commercial potential to-date, its toxicology is not well understood. Therefore it is not possible state that hazards posed are acceptable in comparison to existing liquid fuel components. (Let's not forget the lessons the recent past with MTBE, or methyl tertiary butyl ether!)
DMF also has a rather complete entry in Wikipedia here. We recommend a look at the toxicology portion of that entry for a summary of what is known.
Other than that, DMF leaves ethanol in the ditch in terms of resource efficiency, from feedstock production through processing.