Researchers at the University of Wisconsin-Madison,US,have developed a two-step method to convert the cellulose in raw biomass into a promising biofuel.
The process is unprecedented in its use of untreated,inedible biomass as the starting material.
The key to the new process is the first step,in which cellulose is converted into the platform chemical 5-hydroxymethylfurfural (HMF),from which a variety of valuable commodity chemicals can be made.
Other groups have demonstrated some of the individual steps involved in converting biomass to HMF,starting with glucose or fructose, said Ronald Raines,a professor with appointments in the Department of Biochemistry and the Department of Chemistry.
What we did was show how to do the whole process in one step,starting with biomass itself, he added.
Raines and graduate student Joseph Binder,a doctoral candidate in the chemistry department,developed a unique solvent system that makes this conversion possible.
The special mix of solvents and additives,for which a patent is pending,has an extraordinary capacity to dissolve cellulose,the long chains of energy-rich sugar molecules found in plant material.
Because cellulose is one of the most abundant organic substances on the planet,it is widely seen as a promising alternative to fossil fuels.
This solvent system can dissolve cotton balls,which are pure cellulose, said Raines. And its a simple systemnot corrosive,dangerous,expensive or stinky, he added.
This approach simultaneously bypasses another vexing problem: lignin,the glue that holds plant cell walls together.
Often described as intractable,lignin molecules act like a cage protecting the cellulose they surround.
However,Raines and Binder used chemicals small enough to slip between the lignin molecules,where they work to dissolve the cellulose,cleave it into its component pieces and then convert those pieces into HMF.
In step two,Raines and Binder subsequently converted HMF into the promising biofuel 2,5-dimethylfuran (DMF).
Taken together,the overall yield for this two-step biomass-to-biofuel process was 9 percent,meaning that 9 percent of the cellulose in their corn stover samples was ultimately converted into biofuel.