Environmental Health & Safety / Water/Wastewater

Potent Potions Convert Cellulose to Fuels

Two recent developments promise to boost prospects for biofuels.

Researchers at the University of Wisconsin – Madison, Madison, Wis., have devised a two-step process that converts cellulose into 2,5-dimethyl furan (DMF), a potential fuel. Meanwhile, a team from Virginia Tech, Blacksburg, Va., the University of Georgia, Athens, Ga., and the U.S. Department of Energy’s Oak Ridge National Laboratory, Oak Ridge, Tenn., have developed an enzyme “cocktail” that produces hydrogen from cellulosic materials.

At the University of Wisconsin, Ronald Raines, a professor in the departments of chemistry and biochemistry, has developed a mix consisting of solvents and additives that can dissolve cellulose. “This solvent system can dissolve cotton balls, which are pure cellulose,” says Raines. “And it’s a simple system — not corrosive, dangerous, expensive or stinky.”

The patent-pending mix uses chemicals small enough to slip between the lignin molecules that surround cellulose. It dissolves the cellulose, creating components that then form 5-hydroxymethylfurfural (HMF). Then, in a second step, the HMF is converted to DMF, a water-immiscible liquid with the energy content of gasoline that already serves as a gasoline additive.
woodchips into hydrogen
Figure 1 --  Cocktail for chips: Mixture of enzymes
converts wood chips into hydrogen.
Source: Virginia Tech.

In tests with corn stover, about 9% of the cellulose in that waste ultimately was converted into DMF. “The yield of DMF isn’t fabulous yet, but that second step hasn’t been optimized,” notes Raines. “Our process is so general I think we can make DMF out of any type of biomass,” he adds.

The Virginia Tech/Georgia/Oak Ridge team relies on a cocktail of 14 enzymes and one coenzyme to make hydrogen. The endothermic reactions take place in water at about 90°F. “In addition to converting the chemical energy from the sugar, the process also converts the low-temperature thermal energy into high-quality hydrogen energy,” notes Percival Zhang, an assistant professor at Virginia Tech (Figure 1).

The hydrogen production rate is over eight times faster than what the researchers have previously achieved using starch. Yield also is high, ∼11.2 H2/anhydroglucose unit of cellulosic materials, the highest level yet reported, they claim.

The team used cellulosic material isolated from wood chips but the technique also could handle crop waste or switch grass.