Chemists try to turn plant waste to fuel

By LIDIA WASOWICZ, UPI Senior Science Writer

A team of chemical engineers has taken the first step to turning plant wastes into Earth-friendly hydrogen fuel that one day could keep the lights burning and engines running without depleting diminishing reservoirs of precious natural resources.

Hydrogen, the most plentiful element in the universe, already is employed in the chemical-processing, food and fuels industries, but at a cost two or three times that of natural gas. Because hydrogen rarely stands alone, however, harnessing its power means devising ways to break the ties that bind it to a wide variety of chemical compounds. In laboratory experiments, detailed in the British journal Nature, the researchers devised a new way to extract hydrogen from plant and animal matter, collectively known as biomass.


Professor James Dumesic, research scientist Randy Cortright and graduate student Rupali Davda at the University of Wisconsin in Madison developed a platinum-based catalyst, similar to that in automobile catalytic converters, that breaks down glucose -- a sugar found in many fruits, animal tissues and fluids -- into hydrogen gas, carbon dioxide and methane at a cool 200 degrees Celsius (392 degrees Fahrenheit). This is significantly lower -- and more energy-efficient -- than the 800 degrees C (1472 degrees F) required to produce hydrogen by traditional high-temperature steam-reforming technologies.


Steam reforming uses thermal energy to separate hydrogen from the carbon components in methane -- a colorless, odorless, flammable gas obtained from natural gas -- and methanol or wood alcohol. Methanol is used, among other ways, as a solvent for varnishes and lacquers, as antifreeze and as a gasoline extender in the production of gasohol.

"An entire industry has been developed worldwide taking methane and converting it into hydrogen," said Esteban Chornet, principal engineer at the National Renewable Energy Laboratory in Golden, Colo., and professor of chemical engineering at Sherbrooke University in Quebec, Canada, who reviewed the findings.

"Renewable hydrogen production from biomass is being actively pursued in academic, institutional and industrial laboratories around the world, and the approach put forward (in the new study) represents progress in this direction," Chornet told United Press International.

The advance should sound an encouraging note with the environmentally minded: hydrogen combustion releases abundant energy and only water as a waste product.

To sweeten the deal, the glucose derives from a non-polluting, plentiful source: plant and animal waste. Glucose is produced profusely from cornstarch -- in the form of corn syrup as one example -- and also can be made from sugar beets or paper mill sludge, cheese whey, corn stover and other low-cost biomass waste.


"(The findings) provide experimental evidence that simple biomass-derived molecules, such as glucose and glycerol (derived from fats), can be treated to produce hydrogen with reasonable efficiency," Chornet and Stefan Czernik, senior research scientist at the Colorado lab, concluded in a commentary on the research.

"The authors suggest that, with some additional effort, their technique could also be technologically and commercially viable," they wrote.

For now, the residue is broken down by bacteria in a process too complex, inefficient and costly on a mass scale to capture much industrial attention, a drawback the researchers are determined to overcome. Dumesic and team have visions of harnessing hydrogen with a more-efficient, less-expensive method than bacterial fermentation, utilizing waste plant matter such as straw and the fibrous leftovers from corn production.

"Initially, cheap biomass waste sources will be targeted to extract the necessary sugars. Examples of such wastes are carbohydrate-rich cheese whey, corn stover and wood waste," Dumesic told UPI. "More work by researchers dealing with new extraction technologies will be needed to (lower the cost of) our process."

Numerous car companies, including DaimlerChrysler and Ford, are creating prototype hydrogen-powered electric vehicles that could be served by the technique as soon as it is refined sufficiently.


"The ... process allows the storage of hydrogen as a safe, non-toxic and non-flammable fuel," Dumesic told UPI. "The simplicity of the ... process should allow for on-site generation of hydrogen as a fuel gas for fuel cells, internal combustion engines or gas turbines."

Touted as a potential source of unlimited pollution-free power, hydrogen is only as clean as the process used to produce it. Currently, most hydrogen is made from natural gas and other fossil fuels employing multi-step, high-temperature methods that have fueled criticism and concern by environmentalists.

"Fossil-fuel stocks are a limited resource, and as the world's governments struggle to agree on a strategy to combat pollution and greenhouse-gas emissions ... the search for clear, renewable energy sources has never been more intense," Chornet and Czernik said.

The approach averts adding to the greenhouse effect that has been implicated in global warming, the Wisconsin researchers said.

"The process should be greenhouse-gas neutral," Cortright asserted. "Carbon dioxide is produced as a byproduct, but the plant biomass grown for hydrogen production will fix and store the carbon dioxide released the previous year."

The strategy converts half the glucose to hydrogen, the other half to carbon dioxide and gaseous "alkanes" such as methane. In contrast, more refined molecules such as ethylene glycol and methanol are almost completely turned to hydrogen and carbon dioxide.


Even so, glucose derived from waste biomass likely will prove more practical for cost-effective power generation, the scientists said. The reaction generates hydrogen in a liquid without the need for water vapor, netting major energy savings compared to the conventional, vapor-phase, steam-reforming processes, Dumesic said.

"The most probable short-term application of our process is for sources of energy from biomass waste streams, e.g., cheese whey. Other applications could be for 'village-power,' that is, power generation from a biomass feed stream in a location that is not on a power grid," Dumesic said. "In addition, our process could be used in 'distributed-power' applications, where power from a biomass feed stream (for example, on a farm) could be generated locally, and excess power could be used by the power grid."

Such applications are not imminent, Czernik cautioned.

"There is a long way to go before it can become a commercial process," he told UPI, "and it will have to compete with the other biomass-to-hydrogen approaches that are being developed elsewhere."

The scientists acknowledged their job is far from over. The platinum-based catalyst that drives the reaction is expensive, and new means must be devised to retrieve greater amounts of hydrogen from more concentrated solutions of sugars, they said.


"We believe we can make improvements to the catalyst and reactor design that will increase the amount of hydrogen we get from glucose," Dumesic said. "The alkane byproduct could be used to power an internal combustion engine or a solid-oxide fuel cell. Very little additional energy would be required to drive the process."

Efforts to replace petroleum-based energy by renewable sources eventually will yield a "hydrogen society," Dumesic concluded. "These changes in global energy production are expected to have tremendous economic and environmental benefits, since water is the only byproduct from generation of electrical power using hydrogen fuel cells."

Latest Headlines