April 28, 2008

Designer plants may produce hydrogen for fuel

Scientists at Argonne National Laboratory, the University of Illinois and Northwestern University are collaborating to design plants that use photosynthesis to churn out hydrogen, which could be a clean alternative to fossil fuels.

And they think the single-celled algae is well-suited to the task.

"This is long-term research," said David Tiede, a senior chemist at Argonne. "Hydrogen is one generation or two generations away as the basis for our energy, but we have to start now to find efficient ways to extract it."

Algae has no roots, can be grown in water anywhere and creates an enzyme, hydrogenase, that separates hydrogen gas from water. Like most plants, algae combines carbon dioxide, sunlight and water to create biomass, biological material that can be used as fuel or for industrial production. With excessive sunlight, some unwanted byproducts are converted to hydrogen by the enzyme.

Tiede and his colleagues believe they can incorporate that hydrogen into the algae's core photosynthesis process, making hydrogen a primary product.

"We're suggesting the idea of photosynthesis to do hydrogen reduction instead of carbon dioxide reduction," Tiede said. "That would be much more efficient than current processes that must break down biomass to get usable energy."

There is a "friendly competition," Tiede said, between scientists who back biological ways to harvest hydrogen and those following a non-biological path.

Engineers working with semiconductors can use silicon-based technology to convert sunlight to electrical energy, but they face the problem of storing that electrical energy efficiently.

Some researchers use inorganic means to split water into oxygen and hydrogen, providing hydrogen gas as a clean fuel. But today's technology relies on using metal catalysts that are expensive and toxic, Tiede said.

"Biology already splits water into hydrogen for us using materials that are cheap and clean," Tiede said. "Our research has value not just for biofuels, but also for those working with inorganic systems who seek better catalysts."

Today's oil-based energy infrastructure supports the conversion of corn to ethanol: Automobiles can run on ethanol-gas blends and existing filling stations can, without too much trouble, supply ethanol fuels in the same way they supply petroleum-based fuels.

Changing the infrastructure to enable hydrogen-powered vehicles to refuel easily is a huge hurdle, one reason no one will be buying algae-fueled hydrogen sedans any time soon.

But the prospect of re-engineering plants to provide efficient petroleum alternatives is a notion gaining momentum, Tiede said.

"This is really cutting-edge bioengineering research," he said. "Energy has become a high national priority. This used to be an esoteric field, but not any more."

Nanomaterials and safety: The growing popularity of products using nanomaterials, or superminiature substances, has caused concern about their unknown effects on the environment.

For example, sunscreens made from bulk forms of zinc oxide block harmful ultraviolet rays by coating the user's skin with a visible white film. Zinc oxide in the nano form blocks the rays using nanotechnology that renders the oxide invisible to the human eye, and the dangers of the tiny materials to humans and the planet are hotly debated.

It will take an enormous amount of research to understand nanomaterials' impact. But one early result from Purdue University may provide some comfort. Researchers found that a nano form of carbon known as the buckyball doesn't appear to affect micro-organisms that are at the foundation of the planet's ecosystem.

The scientists injected massive amounts of nanoparticle carbon into wastewater to gauge its effect on the microbes that break down organic materials. The experiment was analogous to pouring 10 pounds of talcum powder on a human being, the researchers said.

"We found no effect by any amount of carbon 60 on the structure or the function of the microbial community over a short time," said Leila Nyberg, the study's leader.

The study could serve as a template for future experiments using other nanoparticles, the researchers said.


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