Mar 23, 2007

Biofuels Process Could Meet All U.S. Transportation Needs

Purdue University chemical engineers have proposed a new environmentally friendly process for producing liquid fuels from plant matter (or biomass) potentially available from agricultural and forest waste that they said would provide all of the fuel needed for "the entire U.S. transportation sector."

The new approach, announced on March 14, modifies conventional methods for producing liquid fuels from biomass by adding hydrogen from a "carbon-free" energy source, such as solar or nuclear power, during a step called gasification. Adding hydrogen during this step suppresses the formation of carbon dioxide and increases the efficiency of the process, making it possible to produce three times the volume of biofuels from the same quantity of biomass, said Rakesh Agrawal, Purdue's Winthrop E. Stone Distinguished Professor of Chemical Engineering.

When conventional methods are used to convert biomass or coal to liquid fuels, 60 percent to 70 percent of the carbon atoms in the starting materials are lost in the process as carbon dioxide, a greenhouse gas, whereas no carbon atoms would be lost using H2CAR, Agrawal said.
 
So providing hydrogen derived from water through solar electrolysis reduces the amount of biomass needed," Agrawal said. "The average energy efficiency of growing crops is typically less than 1 percent, whereas the energy efficiency of photovoltaic cells to split water into hydrogen and oxygen is about 8 percent to 10 percent. I am getting hydrogen at a higher efficiency than I get biomass, meaning I need less land."

"Having said that, this is the first concept for creating a sustainable system that derives all of our transportation fuels from biomass," Agrawal said.

"This waste is due to the fact that you are using energy contained in the biomass to drive the entire process," he said. "I'm saying, treat biomass predominantly as a supplier of carbon atoms, not as an energy source."