"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 8-10 percent. I am getting hydrogen at a higher efficiency than I get biomass, meaning I need less land."
Using coal exclusively to produce liquid fuels for the nation's transportation sector could deplete all coal deposits in the United States in about 90 years, whereas H2CAR would enable the known coal reserves to last 140 years.
The researchers suggest in the paper the chemical processing steps needed to make the new approach practical. But making the concept economically competitive with gasoline and diesel fuel would require research in two areas: finding ways to produce cheap hydrogen from carbon-free sources and developing a new type of gasifier needed for the process.
"Having said that, this is the first concept for creating a sustainable system that derives all of our transportation fuels from biomass," Agrawal said.
Purdue has filed a patent for the concept. The approach is in the conceptual stages, and a plan for experimental research is in progress.