One of the persistent problems facing biofuels is transportation.
Cellulosic ethanol might be made economically in South Dakota, where corn stover is harvested. But trucking the biomass to a central refinery (or the finished fuel to Seattle for consumption) partially defeats the carbon savings and adds to cost.
Purdue University researchers say their hydrogen-consuming, high-heat process out performs convention biofuels plants
How to solve this dilemma? Researchers at Purdue University believe they have an answer. They plan to test a roving bio-refinery and claim it does a miraculous thing; it processes a broad range of source materials, from corn stover to switch grass, wheat straw and wood chips in the same tank using high heat and the addition of hydrogen.
The process is called fast-hydropyrolysis-hydrodeoxygenation. It makes use of a high-pressure reactor, injects hydrogen and heats the mixture to as much as 900 degrees in less than a second. The resulting liquid is less costly to cart to a finishing plant than the bulky plant material.
But the process adds several production problems, even as it promises to solve the biomass transportation dilemma. First, it relies on hydrogen, which require significant energy to make. Second, it fails to eliminate the need to transport the finished fuel to metropolitan markets hundreds, or thousands, or miles away.
Finally, heating the chamber to 900 degrees Fahrenheit in less than a second requires a lot of energy.
The researchers described their work in a paper published in June in the Environmental Science & Technology journal. Purdue has applied for a patent.
The scientists claim their technique produces more fuel than conventional biofuel processing. When hydrogen is derived from natural gas, yields will be twice as great. When it comes from the biomass itself, yields will rise 1.5 times.
“The biomass will break down into smaller molecules in the presence of hot hydrogen and…catalysts,” says chemical engineering professor Rakesh Agrawal. “The reaction products will then be subsequently condensed into liquid oil for eventual use as fuel. The uncondensed light gases such as methane, carbon monoxide, hydrogen and carbon dioxide, are separated and recycled back to the biomass reactor and the reformer.”
But power is an issue. Agrawal conceives of obtaining the hydrogen using solar power to split water instead of relying on natural gas or the biomass itself. In the meantime, he sees the process as economical during periods when oil prices spike.
On the other hand, mobile units are less capital intensive than permanent plants, he says.
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