Chemical engineers at Purdue University have developed a new method to process agricultural waste and other biomass into biofuels— fast-hydropyrolysis-hydrodeoxygenation, called the H2Bioil process (earlier post)—and are proposing the creation of mobile processing plants that would rove the Midwest to produce the fuels.
The approach sidesteps a fundamental economic hurdle in biofuels: Transporting biomass is expensive because of its bulk volume, whereas liquid fuel from biomass is far more economical to transport, said Rakesh Agrawal, the Winthrop E. Stone Distinguished Professor of Chemical Engineering.
Material like corn stover and wood chips has low energy density. It makes more sense to process biomass into liquid fuel with a mobile platform and then take this fuel to a central refinery for further processing before using it in internal combustion engines.
The H2Bioil process works by adding hydrogen into a high-pressure biomass-processing reactor subjected to extremely fast heating, rising to as hot as 500 °C (932 °F) in less than a second. The hydrogen for the mobile plants would be reformed from natural gas or from a syngas from the gasification of the biomass itself. However, Agrawal envisions the future use of solar power to produce the hydrogen by splitting water, making the new technology entirely renewable.
The new method would produce about twice as much biofuel as current technologies when hydrogen is derived from natural gas and 1.5 times the liquid fuel when hydrogen is derived from a portion of the biomass itself.
The biomass will break down into smaller molecules in the presence of hot hydrogen and suitable catalysts. 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.
Purdue has filed a patent application on the method.
The researchers previously developed an approach called a “hybrid hydrogen-carbon process,” or H2CAR. Both H2CAR and H2Bioil use additional hydrogen to boost the liquid-fuel yield. However, H2Bioil is more economical and mobile than H2CAR, according to former chemical engineering doctoral student Navneet R. Singh.
The research was funded by the US Department of Energy, the National Science Foundation and the US Air Force Office of Scientific Research, and is affiliated with the Energy Center at Purdue’s Discovery Park.