New flexible method to produce biofuels and electricity from waste products

October 15th, 2008 - 2:34 pm ICT by ANI  

Washington, Oct 15 (ANI): Researchers are proposing a new flexible approach to producing boifuels, hydrogen and electricity from municipal solid wastes, agricultural wastes, forest residues and sewage sludge.

The method offers a potential solution to problems that might be created by increasing production of ethanol with conventional methods, which use corn grain as a feedstock.

Boosting ethanol production with conventional methods would require additional crops and heavy fertilizer use, increasing runoff into waterways and threatening ecosystems.

The new concept, however, which Purdue researchers call a flexible carbon-to-liquid fuel process, would require no additional crops and use primarily wastes as the feedstock, according to Fu Zhao, a Purdue assistant professor of mechanical engineering.

This technique is more flexible than conventional methods because we can process a wider range of very different feedstocks and, at the same time, we can generate a wider range of end products - not just gasoline and diesel but ethanol and hydrogen. Or we could generate electricity directly from the gas produced, he said.

The method also would be immune to the market fluctuations of corn and other crops and less affected by disturbances such as feedstock supply shocks and market demand changes.

The method also could reduce greenhouse gas emissions by more than 50 percent compared with petroleum-derived gasoline.

The system first requires processing carbon-containing waste, such as paper, wood, plastic and rubber, into small pieces with a diameter of a few millimeters, or thousandths of a meter.

The pieces would then be fed into a gasifier, where the materials would be turned into a gas containing hydrogen, carbon monoxide, carbon dioxide, methane and other hydrocarbons .

This gas would be further processed to get rid of everything but the hydrogen and carbon monoxide, referred to as synthesis gas or syngas.

This gas could then be used to directly run a turbine to generate electricity, or it could be converted into gasoline and diesel fuel for transportation using a process called Fischer-Tropsch synthesis.

The technique could be used to produce ethanol, jet fuel and other biofuels from the solid wastes.

The analysis suggests that it is possible to replace 15 percent to 20 percent of transportation fuels consumed daily in the United States with liquids derived from this flexible process.

The researchers estimate the method would be economically competitive with petroleum-based fuels and plan to develop an integrated process simulation model to test the technique with a variety of feedstocks, including waste plastics.

Raw data for the model will be generated with an experimental gasifier being built at Purdue. (ANI)

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