by Irshad Ahmed (Lee Enterprises) ... I believe cellulosic ethanol is here to stay for the long haul and it is finally exhibiting real potential to establish a critical-mass commercial base alongside the corn-ethanol industry. Its commercial success will come from the technical ability of the processes to extract value from all components of the biomass material in addition to cellulosic ethanol from primary sugars.
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The slow progress can mostly be attributed to the widely gyrating public policy that injected not only a great deal of uncertainty into the marketplace regarding the future of cellulosic ethanol, but it also elevated financial investment risks for the willing investors. This was mainly due to lack of clarity and/or commitment of public policy backing the future of biofuels through executable programs that are consistent over longer time horizons—a necessary ingredient to induce confidence in the investment community.
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One other important factor that contributed heavily to the limited success of the first attempts to commercialize cellulosic ethanol was due to the fact that almost all technology developers only focused on extracting and converting only the C6 glucose sugar derived from the cellulosic portion of the lignocellulosic biomass material—which under the best circumstances represented under 50-percent of the biomass material being processed. This approach not only suffered with low ethanol yields but it also wasted higher-value C5 xylose sugars from hemi-cellulosic portion of the biomass and lignin by utilizing it as the boiler fuel to provide process heat.
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The last two decades of research and development activities resulted in four major technological pathways for cellulosic ethanol production:
- Dilute Acid Hydrolysis;
- Concentrated Acid Hydrolysis;
- Enzymatic Hydrolysis; and
- Biomass gasification to SynGas followed by fermentation or catalytic conversion to ethanol