Several technologies are emerging for the production of ethanol from non-conventional feed stocks that do not have readily available starch and fermentable sugars. This process is now called CELLULOSIC ETHANOL. 

The “new” processes involve the hydrolysis of polysaccharides in cell walls of fiber and woody plant materials. This structural material known as lignocellulose is composed of cellulose fibers embedded in a cross-linked lignin-hemicellulose matrix.

Breaking this component is difficult, because lignocellulose is resistant to both chemical and biological attack. 

A variety of physical, chemical and enzymatic processes have been developed that allow the recovery from the cellulose of 5-carbon sugars and 6-carbon sugars (hexoses) which can be fermented and distilled to produce ethanol. The leftover lignin is not recovered and simply burned as boiler fuel. 

Up to now the industrial processes in commercial operations are not cost competitive. The cost per gallon is 3-4 times higher than conventional corn-ethanol. 

One of the major costly steps corresponds to pre-treatment of the lignocellulose, which accounts for 33% of the total processing cost. The energy use is very high during the pretreatment phase and grows exponentially when reducing particle sizes to apply enzymatic hydrolysis. 

For the Hydrolysis phase there are three basic technologies: 

1.      Concentrated Acid

2.      Dilute Acid

3.      Enzymatic Hydrolysis

Most of the cellulosic commercial plants are using some form of Enzymatic Hydrolysis, but the quantity required and costs of the enzymes is not commercially competitive yet. (Over time there may be reductions in the price of enzymes). 


The design and engineering of the company's 2nd. generation advanced bio-fuel plant includes the utilization of multi-feedstock such as Corn, Grain Sorghum, Sweet Sorghum and others. The advanced design also allows adding more commercially viable cellulosic pathways to increase yields and to qualify more of the production for the advanced bio-fuel RINS. 

Among the unique features that may make the plant to increase the Cellulosic production of ethanol are: 

1.      Production of its own CHP (ENERGY) thru the anaerobic digester and the production of bio-gas

2.      Propriety Super Heat Steam Technology. 

3.      Favorable bio-mass such as corn cobs readily available from local farmers. 

The above factors will allow producing cellulosic ethanol in a cost per gallon similar to conventional dry milling corn ethanol production.  

Benchmark has access to a patented process similar to a process developed in the 1930’s for the production of fiberboard that will be adapted in existing plants in a cost effective way. 

It involves the creation of a Thermal Expansion during the pre-treatment phase. 

The Thermal Expansion involves saturation of the pores of the plant materials with steam followed by a rapid decompression. The explosive expansion of heat reduces the plant material to separated fibers, increasing the accessibility of polysaccharides to subsequent hydrolysis. The steam needs to reach temperatures of 220-270 Centigrade and the resident time varies between 40-90 seconds. 

Corn Cobs have very high hemicellulose content and are particularly easy to digest. Pre-hydrolysis at temperature of 150 Centigrade converts the hemicellulose to xylose after only 5 minutes.  

For the Hydrolysis phase, Benchmark proposed pathway uses Acid Hydrolysis (Sulfuric Acid). The large volume of acid required about equal the weight of sugars produced; therefore, to be cost effective, the sulfuric acid needs to be recovered and recycled. 

The recovery of sulfuric acid has a high boiling point.  Available state of the art instrumentation controls in the  distillation flash  extraction points, allowes for a very precise recovery.

Copyright June 1, 2017