The Ethanol Process

The Process of Making Ethanol

Making ethanol is simply a modified version of beer-making.  It was invented by the Persians, mass produced by the Egyptians, distilled into alcohol by Greco-Romans, used medicinally for decades and possibly centuries, and recently converted for use as energy.  But, we have had requests from potential investors and the curious to better understand its process.

There is an art to making beer, and the process can be quite involved.  There are even more steps when making alcohol out of it.  But, most of the basic components are the same.  This diagram shows the basic components used in making ethanol.  Simply, the Grinder cuts the feedstock (cellulose biomass) into smaller chunks.  The Pretreatment (which is called Hydrolysis), soaks the fibers with water.  Enzymes in the Liquifaction stage "mash" the material into a sludge.  Sugars must go through a Separation process because it is often necessary to remove the sugars that would not normally ferment.  *If the sugar separation process is not used, then the Mash would have to be cooled before coming in contact with yeast.  Once the yeast has made beer from the mash inside the Fermentation tanks (190 proof), then the alcohol must go through what is called Distillation in order to remove the rest of the water, or the vapor can build up and cause problems when used in a motor.  Afterwards, the Molecular Sieves are designed to filter any particles that may still remain in the alcohol.  The Bio-gas and CO2 that are produced by the yeast (or other organisms if any are used), are sometimes converted into energy through a Combined Heat and Power unit.  As a final step, the alcohol must be mixed with at least 10% gasoline as a Denaturant in order to be usable as a renewable energy source.  (Instead of equipping vehicles with a manual choke for starting the engine on cold mornings, cars in several countries now use what is called Flex-fuel technology.) 

Comparing Cellulosic Methods

This is a simplified explanation, since there are many technologies that use various systems and processes in hopes of generating additional product.  It is common to use acid in the Hydrolysis, but some companies use organisms, ethanol, or other processes.  Liquefaction typically requires the use of a particular set of enzymes, but some blends are used with specific feedstocks.  A few companies do not utilize Sugar Separation, and have pursued Xylitol-tolerant yeast instead.  Even the leftover pulp is used in a variety of ways, such as in the making of glass aggregate (sand for construction trades), gypsum for wallboard, or its thermal properties are used as a source for heating various ethanol systems.

For more details on the ethanol process, see Making Alcohol.

Comparing Cellulosic to Grains

What is important, is that systems for ethanol derived from cellulose material differ from grain ethanol systems, like corn.  That difference is significant when locating an economically sustainable bio-fuel to address challenges – such as when global oil peaks (surpasses its equalibrium stage to become scarce).  Although many of these components shown here look the same as what is used for making corn ethanol, there are some distinct differences between cellulose-based and grain ethanol systems.  When comparing cellulosic to grain ethanol, it can be easy to get confused. 

For starters, terminology is not always similar and that makes comparing cellulosic systems to grain ethanol that much more difficult.  Here in this article, terminology that is common to the cellulosic ethanol industry is used.  In this instance, a Hammer Mill performs relatively the same function as a Grinder, although one is designed to press corn kernels and the other to chop fiberous wood chips and other wastes.  The same is relatively true when comparing a Slurry Tank to Hydrolysis Pretreatment.  For a cellulosic system, however, the biomass must be pretreated during this stage in order to expose the softer material where the sugar exists.

One of the biggest differences between cellulosic and grain ethanol is that Sugar Separation does not exist on grain systems, and Mash Cooling is rarely found on cellulosic systems.  That is because the sugars in corn kernels are relatively easy to expose, and cellulose has a thick outer membrane called an exoskeleton that covers each fibril, a tough fiberous strand (see illustration).  Once the sugars are exposed by whatever method, cellulose contains less sugar than corn.  But, cellulose is still preferable.

Even with all these hurdles, it is worth it to find an economically sustainable solution for cellulosic ethanol because sources of cellulose are rediculously more abundant and are not climate restrictive.  The answer that many companies have sought is how to get more sugar out of the process.  When using acid in the pretreatment process, it destroys some of the sugar.  Most companies are attempting to get more sugar yield out of the sugar that exists by using better enzymes and yeast.  Some companies are using the alternate methods for pretreatment mentioned earlier.  Others still are trying to find better-producing crop sources.  But ultimately, they are only able to increase their productivity by 0.07 – 0.4%.

For more detailed comparisons of how 3F Inc's production yield is to other processes, see Ethanol Yield.