Cellulose based Ethanol has a Great Potential.

posted by Sumukee @ 1:28 AM | Monday, September 28, 2009 0 Comments

As discussed in my earlier posts, cellulosic ethanol is the most abundant biological material present on earth and deriving oil from it is indeed an excellent idea. There are a number of economic, social and sustainability issues faced by this industry. Research is underway to curb these bottlenecks so as to start using a sustainable biofuel such as Cellulosic Ethanol.

The major advantage offered by the cellulose based ethanol fuel is the fact that the feedstock is very cheap. However, purification of the feedstock seems to pose a problem when economic barriers are taken into consideration. These impurities, if not properly removed even damage the equipments.

Using cellulosic ethanol might not interfere with the food chain, as only non- food crops are being used as a biomass. The problem, here again, is the complexity of the cellulosic molecule; it is extremely hard to digest (or) hydrolyze the cellulosic material, which requires lot of expensive enzymes to break – up them unlike the starchy y materials. I think the solution of using the wonder bacteria would solve the problem of digesting the cellulosic biomass and has gained a lot of popularity among the ethanol researchers.

U.S is one of the top-leaders in cellulosic ethanol research and considerable research is being taken by the researchers there to gain some energy independence. The ethanol from cellulose (that is the way they term the name), also known as EFC employs cost effective methods such as acid-hydrolysis. Generally, there are three methods to digest the cellulosic biomass (a) Acid-hydrolysis (b) enzymatic-hydrolysis (c) thermo chemical processes. However, most popularly used method is the acid –hydrolysis due to the cheapness of sulfuric acid.

Acid-hydrolysis can be either dilute or concentrated; dilute-acid hydrolysis is usually performed at high temperatures and pressure. The barrier we face here is that the fact that, when high temperatures and pressure is applied it sometimes damages the equipment. Hence, specialized equipment having the ability to withstand high temperature and pressure must be brought into use. These specialized equipments are available only in exorbitant prices. Yet another issue is the efficiency of this method is only 50% thereby yielding less sugar. The biggest advantage of dilute acid processes is their fast rate of reaction, which facilitates continuous processing. However, the feedstocks must be reduced in size in order to make it a continuous process.

Research efforts in various places have brought in a solution for this problem; the cellulosic biomass consists of the C5 and the C6 sugars. As I said earlier, the problem we are facing at the moment is lesser yield of sugar during hydrolysis. This can be very much increased by first performing a mild process, wherein, only the five-carbon sugars get broken up and then a harsher process, to extract the six-carbon sugars. This solution is still not being widely employed. Research is underway.

The concentrated acid hydrolysis uses comparatively milder temperature and pressure. When compared against the acid-hydrolysis, it yields higher quantities of sugar. The problem here is, the process is extremely slow and research is still underway to find a cost-effective acid-recovery system.

The potential of enzymatic hydrolysis, thermochemical proceses and their bottlenecks faced by them can be obtained from this link. Thus, producing ethanol from cellulosic has a great potential due to the vast availability of the biomass feedstock. However, the routes to cellulosic ethanol are still not techno-economically feasible.

Labels: Acid hydrolysis, biofuel, cellulosic ethanol, energy, Ethanol

Cellulosic Biomass to Ethanol – Iogen Technology

posted by Sumukee @ 3:36 AM | Thursday, September 24, 2009 0 Comments

This post explains the technology employed by Iogen, the world leader in Cellulose Ethanol. I have highlighted the technology employed by this sustainability minded company and the technology they have employed to commercialize cellulosic ethanol.

Generally, the conversion of cellulosic ethanol involves three steps. The technology employed by Iogen has been explained briefly in the preceding paragraphs.

Activation step
Biological conversion
Product recovery

The first step involves converting the raw cellulosic biomass into reactive intermediates. This is either by pretreatment, enzymatic hydrolysis, acid hydrolysis or gasification. Studies reveal that pretreatment and enzymatic hydrolysis serves to be the cheapest method in the activation step.

Companies like Iogen, who are world leaders in cellulose ethanol, have developed an efficient pretreatment method such as steam explosion. This method increases the surface area and the accessibility of the plant fibre to enzymes. This modified steam explosion process has not only improved the ethanol yields over the years but also has increased the pretreatment efficiency as well as reduces the overall cost.

Iogen produces some highly potent and efficient cellulose enzyme systems by themselves and those are tailored to the specific feedstock. This is followed by fermentation. Iogen has also developed reactor systems which have proved to fabricate high productivity and high conversion of cellulose into glucose. They have been able to do through a multi-stage hydrolysis process.

Again, I would like to highlight the fact that companies such as Iogen uses advanced microorganisms and fermentation systems which convert both C6 and C5 sugars to ethanol. This results in what is called “beer”. Further distillation is required to produce cellulose ethanol to be used as a fuel.

The last step involved is the process integration wherein energy efficient heat integration,
water recycling, and co-product production are performed to make the overall process economical as well as efficient.

For those of the scientific bent - Full article

Labels: Acid hydrolysis, Bioenergy Enzymes, cellulosic ethanol, energy, Fermentation