Cellulosic Ethanol Showstoppers...

As discussed in the previous posts, cellulose based ethanol have great prospects, however, there are many bottlenecks witnessed to commercialize the production of cellulosic ethanol.

DOE has identified the various barriers witnessed by the cellulosic ethanol industry. These include the economic, sustainability, storage barriers, which have been briefly explained in the preceding paragraphs.

Provided below are the highlights of the bottlenecks faced by the cellulosic ethanol industry:

Summary of the bottlenecks faced by the Cellulosic Ethanol Industry:

1) The enzymes used in cellulosic biomass production are too expensive. The solution for those was produced by certain thermophilic baceteria, but research is still underway to find if they are the best choice for the biomass breakdown.
2) Efforts are still on the way to find robust organisms which can utilise all the sugars even in impure environments.
3) Research is underway to find microorganisms which can aerobically ferment to produce cellulosic ethanol. This will help a great deal in reducing fermentation costs.
4) Removing the impurities generated by fermentation is very expensive.

Bottlenecks related to Cost:

1) Efforts are still underway to commercialize the cellulosic ethanol production and make is economically viable. The pretreatment methods are still expensive and the industry is still in its nascence.
2) Biotechnological research which includes genetic modification makes the investors worry about the risk they might create to the native population.
3) Cellulosic biomass is still expensive due to issues such as transportation, as discussed in my previous post. Also, the biomass feedstock are changeable. For example, unknown quantities of the biomass might be lost to extreme weather.
4) High capital costs are still a big problem faced by the cellulosic ethanol industry.
5) There is yet another problem with ethanol; it costs more than and still gives about 34% lesser energy than gasoline.

Bottlenecks related to Storage:

1) Even if pretreatment is made cheaper, there are some harvesting issues which have to be overcome to enable the large-scale production of cellulosic ethanol. There are still no harvesting machines to harvest the cellulosic biomass.
2) The harvesting machines which are currently available will not be able to handle tons of biomass.
3) There are still issues for storing the wet biomass, which if not properly stored might result in rotting and lead to spoilage, making it unusable.

Bottlenecks related to Preprocessing:

1) To find the best methods or organisms for preprocessing, properties of the biomass must be researched extensively.
2) Apparently, the issues in removing the impurities present in the biomass is posing problems for large-scale production of cellulosic ethanol.
3) These impurities present are removed by employing methods such as grinding, compacting and blending.
4) If these preprocessing steps are not done properly, it might damage the equipment.
5) The harvest season of each cellulosic biomass is different because of which it is a bit difficult to harvest the cellulosic biomass to pre-process them and store them.
6) A multi-step process is required for a enzymatic break-down and this is really expensive. Though many cellulosic ethanol companies are coming up with innovative pre-treatment ideas, no pretreatment method as been confirmed to be entirely economically viable.
7) When these microorganisms or enzymes are added to the fermenter , sterilization is required so as to maintain a sterile environment and to prevent contamination and the issue here is , when batch sterilization is done it might pollute the waterways if the impurities from the equipment is improperly disposed.

For those of the scientific bent - Full article