Butanol Fermentation

CBR's technology partners have been involved in the research of hydrogen production from fermentation processes for over 30 years through the development and application of its Community Bio-Refinery (CBR) applied technologies.  This work has mainly been the result of hydrogen as a by-product of CBR partner’s research and development of its n-butanol fermentation processes where hydrogen and carbon dioxide gases are produced as by-products of the n-butanol fermentation process.  These gases are usually produced in ratios of 45% hydrogen and 55% carbon dioxide with about 30% of the total energy (carbohydrates) going into this gas production.  Under normal fermentation conditions, approximately .6 pounds (6/10th lb) of hydrogen gas is produced per one gallon of butanol fermented.  Essentially, 10% of the energy (carbohydrates) of the n-butanol fermentation process goes into the production of hydrogen, or the hydrogen phase as a by-product.  Since the CBR model intends to produce a minimum of 10 million gallons of n-butanol annually for use in biochemicals or biofuels, this would result in about 6 million pounds of hydrogen gas being produced annually by a CBR.  This production can be accomplished from both primary feedstocks such as high starch grains, e.g. corn, barley, rice, sorghum grains, etc.) or from secondary crop biomass such sweet cane sorghum, corn stover, rice and wheat straw, or cotton stalks, for example.  These feedstocks must be relatively dry if they are to be transported for more than 10 miles.

Hydrogen Fermentation

Part of the technologies developed by CBR are far more efficient continuous flow fermentation processes where CBR has been able to increase the fermentation rates, for example, in ethanol fermentations by 10 fold (reducing the fermentation time from 50 hours to 5 hours), and butanol by 10-20 fold.  CBR believes that these same novel fermentation processes could be used to accomplish the same results for increased hydrogen production.   Since only about 10% of the energy (carbohydrates) content goes towards the production of hydrogen, CBR believes it can “skew” this output to favor hydrogen production.  This could be done by either metabolic or genetic DNA modification of the typical bacteria that produce butanol (clostridial sp.), or preferably, by substitution of special bacteria which produce a hydrogen-rich stream where most of the energy (carbohydrates) goes to the production of hydrogen.  The USDA has developed these types of bacterial species.  If these bacteria or similar bacteria were to be added to the CBR model, much larger volumes of hydrogen could be generated by a CBR, potentially increasing the “hydrogen phase” output by 10 fold.  However, the CBR financial model is highly dependent upon the butanol phase for sustainability.  Therefore, to implement this secondary hydrogen-rich phase will require processing of additional dry tons of secondary crop biomass such as corn stover, cotton stalks, rice straw, or hemp straw, for example, dedicated mostly to the production of hydrogen.  The advantage of this fermentation system, should its fermentation efficiency be proven out in this particular application, is that it could reduce the capital cost to as low as $1-2 million per MWH generated, or less.  Since this system is modular due to the modular fermentation technology to be employed, this system could be scaled up in a graduated mode, probably in 2-5 MWH increments.  CBR plans to initiate this novel fermentation approach during its butanol beta site phase which will be 'adjuncted' to its first Commercial Food MBR plant.  One of the downsides of this technological approach is the cost and preparation of the feedstock and producing a value-added product therefrom.  CBR has developed novel micronization technologies which when applied to biomass grinding will dramatically reduce the cost of processing biomass.  This same technology may also have applications with wet biomass processing.  In addition, the CBR biomass model CBR plans to produce bioplastics to off-set these feedstock costs and the production of these by-products is expected to recover both the feedstock cost itself as well as its hauling and milling costs.  This could make the production of green electrical power from crop biomass a highly attractive method of generating green electrical power for the local community.  The advantage to this technology is that it is modular and can be scaled in increments to almost any size.