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By Cara Mullen

Dynamic action and adaptability accompany propagation--no matter what the species. We are

managing an optimum solution to energy availability in a land almost devoid of woody biomass.

When Haitians went to the woods to gather wood as cooking fuel, their need outpaced the

regenerative ability of the trees to repopulate the mountainous forests. Then with easy access to

abandoned sugar cane fields enterprising farmers gathered what they could to emulate rum

distilling for profit. Consequently, an overpopulated economy marginally supports eight

hundred plus guildives in the production of the native clarin. Clarin, the low-proof distilled

sugar cane beverage averages proof –levels of a number of normally fermented beers.

Within the past decade a number of non-profit organizations invested in a cart before the horse

by committing to fuel ethanol cook stoves to address chronic poor health conditions created by

charcoal and wood-fire cooking. Access to quality ethanol cooking fuel has not been affordable.

And therefore hundreds of ethanol cook stoves remain unused.

Supported by the Inter-American Development Bank, Sustainable Technology Systems, Inc.

(STS) was engaged to evaluate distilled proof levels in existing guildives and to analyze the

steps necessary to convert these small-scale distilling hubs into efficient cooking-fuel production

sites.

There is no argument in nature vs. nurture when discussing yeast necessary to transform sugars

into fuel ethanol. Cooperative control of all production elements is necessary to improve a

viable percentage of alcohol for effective cooking temperatures. The solution rests in the magic

of certain yeast to convert simple sugar into alcohol followed by efficient distillation. Only with

the nature of certain yeast and with proper nurturing can distillers reach their 180 to 190 proof

goals.

Microbiologist, Cara Mullen and distilling technician, Tom Setchel joined Peggy Korth of STS

to investigate optimizing the natural propensity of "the little guy": Saccharomyces cerevisiae or

its close relatives. Over the past few decades, brewer's yeast has been cultured into strains that

are temperature, pH, and alcohol tolerant. By giving these little guys a friendly environment and

the correct dilution of sugar water, they rapidly produce alcohol distilled into high proof alcohol

that is readily transformed into meal preparation. Fuel ethanol heat as energy can supply self-

supportive in energy resources not available in this island culture. Cooking with fuel ethanol

replaces air-polluting charcoal and biomass fires that cause major health-related problems within

the home.

Building with Brix

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Training distillers in technical imperatives and with the use of simple tools, STS team members

gathered data to forward distilling improvement guidelines. Recommendations follow.

1. Return to the earth what comes from the earth. Ameliorate the soil and replant with new

sugar-rich cane stock.

2. Control competitors. Sugar levels (brix readings) drop as much as 25% from cane juicing to

fermentation tanks indicating massive biofilm infection that is robbing the juice flow of sugar.

Re-examining cultures taken from fresh juice to juice storage vats indicated the presence of lactic

acid and glycerol. These invasive bacteria must be removed and kept from re-establishing

colonies in the fermentation system.

3. Temperature controls, pH and sugar levels provide an ideal environment. To keep the natural

temperature profile stable, the fermenters could be covered to optimize anaerobic yeast

production. Fermentation temperature should be between 86 and 96 degrees F.

On site local distillers and

demonstration comparisons

Samples pH SG BX

Sugar juice local 2.0 1.130 7.0

Sugar juice STS 5.0 1.100 5.0

Syrup local 3.0 1.090 25.0

Syrup STS 4.8 1.040 16.0

Recipe for optimum use of sugars: Brix refers to grams of sugar per 100 grams of water or a

ratio of 1:3. By weight 1 cup (8 oz.) of sugar should be diluted by 3.5 cups of water. Because

yeast cannot typically survive in alcohol concentrations above 15 to 18% a maximum Brix of 27

can support yeast turning that sugar into alcohol. Yeast do not have to be inoculated at a certain

ratio because they are living organisms which reproduce in the presence of adequate oxygen.

Typically one gram of yeast is added to one gallon of fermentable liquid.

Disadvantages of a large cell mass—too much yeast: After the stationary phase of

fermentation, the yeast begin to consume glucose for cell maintenance thereby not converting

usable sugars into ethanol. Necessary yeast should be limited to what is needed to complete

fermentation. Cell mass can be reduced by starting with a lower yeast inoculation. Use yeast

cultivated for ethanol production and not baker’s yeast. Keep oxygen levels supportive of yeast

activity.

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Reducing Glycerol Production: Yeast stress produces glycerol. Stress factors are synergistic.

A number of stress factors working together will stress the yeast resulting in ethanol loss. The

biological processes of yeast activity produce glycerol which will inhibit ethanol production by

the yeast. High performance liquid chromatography of local fermentation samples indicated

yeast stress with high glycerol waste levels. Example of evaluation of fermentation action:

Blycerol ratio of 2:1 on a weight basis for every 0.1% w/v glycerol produced translates to a

0.05% w/v ethanol loss.

Osmotic Stress from High Glucose Concentration (Sugar Shock): The yeast used in alcohol

production, Saccharomyces cervisiae, is non-osmotolerant or cannot protect itself in the cell

wall. High levels of glucose stress the cell wall and membrane allowing available glucose to

enter the cell. The physiological response is production of glycerol by the yeast and thereby

causing osmotic stress. The addition of warm water not to exceed 100 degrees obtained from the

distillation process can reduce the sugar concentration. A brix meter is used to measure brix

concentration during fermentation with a target glucose level of 8 to 10% at any given time.

Lower brix levels will stimulate yeast growth. To encourage yeast growth, use a 4% w/v glucose

concentration. The longer yeast is exposed to high concentrations of glucose, the more

detrimental it is to yeast growth.

Moderately High Temperatures in Fermentation: Elevated fermentation temperatures cause

increased yeast activity and a faster rate of fermentation as well as increased glycerol production.

Temperatures should be kept below 90°F and can contribute to combined stress factors.

Maintain temperatures between 86 and 96°F

The final report submitted to the Farmers and Distillers Association explains how to improve all

phases of production quantity and quality. Moreover, the investigative team believes that ideally

an educational program should be instituted to train technicians in basic microbiology and simple

distilling physics. Sustainable Technology Systems, Inc. builds training modules as well as

trouble-shooting existing facilities. A recent publication, Bioenergy Tips for Trials by Cara

Mullen and Peggy Korth offers a procedure guide to small and mid-sized producers to build

systems that can serve as energy resources where ever sugars and starches are available. Contact

iucarabou13@gmailcom for more information.