Haiti sugarcane processing

1. Maximizing Efficient Sugar Consumption
Minimizing organic acid production
Reducing glycerol production

4. Bacteria
Yeast

5. Bacteria are
Single-celled organisms
which are
Prokaryotes which
Can produce infection
And undesirable
ACIDS and stress to
Yeast.

6.  are a fungi which are
 Eukaryotes
 Yeast turn sugar into alcohol. Yeast have
many different attributes. Some yeast are
better at making alcohol than others

7. Vinegar (acetic acid) is made from ethanol by the
acetic acid bacterium, Acetobacter aceti
Sauerkraut is made by lactic acid bacteria naturally
present on cabbage
Pickles are made essentially by the same process for
sauerkraut with organisms: Leuconostoc and
Pediococcus
Acid is NOT good when Making alcohol

8. Sources of bacterial contamination
 On the feedstock, especially old, wet, or damaged
stalks!
 On the trucks or from the soil
Bacteria are in the water
 Well water, open container water, stagnate water
 Cooling water
Bacteria are in the air
 Higher in warm and humid environments
 Summer time they thrive in moist environments
Bacteria are on your person
 Skin, mouth

9. sugar → ethanol + carbon dioxide + heat
____________________________________________
Anaerobic respiration with lactic acid
formation when invaded by bacteria.
sugar → lactic acid + heat

10. Certain species of bacteria and wild yeast strains live favorably in ethanol
fermentation conditions.
They compete with the yeast and utilize the glucose (simple sugar) and produce
stress chemical called glycerol. Both reducing the amount of ethanol that could
have been produced.
This lowers the ethanol yields and increases undesirable organic acids. Acids kill
the yeast

11.  During fermentation, carbohydrates, ethanol,
and organic acids are monitored in order to
insure that the fermentation process is
occurring normally and to insure that
undesirable bacteria are kept under control.
Also, the mash temperature is kept in a range
of 90F to 95F.

12.  Lactic acid: Lactic acid % starts at 0.05 and
stays mostly steady when lactic acid bacteria
are under control When lactic acid bacteria
are present in larger numbers, the lactic acid
% in Haiti were extremely high ex: 1.8%
 Acetic acid: Acetic acid generally stays in a
range of 0.05 to 0.10.

13.  Bacterial cultures:

14.  Bacterial infections can cause large losses in profit
 Based on ~1% lactic acid growth at 13 wt% ethanol and $2
gal/ethanol
 For example a 250,000 liter ethanol plant infection causes
loss of
1% loss = $1,000 per year
4% loss = $4,000 per year
 1 organic acid molecule = 1 lost ethanol molecule
 1 lactic acid molecule = 1 lost ethanol molecule

15. Glycerol 2:1 on a weight basis; for every 0.1% w/v glycerol
produced, 0.05% w/v ethanol is lost.
Reducing glycerol from a 1.8% to 1.6% w/v theoretically results in
0.1% w/v increase in ethanol.
13.0 → 13.1% w/v increase = ~1,000,000 gal additional EtOH/year
(100,000 MMGY)
800,000 X 16.12% v/v = 128,960 gal EtOH/ferm
800,000 X 16.24% v/v = 129,952 gal EtOH/ferm
~1000 gal EtOH increase per ferm; 3 ferms per day, 360 operating
days per year = 1,080,000 gal additional EtOH produced
 184/92 = 2 ----- Thus glycerol:ethanol is 2:1 by wt

16.  Yeast stress factors are synergistic; while
yeast can tolerate one or two moderate stress
factors, several stress factors working
together will add infinitely more stress to a
yeast culture such as:
 pH
 Temperature
 Ethanol content
 Acid and glycerol content
 Osmotic pressure
 Glucose content
 Salt content from water

17. Glycerol is a waste product
produced by “stressed” yeast. It
sends a signal out to stop working
because the end is near. This
inhibits the yeast from doing their
job.
 Acid affects the yeast by
changing their ideal
environment and not
allowing them to make
alcohol.

18. Practical Application
Keep plant clean and bacteria free
Further Considerations:
 Bacteria consuming sugar isn’t the only concern.
The negative effects of elevated organic acids are
extensive including increased residual sugars,
decreased ethanol, increased stress on yeast.
 If you have a chronic, recurring infection it may be
wise to do some calculations on how much
ethanol potential is lost and what capital
expenditures could be made to alleviate the
source of the issue.

19. Lactic Acid (produced by heterofermentative LAB) is roughly 1:1
on a weight basis; for every 0.1% w/v lactic acid produced, 0.1%
w/v ethanol is lost.
Reducing lactic acid from a 0.4% to 0.2% w/v theoretically
results in 0.2% w/v increase in ethanol.
13.0 → 13.2% w/v increase = ~2,000,000 gal additional
EtOH/year
(100,000 MMGY)
800,000 X 16.12% v/v = 128,960 gal EtOH/ferm
800,000 X 16.37% v/v = 130,944 gal EtOH/ferm
~2000 gal EtOH increase per ferm; 3 ferms per day, 360
operating days per year = 2,160,000 gal additional EtOH
produced

20.  “Reducing lactic acid levels should result in
increased ethanol concentration due to
glucose consumption via yeast rather than
bacteria. Reducing lactic acid from 0.3 to
0.2% w/v
 (0.1% w/v difference) theoretically results in a
gain of ethanol by 0.05 to 0.1% w/v per
fermenter. For a 100-million-gallon/year
ethanol plant, this results in a yearly gain of
1–2 million additional gallons ethanol
produced per year.”
 Phibrochem 2011

21. Lab technicians test
for acids with
instruments to save
money for the
producer
Lactic acid on Hplc
• Lactic acid indicates bacterial
contamination
• Primary source is a (LAB) lactic acid
bacteria

22. for every 0.1% w/v lactic acid produced,
0.1% w/v ethanol is lost.

23. Propagation ? #3
Lactic acid 1.710
Glycerol 2.220
Low glucose
Finished ethanol
Ethanol 99.92
Methanol .0157
DENATURANT type chemicals
.065 which does not include
the acids and glycerols.
 Backwash #1
 Lactic acid 2.274
 Glycerol 2.770
 Backwash #2
 Lactic acid 1.806
 Glycerol 3.240
 Fermentor
 Lactic acid 1.452
 Glycerol 2.832

24. Backwash What this means:
 Dp4 are larger starches
 Still some glucose left
over
 Still some ethanol left
over
 Extremely infected with
Lactic Acid bacteria
produce lactic acid out of
the glucose
 High stress on yeast
which are producing
glycerol instead of
ethanol.
 Peak after glucose is
probably Fructose or
Sucrose which are other
sugars that can be
fermented.

25. Backwash
What this means: Same as
previous
 Dp4 are larger starches
 Still some glucose left over
 Still some ethanol left over
 Extremely infected with
Lactic Acid bacteria produce
lactic acid out of the
glucose
 High stress on yeast which
are producing glycerol
instead of ethanol.
 Peak after glucose is
probably Fructose or
Sucrose which are other
sugars that can be
fermented.

26. Fermentor
What this means:
 Dp4 are larger starches
 Still some glucose left over
 Still some ethanol left over
 Extremely infected with
Lactic Acid bacteria produce
lactic acid out of the
glucose
 High stress on yeast which
are producing glycerol
instead of ethanol.
 Peak after glucose is
probably Fructose or
Sucrose which are other
sugars that can be
fermented.
 Ethanol production can be
higher.

27. Ethanol production What this means:
 Some methanol in
product
 Other contaminants
probably from high
acids
 Not sure if denaturant
had been added

28. Propagation What this means:
 Dp4 are larger starches
 Still some glucose left over
 Still some ethanol left over
 Extremely infected with
Lactic Acid bacteria produce
lactic acid out of the
glucose
 High stress on yeast which
are producing glycerol
instead of ethanol.
 Peak after glucose is
probably Fructose or
Sucrose which are other
sugars that can be
fermented.
 Ethanol production should
be lower in the prop to
avoid high glycerol.

32. Sugar holding well Dirty processing

33. Sugar trough Resolution

34. Prop needs cover Fermenters need covers

35. Stainless steel and pvc
piping
Plastic tanks

36.  Ethanol producing yeast
 Power washers and sanitation from STS
 PVC piping
 Washable stainless steel and tanks
 Use distillate water to clean with
 Washable milling equipment
 Better tanks for fermentation
 Use briquettes from coconut or bagasse for heat
 Heat efficient broilers
 Enzyme, nutrient, and STS conditioner, STS yeast trial
 Hydrometers, Refractometers and pH meters/paper
 New clean buckets and method to clean them
 New presses for briquettes
 New distillation equipment
 Head space improvement to cookstoves
 Use of other available waste for feedstock