of the Philippines.
It is produced by converting freshly
harvested coco sap into syrup by boiling
and allowing it to become crystal through
constant mixing and kneading.
Boiling coco sap to evaporate water is
one of the costly and intensive activity
during the process in coco sugar
production.
Forty liters of cocosap requires about 2 to
3 hours of heating and boiling before it
can be turned into syrup and crystal
sugar.
About 1.4 kilograms of LPG is needed to
produce 1 kg of sugar.
Although fuel wood can be used as an
alternative fuel for boiling coco sap, the
erratic heating using wood fuel usually
affects the quality of the sugar produced.
Rice husks, which is highly abundant in
the Philippines, can be utilized as
alternative fuel for coco sugar processing.
Gasifying rice husks can provide low cost
and quality fuel for boiling coco sap.
Annually, about 2 million metric tons of
rice husks is available.
Ways of disposing rice husks is still a
common problem.
Metric Tons
Converting rice husks into gaseous fuel is a
practical and proper way of disposing them,
at the same time, making use of the energy
available.
A kilogram of rice husks can provide around
1.2 m
3
gaseous fuel with heat content of
1,400 kcal.
With the recent development on rice husk
gasifiers, boiling coco sap can now be done
cheaper with better quality as compared
with the traditional burning of biomass which
is difficult to control and produces a lot of
smoke during operation.
The Rice Husk Gasifier Stove
A rice husk gasifier stove produces heat
energy for cooking, boiling, or heating
through the process of gasification.
It converts rice husks into combustible
gas in an oxygen-starve environment and
produces a luminous blue-to-pink flame,
which is almost similar to that of an LPG.
The gas produced is rich in carbon
monoxide (CO), hydrogen (H
2
), and
methane (CH
4
).
The intensity of burning the gaseous fuel
in the stove can be finely controlled.
No smoke during operation
CO
2
and black carbon emission are very
low as compared with that of the
conventional fuel sources.
One person is needed to operate the
rice husk gas stove – that is, to load rice
husks, to discharge the char, and to
oversee the entire operation.
One person can operate four units of the
gasifier stove at one time.
The extent of firing can be controlled
using a switch and a control valve.
One person can
manage the
operation of the
stove.
One batch of 40
liters of coco sap
(12-18 Brix) can
produce around 5
to 6 kilograms of
sugar.
Advantages of the Gasifier Stove
Clean gas is obtained from burning rice
husks.
• Almost no smoke during operation
• CO
2
emission is significantly reduced
(around 0.6 kg CO
2
per kg of rice husk
• Black carbon emission is very low (equal
or less than 50 ug/m
3
) .
The gas obtained from rice husk stove can
be used to supply the heat needed for
boiling coco sap.
The stove is efficient since the heat energy
produced from the reactor is delivered to
the gas burner with very minimal heat
losses.
The amount of energy released by the
gasifier can be easily controlled attaining
a uniform heating during operation.
The energy needed to produce gas is
very minimal, at about less than 5% of the
heat output.
Investment and operating costs per unit
power output are much lower compared
with that of the conventional stoves.
By-product can be utilized in agriculture
for conditioning and for improving the
water holding capacity of the soil.
It can also be used as ingredient for
making pelleted fuel and for the
production of locally-mixed construction
material.
Limitations of the stove
An air-moving device is needed to
generate the required amount of air for
gasifying rice husks.
Power source is needed to run the fan.
Highly fuel-selective to be able to
produce quality and uniform supply of
gas throughout the operation.
Skill and thorough understanding of the
process are required in order to properly
operate the gasifier .
Safety must be ensured since the gas is
highly combustible and injurious to
health when inhaled.
By-product of the stove
The by-product of
the gasifier , which is
char, is used as
source of
carbonized rice
husks to improve
the fertility of the
soil, to increase the
water holding
capacity of the soil,
and to enhance
bacterial
decomposition in
the soil.
Increased in Weight
Time (min x 10)
Water Holding Capacity of Char Compared with
Rice Husk and Charcoal
Char
Rice Husk
Wood Charcoal
BY -PRODUCT UTILIZATION
The char produced can
also be used as an
ingredient in the
production of biomass
pellet to fuel the stove.
The ash, which is
derived from burning
the char further can be
used as an ingredient
in making low-cost
refractory cement and
in producing cementfiber board and
geopolymer blocks for
light construction.
OPE
OPERATING COST AND PAYBACK PERIOD
The rice husk gasifier stove is around
Php150,000.00 per unit, excluding
transport and/or shipment.
The cost to operate the stove is P30.17
per hour, Php2.01 per liter of coco sap
or Php 14.08 per kg of sugar.
The investment for the stove can be
recovered within a little more than 5
months, as compared with LPG stove.
CONCLUDING REMARKS
The rice husk gasifier stove can be
considered a good alternative cooking
device for coco sugar production.
It can boil and convert coco sap into syrup
and crystal similar to that boiled in LPG
and wood stoves.
The operation of the stove can be easily
controlled using a switch and a valve .
Compared with LPG, the investment for
the stove can be recovered within half a
year.
Gasified rice husks can be further
utilized in agriculture and industrial
applications, particularly in improving
the fertility of the soil, as an ingredient in
the production of cement-fiber board,
refractory cement, and geopolymer .
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