A RICE-HUSK-GAS-FED BAKERY OVEN DEVELOPED FOR SMALLCOTTAGE INDUSTRY USE

by
Alexis Belonio, Emmanuel Sicat, Catherine delos Reyes, Ireneo Agulto, and Francisco Cuaresma
Good news and glory to God!!
Baking in a conventional bakery oven
can now be done using producer gas
from rice husks.  Amid continued
increase in the prices of conventional
fossil fuel, small-cottage bakery
industry can still carry out their
business profitably using the newly
developed continuous-type rice-huskgas-fed oven. This technology is one of
the series of project developments
being done by CRHET-CLSU Rice Husk
Project under the College of
Engineering of Central Luzon State
University at Science City of Munoz,
Nueva Ecija, Philippines. The
Project aims to develop
technologies that utilizes rice
husks as source of fuel to help
small industries cope with the
high cost of fuel while, at the
same time, being
environment-conscious.
The oven, basically, is a boxtype structure commonly used
by Bakers in a small-cottage
industry business. It is made
of galvanized iron with 105-cm x 105-cm inside dimension
and a 50-cm height. The outside casing is made of the same material with a 1.2-m x 1.2-m
The Oven
total dimension and a 0.8-m
height. Inside the oven are
two layers of tray shelves
that can hold 4 to 5 pieces of
standard baking pan (33 cm
x 43 cm) per shelf.  A 2-in.
diameter pipe-type gas
burner indirectly heats the
oven at a temperature of
150C. The combustible gas
used for the oven is supplied
by a 0.3-m diameter
continuous-type rice husk
gasifier equipped with a 2-in.
350-watt, 220-volt electric blower.
Preheating of oven requires about 30 minutes to raise the temperature from 28 to 160C.
Once the temperature reaches 160C, trays of bread are loaded in the oven. A minimum oven
temperature of 140C is maintained throughout the baking period.  The breads are required to
stay inside the oven for 20 minutes.  During the first 10 minutes, trays of bread are loaded in
the lower shelf of the oven, and are subsequently transferred to the upper shelf  which are kept
for another 10 minutes.   The oven has a capacity of 8 to 10 trays per load.  Each tray can
accommodate 24 pieces of “Pandesal,” giving a total of 192 to 288 pieces per load.  In one hour,
it can bake a total of 768 to 960 pieces of
“pandesal.”  Moreover, the amount of
rice husks consumed is 7 to 8 sacks per
hour with an electrical consumption of
0.09 kW in one hour.  The temperature
at the burning zone of the oven, which
was taken directly from the top of the
flame, was measured from 220 to
405C. The gas temperature leaving the
reactor ranges from 172 to 180C.  One
person is needed to attend in the
operation of the oven.  The burning gas at the oven is generally light- blue with pink color and is
almost similar with that of the conventional LPG-gas fired oven.  Smoke emission is almost zero
when proper operation is observed. The char, which is the by-product from burning rice husks,
coming out of the gasifier is 25 to 30% of rice husks input.
Loading the Oven
The Burning Gas from Rice Husk
When operated for 8 hours, a minimum total of 6144
pieces of “Pandesal” for an 8-tray capacity  per day can
be baked. With the investment cost for the oven and
gasifier of P65,000.00, the computed baking cost using 8-tray loading capacity is P44.85 per hour or P 0.06 per
piece of “Pandesal.” Comparing with the current cost of
baking “Pandesal” using LPG of about P1.21 per piece
and considering an 8-hour per day and 20 days per
month operation, the investment for the oven and the
gasifier can be recovered within a period of one month.
Other advantage features of the oven and the gasifier
are:  (1) It is convenient to operate; (2) The gasifier
reactor can be put outside the baking room providing
clean environment during operation; (3) It can also be
operated using LPG, when needed; (4) It can be backedup with 12-volt, 100-amp-hour car or solar battery and
inverter, in case of brown out; (5) It can be built using
local skills and construction materials; and (6 ) the byproduct, which is the char, can be used in the rural areas
for improving the condition of the soil.
For more detailed information, please contact:
Engr. Alexis T. Belonio
Project Director, CRHET-CLSU Rice Husk Project
College of Engineering, Central Luzon State University
Science City of Munoz, Nueva Ecija, Philippines
Email: atbelonio@yahoo.com
We wish to thank ERDT for providing the fund for this project.  The following undergraduate
students of the Agricultural Engineering Department of CLSU College of Engineering, namely:
Genesis Lazo, Marlon delos Santos, Roel Pranilla, and Rafael Domingo who assisted in testing
and evaluating the gasifier oven.
Released: April 2012