3rd Africa Rice Congress Theme 3: Rice processing and marketing Mini symposium: Adding value to Africa’s rice: rice-derived products Author: Mbazzi et al.

1. Particle size, drying method, water
temperature and husk-to-bran ratio are
important factors influencing the hardness of
briquettes at constant pressure
S.A. Ndindeng, J.E.G. Mbassi*, M. BihLoh Achu, W.F. Mbacham, J.T. Manful
S.Ndindeng@cgiar.org

2. Introduction
In regions of the world where rice
is produced especially in SSA
countries, poor treatment and
disposal of rice by-products is a
serious problem as this results in
pollution.
Rubber roll mill
In these communities rubber roll
mills are advantageous not only
because they produce better
quality milled rice but also because
they produce separate husk and
bran
De-husking
Polishing

3. Introduction
Rice bran is often used in in SSA countries as an
ingredient in the production of livestock feed.
Recently some authors have pointed out the
possibility of using rice bran as a supplement in the
production of biscuits and cookies (Bunde, 2010;
Yadav, 2011).
BRAN
HUSK
Unlike the bran, rice husk is not used for any
purpose in SSA countries and the huge mounts
behind rice mills is usually set on fire and it burns
slowly as it is produced.
Some authors have indicated the possibility of
using rice husk ash as a partial substitute for
cement (Brown, 2012).

4. Introduction
However, in areas where Engelberg-type mills
are common, the husk is usually mixed with
the bran, making both by-products unsuitable
for livestock feed production.
Briquetting of husk from rubber roll mills and
husk mixed with bran from Engelberg mills for
fuel wood has been suggested as alternative
means to add-value to these by-products
especially for communities that need fuel
wood for other rice processing activities such
as parboiling.
Such a briquetting process must also ensure
that it does not incorporate material in the
briquettes that will render the ash unusable
either as a cement substitute or in ceramics.
De-husking and Polishing
Briquettes

5. Objectives
Overall
To add value to husk and husk mixed with bran through
briquetting to achieve the required hardness and burning
parameters.
Specific
• Produce a briquetting machine
• Use machine to produce briquettes while varying the
following factors:
•
•
•
•
Particle size
Husk : Bran ratio
Water temperature
Drying method
• Measure the hardness of different briquettes

6. Methodology of briquette production
Biomass
collection
Husk
Ratio
Bran
Grinding
Sieving
Water
[Hot = 97 oC]
[Cold = 27oC]
Large, Pore size (mm2) = 2<PS ≤ 67
Medium Pore size = 0,49<PS ≤2
Fine, Pore size = PS ≤ 0,49
Mixing
Briquetting (press)
Drying
Strength analysis on
briquettes
•Open –air
•In the oven (70 C)

7. Results and Discussions
Hydraulic Pump briquetting machine (2
tons)
Lid
Cylindrical tube
Support
Bar
Piston
Pressure pump
Open/closed pump
Lever

8. Results and Discussions
•Influence of proportion of husk and bran on the hardness of briquettes
Drying method= Sun, Drying time = 14 days, water proportion= 1,5, water temp= hot (97°C),
Particle size =fine,
14
More bran leads to
harder briquettes
12
10
8
6
4
2
N=
6
3
3
3
3
1:1
1:2
1:0
0:1
2:1
Ratio of husk to bran
Sokhansanj and co-workers (2005)
identified that feed material
containing higher proportions of
starch and protein will produce
higher quality briquettes than
material high in cellulosic material.

9. Results and Discussions
•Influence of drying method on the hardness of briquettes
Drying time = 7, water proportion= 1,5, water temp= hot, Particle size =fine, Ratio husk to bran=1:1
Sun drying had the best effect on
the hardness of the briquettes.
8.0
7.5
7.0
6.5
6.0
5.5
N=
2
3
Oven and Sun
Sun only
Drying method
Michel and Autio (2001): During
drying, the amylopectin portion of
the starch granule recrystallizes,
and increases the rigidity of starch
gels

10. Results and Discussions
•Influence of temperature of water used for mixture on the hardness
Drying method= Sun, Drying time = 14, Particle size =fine, water proportion= 1,5, Ratio husk to bran=1:1
10
Hot water modifies physico-chemical
properties (gelatinization of starch,
denaturation of protein) and binding
between particles is greatly enhanced
resulting in improved physical
briquettes quality (Thomas et al. 1997)
8
6
4
2
0
N=
6
5
Hot (97)
Cold (27)
Water temp for briquetting (oC)
Warm water influence positively on the hardness of briquettes

11. Results and Discussions
•Influence of Particle size on the hardness of the briquettes
Drying method= Sun, Drying time = 21, water proportion= 1,5, water temp = hot, Ratio husk to bran=1:1
12
11
10
9
8
Fine
7
Medium
Large
6
5
4
N=
3
3
Fine
Medium
Particle size
Mani and co-workers (2003) report
that smaller particle sizes produce
higher density briquettes.

12. Conclusions and Recommendations
• Husk-Bran mixture of 1:1 from Engelberg mills and husk
alone (1:0) from rubber roll mills gave briquettes of
good hardness (7-9 kg).
• The highest hardness were achieved from a combination
of the following factors:
Particle size: Fine (PS ≤ 0,49)
Water temperature: Hot (97°C)
Combination
Drying method: Sun drying/Open air
Drying time: 21 days