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Biomass Briquettes in Malawi
Olle Faxälv Olof Nyström
Division of Energy Systems
Degree Project
Department of Management and Engineering LIU-IEI-TEK-A--07/00129--SE
Minor Field Study MFS-report nr 103 ISSN 1400-3562
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Abstract In Malawi 2.5 % of the forest disappears each year. The use of firewood and charcoal, deriving
from forest resources, accounts for about 99 % of the household energy demand in Malawi and is a
cause to the deforestation. The Government of Malawi recently launched a programme called
Promotion of Alternative Energy Sources Programme (PAESP) with the aim to reduce the use of
firewood and charcoal. One of the fuels included in the programme is the biomass briquette. The
aim with this study is to evaluate the viability of biomass briquettes as a sustainable alternative
energy source to firewood and charcoal for households in Malawi.
Research for the study was carried out during three months in Malawi. Visits were made to a
number of briquette production sites to study the manufacturing methods and to collect briquette
samples. The briquettes were tested using various methods and then compared with results for
firewood and charcoal.
At the moment various production methods are used in Malawi, with a high difference in technical
complexity and cost. Machines produced from wood using very basic mechanics can apply similar
pressure as more advanced metal pressers. They also seem to be better suited than those made of
metal, in terms of price and availability.
The majority of the briquette producers in Malawi use waste paper as base material. Although the
paper briquettes are good, other raw materials will be needed if the production is supposed to be
significantly increased.
The briquettes burn well using the most common stoves in Malawi, including the commonly used
charcoal stove. While firewood is cheaper to use than other available fuels, the briquettes seem to
be able to compete with the fuel costs for charcoal.
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Sammanfattning I Malawi försvinner 2.5 % av skogen varje år. Användningen av ved och träkol, som kommer från
skogstillgångarna, står för runt 99 % av hushållsenergi användningen och det orsakar avskogning.
Regeringen i Malawi har nyligen introducerat ett åtgärdsprogram som heter Promotion of
Alternative Energy Sources Programme (PAESP) med syftet att minska användningen av ved och
träkol. Ett av bränslena som ingår i programmet är biomassabriketter. Målet med det här arbetet är
att utvärdera biomassabriketten som en hållbar alternativ energikälla till ved och träkol för hushåll i
Malawi.
Utvärderingen för det här arbetet gjordes under tre månader i Malawi. Flera ställen där briketter
producerades besöktes för att studera tillverkningsmetoder och samla ihop olika briketter.
Briketterna provades genom olika metoder och jämfördes sedan med ved och träkol.
I dagsläget används flera olika produktionsmetoder i Malawi, med stora skillnader i hur tekniskt
avancerade och kostsamma de är. Maskiner producerade från trä med enkla mekaniska lösningar
kan producera samma presskrafter som mer avancerade stålpressar. De verkar även lämpligare än
de gjorda i stål, vad gäller pris och tillgänglighet.
Merparten av producenterna i Malawi använder återvinningspapper som utgångsmaterial. Även om
pappersbriketterna är bra, så kommer andra material behöva användas om produktionen ska öka
betydligt.
Briketterna brinner bra i de populäraste spisarna i Malawi, inklusive den välanvända träkolspisen.
Medan ved är billigare att använda än andra tillgångliga bränslen så verkar det som att briketter kan
konkurrera med bränslekostnaderna för träkol.
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Acknowledgements We would like to thank everybody who helped us through our work, especially:
Mats Söderström
-For supervising our work
Dr. Charles Kafumba and the staff on Department of Energy Affairs in Malawi
-Making it possible to carry out with the thesis and supervision
Per Lindskog and Kenneth Nyasulu
-Mediate contacts
Annie Kamanga
-Helping us in the various tests
Kyle and Amy Guerrero
-Great accommodation and minibus service
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Acronyms 3SF Three-Stone Open Fire
CCS Charcoal Ceramic Stove
CCT Controlled Cooking Test
CEEDS Centre for Energy, Environment and Development Studies
CWAG Chembe Women's Aquaculture Group
DoE Malawi Department of Energy Affairs
FWS Firewood Ceramic Stove
GoM Government of Malawi
HHT Household Test
LPG Liquefied Petroleum Gas
MK Malawi Kwacha
MASEDA Malawi Socio-Economic Database
MEP Malawi Energy Policy
MWBT Modified Water Boiling Test
NGO Non-Governmental Organization
PAESP Promotion of Alternative Energy Sources Programme
PAMET Paper Making Education Trust
ProBEC Programme for Biomass Energy Conservation
SIDA Swedish International Development Agency
WBT Water Boiling Test
WESMA Wildlife and Environmental Society of Malawi
WICO Wood Industry Corporation of Malawi
WWF World Wide Fund for Nature
Exchange rates of currencies, 2006-12-31:
1 EUR = 190 MK
1 SEK = 20 MK
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Table of contents
1 Introduction....................................................................................................................................... 1 1.1 Problem Statement .................................................................................................................... 1 1.2 Aim............................................................................................................................................ 3 1.3 Study Boundaries ...................................................................................................................... 3 1.4 Method ...................................................................................................................................... 3
1.4.1 Visits at production sites ................................................................................................... 4 1.4.2 Testing of briquettes .......................................................................................................... 4
1.5 Constraints................................................................................................................................. 5 2 Frame of Reference........................................................................................................................... 7
2.1 Household Energy in Malawi.................................................................................................... 7 2.1.1 Cooking Stoves.................................................................................................................. 8
2.1.1.1 3-stone open fire ........................................................................................................ 8 2.1.1.2 Improved Ceramic Stoves.......................................................................................... 9
2.2 Biomass Briquettes.................................................................................................................. 10 2.2.1 Raw materials .................................................................................................................. 10 2.2.2 Shapes.............................................................................................................................. 11 2.2.3 Briquette burning............................................................................................................. 11
2.2.3.1 Airflow..................................................................................................................... 11 2.2.3.2 Ash Removal............................................................................................................ 12 2.2.3.3 Positioning in fire..................................................................................................... 12
2.3 Briquette Production ............................................................................................................... 12 2.3.1 Raw Material Collection.................................................................................................. 13 2.3.2 Material Processing ......................................................................................................... 13 2.3.3 Pressing............................................................................................................................ 13
2.3.3.1 WU-Presser .............................................................................................................. 14 2.3.3.2 Screw presser ........................................................................................................... 15 2.3.3.3 Hand pressed............................................................................................................ 16 2.3.3.4 Heated die screw press............................................................................................. 16
2.3.4 Drying.............................................................................................................................. 17 3 The visited production sites and their briquettes ............................................................................ 19
3.1 Department of Energy ............................................................................................................. 19 3.2 Orphanage in Ndirande, Blantyre............................................................................................ 20 3.3 PAMET, Blantyre.................................................................................................................... 21 3.4 WESMA, Lilongwe................................................................................................................. 23
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3.5 MIRTDC, Blantyre.................................................................................................................. 24 3.6 Nordin Family, Chitedze ......................................................................................................... 26 3.7 CWAG, Cape Maclear ............................................................................................................ 27 3.8 WICO, Blantyre ...................................................................................................................... 30
4 Tests ................................................................................................................................................ 33 4.1 Water Boiling Test .................................................................................................................. 33
4.1.1 Method............................................................................................................................. 33 4.1.1.1 Modified Water Boiling Test ................................................................................... 33
4.1.2 Realization....................................................................................................................... 35 4.1.2.1 The WBT for comparing the fuels ........................................................................... 36 4.1.2.2 The WBT for comparing stoves............................................................................... 37
4.1.3 Results ............................................................................................................................. 37 4.1.4 Sources of Error............................................................................................................... 38 4.1.5 Analysis ........................................................................................................................... 39
4.1.5.1 Fuels......................................................................................................................... 39 4.1.4.2 Stoves....................................................................................................................... 42
4.2 Controlled Cooking Test ......................................................................................................... 44 4.2.1 Method............................................................................................................................. 44 4.2.2 Realization....................................................................................................................... 44 4.2.3 Results ............................................................................................................................. 45
4.2.3.1 Sources of Error ....................................................................................................... 46 4.2.4 Analysis ........................................................................................................................... 46
4.3 Household Test........................................................................................................................ 49 4.3.1 Method............................................................................................................................. 49 4.3.2 The Household................................................................................................................. 49 4.3.3 Realization....................................................................................................................... 50 4.3.4 Results ............................................................................................................................. 50 4.3.5 Analysis ........................................................................................................................... 50
5 Discussion ....................................................................................................................................... 53 5.1 What makes a good briquette? ................................................................................................ 53 5.2 What presser to use?................................................................................................................ 54 5.3 The market for briquettes ........................................................................................................ 55
6 Conclusion ...................................................................................................................................... 57 7 Proposal to further work ................................................................................................................. 59 8 References....................................................................................................................................... 61 9 Appendices...................................................................................................................................... 63
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List of Tables
Table 1: Efficiency of cooking stoves..................................................................................................8
Table 2: Fuels and stoves in MWBT .................................................................................................37
Table 4. Results for comparing stoves from WBT ............................................................................38
Table 5: Energy results from the tests compared with the theoretical values....................................43
Table 7: Average values of the results gained from the CCT............................................................47
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1 Introduction
”By the year 2020, Malawi, as a God-fearing nation, will be secure, democratically mature,
environmentally sustainable, self-reliant with equal opportunities for active participation by all,
having social services, vibrant cultural and religious values and a technologically driven middle
income country”.
This vision was announced by the former president of Malawi, Dr. Bakili Muluzi, in March 1998. It
is understandable why the president find a sustainable environment to be important for Malawi,
since about 90 % of the energy used in the country derive from forest resources. (MEP, 2003)
Unfortunately the handling of forests in Malawi is not sustainable today. Every year 2.5 % of the
total forest in Malawi disappears according to government statistics (MASEDA, 2002). The reasons
are various, but the extensive use of forest as resource for providing firewood and charcoal, is one
of them.
Malawi is one of the poorest countries in the world, with 65 % of the population living on less than
US$1 a day (MEP, 2003). The industrial sector in Malawi is small and the country's energy is
almost exclusively used in households. Hence a situation where the forest is disappearing mainly
affects the ability for households to meet their energy needs, which is most commonly spent on
cooking.
The deforestation also causes increased amounts of silt in rivers creating seasonal dry ups, trouble
for hydro power generation, and occasional flash floods, which threaten lives and infrastructure in
the riverbanks. Furthermore it leads to sedimentation in lakes which threatens the biodiversity of
fishes (MEP, 2003).
1.1 Problem Statement
The problem in Malawi is a misuse of the existing energy resources. If new more efficient methods
to use the energy could be found the energy situation could be sustainable and the deforestation
problem could be ameliorated.
For cooking, the major part of the population use firewood on an open fire, with a low efficiency.
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The main reason why firewood is not more efficiently used is that the fuel can be collected for free
by most Malawians. The charcoal production today is another example of how the energy is used in
an inefficient way. Most of the charcoal in Malawi is produced with traditional charcoal
carbonization technologies with a proven efficiency of about 10 %. The production of charcoal is an
easy income source for producers, there is no need for investments or an economical capital to start
producing charcoal. For the households charcoal is also a relatively convenient fuel since there is no
need for advanced stoves or equipment to use it.
The Government of Malawi (GoM) has tried to take control over the charcoal production but never
really succeeded. Laws and legislations have been introduced in order to reduce the environmental
impact that is related to the charcoal production. Hence a licence is needed to produce charcoal
legally. At present there is no producer in the country that has this licence. One of the major
problems with these laws and regulations is that there are no alternative income sources to offer the
illegal charcoal producers. At the moment it is also difficult for the households to find alternative
energy sources on the market that can compete with the availability of charcoal.
The lack of capital among most households in Malawi makes it difficult to move from using either
firewood or charcoal, to more advanced energy sources where even small initial investments must
be made, for buying for example more advanced stoves or burners. Hence the substitute to these
fuels needs to require a minimal capital investment, be as cheap and accessible as charcoal and
firewood are, and at the same time be environmentally sustainable.
In order to fight the deforestation and reduce the dependence of the forest as a resource for energy,
the Department of Energy (DoE) in Malawi launched a project called ”Promotion of Alternative
Energy Sources Programme” (PAESP) in the year 2006. The aim of this project is to encourage the
use of energy sources other than firewood and charcoal.
One of several alternative energy sources considered in this project is the biomass briquette (see
illustration 1). Other alternatives include the biogas, Liquefied Petroleum Gas (LPG), ethanol and
gel-fuel technologies. It is though evident that none of these latter alternatives can compete with the
biomass briquette, in terms of the low capital investment that is required to use it.
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Illustration 1: A typical biomass briquette made of compressed paper and sawdust.
An evaluation study about this fuel was carried out in Malawi the year 2000 (CEEDS, Biomass
Briquette Extension, Production and Marketing), and then proved it to be a cheap alternative to
both firewood and charcoal. Since some of the conditions for the biomass briquettes may have
changed during the past six years, a new evaluation is needed to update on the information and thus
validate whether this situation still obtains. That leads us to the aim of this thesis.
1.2 Aim
The aim of this study is to evaluate the viability of biomass briquettes as a sustainable alternative
energy source to firewood and charcoal for households in Malawi.
1.3 Study Boundaries
The briquette evaluation will be made in terms of physical and chemical characteristics (like
material content, size, weight, energy content), costs for the fuel and usability in household cooking
stoves. The feasibility of the production method for each briquette type will also be evaluated. The
briquettes will be compared with the characteristics of firewood and charcoal. This report does not
include an evaluation of the social obstacles related to the use of biomass briquettes in households.
It neither includes an elaborate market research or how the supply could meet the demand for
biomass briquettes in Malawi.
1.4 Method
To carry out this study a journey was made to do field studies in Malawi for 3 months, partly
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financed by the Minor Field Study scholarship, given by the Swedish International Development
Agency (SIDA). The study has been made with support by the DoE in Malawi.
1.4.1 Visits at production sites
To get knowledge about the current status of the briquette production in Malawi visits to various
manufacturers was done. The selection of places to visit was mainly done with help from the
Department of Energy. During those visits an official from the DoE was always present. Visits
made without the assistance of DoE was made at WESMA in Lilongwe and the Nordin family in
the village Chitedze. At each site persons responsible for the production were interviewed about the
briquette making activities and the used facilities were then seen. From each producer that was
visited briquettes were collected to be examined further. At some sites the production was not
running anymore, for various reasons, but every site had samples to give us anyway, although some
of them might have been old.
1.4.2 Testing of briquettes
In order to make a statement about the briquettes as an energy source several tests were carried out.
The various tests were made over a period of about two months and the necessary equipment was
borrowed from ProBEC, based in Mulanje.
The performance of the briquette types was compared among themselves and with firewood and
charcoal. All the tests were made in a firewood cooking stove (FWS) except the charcoal where a
charcoal stove (CCS) was used. The FWS was recommended for burning the briquettes by CEED
(2000). The test made at this stage was a modified water boiling test (MWBT).
Performance comparisons for the different stoves were also carried out. The stoves tested were a 3-
stone fire, a FWS and a CCS. The fuels used for comparison in these tests were paper briquettes
from PAMET, softwood and charcoal. The same MWBT as in the fuel testing was applied for the
stove testing.
To make the comparison between briquettes, charcoal and firewood more complete, a Controlled
Cooking Test (CCT) was made for each fuel. A meal consisting of nsima and vegetables was
prepared by a local woman on a FWS and a CCS. The briquettes used in this phase were the ones
made by the DoE.
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Furthermore, one household was asked to use briquettes for cooking, in order to evaluate how user
friendly they are and if there are any practical obstacles connected to the use of briquettes in the
household. The testing lasted a week and the briquettes used during this time were produced by
WESMA.
1.5 Constraints
The limited amount of available briquette samples from the producers affected the amount of tests
that could be made. To assure the results of the tests (it is considered that) every test should be
repeated at least three times. This is something that was not always possible, due to the lack of
available fuel. The majority of the briquettes were collected in the Blantyre area, which is a few
hours drive from Lilongwe, where the tests was made.
The weather might have affected the results of the tests. Wind and temperature were not constant
throughout all the tests, although a lot of effort was made to make the tests in sheltered environment
to minimize the chances for the wind to influence the heat transfer from stove to pot. The tests were
carried out during the months of November and December. This year the rainy season started
approximately in early December, which brought cooler temperatures and moister air compared to
the previous month. Most of the WBT was made in November before the rain, but all the CCT were
made in December at the same time each day.
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2 Frame of Reference
2.1 Household Energy in Malawi
As seen in the second pie chart in Diagram 1, the household sector accounts for over 80 % of the
energy demand in Malawi. 99 % of the energy used by this sector is coming from biomass energy
sources (the remaining 1 % comes mainly from electricity and paraffin). Approximately 4 % of the
households have access to electricity.
Diagram 1: Energy consumption in Malawi displayed by source and end-user. (World Bank,1996)
About 85 % of the Malawi population, consisting of 12 million
inhabitants, live in rural areas. The urban population is mostly
found in the four biggest cities; Blantyre and Lilongwe (country
capital), both having about 500'000 inhabitants each, and the
smaller Zomba and Mzuzu, with populations of around 100'000
each. A map of Malawi with the biggest cities is shown in
illustration 2.
In rural households almost exclusively firewood is used, when
cooking. The firewood is normally taken from trees on the
farmland or in the nearby forests, for free.
In urban areas most of the firewood users collect the wood from
nearby trees for free, while about half of them sometimes buy
firewood. The firewood is normally sold in street markets.
Illustration 2: Map of Malawi,
showing the locations of the four
biggest cities: Lilongwe, Blantyre,
Zomba and Mzuzu.(CIA,2006)
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For the urban households that have to buy their fuel, an alternative to firewood is charcoal. Charcoal
is made in earth kilns in rural areas and is sold in the cities, where the demand for fuel is high. The
charcoal is a more convenient fuel in a way, since it has got a higher heat value (J/kg) than firewood
and less smoke emissions, once it has started glowing. On the other hand, the price of charcoal is
normally higher than the price of firewood (counted in money spent per meal). Therefore the fuel is
mostly used by middle- to upper-income households. (World Bank, 2005)
The charcoal is almost exclusively made from hardwood, taken from indigenous forest. The GoM
has tried to promote softwood charcoal, made from planted pine trees, but since the quality of this
charcoal is not as good as the former alternative, households still buys the hardwood-based
charcoal. The kilns where the charcoal is made are inefficient. To produce one ton of charcoal 7
tonnes of firewood is needed. (GoM, 2003)
2.1.1 Cooking Stoves
There are several cooking stoves that can be used for biomass energy in Malawi. The most simple,
and affordable one is the 3-stone open fire. Other alternatives are the ceramic stoves. Those are
more expensive to buy but they cook with better efficiency. The efficiencies of the three most
common stoves are shown in Table1.
End use device Efficiency
3-Stone Fire 10 %-14 % Firewood Cooking devices
Improved Fire Wood Ceramic stove 20 %
Charcoal Cooking Devices Improved Charcoal Ceramic stove 35 %
Table 1: Efficiency of cooking stoves. (MEP, 2003)
2.1.1.1 3-stone open fire
In African countries the 3-stone open fire (3SF) is widely
used for cooking with firewood (see illustration 3). In
Malawi 91 % of the urban firewood-using households
prepare their meals on this open fire, according to the
Malawi Energy Policy (GoM, 2003).
Illustration 3: 3 stone open fire
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The stove consists of three stones placed on the ground, forming the edges of something like a
triangle, which holds the pot a decimetre or two above the ground. Underneath the pot firewood is
pushed in from different angles. The “stove” is inefficient, since much heat is lost to the
surrounding environment. The advantage of this cooking device is that it is free and easily
assembled (you just need three stones).
2.1.1.2 Improved Ceramic Stoves
One way of decreasing the use of biomass energy for cooking is to change the end use device. If
more efficient stoves are used, less fuel is needed to cook the same amount of fuel. Therefore the
DoE has been recommending ceramic stoves to the public. These stoves are made from recycled
metal, and are lined with about 3 cm of clay on the inside. The clay insulates the combustion
chamber against the environment (although some of the heat is absorbed by the material) and hence
more heat is transferred to the pot. The stoves are sometimes given the epithet “improved” because
they are a better version of the older and simpler metal stoves (without the clay lining).
The charcoal and firewood have different burning characteristics and the stoves need to have a
suitable design for each fuel. While firewood transfers most of the heat by convection through the
flames, charcoal transfers heat by radiation. When charcoal is used for cooking the fuel should be
placed close to the pot to get the most efficient transfer of heat radiation. On the other hand, the
firewood needs some space above the fuel for the hot flames. Hence the pot needs to be placed at a
higher level when firewood is used, comparing to when charcoal is used. The designs of the ceramic
stoves are displayed in illustration 4.
Illustration 4: Firewood ceramic stove and charcoal ceramic stove.
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The firewood stove also has a shape that demands an opening (with or without hatch) where the
firewood sticks can be pushed into the fire. (Interview with Andi Michel)
The charcoal ceramic stove (CCS) is the most common stove to use in Malawi and other African
countries when burning charcoal, while few households use the FWS when burning firewood.
Although the FWS is not close to being used as much as the 3SF, the stove is interesting in this
study, since the Department of Energy is promoting this stove for firewood users.
2.2 Biomass Briquettes
The biomass briquette is a fuel, consisting of biomass, such as agricultural waste or waste paper,
bound together and compressed into small pieces (approximately 5 to 15 cm). The fuel complies
with the energy needs for poor households in developing countries, where firewood and charcoal is
normally used. Briquettes are very seldom used in Malawi today. There are few producers in the
country and the fuel is hard to find for consumers. If nothing else is stated, the information about
biomass briquettes in this chapter is based upon facts found in the book Fuel Briquettes: Theory
and Applications from around the World (2003), written by Richard Stanley for the Legacy
Foundation.
Richard Stanley has a lot of experience in briquette production and he has got great knowledge
about briquettes. Richard Stanley has also tried to introduce biomass briquettes as a household fuel
in Malawi a few years ago.
2.2.1 Raw materials
A lot of different materials can be used for briquette making, for example agricultural residues like
ground nut shells, straw, tree leaves, grass, rice and maize husks and banana leaves. It is also
possible to use already processed materials such as paper, saw dust and charcoal fines. Although
some materials burn better than others, the selection of raw material is usually most dependent on
what is easily available in the surrounding areas of where the briquettes are made. Of course a
briquette can consist of a blend between many different raw materials.
The inflammability is not the only thing that matters when the raw material is being selected.
Another important characteristic is its ability to bond together, when compressed. For these reasons
fibre-rich materials are good. When these materials are soaked in water and partly decomposed, the
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fibres in the material are able to create strong bonds.
The calorific value of a basic paper/sawdust briquette will be around 15 MJ/kg. This value will of
course differ depending on the selection of raw materials. It can be compared to firewood that is
around 16 MJ/kg (dependent on moisture content) and Charcoal around 30 MJ/kg (CEEDS). These
values should not be confused with the energy gained from the briquette when burned in different
stoves.
2.2.2 Shapes
The size of the briquette has an influence on in which stove that it can be used, since it must be able
to fit into the combustion chamber. The most common type of briquette is the so called doughnut
shaped one. It has got a cylindrical shape with a hole in the middle. If burned properly, the central
hole increases the combustion efficiency of the briquette, states the Legacy Foundation. In order to
make these briquettes a presser is needed. The diameter of the briquettes is affected by which
pressing equipment that is used, but usually they measure between 10 and 15 cm.
In Low Input Food and Nutrition Security: growing and eating more using less (World Food
Programme, 2005) the author Stacia Nordin describes a way to make paper-based briquettes
without the use of pressing equipment or tools. Paper that has been soaked for about half a day is
squeezed by hand in shapes of balls or similar. The balls are then left to dry in 1-3 days, before they
are ready for use.
In the section called ”Briquette Production” further below, the briquette pressing is described in
greater detail.
2.2.3 Briquette burning
Below the most important theories about briquette burning is described. Richard Stanley states that
there are three important factors that affect the fire when briquettes are used. Those are air flow, ash
removal and positioning of the briquettes in the stove.
2.2.3.1 Airflow
Good airflow is critical for the burning of briquettes, as for other fuels. The optimal fire is reached
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when the airflow comes from underneath the fuel. Insufficient air flow will result in a smoky fire,
since the released volatile gases will not be completely combusted.
2.2.3.2 Ash Removal
The briquettes produce more ash than both firewood and charcoal. This can cause a problem in
some stoves, where the air holes can get clogged, which affects the airflow. Legacy Foundation
claims that the air holes in the bottom of a stove needs to have at least 1.5 inches (~37 mm)
diameter, to be suitable for briquettes. The charcoal and firewood ceramic stoves do not comply
with this rule since their air holes only have a diameter of about 0.75 inches. When using briquettes
in a 3-stone open fire, extra tendering may be needed to remove ashes from the fire under the pot.
2.2.3.3 Positioning in fire
The positioning of the briquettes in the stove influences the burning characteristics. The briquettes
can either be burnt just like they are, or they can be broken into smaller pieces. The former method
is considered to make the combustion more long-lived, but less intense than the latter, although the
ignition of the briquette is made more difficult.
If the briquettes are burned without tearing them apart, doughnut shaped briquettes should be placed
in an upright position (i.e. having the inner hole facing upwards). This helps the air to pass through
the central hole in the cylinder, which makes the combustion much more efficient, states the Legacy
Foundation. The reason for the higher efficiency is because the radiant energy from the burning
material is facing inwards, and not out from the fire. This characteristic makes the briquettes
suitable in stoves with low efficiency, since the impact of the heat losses are greater in those cases.
The hole also creates a draft through the central hole, similar to that of a chimney, which gives a
clear path for good air-flow from underneath the briquette.
2.3 Briquette Production
The making of briquettes is divided in four main steps, as described in the manual Fuel Briquettes:
a Users Manual (Legacy foundation, 2003).
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2.3.1 Raw Material Collection
As said before, a lot of different ingredients can be used for briquette making. Burnable, fibre-rich
material that is both available nearby and that can be taken free of charge is preferably selected. The
manual labour required for the collection of material will then be the only related cost for getting
hold of raw material.
2.3.2 Material Processing
To make briquettes the raw material should be pressed together, but before this, the material has to
be prepared. The preparation is necessary to release and distribute the fibres in the material. This
makes the materials more susceptible to bond when compressed in the presser.
The organic matter, like agricultural residues, first needs to be chopped or pounded into smaller
pieces in dry condition. Then it should be left to partially decompose in order to loosen up the
structure of the material. How long time the decomposition takes varies and depends on the material
and the climate. After the different materials have been decomposed properly they should be soaked
in water and blended. This makes the fibres to randomly distribute in the sludgy matter that is
created.
If the briquettes are to be made out of waste paper the preparing process is different, and much
easier. The paper must be soaked in water for about half a day, or more, and then it should be
shredded and pounded into small pieces. When this is done the material is ready to be pressed into
briquettes.
The pounding of raw material, whenever it is necessary during the preparations, are the most
laborious and time consuming phase in the production chain. The pounding is usually made using
large mortars and pestles (about ~1.5m tall).
2.3.3 Pressing
For the material to be de-watered and to bond, it is necessary to submit it to pressure. The method
of pressing will affect the final shape and burning characteristics of the briquette. A higher density
gives the briquette a higher heat value (J/kg), and makes the briquette burn more slowly.
The most common type of the briquettes is the cylindrical shaped, often with a centre hole
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(doughnut shape). To press this type of briquette it is necessary to use a cylindrical mould, most
commonly a perforated tube of PVC, placed in upright position. In the centre a metal piston can be
placed which enables the making of a hollow shaped doughnut briquette. The tube is then filled
with raw material. The raw material in the cylinder is then
compressed by descending a disc or a solid cylinder that just fits
in the PVC tube.. Water, blended in the raw material, leaves the
tube through the perforated holes during the compressing phase.
An example of this equipment is shown in illustration 5.
When compressing the briquette the compression of raw
materials requires a non linear force to distance1. There are
different ways of applying the force for pressing cylindrical
shaped briquettes. Two common technologies are explained
below.
2.3.3.1 WU-Presser
The WU-presser was developed by the Washington University more than ten years ago. It is
constructed from either metal or wooden parts. The wooden version has been seen in Malawi at
least since 1997 (illustration 6).
Illustration 6: A wooden WU-press in Malawi.
1 When the disc first starts forcing the raw material to compress downwards, the first centimetre travelled by the disc
needs a lower amount of work (since the raw material in the tube contains a lot of air and water that is easy to
squeeze), if compared to the work that is necessary during the last centimetre of the pressing movement.
Illustration 5: Mould kit for making
doughnut briquettes
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15
There are a few reasons why the wooden version grew popular. Wood is a cheaper material and
more available than metal in Malawi and because of the lack of financial means in the country the
wooden press had the economical advantage. Another reason was the high availability of skilled
manpower for producing in wood. (CEED, 2000)
Illustration 7: How to use the WU-presser.(Legacy Foundation, 2003)
The WU presser is pressing the briquette in three steps described in illustration 7. Each step will
press with increasing pressure. This takes advantage of the non linear force to distance property of
briquette pressing described earlier.
2.3.3.2 Screw presser
The screw pressers also make briquettes in upright cylinders. The raw material is compressed by
lowering a metal disc which is moved vertically by a screw that is turned by hand. The disc moves
approximately 1cm/rev, with a constant exchange ratio of the force. The screwing technology is
powerful and becomes handy in the final compression stage where it is able to contribute fully with
its advantages of a good exchange ratio of forces.
The screw press is most commonly made in metal. This makes it sturdy but often quite expensive.
Richard Stanley, who is promoting the WU-press press through Legacy Foundation, claims that a
press using screwing parts is not suitable for an environment where briquettes are made, since there
is too much of granular and wet material around that may cause damages on the screw threads.
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Illustration 8: Instruction paper on how to
make hand pressed paper briquettes. (Art by
Kristof Nordin,2005)
2.3.3.3 Hand pressed
As Stacia Nordin claims in “Low Input Food and Nutrition
Security: growing and eating more using less” (World Food
Programme, 2005) the briquettes can be pressed by hand,
using waste paper as raw material. This method does not
require any use of pressing equipment or tools, which
makes it cheap and available to everybody. The method is
though explained only for making paper-based briquettes,
and not for using agricultural residues. Illustration 8 is the
instruction of how to make these briquettes from the book.
2.3.3.4 Heated die screw press
The heated die screw press is an industrialized machine for
producing briquettes. It uses the natures own binder, lignin.
When heating up the biomass to 300°C the lignin melts and
when cooled down again it stiffens and the briquette will get
the desired shape.
In illustration 9 a principal sketch of a heated die briquetting machine is shown. In the funnel (1) the
biomass is gathered. It drops down on the screw (3), which is driven by an electrical engine (4).
The screw presses the biomass into
the die (2). Along the die there are
grooves to prevent the biomass to
rotate with the screw. The die is
electrically heated and heats up the
biomass to 300°C so that the lignin
melts. The briquette is extruded (5)
and chopped off in desired length.
The briquette will be hollow and have
a pyrolyzed surface from the heating.
Some machines heat up the biomass before it goes into the screw. This decreases the wear on the
screw and die. To a small extent it saves the energy needed for rotating the screw.
Illustration 9:Simple sketch of a heated die scew press
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Besides the cost of the investment the machine also has a cost for the electricity consumed. Another
cost is the screw that gets worn and has to bee replaced frequently.
2.3.4 Drying
After the briquettes are made they have to be left to dry, usually between 3 and 8 days. The number
of days depends on the weather conditions, during the dry season it is a lot quicker.
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3 The visited production sites and their briquettes
In the following chapter all the visited briquette producer are described, based on observations and
interviews at the production sites. The briquettes produced at each site are described with a picture
and some basic physical facts. The pressure stated is from brief calculations found in appendix 4.
3.1 Department of Energy
Raw materials: Paper, sawdust
Press: Stanlink
Shape: Doughnut
Outer diameter: 100 mm
Inner diameter: 26 mm
Height: 48 mm
Weight: 117 g
Density: 0.36 kg/dm3
Pressing pressure: 1.7 MPa
Comments: Made by staff at the DoE for
marketing and demonstration
purpose.
Department of Energy has made briquettes for exhibition and marketing purposes. Those are made
using the wooden WU-presser. DoE has several such pressers at the BARREM office in the
outskirts of Lilongwe. The briquettes made by the DoE were stored at the ProBEC office in
Mulanje. The briquettes consist of waste paper and sawdust.
During a visit to the BARREM office some briquettes were made together with staff from the DoE.
The purpose of the visit was to get an idea of the briquette making process. Briquettes were made
from paper and different additives.
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3.2 Orphanage in Ndirande, Blantyre
Raw materials: Paper, sawdust
Press: Stanlink (without iron
piston)
Shape: Cylindrical
Outer diameter: 100 mm
Height: 70 mm
Weight: 163 g
Density: 0.30 kg/dm3
Price: Only produced for own use
Comments: Slightly irregular shape in
between the briquettes
In the township of Ndirande in Blantyre disabled people make briquettes at an orphanage. The
briquettes are made for own use only, and are not sold to the public. A wooden WU-presser is used.
The piston has been missing, so the briquettes can not be made in a doughnut shape as intended,
instead they are solid. The machine is only used once a week. This is enough for covering the
demand of briquettes that they have. Raw materials used are paper waste and sawdust that is
transported to the site for free. Initially the briquette production at this site started with help form
the Nkhomano Development Centre. There is apparently no communication between the orphanage
and Nkhomano anymore, the reason is unclear.
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3.3 PAMET, Blantyre
Raw materials: Paper, sludge from Unilever
(residue oil from food
processing)
Press: Screw press
Shape: Doughnut
Outer diameter: 150 mm
Inner diameter: 56 mm
Height: 50 mm
Weight: 295 g
Density: 0.39 kg/dm3
Pressing pressure: 1.8 Mpa
Price: 5 MK
Comments: Bad smell from the sludge
The non-profit organization Paper Making Education Trust (PAMET), based in central Blantyre,
developed in the 90's a press based on the screw technology. The press is made from metal parts
that are bolted together. The machine costs 28'000 MK (of which the mould contribute the costs
8'000 MK). The press uses one mould, where two
briquettes can be made at the same time, using a
divider plate. See illustration 10 of the presser in use.
The briquettes at PAMET are made of waste paper,
coming mainly from the Blantyre Print and Packaging
(BPP). Sometimes PAMET has to drive and fetch the
waste. The waste is being used both to produce
recycled paper and to produce briquettes. According
to PAMET there is an increasing demand for waste
paper in Blantyre, from different stakeholders. Some
paper is even being exported on trucks to Zimbabwe
and Mozambique, for industrial recycling.
Also some small amount of sludge (containing oil) is
added to the waste paper, to increase the combustion Illustration 10: Screwpresser in use at PAMET
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performance. This sludge is delivered free of charge from Unilever in Blantyre, where the sludge
comes out as a by-product form this food industry. The sludge was kept in a bucket and did not
seem to be very pleasant to work with, since it is greasy and containing a mix of unidentified
ingredients.
The organization has one person employed for producing briquettes. This person produces about
100 briquettes per day. The demand is increasing so Moses Binali, executive director for PAMET,
is considering employing another person for extending the briquette production.
Normally the waste paper is collected about once a week, and stored at PAMET. In the afternoon
the employee soaks the wastepaper that he is going to use for briquette production the day after.
Next morning he pounds the waste paper and then he uses the presser to produce briquettes from the
pounded material.
The briquettes are sold in the township of Chilomoni in Blantyre. PAMET delivers the briquettes
with a vehicle to the salesmen in this township. Some briquettes are also sold at the PAMET office
in Blantyre. Briquettes sold by PAMET to the end consumer are sold for 5 MK/each, whereas they
are sold to the salesmen in Chilomoni for 3 MK/each. At the moment 3 persons are selling
briquettes for them. PAMET is not producing briquettes for making profit, but for marketing the
product, as an alternative energy source to charcoal and firewood. Sometimes PAMET hosts
marketing events of the briquettes in townships around Blantyre. They demonstrate how easy it is to
cook beans, talk about how clean the briquettes are and try to explain the whole situation of the
deforestation and how it is caused by firewood. The event lasts for a day.
It should take no more than four PAMET briquettes to make nsima for a normal household, says
Moses Binali.
PAMET has trained a number of women in briquette manufacturing and a few years ago there was
production running by women groups (with support from NGO's and church groups) in different
parts of Blantyre, but today Moses Binali does not know of anybody who is still making briquettes,
apart from PAMET itself. According to him, the reason is the increasing difficulty of collecting
waste paper, especially in the rural areas. If there is no raw material to be found, the production can
not continue. PAMET sold a few pressers to the women groups which were trained by them. The
presser that is sold is a smaller version of the one used by PAMET.
Moses also claims that the waste paper in Blantyre is not by any means enough for producing
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briquettes for the whole Blantyre region.
PAMET is an organization financed by NGO's. They do try to make profit so that it would be
economically sustainable if the NGO's would retract their funds. The incomes are generated from
selling recycled paper and briquettes.
3.4 WESMA, Lilongwe
Raw materials: Paper
Press: Screw press
Shape: Doughnut shape
Outer diameter: 100 mm
Height: 70 mm
Weight: 163 g
Density: 0.3 kg/dm3
Pressing pressure: 1.1 MPa
Price: 20 MK for a bundle of four
briquettes
Comments: Irregular shape in between
the briquettes
A few years ago Wild Life and Environmental Society of Malawi (WESMA) started a briquette
production project at the National Sanctuary in Lilongwe. Staff from WESMA made a visit to
PAMET in Blantyre to learn about briquette making. WESMA also bought a presser (the same that
PAMET uses today) through PAMET, for the production.2
Raw material for the production at WESMA was office paper, given by offices in City Centre. The
paper was dumped free of charge by companies or NGO's, at the National Sanctuary, where it was
stored in two containers. The briquettes were sold in street markets in Lilongwe, and at the
WESMA office in the Natural Sanctuary.
Around “one year” ago, the responsibility of the production was given over to two persons
employed by WESMA. The people made briquettes, but there started to be a problem with the
2 Except for the presser from PAMET, that was bought for a few thousand MK, WESMA was also given a presser as a donation from some person. This machine is a screw press, and looks really durable, but has not been used
at any time.
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market. There were more briquettes produced, than what could be sold. So the persons were then
given also the responsibility to market the briquettes that they produced. For some reason this was
not very easy, so after a few months the two employed briquette makers resigned. Instead of
shutting down the production, WESMA gave a group of ten women the opportunity to use their
facilities for producing briquettes. The women made briquettes for a few months, until the
production stopped about one month ago. The reason given for the stop was that they could not find
any market for the briquettes.
Today there is no production at WESMA in the Natural Sanctuary. All the facilities are there, but
nobody is using them. There is a storage room filled with hundreds of paper briquettes that were
made before. The containers for raw materials are still there, with quite a lot of paper in them. The
presser that was bought through PAMET is partially broken. The machine can still be used,
although the joint between the screw and the pressing disc is broken. (George Bokosi, 2006)
3.5 MIRTDC, Blantyre
Raw materials: Paper, sludge from Unilever
(residue oil from food
processing)
Press: MIRTDC screw press
Shape: Doughnut shape
Outer diameter: 150 mm
Inner diameter: 60 mm
Height: 53 mm
Weight: 330 g
Density: 0.42 kg/dm3
Pressing pressure: 1.6 MPa
Comments: Very hard packed, Bad smell
from the sludge.
The Malawi Industrial Research and Technology Development Centre (MIRTDC), in Blantyre,
together with some other organizations, developed a new press which was ready for the market in
1999. This project started in 1998, hoping to be able to construct a presser that could make 20
briquettes at the time, instead of only one, as did the older pressers. It was then discovered that the
force applied for pressing such amount of briquettes in one move was too big.
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The final version of the MIRTDC press that came out on the
market can make 12 briquettes at the same time, using 6
cylinders, each producing 2 briquettes. See illustration 9 of the
press. The force on the cylinders is applied by lowering a metal
disc that squeezes the raw materials in all the 6 cylinders at the
same time, instead of just working on one cylinder which is
most common. The metal disc is moved up and down by
screwing. The crank handle is tube shaped, which makes it
possible to locate a rod (like a strong broom stick or similar) to
get more leverage, when needed. The machine consists of
welded metal parts, and is made in Blantyre, after design
drawings from MIRTDC. MIRTDC sells the machine for 40'000
MK. MIRTDC says that the only buyers of this machine have
been NGO's. MIRTDC hopes that the presser could be
developed to be constructed using different, less expensive,
materials.
Since MIRTDC did not present any record of the buyers of this product, it was not possible to find
any users of the machine. MIRTDC though offered to test the exhibition machine in the MIRTDC
shop. Raw materials brought from PAMET, consisting of paper and sludge, were used when trying
to produce briquettes using the MIRTDC machine. With manual force the screw was turned,
pressing the briquettes. Unfortunately, the machine did not support the forces applied, so the
construction broke in one of the weldings. It is worth mentioning that a 2 meter lever was used to
turn the crank handle with two persons operating it at the same time. A person from the MIRTDC
claimed that the machine that broke was not constructed correctly, that it did not fulfil the
specification of requirements.
Illustration 11: The MIRTDC press demonstrated at their shop in Blantyre.
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3.6 Nordin Family, Chitedze
Raw materials: Paper
Press: By hand
Shape: Spherical
Outer diameter: 70 mm
Height: 48 mm
Weight: 93 g
Density: 0.52 kg/dm3
Comments: Irregular shape
Kristof and Stacia Nordin lives in the village Chitedze, 20 km outside of Lilongwe. They are
working under a program called Never Ending Food. At their home in Chitedze and in their work
they are promoting permaculture. Permaculture is a type of sustainable agriculture on the natures
own conditions. It enables the farmers to harvest food all year around and cultivate their land
without ruining fertility of the soil. In their work they have created the “The Low Input Food and
Nutrition Security manual”, that is all about a more sustainable living. It contains information about
anything between agriculture and what food contains the necessary nutrients. One part of this
manual is about making paper briquettes from office waste paper. In their instructions they soak the
paper overnight and then, without pounding or shredding, pressed by hand into balls the next day.
They are then left to dry for 1-3 days. The briquettes are used for cooking during power failures or
for heating on a Charcoal Ceramic Stove. Similar briquettes have been made by ourselves (the
authors) at home using both office paper and newspaper.
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3.7 CWAG, Cape Maclear
Raw materials: Leaves
Press: WWF hand press
Shape: Doughnut shape
Outer diameter: 144 mm
Inner diameter: 50 mm
Height: 50 mm
Weight: 186 g
Density: 0.36 kg/dm3
Price: 2.50 MK
Comments: Very fragile, falls apart very
easily
Raw materials: Corn stalks
Press: WWF Hand press
Shape: doughnut shape
Outer diameter: 144 mm
Inner diameter: 50 mm
Height: 50 mm
Weight: 133 g
Density: 0.36 kg/dm3
Price: 2.50 MK
Comments: -
The production at Panda Garden in Cape Maclear is done by Chembe Women's Aquaculture Group
(CWAG), under the support of the following stakeholders:
● HEED – Malawi
● WWF – Finland
● Rotary Limbe Club
● Rotary District
● Department of National Parks
● Department of Fisheries
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Close to the national park is the WWF headquarter situated. Here is
also where the WWF started up the briquette project year 2003. The
organization then developed the equipment, which can be made by
people in Monkey Bay. The presser consists of metal parts and
produces doughnut shaped briquettes. Instead of using a perforated
PVC tube for the mould, a non-perforated metal cylinder is used.
The raw material is compressed using a metal plate, a smaller
cylinder and a handle that is pushed down with hand power (see
illustration 12). The metal plate is slightly smaller than the bigger
metal cylinder, which enables the water in the raw material to
escape on top of the plate.
The headquarter does still produce briquettes today, but the
briquettes are only made to supply the staff at the WWF. The site
has since 2003 served as an educational centre for people who want
to learn how to make briquettes. In Cape Maclear they today have 56 women working with
briquette production, in different sites in the village. Since the equipment is so light you can
conveniently keep it in your household. Today the centre has taught people from a number of
villages in the Mangochi area and even one from Blantyre. At the moment briquettes are produced
in four different villages in the Mangochi district, using the methods that were taught at the Panda
Garden. The 56 women in Cape Maclear, who are working with briquette production, are divided in
5 groups. Each group, containing about 10 people, work together with the production. They then
share the profit between themselves. A woman can make between 100 to 150 briquettes a day. The
briquettes are sold at the price 2.50 MK, which means that a woman working in production can
make a profit of about 250 MK per day.
The briquettes are either produced only by corn stalks or by leaves. Sometimes they add grass or
paper. Paper burns well but is expensive. The materials are collected from the surrounding areas,
free of charge. They are mixed with water in a basin for about 3 days. Then they are left to
decompose for 2 to 3 weeks, depending on the material. The corn stalks takes about 1 week more
time to decompose compared to the leaves. The decomposition makes the pounding easier, and
makes the briquettes easier to compress, in the presser. When the material has decomposed, it will
be pounded. This takes a lot of time and work. After this, the briquettes are made with the pressing
procedure. After the pressing, the briquettes are left to dry in the sun or the shade (during the rainy
season). The drying takes about 4 to 5 days, but in the rainy season it takes about 10 days.
Illustration 12:The WWF designed
briquette press used in Cape
Maclear.
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In Cape Maclear briquettes are used just as much as firewood, claims Lois Chembe. This is due to
the deforestation problems that this area faces. The last twenty years a lot of forest has disappeared,
and the people living in Cape Maclear has to go far to collect firewood. According to Lois Chembe
it is not unusual that women spend their whole day on collecting firewood, since the transport is
done by feet and the wood is collected far up in the mountains. Before people used to pay the entry
fee for the adjacent national park (10 MK) and then collect as much firewood as possible and then
return to the village. This is illegal and the park guards now watches more carefully over its visitors.
Since it is so laborious to get firewood the prices for the fuel is high in the village. Normally you
will have to pay about the double price per useful energy unit for firewood than for briquettes,
according to Lois Chembe. The briquettes are sold for 2.50 MK a piece. Usually you will have to
use about two or three briquettes to make nsima for a household, depending on the size of the
family. The briquette is more poplar during rainy season, since the firewood in the forest is wet
then.
One household completely depending on briquettes as fuel for meeting their energy demand will
spend between 10 and 20 briquettes per day, or even more if the family is big.
One problem that the women in Cape Maclear face is that there is not enough market for the
briquettes in the village. They could easily increase production, but there is no demand for this
today. Then they must be transported to other villages, and this is not convenient.
People that are interested in briquette production can visit the site in Cape Maclear to learn how to
make the briquettes, free of charge. If they are interested to start up a new production site, they can
then apply for getting subsidies, for paying the equipment needed.
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3.8 WICO, Blantyre
Raw materials: Sawdust
Press: Die-heated screw-
press briquetting
machine
Shape: Cylindrical with an
inner hole
Outer diameter: 58 mm
Inner diameter: 20 mm
Height: 400 mm
Weight: 931 g
Density: 1.16 kg/dm3
Price: 40 MK
Comments: Hard and heavy with a
burnt surface. Inside the
hole there was dirt/ash
on our samples.
The Wood Industry Corporation of Malawi (WICO) has several sawmills in Malawi. One of them is
situated in Dedza. The facility has a briquetting machine that produces briquettes form sawdust.
The machine has been running periodically from 1984. The last time it was running was about 6
months ago. WICO bought the presser for a subsidized price from Japan. From the beginning it
produced 500 kg briquettes per day. This number has now been reduced to 300 kg. The total
amount of sawdust produced every day is about 5 tonnes in Dedza. WICO also has saw mills in
other parts of Malawi, e.g. in Zomba, where the mountain of sawdust is even bigger, according to
Aman Kunje, working at WICO.
The machine that has been used is driven by electricity, and produces a continuous briquette, which
is then manually broken into parts, each with the weight about one kilogram. The sawdust is hold
together thanks to a process where the briquette is heated on the outside, which makes a strong
shell.
The reasons why the machine is not in use today are various. One is that there is some part of the
equipment missing. Another is that the increasing demand of timber has made the manager
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concentrating only on the main activity: timber production. One other reason is that the market for
briquettes at the moment is not reliable. Aman Kunje thinks that it still is difficult to compete with
the charcoal prices. He though thinks that if a more effective briquette machine is introduced to
produce briquettes from all the WICO sawdust, it could be more profitable, if there is proof of a
market to rely on.
WICO's briquettes consist of 100 % sawdust from their own production sites. WICO has tried to
blend the sawdust with cassava and maize husk to get better briquettes, but it was not worth the
effort. The briquette will last for a month if it is kept in normal humidity, after that it will fall apart.
This is one of the major problems with the briquette, that it is not possible to store it for a longer
period of time. It is possible to keep it longer if it is stored in dry conditions. The consumers then
refer to charcoal that can be stored for a long time without problems.
They have sold the briquettes on the market for personal use. The tea industry has been interested in
buying the briquettes but the demand could not be satisfied with WICO's small production capacity.
The price for the briquettes has risen from 5 MK to 40 MK due to the increasing electricity prices
and inflation. WICO claims that there is no possibility to invest in a new briquette press and make a
profit, due to the low prices of charcoal.
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4 Tests
4.1 Water Boiling Test
What is interesting concerning the energy content of a briquette is how much of the energy in the
briquette that can actually be used. The useful energy is the energy transferred into the pot that is
used while cooking. If the same test is performed on each briquette and on firewood and charcoal, a
good comparison can be made. The test is called the Water Boiling Test and it will be used for
comparing:
• The briquettes with each other
• The briquettes with firewood and charcoal
• The briquettes performance on the most common stoves in Malawi.
4.1.1 Method
Stove developers around the world have developed a standardized water boiling test (WBT) to help
them in their work. This existing test, found in appendix 1, focus on comparing the efficiency of
different stoves. The WBT consists of three phases:
• High power test with cold start
• High power test with hot start
• Simmering test The high power test measures the time and fuel it takes for bringing a certain amount of water to
boil, first by using a cold stove and then a hot stove. The simmering test measures the amount of
fuel it takes to keep the water simmering for 45 minutes. It is very versatile but it takes quite a bit of
time to perform each test. Because of limited time, supply of briquettes and the fact that the focus of
the WBT is set on stove performance, a modified water boiling test (MWBT) was needed.
4.1.1.1 Modified Water Boiling Test
The information that is wanted from the MWBT is:
• How quick can the fuel bring the water to boil?
• How much energy is transferred into the water relative the amount of fuel consumed?
• Other notations (smoke, ease of ignition etc.)
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To save time and fuel the two last phases in the original WBT (high power test with hot start and
simmering test) were combined and the 45 minutes for simmering was reduced to 15 minutes in the
MWBT. The specific time of 15 minutes is approximately the time it takes to cook the most
common food in Malawi, nsima. The time limitation makes the test closer to a true scenario. In the
beginning of the MWBT, when the water is brought to boil, a lid is used on the pot, but once the
water starts to boil the lid is taken off. The stove testers around the world still discuss if the test
should be performed with or without the lid for various reasons, but to take the lid off reminds more
of the real scenario when cooking nsima (because the need of stirring) and will therefore be used in
this test. The first phase of the WBT (test on cold-started stove) is not very necessary since it tells
more about the heat capacity of the stove than the characteristics of the specific fuel.
The WBT is designed to be suitable for comparing stove-tests that has been performed in various
parts of the world where moisture content of the fuels may differ a lot. Hence this difference should
be taken into account, so it does not affect the results in the original WBT. In the WBT the moisture
content of each fuel should be measured before using them for testing. The value is then used for
calculating the energy that is needed to vaporize this moist during the test. The calculated amount of
energy is then subtracted from the total energy that has been used in the test. Since the testing
included in this report is made to compare fuels during a limited time period (3 months) and for a
limited geographical area (Malawi), the moisture content for the fuels was not considered very
important. The true performance of a fuel is partly dependent on its moisture content and therefore
its effect should not be subtracted from the results.
The time recorded to bring the water to boil is from the moment the fuel catches fire until the
temperature of the water reaches local boiling point, and the lid is taken off. To prevent the use of
too much fuel to bring the water to boil faster, an aim is set to immediately keep the water
simmering and not heavily boiling after the lid is taken off.
The amount of energy that is transferred to the water will be calculated by measuring the increased
water temperature and the amount of water disappeared from the pot during the test. The energy
will be compared to the weight of the used fuel. This measure (J/kg) will be referred to as ‘utilized
energy’ from now on. The procedure for calculating this is described in appendix 4.
After the test, the remaining fuel in the stove will be weighed to calculate how much of that fuel
that was not combusted. This will be measured because of the limited experience of burning each
type of briquettes. It can be hard to know exactly how much fuel to put into the stove, something
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that the consumer will learn in a few weeks.
The briquettes will produce quite a lot of ash (CEEDS 2000), therefore a formula for calculating the
proportion unused fuel and ash is developed. The formula is found in appendix 4. The ash produced
from a fully combusted briquette will be measured at the end of the testing sessions, when it will be
possible to leave the briquettes in the stove until they are fully combusted.
Every specific test shall be performed at least three times, unless there is a lack of fuel or other
practical obstacles. Three times is the number recommended in the original WBT.
The exact procedure that is set up for the MWBT is found in Appendix 2.
4.1.2 Realization
The equipment used in the
testing was a thermometer, a
scale, and the stoves. This
equipment is listed and
described in Appendix 6. The
thermometer was inserted in
the middle of the pot and the
water through a small hole in
the lid. The testing equipment
that was used is shown in
illustration 13. For each test 20
g of softwood twigs were used
to start the fire. To start the
charcoal 30 g was needed
because it is a fuel that is
harder to ignite. The amount of
twigs needed was decided by
trial and error. The testing took place in a backyard of a house in Area 6 and one in Area 43,
Lilongwe.
Illustration 13: Laboratory equipment for the MWBT
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4.1.2.1 The WBT for comparing the fuels
The following briquettes were tested. They are all collected by us and they have different
characteristics in one way or another:
● Paper and sawdust briquette from DoE
● Paper briquette from orphanage in Ndirande
● Paper briquette from PAMET
● Paper briquette from WESMA
● Paper briquette from MIRTDC
● Leaf briquette from CWAG
● Corn stalk briquette from CWAG
● Paper briquette from the Nordin family in Chitedze
● Sawdust briquette from WICO
To get the reference to the woodfuel these were also tested:
● Softwood
● Hardwood
● Charcoal
Briquettes and firewood were tested on a firewood ceramic stove, but for the charcoal tests it would
not be fair to use that stove, since the design is not suited for charcoal burning. Instead a charcoal
ceramic stove was used, which is very similar to the firewood ceramic stove, but constructed for
charcoal use.
The briquettes from CWAG were impossible to complete a whole test with. They produced too
much smoke to be able to stay close to the stove for tendering. When they burned they produced a
big amount of ash, which filled up the stove and clogged the air holes. A decision was made to
interrupt these tests for health reasons.
The briquettes from the Nordin’s were not burning very well. They seemed slightly heavier then the
other briquettes which the calculated density confirms. High moisture content was suspected as a
possible reason and it was needed to control. To control the moisture content the briquettes were put
into an oven at 70°C to vaporize the water. They stayed in the stove until there was no weight loss
from them. The briquettes from Nordin’s turned out to have a moisture content of about 18 %,
which can be compared to the moisture contents of briquettes made by DoE and WESMA, that
measured less than 6 %.
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4.1.2.2 The WBT for comparing stoves
For the comparison of stoves, the WBT was performed in the same way as for the fuel testing. The
Firewood and charcoal were only tested on the stove produced for the specific fuel, while the
briquettes were tested on all three stoves. The scheme over the testing is illustrated in table 2.
During the end of the stove testing phase the charcoal stove broke so it had to be replaced. The new
CCS was similar design but 1kg (~20 %) heavier. They were bought from different producers.
PAMET briquettes were used because it seemed like an average briquette concerning size and
burning characteristics. It was also one of the briquettes where a surplus existed.
Firewood stove Charcoal stove 3 stone fire
Briquettes from PAMET X X X
Softwood X - X
Charcoal - X -
Table 2: A table of which fuels where tested on which stove during the stove testing in the MWBT
4.1.3 Results
The results are presented in the table below. This is a summary of all the results gained from the
test. The full table of results is found in appendix 7. Some test has been declared invalid for various
reasons. In a few tests the wind picked up and the losses from the pot were considered too big.
Another reason was that there were too much or not enough water vaporized, this indicates that the
water has not been simmering, respectively it has been boiling too hard. The failed tests are also
documented in appendix 7 but in Italic. The reason why they are made invalid is described in the
bottom of the column.
A general notation when doing the test was that the more compact briquettes did not need the same
tendering. They burned for a longer time without any need to put more fuel into the stove.
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MWBT Fuels
Fuel Softwood Hardwood Charcoal DoE Ndirande Energy per weight unit (kJ/g) 5,1 3,7 7,3 3,6 3,1
Weight of used fuel (g) 253 366 194 426 456
Time until boiling (min,s) 15.27 12.55 17.42 10.45 14.15
Price per mass unit (MK/kg) 12,70 10,75 32,68 N/A N/A
Price per energy unit (MK/MJ) 2,50 2,93 4,46 N/A N/A
Density (kg/dm3) - - - 0,36 0,30
Number of tests 4 4 6 1 4
Fuel PAMET WESMA MIRTDC Nordins WICO Energy per weight unit (kJ/g) 3,8 3,4 4,9 2,7 5,3
Weight of used fuel (g) 371 376 305 413 282
Time until boiling (min,s) 12.45 12.57 10.51 15.53 11.50
Price per mass unit (MK/kg) 16,96 23,52 N/A N/A 36,90
Price per energy unit (MK/MJ) 4,48 6,99 N/A N/A 6,94
Density (kg/dm3) 0,30 0,40 0,42 0,52 0,40
Number of tests 2 3 4 2 1
Table 3:Results for comparing fuels from WBT
MWBT Stoves
Stove 3SF 3SF FWS FWS CCS CCS Fuel Softwood PAMET Softwood PAMET Charcoal PAMET Energy per weight unit (kJ/g) 3,0 2,5 5,1 3,8 7,3 4,7
Weight of used fuel (g) 448 508 253 371 194 288
Time until boiling (min,s) 12.40 14.32 15.27 12.45 17.42 12.40
Price per mass unit (MK/kg) 12,70 16,96 12,70 16,96 32,68 16,96
Price per energy unit (MK/MJ) 4,25 6,86 2,50 4,48 4,46 3,58
Number of tests 2 2 4 2 6 2
Table 4. Results for comparing stoves from WBT
4.1.4 Sources of Error
It was hard to simulate exactly the same conditions for each test. The most disturbing factor was the
weather conditions. When the testing started it was in the end of the dry season. Warm winds with
dry air are typical for the dry season. The wind made the testing impossible a few times. It increased
the heat transfer to the surrounding environment (losses) and made it hard to keep the water
simmering. This resulted in remarkably low energy values. At the end of the testing period the rain
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39
season started with a few rains. The rains probably increased the humidity of the air. Unfortunately
there was no available equipment to measure the humidity.
In the MWBT the stoves should be hot started each time. The definition of hot start was to wait for
no more or less than 10 minutes between the finish of one test and the starting of another. Since the
hot stove was defined by a time parameter more than a certain temperature, it is possible that there
might have been some differences in starting temperatures of the stoves, depending on how much
heat that was conserved from the fire in the preceding test.
The way that the briquettes were burnt in the stoves may have affected the outcome of the tests in
some way. Because of the size differences, it was not possible to burn the large diameter briquettes
(WESMA, PAMET, MIRTDC) in the FWS without first breaking them into smaller pieces. The
size of the combustion chamber was simply too small to fit them inside.
4.1.5 Analysis
4.1.5.1 Fuels
At the production sites visited, the producers never had to pay for the raw materials. The production
costs they have are the handling of the raw materials and the work for pressing. This makes the unit
kJ/g most suitable for the comparison concerning energy, since the costs then mostly depends on
the amount of raw material. These results are shown in Diagram 2.
MWBT Fuels - Results(Best f irst)
0,0 2,0 4,0 6,0 8,0
Nordins
Ndirande
WESMA
DoE
Hardw ood
PAMET
MIRTDC
Sof tw ood
WICO
Charcoal
Energy perweight unit(kJ/g)
Diagram 2: Results from the MWBT for comparing fuels.
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40
Sludge? – MIRTDC and PAMET
In the briquettes from MIRTDC and PAMET the same raw material was used, they use plain paper
but add the oily sludge from UniLever. The WESMA briquette has the same shape and density as
MIRTDC. The big difference is the Sludge. According to the test results the sludge seems to
increase the utilized energy of the briquette.
The difference between PAMET and the MIRTDC is the density, which indicates a higher level of
compaction rate. The MIRTDC briquette has the higher level of energy, which indicates that the
higher compaction increases utilized energy. The densities for these briquettes together with the rest
of the briquettes are shown in Diagram 3.
MWBT Fuels - Results(Best f irst)
0 0,1 0,2 0,3 0,4 0,5 0,6
Ndirande
PAMET
DoE
WESMA
WICO
MIRTDC
Nordins
Density(kg/dm3)
Diagram 3: The measured densities of the briquettes used in the MWBT
The bad smoke and a smelly briquette is a comment from most of the test with the briquettes that
has the sludge.
Paper or Sawdust? – WICO and WESMA
WICO and WESMA have the same density. WICO is from pure sawdust and WESMA is from
paper. The WICO briquette gets a higher amount of utilized energy from these two. This indicates
that the sawdust has higher calorific value.
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41
Pressure and sawdust? – WESMA, Ndirande and DoE
The factors that differentiate the briquettes made by WESMA, Ndirande and DoE from each other
are the density (pressure) and the sawdust content. When looking at the utilized energy for these
three briquettes, the conclusions gained above are confirmed. Higher pressure and sawdust gives
higher utilized energy.
In general it seems like the briquettes makes the water boil faster than both charcoal and firewood,
see diagram 4.
MWBT Fuels - Results(Best f irst)
00.00 07.12 14.24 21.36
Charcoal
Nordins
Sof tw ood
Ndirande
WESMA
Hardw ood
PAMET
WICO
MIRTDC
DoE
Time untilboiling(min,s)
Diagram 4: Times needed to bring the water to the local boiling point in the MWBT
Price?
Since most of the briquettes in the test are not sold in the open market it is hard to say anything
about the price. Only the briquettes from WESMA and PAMET can be found in the market. The
prices per kJ for these two are a lot higher than from softwood when consumed in the same stove.
For charcoal the price is the same as for the PAMET briquette, while the price for the WESMA
briquette is still higher. The results are shown in Diagram 5.
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42
MWBT Fuels - Results(Best f irst)
0 2 4 6 8
Sof tw ood
Hardw ood
Charcoal
PAMET
WICO
WESMA
Price perenergy unit(MK/MJ)
Diagram 5: Calculated prices from the MWBT results for comparing fuels.
4.1.4.2 Stoves
For briquettes (PAMET) it seams that a normal charcoal stove gives the higher energy efficiency
from the three stoves. The 3-stone fire gives bad efficiency for both firewood and briquettes.
Though when comparing with the firewood stove the firewood have 41 % less energy value in the
3-stone fire, while the PAMET briquette has only 35 % less energy value in the 3SF, see Diagram
6. This validates the theory of Richard Stanley that briquettes are less sensitive to the performance
of the specific stove than firewood.
Energy Content
Charc