Biomass Briquettes in Malawi

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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

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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

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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

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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

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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.

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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

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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

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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

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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.

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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

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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:

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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.

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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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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.

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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

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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.

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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.

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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

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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 PA MET MIRTDC Sof tw ood WICO Charcoal Energy per weight unit (kJ/g)

Biomass Briquettes in Malawi