Local oven for charcoal production

An appropriate alternative for carbonizing materials into charcoals

Takuro Haraguchi Kopernik Fellow

-Tokyo Institute of Technology Department of International Development Engineering

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Contents 1. Introduction・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 3p

2. Collection・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・4p

2.1 Bricks・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・4p

2.2 Mud・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・4p

3. Building the oven・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 6p

3.1 Theory・・・・・・・・・・・・・・・・・・・・・・・・・・ ・・・・・・ 6p

3.2 Let’s build up・・・・・・・・・・・・・・・・・・・・・・・・・・・・・ 7p

3.3 Covering outside of the oven・・・・・・・・・・・・・・・・・・・・・・・12p

4. How to use it ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・16p

4.1 Putting materials inside.・・・・・・・・・・・・・・・・・・・・・・・・16p

4.2 Lighting the fire・・・・・・・・・・・・・・・・・・・・・・・・・・・・16p

4.3 Cooling down ・・・・・・・・・・・・・・・・・・・・・・・・・・・・・16p

4.4 Taking out charcoal・・・・・・・・・・・・・・・・・・・・・・・・・・・17p

5. Supplement・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・・18p

5.1 Making a better structure・・・・・・・・・・・・・・・・・・・・・・・・18p

5.2 Lowering the cost to build an oven ・・・・・・・・・・・・・・・・・・・・18p

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1. Introduction

While managing the charcoal project in Kenya, which uses technology developed by MIT D-lab that allow the production of charcoal from agricultural, I faced several problems. One of the biggest hurdles for beneficiaries who were willing to get involved with the project was the initial cost of getting a drum, a necessary equipment for carbonization of agricultural waste under D-lab’s technology. That is because many of the participants live in impoverished villages and are not in a position to meet even some basic needs, and thus cannot afford to get a drum which cost 1,700Ksh (16.63 USD※1). Furthermore, they have to go towns to obtain it, making it even more inaccessible. Initially, I tried to manage the situation by using a loan model. This model consists of providing a loan and getting it repaid after 6 months from the profits of producing and selling charcoal. After 6 months however, when I came back to Kenya, I realized that they could not generate enough income from the charcoal project because several problems resulted in an underproduction of charcoal. At the same time, I received many requests from people in village to become beneficiaries of this project, although ultimately they were unable to participate because of the cost of the drums. Therefore, from the initial process of this project, it is evident that we must provide alternative ways to get involved with this project. It is important to consider accessibility for the poor when introducing a technology. A key word and possible solution to tackle this issue is “Localization”. There are many local technologies that are still unknown. There is a possibility to combine ideas from local technologies and our idea to solve the problem. One example is using an oven with bricks to substitute for the drums, which I will explain in the next section. Many villages in western Kenya uses bricks that are made from soil by local people, which means that bricks are accessible and cheaper.

1 I converted Kenyan currency to USD by this ratio USD/KES = 0.00978, 13th Oct 2011

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2. Collection Before creating an oven, you have to prepare two materials: bricks and binder, which are available at villages, eliminating the necessity to go to towns to collect materials. 2.1 Bricks Brick is a fundamental material to develop this structure. Of course, you can modify it to the oven design you want to make. But, I would like to show a basic model of this structure here.

First you have to access a place where you get baked bricks. You will use about 100 bricks. So, cost of getting bricks is about 500Ksh(4.86 USD) because the cost per brick is just 5 Ksh. 2.2 Mud It is very important to think about binder connecting bricks and making them into a very strong structure. So, what we can use locally is soil. Actually, people in villages already know how to make good mud from soil.

People in villages use mud for building their houses.

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2.2.1 Making mud

2.2.2 Fermentation

Second, you cover it by plastic paper for more than 3 days.

After 3 days, the mud is stickier. And you can know that the mud was indeed fermented from simply detecting the smell emanating from the mud.

The first step is to dig up soil by spade and add water. After that, you mix it with water by using spade and stepping on it by foot until mud reaches a consistency that is well mixed and sticky.

After making mud, we devise it to be stickier by fermentation. First, you collect mud in one place like the photo to the left.

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3. Building the oven After collecting the above two materials, now you can develop a local oven. 3.1 Theory Before actual construction, I would like to explain 4 structural requirements that enable us to get good charcoal. -1: A hole from which we put agricultural waste in it. Before starting to carbonize, agricultural waste must be inside a structure and so you need a hole from which you will place the materials inside.. -2: Holes from which the waste will catch fire. After putting the materials inside, you need to ignite them from bottom holes. -3: No hole from which heat can escape. After burning, you cover all holes so that you can stop providing oxygen while maintaining high temperature and pressure. -4: Places from which to take charcoal out. After cooling down, you can get charcoal from those places. With these requirements in mind, we designed the following oven.

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3.2 Let’s build up We can divide this structure into three parts: bottom structure, middle structure and top structure. And, you need to add mud between bricks from now to connect each other without removable bricks that I am going to talk about at 3rd layer. 3.2.1 The first and second layer (Bottom structure) To meet the requirement number two, we devise the first and second layer to accommodate holes from which we can supply burning material to fuel the fire. - First layer There are spaces between bricks (see Figure 1 and Figure 1a below) which are equal to the size of the bricks so we can insert bricks to cover this space and prevent heat from running away during the cool down process. .

Figure 1 Figure 1a

- Second layer

Figure 2

From this point on, I would like to explain step by step. First, you put 6 bricks on top of the first layer as shown in red to the left on figure 2.

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Figure 2a Figure 2b

Figure 2c

Figure 2d

For step #2, you put another 8 bricks on the top and bottom, which are drawn again in red thick lines on Figure 2a. Figure 2b shows the actual layout.

Figure 2d shows the complete second layer.

The last step for the second layer is to fill 6 spaces by splitting bricks so that they fit into the small spaces around the perimeter. These small spaces are shown by the 6 rectangles drawn in red thick lines on Figure 2c.

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3.2.2 The third, fourth, fifth and six layer (Middle structure) After completing the second layer, it is now time to build up the structure around the edge. For step #1 of the third layer, you will need to pile up 12 bricks on top of the edge of the second layer (see the green rectangles on Figure 3 below). - Third layer

Figure 3

Figure 3a

For step #2, you fill 4 spaces by splitting bricks as you did with the second layer to fit into the gaps. The 4 squares that are painted in darker green on Figure 3a mark these 4 gaps that need to be filled.

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Figure 3b - Fourth layer For the fourth layer, you pile up bricks in the same exact way as the third layer. Please be careful that there are 4 removable bricks in total on third layer and fourth layer and not to attach mud on these removable bricks. - Fifth layer. On the fifth layer, pay extra attention to the removable bricks on the third and fourth layer. You will have to pile up bricks on top of them, but the structure must be stable even when you take out the removable bricks. The key to creating this stability is the two bricks right above the removable bricks—they must be supporting each other. You can achieve this by connecting the sides of these two bricks and make them lock. Refer to the instructions and diagrams below.

Figure 5 Figure 5a (aerial view)

Please look at Figure 3b to the left. The two darker green squares indicate the 2 bricks that will become removable bricks. You must not attach mud on the edges of these removable bricks.

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Figure 5b

- Sixth layer For the sixth layer, pile the bricks as you did in the fifth layer. 3.2.3 Seventh, eighth and ninth layer (Top layer) For the seventh to ninth layers, you begin to make the hole on top. The perimeter of the bricks must gradually taper with each layer as illustrated in the diagrams below. - Seventh layer - Eighth layer

Figure 7 Figure 8

Figure 5 shows the side of the oven where the removable bricks are clearly visible. To achieve this, you must make a secure connection of the 2 bricks on the 5th layer right above the removable bricks (shown in orange on Figure 5a). Figure 5b shows a side view of the oven thus far. Note the circle drawn on the 5th layer on Figure 5b; that’s where the 2 bricks above the removable bricks (shown in blue) need to be connected.

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- Ninth layer

Figure 9 3.3 Covering outside of the oven 3.3.1 First cover (Before being dried)

Figure 10

After building up, you have to cover holes on the surface by mud. The trick of attaching mud is to pelt it on the surface instead of applying.

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3.3.2 Second cover (after being dried)

Figure 11 3.3.3 Third cover (after being dried again)

Figure 12

The purpose of second cover is to cover small holes that still exist after drying the first time, mostly because some mud falls down in the process of drying due to wind or rain (see figure 11). So, after first round of drying, find small holes on the surface that will allow matter to seep inside and cover them by pelting mud again.

The purpose of the third cover is to cover cracks. You will notice that there are many cracks on the surface after the mud becomes dry (see figure 12 below). So what you should do is to cover again, but this time use another type of mud that does prevent cracks from occurring: a mixture of mud and cow dung are normally used for building up foundation and wall of house in villages, and will suit this purpose as well. You can see how that mixture works after it dries on figure 12a.

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Figure 12a 3.3.4 Preparing mixture of mud and cow dung You put soil on cow dung and add water.

Figure 13 Figure 13a Then mix it together.

Figure 14 Figure 14a And unlike with mud, apply and do not pelt this mixture on the structure.

Can you see the difference? There are no cracks on the surface of this wall. By using this mixture, we eliminated cracks because the mixture of mud and cow dung is so sticky that cracks do not appear even after being dried.

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Figure 15 Figure 15a And your oven is now finished! If you don’t cover the oven with this mixture as a final step, it will fail to make good charcoal because heat will escape through cracks and holes, as seen on figure 16 below.

Figure 16

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4. How to use the oven 4.1 Putting materials inside This process is the same as using a drum. You put it in until it is full. One difference here is the size of the container. This oven is 1.5 times bigger than a regular sized drum so that more materials are needed to fill the oven. 4.2 Lighting the fire

Figure 17 4.3 Cooling down Once the fire is large enough to reach top of this structure, cover the hole on the top and 4 holes on the bottom to prevent oxygen from getting inside and heat from escaping. - Covering the hole on the top Do it the same way as you would with a drum by placing an ion sheet and putting soil on it. - Covering 4 holes on the bottom

Similar to when using a drum, you have to insert materials to burn (fuel) from the four holes that are located at the bottom.

A significant difference of the stove compared to a drum is that it attaches on the ground. If we use a drum, we remove stones on the bottom and put them on the ground before sealing the bottom edges and the top of the drum with sand. With the stove, however, you place four bricks into these holes instead to cover up the oven, and then you seal it tight with sand. The result will look similar to Figure 18 below.

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Figure 18 4.4 Taking out charcoal After you confirm that the bricks are not hot, then it is safe to take out charcoal from inside. First, you take out the removable bricks from both sides, as shown below.

Figure 19

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Figure 20

Then remove the charcoal inside with your hands.

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5. Supplements 5.1 Making a better structure A drawback stated by beneficiaries about this oven is that the holes on the first (floor) layer are so big that carbonized materials fall down very easily. So, they came up with a solution to prevent materials from falling down by putting iron mesh, regularly used for grilling meats, on those holes to capture the fallen, carbonized materials. 5.2 Lowering the cost to build an oven One way to bring the price of this oven down is to use unbaked bricks, which are 2 Ksh per brick, lowering the total cost to 200Ksh. You may think that unbaked bricks will not support the structure as strongly as baked ones; however, the process of carbonizing materials with fire will essentially bake the bricks because the process is the same for baking bricks from mud. Thus, the more you use the oven, the more firm and stronger the oven will become, making the 200ksh alternative oven a more viable possibility.

If you have any questions or suggestion, please let me know.

takuro.haraguchi@gmail.com

Takuro Haraguchi Kopernik Fellow

Tokyo Institute of Technology Department of International Development Engineering