Small scale charcoal making: A manual for trainers
 Day 6
 Session 19: Evaluating charcoal yields Session 20: Program evaluation

### Session 19: Evaluating charcoal yields

 Total Time: 2 hours Objectives: * To determine the moisture content of wood * To calculate the yield of a kiln Materials: Newsprint, felt-tip pens, pencils or pens, notebook paper, sample pieces of wood of varying moisture contents. Resources: * Attachment 19-A, "Elementary Calculation of Moisture Content" * Attachment 19-B, "Energy Potential of Raw Wood" * Attachment 19-C, "Charcoal Yield Worksheet"

 Trainer Notes * Prior to this session, it will be necessary to gather several pieces of wood from among common local varieties and calculate their moisture content. Number the samples and record their exact moisture contents on a sheet of paper. (See Step 4) * Also, it will be necessary to create and solve two hypothetical yield calculation problems. (See Step 8)

Procedures:

Step 1. (5 minutes)

Explain the session objectives.

Step 2. (10 minutes)

Ask participants to briefly review and explain factors to be considered in evaluating different types of kilns.

 Trainer Notes * Remind participants of the factors mentioned in the article, "Realities of Making Charcoal" and of the criteria lists which were developed in their design plans. * Some factors which should be mentioned include: - user needs - labor requirements - capital requirements - carbonization time - kiln capacity - portability - durability - availability of construction materials - ease of operation - yield * Point out that "yield" calculations are an important way of determining the specific energy efficiency of a particular kiln design.

Step 3. (15 minutes)

Ask participants to identify some of the variables which should be considered in calculating yield.

 Trainer Notes * Explain that yield calculation essentially involves comparing the amount of potential energy going into a kiln in the form of wood to the amount of energy potential coming out in the form of charcoal. * Stimulate discussion by asking: - What variables must be considered in determining the energy potential of raw wood? - What variables should be considered in determining the energy potential of charcoal? * Some important variables which should be highlighted include: - moisture content of raw wood - weight of raw wood - brands found in kiln - moisture content of charcoal

Step 4. (15 minutes)

Distribute the samples of raw wood and have participants estimate the moisture content of each sample.

 Trainer Notes * Record their estimates on newsprint. * Point out that different wood species have different densities, so weight alone may not indicate moisture content. The feel and smell of the wood are often more reliable indicators. * A game can be made of this activity by offering a prize to the participant who most accurately guesses the actual moisture content of a particular sample.

Step 5. (5 minutes)

Reveal the real, calculated moisture content of each sample by writing it on the newsprint beside their estimates.

Step 6. (20 minutes)

Distribute Attachment 19-A, "Elementary Calculation of Moisture Content" and Attachment 19-B, "Energy Potential of Raw Wood" and practice calculating moisture content.

 Trainer Notes * Allow participants time to look over the attachments and ask questions. * Explain that the oven-dry weight of a quantity of wood can be determined by baking random samples at below 212° centigrade until stable weight is obtained (usually overnight). * Identify individuals among the participants that are familiar with calculating moisture content and ask them to help others in the group to work a few sample problems using hypothetical weight figures.

Step 7. (15 minutes)

Distribute and explain Attachment 19-C, "Charcoal Yield Worksheet."

 Trainer Notes * Explain the basic formula outlined on the attachment by working through the sample problem on newsprint. * Mention that the moisture content of the charcoal is assumed to be negligible unless it has been wetted by rain or during the extraction process. If necessary, the moisture content of the charcoal can be determined by baking random samples.

Step 8. (20 minutes)

Ask participants to practice solving two hypothetical yield problems.

 Trainer Notes * Write two hypothetical problems on newsprint. * Ask those participants who work out the problems early to help others in the group who may be experiencing difficulty.

Step 9. (15 minutes)

Conclude by asking participants to discuss examples of ways in which yield calculations could be helpful at their work sites.

 Trainer Notes * Stimulate discussion by asking: - What difficulties would you encounter in collecting yield data at your work site? - How could these difficulties be overcome? - Why is accurate yield data important?

### Attachment 19A: Elementary calculation of moisture content

In forestry it is customarily given as a percent fraction on a DRY basis:

DRY basis

Beware that we customarily think in terms of "percent of a total," in this case giving a WET basis figure which is NOT generally used:

WET basis

### Attachment 19B: Energy potential of raw wood

Raw Wood Charged

 Air-dry wood Partially dry wood Wet wood 25% m.c. 50% m.c. 100% m.c. Fig. 1 Fig. 2 Fig. 3 1. 25 kg 1.5 kg 2.0 kg 4850 kcal 4700 kcal 4400 kcal

 Ranking Very Good Fig. 4 Fig. 5 Fig. 6 0.35 kg. 35% yield 0.30 kg. 2250 kcal 0. 24 kg. 1800 kcal 2625 kcal 54% of 30% yield 24% yield energy initially recoverable 48% e.i.r. 41 % e.i.r. Adequate Fig. 7 Fig. 8 Fig. 9 0. 25 kg. 1875 kcal 0.20 kg. 1500 kcal 0.15 kg. 1200 kcal 25% yield 20% yield 16% yield 39% e.i.r. 32% e.i.r. 27% e.i.r. Very Bad Fig. 10 Fig. 11 Fig. 12 0.15 kg. 1125 kcal 0.10 kg. 750 kcal 0.08 kg. 600 kcal 15% yield 10% yield 8% yield 23% e.i.r. 15% e.i.r. 14% e.i.r.

Fig. 2 Energy Available from Raw Wood and from the Charcoal

Produced from It with Respect to Moisture Content and Efficiency of Carbonization

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9

Fig. 10

Fig. 11

Fig. 12

### Attachment 19C: Charcoal yield worksheet

The basic formula for determining yield is:

Brands may be of two types: wet and oven-dry. Brand content of 2% or more by volume is an immediate indication of kiln inefficiency.

There are essentially four options in accounting for brands in yield calculations:

1) Subtract wet brands from wet wood, then calculate oven-dry wood weight.

2) Subtract dry brands after calculation of oven-dry wood weight.

3) Do both of the above.

4) Ignore the brands in the calculation and list x% yield with x% of brands.

Option #3 is generally considered to be most accurate.

 Sample Problem: Work Space 875 kilos of charcoal 100 steres of wood at 350 kg. per stere 8 kilos of wet brands 4 kilos of dry brands 20% moisture content (ODB)

### Session 20: Program evaluation

 Total Time: 2 hours Objectives: * To evaluate the effectiveness of the training program * To identify ways in which future charcoal training programs can be improved Materials: Newsprint and felt-tip pens

Procedures:

Step 1. (10 minutes)

Review and explain the session objectives.

 Trainer Notes * Remind the participants of the design principles which were discussed during the session on re-design of kilns (Session 13, Day 3). Point out that the principles of testing, evaluation and re-design also apply to the development of effective training programs. * Explain that evaluation through feedback from participants can serve as the basis for improving future charcoal training programs.

Step 2. (25 minutes)

Have the participants divide into groups of 3 or 4 and record on newsprint their observations regarding the effectiveness of the training program.

 Trainer Notes * Ask that each group list three aspects of the program which were particularly effective and three aspects which were particularly ineffective. * For each ineffective aspect of the program, ask that participants suggest ways in which it could be improved. * Encourage participants to be as specific as possible and to consider all aspects of the program (i.e., sequence of sessions, content of sessions, trainer techniques, etc.). * If possible, the trainers should join the small groups and participate in the activity. * While the small groups are working, arrange chairs in a semicircle at the front of the room so that three people can face and speak to one another while reading the posted observations and suggestions. Arrange a second row of chairs around the first three. The configuration should look like this: Row of chairs * Approximately five minutes before the end of the time allotted for this step, circulate among the groups, remind them of the time remaining and ask that they post their observations and suggestions when they are finished.

Step 3. (10 minutes)

Have the group reconvene and occupy the chairs the outer semi-circle. Explain the "Fishbowl" activity.

 Trainer Notes * Ask if anyone has had experience with this activity. If so, ask them to help you with the explanation. Your explanation should include the following points: - Only three people at a time will be in the inner semi circle - The role of each of the three people will be to discuss and respond to the posted observations and examine the feasibility of the suggestions. - The role of those in the outer semi-circle will be to observe and listen without speaking. - When someone from the outer circle wants to enter the discussion, a person from the discussion group should leave and join the observers. * The reason for using the fishbowl structure is to provide a comfortable format for discussion and to encourage constructive feedback and suggestions. Therefore, it is important that people feel free to express their thoughts without fear of reprisal. People should be encouraged to enter the discussion and to exchange places with one another when they have something to say. It is a good idea to have at least one member of the training staff in the discussion group at all times.

Step 4. (10 minutes)

Just before the discussion, ask one of the participants to scan the lists and point out any commonalities and parallels among the observations.

 Trainer Notes * This quick identification will help provide order and avoid repetition once the discussion begins.

Step 5. (50 minutes)

Ask that three volunteers move to the inner semicircle and initiate the activity by responding to one of the observations.

Step 6. (10 minutes)

Summarize the observations and suggestions for improvement that resulted from the fishbowl discussion.

 Trainer Notes * Stress those observations which seem most generally agreed upon by the group and most feasible in terms of future implementation.

Step 7. (5 minutes)

Thank the group for their participation in this activity and in the training program.

 Trainer Notes * It is suggested that a barbeque be held immediately following this final session. Participants and staff could then have the opportunity to prepare a meal using charcoal produced during the program.