Chapter 1
CASE STUDIES (contd.)

VI. ECONOMIC ASPECTS

6.1. Cost Calculation of Stove Production

As seen from the calculations above, sweetmeat (jilebi) production has an excellent return on the initial investment (profits amount to 59% of the total investment). There are 2 or 3 shops every 100 meters in cities like Kathmandu and sweetmeats are easily available in roadside restaurants.

6.2. Fuelwood Used in Total Production Process

Based on the case studies, the consumption of fuel varies between the two different kinds of stove. It is observed that on an average cooking one kg of jilebi (sweetmeat) consumed 0.446 kg of fuelwood in one stove while another stove consumed 0.597 kg of fuelwood. This was primarily due to the size of the stove on average 0.515 kg of fuelwood is required per kg of jilebi. The cost of fuelwood per kg of jilebi is about Rs.2.06 (3.4% fuelwood cost per kg. of jilebi).

6.3. Analysis of Sweetmeat Production

Table 1. Results of Sweetmeat (Jilebi) Cooking Tests

Remarks: Pan balance was used for the tests
Fuelwood with 16% moisture content
Stove A: WBT - 16.2 PHU with 37 gm/min BR
Stove B: WBT - 14.7 PHU with 48 gm/min BR.

VII. SUGGESTIONS FOR FUTURE DEVELOPMENT

Sweetmeat production is a very profitable business. In cities, the main problem is the smoke emissions which pollute not only the shop keepers house but also affect neighbours. Because of this people are switching from fuelwood to kerosene or LPG but there are certain items which are best produced with firewood. Kerosene and LPG fuel are also not consistently available.

• Based on analysis of stove use some suggestions for future development are as follows:

• A chimney or chimney hood should be incorporated into the stove design.

• A metal grate should be introduced for better combustion,

• A round bottomed pan should fit more deeply into the combustion chamber.

• If a chimney is not used, the pot support should be small as in the Thai Bucket Stove so that heat loss can be minimised. This will also ensure that the cook will be exposed to less heat.

The kitchen or working area should be clean and the cooks should stand while working instead of sitting. Improved working conditions may make the work more attractive to young people.^₦

D. BIOMASS STOVE FOR POP-RICE INDUSTRY

K.M. Sulpya
RECAST
Kirtipur, Kathmandu, Nepal

I. BACKGROUND

Pop-rice (golphaki) is a very popular food item in Kathmandu Valley and in the southern part of Nepal. People in Kathmandu Valley offer this food to Sitalamai, the goddess of smallpox. If a child contracts smallpox, the villagers go to the temple of Sitalamai and worship her so that the child will get well. A portion of the pop-rice thus offered is taken back and given to the child. Since smallpox has been eradicated from Nepal the practice of worshipping the goddess associated with smallpox has lessened. In the southern part of Nepal (Terai), one can see people selling and buying pop-rice. The Riksha -three-wheeler pullers, carters and other poor people eat pop-rice as a dietary staple when they cannot afford to buy a heavy meal of rice and bread. Pop-rice is a very light edible item. It is indispensable in the Terai region. There are many restaurants in Nepalese cities that offer sekuwa (small pieces of meat roasted in charcoal) which is eaten along with pop-rice, radish and lemon. This item is inexpensive and very popular.

Pop-rice processing is a small scale village industry which falls under the category of cottage industry. According to Suwal (1988), the pop-rice processing area is quite distinct in the villages. Workers normally live together and one can see households of 25–30 in one area producing pop rice. Production is usually a family business but some groups employ labour for transportation of the finished product.

Pop-rice production flow diagram

The raw material used in this industry is mainly rice. Other materials which are required include earthen pots, fine sand, sieves, and winnowing trays.

The people involved in this business are generally poor. They don't buy fuelwood. Fuel collection is done by the household members. Forest weed (Eupatorium odonoforum) is available everywhere. This weed is also known to be a forest destructor because when the weed dries it becomes highly flammable. Twigs, branches, bushes, leaves etc. are also collected.

The villagers are illiterate, and so they don't keep track of their labour costs. Every two or three days some members collect fuel; the weeds, twigs are tied in bundle and left in the sun until dry.

II. THE STOVE

2.1. Stove Design

The stove use for pop-rice production is traditional. There are three-pot holes in the first series and one-pot hole in the back. The stove is fixed to the ground floor or outside the house. In the first two-pot holes, there are no pot supports while small pot supports are used in the third pot hole. The pop-rice stoves in the Machhegaon village are small. The height of the stove is 17 cm, pot holes are 16 cm diameter, a wood feeding hole is 12 cm × 10 cm. The wood feeding hole is made small and accommodates weeds, agri-residues, and branches of trees.

2.2. Stove Construction and Materials

The stove is made of mud-bricks. Mud is mixed with cow dung and chopped rice-straw. The exact proportions are not known. The stove can be made within 2–3 hours, though it must dry for several days before it can be used.

III. FUEL USED AND PREPARATION

Rice husk, forest weed (Eupatorium odonoforum), wheat straw, maize stalks, maize cobs, twigs and branches, bushes, etc. are used for fuel. First, they place 2–3 kg of rice husk in front of the stove and place some inside the stove (fire box) as a fuel bed. Forest weed is then added (5–6 sticks at a time) with a regular dusting of rice-husks inside the fire box. The forest weed is 1 cm in diameter and about one meter in length.

3.1. Heat and Combustion

All the pop-rice producers in Machhegaon village use low grade fuel. For good power output and continuous heating, a rice husk bed is used. Rice-husk increases the power output. The twigs and forest weeds are air-dried before use. During the study, the moisture content is found to be 18 percent. During the combustion, fuel burns yellowish to light red. The fuel is pushed towards the pot hole on the right which has a pot which contains sand. The temperature recorded here is around 710 degrees Celsius, while the temperature in the left pot hole is around 615 degrees Celsius and the temperature in the back pot hole is around 518 degrees Celsius. Temperature fluctuates as fuel is added. Sometimes the temperature falls 400 to 500 degrees Celsius.

A typical of stove used in pop-rice production

After completing the process, the residual ash are removed. They are used as cleaning powder for plates, pans, pots, etc and also for soil improvement in the garden.

3.2. Operation and Maintenance

Heat is controlled by adjusting the amount of fuel. The stove gets light impact because of light fuel used. Red clay mixed with cow dung is used for plastering from time to time.

3.3. Cooking Utensils and Design

Cooking utensils are only round bottomed earthen pots. The size is 20 cm height and 18 cm diameter (pot base).

IV. PRODUCTION PROCESS

Paddy is soaked in water for about one day in a special pot called a phoshi. The paddy is then boiled in the phoshi after which the water is drained out and the paddy is air-dried. The paddy is then heated in hot earthen pots until it begins to pop up. The paddy should not be completely popped. Complete popping will covert the paddy into a different thing known as lava or pop-paddy which is required especially for auspicious occasions.

The incompletely popped paddy is then dried in the sun for two or three days. It is then taken to the mill to separate the chaff from the rice. Some use a traditional threshing device. Clean rice obtained after winnowing is popped for a second time in an earthen pot containing heated sand. The pot is strongly heated. Three such earthen pots (two containing sand and one which is empty) are placed in series over the three-pot-hole stove.

In the three-pot-hole stove, three earthen pots are heated but two pots contain sand while handful of rice grains is warmed up in the empty pot. Certain mechanisms or tricks are applied so that more heat goes towards the first pot containing sand when the sand is sufficiently heated and turns red-hot then it is poured into the empty pot containing warm rice. As the warm rice-grains come in contact with the red hot sand, they start popping up almost instantaneously. Immediately the second pot containing sand which receives lower heat is poured in to the first pot to heat it up a bit. Continuous stirring of the grains gives them a uniform heat. Each grain rice is enlarged in size as it pops.

The mixture is then poured into the sieve. Fine sand passes through the pores of the sieve leaving behind the inflated snow-white rice grains which are called pop-rice. The process is repeated continuously until complete.

V. PROBLEMS AND CONSTRAINTS IN THE UTILIZATION OF STOVE

Pop-rice production is a long process. Only one handful rice-grains is heated at a time; thus the cook has to work 10 to 12 hours per day. The stove produces smoke. In the absence of fuelwood, the cook normally uses forest weed, rice husk for fuel bed and agri-residues. Because of this the cook has to pay continual attention to the fire.

Production difficulties and competition with products from the southern part of Nepal have forced some producers to abandon their activities.

VI. ECONOMIC ASPECTS

6.1. Cost Calculation of Stove Production

The existing traditional stove costs about Rs.40.

6.2. Capital Input vs. Economic Output

As seen from the calculations(see Annex 1), pop-rice production has a very low profit in comparison to other activities. Two day of work yields an income of Rs. 161. The Nepalese are not satisfied with their situation but have limited options.

6.3. Fuelwood Used in Total Production Process

Case studies suggest that fuel consumption does not much vary from one stove user to another. The stoves are more or less of equivalent size.

On average 17.4 kg of fuel was consumed for making 12.72 kg of pop-rice. That means, producing 1 kg of pop rice requires 1.37 kg of fuel.

Fuel is not purchased for this activity but rice husks cost Rs. 1.50 per kg. Assuming the same price for weed, the percentage of fuel cost to total production cost is 5.6 percent.

6.4. Production Cost and Economic Analysis of Pop-rice Production

Sales

42 kg paddy gives 12.72 kg pop-rice.
12.72 kg pop-rice: Rs. 480 (whole-sale price)

The profit equals to Rs. 11 only but the people involved in this business do not count their labour. Excluding labour the benefit they got is Rs. 161.

Table 1. Results of Pop-rice Production Tests

Stove A: Nuchhe Maya Maharjan

Stove B: Sun Maya Maharjan

Remarks: Pan balance was used for the tests.
Local ‘Pathi’ was used and converted into kg.
Stove: A: WBT -13.6 PHU with 41.6 gm.min kg BR.
Stove: B: WBT - 14.4 PHU with 34.62 gm/min BR.

VII. SUGGESTIONS FOR FUTURE DEVELOPMENT

The people involved in this business, especially those in the Mechhegaon village of Kirtipur area are not satisfied with the price they receive from the dealers or shop keepers; unfortunately they have no alternative. They must work for 8–10 hours processing rice-grains into pop-rice on a wet ground floor and in an unmanaged kitchen.

Based on an analysis of the stove used, some suggestions for future development are as follows:

• A chimney or chimney hood or kitchen window should be introduced for smoke removal from the kitchen.

• Proper lighting and installation would contribute to a better kitchen environment.^₦

Case Study - Philipine

A. RICE HULL STOVES IN SALT MAKING

Hil J. Padilla
AGTALON
2430, Pangasinan
Philippines

I. INDUSTRY BACKGROUND

1.1. Brief Information on Salt Making Techniques

There are 2 methods of salt making in the Philippines.

A. Solar Bed Method

This method is locally called “balara”. First, salt water is channeled into shallow ponds. The water is then evaporated through solar radiation and the salt that cakes on the bottom is scraped. This process yields coarse salt granules usually referred to as “rock salt”.

The two major drawbacks of this method include the use of polluted sea water in urban areas and the coarseness of the granules. Some regions of the Philippines only use fine grained clean salt. If balara salt is used in the preparation of fermented fish sauce for “bagoong” and “patis”, the resulting product is of poor quality. However, the production method is inexpensive as it does not use fuel.

Dripping salt to dry

B. Cooked Salt Method

This method is mainly used in the province of Pangasinan, the study site. The place is also noted for “bagoong”. Pangasinan literally means salt making place. Salt is made by evaporating salt water in large open vats with heat source from biomass cookstoves.

The method produces very clean, fine grained salt. Impurities are removed during cooking. Prolonged boiling sanitizes the salt, thus satisfying a requirement in the preparation of fermented fish.

To save fuel, some salt makers use partially evaporated salt water from solar ponds. The concentration of the salt is ready for cooking when the branch of a tree that grows near brackish water floats. Sometimes a hard rubber material is used to determine the salt concentration.

Pouring the rice husks

An innovation by inland salt producers is to buy the coarse, cheap “balara” (rock) salt, dissolve it in water and re-evaporate it. “Balara” salt is currently P120.00/50 kg bag while the “cooked” salt is P250.00/bag. To increase salt yield other producers use salt water to dissolve the rock salt. The mushrooming of this kind of salt making industry is one indication of its viability as a business enterprise.

1.2. Development of Stove Used

Traditionally, the stove used in salt making is a wood-fueled. The efficiency of the stove is increased by enclosing the fire box with walls or by embedding the stove under the ground, with a smoke outlet at the other end. The salt processing sites are located near seashores. Usually, a processing venture is run by one household as a cottage industry and uses family members for labor. In the late 1970's wood became more expensive and difficult to collect, prompting a shift to rice hull stoves.

It was also the time when the rubber roll type of rice mill replaced the “Engelberg” (steelhuller) type. The rubber roll is sometimes called the “2 pass miller”. The rice is first dehulled by the 2 rubber rolls rotating at 2 different speeds and then the grains are passed on to a metal jet polisher. The rubber roll produces ‘rice hulls’ whereas the 1 pass Engelberg type produces rice bran.

The abundance of rice hulls in inland rice producing areas made it economically feasible to reprocess the “balara” salt. In general, the scale of these rice hull fired salt making industries is bigger than their woodfueled counterparts.

Rice hulls constitute about 14–16% of the harvested paddy weight. About 8 to 9 million tons of rice hulls are produced each year in the Philippines. If properly utilized, rice hulls could become a substantial renewable resource.

The fuel entrance to the combustion chamber

The actual energy content of the rice hull is 6.000 to 6.800 BTU/lb or 14 to 16 MJ/Kg. This amount is about the same as wood waste burned as fuel from timber production industries. However, it has a high ash content (16 to 23%) which makes the energy content per unit volume rather low.

Cleaning up the ashes to keep air flow into the combustion chamber

The origin of the rice hull stove design is unknown. In the Philippines, it is called the “ipa” (rice hull) stove and used in different industries like mushroom making, restaurants, etc.

They are mainly constructed by local masons. In Yogyakarta and Central Java, it is called the “Tahu” (soy curd) stove. In Blitar, East Java, it is called “Gula Jawa” (coconut sugar) stove.

1.3. Problems and Constraints in Stove Utilization

The main problem with the woodfed stove is the high cost of wood which reduces the net income. The high cost of wood makes the rice hull stove more attractive. In the salt factory studied, the cost of one 10-wheeler truck load of rice hull is only P200, and delivery is free. Others gather hulls as waste from rice mills. In many rice mills, millers pay contractors to remove and dispose of rice hull; they are thus pleased to offer the hulls to local entrepreneurs who can make use of them.

One of the problems with the rice hull stove is the high amount of residual rice hull ash. In the factory studied, the ash is dumped in the seashore. Rice hull ash is becoming a pollutant. Although rice hull ash is a very good soil conditioner, very few farmers use it.

The rice hull stoves also release more smoke compared to woodfuel stoves with the same design. Some salt makers prefer wood because it requires less attention during the cooking process. However, in the rice hull stove studied here, smoke was not much of a problem for the workers because of the chimney.

The rice hull stove is also expensive to construct. The stove makers charge P4,500.00 per concrete stove with ceramic lining. The stove pan made of flat G.I. sheet costs around P700/pan and one stove uses two pans making it P1,400/stove. Some resource poor salt makers use clay with bamboo lining rather than clay, bricks and concrete lining for their stoves; also they use only one pan. Properly constructed bamboo lined stoves are as durable, so this modification is not a problem.

Workers complain that rice hull make them itch. Although cooler than the open type stoves, the workers using rice hull stoves still complain about the relatively hot working environment.

Visual inspection of the stoves seems to suggest that they are the same. However close observation of the cooking process reveals that they differ much in efficiency. The efficient stove could process 3 loads in 16 hours, while the other stoves could accommodate only 2 loads. This is not due to the skill level of the workers, because if they switch stoves, the results are the same. The workers are paid by the number of loads processed. So, the workers with a more efficient stove earn 33% more. A minor change in the stove design like the position of the grate made the difference between the two models. Modifications will be discussed in the following sections.

The grate of the stove used in salt production

Although the cost of rice hull fuel is minimal, the amount of fuel used could (approximately 250 kg rice hull/ cooking) still further be reduced if there is improvement in the efficiency of the stove and consequently, a lessening of work and production cost.

II. STOVE TESTING

The first stage of the study included a survey of the salt industry and the different stoves used. We visited three salt factories, each of which used the same basic rice hull stove design but with occasional differences in the dimensions. Observations of the cooking practice and interviews with workers on the characteristic of the industry were conducted. For comparative purposes, a woodfuel fed salt factory was also visited.

The biggest of the three factories (with 14 stove units) was chosen for stove testing. In this factory, the 2 fastest cooking stoves (stoves that could cook 3 times per day) and the 2 slowest stoves (stoves that could cook only 2 times per day) were selected for testing. These stoves have the same pan sizes and stove dimensions and position of grate, (inclination of tunnels and size of tunnels going into the chimney). We noted that the stoves had approximately the same performance even when the workers change, which suggests that the difference in performance is due to stove design rather than skills of workers in managing the fire.

The short water boiling test and the long water boiling test were used to assess (as described by Waclaw Micuta, please see attachment for methodology). The 2 water boiling tests could also be considered cooking tests as the cooking method is evaporating the salt water. So, in the first test, instead of using tap water, salt water with salt concentration of 200 was used. Ambient air temperature and climatic conditions during the were also noted.

Four stoves were studied, the 2 fastest and the 2 slowest. Two replications were taken.

III. RESULTS AND DISCUSSIONS

3.1. The Industry and Its Requirement

The salt processing industry studied employs the “cooked salt” method earlier described. “Balara” or rock salt derived from evaporating ponds is bought usually from local “balara” salt producers or imported from other countries like India. This is then dissolved in salt water and then cooked in wide shallow pans using rice hull as fuel. The resulting product is a clean, fine granules salt which is then sold at a higher price.

The Salt Making Procedure
(Please see production flow diagram)

1. The dissolving tank usually made of concrete or wood lined with epoxy sealants, is filled with about half of the required amount of water. A plastic net screen covers the top of the dissolving tank. When rock salt is poured through the screen, large impurities are withheld from the tank. The other half of the required water is then poured into the tank to further dissolve the salt. Motorized water pumps are used. The ratio of salt to water is such that it will have a reading of 20 on the barometer. At this factory, workers no longer use the barometer because the tanks have been pre-calibrated. Workers can fill water up to the appropriate marking on the walls of the tanks.

2. By means of gravity, the dissolved salt is poured by workers into the cooking pans. The pans are filled 1 inch below the rim to allow room for boiling so the solution won't overflow.

3. Then it is cooked until salt granules form but are not crystallized. If cooked until dry, it will burn or form big chunks which are difficult to pulverize. So, when there is still a small amount of water, the small salt granules are scooped and transferred to bamboo baskets located just above the pans supported by wooden planks. Excess water drips back into the pans. The baskets remain there until the next batch of cooking is about to be harvested. It is worth noting that during the cooking process, the dirt floating on top of the boiling salt water is removed with nets sewn in metal rings and thrown away.

4. While the harvested salt is drying, another batch of salt water is added into the remaining water in the pan. The remaining water in the pan is around 15–20% of the original amount. Then the second batch is cooked as outlined above. But after around six rounds of cooking, the remaining water is thrown out and replaced. If the remaining water is not discarded after so many rounds of cooking, the salt quality suffers.

Salt making production flow diagram

Cooking Utensils

1. cooking pan - made of gauge 18 plain G.I. sheet
2. flat shovel - used to scoop the cooked salt
3. dirt scoop - iron ring with net to remove floating particles
4. bamboo basket - salt container used during drying
5. shovel - used to take away the ashes
6. iron rod - used to push down the rice hull and remove the ashes to refill the fire grate

Cooking pan - made of gauge 18 plain G.I. sheet

3.2. Stove Design

Stove Dimensions

The size of stove is 249 cm long, 125 cm wide and 60 cm high. The size of chimney is 315 cm long, 50cm high, and the length of the channel is 107 cm.

Stove Materials

1. Body - the body is made of concrete with brick lining inside. Sometimes the inner lining is made of mud instead of bricks.
2. Chimney - made of concrete hollow blocks measuring 10 × 20 × 40 cm. The chimney is square from top view.
3. Fire grate - made of 0.625 × 5 cm flat bars
4. Rice hull fuel tank - made of concrete blocks. Sometimes a worn out refrigerator body is used instead of concrete.

3.3. Stove Operation and Maintenance

The main cooking trick employed is directly related to time management.

The fuel hopper is filled with rice hulls. Some of the fuel will slide by means of gravity down into the grate. The fuel is then lighted at the bottom of the grate using paper as kindling material.

The grate will become full of ashes which will impede air flow and the introduction of additional fuel. The ashes are removed periodically, allowing a fresh batch of fuel to slide down. The ashes are loaded into baskets and dumped elsewhere. In this factory, it is dumped on the shoreline, thus polluting the nearby sea.

Cooking is quickened by using a very intense fire in the beginning of the cooking process until the time when the salt is about to be harvested. Sometimes a very intense fire will make the boiling water overflow. Harvesting of salt starts when granules form. The granules begin floating when there is still around 20–25% of the original amount of water left. The salt is then scooped into the dripping basket above the pan. While dripping, the pan is filled with salt dissolved earlier in the tank. The refill will come to a boil quickly. Before retiring for the day, the stove is filled with another load to maximize the remaining heat and fuel and left until the following day. This technique allows more salt to be cooked.

The fuel is loaded into sacks by women, whereas the cook usually loads the fuel. One women may supply 4–8 stoves and will be paid by the number of sacks.

Stove maintenance mainly consists of cleaning the chimney. Minor repairs are rare due to the sturdy concrete stove material used.

It is also interesting to note that the workers use the boil water for food preparation.

3.4. Stove Efficiency Computations

A. Test Conditions and Cooking Test Results

The test conditions and the results of the actual cooking test are shown in table 1 at the following page.

The data was obtained under normal cooking conditions. The stoves had been used at least once before the data was taken, thus the initial water temperature in the pan ranged from 38–43° C as compared with the water temperature of the tank which is 30–32°C. The rice hull fuel registered 15% moisture content.

Although the 4 stoves have the same general dimensions, stoves C & D have an inclined channel going into the chimney. From the top view the channel in stoves A & B are straight while in stoves C & D, the channels after the main stove body are wide and tapers to the chimney. The chimney dimensions are the same for all 4 stoves.

Although the pans have the same dimensions, the data shows that stoves C & D contain more initial salt water volume (C=463.5 liters; D=487.5 liters) compared to A & B (A=434.0 liters; B=421.0 liters). One liter was assumed to be 1 kilogram. This disparity can be explained by the relative mounting of the pans; in A & B, they are inclined a bit and tend to spill at one end if overloaded, whereas C & D are more level. Stoves C & D were constructed recently and have and have corrected the earlier flaw.

Stoves C & D boil the mixture significantly faster even if it contains a higher volume of salt water. Accordingly, they consume a higher amount of fuel. The style of tunneling creates a better air draft which allows for increased consumption, as will be explained in the following sections.

Table 1: Actual cooking test results

Likewise, a similar trend could be observed in the time consumed till salt harvest and in the total amount of fuel utilized.

B. Specific Fuel Consumption, Percentage Heat Utilization, Power Output and Burning Rate

Specific Fuel Consumption and Rate of Cooking

The data reveal (Table 2) that stoves C & D have significantly lower fuel consumption, faster cooking, and higher salt yield.

Table 2 : Average fuel consumption, Time consumed till salt harvest and Salt yield

The specific fuel consumption was derived by dividing the total fuel consumed by the salt yield. Stoves C & D have lower SFC's than stove A & B, with stove D having the lowest (Table 3), followed by stove C.

Table 3 : Specific Fuel Consumption

How about the time required to reach the boiling point and the speed with which this is reached ? The data shows (Table 4) that stove C (29 minutes) reached the boiling point fastest. Stoves C & D, however consumed more fuel than stoves A & B to reach the boiling stage. Stove B reached the boiling point the slowest (55 minutes). When the worker tending stove B tried to increase the fire to the same intensity as stove C, lots of smoke developed and the air flow was impeded. However, stoves C & D, consumed more fuel to reach boiling stage. Although it took a long time for stove B to reach the boiling point, it consumed the least fuel.

Snow white salt from cooked salt method	Packaged salt, ready to the market

Table 4 : Average time consumed to boil and Average fuel consumption up to boiling point

In theory, the degree of salt recovery depends on the concentration of salt. In table 5, stoves C & D have higher salt recovery based on the amount of salt water evaporated.

Table 5 : Percentage salt yield based on the amount of water evaporated

There are 2 possible explanations for this. One, it is customary for the cook/worker who tends stove C & D to refill the pans prior to complete evaporation. The residual fluid increases the concentration of salt in the additional solution pans. Hence, this will result to a little bit higher concentration. This explanation is likely because at the beginning of the study all of the pans had the same concentration of salt. However, in successive trials the concentration was not measured because all of the stoves used the same number of bags of salt. Secondly, the coarse salt used in C & D may have had a higher concentration as it came from the Philippines while the salt used in A & B came from India. Also the worker tending stove C & D may have added a little less water. By the time this discrepancy was noticed they had run out of salt from India, such that a detailed analysis was not possible. Based on preliminary rate results, stoves C & D were thought to be more efficient.

C. Percentage Heat Utilization, Power Output and Burning Rate

The stove efficiency (PHU) was computed using the following formula and constants;

The Specific Power Output is computed using the following formula:

Burning rate = Salt Yield / time

The Burning Rate was taken based on salt yield and based on the amount of water evaporated.

The results of the computations are presented in table 6 at the following page.

Table 7 shows that stoves C (30.5%) and D (31.09%) have a higher percentage heat utilization or thermal efficiency than stoves A (22.65%) and B (27.35%). Visual inspection construction revealed that C & D, have stronger updraft due to the tunnel design described earlier. Thus A & B expel darker smoke from their chimneys, especially when the fire is intensified. Stoves C & D also used fuel and produce more power than stoves A & B.

Table 7 : Percentage Heat Utilization & Power output

Another factor which contributes to the efficiency of stoves C & D is the position of their grate. The grates slope down to the middle part allowing the heat to be distributed across the surface of the pan. In A & B, the fire hits the end of the pan near the fuel hopper because the grates are placed below the end of the pan.

Table 8: Average burning rate based on salt yield and evaporation

3.5. Economic Analysis

Production Cost and Revenues

Assumptions:

• Family/household managed salt making enterprise
• Using 2 stoves containing 2 pans/stove of the same size as in the study done. The stoves are made of concrete
• Housing is made of local material. Thatched roofing is used as G.I. sheets corroded with smoke from the stoves.
• Coarse salt is procured and dissolved in water.
• Salt makers produce 2–3 loads per day.

Table 6 : Computation results on Specific Fuel Consumption (SCF), Percentage Heat Utilization (PHU), Power Output & Burning Rate

Note: Variable cost and revenue is computed based on per load basis; additional information is located in the following income statement.

IV. CONCLUSIONS AND RECOMMENDATIONS

• Although data on fuel cost and efficiency of fuelwood salt stoves were not collected, rice hulls fed salt stoves are far more profitable because of the very minimal cost of fuel. Fuel accounts for only 11.6% of the total variable cost. Moreover, rice hulls are an agricultural by-product and their utilization reduces a possible source of pollution. By comparison, wood cutting for fuel in industrial stoves enhances deforestation, erosion, and environmental degradation.

• The rice hull fed stoves used in salt making are generally highly efficient. They have a range of 25.7% to 32.19% percentage heat utilization (PHU) compared to other rice hull stoves which have 15–18% efficiency (as reported in the literature). However, the PHU presented is abnormally high. This could be explained by the test conditions: the data were measured when the stove body was already hot. The temperature of the water when poured into the pan is 30–32° C. It takes some time for the cook to haul the fuel to the stove and fill the pans. By the time they start firing, the water temperature is already 38–43° C because of the residual heat from the previous cooking. However, we decided to take data then because residual heat was the usual condition. Before the cooks retire late at night they fire the stove first so that it is very warm in the early morning of the following day. So, the stove is almost continuously fired for 6 days a week. The actual efficiency of the stove could not be assessed from a cold condition which is present only at the start of the week.

• Proper pans which are mounted in a level fashion will contain more solution and thus provide a higher salt yield. With the 3 loads per day of 12–16 hours of work per day, the additional salt yield makes the enterprise significantly more profitable.

• Based on the computation of the PHU, the Specific Fuel Consumption, Power Output, Burning Rate and Time Consumed till Salt Harvest, this study concludes that stoves C & D are superior to stoves A & B. The main difference is in the design of the channel going to the chimney. In stoves C & D, the bottom of the channel inclines upward creating an updraft. Secondly, from the top view, the channel widens after coming from the rectangular body of the stove and tapers towards the chimney. This creates a higher air draught adapted to intense firing for quick cooking. In contrast to stoves A & B, the neck channel going into the chimney is straight and of the same size as the chimney. In stoves C & D, the grates also have a wider surface area over which to heat the pan. In the case of A & B, the intense fire heats the end of the pan near the fuel hopper, and has a lower surface area contact. If the pan is fired more intensely, there is a tendency for the water being boiled to spill.

• It is therefore recommended that:

  • Information drives should be done to encourage salt makers using wood as fuel to shift to rice hulls where-ever rice hulls are available.

  • Technical information should be made available for existing rice hull stoves emphasizing the importance of proper mounting of pans, the position of the grate, the influence of tunnel design on air draught strength, and the modification of fuel hoppers which include control valves to make the feeding of fuel less laborious.

  • Environmental controls should also be legislated for rice hull ash disposal. Information should be disseminated on the value of rice hull ash in compost making and as soil conditioner in its ash form. It is highly effective in improving soil structure as already demonstrated by the author of this study.

  • Finally, this study is preliminary and merits follow-up research.^₦

B. STOVES FOR SMOKED FISH MAKING

Hil J. Padilla
AGTALON
2430, Pangasinan
Philippines

1. BACKGROUND

“Galunggong”, a variety of mackerel fish, is one of the cheapest fish items in the Philippines. It is widely available and is the staple fish for poor Filipino families. It was not surprising then that the famous president of the Philippines, Corazon Aquino, made the price of “galunggong” the indicator for her economic program of improving the plight of the poor. Galunggong is the main variety used for smoked fish making since it is the most affordable and hence, the most marketable.

This study was conducted in a town where there are approximately 28 “tinapahan” or smoked fish processing centers. They process an average of 16 “banyeras” daily per processing center with 50 kg of fish per “banyera” or vat. This means around 22.4 tons of fish are processed daily. One processing center employs an average of 15 workers in addition to the owners who intermittently participate in the work or act as supervisors and administrators. The industry also includes wholesale traders and retailers of smoked fish and fresh fish traders. So, one can imagine the employment benefits derived from this particular industry.

Smoked fish making flow diagram

Smoking preserves the fish. Fisher folks prize this industry because it provides them with market even during times when there is high volume of catch resulting in an oversupply of fish. Smoked fish enables households in remote places who have no refrigerator nor a means of storing or preserving fish to stock fish for some time without spoilage.

The processing of smoked fish utilizes sawdust and sugar cane “bagasse” (waste from sugarcane mills) as fuel, and thus helps in the properly dispose and manage wastes from other local industries.

However, some people resist eating smoked fish because of reports that it causes cancer. Also, some manufacturers use formalin to increase the shelf life of the fish. There has been consumer concern about the high dosage of formalin used in fish processing.

Moreover, the processing centers which are situated in residential areas are too smelly and are the subject of complaints in the community. Fish entrails which are not currently utilized as feed for animals compound the pollution problem.

The stoves used, although much improved from the open type of stoves, are still very inefficient and could still be improved further. The area, where fish are smoked, is also naturally too smoky for the workers.

II. THE STOVE

2.1. The Design of Stove

The stove used for fish processing was developed in response to problems with the open type of stove. The open flame stove made the cooking area too hot for the cook, consumed a lot of fuel, and was viewed as unstable and therefore unsafe. Modifications include the addition of a chimney reduce smoke exposure, the enclosure of the firebox to reduce excess heat, and the construction of a concrete stove body which is more stable. A second pot hole was also added to the new design.

The workers are preparing the baskets for the smoking process

Typical stove used for smoked fish processing

The cooking stoves are made from cement and iron bars as reinforcements (as in building constructions). Concrete masons that are available locally are hired for the job. Clay is not feasible, since there is a high amount of water dripping from the boiled fish which would erode the stove body. Fired clay is not also feasible since the stove body is too big to be fired.

Very few processors line the stove walls with clay bricks. However, the lining could improve the stove's efficiency.

The bottom of the stove is made of earth. Usually, the chimney is made of B.I. pipe or fired clay. However, these materials are not durable. Concrete blocks could be used instead.

2.2. Problem With the Stove

The main problem with the “tinapahan” cooking stove is the high amount of fuel consumption as seen from the enclosed pictures. A lot of heat comes out of the firebox entrance. This heat makes the working condition very uncomfortable. The workers said that they have to change their shirts 5–6 times daily because their shirts become quickly saturated with sweat. Since the workers are paid by their work output, they create a very intense, hot fire to bring the water to a boil as fast as possible.

The problem stems from the very wide firebox entrance and the small diameter of the chimney which reduces the draft. Actually, the chimney of the stove studied, which is made of metal, was worn out and has been removed. Chimney durability could be improved by using concrete blocks for its construction as in the photo beside.

The concrete block chimney

They used the “banyera” made of flat metal sheet as a cooking pot or vat. The pots were installed with only the bottom exposed to the flame. The sides of the pot are in contact with the stove body. Heat transfer to the pot could be increased by hanging the pots by the rim only and thereby increasing the surface area in direct contact with the flame. A recent innovation is the use of a long cooking pan made of 16 gauge stainless steel. Since it is long (with no spaces in between), they could cook more. It also has higher rate of heat transfer. However, it costs more at P4,000 per unit as compared with a banyera which costs only P240 for 2 pots.

An improved stove, with enclosed firebox and chimney

2.3. The Smoking Vats

The smoking vat is made of ceramic. It is shaped like a big pot with iron bars put across the top from which small baskets of fish are hung.

The smoking vat is filled with burning charcoal taken from the other stove (stove for boiling). On top of the charcoal they put sugar cane bagasse and saw dust to generate smoke. The baskets of fish are then loaded into the smoking vat and covered with plywood.

2.4. Main Problem With the Smoking Vat

The main problem with the smoking vats is the very, very large amount of smoke created. Prolonged cooking for 10 – 14 hours can render the cook partially or temporary blind. This could be alleviated by installing smoke hoods on top of the smoking vats to draw out the smoke. The building's roofing should also have exhaust baffles as pictured below.

The second problem is the poor durability of the smoking vats which are made of ceramic. They very expensive now (P 800–1200 per piece). An alternative which is now being used by other processing units are vats made of concrete. They are cheaper and more durable.

III. FUEL USED

The fuel used for boiling fish is wood. One jeep load of fuel which is 5 m³, costs P1,200 (if delivered). Big trunks, 4 to 12 inches in diameter and 1 meter long, are used. This may explain why the firebox entrance of the stoves is so wide. Wood is preferred over rice hulls as fuel for 2 reasons: a) the charcoal from woodfuel can be used as a fire source for smoking; and b) wood produces less ash and hence creates less of a waste disposal problem. The wood consumption is 10 m³ per month.

The ceramic smoking pots	Exhaust baffles at the buliding's roof
Sugarcane bagasse and sawdust used to generate smoke	The bagasse are chopped into 6 inches before loaded to the smoking pot

The fuel used in smoking is sugarcane bagasse and sawdust. Sawdust costs P4 per sack. Sugarcane bagasse (waste from sugarcane mills) costs P1,000 per jeep load which is estimed to be around 5 m³ It is chopped into 6 inch lengths. One jeep load of sugar cane bagasse is consumed per month

IV. STOVE EFFICIENCY

The stove efficiency (Percentage Heat Utilization) was computed using the following formula and constants;

4.1. Test Results and Computations for Smoke Fish Making Stove:

Test conditions:

• The ambient outdoor temperature is 30° C
• The stove was last used 5 hours ago, it is still hot
• The 2 pots in the 2 pot holes were each filled with 15 kg water
• The water boiling test was conducted for 1.5 hours
• 2 replicates were taken with the same test conditions

Computation :

The results of the computations show that the stove used in smoked fish making is quite inefficient. By comparison, an improved wood fuel cookstove used in mushroom spawn making was also tested.

Note: The efficiency of the smoking vats was not tested for practical reasons: a) one could not conduct water boiling test; b) the amount of fuel consumption is not very significant.

4.2. Test Results and Computation for Mushroom Spawn Stove:

Test Condition:

• The ambient outdoor temperature is 29° C
• The stove has not been used for more than 1 week
• Only one pothole was utilized
• The water boiling test was conducted for 1 hour 15 min
• 2 replicates were taken under the same test conditions

Computation:

The stove for mushroom spawn production, even with only one pot hole, is more efficient than the stove used for smoking fish. The reasons for the higher efficiency are as follows ;

• The pot is hung in a way which allows more surface area to be in direct contact with the flame
• The smaller firebox entrance prevents heat from escaping from the fuel entrance
• Better up draft due to better chimney
• The use of baffles and dampers. The upright firebox entrance also results in better control of the fire and less attention to the stove as the fuel goes down by itself.

THE PRODUCTION PROCESS OF TINAPA OR SMOKED FISH

1.	The fish are thoroughly cleaned. If fresh, the fish entrails are left intact. If not, the entrails are removed.	2.	The fish are soaked in brine solution (1 part salt + 2 parts water) until the eyes of the fish become white. This takes approximately 30 minutes.
3.	The fish are then arranged in a bigger basket used for cooking. Weights are put on top of the basket so the fish won't float during cooking	4.	The fish are boiled in the brine solution for 5 minutes if the water is already boiling. After every 100 kg, 4 liters water and 2 liters of salt are added to the brine cooking solution.
5.	A smaller basket is used to hold 10–12 pieces of fish for the smoking process.	6.	The baskets loaded with fish go to the smoking area. The smoking vat is filled with burning charcoal from the stove boiler topped with sugar cane bagasse and sawdust to generate smoke. The baskets are then loaded into the smoking vat and covered with plywood.
7.	After smoking for about 30 minutes, the smoked fish is sprayed with yellow food coloring depending on the preference of the customers. If the customer does not like food coloring then thissteped.	8.	The smoked fish is aired to cool off before packing. If packed while still hot, fungus will be produced.

V. ECONOMIC ASPECTS

5.2. Durability

The stove was already 5 years old and still workable except for the B.I. pipe chimney which wore out after 4 years.

5.3. Economic Efficiency

2. Variable Costs

Note: The costs will be computed based on 10 banyeras = to 500 kg, then this will later be multiplied by the production rate for easier computation.

Note: Based on the calculations and experiences of the manager, he spends P200/banyera which comes close to the estimate above. The manager provides free meals to the workers as an added benefit. Usually, 2 meals are provided per day including snacks. But if they work overtime, they will be provided with 3 meals per day. The household of the manager does the cooking.

Since they are processing 15 banyeras per day, the income of the manager comes to P 6,108 daily.

VI. CONCLUSIONS AND RECOMMENDATIONS

The main problems in the smoked fish making industry are as follows:

• The inefficient stove (16% PHU), which results in high fuel consumption and very hot working conditions.

• The pollution caused by the high amount of smoke from the smoking vats and the cooking stove.

• The durability of the smoking vats made of ceramic material.

• The unsanitary condition of the processing centers. There are so many flies that when one sees the production site, one would rather not eat the smoked fish. Although, the production site under study has good sanitation, there is still much to be desired for the majority of the entrepreneurs.

• There is a lack of technical support for or access to information on alternative cookstoves and cooking techniques.

Our recommendations are as follows :

On Stove Efficiency

• Install chimney made of concrete blocks because it is the most durable, easiest to construct and most cost effective.

• The firebox entrance should be made narrower, or follow the design of the silkalan which registered an efficiency of 24%. The silkalan style also reduced the heat emanating from the firebox entrance which made the working environment more comfortable (please see attached photos on the next page). The attached Pogbi stove design could also be adopted.

• The use of long, stainless steel cooking pans instead of the 2 round pots. The long pan, cooks more fish and produces greater surface area exposure to the flame. The stainless pot is more durable because it doesn't rust. In the long run, if the durability is considered it is cheaper.

• The grate should be positioned in such a way that the flame heats the middle of the pan rather than the end of the pan. This allows more surface area for heat transfer with the higher intensity flame. Secondly, it will prevent spillage due to the turbulent boiling at the end part of the pan.

• Baffles and dampers should be installed.

• The inside walls should also be lined with ceramic bricks to increase heat insulation.

On Pollution

• The installation of a smoke hood extractor above the smoking vats.

• The installation of a chimney that goes up above the roof in the cooking stove.

• The roof in the working area should be constructed in such a way that smoke can escape.

On Smoking Vat Durability

• The use of concrete instead of ceramic vats should be promoted.

On Sanitation

• Installation of screens in the walls of the building to prevent flies from coming in.

• Utilization of fish entrails as feed for animals to solve waste disposal and avoid attracting flies. Stricter sanitation monitoring by the municipal government.

Others

• The introduction of the commercial GLM smokehouse and dryer should be assessed.^₦