Fuel sources for cooking/baking stoves
Figure 3 presents the descriptive statistics of the fuel sources used in the Zenzelima kebel. Out of the 60 sample households interviewed, most used biomass solid fuel sources for baking and cooking. In terms of fuel utilization, the data show that the households were used in descending order of firewood, crop residues, dung, and charcoal, and their percentage shares were 50%, 25%, 16.7%, and 8.3%, respectively. Electricity, gas, and kerosene were not utilized by societies for cooking/baking, unlike for biomass energy, but rather for lighting purposes. From this figure, biomass energy is the dominant energy source in the community for the cooking/baking process.
Naturally, rural consumers, including rural households, collect their traditional fuel supplies freely in their surroundings. However, depending upon accessibility (both physically and financially) and the degree of commercialization of traditional fuels, some households may purchase traditional fuels from the market. The results of the baseline survey confirm this line of argument.
The results of the survey also revealed that there is a negative correlation between traditional fuel availability and the amount of time required to freely collect fuels.
As indicated in Fig. 4, less than 10% of the freely collecting households in areas with a relative abundance of traditional fuels reported that it takes approximately one hour to collect their fuels, and the proportions reach 41% in areas where woody biomass resources are scarce and far from locals. Increasing land clearing for agriculture and growing demand for cooking fuels (both are needed to feed a growing population) were cited by households as the two most important reasons for the scarcity of traditional fuels. For that reason, some societies purchased fuel from the market.
Stove efficiency
Several reports indicate that the efficiency of cooking technology is 10%, 25%, 48%, 50%, and 54% for open fire, lakech, mirt, gonze, and tikikil, respectively [23, 24]. However, the efficiency of the pyrolysis stove is approximately 76%, as determined experimentally in our previous study. The performances of the 3-stone and mirt stoves were determined in the laboratory, and the results were in good agreement with the literature values. Figure 5 indicates that the efficiency of the pyrolysis stove was the highest, and the open fire stove was the least efficient. The efficiencies of the other stoves were between these two ranges.
Cooking time
As shown in Fig. 6, the cooking/baking time of the 3-stone stove was the highest, and the pyrolysis stove cooking/baking time was the lowest. This showed that open-fire stoves need more cooking and ignition time to cook or bake than other stove types due to energy loss and uncontrolled wind. Lakech, mirt, gonze, and tikikil have shorter cooking times in descending order. As the cooking time increases, fuel consumption also increases, which results in rising fuel costs and a high deforestation rate.
Fuel consumption during cooking/baking
Firewood, crop residue, and charcoal are the three most significant cooking fuels that rural families often utilize in the Zenzelima kebel. However, households in wood-scarce areas tend to diversify their fuel mix more and use low-grade cooking fuels such as cow dung and tree leaves to a limited extent.
Table 2
No
|
Type of stove
|
Fuel
consumption
Per week (kg fuel/food/HH)
|
Fuel
consumption
Per month (kg fuel/food/HH)
|
Fuel
consumption
Per year (kg fuel/Kgfood/HH)
|
|
|
cooking
|
baking
|
cooking
|
baking
|
cooking
|
baking
|
1
|
3-Stone
|
30.43
|
45.99
|
121.72
|
183.96
|
1460.64
|
2207.52
|
2
|
Lakech
|
22.4
|
|
89.6
|
|
1075.2
|
|
3
|
Mirt
|
|
19.95
|
|
79.8
|
|
957.6
|
4
|
Gonze
|
|
12.5
|
|
50
|
|
600
|
5
|
Tikikil
|
|
10.08
|
|
40.32
|
|
483.84
|
6
|
pyrolysis
|
3.36
|
|
13.44
|
|
161.28
|
|
The results of the study showed that, by using 3-stones, rural households in the Zenzelima kebele consumed the most fuel consumed−2207.52 fuel/kg dough per household per year in 2 shifts per week for baking injera and 1460.64 kg fuel/food per household per year for cooking purposes in 4 shifts a day—and by using pyrolysis stove, they consumed the least amount of fuel consumed−161.28 kg fuel/kg food per household per year for cooking purposes in 4 shifts a day, as shown in Table 2.
Based on the findings of actual fuel consumption measurements in survey households, cooking energy consumption for rural households in the Zenzelima kebele by using 3 stones is estimated to be 141.250.7 tons of wood equivalents per annum. This indicated that a high degree of deforestation is occurring due to the cutting down of trees for firewood by societies in the kebele.
According to the results of the study, firewood, crop waste, and dung are the three primary sources of energy commonly used by rural households in the Zenzelima kebele.
From this study, approximately 75% of the cooking energy consumed by rural households in the Zenzelima kebele was firewood, as shown in Fig. 7. With a 15% contribution to household cooking fuel consumption, crop waste comes in the next place, and dung (6%) in the third place. Additional energy sources, such as charcoal and leaves from tree leaves, were also used where wood scarcity was high.
Fuel consumption also depends on the efficiency of cooking technologies. As shown in Fig. 8, the open fire stove was the highest fuel consumer, and pyrolysis was the least fuel consumer stove. The fuel consumption of other stoves was between those of the other stoves. This means that improved cookstoves use less energy to cook the same quantity of meals than customary, open-fire, stoves. Additionally, the pyrolysis/gasifier type has the least impact. Therefore, the pyrolysis/gasifier stove type was the better type for fuel consumption or for reducing the deforestation rate.
Impact of cook stove smoke on health
It is estimated that approximately 3 billion people worldwide rely on wood, stubble, dung, and leaves for cooking fuel. Numerous dangerous contaminants are released when biomass fuels are burned over open flames or in ineffective stoves [25]. Women and children who inhale these contaminants have increased respiratory morbidity and death [26]. The amount of indoor air pollution decreases when households utilize upgraded stoves [27]. It is crucial to determine the knowledge of the negative health effects of indoor air pollution and readiness to change before attempting to intervene to lessen the health effects of biomass cooking smoke.
As shown in Table 3, the smoke release level from the 3 stone stoves in the 60 households surveyed was very high when compared to that from the other stoves due to direct burning and open fire systems. However, the smoke released by the Lakech, mirt, Tikikil, and Gonze stoves was at a medium level due to improvements in their efficiency. Moreover, the pyrolysis stove efficiency is superior to that of the stoves that are currently in use in Ethiopia, resulting in a low level of smoke release. The pyrolysis stove does not directly complete burning and releases combustible producer gases such as H2 and CO through a limited oxygen pyrolysis process. These gases are then burned completely without emitting any environmental pollutants. For a lake-type stove, the fuel source is pure charcoal, and the stove does not release too much smoke. Mirt, Tikikil, and Gonze stoves are not included in the complete buying process. They are partially oxidized, and the smock levels are intermediate.
During the survey in the household, the women told us that they were suffering from smoke, as shown in Fig. 7. This smoke resulted in breathing problems, soot on the ceiling and wall of the house, and inching of the skin and eyes of the family, especially mothers and children who cooked/baked with that type of stove.
Table 3
Impact of cooking stoves on the health and education of the selected site area (Zenzelma kebele) societies
N0.
|
Type of stove
|
Kebele Household(N = 60)
|
Smoke release
|
Burden to
|
Fuel collection
|
Ignition
|
Fuel inserting
|
Education
|
1
|
3 stone
|
23(38.3%)
|
Very high
|
Very high
|
Very high
|
Very high
|
very high
|
2
|
Lakech
|
7(11.6%)
|
Medium
|
Medium
|
High
|
Low
|
Medium
|
3
|
Mirt
|
19(31.6%)
|
Medium
|
High
|
Low
|
Medium
|
Medium
|
4
|
Gonzeye
|
3(5%)
|
Medium
|
High
|
Low
|
Medium
|
Medium
|
5
|
Tikikil
|
6(10%)
|
Medium
|
Medium
|
Low
|
Medium
|
Medium
|
6
|
pyrolysis
|
2(3.3%)
|
Low
|
Low
|
Very low
|
Very low
|
Low
|
As the efficiency of the cooking stove decreased, the burden of fuel collection, ignition, and fuel insertion increased, as shown in Table 1. The challenge with gasoline collecting had to go long distances, and they may have also been injured by insects and may have been raped. The burden of education for 3 stone types is very high due to the high consumption of fuel, especially for children; instead of attending their classes and studying, they spend their time cooking/baking, collecting fuels, igniting and fuel inserting fuels, and sometimes their health is affected by smoke, as demonstrated in Fig. 9. Therefore, they cannot attend their lesson properly. However, in the pyrolysis stove, there is no waste of time for fuel insertion and ignition in time intervals. The appropriate fuel wood is inserted once, and there is no need to insert fuel wood or ignite. During this cooking time, women and children can perform other work, including homework and other education studies.
Utilization of cook stove byproducts
Biochar, a soil amendment, has potential as a valuable tool for the agricultural industry because of its unique ability to help build soil, conserve water, produce renewable energy, and sequester carbon. By influencing important soil processes, biochar enhances the quality of soil. The vast surface area and very porous structure of biochar are the main sources of its advantages. High surface area charges can increase cation exchange capacity (CEC), thereby increasing a soil’s ability to retain and supply nutrients. Increased porosity can increase the soil's ability to retain water, and small pore spaces with positively charged surfaces can improve soil water retention and in turn reduce nutrient (P, K, Ca, Mg, phosphorous, and nitrogen) loss through leaching. Charcoal in soils has also been linked to increased soil microbial populations, which may increase beneficial soil processes mediated by soil organisms, including nutrient availability. Since most biochar does not increase the amount of nutrients that are accessible to the soil, it is better to think of it as a soil conditioner rather than a fertilizer. If biochar is to be useful for sequestering carbon, it must be long-lived and resistant to chemical processes such as oxidation to carbon dioxide or reduction to methane.
In this study, it was observed that traditional cookstoves produce little biochar and a large amount of ash from the cooking/baking process, and most societies cannot use the byproduct biochar for soil amendment. Simply, they discharged it to their surroundings. Some of these materials were used for compost purposes because of their soil fertility.
Since the existing cooking stoves involve direct burning, the char is also burned during the combustion process, and the char yield is low. However, pyrolysis/gasifier stoves produce combustible gas without direct burning of char, and the byproduct is pure biochar, which is crucial for soil amendment in former farmlands. Biochar is also used as charcoal in briquettes for cooking.
Cost analysis
The current prices of cooking/baking stoves in Ethiopia are shown in Table 4. Lakech has low prices, whereas Mirt, Gonze, and Tikikil have medium-range prices. If we look at pyrolysis stoves in terms of price, it seems highly costly compared to other stoves. However, considering the other advantages of pyrolysis stoves, they have many advantages, such as fuel efficiency, time efficiency, and useful byproduct production. The biochar produced from this pyrolysis stove can be used again for cooking, can reduce the cost of firewood, and can be sold to other customers for cooking and soil amendment purposes. Hence, these advantages outweigh the high cost of pyrolysis stoves in contrast to alternative stoves.
Table 4
Comparison of different stoves in terms of price
No.
|
Type of stove
|
Unit price (birr)
|
1
|
3-stone
|
Free
|
2
|
Lakech
|
80.00–120.00
|
3
|
Mirt
|
180.00–200.00
|
4
|
Gonze
|
150.00–180.00
|
5
|
Tikikil
|
220.00 -300.00
|
6
|
Pyrolysis
|
500.00–600.00
|
Estimation of Emission Reduction
For the estimation of emissions, the UNFCCC methodology for energy-saving techniques for thermal applications of nonrenewable biomass was used [22], as indicated in Eq. 1.
$${E}_{ry}{=B}_{y }(1- \raisebox{1ex}{${{\eta }}_{old}$}\!\left/ \!\raisebox{-1ex}{${{\eta }}_{new}$}\right.){f}_{NRB}NCV{EF}_{kerosene}$$
1
Where
Ery - Emission reduction per stove
By – Average quantity of biomass consumption by the household for cooking (or baking).
ηold – Efficiency of the stove being replaced
ηnew – Efficiency of the stove being deployed
fNRB – Nonrenewable fraction of biomass use
NCV – Net calorific value of biomass fuel
EFkerosene - Emission factor for the substitution of nonrenewable biomass
Estimation was made for injera baking and other cooking processes. To estimate the emission reduction, improved cook stoves with overall efficiencies of 10%, 25%, 48%, 50%, 54%, and 76% for open fire, lakech, mirt, gonze, tikikil and pyrolysis stoves, respectively, were used for the cooking and injera baking processes, as shown in Table 5.
Table 5
Estimation of emissions reduction per stove per household per year for cooking
No.
|
Estimation of CERs/VERs
|
Symbols
|
Values
|
Units
|
1
|
Percentage of nonrenewable biomass use in the Zenzelima kebele (estimated)
|
fNRB
|
60
|
%
|
2
|
Average fuel wood consumption by HHs
|
By
|
2.2
|
tone/hh/yr
|
3
|
The efficiency of stove being replaced
|
ηold
|
10
|
%
|
4
|
Efficiency of stove to be deployed
|
ηnew
|
Lakech
|
25
|
%
|
Mirt
|
48
|
Gonze
|
50
|
Tikikil
|
54
|
Gasifier
|
76
|
5
|
Net Calorific Value of biomass
|
NCV
|
0.015
|
TJ/tone
|
6
|
Emission factor for the substitution of nonrenewable biomass
|
EFkerosene
|
71.5
|
toneCO2/TJ
|
7
|
Emission Reductions per stove
|
Ery
|
3-Stone
|
0.142
|
toneCO2/hh/year
|
Lakech
|
0.849
|
Mirt
|
1.121
|
Gonze
|
1.133
|
Tikikil
|
1.153
|
Pyrolysis
|
1.229
|
From this study, it was observed that the emission reductions achieved by improved cook stoves are proportional to the efficiency of the cooking stove. As shown in Fig. 10, the gasifier/pyrolysis stove has a greater emission reduction capability than the other improved cook stoves. It reduced CO2 emissions by 1.229 tons per household per year. According to our sample study, 60 households could reduce CO2 emissions by approximately 73.74 tons per year, which is a very significant reduction in emissions and is very important for the carbon credit market. However, for the 3-stone stove type, the emission reduction is 0.142 tons of CO2 per household per year, which means that the reduction is very small compared to that of another type of stove; therefore, utilizing this type of stove is not recommended.
General linear model of the data analysis
The cooking stoves, fuel consumption, and cooking time were identified in this survey out of the 60 households listed as shown in Table 6. The figure indicates that, from the total sampling of 60 households, the number of households interviewed and observed are 23HH for 3-stone, 7HH for Lakech, and 19HH for Mirt and from secondary sources 2HH for pyrolysis, 3HH for Gonze, and 6HH for Tikikil. As indicated in Table 6, the greatest mean value stove type for fuel consumption and cooking time is 3 stones, which means that this type of stove utilizes more fuel and takes more time to cook than does another type of stove. On the other hand, pyrolysis stoves utilize less fuel and take less time to cook, so they have the lowest mean value. Therefore, the table indicates that the adoption of pyrolysis stove type is essential for minimizing the deforestation rate and saving time. Secondary data were collected for the analysis of the pyrolysis stove.
Table 6 Number of stoves in the survey households and descriptive statistics Between-Subjects Factors
|
N
|
Cooking technology
|
3-Stone
|
23
|
pyrolysis
|
2
|
Gonze
|
3
|
Lakech
|
7
|
Mirt
|
19
|
Tikikil
|
6
|
Descriptive Statistics
|
|
Cooking technology
|
Mean
|
Std. Deviation
|
N
|
Fuel consumption
|
3-Stone
|
3.1070
|
.63734
|
23
|
pyrolysis
|
.1100
|
.01414
|
2
|
Gonze
|
.4783
|
.15687
|
3
|
Lakech
|
2.2571
|
.64513
|
7
|
Mirt
|
1.1379
|
.55334
|
19
|
Tikikil
|
.8250
|
.59477
|
6
|
Total
|
1.9248
|
1.19011
|
60
|
Cooking time
|
3-Stone
|
5.5217
|
1.15284
|
23
|
pyrolysis
|
1.7500
|
.35355
|
2
|
Gonze
|
2.2000
|
.52915
|
3
|
Lakech
|
4.7143
|
.48795
|
7
|
Mirt
|
3.3526
|
.70029
|
19
|
Tikikil
|
2.7667
|
.25820
|
6
|
Total
|
4.1733
|
1.49846
|
60
|
Post hoc analysis between cooking technologies
The relationship between the cooking stove types is described in Table 7. As shown in Table 6, compared with other types of cooking stoves, the pyrolysis stove had significant differences in terms of fuel consumption and cooking time. The table shows the mean difference comparison of one cooking/baking stove with the other stoves in terms of fuel consumption and cooking times. For example, when we compared 3-stone cook stoves with other stoves in terms of fuel consumption and cooking time, a significant difference was detected for the pyrolysis stove, and the least significant difference was also detected for the lakech stove, as shown in Table 7.
Table 7
Post hoc analysis and multiple comparisons of cooking/baking technologies
Multiple Compariso
|
Dependent Variable
|
(I) Cooking technology
|
(J) Cooking technology
|
Mean Difference (I-J)
|
Std. Error
|
Sig.
|
95% Confidence Interval
|
Lower Bound
|
Upper Bound
|
Fuel consumption
|
3-Stone
|
Pyrolysis
|
2.9970*
|
.43456
|
.000
|
1.4960
|
4.4979
|
Gonze
|
2.6286*
|
.36184
|
.000
|
1.3788
|
3.8784
|
Lakech
|
.8498
|
.25445
|
.064
|
− .0291
|
1.7287
|
Mirt
|
1.9691*
|
.18274
|
.000
|
1.3379
|
2.6003
|
Tikikil
|
2.2820*
|
.27022
|
.000
|
1.3486
|
3.2153
|
Pyrolysis
|
3-Stone
|
-2.9970*
|
.43456
|
.000
|
-4.4979
|
-1.4960
|
Gonze
|
− .3683
|
.53810
|
.993
|
-2.2270
|
1.4903
|
Lakech
|
-2.1471*
|
.47262
|
.003
|
-3.7796
|
− .5147
|
Mirt
|
-1.0279
|
.43820
|
.371
|
-2.5415
|
.4857
|
Tikikil
|
− .7150
|
.48129
|
.818
|
-2.3774
|
.9474
|
Gonze
|
3-Stone
|
-2.6286*
|
.36184
|
.000
|
-3.8784
|
-1.3788
|
Pyrolysis
|
.3683
|
.53810
|
.993
|
-1.4903
|
2.2270
|
Lakech
|
-1.7788*
|
.40677
|
.005
|
-3.1838
|
− .3738
|
Mirt
|
− .6596
|
.36621
|
.664
|
-1.9245
|
.6053
|
Tikikil
|
− .3467
|
.41681
|
.983
|
-1.7864
|
1.0930
|
Lakech
|
3-Stone
|
− .8498
|
.25445
|
.064
|
-1.7287
|
.0291
|
Pyrolysis
|
2.1471*
|
.47262
|
.003
|
.5147
|
3.7796
|
Gonze
|
1.7788*
|
.40677
|
.005
|
.3738
|
3.1838
|
Mirt
|
1.1192*
|
.26063
|
.006
|
.2190
|
2.0195
|
Tikikil
|
1.4321*
|
.32795
|
.005
|
.2994
|
2.5649
|
Mirt
|
3-Stone
|
-1.9691*
|
.18274
|
.000
|
-2.6003
|
-1.3379
|
Pyrolysis
|
1.0279
|
.43820
|
.371
|
− .4857
|
2.5415
|
Gonze
|
.6596
|
.36621
|
.664
|
− .6053
|
1.9245
|
Lakech
|
-1.1192*
|
.26063
|
.006
|
-2.0195
|
− .2190
|
Tikikil
|
.3129
|
.27604
|
.934
|
− .6406
|
1.2663
|
Tikikil
|
3-Stone
|
-2.2820*
|
.27022
|
.000
|
-3.2153
|
-1.3486
|
Pyrolysis
|
.7150
|
.48129
|
.818
|
− .9474
|
2.3774
|
Gonze
|
.3467
|
.41681
|
.983
|
-1.0930
|
1.7864
|
Lakech
|
-1.4321*
|
.32795
|
.005
|
-2.5649
|
− .2994
|
Mirt
|
− .3129
|
.27604
|
.934
|
-1.2663
|
.6406
|
Cooking time
|
3-Stone
|
Pyrolysis
|
3.7717*
|
.63855
|
.000
|
1.5662
|
5.9773
|
Gonze
|
3.3217*
|
.53170
|
.000
|
1.4852
|
5.1582
|
Lakech
|
.8075
|
.37390
|
.467
|
− .4840
|
2.0989
|
Mirt
|
2.1691*
|
.26853
|
.000
|
1.2416
|
3.0966
|
Tikikil
|
2.7551*
|
.39707
|
.000
|
1.3836
|
4.1265
|
Pyrolysis
|
3-Stone
|
-3.7717*
|
.63855
|
.000
|
-5.9773
|
-1.5662
|
Gonze
|
− .4500
|
.79070
|
.997
|
-3.1811
|
2.2811
|
Lakech
|
-2.9643*
|
.69448
|
.007
|
-5.3630
|
− .5655
|
Mirt
|
-1.6026
|
.64390
|
.304
|
-3.8267
|
.6214
|
Tikikil
|
-1.0167
|
.70722
|
.837
|
-3.4594
|
1.4261
|
Gonze
|
3-Stone
|
-3.3217*
|
.53170
|
.000
|
-5.1582
|
-1.4852
|
Pyrolysis
|
.4500
|
.79070
|
.997
|
-2.2811
|
3.1811
|
Lakech
|
-2.5143*
|
.59771
|
.008
|
-4.5788
|
− .4498
|
Mirt
|
-1.1526
|
.53812
|
.477
|
-3.0113
|
.7060
|
Tikikil
|
− .5667
|
.61247
|
.972
|
-2.6822
|
1.5488
|
Lakech
|
3-Stone
|
− .8075
|
.37390
|
.467
|
-2.0989
|
.4840
|
Pyrolysis
|
2.9643*
|
.69448
|
.007
|
.5655
|
5.3630
|
Gonze
|
2.5143*
|
.59771
|
.008
|
.4498
|
4.5788
|
Mirt
|
1.3617*
|
.38297
|
.040
|
.0389
|
2.6844
|
Tikikil
|
1.9476*
|
.48189
|
.012
|
.2831
|
3.6121
|
Mirt
|
3-Stone
|
-2.1691*
|
.26853
|
.000
|
-3.0966
|
-1.2416
|
Pyrolysis
|
1.6026
|
.64390
|
.304
|
− .6214
|
3.8267
|
Gonze
|
1.1526
|
.53812
|
.477
|
− .7060
|
3.0113
|
Lakech
|
-1.3617*
|
.38297
|
.040
|
-2.6844
|
− .0389
|
Tikikil
|
.5860
|
.40562
|
.835
|
− .8151
|
1.9870
|
Tikikil
|
3-Stone
|
-2.7551*
|
.39707
|
.000
|
-4.1265
|
-1.3836
|
Pyrolysis
|
1.0167
|
.70722
|
.837
|
-1.4261
|
3.4594
|
Gonze
|
.5667
|
.61247
|
.972
|
-1.5488
|
2.6822
|
Lakech
|
-1.9476*
|
.48189
|
.012
|
-3.6121
|
− .2831
|
Mirt
|
− .5860
|
.40562
|
.835
|
-1.9870
|
.8151
|
Based on observed means. The error term is Mean Square (Error) = .750.
|
*. The mean difference is significant at the .05 level.
|
Curve fitting linear model
The relationship between fuel consumption and cooking time of the cook stoves is displayed in Fig. 11. The regression indicated that fuel consumption and cooking time had a linear relationship, as shown in Fig. 11.
Production process
The pyrolysis/gasifier/stove production process is simple and is now already designed, licensed, and manufactured by the Epro Green Energy Company. Therefore, to disseminate mass production for society, appropriate training and consultation will be given for those societies that manufacture and utilize this material. To manufacture, 15 days of training are needed, and 10 days of training are required for the utilization of the stove. The training and the consultancy will be provided by the Epro Green Energy Company.