Fuel and Emission Eciency test for locally produced charcoal stoves using charcoal sourced from selected tree species in Adola Woyu District, Ethiopia

Background: Energy plays an indispensable role in social, and economic development. It is 13 primarily obtained from biomass and converted to required energy using traditional stoves in most 14 developing countries. Currently, the market is dominated by different shapes and sizes of locally 15 produced cooking stoves. Their impact on fuel-saving, and emission reduction, however, has not 16 been exhaustively investigated. Objective and Method: Hence, the objective of this study is to test the fuel efficiency and emission 18 reduction potential of locally produced charcoal stoves. Accordingly, four charcoal stoves and 19 three plant species that are commonly used were collected for conducting laboratory tests following a controlled cooking test. 21 Results: The overall findings revealed that about 62.69% of the respondents use locally produced 22 charcoal stoves compared to the traditional metal stoves (37.31%). However, individual stove- 23 wise analysis indicates that traditional metal stoves are majorly used stove type followed by Lakech (29.36%) and Mirchaye (13.46%) stoves. Overall, a traditional metal stove consumes a 2 huge amount of fuel (0.23ton/year) which is around 0.0046ha of forest and is responsible for the 3 emission of 77.07ton of CO 2 e per year whereas the mean consumption of improved stoves is 4 0.16ton/year which is about 0.0032ha of forest and emits 13.69tons of CO 2 e per year. 5 Furthermore, these differences were among improved stoves. Accordingly, the highest annual 6 greenhouse gas emission was recorded by Mirchaye stove (14.64ton of CO 2 e) followed by lakech, 7 and kib stoves 13.69, and 12.74ton CO 2 e respectively. The types of wood used for charcoal 8 preparation, in addition to stoves types, also have an impact on the amount of fuel consumed and 9 pollutants emitted. Conclusions: Generally improved stoves significantly contribute to reducing emission and fuel 11 consumption which in turn reduces the impact on forest resources, human health, and global 12 warming of the energy sector. Hence, this finding discloses the distribution of these improved 13 stoves for local communities by government and concerned stakeholders to assure affordable and 14 clean energy for all and reducing pressure on forest and human health.


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Energy has a multitude of implications and plays an indispensable role in social, and economic 18 development [1], [2]. Currently, at the global level, more than three billion people rely on biomass 19 energy sources for different socio-economic activities [3], [4]. Subsequently, the global energy 20 demand is increasing by 4.6% in 2021 [3] and is expected to continue to mount in the coming 21 decades with increasing population, industries, and expansion of energy-dissipating economic 22 activities [3], [5]. However, the types of energy resources and demand vary from continent to affirmed that improved cooking stoves have the potential to reduce fuelwood consumption, wood 1 collection time, tree feeling, and emission of a pollutant that poses serious health impact [24] in 2 the short term and greenhouse gas (GHG) emission in long term. However, due to the cost of 3 improved stoves, community awareness, technical and financial requirements, nationally the 4 development and dissemination of standardized improved cookstoves, particularly charcoal 5 stoves, throughout the country were not effective. Considering the high demand and financial 6 income obtained from the production of stoves, different people and small-scale business 7 organizations had been engaged in the production of charcoal stoves. Consequently, different 8 shapes, sizes, and designs of stoves had been penetrating the local market without checking the 9 standard and quality of their stoves. Even though such engagements from private, small-scale 10 business owners and individuals would increase assess and affordability of the stoves; still there 11 is little empirical evidence associated with their fuel use efficiency and greenhouse gas emission 12 reduction potentials relative to the traditional metal charcoal stoves. Therefore, the objective of 13 this study is to test the fuel efficiency and emission reduction potential of three locally produced, 14 widely available, and commonly used charcoal stoves ("lakech", kib, and "Mirchaye") compared 15 to traditional metal charcoal stoves using charcoal produced from three selected tree species 16 dominantly used for charcoal production in the study area following controlled cooking test.

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Description of the study area 19 The study was conducted in Adola district of Guji zone, which is located in the central rift valley  The district is characterized by forest cover (Anferara forest) which is a remnant natural forest 1 resource that faces great pressure from the surrounding community for charcoal production and 2 other fuelwood energy sources. 3 Description of stoves 4 The traditional metal charcoal stove (Figure 1b) is the most common and widely used stove for 5 cooking in most parts of urban and semi-urban Ethiopia. It consists of a combustion chamber, 6 grate, pot rest, and primary air opening. All its parts are only made of metal and hence, simple that outer coverage including grate and pan seat is made of metal sheet whereas the internal wall is 10 from clay. Even though their size and design vary, they all have combustion chambers and grates.

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Mirchaye and Kib stove have pan seats. However, the pan seat of Mircheye is made of metal that 12 is internally fixed to a metal sheet whereas that of the Kib stove is made of clay that is internally 13 attached to the clay wall of the stove. These stoves were purposively selected since they are easily 14 available in the local market and are dominantly used by most of the respondents in the study area. 15 Accordingly, traditional metal stoves were used as a control for comparison. To conduct laboratory analysis and collect the required data, a digital balance with 0.01gm 6 accuracy, digital thermometer with thermocouples, charcoal fuel, sauce ingredients (mitin-Shiro, 7 onion, edible oil, salt, and water), stopwatches, heat resistant hand gloves, charcoal pans, spatulas, 8 measuring tape, wot cooking pot (25cm diameter), emission measuring device, and infrared 9 thermometer were the equipment and materials used during CCT test.

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Data was collected from a controlled cooking test (CCT) test, which is carried out in Addis Ababa 12 Laboratory of Alternative Energy Development and Promotion Center, using charcoal derived 13 from three different plant species and stoves. The CCT was conducted to evaluate the fuel use 14 efficiency/performance and emission reduction potential of the commonly used locally produced charcoal stoves (Mirchaye, Lakech, and Kib) relative to the traditional metal charcoal stove. To collect appropriate data, before testing, three experienced women were selected as a cooker of 4 the wot/sauce and well-oriented about the procedures of the test in such a way that both testers and 5 cookers can understand and follow each other. The role of the testers during the cooking session 6 was only to record the data and do observations without any interference to the cookers. 7 Accordingly, during each test, data related to the mass of charcoal (before, and after each test), 8 moisture of charcoal, time the stove lit (fire catches), time at which the test ends, the mass of food 9 cooked, the mass of sauce ingredients (Shiro, onion, water, salt), air temperature, the weight of the 10 charcoal container and cooked food were recorded and entered to a spreadsheet for calculation. region. Before proceeding with cooking, the moisture content of charcoal samples was analyzed 2 using an oven heater and their average moisture contents range from 7.5 to 12.0%. Match and 3 kerosene were used for lighting, and paper and wood sticks were used for starting the fire. After 4 each test, the remaining charcoal was weighed.

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Efficiency calculation 6 In this study, the calculation of cookstove's efficiency was done following the formula of [25]. 7 Accordingly, the specific fuel consumption (SFC) which is the principal indicator of stove 8 efficiency and measures the amount of wood used per kg of food is calculated as: Where SFC is specific Fuel consumption, fd is Equivalent Dry Wood consumed and Wf is the total 11 weight of cooked food. The number 1000 is a conversion factor for grams of fuel per kg of food 12 cooked.

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The variables fd and Wf are computed as; Where j is an index for cooking pot ranging from 1-2, Pjf is the weight of each pot with cooked  For testing Emission from the stoves, an emission testing hood was employed. Accordingly, the 5 charcoal stoves were placed in the hood, and then the flue test analyzer probe was inserted into the 6 hood through the sensor inlet pore to detect the CO, CO2, NO, NOX, etc. The tester logs the data 7 automatically at specific intervals. For these tests, the data was logged in 5minutes intervals. The 8 analyzer has an accuracy of ±20 ppm CO with a measuring range (0-4000ppm CO) and 1 ppm 9 resolution. The reaction time for the analyzer is approximately 40sec. After data related to CO2, 10 CO, NO, NOx has been collected, since their global warming potential is different, the CO2e of 11 each greenhouse gas was calculated as follows: 12 CO2e = GWPi * GHGi ……………………………………………………. Equation5

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Where: GWPi is the global warming potential of each gas (relative to CO2), and GHGi is the 14 quantity of each greenhouse gas emitted. 15 Finally, for calculating the greenhouse gas emission reduction potentials of each improved 16 charcoal stove under investigation relative to the traditional metal stoves the following equation The data analysis was made using statistical package for social science (SPSS) version 20, and 2 Microsoft excel. Accordingly, the statistical differences in emission of CO2, CO, NOx, and NO 3 and specific charcoal fuel consumption were computed using multivariate analysis and analysis of 4 variance at a 5% significance level. Other descriptive statistics like percentage, mean and standard 5 deviation were also calculated for quantitative data. Finally, tables, figures, and pie charts were 6 used for summarizing and displaying the findings. were not yet adopted appropriate charcoal stoves due to lack of availability in the market 1 and distance to the market. During focus group discussion, the respondents were also stressed that 2 all the above-mentioned charcoal stoves are not produced in their surrounding area rather obtained 3 from other large cities like Addis Ababa, Awassa, and Shashemane. On top of this, they stated that 4 the stoves available in the market also varied in shape, size and durability and majority of them 5 were not produced as per the stove standard. The result of household survey analysis also showed that major (65%) respondents use charcoal 18 as a source of energy for household cooking like cooking 'woat', boiling coffee, and house heating.  The overall result of this study showed that the highest mean charcoal fuel consumption (0.288kg) 3 was recorded by traditional metal charcoal stove followed by 'Kib' stove (0.201Kg) and The overall result of the analysis affirmed that the stoves used by the respondents contributed to 4 32.33% charcoal fuel-saving relative to traditional metal stoves as indicated in Table 3   The overall result of analysis of variance and descriptive statistics showed that there was a 8 significant difference (p < 0.000) in specific charcoal fuel consumption among the stove types 9 under investigation (as indicated in Table 6 and More interestingly, the specific charcoal fuel consumption of the stoves under investigation also 5 differs based on types of charcoal fuels which is related to the types of wood plants used to produce 6 the fuel as indicated in Figure 5 below. Accordingly, traditional stoves consume more charcoals 7 fuel produced from Syzygium guineense ( 129 g) followed by Olea capensis (126g) and Allophylus 8 abyssinicus (121g) per cooking session. The possible contributing factors for higher consumption 9 of Syzygium guineense might be due to its lower heating/calorific value relative to other charcoal 10 fuels like Olea capensis (7262.3 cal/g) and Allophylus abyssinicus (6728 cal/g) as indicated in 11 Table 4 below. The other possible reason might be its higher ash content (7%).

Carbon dioxide (CO2):
The result of multivariate analysis (Table 7 below) also showed that there 8 was a statistically significant (P = 0.000) mean difference in mean carbon dioxide emission from 9 stoves under investigation. The highest (18%) percentage of variation (differences) in the amount 10 of carbon dioxide emission was attributed due to the types of stoves used by households (Table 8).

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Accordingly, as indicated in figure 8 below, traditional charcoal stoves emit a significantly higher 12 amount of carbon dioxide as compared to improved stoves considered for this particular study.  the potential to reduce emissions that can also contribute to reducing acute respiratory infection, 2 lung cancer and eye irritations. 3 The percentage emission reduction analysis result showed that among improved stoves, the kib 4 charcoal stove emits lower amounts (11,496.67ppm) of carbon dioxide as compared to other 5 charcoal stoves. On the contrary, the traditional charcoal stove relatively emits a very high amount 6 of carbon monoxide. In other words, among locally produced improved stoves under 7 consideration, the kib stove has a higher potential (83.12%) to reduced carbon dioxide emission 8 followed by Lakech and Mirchaye stoves (Table 9).  (Table 8). The stove types also contribute to a difference in the emission of 3 carbon monoxide difference even though its percent share is lower (10.9%) compared to what has 4 been mentioned. Accordingly, as indicated in figure 9 below, the traditional metal charcoal stove 5 emits significantly much higher amount of carbon monoxide relative to other charcoal stoves under Mirchaye stoves respectively. In other words, in terms of their emission of carbon monoxide,

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Lakech stove < Kib stove < Mirchaye stove < traditional metal charcoal stove as indicated in figure   13 9 below. This means that relative to traditional charcoal stoves, Lakech stoves have the highest 14 potential to reduce the emission of carbon monoxide per household's cooking activity. Kib and 15 Mirchaye also have the highest carbon monoxide emission reduction capacity as compared to 16 traditional stoves. Furthermore, they have a great contribution in reducing indoor air pollution and 17 other health-related problems with exposure to carbon monoxide.  The value of partial Eta squared showed that about 43.1% of the variation in nitrogen oxides 4 emission is due to the types of wood plants species used as charcoal fuel as indicated in Table 8,   5 below. Additionally, the types of charcoal stoves (32.7%) used by itself were also contributed to 6 the difference in emission. Figure 10 below also shows that similar to carbon dioxide and carbon 7 monoxide, traditional metal charcoal emits a higher amount of NOx's followed by Mirchaye stove 8 whereas kib stove emits relatively very low.

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The types and efficiency of stoves used by households have a considerable impact on charcoal fuel 4 consumption. The findings revealed that traditional charcoal stoves consume a huge amount of 5 fuel when compared with locally produced modified stoves. Furthermore, there was a difference 6 in emission and fuel-saving between traditional metal stoves and improved stoves that are 7 considered in this study. There were also differences in terms of fuel consumption, fuel-saving, 8 and greenhouse gas emissions among improved stoves. Furthermore, the types of wood used for 9 charcoal preparation, in addition to stoves types, also have an impact on the amount of fuel 10 consumed and pollutants emitted. Generally, this implies that improved stoves have a great 11 contribution in reducing the impact on forest resources, health impacts of indoor air pollution and 12 global warming from the energy sector. Hence, this finding discloses the distribution of these 13 improved stoves for local communities by government and concerned stakeholders so that it 14 enables to assure the objectives of sustainable development goals associated with the provision of 15 affordable and clean energy technologies.

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Ethics approval and consent to participate 18 This research is not associated with humans or part of human participation/involvement. Hence, The article is original, has not already been published in a journal, and is not currently under 1 consideration by another journal. 3 The authors declare that they have no competing interests.  Author's contribution 8 Both the first (GD) and second authors (AD) were involved in the inception of research ideas, data 9 and collection. Moreover, the first author (corresponding author) was also involved in data 10 analysis, interpretation, manuscript development and editing.

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Availability of data and materials 13 The datasets used and/or analyzed during the current study are available from the corresponding 14 author on reasonable request.

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Acknowledgment 16 We would like to thank MRV project office for their financial support during data collection. At 17 the end, but not the least, we also acknowledge the head of the