Technical Potential of Biogas Technology Adoption in Replacing Firewood, Kerosene and Chemical Fertilizer: The Case of Misrak and Mirab Estie Districts, in Northern Ethiopia

Background: The depletion of bioenergy sources has caused signicant deforestation, low agricultural production and energy crisis. This study evaluates the technical potential of biogas technology adoption in replacing rewood, charcoal, kerosene and chemical fertilizer in Northern Ethiopia. Methods: Questionnaire household survey, key informant interview, focus group discussion and eld obervation were used for data collection. Results: Biogas technology adoption reduced the use of rewood, charcoal, dung cake, and kerosene consumption by 58%, 36%, 71%, and 74%, respectively. It also reduced the use of chemical fertilizer by 94% and the combined use of chemical fertilizer and manure by 91%. Adoption turned the majority of households (65.4%) to use combination of bio-slurry and chemical fertilizer. It helped the majority (89.95%) of adopters to construct and connect toilets to biogas operational system. In doing so, adoption reduced defecation in the eld and improved environmental sanitation and human health. It further enabled saving of about 38% of adopters’ time, which otherwise would be expended for rewood and dung collection. It similarly enhanced adopters’ income through decreasing expenses for chemical fertilizer, kerosene, and other fuel sources. Conclusions: of replacing traditional sources for domestic and of reducing the consumption of and chemical as well as of increasing income and decreasing time for collection.


Background
Biogas is combustible mixture of gas. It consists mainly of methane and carbon dioxide and is made from decomposition of organic compounds by anaerobic bacteria. It is a methane rich fuel gas produced by anaerobic digestion of organic materials with the help of methanogenic bacteria. Biogas technology offers a very attractive route to utilize certain categories of biomass for meeting partial energy needs (Molina et al., 2007). It provides an alternative energy source to the use of traditional fuel sources, which is dominantly used in most developing countries. Biogas technology serves two major purposes, biogas and bio-slurry. Biogas energy could replace the use of rewood, charcoal and kerosene for cooking, heating and lighting while bio-slurry could replace the use of chemical fertilizer for agricultural production (Sime et al., 2020).
Ethiopia is one of the developing countries that extremely relies on biomass for cooking and lighting (Lakew, 2010. The predominant cooking biomass energy source is rewood (77%), followed by cow dung cake (13%), crop residues (9%), and charcoal (1%). Kerosene (56%) is the central energy source for lighting, followed by a rechargeable electric battery (14%) in rural Ethiopia. Over 92% of the domestic energy demands are meeting from biomass-based fuels. Unsustainable cutting down of trees for rewood has directly caused signi cant deforestation, land degradation and soil erosion. The use of crop residues and dung cakes as substitute of rewood has further intensi ed problems related to land degradation and agricultural underproduction (Sime et al., 2020).
In the study area, scarcity of rewood has led to increased utilization of dung and agricultural residues for cooking, which otherwise would have been used to enhance forest cover, soil fertility and agricultural productivity. The undergoing biogas domestication activity in Ethiopia and the utilization of the potential of biogas technology has been low. The technical potential of biogas technology in replacing biomass . None of these studies have offered detailed attention to the evaluation of the technical potential of biogas technology in replacing rewood, charcoal, kerosene and chemical fertilizer. Thus, the objective of this study was to answer the technical potential of biogas technology in replacing rewood, charcoal, kerosene and chemical fertilizer in Southern Ethiopia.

Materials And Methods
Description of the study area Location Misrak and Mirab Estie Districts are located in South Gondar zone, Amhara Regional State, Northern Ethiopia ( Fig. 1). Misrak Esite District is located at 7˚40' N latitude and 36˚50'E longitude and at 96 kilometer from Bahir Dar, the capital city of Amhara Regional State and at 46 kilometer from Debre Tabor, the capital city of South Gondar zone. The District has 43 Kebele (5 urban and 38 rural villages), and is bordered by Abay River in the South, by Dera district in the West, by Farta in the North and by Simada in the East. Mirab Estie lies within 11 0 10' to 11 0 30' North latitude and 37 0 45' to 38 0 to 00'E longitudes. It is located at 148 kilometers from Bahir Dar, the capital city of Amhara Regional State and at 91 kilometers from Debre Tabor, the capital city of South Gondar zone. This District has 24 Kebele (2 urban and 22 rural villages), and is bordered by Misrak Estie in Northeast and by Abay River in the South and by Dera in the West.

The topography
The topography of Misrak and Mirab Estie Districts comprises 41% plain, 47% plateau and 12% deep gorge and other features according to District Agriculture O ce. It has wide variation in altitude, ranging from less than 1500 to more than 2300 meter above sea level.

Agro-climatic conditions
The Districts have three agro-ecological zones. They include Dega with an altitude of more than 2300 meter above sea level, Woina-dega with an altitude of 1500-2300 meter above sea level and Kolla with an altitude of less than 1500 meters above sea levels. Dega, Woina-dega and Kolla cover about 3%, 91% and 6%, respectively. The maximum and minimum annual temperature is 25 0 C and 8.3 0 C, respectively.  Note: the number of installed biogas plants is the same as the number of biogas user households Primary data were collected using questionnaires, semi-structure interview, focus group discussion and eld observation. The 74 household heads were interviewed through administering questionnaire. In addition, a total of seven key informants ( ve biogas users and two-biogas coordinators) were purposefully selected. Then, the key informants were interviewed upon their consent using interview checklists. Key informants are individuals who are knowledgeable, open-minded, articulate, and cooperative for research interview purpose (Neergaard and Ulhøi, 2007). Focus group discussion was also held with group of biogas users belonging to different age and sex categories. Three focus group discussion per sample District were held. Each group has six members. The optimum size for a focus group discussion ranges from six to eight members (Bloor, 2001, Ritchie et al., 2013). Responses from both the interviews and discussion were recorded with a tape recorder. User voices were also recorded in videos upon their consent.
The eld observations were conducted along with other data collection activities. Biogas plant feeding materials, major fuel sources, market value of household fuel at local market (charcoal, rewood, and kerosene and dung cake) and the use of chemical fertilizer and bio-slurry were observed.

Data analysis
All the data collected were entered into Microsoft O ce and statistical analysis was done using SPSS-20 software. Descriptive statistics, chi-square, one sample t-test was used for analysis of data obtained from questionnaire at 95% con dence interval and p-value < 0.05.

Results And Discussion
Socio-economic characteristics of user households Cattle holding size About 55.4%, 32%, 5.4%, and 6.8% of the households had cattle holding size ranging from 1-3, 4-5, 6-7 and > 7, respectively. The average cattle holding size was three cattle per household, which is less than the minimum standard set by the National Biogas Program of 4 cows for installing biogas plants (Table 3). One sample T-test result showed that livestock size has a signi cant (p < 0.05) positive association with the adoption of biogas technology. Field observations of biogas plants also showed that the availability of su cient cattle dung, which is the primary feedstock for biogas plants, is the most important factor in daily biogas operation. Thus, the quantity of dung available per day is critical in realizing the bene t and viability of biogas technology. Eshete et al.

Quantity of rewood consumption
About 70.3% of households consumed 3-5 bundles of rewood, 23% consumed 6-7 bundles of rewood and 6.8% consumed 8-9 bundles of rewood per month. This is, on average, equivalent to the consumption of 4.8 bundles of rewood per household per month or 57.6 bundles of rewood per year before adoption. After adoption, 81.1% of the households used 1-2 bundles of rewood, 10.8% used 3-4 bundles of rewood and 8.1% used 5-6 bundles of rewood per household per month, with an average consumption of 2.0 bundles of rewood per household per month. This is a reduction of more than 50% of the bundles of rewood used per household per month or is a reduction of 33.6 bundles of rewood per year. Thus, biogas technology adoption enabled the saving of 33.6 bundles of rewood annually. This is equivalent to saving 3010.56 ETB annually at a local price rate of 89.6 ETB per bundle of rewood (Table 5). Amare (2015) reported that biogas technology adoption enabled a reduction of 70.47% of rewood per household per year. This is a reduction in annual rewood consumption, approximately of 79 bundles of rewood per household per year. In turn, this is equivalent saving 3833.22 ETB annually at local rate of 48.40 ETB per 32 kg per bundle. A reduction of 45% in rewood consumption was also reported because of partial replacement of traditional fuels with biogas energy (Abadi et al., 2017). Similarly, other previous studies also showed that biogas users tend to consume less rewood than nonusers do (Christiaensen and Heltberg, 2014).           (Table 10). The use of chemical fertilizer was reduced from 41.9-2.7%, which is equivalent to 94% reduction. Similarly, the combined use of chemical fertilizer and manure was reduced from 47.3 to 4.1%, which is again equivalent to 91% reduction. Furthermore, eld observations showed that the use of bioslurry has increased following adoption. The majority of adopter households, which is about 65.4%, also used combination of bio-slurry and chemical fertilizer together. Debebe and Itana (2016) reported that 15.4% biogas adopter households used chemical fertilizer only, 11.5% used cow dung, compost and chemical fertilizer, while the remaining 7.7% used bio-slurry, compost and chemical fertilizer. The difference in the amount of money saved might infer to soil fertility, type of crop grown, and tradition of using chemical fertilizer and bio-slurry.  were very poor (Table 13). Biogas technology adoption helped the majority of biogas users to construct toilets and reduce defecation in the eld, with massive potential of improving environmental sanitation and human health.

Conclusion And Recommendation
This study evaluated the technical potential of biogas technology to replace traditional fuel, kerosene and bio-slurry in northern Ethiopia. Biogas technology adoption soundly reduced households' rewood, charcoal, dung cake and kerosene consumption by 58%, 36%, 71%, and 74%, respectively. It similarly reduced the use of chemical fertilizer and combination of chemical fertilizer and manure by 94%, and 91%, respectively. The technology also enhanced adopters' annual income. Besides increasing the trend of constructing toilets, it reduced defecation in the eld that massively improved environmental sanitation and human health. In conclusion, biogas technology offers a massive potential of reducing the consumption of rewood, charcoal, dung cake and kerosene, with huge implication for forest resource management and improvement of agricultural productivity, and human and environmental health. Future research need to focus on rectifying other challenges in uencing the realization of the technical potential of biogas technology dissemination in Ethiopia.

Declarations
Authors' contributions Both authors designed the research and conducted primary data collection and analysis for the studies. In addition, both authors edited and approved the nal manuscript.

Funding
This study received funding support from Hawassa University, Ethiopia.
Availability of data and materials Not applicable.
Ethics approval and consent to participate Not applicable.

Consent for publication
Not applicable.

Competing interests
The authors declare that they have no competing interests.

Figure 1
Physical map of study area Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.