Rwanda peat deposits: An alternative to energy sources

Mugerwa, Theophile; Rwabuhungu, Digne Edmond; Ehinola, Olugbenga A.; Uwanyirigira, Janviere; Muyizere, Darius Article Rwanda peat deposits: An alternative to energy sources Energy Reports Provided in Cooperation with: Elsevier Suggested Citation: Mugerwa, Theophile; Rwabuhungu, Digne Edmond; Ehinola, Olugbenga A.; Uwanyirigira, Janviere; Muyizere, Darius (2019) : Rwanda peat deposits: An alternative to energy sources, Energy Reports, ISSN 2352-4847, Elsevier, Amsterdam, Vol. 5, pp. 1151-1155, https://doi.org/10.1016/j.egyr.2019.08.008 This Version is available at: https://hdl.handle.net/10419/243658 Standard-Nutzungsbedingungen: Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden. Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen. 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If the documents have been made available under an Open Content Licence (especially Creative Commons Licences), you may exercise further usage rights as specified in the indicated licence. https://creativecommons.org/licenses/by/4.0/ Energy Reports 5 (2019) 1151–1155 Contents lists available at ScienceDirect Energy Reports journal homepage: www.elsevier.com/locate/egyr Research Paper Rwanda peat deposits: An alternative to energy sources Theophile Mugerwa a,b,∗, Digne Edmond Rwabuhungu b, Olugbenga A. Ehinola a, Janviere Uwanyirigira b, Darius Muyizere c aInstitute of Life and Earth Sciences (Including Health & Agriculture), Pan African UniversityUniversity of Ibadan, Ibadan, Nigeria bSchool of Mining and Geology, University of Rwanda, Kigali, Rwanda cAfrican Centre of Excellence in Energy for Sustainable Development, University of Rwanda, Rwanda article info Article history: Received 18 January 2019 Received in revised form 8 July 2019 Accepted 10 August 2019 Available online xxxx Keywords: Peat Proximate analysis Electrical power Energy Rwanda abstract In this era, energy and environmental sustainability is a priority in most African countries developmental agenda. The need for energy equity and security in Rwanda is a priority and thus this paper illustrate the current peat resources and their energy potential which can be mined to meet country vast energy requirements. Six hundred (600) peat samples were collected from eighteen peat bogs and all samples were subjected to proximate analyses respecting the procedures outlined by the Bureau of Indian Standard and American Society for Testing and Materials. The high moisture content (average 70.88%) is typical of peats (70%–90%). The total sulfur percentage values (average 0.49%) are generally medium for all samples. The gross calorific values of peat samples ranged from 2560 to 5350 Kcal/kg, with an average value of 3976 Kcal/kg. These values are moderately very high because typical dry peat has calorific values of 2000 Kcal/kg. Mashya displays the lowest value (19%) while the highest ash content (80%) is found in Kageyo. The average ash content in all studied location is 38%. The moisture content in all locations is slightly high ranging from 53% to 85%. Most of the peat deposits in Rwanda may be converted into energy based on the calorific value of all samples. Akanyaru, Mukindo, Gishoma, Mashya, Kaguhu, Mukindo and Nyirabirande are the most promising sites for peat mining. ©2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). 1. Introduction Peat is low rank coal, which is made of plant remains as evidenced by the presence of biomarkers detected through chemical, geological, and petrographic studies (Del Rio et al.,1992). It is sedimentary deposit formed principally from plants and rarely from inorganic substances. It is, thus, an aggregate of macerals or premacerals and minerals that when subjected to certain processes, can be converted to coal. According to Cohen et al. (1987) it is difficult to place a precise boundary between what might be a precursor of carbonaceous shale and what might be a precursor of a coal. However, it is agreed that the precursor of a good coal should consist of at least 70% dry weight of organic material (Del Rio et al.,1992). The peat has attracted coal geologists due to their distribution, low ash content, low sulfur content and significant thickness (Staub et al.,1991;Dehmer,1992). It is used as source of energy mostly in Europe (e.g., Finland, Sweden, etc.,) and Russia (Schora and Punwani,1980). The use of gas and oil during 20th has shadowed the use of peat (Andriesse,1988) but the high demand for electricity ∗Corresponding author at: Institute of Life and Earth Sciences (Including Health & Agriculture), Pan African UniversityUniversity of Ibadan, Ibadan, Nigeria. E-mail address: [email protected] (T. Mugerwa). has stimulated the construction of peat-fired power plant. In developing worlds where energy is scarce, they scale it up to meet their objectives to achieve the development. In Sub-Saharan Africa, energy accessibility and affordability (Equity) is a priority in their agenda while European countries need energy security (IEA,2014;Ituze et al.,2017). Rwanda is most densely populated in Africa with about 10.5 million inhabitants and it is projected that in 2032, the Rwandan population will be 15.4 million (MINECOFIN,2014). Inefficient and expensive electrical energy supply hinders the development of the country and therefore the government has a target to decrease wood’s consumption from 86.3% to 50% of national energy consumption in 2020 (Rwanda, 2012). As the demand for energy is growing, the researchers attempted to evaluate the contribution of peat deposits for energy production to meet country vast energy requirements. 2. Peat reserves in Rwanda The quantitative assessment of peat deposits in Rwanda is approximately 155 million tons of peat on dry basis across the country (Vitikka and Lahtinen,2013;Ekono,1992) and these deposits could be converted into energy (Hakizimana et al.,2016). The major peat deposits are presented on Table 1. https://doi.org/10.1016/j.egyr.2019.08.008 2352-4847/©2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). 1152 T. Mugerwa, D.E. Rwabuhungu, O.A. Ehinola et al. / Energy Reports 5 (2019) 1151–1155 Table 1 Peat reserves in Rwanda (EDCL,2014). Name of peat bog Area (ha) Quantity of exploitable peat reserves, dry basis (tonnes) Sod peat Milled peat Rucyahabi 925 813 973 687 998 Akanyaru North–North part 1321 501 291 68 753 Akanyaru North–Middle part 1994 3 572 375 2 026 147 Akanyaru North–South part 3208 15 740 346 11 517 536 Akanyaru South 2108 7 797 785 6 763 219 Mukindo 959 1 323 573 698 581 Kaguhu 195 69 712 64 942 Gishoma 423 171 880 88 305 Gihitasi 90 12 168 12 168 Mashya 36 89 821 78 191 Fig. 1. Main energy resources in Rwanda (RDB,2019). It is clear that the hydropower energy is the leading energy resources in Rwanda. 3. Energy scenario in Rwanda The main energy resources are Wood, Hydropower, Solar energy, Biogas, wind, biomass, Solar photovoltaic (PV), methane gas, peat, geothermal and petroleum products (Safari,2010;Ituze et al.,2017). According to RDB (2019) the main energy resources are hydropower; thermal, solar PV, and methane to power (Fig. 1). Rwanda energy sector improvement in the past few years is a result to economic reform, development and clear vision. Wood consumption has been the main source of energy to Rwandan households for the past decades. For example, wood provided 99% of energy in 2000 and 86.5% in 2010, (Rwanda, 2012). Nyamvuba and Gakuba (2014) indicate that supply and consumer needs analysis revealed that 85% of primary energy used in the country were coming from biomass, either in the form of wood directly used as fuel (57%) or charcoal (23%). Bimenyimana et al. (2018) states that, at present day, wood is still the main source of energy, mainly due to its low cost in comparison to other sources. Consequently, however, this large-scale wood consumption has been associated with deforestation, soil degradation (Rwanda,2012), and have been found to contribute to global warming. In addressing the issue associated with energy production, the Government of Rwanda, in its Vision 2020 policy, planned to have diversified energy resources, provided electricity to 75% of the population and wood consumption to have dropped at 50% of energy consumption, by the year 2020. At present day however, the Rwanda Energy Group (REG) re-drafted targets for electricity generation. REG new planning policy targets on generating 586 MW, from the current 220.9 MW, and providing a 100% electricity access to Rwandans, from the current 45.3%, by the year 2024, (REG,2019a). This include 52% on-grid and 48% off-grid connections, (USAID,2018). In addition to wood, Rwanda has various potential resources of energy including biogas, hydro, solar, petroleum, methane gas, wind and geothermal, (Nyamvuba and Gakuba,2014). Table 2 The Von post classification system and Von post degree of humification (H1 to H10) for peat. Source: Adapted from Andriesse (1988). Symbol Description H1 Completely undecomposed peat which, when squeezed, releases almost clear water. Plant remains easily identifiable. No amorphous material observed present H2 Almost entirely undecomposed peat which, when squeezed, releases clear or yellowish water. Plant remains still easily identifiable. No amorphous material present H3 Very slightly decomposed peat which, when squeezed, releases muddy brown water, but from which no peat passes between the fingers. Plant remains still identifiable, and no amorphous material present H4 Slightly decomposed peat which, when squeezed, releases very muddy dark water. No peat is passed between the fingers but the plant remains are slightly pasty and have lost some of their identifiable features H5 Moderately decomposed peat which, when squeezed, releases very ‘‘muddy’’ water with a very small amount of amorphous granular peat escaping between the fingers. The structure of the plant remains is quite indistinct although it is still possible to recognize certain features. The residue is very pasty H6 Moderately highly decomposed peat with a very indistinct plant structure. When squeezed, about one-third of the peat escapes between the fingers. The residue is very pasty but shows the plant structure more distinctly than before squeezing H7 Highly decomposed peat. Contains a lot of amorphous material with very faintly recognizable plant structure. When squeezed, about one-half of the peat escapes between the fingers. The water, if any is released, is very dark and almost pasty H8 Very highly decomposed peat with a large quantity of amorphous material and very indistinct plant structure. When squeezed, about two-thirds of the peat escapes between the fingers. A small quantity of pasty water may be released. The plant material remaining in the hand consists of residues such as roots and fibers that resist decomposition H9 Practically fully decomposed peat in which there is hardly any recognizable plant structure. When squeezed it is a fairly uniform paste H10 Completely decomposed peat with no discernible plant structure. When squeezed, all the wet peat escapes between the fingers Hydropower, solar, and methane gas constitutes the main natural resources of energy in Rwanda (USAID,2018) (Fig. 1). According to Bimenyimana et al. (2018), hydropower and solar resources are the main renewable energy resources, with the largest power proportion originating from hydropower projects across numerous rivers and water falls across the country. Lake Kivu methane gas production currently contributes ∼14.3% of energy (Fig. 1), and at full completion, the Kivu Watt project aims to produce over 100 MW of electricity (Contour global,2019). Since 2007, the government of Rwanda has put tremendous efforts in Biogas technology to cut down wood consumption, (Landi et al.,2013). Biogas is mainly used in schools, prisons and some rural households, (Sinaruguliye and Hategekimana,2013). Currently, Rwanda has not yet discovered any petroleum resources in line with the East African Rift Valley petroleum system. As of 2016, the daily consumption of petroleum products in Rwanda accounted at ∼6000 bbl (US liquid barrel) (Munyaneza et al.,2016). Most of the petroleum products in Rwanda are imported from neighboring countries such as Kenya and Tanzania, (Munyaneza et al.,2016). In addition to the above resources, peat resources are becoming significant contributors to the energy production sector in Rwanda. It accounts for ∼155 million tonnes of dry peat, which can be used for electricity generation (Bimenyimana et al.,2018; REG,2019b). Seventy seven percent (77%) of such deposits occur T. Mugerwa, D.E. Rwabuhungu, O.A. Ehinola et al. / Energy Reports 5 (2019) 1151–1155 1153 Fig. 2. Rwanda peat deposits distribution map. proximally near Akanyaru and Nyabarongo rivers and Rwabusoro plains (MININFRA,2015;REG,2019b). However, despite the large peat deposit accounted in Rwanda, only two peat to power projects are currently under development. Gishoma 15 MW peat to power project was completed in 2017 and 80 MW Hakan project is under construction since February 2017 (REG,2019b). 4. Materials and methods 4.1. Sampling procedures The systematic grid sampling was used in this study. The sampling process was commenced with determination of the coordinates of all sampling locations and core samples were collected from each drill hole in different locations for each 50 cm interval down to the depth where there is no peat. At each location, the corer was pressed into layers by hand. The six hundred samples collected were placed in tightly closed plastic buckets and labeled prior to being sent to the laboratory for testing. The samples were collected in various peat bogs (Fig. 2). The samples were described on field and classified based on Von Post classification (Table 2). 4.2. Methods The proximate analysis of peat includes the determination of moisture, volatile matter, ash, fixed carbon and calorific value. The first three parameters were determined in laboratory and the fixed carbon was calculated. The samples were crushed to <72-mesh size for chemical analysis. The proximate and sulfur analyses were done following the Bureau of Indian Standard IS:135 (BIS,2003) and American Society for Testing and Materials (ASTM,1989) respectively. 5. Proximate analysis results and discussion The average ash content of samples taken from different location are displayed in Table 3 where Mashya display the lowest value (19%) while the highest ash content (80% ) is found in Kageyo (Fig. 3). The average ash content in all studied location is 38%. The moisture content in all locations is slightly high ranging from 53% to 85%. Kaguhu and Kageyo display the lowest moisture content (53%) while Akanyaru North is featured with highest value (85%). The ash content of less than 40% in soda peat dried up to 30% moisture content and less than 30% in milled peat dried to 1154 T. Mugerwa, D.E. Rwabuhungu, O.A. Ehinola et al. / Energy Reports 5 (2019) 1151–1155 Fig. 3. Average ash content in all sampling locations. Table 3 Proximate analysis results of peat samples. Name of peat In-situ moisture Average ash Average volatile Average fixed Average sulfur Average calorific bog content(% wt) content in dry matter content content carbon value basis Cyato 64 33 10.70 19.21 0.45 2981 Murago 83 31 46.70 20.81 0.12 2560 Rucyahabi 80 29 55.00 26.40 0.23 3218 Akanyaru 68 46 48.13 29.30 0.35 5000.9 North(other), North Akanyaru 78 42 40.83 26.00 0.21 5112 North(other), Middle Akanyaru 85 28 41 28.10 0.25 4813 North(other, South) Bishya 70 39 68.00 25.70 0.80 3654 Akanyaru 83 20 60.22 22.62 0.41 3782 South (other) Mukindo 65 43 60.00 19.98 1.0 4002 Gishoma 73 31 61.36 22.45 0.25 4756 Gihitasi 73 74 18.50 31.3 0.53 2845 Mashya 86 19 50.10 28.88 0.39 4850 Kaguhu 53 28 21.90 0.65 5350 Bahimba 55 42 40.70 19.21 1.1 3973 Bisika 54 73 63.90 21.00 0.76 3751 Kageyo 53 80 68.20 26.48 0.49 2987 Ndongozi 76 33 72.01 25.28 0.64 3622 Nyirabirande 67 20 68.21 18.22 0.33 4318 40% is suitable for electrical power generation (EDCL,2014). The volatile matter of peat falls between 60%–70% (Lindström,1980) while that of Rwanda is ranging from 10%–72%. The quality of peats for fuel production is influenced by humification grade and thus all samples with ash content less than 40% are in humification grade 4 (H4) to H10. As demonstrated by Lasse (2007) the increase in humification grade, positively influence the calorific value of peats. The high moisture content (average 70.88%) is typical of peats (70%–90%). The total sulfur percentage values (average 0.49%) are generally medium for all samples. The gross calorific values of peat samples ranged from 2560 to 5350 Kcal/kg, with an average value of 3976 Kcal/kg. These values are moderately very high because typical dry peat has calorific values of 2000 Kcal/kg (Fatma and Sadettin,2015). The peats with calorific value less than 4562 Kcal/Kg are not suitable energy production (Lasse, 2007). Akanyaru peat bogs have the calorific value above 5000 Kcal/Kg and are considered the overall bogs for energy production. The high ash content of Gihitasi; Bisika and Kageyo make them unsuitable for energy production because the ash content in dry basis above 40% affects negatively the calorific value of peats (EDCL,2014). According to Ituze et al. (2017), the available peat deposits in Rwanda will contribute 20.6% to the energy growth by 2025 (Table 4). 6. Conclusion The peat to power in Rwanda is a matter of urgency to achieve the developmental target and to ensure that all population will have access to the electricity by 2025. Most of the peat deposits in Rwanda can be converted into energy based the calorific value of all samples. Akanyaru, Mukindo, Gishoma, Mashya, Kaguhu, T. Mugerwa, D.E. Rwabuhungu, O.A. Ehinola et al. / Energy Reports 5 (2019) 1151–1155 1155 Table 4 Rwanda energy mix road map projects (Modified after Ituze et al.,2017). Energy resources Medium term Medium to long Unit (2012–2017) term target from 2018 to 2025 Generation 132–595 595–1450 MW Hydropower 200 310 MW Methane 100 350 MW Peat power 115 300 (20.6%) MW Geothermal 160 460 MW Heavy fossil oil 20 20 MW Total 595 1450 MW Average US Dollars (Million) 510 555 $ Mukindo and Nyirabirande are the promising bogs for peat mining for energy generation. In rural area, the wood is mostly used as sources of power and this has urged the Government of Rwanda and partners to start constructing peat to power plants where the peat are expected to generate 20.6% of all energy resources in Rwanda. This effort to use peat as source of power along with other project, they will promote the development of the Country. To use peat as source of power, it is advisable to develop suitable pollution control as the coal burning contribute to environmental pollution and climate change. 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