3.1. Search results
From the literature search, a total of 11,361 publications were obtained. 11,317 publications were peer-reviewed articles, while 44 were grey literature gotten from various search engines of the World Wide Web. After screening the publications in two stages, 64 publications were selected based on their focus on the small-scale biogas plants in SSA or developing countries and the availability of PESTLE information in them. Out of these 64 publications, 58 were peer reviewed and 6 were grey. The distribution of the publications studied is shown in Table 1.
Table 1
Summary of the articles collected from the literature search
Geographical zone/ Country
|
Reference (s)
|
Σ
|
Africa, SSA
|
So et al. (2020), Surroop et al. (2019), Griffith-Jones et al. (2012), Roopnarain & Adeleke (2017a), Mandelli et al. (2014), Bamikole Amigun et al. (2011), Verbist (2018), Mulinda et al. (2013), Roopnarain & Adeleke (2017b) Kinyua et al. (2016), Cheng et al. (2014), Surendra et al. (2014), Maes & Verbist (2012), Ruane et al. (2010), Pollmann et al. (2014), Rupf et al. (2016), Smith et al. (2015), Rupf et al. (2015), Mwirigi et al. (2014b), Mohammed et al., (2013), Parawira (2009), Gebreegziabher et al. (2014), Mwirigi et al. (2014), Nevzorova & Kutcherov (2019), Terrapon-Pfaff et al. (2018), Amigun & Blottnitz (2009)
|
26
|
East Africa
|
Walekhwa et al. (2009), Wassie & Adaramola (2019) Karanja & Gasparatos (2019), Mwirigi et al. (2009), Kamp & Forn (2016), Mengistu et al. (2015b), Kamp & Forn (2015), Sarakikya (2015), Mwakaje (2008), Omer (2005), Godfrey (2012), (Wilson, 2007)
|
12
|
Central Africa
|
Muh et al. (2018), Tangka et al. (2016), Kimengsi (2015), Balgah et al. (2018)
|
4
|
Southern Africa
|
Walwyn & Brent (2015), Boyd (2012), Msibi & Kornelius (2017), Rasimphi & Tinarwo (2020), Chirambo (2016), Aliyu et al. (2018), Shane et al. (2017), Shane et al. (2016), Jingura et al. (2013), Mokhtar, et al. (2013), Kemausuor et al. (2011), Painuly & Fenhann (2002)
|
12
|
West Africa
|
Aliyu et al. (2015), Ishola et al. (2013), Akinbami et al. (2001), Okello et al. (2013), Mas’ud et al. (2015), Ohimain (2013), Ituen et al. (2009), Adeoti et al. (2000), Osei-Marfo et al. (2018), Kemausuor et al. (2015).
|
10
|
Total
|
|
64
|
Countries of the region where national biogas programmes were implemented, produced documents containing useful information needed to understand changes in the small-scale biogas technology. Unfortunately, academic publications were not found for the following countries: Cape Verde, Mauritania, Togo, Central African Republic, Equatorial Guinea, Sao Tomé and Principe, Liberia, Gambia, Benin, Mali, Togo, Senegal. However, a variety of grey literature on these countries was found.
3.2. PESTLE constraints to the development of small-scale biogas technology in SSA
Despite the market penetration of renewables in SSA, small-scale biogas technology remains one of the least exploited regarding the available potential. Barriers to their enhanced development are at all levels - in practical policy attitudes, economic sphere, social, technology management, environment and legislation. The results of the PESTLE factors are presented below.
3.2.1. Political
Political constraints to the development of small-scale BGT are still evident. Small-scale biogas technology still has minor influence on national energy supplies in SSA. SSA is still faced with several bottlenecks regarding the considerations of small-scale BGT issues related to the planning and implementation of bioenergy interventions. Before the year 2000, no SSA country had a bioenergy policy. Despite the advances made by some countries in the development of renewable and/or bioenergy policies, political support concerning policy frameworks that strongly support small-scale BGT development is inadequate. Austin (2003) indicated that South Africa could learn lessons from the Indian, Chinese and Nepalese programmes, with offers already having been made of bilateral governmental assistance in setting up such a programme. In 2009, (Parawira, 2009) still identified that poorly informed and uninformed authorities and policymakers in SSA have led to gaps in the formulation of renewable energy policies. As part of the experimentation process, SNV, Heifer International and Hivos assisted national governments of the region to develop and implement biogas programmes. However, the harmonisation of the policies. The African bioenergy policy framework and guidelines exist since 2013 (AUC-ECA, 2013). However, countries are still in the process of preparing or are still to begin the preparation of this policy. The passivity of some governments still remains a threat to promote the new biogas technology (Pollmann et al., 2014). In 2017, bioenergy provided 176,000 jobs in the region. Biogas technology expansion opens employment opportunities for masons, plumbers, civil engineers, and agronomists (Mengistu et al., 2015). However, the number or percentage of these jobs created has not been realistically determined yet. There is increasing priority to biogas technology in 2020 compared to the year 2000. Bottom-up approaches are required for the significant inclusion of small-scale technology in the national renewable energy policies. Most development policy frameworks in the region have no direct strategy for the development of small-scale biogas technology. The stability of political framework and transparency is therefore required for the development of small-scale biogas technology. Socio-political instability in some SSA countries has led to the low adoption rate and dissemination of small-scale biogas plants. For example, Burundi was affected by the war between 1993 and 2000 (SE4All, 2013). Since then, they are still reconstructing the country and pending significant interest in developing small-scale biogas plants. Under a stable socio-political situation, the biogas potential is an asset.
3.2.2. Economic
The primary economic constraint to the development of the small-scale BGT is the inadequate investment cost. The average cost of small-scale biogas plants in some SSA countries is shown in Table 2. However, the cost of the technology is mainly dependent of the plant’s geographical location (Amigun & Von Blottnitz, 2010). Boyd (2012) reported in South Africa inadequate access to finance. Generally, there is still a inadequate reliable information on the benefits of the technology by financial institutions (Parawira, 2009) in the region and a lack of financing structures for small projects. The revenue from the digested slurry, otherwise referred to as organic fertiliser, is largely not yet estimated for most SSA countries. There is also an information deficit on the economic viability of available biomass and waste resources (So et al., 2020). Due to clustering of poor or average homes in some countries, construction space is seen as a constraint to the adoption of the small-scale BGPs. This was identified in the case of Nigeria by Akinbami et al. (2001). Mwirigi et al. (2014), in a study in Uganda, stated that other factors affecting the adoption of small-scale biogas technology include low levels of awareness of the potential uses of biogas and the small size of landholdings, which limits the number of different types of land use unless the uses are complementary. However, by 2017, Kenya had made the most progress toward establishing viable biogas plant markets, including hosting companies with prefabricated digesters and establishing 22 marketing hubs, linking rural institutions to local enterprises and finance (Clemens et al., 2018). Makai & Molinas (2013) revealed that the payback period of small-scale BGPs in Zambia is 3.25 to 3.75 years. According to Kabyanga et al. (2018), many of the biogas designs promoted in Uganda have proved to be too expensive for the average Ugandan to afford. They added that a cheaper flexible balloon digester is being proposed, but there has been no evidence on this design’s economic viability. Generally, small-scale biogas users still find it challenging to afford the complete installation of the small-scale BGPs. Parawira (2009) recommended the need to provide loans and subsidies to encourage and promote biogas technology. Market incentives for biogas technology take the form of ‘soft’ loans, direct and indirect subsidies and international funding schemes through the Clean Development Mechanism fund and Joint Implementation Programme’ (Surroop et al., 2019). In several OECD (Organization for Economic Cooperation and Development) countries, firms and individual households can collect government subsidies if they adopted technologies that have socially desirable characteristics (Mengistu et al., 2015b).
Table 2
Average costs of small-scale biogas plants in some SSA countries
Location
|
Capacity (m3)
|
Year constructed
|
Cost (US$)
|
Source
|
Burkina Faso
|
6
|
2004
|
1,209.00
|
Osei-Marfo et al. (2018)
|
Ghana
|
6
|
2004
|
1,358.00
|
Osei-Marfo et al. (2018)
|
Ghana
|
6
|
2011
|
2,189.00
|
Osei-Marfo et al. (2018)
|
Ghana
|
6
|
2015
|
851.00
|
Osei-Marfo et al. (2018)
|
Ghana
|
10
|
2011
|
3,169.00
|
Osei-Marfo et al. (2018)
|
Kenya
|
8
|
2004
|
2,973.00
|
Osei-Marfo et al. (2018)
|
Uganda
|
6
|
2004
|
1,005.00
|
Osei-Marfo et al. (2018)
|
Rwanda
|
6
|
2007
|
859.00
|
Amigun & Blottnitz (2010)
|
South Africa
|
6
|
2007
|
1149.86
|
Amigun & Blottnitz (2010)
|
Akinbami et al. (2001) recommended that using local materials reduce construction costs, which constituted up to 65% of the total costs. Labour and other costs amounted to an additional 35% of the cost (Akinbami et al., 2001). In some cases, household labour was used to reduce costs (Osei-Marfo et al., 2018).
Biogas technology has been scaled up in SSA during the last two decades with programme funds mainly from SNV, Hivos and Heifer International. However, the sustainability of the adoptions is not ensured because of the various constraints after the programmes. One possible, despite the controversial approach to increasing the adoption of small-scale biogas technology out of the programme funds is to utilise the available funds that a household possesses, rather than targeting the very poor households (Smith et al., 2011). Information dissemination on the successful implementation of the technology by farmers to their counterparts proves to be the best tool to promote biogas use (Berhe et al., 2017). Biogas produced with small-scale digesters is used in different appliances including biogas stoves (one and two burners), water heater (Mwirigi et al. (2014a), biogas lamp (Khandelwal, 2009; Mwirigi et al., 2014a) and biogas electricity generator (Tangka et al., 2016; Mwirigi et al., 2014a).
3.2.3. Social
In the beginning of the year 2000, socio-cultural constraints still impacted the uptake and dissemination of the small-scale BGPs. In Nigeria, Akinbami et al, (2001) reported that the inertia toward changes, especially when it involves an unfamiliar (even though simple) technology, are potential barriers to adopting and disseminating biogas technology. Walekhwa et al. (2009) later in Uganda assessed Uganda’s acceptance of small-scale BGT and discovered that the development and acceptance of biogas technology largely depended on exploiting its technological opportunities over the existing technologies. This was exacerbated by the poor ownership responsibility of the users (Parawira, 2009). In Rwanda, Tanzania and Malawi, (Barry et al., 2011) identified that training and skills development of communities would alleviate the lack of user acceptance. There was the need to improve the skills base of the community to help maintain the technology. The dissemination needs to be done through capacity building, governance and integrated development (Ghimire, 2013a). In 2014, low levels of awareness of the potential uses of biogas and the small size of landholdings, limiting the number of different types of land use unless the uses are complimentary (Mwirigi et al., 2014). In Uganda, an increase in age and level of education were inversely related to adoption. In contrast, the availability of traditional fuels and the increase in household size positively impacted the acceptance of the technology (Mwirigi et al., 2014). The low levels of education and income of women were the leading causes of limited, little or no involvement of in the decision for procurement of the BGPs. The decision to install the BGPs was mainly made by the male heads of households who control resources and their allocation (Mwirigi et al., 2014). Over the past two decades, biogas stakeholders have made significant efforts to create awareness on the role of small-scale BGT. In the region, the technology is generally accepted by people of different socio-cultural and religious backgrounds. But affordability and gender constraints still need to be addressed for wider adoption of the technology. Notwithstanding, Nevzorova & Kutcherov (2019) still identified a lack of acceptance as one of the constraints to the development of small-scale BGT in SSA. A study by (Lemma et al., 2020) in southern Ethiopia also showed that in households, 92.5% of biogas users and 77.5% of non-users tend to have a positive attitude towards biogas technology. However, 52.5% of the non-users did not have adequate information, while the installation costs deterred 25% of the non-users.
3.2.4. Technological
Technical potential of small-scale BGPs in SSA
The technical potential is defined as the number of households that can meet the two basic requirements – sufficient availability of both dung and water – to operate a biogas plant (SNV, 2018). The first estimation of the technical potential of domestic or household biogas in Africa was done in 2007 by Heegde & Sonder (2007). Two leading indicators were used included the number of households with access to water and the number of domestic cattle per household (ibid). The small-scale biogas potential of SSA is continuously being assessed. A study by SNV (2018) showed that the present technical potential for household biogas plants in Africa arrives at 32.9 million installations. By 2012, the total number of BGPs had risen to nearly 23,000, by December 2018, to 75,561 with the involvement of other agencies under the umbrella of the Africa Biogas Partnership Programme (ABPP) (Freeman et al., 2019). This shows that SSA has exploited less than 1 per cent of its technical biogas potential. Figure 3 shows the quintile distribution of the technical potential of HH biogas plants in SSA.
Source: Data from SNV (2018).
Choice of digester design
There exist three main philosophies commonly applied in the design of household or small-scale BGPs, namely the floating drum, the fixed dome, and the flexible balloon digester (Jansen & Rutz, 2012). Prefabricated biogas digesters following the above philosophies are also present in the region (Cheng et al., 2014). Biogas plants’ size is be based upon: (i) the (daily) amount of available feeding material; and (ii) the biogas requirement of the family (Freeman et al., 2019). Some of the major constraints identified include the wrong selection of the design and size of the digester. This contributes to the operation failure in some cases. Construction of the digesters with low quality materials has resulted in short life, low efficiency biogas plants.
Table 3
Type of digester
|
Advantages
|
Disadvantages
|
Source
|
Fixed dome digester
|
• eliminates the use of costly mild steel gasholder,
• relatively low installation cost (about two-thirds of the cost of the floating drum digester),
• does not have moving parts,
• does not have rusting steel parts,
• long lifespan (20 years or more),
• possible underground construction,
• saves space,
• creates local employment during construction,
|
• digesters are usually not gastight (porosity and cracks). The gas tightness is a problem that pertains only to the constructed systems and not prefabricated systems,
• gas pressure fluctuates substantially.
|
(Mulinda et al., 2013). (Jansen & Rutz, 2012).
|
Floating drum
|
• has a simple operation design,
• operates at constant gas pressure, and the volume of stored gas is visible directly on the
|
• high installation cost (up to 50% greater than that of a fixed dome digester),
• uses many steel parts that can easily corrode, leading to short lifespan (up to 15 years; in tropical regions and about 5 years for the drum),
• requires regular maintenance costs due to painting.
|
(Mulinda et al., 2013), (Jansen & Rutz, 2012).
|
Flexible balloon biogas digester
|
• technically cheapest and simple design to install
• easy transportation,
• shallow construction
• high digester temperatures,
• easy cleaning, emptying, and maintenance.
|
• short lifespan (about 5 years),
• High risk of damage,
• no real local employment creation, little scope for self-help
• low gas storage is a limitation
|
(Kabyanga et al., 2018), (Jansen & Rutz, 2012)
|
Since the first introduction of the small-scale technology in SSA, the conventional fixed dome and floating biogas digester were promoted. The fixed-dome design is accepted by most users as the most viable design that is affordable and reliable for the domestic market. In SSA like other parts of the world like India, the switch from the floating drum design to the fixed dome design is increasing (Jansen & Rutz, 2012). However, due to inadequate finance to purchase these plants, the private sector has developed low-cost biogas plants, including the Flexi-biogas in Kenya, while others have recycled plastic containers into biogas digesters. From 2011 to 2014, IFAD and Biogas International distributed 500 Flexi-Biogas System (FBS) units to rural Kenyan households (Sovacool et al., 2015). However, the flexible balloon biogas digester design is not suitable for a programme-based approach to digester installations where a predefined financing scheme (including subsidies linked to quality assurance measures and long-term production of voluntary or certified emissions reductions). Therefore, long-term functionality, is needed. Balloon BGPs are preferable wherever the balloon surface is not exposed or has the likely risk of damage especially in areas where the temperature is constant high (Jansen & Rutz, 2012).
Anaerobic digestion efficiency
Biogas production through anaerobic digestion of organic waste using small-scale BGPs is a continuous learning process in the regions. Parawira (2009) in Uganda identified that household biogas digesters in SSA, usually lack facilities to remove sand, stones and other non-digestible materials, which accumulate over years of use, thereby decreasing the volume of the digesters and hence reduce efficiency. SSA has favourable conditions for biogas technology, namely a suitable tropical climate in most parts of the region (Rupf et al., 2015). From the poor designs to poor operation and maintenance, followed by the lack of inadequate monitoring devices, most of the small-scale BGPs rely on the local climatic conditions. To realise the full potential of biogas, the efficiency of end-use appliances must also be improved and adapted to local cooking conditions, as has been done with other cooking technologies (Freeman et al., 2019). Co-digestion has also proven to ease or improve biogas, e.g. the case of a mixture of poultry/cow dung/water hyacinth at the Songhai Farm in Burkina Faso.
Waste availability
In SSA, the feedstock for biogas production is mainly excreta from livestock, e.g. cattle, sheep, goats, horses, donkeys, rabbits and chickens, but also from humans if culturally acceptable (Orskov et al., 2014). The biogas potentials of the available animal and agricultural feedstocks have not been thoroughly researched. Karekezi et al. (2003) stated that despite the proof of the viability of small-scale biogas plants, dung collection proved more problematic than anticipated, particularly for farmers who did not keep their livestock penned in one location. More R&D is also needed to explore better substrates to boost the efficiency and performance of the biogas plants. Land management and the method of rearing is also affecting the availability of feedstocks. For example, the results of the nationally representative household surveys in Ethiopia, Kenya, Rwanda, Mozambique and Zambia, concluded that farm sizes in Africa are declining over time, with approximately 25% of agricultural households being virtually landless, controlling less than 0.1 ha caput− 1, the largest part of the variation in farm sizes occurring within, rather than between villages. Households controlling such a low area of land may be limited in the livestock they can manage, which may, in turn, limit their potential to run a biogas digester (Orskov et al., 2014).
Water availability for anaerobic digestion across the region
Mwirigi et al. (2014) identified hurdles to the wider adoption of small-scale BGT in SSA, including limited access to water. In South Africa, Calendar et al. (2007) revealed a common misperception that access to water is a constraint on the use of BGT at the household level. Since each family uses water every day, this same water can easily be directed to the biogas digester. According to Griffith-Jones et al. (2012), households in SSA were 28.2% and 125.2% more likely to have access to improved water sources in 2000–2005 and 2010–2015, respectively, than in 1990–1995. The World Bank (2020) reports that 27% of the population of SSA have access to safely managed drinking water.
Design, construction and maintenance
In SSA, inexperienced technicians and consultants have resulted in poor quality BGPs. This is a result of poor selection of construction materials (Parawira, 2009). This is also due to inadequate technical know-how in the design and construction of small-scale biogas plants (So et al., 2020) and flawed or wrong operation and maintenance culture (So et al., 2020). The optimisation of the BGP design process has been constrained by inadequate knowledge, even at the level of research institutes and universities (Parawira, 2009). A study by Berhe et al. (2017) in Ethiopia’s Tigray region showed that 58.1% (of a total of 3600 BGPs) of the installed BGPs were non-operational due to incomplete installation, other technical problems, and limited supervision. Waste collection reliability is still not measured. However, the small-scale biogas plants have contributed to reducing the time to collect fuelwood by women and children in the region.
3.2.5. Legal
Several disputes persist in Sub-Saharan Africa regarding the sustainable management of local water, land and agricultural wastes for small-scale biogas production. In South Africa, Du Plessis (2003) identified that no legal measures were dealing with the collection of dung, except in the case of the Gas Act of 2002 that excludes small biogas projects in rural communities from the Act. Some countries in sub-Saharan Africa have relatively successfully scaled up renewable energy through changing energy market structures and introduced incentives (Griffith-Jones et al., 2012). South Africa and Uganda are some of the identified SSA countries that have instituted Renewable Feed-in Tariffs (REFIT) on renewable energy, including biogas technology. According to private finance practitioners, Griffith-Jones et al. (2012) added that a FIT of 50% is a powerful incentive mechanism for renewable energy deployment in developing countries. In Kenya, biogas equipment such as stoves, other appliances, and prefabricated digesters may be exempted from import tax. Notwithstanding, interviews with biogas stakeholders (mainly entrepreneurs) indicate that the exemption can only apply to the entire shipping containers of appliances and therefore, do not benefit small enterprises. Moreover, the process to obtain duty-free status is unclear to local entrepreneurs in the region. No tax exemptions exists in Tanzania and Uganda (Clemens et al., 2018), as well as on most other countries of the region. According to IRENA (2018), renewable energy auctions can be successfully implemented in South Africa, Uganda and Zambia. However, only large-scale biogas technology producing marketable electricity can benefit from these auctions. However, small-scale biogas technology still lacks cost legal frameworks for development incentives in the region.
3.2.6. Environmental
The BGPs in SSA are multi-functional depending on the reason for construction such as sanitation, energy recovery, management of waste and environmental protection (Mulinda et al., 2013). The unsustainable use of fuelwood biomass can accelerate deforestation and lead to soil erosion, desertification and an increased risk of flooding and biodiversity loss (Parawira, 2009). The Clean Development Mechanism (CDM) can promote renewables projects in developing countries to offset emission reduction commitments under the Kyoto protocol in developed countries, which by investing in developing countries can earn credits (WEC, 2004). Venkata et al. (2015), per 2010 data, indicated that household air pollution mortality and morbidity led to 14% of the deaths in SSA in an affected population of 3.5 million. This also led to 24% Disability-Adjusted Life Year (DALY). In Ethiopia, each household BGP has the potential to reduce about 6024 kg CO2e per year of GHG emissions (Lemma et al., 2020). Under the Paris Agreement on Climate Change, all SSA countries have included renewable energy actions (covering all technologies and end-use applications) as commitments to tackle climate change as well as spur economic growth (UNECA, 2018). Despite the ratification agreement by all SSA countries, there is an inadequate effort being made by governments to develop small-scale biogas plants as part of the national environmental strategies.