CC BY
29
УДК 621.39
G. M. BELLO, A. A. SHUPILOV, B. G. DANSHEKHU Г. М. БЕЛЛО, А.А. ШУПИЛОВ, Б. Г. ДАНЬШЕХУ
RENEWABLE ENERGY TECHNOLOGIES: AN ALTERNATIVE OPTION FOR AGRICULTURAL GREENHOUSE GASES (GHGs) REDUCTION FOR WEST AFRICAN SUB-SAHARAN COUNTRIES
ВОЗОБНОВЛЯЕМАЯ ЭНЕРГЕТИЧЕСКАЯ ТЕХНОЛОГИЯ - АЛЬТЕРНАТИВНЫЙ МЕТОД СНИЖЕНИЯ СЕЛЬСКОХОЗЯЙСТВЕННЫХ ПАРНИКОВЫХ ГАЗОВ (ПГ) В ЗАПАДНОАФРИКАНСКИХ СТРАНАХ
(Поступила в редакцию 15.01.2015)
This paper discusses the renewable energy technologies for В статье обсуждаются технологии возобновляемой
the reduction of greenhouse gases emissions that are produced by энергии для уменьшения эмиссии парниковых газов, произ-agriculture in the Sub-Sahara African countries. These quantities водимых сельским хозяйством в странах южнее Сахары. of agricultural residues, animal wastes appears to have potential Растительные остатки и отходы животноводства могут as an alternative renewable energy for many African countries if стать альтернативным источником возобновляемой энер-relevant and appropriate research is carried out to adopt the гии для многих африканских стран, при условии проведения renewable energy technology to the local conditions in African соответствующих исследований для приспособления этой countries. The paper also identifies the renewable resources технологии к местным условиям африканских стран. В available and their application in West African sub-Saharan статье описываются типы источников возобновляемой countries. However, this paper is not intended to provide exten- энергии и их использование в странах западной Африки и sive solutions but to raise awareness and to encourage considera- Африки южнее Сахары. Однако, статья не предлагает tion of the relationship between climate change and agriculture исчерпывающие решения, а лишь привлекает внимание к and therefore developing a document that spearheads means of проблеме и повышает осознание связи между изменением remarkably reducing deforestation, GHGs as well as negative климата и сельским хозяйством, и таким образом призыва-impact on the environment and public health if properly used. ет использовать экологически чистые методы хозяйство-
вания, уменьшающие обезлесение и эмиссию парниковых газов и положительно сказывающиеся на здоровье людей.
Introduction
Energy is the one of the most important factors to global prosperity. The dependence of fossil fuel as primary energy sources has led to global climate change, environmental degradation, and human health problems. According [25], in the year 2040, the world predicted will have 9-10 billon people and must be provided with energy and materials. Moreover, the recent rise in oil and natural gas prices may drive the current economy towards alternative energy sources. Therefore, the need for alternative energy sources from locally available resources cannot be overemphasized [27].
Many countries, especially in developing countries are faced with serious energy crises. They have been unable to meet the energy needs of their countries. In a quest to realize this, many have turn to different sources of energy which among them are renewable energy sources. Currently a high proportion of the world's total energy output is generated from fossil fuels such as oil and coal. The energy consumption level is among the lowest in the world with 4 % of the world population, (13 % for Africa) and a 2 % production of world commercial energy (7 % for Africa), ECOWAS accounts for only 1.7 % of world energy consumption (3 % for Africa) [8].
Africa is a continent with abundant, diverse and unexploited renewable energy resources that are yet to be used for improving the livelihood of the vast majority of the population. There is a consensus that achieving the Millenium Development Goals (MDGs) in Africa will require a significant expansion of access to modern and alternative renewable energy that if harnessed properly would reduce the use of fossil-fuel derived energy and reduce environmental impact, including global warming and pollution, improve sanitation, reduce demand for wood and charcoal for cooking.
Therefore, in most countries of the region campaign for using renewable energy resources is becoming stronger today because of the finite nature of fossil fuel energy resources as well as the greenhouse gases emission which many scientists believe cause global warming [20]. This campaign was as a result of the 1973 oil crises, chaos caused by the Arab oil embargo, in western countries brought a sudden global realization to use renewable energy resources such as solar energy, hydropower, wind energy, wave energy, biomass and biofuels [5]. Effective applications of renewable energy resources to augment energy supply from fossil fuel energy resources (using cleaner for fossil fuel technologies) will enhance availability of energy with minimum environmental effect.
Agriculture is responsible for an estimated 14 percent of the world's greenhouse gases. A significant portion of these emissions come from methane, which, in terms of its contribution to global warming, is 23
times more powerful than carbon dioxide. The U.S. Food and Agriculture Organization says that agricultural methane output could increase by 60 percent by 2030 [29]. The world's 1.5 billion cows and billions of other grazing animals emit dozens of polluting gases, including lots of methane. These gases can have significant social, economic and environmental consequences such as: altered length of growing season; extreme weather events altering how farming operations manage risk; increased flooding events in some areas, and increased occurrences of drought; in others; melting of the permafrost; increased storm surges in some areas and subsequent vulnerability to flooding and erosion; sea level rise of 0.1 - 1.0 m; more frequent and intense extreme weather events and disasters such as wind-storms, forest fires, snowstorms, hail, droughts, and floods; changes in ecosystems and ecosystem functions resulting in changes in biodiversity and habitats: greater potential impacts to species at risk and fisheries; new pest and disease outbreaks. Sources of agricultural greenhouse gases (ghgs) also known as global warming gases When the sun's rays strike the earth, light energy is converted into heat energy which is radiated into the atmosphere. Certain gases block the escape of this heat energy, resulting in a warming of the Earth's atmosphere known as the 'greenhouse effect'. Carbon dioxide, methane, nitrous oxide and other gases that contribute to the greenhouse effect are discharged by many natural and human activities, including agriculture. Greenhouse gas (GHG) emissions associated with livestock supply chains add up to 7.1 gigatonnes (GT) of carbon dioxide equivalent (CO2-eq) per year - or 14.5 percent of all human-caused GHG releases. The main sources of emissions are: feed production and processing (45 percent of the total), outputs of GHG during digestion by cows (39 percent), and manure decomposition (10 percent). The remainder is attributable to the processing and transportation of animal products [10].
Carbon Dioxide (CO2). Carbon dioxide is a greenhouse gas produced by the combustion of fossil fuels and biomass and from deforestation or clearing of agricultural land. It is a major contributor to the greenhouse effect and is therefore associated with climate change. Climate change refers to changes in the modern climate as a result of human activities that have increased GHG concentrations in the atmosphere. The vast majority of the scientific community agrees that climate change is caused by greenhouse gases (GHGs) in the atmosphere that trap heat by reflecting it back to the Earth, resulting in warming
Methane (CH4). Methane is a greenhouse gas produced during anaerobic decomposition (decomposition in the absence of oxygen) of organic wastes such as manures. Animals, particularly ruminants, emit methane gas during digestion which contributes to the greenhouse effect.
Nitrous Oxide (N2O). Nitrous oxide is a greenhouse gas produced in the soil from the biochemical reduction of nitrate to gaseous nitrogen compounds, a process known as denitrification.
These gases also exist naturally and are constantly exchanged between the atmosphere, the oceans, the soil, and living organisms. A net increase in the atmospheric concentrations of these gases is occurring due to human activities, including agriculture. The greenhouse effect, agricultural carbon and nitrogen cycles are shown on the following simplified figures.
Fig. 1. Example of an agricultural carbon cycle Fig. 2. Example of the agricultural nitrogen cycle.
Explanatory note: figure sources Explanatory note: figure sources
Renewable energy technologies as means for ghgs reduction in Africa
In Africa, water pollution and access to energy resources present challenges to human health, environmental health, and economic development. In 21 sub-Saharan African countries, less than 10 % of the population have access to electricity [18]. It is a continent with abundant, diverse and unexploited renewable energy resources that are yet to be used for improving the livelihood of the vast majority of the population. Therefore, the need for alternative renewable energy sources from locally available resources cannot be over emphasized.
In response to global demand for applications of renewable energy resources, Regional Sustainable Energy Centre of Excellence for Sub Saharan Africa (RSECE) was established in 2004. The centre's products and services are renewable energy applications (Biofuel, Biogas, Biomass, Geothermal, Hybrid systems, Hydropower, Photovoltaic, Solar Energy, Solar-thermal, Waste-to-energy, and Wind-power); climate change and energy transfer. In the same vein, Nigeria has established Energy Commission since 1979 with now six centres nationwide. The research centres have mandate to conduct researches and develop renewable energy technologies as well as disseminate information to both rural and urban populace the applications and important of renewable energy resources towards reduction of GHGs emissions [14]. Renewable energy is energy produced from naturally occurring sources that are regenerative or theoretically inexhaustible. Sources of renewable energy include: biomass (i.e. woodwaste, manure, food processing waste, etc.), hydroelectric, solar, wind, geothermal
Renewable energy sources can displace fossil fuel use, reducing GHG emissions on and off-farm. They can also help decrease reliance on energy sources with volatile prices, and create new economic diversification opportunities for agricultural producers. Opportunities for generating or using renewable energy on-farm will depend on the type and scale of operation as well as its location. Some agricultural producers may decide to generate energy or energy feedstock to sell off farm, while others may generate small quantities of energy in the interest of self-sufficiency and reduced energy costs. Renewable energy technologies suitable for on-farm use include.
Anaerobic Digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen; anaerobic digestion reduces the emission of landfill gas into the atmosphere. Anaerobic digestion is widely used as a renewable energy source because the process produces a methane and carbon dioxide rich biogas (biofuel - a fuel produced from crops or crop residues resulting in fuels like biodiesel and ethanol) suitable for energy production helping replace fossil fuels. Also, the nutrient-rich diges-tate can be used as fertilizer. Manure and other feed stocks are broken down in the absence of oxygen and methane rich gas is produced and captured for use in a boiler, cooking, lighting, co-generation facility or upgraded to natural gas for grid injection. Among the sources with great potential for electricity generation, the biomass energy has an important role in the world energy matrix as it accounts for 10-14 % of energy supply [17]. Currently the largest consumers of biomass based energy are the developing countries, where participation in the energy matrix reaches 40 %.
Environmental issues are among the factors that support the growing interest in biomass energy in the world. Biomass is more attractive and has gained worldwide attention for being the most renewable and provide a balance of zero CO2, based on sustainable use [6; 12].
All biological organisms that can be tapped as energy sources are called biomass. If biomass is burned efficiently, there is production of carbon dioxide and water, therefore, the process is cyclical and it can be stated that biomass is a renewable resource. The most popular forms of biomass are wood and its residues, waste generated by agriculture, agribusiness and animal husbandry, energy forests and municipal solid waste. In developing (West sub-African) countries simple home and farm-based anaerobic digestion systems offer the potential for cheap, low-cost energy for cooking and lighting [11; 7; and 13]. It has been estimated that only Nigeria produces about 542.5 million tons of including (227,500 tons of fresh animal waste daily) organic waste per annum. Since 1 kg of fresh animal waste produces about 0.03m3 biogas, This, in turn, has the potential of yielding about 25.53 billion m3 of biogas (about 169, 541.66 MWh) [19] and even more if other agricultural sources are included because many other raw materials available in Nigeria have been critically assessed for their possible use in biogas production [21]. These include water lettuce, water hyacinth, dung, cassava leaves and processing waste, agricultural residues (banana/plantain) peels, grain and rice husk, cow/pig/poultry wastes etc [4, 3; 23; 2; 1; 15; 16; 22].
Electricity. Electrical power is usually generated by utilizing steam produced from fossil fuel combustion, heat released from nuclear reactions, or from other sources such as wind or flowing water (hydroelectric).
Hydroelectric. Energy from running water is converted to electricity via small scale hydro power facilities, such as run-of -river projects. Hydroelectricity is a renewable energy source which releases negligible amounts of GHGs that contribute to climate change and is therefore a preferred source of power in Africa.
Geothermal Systems. Also known as Ground Source Heat Pumps, pump heat to or from the ground. They use the Earth as a heat source in the winter or a heat sink in the summer to either provide heat or cooling.
Gasification. A self-fuelled process where carbon rich feed stocks, such as manure and wood waste, are converted into a gas at high temperatures in an oxygen starved chamber. The produced gas, called syngas, is then burned to produce heat and electricity through co-generation or just heat via final combustion in a thermal oxidizer.
Wind. Wind is made when the Sun heats the Earth and the area above land gets hotter than the area above water. The hot air above land rises upwards leaving an area of low pressure. Cooler air moves into this area of low pressure making wind which we use to turn wind turbines and make electricity. Wind used to be used to turn windmills to grind wheat into flour. Energy from wind is converted to electricity via propeller blades that turn a generator.
Tidal. Tidal energy comes from the movement of water in the sea by the tides. These tides happen twice a day. The flow of water that is created by the tides is used to turn generators that make electricity.
Wave. Waves are created by the wind blowing across the sea and by the gravitational force of the moon. Wave power uses the energy of the waves to turn turbines that make electricity.
Solar. The sun's energy is converted to electricity via photovoltaic cells (PV) or captured as heat (Solar Thermal or Radiation). This solar radiation is abundantly available in Nigeria since the country is situated in the high solar radiation belt of the world which can be used as renewable energy resources. According to [14] Nigeria receives an average solar radiation of about 7.0kWh/m2-day (25.2 MJ/m2-day) in the far north and about 3.5 kWh/m2-day (12.6 MJ/m2-day) in the coastal latitudes.
Looking at the energy demand in the country, it is concluded that the estimate of potential solar energy in Nigeria with 5 % device conversion efficiency is 5.0 x 1014 kJ of useful energy annually [26]. This is equivalent to about 258.62 million barrels of oil produced annually and about 4.2 x 105 GWh of electricity production annually in the country [3]. According to [30] in Nigeria, solar radiation is fairly well distributed with average solar radiation of about 19.8 MJm -2 day-1 and average sunshine hours of 6hrs per day. If solar collectors or modules were 4 used to cover 1 % of Nigeria's land area, it is possible to generate 1850 x103 GWh of solar electricity per year; this is over one hundred times the current grid electricity consumption level in the country [30]. Classified technologies used for conversion of solar radiation into (i) solar electricity or photovoltaic (PV) and (ii) solar thermal systems which both have broad several applications [4].
Challenges with implementing alternative energy projects in Africa
Some of the problems faced with implementing renewable energy projects identify by many researchers such as [24] include the following:
1. Technical challenges: these range from lack of technical competence as a result of lack of understanding of local energy requirements; lack of research and development to adapt technologies to local conditions, resources and requirements; lack of local skilled labor to install, operate and maintain the equipment properly; and lack of access to spare parts.
2. Economic and Financial Challenges: Coupled with low income per capita stigma of most African countries, it is observed that economic and financial barriers might be another major issue to contend with the development of renewable energy systems in Nigeria. These challenges arise from lack of access to capital; lack of means of life support; lack of information by appropriate financial institutions; lack of investment; scale of energy systems; inappropriate subsidies by the government or other agencies; size of organizations. In Africa as a whole, investments in new technologies are very expensive. The cost for renewable energy systems may continue to be high because of high financial input and low profit margin in the course of manufacturing the component parts caused by low patronage and high cost of research and development.
3. National Policies and Awareness Programme Challenges: Activities of the government are highly instrumental to the success or failure of any matters of national interest including the programmes that will tend to enhance the very life status by introduction of new ways of living. Introduction of renewable energy systems is in the deployment programme for most African countries.
4. The rate of growth of the programme can only increase or decrease within the context of the government interest couple with complex bureaucracy and protocols as well as lack of awareness of the gains of the renewable energy systems by the rural dwellers.
5. Social, cultural and environment constraints: Social acceptance of the renewable energy technology is very important, as its absence can be a major challenge. If the local Community does not accept the technology; there will be no demand for its services. For example, it may not make much sense to install solar cookers in communities which forbid women to cook in the middle of the day. Most renewable energy installations failed because the beneficiaries are not carried along during the decision making to deploy the energy systems to them. Involving the end users may generate more interest as they tend to benefit more, having been given the chance to express their very need or convinced on what is being provided.
6. Political, institutional and legislative barriers: massive deployment of renewable energy systems in Nigeria has great future if only the right political and legislative framework can be put in place. Since the technology is foreign, there is need to put proper legislation (such as zero taxes and large subsidy) in place, to prevent turning the country into a dumping ground by the technologically advanced nations.
Conclusion and recommendations
African scientists are urged to carry out research in renewable energy technology to locally demonstrate the feasibility, application, and adaptation of this technology and help improve the quality of energy supply and reduce global warming in their respective countries. The following recommendations are proffered:
1. African governments should create more awareness on the advantages derivable from Renewable Energy Technologies (RETs) in order to discourage people from generators and also banning or placing restrictions on the importation of generators because of its contribution to global warming.
2. ECOWAS countries team up and subsidize the cost of importation of Renewable Energy Technologies (RET) most especially solar PV. They should also encourage private individuals to invest in the setting up of RETs.
3. Most importantly, governments should adequately fund our universities, polytechnics and research institutes to RETs that will be adaptable to our environment so as to increase the efficiency compared to the imported ones.
4. There is need for introduction of entrepreneurship and managerial skills development training programmes and technical courses in RETs with a view of developing Energy Service Companies (ESCOs) providing services to rural areas.
5. The region can take advantage of global partnerships such as the REEEP initiative of UK, to help some of the member countries for creative integration of renewable energy systems.
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