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УДК 628.385.954 (669)
M. B. GARBA, A. S. DOBYSHEV, A. A. SHUPILOV
ADVANCED TECHNOLOGY APPLICATION OF COW-DUNG AS A SOURCE OF ENERGY IN NIGERIA
М. Б. ГАРБА, А. С. ДОБЫШЕВ, А. А. ШУПИЛОВ
ПЕРЕДОВЫЕ ТЕХНОЛОГИИ ПРИМЕНЕНИЯ КОРОВЬЕГО НАВОЗА КАК ИСТОЧНИКА ЭНЕРГИИ В НИГЕРИИ
(Поступила в редакцию 13.07.2015)
The article describes a simple and inexpensive technology to Статья описывает простую и недорогую технологию
produce biogas and bio-fertilizer using fresh cow-dung in com- производства биогаза и биоудобрений с использованием bination with paunch content. The results of the experiment свежего коровьего навоза в сочетании с содержимым руб-revealed that the generated biogas can be sufficient for a family ца. Результат эксперимента показал, что полученного of 2-4 people per day having 1-2 cattle, so this low-cost tubular таким образом биогаза должно хватить на день семье из plastic reactor has been recommended to smallholder farmer 2-4 человек с 1-2 коровами, так что этот недорогой пла-due to its cheap cost of production (USD 80-100), and using стиковый трубчатый реактор был рекомендован для мел-local materials as well as ease of installation and operation. ких фермеров из-за дешевизны производства (USD 80-100) и
использования местных материалов, а также простоты установки и эксплуатации.
Introduction
In recent years, there is an increasingly serious problem with the lack of conventional energy sources. One of the most urgent and cost-effective ways to solve this problem is the production of liquid fuels (biogas) from biomass.
Biogas is produced by anaerobic digestion of agricultural waste and livestock. It is about 20 % lighter than air and has a flash point ranging from 650 0C to 750 0C. It is odorless, colorless and burns with a brilliant blue flame similar to LPG. Its calorie content is about 20 MJ / m3 and 55% more efficient than a conventional gas. The gas is a mixture of methane, carbon monoxide, hydrogen, nitrogen, hydrogen sulfide and water vapor. Biogas is a useful substitute for wood, gasoline, diesel fuel and electric power, depending on the nature of the purpose and its availability. Biogas can be used in internal combustion engines. There is train that operates in Sweden between Linkoping and Vastervik on biogas from cattle manure and sewage waste. Biogas has no particulate emissions and produces one-fifth as much nitrous oxide as diesel engine [11].
The feed stock that is used for the production of biogas can be used animal dung, food and wood processing industry wastes, tuber crops husks, sugarcane straws, hyacinth grass, water lettuce, cassava leaves and waste, banana and plantain wastes, rice husks etc.
In Africa, water pollution and access to energy create problems for human health, environment and economic development. In twenty one sub-Saharan African (SSA) countries, less than 10% of the population has access to electricity [8]. Figure 1 shows the total energy consumption in Nigeria in 2008.
8,2%. Natural gas
0,4%,Hydro energy
10,1%, Oil
81,3%, Combustible renewabl.
Fig. 1. Total energy consumption in Nigeria. Source: International Energy Agency [5]
On the continent there are a variety of untapped renewable energy resources that can be used to improve the livelihood of the vast majority of the population. Thus, the need for alternative renewable energy from locally available resources cannot be overemphasized.
The purpose of research is to investigate the possibility of producing biogas and bio-fertilizers for rural poor farmers in Nigeria having 1-2 cattle.
The analysis of sources
In the Sub-Saharan African developing countries, simple houses and farm-based settlements have the opportunity for cheap, low-cost energy for cooking and lighting based on anaerobic digestion systems. It is noted that, against the background of ever-increasing focus on renewable energy and for the production of biogas and bio-fertilizers, it is estimated that only Nigeria produces about 227,500 tons of fresh animal waste. And 1 kg of fresh animal waste produces about 0.03 m3 of biogas. Nigeria produces about 542.5 million tons of the above mentioned organic wastes per year. This, in turn, has the potential to bring about 25.53 billion cubic metres of biogas (approximately 169 541.66 MW) and 88.19 million tons of bio-fertilizer per year. Both which have a combined estimated value of about 4.54 trillion naira (29.29 billion USD). This potential quantity of biogas will be able to completely replace the use of kerosene and charcoal for cooking in homes, and reduces the consumption of wood fuel by 66% [10].
To use this potential and to increase the performance of biogas plants it is necessary to identify and analyze the factors influencing this process. The most important ones are the right choice of raw ingredients from which the biogas is to be produced and also level of training.
There is need for the utilization of agricultural biomass in Nigeria, because a large amount of fuel wood for cooking is consumed and also at the same time there is continuous increase in demand (table 1) of high-quality fertilizer as the situation deteriorated in the early 2000s (between 2002 and 2005) when the nitrogen, phosphorus and potassium (NPK) fertilizers used in Nigeria were imported in the absence of domestic production as a result of the closure of the only production company - National Fertilizer Company of Nigeria (NAFCON) for repairs [7]. The use of fertilizers in Nigeria is estimated at 13 kg/ha [4], which is above the average used in SSA - 9 kg/ha. This is much lower than elsewhere in the world (for example, 86 kg/ha in Latin America, 104 kg/ha in South Asia and 142 kg/ha in South-East Asia), and much lower than 200 kg/ha recommended by FAO [7, 3].
Table 1. Consumption of fertilizers in Nigeria (in metric tons)
Fertilizer 2002 2003 2004 2005
Nitrogen 94,400 137,603 101,001 115,041
Phosphorus 41,400 49,432 14,028 58,875
(Potassium 30,400 42,712 37,141 41,255
In table 2 shows the potential number of organic fertilizer (dry) obtained from various organic wastes in Nigeria, which amounted to 88.19 million tons per year.
Table 2 Total amount of organic fertilizer produced (dry) of various organic wastes in Nigeria
Organic waste (biomass) Total weight of generated biogas, million tons /year Total weight of dry biogas, million tons/year Mass of vapourised solid substances from dry mass, million tons/year Estimated quantity of bio-fertilizer (dry), million tons/year
Cow dung 197,6 49,4 39,52 25,69
Sheep and goat dung 39,6 7,13 5,7 3,71
Pig dung 15,3 3,06 2,3 1,68
Chicken droppings 32,6 3,26 2,28 1,89
Abattoir waste 83,3 12,5 10,63 6,12
Human faeces 52 13 10,92 6,42
Plant wastes 83 73,87 62,79 36,2
Communal services waste 39,1 11,73 8,8 6,45
Total 542,5 173,95 142,94 88,19
There are different kinds of biogas technologies for biomass processing which include biogas digester - a hermetically sealed container, where at a certain temperature an anaerobic digestion of prepared feedstock occurs and finally biogas are produced [9].
Such techniques allow processing of any kinds of organic materials, such as listed above (both solid and liquid) into biogas. However, the most efficient use of biogas technologies for processing livestock and poultry farms wastes should be characterized by timely availability of the waste as well as ease of collection. The quality of raw material feed to the biogas plant is characterized by humidity, biogas yield per unit of dry matter and methane content. Feedstock humidity should be at least 60 - 85% for tropical condition [9] and the yield of biogas depends on the type of feedstock used and the temperature during the fermentation.
Figs. 2 and 3 show the percentage distribution of individual organic waste (biomass) and an output poten-
Fig. 2. Distribution of various organic wastes (biomass) in Nigeria
10% , Poultry
oo/ cVi i droPPings 9%, Sheep &
goat manure
5%, . Municipal solid waste*
10%, Human faeces
4%, Pig manure
19%, Crop residue
■17% , Abattoir waste
Fig. 3. Distribution of the output potential of biogas from various organic wastes in Nigeria Table 3. Yield biogas potential of various organic wastes (biomass) in Nigeria
Organic waste (biomass) Population, million Total yield of biomass million tons/year Estimated biogas output, billion m3/year
Cattle manure 21 197,6 6,52
Sheep & goat manure 100,9 39,6 2,3
Pig manure 9,6 15,3 0,92
Poultry droppings 112,6 32,6 2,5
Abattoir waste - 83,3 4,42
Human faeces 139 52 2,6
Crop residue - 83 4,98
Municipal solid waste - 39,1 1,29
Total 542,5 25,53
Organic matter is made up of protein, fat, and light and heavy degradable carbohydrate percentage of which is determined by the gas output from the feedstock and the percentage of methane in it. Its maximum quantity in biogas is obtained from protein - 71%; fats - 68%, and carbohydrates - only 50% [9]. However, for better gas output, it is necessary as far as possible to mix feedstock with a high content of fats and proteins, such as grain, sugar cane, manioc and yam wastes. Therefore, mixing of various feedstocks and its homogenization has a significant impact on increasing the production of biogas (table 3). For example, when cow dung is used in conjunction bird droppings, biogas yield was 0.528 m3/kg, while using only cow dung does not exceed 0,380 m3/kg, and the homogenization of cow dung has improved the production of biogas from 0.174 to 0,380m3/kg [1].
Table 3. Increase in of biogas production by mixing different waste
Waste Biogas production, m3/kg Biogas output increase, %
Cow dung + chicken droppings 0,634 6,0
Birds droppings 0,617
Cow dung + chicken droppings + pig dung (1:0.5:0.5) 0,585 11,0
Pig dung 0,560
Cow dung + birds droppings 0,528 6,0
Cow + pig dung 0,510 7,0
Cow dung 0,380
Cow dung + piny wood 0,363 5,0
Piny wood 0,277
Main part
The biogas digester presented herein uses fresh cow dung, water and fresh paunch content in the ratio 1:2:1 respectively as shown in [9], and can be represented by the following structural diagram (fig. 4).
Gas collector_^ biogas
Feed to the digester
Bio-fertilizer
^ Effluent
Fig. 4 - A H-----st^oZyZh
Based on the above, within the capacity of Nigerian rural peasant smallholder farmers who have 1-2 of cattle may invest in processing their animal waste (cow dung and paunch content) to produce biogas and fertilizers. From the feed stock composition parameters analysis and the identified factors that contribute to increased biogas production, a process flow diagram for its production with the use of cheap (USD 80-100) PVC and plastic film [2] is hereby proposed with ease of construction and maintenance.
Biogas production time was 40 days (evolution of flammable gas was noticed after 2 hours) at a temperature of 30-35°C and 60 % relative humidity, depending on the season. In practice, experience has shown that the retention to 60-100 days occurs when there is lack of substrate. Longer retention times may also increase the biogas production by 40% [6].
Conclusion and recommendations
According to the research results, it can be concluded that the use of cow dung combined with paunch content is possible to obtain enough biogas for a family of 2 to 4 per person per day with 1-2 cattle. Therefore, such polyethylene tubular-reactor is proposed for its low cost of production using local materials and simple in construction, operation and needs no serious maintenance.
LITERATURE
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