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Technical and economic evaluation of the use of CNG as potential public transport fuel in Nigeria
Scientific African 6 (2019) e00212
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Scientific African journal homepage: www.elsevier.com/locate/sciaf
Technical and economic evaluation of the use of CNG as potential public transport fuel in Nigeria Anthony Igbojionu a, Charley Anyadiegwu a, Emmanuel Anyanwu b, Boniface Obah a, Chukwuemeka Muonagor a,∗ a b
Petroleum Engineering Department, Federal University of Technology, Owerri, Nigeria Mechanical Engineering Department, Federal University of Technology, Owerri, Nigeria
a r t i c l e
i n f o
Article history: Received 21 March 2019 Revised 9 October 2019 Accepted 24 October 2019 Available online xxx Editor: Dr. B. Gyampoh Keywords: Compressed natural gas Economic analysis Vehicles Stations Net present value Transportation
a b s t r a c t The need to develop alternative automobile fuel other than petrol and diesel in Nigeria is based on the rising cost, environmental pollution, and perennial scarcity of petrol, diesel, etc. Technical analysis of the introduction of compressed natural gas vehicles as a means of public transportation in Nigeria is conducted in this work. Port Harcourt – Onitsha expressway, a major interstate route in Nigeria is used as a case for analysis. 400 compressed natural gas vehicles are estimated to ply the route daily, which makes the total energy requirement per day to be 3856 gasoline gallon equivalent/day. It is recommended from the refueling stations design that five refueling stations with an average dispensing rate of 800 gasoline gallon equivalent/day are installed along the route to take care of the total requirement of 3856 gasoline gallon equivalent/day. Compressor duty analyses are conducted using Hysys, a process simulation software to determine the energy required by the compressors to boost the pressure of the gas from 14.70 psia at the sales point to 3600 psia which is the outlet pressure of the stations. From the analyses using economic indicators, the project is also found to be economically viable. It has a very high net present value of $2.27 million, short pay-out of 4.24 years, internal rate of return of 14.42% and profit per dollar investment after seven years of 0.72. The entire results indicate that adopting compressed natural gas vehicles for public transportation in at least the major interstate routes in Nigeria, will help to reduce the transportation problems encountered in Nigeria due to the pressure on gasoline and diesel. © 2019 Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative. This is an open access article under the CC BY-NC-ND license. (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Introduction Problems of gasoline and diesel combustion emissions “Gasoline and diesel are complicated mixtures of hydrocarbons, including aromatic, naphtenic, olefinic and paraffinic components” [1]. Gasoline typically contains hydrocarbons with 5–12 carbon atoms; while diesel fuel 12–18 carbon atoms. “Normal combustion of petroleum products takes only about 3/10 0 0 of a second” [2]. ∗
Corresponding author. E-mail address: [email protected] (C. Muonagor).
https://doi.org/10.1016/j.sciaf.2019.e00212 2468-2276/© 2019 Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative. This is an open access article under the CC BY-NC-ND license. (http://creativecommons.org/licenses/by-nc-nd/4.0/)
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Anetor [3] carried out experiment on general causes and implementation of high blood lead (Pb) levels in Nigerian population and found out that “depending on the formation composition, lead could be present in gasoline derived from the earth’s crust”. “This is usually small and in most cases insignificant. Lead (Pb) is a highly toxic chemical with no physiological benefits. There are several pathways by which lead is ingested by the population. But the major pathway is airborne lead, which is mostly produced by vehicles using leaded petrol” [4]. According to Enemari [4] “the combustion of petrol is inefficient in most cases and gases and particulate are emitted as exhaust gas/particulate. One of the perturbing ones is lead particulate, which has detrimental physiological effects. In countries such as Nigeria where gasoline that contains high lead levels is still used, atmospheric lead pollution from vehicular exhaust aerosols is a major source of lead pollution”. His-study revealed “disturbing blood lead levels (BLLs) in the general population”. Enemari [4] concluded that “scientific and medical evidence accumulated during the past several decades suggest that environmental lead pollution from highly leaded gasoline sold in Nigeria has elicited adverse health outcomes particularly in children”. He averred that “ingestion of lead has been linked to several physiological disorders in man such as interference with IQ of children of school age, gastrointestinal disorder, nausea, circulatory collapse, fatigue, blindness, CNS disorder, anaemia, etc. The use of leaded petrol therefore, needs to be reviewed in Nigeria like in other countries of the world to reduce the health effects. It is possible to produce petrol of high and desirable octane number without the use of TEL lead using appropriate technology e.g. cracking of higher molecular crude, use of methyl tetra–butyl ether (MBTE), Fluid Catalytic Cracker (FCC), and so on. In Nigeria, the two refineries in Port Harcourt have been modified to produce only unleaded petrol if the FCC is functioning properly”. According to Kupolokun [5], “Nigeria’s two refineries in Kaduna and Warri already have the capability to produce unleaded petrol, but would need modifications to be able to produce 100% unleaded gasoline”. “The defunct Federal Environmental Protection Agency (FEPA) undertook a study of levels of lead in six Nigerian cities of Lagos, Port Harcourt, Aba, Abuja, Ibadan and Kaduna. The soil samples were taken from roadside, motor parks, markets, etc. The lead content was, as staggering as it was frightening” [6]. Tests carried out by Uwagboe [6] using Atomic Absorption Spectrometry showed that “the concentration level of lead (in μg/g) around Warri collaborated this earlier result by the then FEPA. It illustrated that lead levels showed positive gradient with traffic density variations - especially along Effurun–Sapele road, classified as a high-density traffic road”. Removing lead does not remove vehicular emission as hydrocarbon, oxides of nitrogen and sulphur will still be emitted. There is need to do something about these too since they also represent environmental problems aiding photochemical reaction. Tambari et al. [7] found out that “the un-burnt gasoline, carbon monoxide, leaded compounds from leaded gasoline and other gases which pollute the air are deadly and harmful to humans, animals and food crops. Lead poisoning causes retarded mental and physical development, reduced attention spaces, increased blood pressures, hypertension, higher risk of cardiovascular diseases and premature deaths”. “The World Health Organization (WHO) estimates 15–18 million children in developing countries suffer from permanent brain damage due to lead poisoning” [8]. Need for CNG use as transport fuel in Nigeria For a developing country like Nigeria, creating a natural gas market is not an easy undertaking. Investments in gas projects are inherently capital intensive, requiring large increments for each expansion. The necessary conditions to overcome this initial hurdle are based on economic and investment policy choices used to exploit it rather than on the size of gas reserves. This largely explains the truism implicit in the fact that Nigeria’s natural gas reserves place her 9th in the world, yet she is not among the top 20 gas producers in the world! It is therefore, the methodology of gas market development that is crucial to creating economic viability and sustainability for a developing country, particularly those richly endowed with hydrocarbon reserves like Nigeria. The path toward a sustainable economy is therefore, deeply entwined in harnessing these resources, attracting the needed financial capital as well as nurturing productive utilization. According to Eromosele [9], “for many decades, Nigeria’s economy has been largely mono-cultural, depending essentially on crude oil, that murky substance which Eromosele [9] described as ‘a useless mixture of useful products’. The volatile nature of the global crude oil prices makes Nigeria’s economy very susceptible to the characteristic vagaries of the international oil market as well as to the dreaded Dutch disease syndrome (DDS). In Nigeria there is incessant scarcity and high cost of energy from existing gasoline and diesel. There are grave environmental issues associated with petroleum fuels. There is thus, the urgent need to find alternative energy to supplement gasoline and diesel as transportation fuel for automobiles in Nigeria”. “CNG has been acclaimed as a clean-burning, environmentally friendly and cheap fuel and its use to power vehicles is globally gaining momentum by the day. Therefore, the perennial problems of fuel scarcity and tailpiece pollution in Nigeria will be effectively tackled by utilizing CNG” [10]. Gaius-Obaseki [10] observed that “given the abundance of gas in Nigeria, the utilization of Compressed Natural Gas (CNG) as automobile fuel provides a clean and environmentally feasible alternative to conventional fuels”. He noted “that the world over, the transport industry is the single biggest consumer of oil, even as it has been fingered as a major source of total CO2 emissions are from road transport”. Review of literatures Review of literatures on worldwide use of CNG automotive engines According to Kafood [11], “natural gas has been considered as the most promising alternative fuel for its cleanliness and abundance. In recent times, natural gas has found applications in a range of industries including the transportation industry
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Table 1 Environmental impacts of use of diesel/gasoline vehicles in Nigeria. Environmental impact
Description
Impacts on human lives
Global warming potential
“Global warming contributes to the rise of the sea level, to an increased occurrence of extreme weather conditions. It leads to shifts and extinctions of biotopes and to drinking water shortage” [16]. “CO2 is the largest contributor to global warming and is mainly originating from the combustion of fossil fuels used for human activities. Nitrous oxide and methane, both emissions exhausted by road vehicles, are also contributing to climate change” [17]. “Carbon monoxide causes oxygen shortage and can lead to suffocation. The concentration of CO in the atmosphere can vary strongly and depends mainly on the traffic situation and on the wind” [18]
“Possible effects on human health are among others: increased occurrence of respiratory effects and cardiovascular diseases due to heat waves and increased number of infections and diseases due to floods” [16].
Air quality contamination and human toxicity
“CO concentrations in the blood of people living in the city can be twice as high as concentrations in the blood of people living in the countryside. The concentration of CO can reach very high levels in closed spaces like underground parking lots, or inside vehicles” [18]. “NOx form acids, when absorbed in the mucous “Nitrogen oxides (NOx) form a group of important membranes of the nose or the oral cavity, and cause pollutants mainly produced by road transportation” [19]. irritation of the bronchial tubes, coughing, and in higher “Nitrogen oxides also lead to eutrophication of soil, concentrations also lack of breath and even death” [19]. ground- and surface water and as a result leads to “People suffering from asthma can be very sensitive to negative impacts on aquatic and terrestrial ecosystems, NOx” [21]. surface water and agricultural and forestry yields” [20]. “Particulate matter (PM10) can remain in suspension in the “As PM10 particles are very small, they can penetrate very air for hours or even days” [19]. deep into the lungs. Because PM10 is often bound to other harmful substances, exposure and inhalation can lead to an important number of health problems and even to death” [19]. “Sulphur oxides (SOx) cause acidification which in turn “Sulphur oxides (SOx) are very soluble in water and damages aquatic and terrestrial ecosystems, surface consequently can easily be absorbed through the mucous water, agricultural and forestry yields and buildings” [20]. membrane of our bronchial tubes. People suffering from asthma are especially sensitive to SOx” [20]. “Volatile organic compounds (VOC) is the name regrouping “Some of the VOC present some important health damaging effects such as carcinogenicity” [21]. a large number of chemical compounds, like toluene, xylene, benzene, etc. Some of the previously described emissions also have indirect effects as they lead to other chemical reactions, once emitted into our atmosphere. The formation of tropospheric ozone for instance is triggered by sunlight and is an important secondary pollution of nitrogen oxides and hydrocarbons emissions (photochemical pollution). Ozone is toxic for living organisms and human beings and causes damage to the cells of the bronchial tubes” [21].
where they have been replacing diesel, gasoline and other fuels. Majorly as a result of the relatively low costs of CNG and the ever-spreading awareness campaigns on air pollution, a lot of motors today run on CNG and the amount of vehicles being fuelled with CNG continue to increase by the day”. “As at 2011, there existed over 14 million vehicles running on natural gas in the world. Iran was the country with the most number of natural gas vehicles (NGVs) with about 2.86 million NGVs. Pakistan followed closely with about 2.85 million NGVs, Argentina stood at the third spot with a little over 2 million cars running on natural gas, followed by Brazil with about 1.7 million NGVs and then India farther away with 1.1 million NGVs” [12]. “The Asia-Pacific region leads with 5.7 million NGVs, followed by Latin America with almost four million vehicles” [13]. “Due to high oil prices, gas has been considered lately as a good substitute for transportation fuel. In China for instance, the number of cars that run on natural gas is about 1 million. In short-haul fleets in the urban areas, the use of CNG is rapidly increasing while LNG is majorly used for long distance vehicles which represent most of truck diesel demand” [14]. “Several manufacturers sell bi-fuel cars. It is now much easier to convert gasoline vehicles to dual-fuel vehicles ie gasoline/CNG vehicles. A lot of auto-engineering workshops now do the retrofitting. Installing CNG conversion kits can be very costly, the cost of installing one can reach over $80 0 0 on average vehicles. However, CNG costs about 50% less than gasoline and emits up to 90% fewer emissions than gasoline” [15].
Evaluation of environmental effects of the use of diesel/gasoline vehicles in Nigeria The evaluation of the environmental effects of the use of diesel and petrol vehicles in Nigeria is presented in Table 1.
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Methodology Development of natural gas as transportation fuel in Nigeria Natural gas is transformed to automotive transportation fuel using compression equipment. The procedure employed in this work for the development of natural gas as transportation fuel in Nigeria comprises: 1. Estimation of the total number of vehicles that ply identified route on a daily basis which provides the information on the quantity of CNG fuel utilized for the day. 2. Determination of the gasoline gallon equivalent (GGE) requirement of the CNG vehicles to enable the quantity of CNG utilization to be known. 3. Design of pipeline network and refueling stations to be installed. 4. Laying of natural gas pipelines from gas supply (gas gathering) plants to the sites where the CNG refueling stations would be sited. The route used as case for the project is Port Harcourt to Onitsha Expressway. CNG refueling stations would have to be installed along the expressway while gas pipelines are laid across to transport gas to the CNG refueling stations where it would be compressed and stored for refueling the CNG vehicles that would ply the route. Estimation of total GGE per day In the course of this work, emphasis are on commercial vehicles. Most of the commercial vehicles that ply the Port Harcourt - Owerri - Onitsha route have an average vehicle-passenger capacity of 14 passengers. The number of vehicles that ply the Port Harcourt - Onitsha route to and fro is estimated; and this estimate enables us to determine the total GGE requirement for the day. This is achieved by taking an estimate of the number of individual commuters from Port Harcourt to Onitsha and from Onitsha to Port Harcourt daily, and analyzing this with the average passenger capacity of the vehicles. The number of similar vehicle models plying the route from Port Harcourt - Onitsha daily can be estimated as follows:
NV = NPT /VPC
(1)
Where, NPT = Total number of passengers (commuters), VPC = Vehicle passenger capacity. The fuel tank of the light duty CNG vehicle used for this analysis holds 8.0 gasoline gallon equivalent (GGE) of CNG at 3600 psi, and can cover an average of 200 miles (322 km) with a full CNG tank; which translates to 0.0248 GGE per km. According to Igweonu and Mbabuike [22], “one GGE equals 0.77Scf of CNG at 3600 psi and 126Scf of natural gas at standard temperature and pressure”. The GGE requirement for light-duty vehicles (LGGE ) is estimated as:
LGGE = LGGEk ∗ NV ∗ 2Lp
(2)
Where, LGGEk = GGE requirement for light duty vehicle per km, Lp = Distance from Port Harcourt to Onitsha. Since one GGE equals 0.77Scf of CNG at 3600 psi, the CNG requirement in scf is estimated as:
CNGLVol = LGGE ∗ 0.77
(3)
The GGE requirement for heavy duty vehicles (HGGE ) is also determined as:
HGGE = HGGEk ∗ NV ∗ 2Lp
(4)
Where, HGGEk = GGE requirement for heavy duty vehicle per km. The CNG requirement in scf is estimated as:
CNGHVol = HGGE ∗ 0.77
(5)
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Design of pipeline network The gas used as CNG was obtained from a gas treatment plant located at a field in the Niger Delta region of Nigeria. This particular gas processing plant is chosen because of its closeness to the route. The plant is 10 km (6.21miles) from Port Harcourt. Before transportation, the gas is compressed to the required pipeline inlet pressure, P1 by the user. The distance between the treatment plant and the route, added to the distance from Port Harcourt - Onitsha, gave a total distance to 126.68 miles. The average temperature of the gas in the pipeline gotten from simulation using HYSYS is 179.9°F. The hourly flow rate of the gas is the total volume of gas per hour needed by the CNG stations for the CNG vehicles. This is expressed as:
Q = CNGLVol ∗ 126/(0.77 ∗ 24 )
(6)
This flow rate is expressed in scf/hr as shown in the pipeline dimensions and gas properties represented in Table 3 below. Weymouth equation was used in this work for the estimation of pipeline inlet pressure and selection of pipe dimensions. The single pipeline arrangement which is adopted in this work is the most conventional pipeline arrangement because it makes use of only one straight pipe of same diameter from the beginning to the end. It is also the cheapest pipeline arrangement. The initial pressure, P1 is estimated using Weymouth equation for single pipeline arrangement as [23]:
P1 = (Q ∗ Pb /18.062Tb )2 ∗ SG ∗ Z ∗ Tavg ∗ L/D16/3 + P2 2
0 . 5
(7)
Where Q = flow rate, scf/hr Pb = base pressure, psia Tb = base temperature, 0 R SG = gas specific gravity Z = gas compressibility factor Tavg = gas average temperature, 0 R L = pipe length, miles D = pipe diameter, inch P2 = pipeline outlet pressure or minimum station inlet gas pressure, psia The number of pipes (Np ) to be laid to cover the entire distance is estimated as:
Np = 5280 ∗ L/Lp
(8)
Where Lp = length per pipe, ft Compressor selection using HYSYS HYSYS is applied in the selection of the compressor to compress the gas to the required initial pressure, P1 before it enters the pipeline for transmission and the selection of compressor to compress the gas at the outlet of the pipe, P2 (which is the same as the inlet pressure of the CNG station) to the refueling station outlet pressure, P3 which is set at 3600 psi. Number of refueling stations The number of CNG refueling stations (NCS ) to be installed is determined as:
NCS = LGGE /Rmax
(9)
Where Rmax = maximum dispensing rate of CNG refueling station Economic appraisal of the CNG transportation project The essence of conducting the economic appraisal is to determine whether the project is economically viable to be invested in or not. Costs and revenue analyses Introducing CNG fuel as alternative transportation would be capital intensive. A lot of things add up to the total expenditure required to bring CNG vehicles to service. They include: i. Costs of Pipeline and Compressor Station (CPC): These include the cost of laying the pipeline from the sales point to the locations of the CNG refueling stations and the cost of the compressor that would be installed at the initial point of the pipeline.
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Compressor station: A reciprocating compressor of less than 10 0 0 hp for which daily input / output is up to 500 MScf/day is chosen. Pipelines and metering stations: “Pipe segments with average length of 20 miles and diameters of 12 in., 14 in. or 18 in. that can cover the length of about 120 miles are commonly used, and metering stations are installed. Different pipes of lengths up to 40 ft make up the various pipe segments” [24]. Costs of pipelines and compressor station can be estimated as:
CPC = CPC per km ∗ L
(10)
Where CPC per km = costs of pipeline and compressor station per km ii. Cost of CNG Refuelling Stations (CCR ): This includes the cost of purchasing and installing the CNG refuelling stations with their associated compressor stations along Port Harcourt-Onitsha Expressway. The number and storage capacity of the CNG refuelling stations depend on the number of vehicles that ply the route in a given time. Cost of CNG refuelling stations can be estimated as:
CCR = CCR per station ∗ NCS
(11)
iii. Cost of CNG Vehicles (CCV ): This is the total cost of the CNG vehicles that would be purchased and shipped down to Nigeria which would be plying Port Harcourt-Onitsha Expressway. It is assumed that the vehicles would be purchased on a one-time basis and they would have life span of seven (7) years each before they are discarded as scrap. Cost of CNG vehicles can be estimated as:
CCV = CCV per vehicle ∗ NV
(12)
The total Capital Cost, CAPEX is given by:
TCC = CPC + CCR + CCV
(13)
Annual Operating cost, OPEX is given by:
AOC = GAC + RFML + MPC + VDAC
(14)
Where, GAC = Annual Cost of Gas RFML = Fuel, Maintenance and Labour Costs for CNG Refueling Stations MPC = Maintenance Costs for Pipelines and Compressors VDAC = CNG Vehicles Drivers and Assistant Drivers’ Wages and Car Maintenance Costs According to United States Department of Energy [25], “one GGE equals 126 Scf of natural gas at pressure of 30psia”. “The price of natural gas is $4/MScf” [26]. Annual cost of gas is estimated as:
ACG = LGGE ∗ 126 ∗ Gp ∗ 353
(15)
Where Gp = Price of natural gas $0.004/scf 353 = Number of plying days of the vehicles considering 12 days of routine maintenance of the vehicles per year. “Fuel, maintenance and labour costs for CNG refueling stations (RFML ) are estimated as 13% of the costs of CNG refueling stations” as [27]:
RFML = 0.13 ∗ CCR
(16)
According to Cornot-Gandolphe et al. [28], “maintenance costs for pipelines and compressors are estimated as 20% of the costs of pipelines and compressor stations per km” as shown:
MPC = 0.2 ∗ CPC
(17)
According to Consumer Reports [29] “CNG vehicle drivers and assistant drivers’ wages and car maintenance costs are determined as 24% of gross revenue” as:
VDAC = 0.24 ∗ GR
(18)
Gross Revenue, GR = Vfreq ∗ NV ∗ VPC ∗ TF ∗ 353
(19)
Where, Vfreq = Frequency of Transportation per day per Vehicle NV = Total Number of Vehicles VPC = Total Number of Passengers per Vehicle TF = Transport Fare of each Passenger 353 = Number of plying days of the vehicles considering 12 days of routine maintenance of the vehicles per year. Net revenue for subsequent years of operation,
NR = GR − OPEX
(20)
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Table 2 CNG vehicles parameters. Number of vehicles (P/H to Onitsha) Number of Vehicles (Onitsha to P/H) Total GGE Requirement Total scf of CNG Requirement
400 400 3856 GGE 2970 scf
Table 3 Pipeline and gas parameters for transportation. Flow rate, Scf/hr Base pressure, psia Base temperature, 0 R Gas specific gravity Gas Z-factor Average temperature, 0 R Pipeline length to station, miles Diameter of pipeline, in Min Station inlet gas pressure
20,239 14.7 520 0.69 0.92 639.9 126.68 12 30 psia
Economic indicators Net present value (NPV) “Net Present Value (NPV) is a measure of profitability of any project. A project is generally welcomed if the NPV is positive and rejected if the NPV is negative because the project will also have negative cash flows” [30]. The NPV is the sum of the present values of the project at the different years. Pay-out (PO) “The Pay-out (PO) for a project refers to the time (in years) at which the initial investment on the project is just recovered” [31]. It is the time at which cumulative NCR becomes zero. Profit per dollar invested In this work, the P/$ after 7years is the ratio of the total net cash recovery from the first (1st) to seventh (7th) year and the sum of CAPEX and OPEX as represented below:
P/$ = NC Rtotal /[(CAP EX + (OP EX ∗ 7 )]
(21)
Where NCRtotal = total net cash recovery of the project for the 7 years. Internal rate of return (IRR) The rate of return of a project at which the NPV of all cash recoveries amounts to zero is the internal rate of return (IRR) on investment for the project. The higher the IRR of a project, the more desirable it is to undertake such project. Presentation of results Estimation of total GGE per day The number of vehicles required would be estimated with Eq. (1) as: Number of vehicles, NV = 5500 / 14 = 392 vehicles The 392 vehicles are approximated to 400 vehicles. From Eq. (2), LGGE = 0.0248 ∗ 400 ∗ 2 ∗ 194 km = 3856 GGE From Eq. (3), CNGLvol = 3856 ∗ 0.77 = 2970 scf of CNG. The summary of the parameters of the CNG vehicles is shown in Table 2 below. Design of pipeline network and compressor stations Pipeline network for gas transportation The pipeline dimensions and gas properties are as shown in Table 3 below. From Eq. (7), for single pipeline network of 126.88 miles, the initial pressure given the CNG Station 5 gas inlet pressure as 30 psi is: P1 = [(20,238.75 ∗ 14.7/18.062 ∗ 520)2 ∗ 0.69 ∗ 0.92 ∗ 639.9 ∗ 126.88/1216/ 3 + 302 ]0. 5 = 31.47psia. Number of pipes (NP ) required for the entire pipe length is estimated from Eq. (8) to the nearest whole number as follows: NP = 5280
∗
126.88/40 = 16,749.
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Fig. 1. Compressor and Pipeline Design Flow sheet.
The compressor selection Using HYSYS, the compressor duty, which is the power consumption at a particular pressure is evaluated. The compressor selection involves determining the particular compressor duty required to boost the pressure of the gas from 14.70 psia which is its pressure from the separator to 32.62psia which is the pressure required at beginning of the pipeline. The compressor and pipeline flowsheet is redrawn using Microsoft Word and as shown in Fig. 1. The compressor selection is performed again to determine the maximum compressor duty required to boost the pressure of the gas from 30psia which is the lowest possible pressure of the gas from the pipeline to 3600 psia which is the outlet pressure of CNG fuel at the station. The compressor and pipeline flowsheet is redrawn using Microsoft Word and as shown in Fig. 2. CNG refueling stations selection The number of CNG refueling stations to be installed is estimated from Eq. (9) to the nearest whole number as: NCS = 3856 / 800 = 5. The five medium stations would be installed at km 1 (0.621mile), km 49 (30.43 miles), km 97 (60.23 miles), km 146 (90.67 miles) and km 194 (120.47 miles) respectively along the 194 km-expressway. The summary of the technical parameters of the CNG vehicles and the refueling stations is shown in Table 4 below: Results of the economic analyses Capital costs i. Costs of Pipelines and Compressor Station: Deduced from Cornot-Gandolphe et al. [28], the total cost of pipeline and compressor station is $700 per km.
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Fig. 2. Compressor Design Flow sheet for CNG Station.
From Eq. (10), total pipeline systems cost is estimated as: CPC = $700 per km ∗ 204 km = $142,800. ii. Cost of CNG Refueling Stations: According to Smith et al. [27], “a medium CNG refueling station with an average daily dispensing rate of 800 GGE/day which is the type of station recommended for this project costs $90 0,0 0 0 . From Eq. (11), the total cost of the CNG stations is estimated as: CCR = $90 0,0 0 0
∗
5 = $4.5 million.
iii. Cost of CNG Vehicles: The number of CNG vehicles that would be purchased is 400, “with CNG vehicles cost of $27,0 0 0 each” [29]. From Eq. (12), the total cost of the CNG vehicles is: CCV = $27,0 0 0 ∗ 40 0 = $10.8 million. From Eq. (13), total capital cost, TCC is: TCC = $142,800 + $4.5 million + $10.8 million = $15.44 million. Annual operating costs i. Annual Gas Cost: The total GGE requirement for the 400 cars that would ply to and fro Port Harcourt and Onitsha is 3856.
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A. Igbojionu, C. Anyadiegwu and E. Anyanwu et al. / Scientific African 6 (2019) e00212 Table 4 Summary of the technical parameters. Parameters
Value
Number of Vehicles (P/H to Onitsha) Number of Vehicles (Onitsha to P/H) Total GGE Requirement Total scf of CNG Requirement Flow Rate across the Pipeline Pipeline Inlet Gas Pressure Number of Pipes Number of CNG Stations Required Dispensing Rate per Station CNG Station Inlet Gas Pressure CNG Station Outlet Gas Pressure
400 400 3856 GGE 2970 scf 20,239 scf/hr 31.47 psia 16,749 5 800 GGE/day 30psi 3600 psi
Table 5 Summary of the cash flows for the CNG project. Time (yr)
CAPEX ($MM)
OPEX ($MM)
GROSS REV ($MM)
NCR ($MM)
CUM NCR ($MM)
PV @ 5% ($MM)
PV @ 10% ($MM)
0 1 2 3 4 5 6 7
15.44 0 0 0 0 0 0 0
0 2.86 2.86 2.86 2.86 2.86 2.86 2.86
0.0 6.50 6.50 6.50 6.50 6.50 6.50 6.50
−15.44 3.64 3.64 3.64 3.64 3.64 3.64 3.64
−15.44 −11.80 −8.16 −4.52 −0.88 2.76 6.40 10.04
−15.44 3.47 3.30 3.14 2.99 2.85 2.72 2.59
−15.44 3.31 3.01 2.73 2.49 2.26 2.05 1.87
Table 6 Cumulative NCR after 7 years. Time (yr)
NCR ($MM)
CUM NCR ($MM)
0 1 2 3 4 5 6 7
−15.44 3.64 3.64 3.64 3.64 3.64 3.64 3.64
−15.44 −11.80 −8.16 −4.52 −0.88 2.76 6.40 10.04
From Eq. (15), Annual gas cost, ACG is estimated as: ACG = 3856 ∗ 126 ∗ 353 ∗ 0.004 = $686,029. ii. Vehicles Fuels and Maintenance Costs and Drivers’ Allowances: The gross revenue is first determined according to Eq. (19) as: Gross Revenue, GR is: GR = 2 trips ∗ 400 vehicles ∗ 14 passengers ∗ N600 ∗ 353 days = N2.37 billion ie $6.5 million per year (at a rate of $1 = N365.00). From Eq. (18), Vehicles Fuels and Maintenance Costs and Drivers’ Allowances is determined as: VDAC = 0.24 ∗ $6.5 million = $1.56 million per year. iii. Pipeline Monitoring and Compressor Maintenance Cost is determined from Eq. (17) as: MPC = 0.2 ∗ $142,800 = $28,560. iv. Cost of CNG Refuelling Stations Maintenance and Fuel is determined from Eq. (16) as: RFML = 0.13 ∗ $4.5 million = $585,0 0 0. From Eq. (14), annual operating cost, AOC is given as: AOC = $686,029 + $1.56 million + $28,560 + $585,0 0 0 = $2.86 million. Revenues and cash flow analysis The gross revenue, GR is determined according to Eq. (19) as: GR = 2 trips ∗ 400 vehicles ∗ 14 passengers ∗ N600 ∗ 353 days = N2.37 billion ie $6.5 million per year (at a rate of $1 = N365.00). The net revenue is determined according to Eq. (20) as:
A. Igbojionu, C. Anyadiegwu and E. Anyanwu et al. / Scientific African 6 (2019) e00212
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Fig. 3. Plot of Time (Yrs) against Cum-NCR (Millions of Dollars).
Fig. 4. Plot of NPV against Discount rate.
Net Revenue = $6.5 million - $2.86 million = $3.64 million. The cash flows for the project for 7 years are shown in Table 5. Determination of the economic indicators Calculation of net present value From Table 5, the Net Present Value, NPV at an expected rate of return/discount rate of 10% which is the sum of all the Present Values in the last column at the left = $2.27 million. Pay-out (PO) Table 6 shows the cumulative NCR and NCR after 7 years while Fig. 3 represents the graph of time against cumulative NCR in millions of dollars for the gas injection project.
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Fig. 5. Plot of NPV ($MM) against Natural Gas Price ($/scf).
Fig. 6. Plot of NPV ($MM) against CNG Vehicle Price ($).
From Table 6, cumulative NCR becomes zero between the 4th and 5th year. From Fig. 3 below, the point at which the cumulative NCR becomes zero can be read as 4.24 yrs.
Profit per dollar invested From Eq. (21), P/$ is estimated as follows: P/$ on the CNG project = ($25 MM) / ($15.44 MM + ($2.86 MM
∗
7)) = 0.72.
Internal rate of return (IRR) Table 7 is a table of the net present values for the project which was used in generating a plot of NPV against discount rate as shown in Fig. 4 for the determination of the IRR which is 14.42%. This value is the discount rate at which the NPV equals zero.
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Fig. 7. Plot of NPV ($MM) against CNG Station Price ($). Table 7 NPV at various discount rates. Discount rate (%)
NPV ($MM)
5 10 15 20 25 30 35 40
5.619599 2.278244 −0.29887 −2.32209 −3.93625 −5.24311 −6.31541 −7.20607
Table 8 Result of economics of the project. Parameter
Value ($)
Annual operating cost Total capital cost Gross Revenue at 1st Year Net Revenue at 1st Year Pay-out NPV @ 10% after 7 years Profit per Dollar invested IRR
$2.86 million $15.44 million $6.5 million $3.64 million 4.24 years $2.27 million 0.72 14.42%
Sensitivity analyses The effects of prices of natural gas, CNG vehicle and CNG station on the CNG Project are as shown below. The plot of NPV ($MM) against Natural Gas Price ($/scf) is shown in Fig. 5. That of NPV ($MM) against CNG Vehicle Price ($) is shown in Fig. 6, and Fig. 7 is the chart of NPV ($MM) against CNG station Price ($). From Figs. 5, 6 and 7 respectively, if natural gas price goes higher than $0.0068/scf, or price of CNG Vehicle goes higher than $32,700, or price of CNG station goes higher than $1.356 million, with other parameters being constant, then the NPV becomes negative and so it would not be advisable to invest in the CNG project. The summary of the results of the economic analysis of the project is as shown in Table 8. Conclusions Analyses on the introduction of CNG vehicles as means of public transportation in Nigeria using Port Harcourt – Onitsha expressway as case were conducted in this work. From the analyses conducted, the following conclusions can be drawn: • CNG vehicles are very suitable as alternative to diesel/petrol powered vehicles.
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• Proper analyses are needed to ensure that the dispensing capacity of the CNG refuelling stations sited would be enough to take care of the total GGE requirement of the CNG vehicles. • Compressor duty analyses are very much required to be able to recommend the energy required by the compressor stations to boost pressure to desired pressures at the pipelines and also to compress the natural gas at the CNG stations to CNG. • The project would incur very high investment cost of $15.44 million which is mainly resultant from the high cost of purchasing CNG vehicles and installing CNG stations. • In spite of the high investment costs of the project, the project is still economically viable since it has very high net present value of $2.27 million, good IRR of 14.42% and P/$ of 0.72 which are all strong indicators of an economically viable project. • It would take just less than five years to break even since it has a short pay-out of 4.24years. • The prices of natural gas, CNG vehicles and CNG refueling stations have very strong effect on the economic viability of the project, as seen from the sensitivity analyses. Recommendations At the moment, there is no policy that encourages the spread of the use of CNG vehicles in Nigeria. All of the government sponsored vehicles being used in the public transportation sector are diesel and gasoline powered vehicles. Considering that adopting CNG vehicles for public transportation through major routes in Nigeria would go a long way to ease transportation and reduce the pressure on gasoline and diesel which mostly result in fuel scarcity problems in the country, and also the fact that the introduction of CNG vehicles into the public transportation of the country is both technically feasible and economically viable according to this work, the federal and state governments can venture into bringing in CNG transport buses and injecting them into Nigeria’s public transportation. This can be taken into consideration in the financial allocation for the Ministry of Transportation in the next budget. The Nigerian government can also create a good avenue that would encourage the use of CNG vehicles, by establishing policy for subsidizing the importation of CNG vehicles to augment the high cost of CNG vehicles and encourage many private individuals to invest in the business. Declaration of Competing Interest None. Acknowledgments There is no other person that deserves all the thanks except Jesus, whose grace made it possible for us to bring this work to fruition. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. References [1] A. Norman, J.D. Corinchock, Diesel Technology, 7th Edition, The Goodheart-Wilcox Company, Inc., 2007 2007, ISBN-13: 978-1-59070-770-8. [2] J.E. Duffy, Modern Automotive Technology, 7th Edition, The Goodheart-Willcox Company, Inc., 2009 2009, ISBN 978-1-59070-956-6. [3] J.I. Anetor, High blood lead levels in the general Nigerian population: causes and implications, A Paper Presented at the National Conference on Phasing out Leaded Gasoline in Nigeria, November, 15-16, 2001, Abuja, Nigeria, 2001. [4] J.J. Enemari, Vehicular emission, environmental and health implications, A Paper presented at the National Conference of Phase-out of Leaded Gasoline in Nigeria, November 15 – 16, 2001, Abuja, Nigeria, 2001. [5] S.O. Kupolokun, Keynote Address. Presented at the National Conference on Phase-out of Leaded Gasoline in Nigeria, November 15-16, 2001, Abuja, Nigeria, 2001. [6] A.I. Uwagboe, Environment concerns of nigerian oil fuel combustion: a lesson from automobile gas emission, Society of Petroleum Engineers (SPE), Nigeria Annual International Conference and Exhibition (NAICE), 2001 6 – 8 August 2001, SPE-73145. [7] S. Tambari, I. Benjamin, D. Daso, K. Sorbari, A. John, Evaluation of comparative analysis in the use of petrol and compressed natural gas (CNG) as vehicular fuel, IOSR J. Mech. Civil Eng. (IOSR-JMCE), e-ISSN: 2278-1684, p-ISSN: 2320-334X, Volumne II, Issue 4 Ver. VI, July-August (2014) pp 46–54. [8] World Health Organization, 15-18 Million children suffer permanent brain damage from lead poisoning, 2004 Retrieved www.epha.org December 11, 2017. [9] N. Eromosele, Accounting for petroleum and petrochemical operations, Napter Q. Mag. NNPC, Vol XXVI, No. 1, First Quarter (1995) 5–7. [10] J.E. Gaius-Obaseki, CNG as an alternative fuel for Nigeria, A Lead Paper Presented at NAICE of SPE, August 6-8, 2001, Abuja, Nigeria, 2001. [11] A.H. Kafood, CNG application in qatar, International Petroleum Technology Conference, 2014 January 19, 2014, doi:10.2523/IPTC- 17497- MS. [12] NGVC (2016). Facts about natural gas vehicles. Retrieved www.ngvc.org, July 17, 2016. [13] International Association for Natural Gas Vehicles, Natural gas vehicle statistics: NGV count - ranked numerically as at December 2009, International Association for Natural Gas Vehicles, 2010 Retrieved www.iangv.org April 27, 2010. [14] Z. Wang, J. Lv, L. Rao, Y. Yang, H. Gao, Natural gas vehicles will develop greatly in china, International Petroleum Technology Conference, 2013 March 26, 2013, Beijing China. doi:10.2523/IPTC- 16705- MS. [15] Gas South, Compressed Natural Gas, 2016 Retrieved March 31, 2016. [16] W.J.M. Martens, Climate change, thermal stress and mortality changes, Soc. Sci. Med. 46 (3) (1998) 331–344. [17] European Commission, in: White Paper: European Transport Policy for 2010: Time to Decide, 2001, COM, 2001, p. 370. [18] A.J. Carlisle, N.C.C. Sharp, Exercise and outdoor ambient air pollution, Br. J. Sports Med. 35 (2001) 214–222. [19] A. Pilkington, F. Hurley, P. Donnan, Health Effects in ExternE Transport: Assessment and Expore-Response Functions, Institute of Occupational Medicine, Edingburgh, 1997 July 1997.
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[20] M. Goedkoop, R. Spriensma, The eco-indicator 99, a damage oriented method for life cycle impact assessment, Methodology Report, 2001 22 June 2001, 3rd Edition. Website: www.pre.nl. [21] J. Timmermans, J. Matheys, J. Mierlo van, P. Lataire, Environmental rating of vehicles with different fuels and drive trains: a univocal and applicable methodology, EJTIR 6 (4) (2006) 313–334 (2006). [22] E.I. Igweonu, I.U. Mbabuike, Utilization of compressed natural gas in Nigeria: a case for natural gas vehicles, Cont. J. Renewal Energy 2 (2) (2011) 1–9 2011 ISSN: 2251-0494. [23] B. Guo, A. Ghalambor, Natural Gas Engineering Handbook, Gulf Publishing Company, Houston, Texas, United States of America, 2005. [24] Oilserve Nigeria Limited, Ongoing Power Plant Stations and Pipeline Projects Listing, Port-Harcourt, Nigeria, 2004. [25] United States Department of Energy, Energy efficiency and renewable energy, Alternative Fuels Data Centre: Natural Gas Basics, 2016 Retrieved http: //www.afdc.energy.gov/fuel/natural_gas_basics.html December 1, 2016. [26] C.S. Rapu, A.O. Adenuga, W.J. Kanya, M.O. Abeng, P.D. Golit, Hilili, et al., Analysis of Energy Market Conditions in Nigeria, Central Bank of Nigeria (CBN), 2015 Occasional Paper No. 55, October 2015. [27] M. Smith, J. Gonzales, Costs associated with compressed natural gas vehicle fueling infrastructure, Energy Efficiency and Renewable Energy, US Department of Energy, 2014 September 2014. [28] S. Cornot-Gandolphe, O. Appert, R. Dickel, M. Chabrelie, A. Rojey, The challenges of further cost reductions for new supply options (Pipeline, LNG, GTL), 22nd World Gas Conference, 2003 June 1-5, 2003, Tokyo, Japan. [29] Consumer Reports (2014). The natural gas alternative, the pros and cons of buying a CNG-powered car. Retrieved www.consumerreports.org, April 2014. [30] C.I.C. Anyadiegwu, E.E. Anyanwu, B. Obah, Economic viability of underground natural gas storage in depleted oil reservoirs in Nigeria, Arch. Appl. Sci. Res., Sch. Res. Library 4 (4) (2012) 1880–1893 USA. [31] C. Muonagor, An appraisal of the economic viability of producing synthetic diesel from natural gas in Nigeria, Pet. Coal 55 (4) (2013) 338–350 www. vurup.sk/petroleum-coal.
Contents lists available at ScienceDirect
Scientific African journal homepage: www.elsevier.com/locate/sciaf
Technical and economic evaluation of the use of CNG as potential public transport fuel in Nigeria Anthony Igbojionu a, Charley Anyadiegwu a, Emmanuel Anyanwu b, Boniface Obah a, Chukwuemeka Muonagor a,∗ a b
Petroleum Engineering Department, Federal University of Technology, Owerri, Nigeria Mechanical Engineering Department, Federal University of Technology, Owerri, Nigeria
a r t i c l e
i n f o
Article history: Received 21 March 2019 Revised 9 October 2019 Accepted 24 October 2019 Available online xxx Editor: Dr. B. Gyampoh Keywords: Compressed natural gas Economic analysis Vehicles Stations Net present value Transportation
a b s t r a c t The need to develop alternative automobile fuel other than petrol and diesel in Nigeria is based on the rising cost, environmental pollution, and perennial scarcity of petrol, diesel, etc. Technical analysis of the introduction of compressed natural gas vehicles as a means of public transportation in Nigeria is conducted in this work. Port Harcourt – Onitsha expressway, a major interstate route in Nigeria is used as a case for analysis. 400 compressed natural gas vehicles are estimated to ply the route daily, which makes the total energy requirement per day to be 3856 gasoline gallon equivalent/day. It is recommended from the refueling stations design that five refueling stations with an average dispensing rate of 800 gasoline gallon equivalent/day are installed along the route to take care of the total requirement of 3856 gasoline gallon equivalent/day. Compressor duty analyses are conducted using Hysys, a process simulation software to determine the energy required by the compressors to boost the pressure of the gas from 14.70 psia at the sales point to 3600 psia which is the outlet pressure of the stations. From the analyses using economic indicators, the project is also found to be economically viable. It has a very high net present value of $2.27 million, short pay-out of 4.24 years, internal rate of return of 14.42% and profit per dollar investment after seven years of 0.72. The entire results indicate that adopting compressed natural gas vehicles for public transportation in at least the major interstate routes in Nigeria, will help to reduce the transportation problems encountered in Nigeria due to the pressure on gasoline and diesel. © 2019 Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative. This is an open access article under the CC BY-NC-ND license. (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Introduction Problems of gasoline and diesel combustion emissions “Gasoline and diesel are complicated mixtures of hydrocarbons, including aromatic, naphtenic, olefinic and paraffinic components” [1]. Gasoline typically contains hydrocarbons with 5–12 carbon atoms; while diesel fuel 12–18 carbon atoms. “Normal combustion of petroleum products takes only about 3/10 0 0 of a second” [2]. ∗
Corresponding author. E-mail address: [email protected] (C. Muonagor).
https://doi.org/10.1016/j.sciaf.2019.e00212 2468-2276/© 2019 Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative. This is an open access article under the CC BY-NC-ND license. (http://creativecommons.org/licenses/by-nc-nd/4.0/)
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Anetor [3] carried out experiment on general causes and implementation of high blood lead (Pb) levels in Nigerian population and found out that “depending on the formation composition, lead could be present in gasoline derived from the earth’s crust”. “This is usually small and in most cases insignificant. Lead (Pb) is a highly toxic chemical with no physiological benefits. There are several pathways by which lead is ingested by the population. But the major pathway is airborne lead, which is mostly produced by vehicles using leaded petrol” [4]. According to Enemari [4] “the combustion of petrol is inefficient in most cases and gases and particulate are emitted as exhaust gas/particulate. One of the perturbing ones is lead particulate, which has detrimental physiological effects. In countries such as Nigeria where gasoline that contains high lead levels is still used, atmospheric lead pollution from vehicular exhaust aerosols is a major source of lead pollution”. His-study revealed “disturbing blood lead levels (BLLs) in the general population”. Enemari [4] concluded that “scientific and medical evidence accumulated during the past several decades suggest that environmental lead pollution from highly leaded gasoline sold in Nigeria has elicited adverse health outcomes particularly in children”. He averred that “ingestion of lead has been linked to several physiological disorders in man such as interference with IQ of children of school age, gastrointestinal disorder, nausea, circulatory collapse, fatigue, blindness, CNS disorder, anaemia, etc. The use of leaded petrol therefore, needs to be reviewed in Nigeria like in other countries of the world to reduce the health effects. It is possible to produce petrol of high and desirable octane number without the use of TEL lead using appropriate technology e.g. cracking of higher molecular crude, use of methyl tetra–butyl ether (MBTE), Fluid Catalytic Cracker (FCC), and so on. In Nigeria, the two refineries in Port Harcourt have been modified to produce only unleaded petrol if the FCC is functioning properly”. According to Kupolokun [5], “Nigeria’s two refineries in Kaduna and Warri already have the capability to produce unleaded petrol, but would need modifications to be able to produce 100% unleaded gasoline”. “The defunct Federal Environmental Protection Agency (FEPA) undertook a study of levels of lead in six Nigerian cities of Lagos, Port Harcourt, Aba, Abuja, Ibadan and Kaduna. The soil samples were taken from roadside, motor parks, markets, etc. The lead content was, as staggering as it was frightening” [6]. Tests carried out by Uwagboe [6] using Atomic Absorption Spectrometry showed that “the concentration level of lead (in μg/g) around Warri collaborated this earlier result by the then FEPA. It illustrated that lead levels showed positive gradient with traffic density variations - especially along Effurun–Sapele road, classified as a high-density traffic road”. Removing lead does not remove vehicular emission as hydrocarbon, oxides of nitrogen and sulphur will still be emitted. There is need to do something about these too since they also represent environmental problems aiding photochemical reaction. Tambari et al. [7] found out that “the un-burnt gasoline, carbon monoxide, leaded compounds from leaded gasoline and other gases which pollute the air are deadly and harmful to humans, animals and food crops. Lead poisoning causes retarded mental and physical development, reduced attention spaces, increased blood pressures, hypertension, higher risk of cardiovascular diseases and premature deaths”. “The World Health Organization (WHO) estimates 15–18 million children in developing countries suffer from permanent brain damage due to lead poisoning” [8]. Need for CNG use as transport fuel in Nigeria For a developing country like Nigeria, creating a natural gas market is not an easy undertaking. Investments in gas projects are inherently capital intensive, requiring large increments for each expansion. The necessary conditions to overcome this initial hurdle are based on economic and investment policy choices used to exploit it rather than on the size of gas reserves. This largely explains the truism implicit in the fact that Nigeria’s natural gas reserves place her 9th in the world, yet she is not among the top 20 gas producers in the world! It is therefore, the methodology of gas market development that is crucial to creating economic viability and sustainability for a developing country, particularly those richly endowed with hydrocarbon reserves like Nigeria. The path toward a sustainable economy is therefore, deeply entwined in harnessing these resources, attracting the needed financial capital as well as nurturing productive utilization. According to Eromosele [9], “for many decades, Nigeria’s economy has been largely mono-cultural, depending essentially on crude oil, that murky substance which Eromosele [9] described as ‘a useless mixture of useful products’. The volatile nature of the global crude oil prices makes Nigeria’s economy very susceptible to the characteristic vagaries of the international oil market as well as to the dreaded Dutch disease syndrome (DDS). In Nigeria there is incessant scarcity and high cost of energy from existing gasoline and diesel. There are grave environmental issues associated with petroleum fuels. There is thus, the urgent need to find alternative energy to supplement gasoline and diesel as transportation fuel for automobiles in Nigeria”. “CNG has been acclaimed as a clean-burning, environmentally friendly and cheap fuel and its use to power vehicles is globally gaining momentum by the day. Therefore, the perennial problems of fuel scarcity and tailpiece pollution in Nigeria will be effectively tackled by utilizing CNG” [10]. Gaius-Obaseki [10] observed that “given the abundance of gas in Nigeria, the utilization of Compressed Natural Gas (CNG) as automobile fuel provides a clean and environmentally feasible alternative to conventional fuels”. He noted “that the world over, the transport industry is the single biggest consumer of oil, even as it has been fingered as a major source of total CO2 emissions are from road transport”. Review of literatures Review of literatures on worldwide use of CNG automotive engines According to Kafood [11], “natural gas has been considered as the most promising alternative fuel for its cleanliness and abundance. In recent times, natural gas has found applications in a range of industries including the transportation industry
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Table 1 Environmental impacts of use of diesel/gasoline vehicles in Nigeria. Environmental impact
Description
Impacts on human lives
Global warming potential
“Global warming contributes to the rise of the sea level, to an increased occurrence of extreme weather conditions. It leads to shifts and extinctions of biotopes and to drinking water shortage” [16]. “CO2 is the largest contributor to global warming and is mainly originating from the combustion of fossil fuels used for human activities. Nitrous oxide and methane, both emissions exhausted by road vehicles, are also contributing to climate change” [17]. “Carbon monoxide causes oxygen shortage and can lead to suffocation. The concentration of CO in the atmosphere can vary strongly and depends mainly on the traffic situation and on the wind” [18]
“Possible effects on human health are among others: increased occurrence of respiratory effects and cardiovascular diseases due to heat waves and increased number of infections and diseases due to floods” [16].
Air quality contamination and human toxicity
“CO concentrations in the blood of people living in the city can be twice as high as concentrations in the blood of people living in the countryside. The concentration of CO can reach very high levels in closed spaces like underground parking lots, or inside vehicles” [18]. “NOx form acids, when absorbed in the mucous “Nitrogen oxides (NOx) form a group of important membranes of the nose or the oral cavity, and cause pollutants mainly produced by road transportation” [19]. irritation of the bronchial tubes, coughing, and in higher “Nitrogen oxides also lead to eutrophication of soil, concentrations also lack of breath and even death” [19]. ground- and surface water and as a result leads to “People suffering from asthma can be very sensitive to negative impacts on aquatic and terrestrial ecosystems, NOx” [21]. surface water and agricultural and forestry yields” [20]. “Particulate matter (PM10) can remain in suspension in the “As PM10 particles are very small, they can penetrate very air for hours or even days” [19]. deep into the lungs. Because PM10 is often bound to other harmful substances, exposure and inhalation can lead to an important number of health problems and even to death” [19]. “Sulphur oxides (SOx) cause acidification which in turn “Sulphur oxides (SOx) are very soluble in water and damages aquatic and terrestrial ecosystems, surface consequently can easily be absorbed through the mucous water, agricultural and forestry yields and buildings” [20]. membrane of our bronchial tubes. People suffering from asthma are especially sensitive to SOx” [20]. “Volatile organic compounds (VOC) is the name regrouping “Some of the VOC present some important health damaging effects such as carcinogenicity” [21]. a large number of chemical compounds, like toluene, xylene, benzene, etc. Some of the previously described emissions also have indirect effects as they lead to other chemical reactions, once emitted into our atmosphere. The formation of tropospheric ozone for instance is triggered by sunlight and is an important secondary pollution of nitrogen oxides and hydrocarbons emissions (photochemical pollution). Ozone is toxic for living organisms and human beings and causes damage to the cells of the bronchial tubes” [21].
where they have been replacing diesel, gasoline and other fuels. Majorly as a result of the relatively low costs of CNG and the ever-spreading awareness campaigns on air pollution, a lot of motors today run on CNG and the amount of vehicles being fuelled with CNG continue to increase by the day”. “As at 2011, there existed over 14 million vehicles running on natural gas in the world. Iran was the country with the most number of natural gas vehicles (NGVs) with about 2.86 million NGVs. Pakistan followed closely with about 2.85 million NGVs, Argentina stood at the third spot with a little over 2 million cars running on natural gas, followed by Brazil with about 1.7 million NGVs and then India farther away with 1.1 million NGVs” [12]. “The Asia-Pacific region leads with 5.7 million NGVs, followed by Latin America with almost four million vehicles” [13]. “Due to high oil prices, gas has been considered lately as a good substitute for transportation fuel. In China for instance, the number of cars that run on natural gas is about 1 million. In short-haul fleets in the urban areas, the use of CNG is rapidly increasing while LNG is majorly used for long distance vehicles which represent most of truck diesel demand” [14]. “Several manufacturers sell bi-fuel cars. It is now much easier to convert gasoline vehicles to dual-fuel vehicles ie gasoline/CNG vehicles. A lot of auto-engineering workshops now do the retrofitting. Installing CNG conversion kits can be very costly, the cost of installing one can reach over $80 0 0 on average vehicles. However, CNG costs about 50% less than gasoline and emits up to 90% fewer emissions than gasoline” [15].
Evaluation of environmental effects of the use of diesel/gasoline vehicles in Nigeria The evaluation of the environmental effects of the use of diesel and petrol vehicles in Nigeria is presented in Table 1.
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Methodology Development of natural gas as transportation fuel in Nigeria Natural gas is transformed to automotive transportation fuel using compression equipment. The procedure employed in this work for the development of natural gas as transportation fuel in Nigeria comprises: 1. Estimation of the total number of vehicles that ply identified route on a daily basis which provides the information on the quantity of CNG fuel utilized for the day. 2. Determination of the gasoline gallon equivalent (GGE) requirement of the CNG vehicles to enable the quantity of CNG utilization to be known. 3. Design of pipeline network and refueling stations to be installed. 4. Laying of natural gas pipelines from gas supply (gas gathering) plants to the sites where the CNG refueling stations would be sited. The route used as case for the project is Port Harcourt to Onitsha Expressway. CNG refueling stations would have to be installed along the expressway while gas pipelines are laid across to transport gas to the CNG refueling stations where it would be compressed and stored for refueling the CNG vehicles that would ply the route. Estimation of total GGE per day In the course of this work, emphasis are on commercial vehicles. Most of the commercial vehicles that ply the Port Harcourt - Owerri - Onitsha route have an average vehicle-passenger capacity of 14 passengers. The number of vehicles that ply the Port Harcourt - Onitsha route to and fro is estimated; and this estimate enables us to determine the total GGE requirement for the day. This is achieved by taking an estimate of the number of individual commuters from Port Harcourt to Onitsha and from Onitsha to Port Harcourt daily, and analyzing this with the average passenger capacity of the vehicles. The number of similar vehicle models plying the route from Port Harcourt - Onitsha daily can be estimated as follows:
NV = NPT /VPC
(1)
Where, NPT = Total number of passengers (commuters), VPC = Vehicle passenger capacity. The fuel tank of the light duty CNG vehicle used for this analysis holds 8.0 gasoline gallon equivalent (GGE) of CNG at 3600 psi, and can cover an average of 200 miles (322 km) with a full CNG tank; which translates to 0.0248 GGE per km. According to Igweonu and Mbabuike [22], “one GGE equals 0.77Scf of CNG at 3600 psi and 126Scf of natural gas at standard temperature and pressure”. The GGE requirement for light-duty vehicles (LGGE ) is estimated as:
LGGE = LGGEk ∗ NV ∗ 2Lp
(2)
Where, LGGEk = GGE requirement for light duty vehicle per km, Lp = Distance from Port Harcourt to Onitsha. Since one GGE equals 0.77Scf of CNG at 3600 psi, the CNG requirement in scf is estimated as:
CNGLVol = LGGE ∗ 0.77
(3)
The GGE requirement for heavy duty vehicles (HGGE ) is also determined as:
HGGE = HGGEk ∗ NV ∗ 2Lp
(4)
Where, HGGEk = GGE requirement for heavy duty vehicle per km. The CNG requirement in scf is estimated as:
CNGHVol = HGGE ∗ 0.77
(5)
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Design of pipeline network The gas used as CNG was obtained from a gas treatment plant located at a field in the Niger Delta region of Nigeria. This particular gas processing plant is chosen because of its closeness to the route. The plant is 10 km (6.21miles) from Port Harcourt. Before transportation, the gas is compressed to the required pipeline inlet pressure, P1 by the user. The distance between the treatment plant and the route, added to the distance from Port Harcourt - Onitsha, gave a total distance to 126.68 miles. The average temperature of the gas in the pipeline gotten from simulation using HYSYS is 179.9°F. The hourly flow rate of the gas is the total volume of gas per hour needed by the CNG stations for the CNG vehicles. This is expressed as:
Q = CNGLVol ∗ 126/(0.77 ∗ 24 )
(6)
This flow rate is expressed in scf/hr as shown in the pipeline dimensions and gas properties represented in Table 3 below. Weymouth equation was used in this work for the estimation of pipeline inlet pressure and selection of pipe dimensions. The single pipeline arrangement which is adopted in this work is the most conventional pipeline arrangement because it makes use of only one straight pipe of same diameter from the beginning to the end. It is also the cheapest pipeline arrangement. The initial pressure, P1 is estimated using Weymouth equation for single pipeline arrangement as [23]:
P1 = (Q ∗ Pb /18.062Tb )2 ∗ SG ∗ Z ∗ Tavg ∗ L/D16/3 + P2 2
0 . 5
(7)
Where Q = flow rate, scf/hr Pb = base pressure, psia Tb = base temperature, 0 R SG = gas specific gravity Z = gas compressibility factor Tavg = gas average temperature, 0 R L = pipe length, miles D = pipe diameter, inch P2 = pipeline outlet pressure or minimum station inlet gas pressure, psia The number of pipes (Np ) to be laid to cover the entire distance is estimated as:
Np = 5280 ∗ L/Lp
(8)
Where Lp = length per pipe, ft Compressor selection using HYSYS HYSYS is applied in the selection of the compressor to compress the gas to the required initial pressure, P1 before it enters the pipeline for transmission and the selection of compressor to compress the gas at the outlet of the pipe, P2 (which is the same as the inlet pressure of the CNG station) to the refueling station outlet pressure, P3 which is set at 3600 psi. Number of refueling stations The number of CNG refueling stations (NCS ) to be installed is determined as:
NCS = LGGE /Rmax
(9)
Where Rmax = maximum dispensing rate of CNG refueling station Economic appraisal of the CNG transportation project The essence of conducting the economic appraisal is to determine whether the project is economically viable to be invested in or not. Costs and revenue analyses Introducing CNG fuel as alternative transportation would be capital intensive. A lot of things add up to the total expenditure required to bring CNG vehicles to service. They include: i. Costs of Pipeline and Compressor Station (CPC): These include the cost of laying the pipeline from the sales point to the locations of the CNG refueling stations and the cost of the compressor that would be installed at the initial point of the pipeline.
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Compressor station: A reciprocating compressor of less than 10 0 0 hp for which daily input / output is up to 500 MScf/day is chosen. Pipelines and metering stations: “Pipe segments with average length of 20 miles and diameters of 12 in., 14 in. or 18 in. that can cover the length of about 120 miles are commonly used, and metering stations are installed. Different pipes of lengths up to 40 ft make up the various pipe segments” [24]. Costs of pipelines and compressor station can be estimated as:
CPC = CPC per km ∗ L
(10)
Where CPC per km = costs of pipeline and compressor station per km ii. Cost of CNG Refuelling Stations (CCR ): This includes the cost of purchasing and installing the CNG refuelling stations with their associated compressor stations along Port Harcourt-Onitsha Expressway. The number and storage capacity of the CNG refuelling stations depend on the number of vehicles that ply the route in a given time. Cost of CNG refuelling stations can be estimated as:
CCR = CCR per station ∗ NCS
(11)
iii. Cost of CNG Vehicles (CCV ): This is the total cost of the CNG vehicles that would be purchased and shipped down to Nigeria which would be plying Port Harcourt-Onitsha Expressway. It is assumed that the vehicles would be purchased on a one-time basis and they would have life span of seven (7) years each before they are discarded as scrap. Cost of CNG vehicles can be estimated as:
CCV = CCV per vehicle ∗ NV
(12)
The total Capital Cost, CAPEX is given by:
TCC = CPC + CCR + CCV
(13)
Annual Operating cost, OPEX is given by:
AOC = GAC + RFML + MPC + VDAC
(14)
Where, GAC = Annual Cost of Gas RFML = Fuel, Maintenance and Labour Costs for CNG Refueling Stations MPC = Maintenance Costs for Pipelines and Compressors VDAC = CNG Vehicles Drivers and Assistant Drivers’ Wages and Car Maintenance Costs According to United States Department of Energy [25], “one GGE equals 126 Scf of natural gas at pressure of 30psia”. “The price of natural gas is $4/MScf” [26]. Annual cost of gas is estimated as:
ACG = LGGE ∗ 126 ∗ Gp ∗ 353
(15)
Where Gp = Price of natural gas $0.004/scf 353 = Number of plying days of the vehicles considering 12 days of routine maintenance of the vehicles per year. “Fuel, maintenance and labour costs for CNG refueling stations (RFML ) are estimated as 13% of the costs of CNG refueling stations” as [27]:
RFML = 0.13 ∗ CCR
(16)
According to Cornot-Gandolphe et al. [28], “maintenance costs for pipelines and compressors are estimated as 20% of the costs of pipelines and compressor stations per km” as shown:
MPC = 0.2 ∗ CPC
(17)
According to Consumer Reports [29] “CNG vehicle drivers and assistant drivers’ wages and car maintenance costs are determined as 24% of gross revenue” as:
VDAC = 0.24 ∗ GR
(18)
Gross Revenue, GR = Vfreq ∗ NV ∗ VPC ∗ TF ∗ 353
(19)
Where, Vfreq = Frequency of Transportation per day per Vehicle NV = Total Number of Vehicles VPC = Total Number of Passengers per Vehicle TF = Transport Fare of each Passenger 353 = Number of plying days of the vehicles considering 12 days of routine maintenance of the vehicles per year. Net revenue for subsequent years of operation,
NR = GR − OPEX
(20)
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Table 2 CNG vehicles parameters. Number of vehicles (P/H to Onitsha) Number of Vehicles (Onitsha to P/H) Total GGE Requirement Total scf of CNG Requirement
400 400 3856 GGE 2970 scf
Table 3 Pipeline and gas parameters for transportation. Flow rate, Scf/hr Base pressure, psia Base temperature, 0 R Gas specific gravity Gas Z-factor Average temperature, 0 R Pipeline length to station, miles Diameter of pipeline, in Min Station inlet gas pressure
20,239 14.7 520 0.69 0.92 639.9 126.68 12 30 psia
Economic indicators Net present value (NPV) “Net Present Value (NPV) is a measure of profitability of any project. A project is generally welcomed if the NPV is positive and rejected if the NPV is negative because the project will also have negative cash flows” [30]. The NPV is the sum of the present values of the project at the different years. Pay-out (PO) “The Pay-out (PO) for a project refers to the time (in years) at which the initial investment on the project is just recovered” [31]. It is the time at which cumulative NCR becomes zero. Profit per dollar invested In this work, the P/$ after 7years is the ratio of the total net cash recovery from the first (1st) to seventh (7th) year and the sum of CAPEX and OPEX as represented below:
P/$ = NC Rtotal /[(CAP EX + (OP EX ∗ 7 )]
(21)
Where NCRtotal = total net cash recovery of the project for the 7 years. Internal rate of return (IRR) The rate of return of a project at which the NPV of all cash recoveries amounts to zero is the internal rate of return (IRR) on investment for the project. The higher the IRR of a project, the more desirable it is to undertake such project. Presentation of results Estimation of total GGE per day The number of vehicles required would be estimated with Eq. (1) as: Number of vehicles, NV = 5500 / 14 = 392 vehicles The 392 vehicles are approximated to 400 vehicles. From Eq. (2), LGGE = 0.0248 ∗ 400 ∗ 2 ∗ 194 km = 3856 GGE From Eq. (3), CNGLvol = 3856 ∗ 0.77 = 2970 scf of CNG. The summary of the parameters of the CNG vehicles is shown in Table 2 below. Design of pipeline network and compressor stations Pipeline network for gas transportation The pipeline dimensions and gas properties are as shown in Table 3 below. From Eq. (7), for single pipeline network of 126.88 miles, the initial pressure given the CNG Station 5 gas inlet pressure as 30 psi is: P1 = [(20,238.75 ∗ 14.7/18.062 ∗ 520)2 ∗ 0.69 ∗ 0.92 ∗ 639.9 ∗ 126.88/1216/ 3 + 302 ]0. 5 = 31.47psia. Number of pipes (NP ) required for the entire pipe length is estimated from Eq. (8) to the nearest whole number as follows: NP = 5280
∗
126.88/40 = 16,749.
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Fig. 1. Compressor and Pipeline Design Flow sheet.
The compressor selection Using HYSYS, the compressor duty, which is the power consumption at a particular pressure is evaluated. The compressor selection involves determining the particular compressor duty required to boost the pressure of the gas from 14.70 psia which is its pressure from the separator to 32.62psia which is the pressure required at beginning of the pipeline. The compressor and pipeline flowsheet is redrawn using Microsoft Word and as shown in Fig. 1. The compressor selection is performed again to determine the maximum compressor duty required to boost the pressure of the gas from 30psia which is the lowest possible pressure of the gas from the pipeline to 3600 psia which is the outlet pressure of CNG fuel at the station. The compressor and pipeline flowsheet is redrawn using Microsoft Word and as shown in Fig. 2. CNG refueling stations selection The number of CNG refueling stations to be installed is estimated from Eq. (9) to the nearest whole number as: NCS = 3856 / 800 = 5. The five medium stations would be installed at km 1 (0.621mile), km 49 (30.43 miles), km 97 (60.23 miles), km 146 (90.67 miles) and km 194 (120.47 miles) respectively along the 194 km-expressway. The summary of the technical parameters of the CNG vehicles and the refueling stations is shown in Table 4 below: Results of the economic analyses Capital costs i. Costs of Pipelines and Compressor Station: Deduced from Cornot-Gandolphe et al. [28], the total cost of pipeline and compressor station is $700 per km.
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Fig. 2. Compressor Design Flow sheet for CNG Station.
From Eq. (10), total pipeline systems cost is estimated as: CPC = $700 per km ∗ 204 km = $142,800. ii. Cost of CNG Refueling Stations: According to Smith et al. [27], “a medium CNG refueling station with an average daily dispensing rate of 800 GGE/day which is the type of station recommended for this project costs $90 0,0 0 0 . From Eq. (11), the total cost of the CNG stations is estimated as: CCR = $90 0,0 0 0
∗
5 = $4.5 million.
iii. Cost of CNG Vehicles: The number of CNG vehicles that would be purchased is 400, “with CNG vehicles cost of $27,0 0 0 each” [29]. From Eq. (12), the total cost of the CNG vehicles is: CCV = $27,0 0 0 ∗ 40 0 = $10.8 million. From Eq. (13), total capital cost, TCC is: TCC = $142,800 + $4.5 million + $10.8 million = $15.44 million. Annual operating costs i. Annual Gas Cost: The total GGE requirement for the 400 cars that would ply to and fro Port Harcourt and Onitsha is 3856.
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A. Igbojionu, C. Anyadiegwu and E. Anyanwu et al. / Scientific African 6 (2019) e00212 Table 4 Summary of the technical parameters. Parameters
Value
Number of Vehicles (P/H to Onitsha) Number of Vehicles (Onitsha to P/H) Total GGE Requirement Total scf of CNG Requirement Flow Rate across the Pipeline Pipeline Inlet Gas Pressure Number of Pipes Number of CNG Stations Required Dispensing Rate per Station CNG Station Inlet Gas Pressure CNG Station Outlet Gas Pressure
400 400 3856 GGE 2970 scf 20,239 scf/hr 31.47 psia 16,749 5 800 GGE/day 30psi 3600 psi
Table 5 Summary of the cash flows for the CNG project. Time (yr)
CAPEX ($MM)
OPEX ($MM)
GROSS REV ($MM)
NCR ($MM)
CUM NCR ($MM)
PV @ 5% ($MM)
PV @ 10% ($MM)
0 1 2 3 4 5 6 7
15.44 0 0 0 0 0 0 0
0 2.86 2.86 2.86 2.86 2.86 2.86 2.86
0.0 6.50 6.50 6.50 6.50 6.50 6.50 6.50
−15.44 3.64 3.64 3.64 3.64 3.64 3.64 3.64
−15.44 −11.80 −8.16 −4.52 −0.88 2.76 6.40 10.04
−15.44 3.47 3.30 3.14 2.99 2.85 2.72 2.59
−15.44 3.31 3.01 2.73 2.49 2.26 2.05 1.87
Table 6 Cumulative NCR after 7 years. Time (yr)
NCR ($MM)
CUM NCR ($MM)
0 1 2 3 4 5 6 7
−15.44 3.64 3.64 3.64 3.64 3.64 3.64 3.64
−15.44 −11.80 −8.16 −4.52 −0.88 2.76 6.40 10.04
From Eq. (15), Annual gas cost, ACG is estimated as: ACG = 3856 ∗ 126 ∗ 353 ∗ 0.004 = $686,029. ii. Vehicles Fuels and Maintenance Costs and Drivers’ Allowances: The gross revenue is first determined according to Eq. (19) as: Gross Revenue, GR is: GR = 2 trips ∗ 400 vehicles ∗ 14 passengers ∗ N600 ∗ 353 days = N2.37 billion ie $6.5 million per year (at a rate of $1 = N365.00). From Eq. (18), Vehicles Fuels and Maintenance Costs and Drivers’ Allowances is determined as: VDAC = 0.24 ∗ $6.5 million = $1.56 million per year. iii. Pipeline Monitoring and Compressor Maintenance Cost is determined from Eq. (17) as: MPC = 0.2 ∗ $142,800 = $28,560. iv. Cost of CNG Refuelling Stations Maintenance and Fuel is determined from Eq. (16) as: RFML = 0.13 ∗ $4.5 million = $585,0 0 0. From Eq. (14), annual operating cost, AOC is given as: AOC = $686,029 + $1.56 million + $28,560 + $585,0 0 0 = $2.86 million. Revenues and cash flow analysis The gross revenue, GR is determined according to Eq. (19) as: GR = 2 trips ∗ 400 vehicles ∗ 14 passengers ∗ N600 ∗ 353 days = N2.37 billion ie $6.5 million per year (at a rate of $1 = N365.00). The net revenue is determined according to Eq. (20) as:
A. Igbojionu, C. Anyadiegwu and E. Anyanwu et al. / Scientific African 6 (2019) e00212
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Fig. 3. Plot of Time (Yrs) against Cum-NCR (Millions of Dollars).
Fig. 4. Plot of NPV against Discount rate.
Net Revenue = $6.5 million - $2.86 million = $3.64 million. The cash flows for the project for 7 years are shown in Table 5. Determination of the economic indicators Calculation of net present value From Table 5, the Net Present Value, NPV at an expected rate of return/discount rate of 10% which is the sum of all the Present Values in the last column at the left = $2.27 million. Pay-out (PO) Table 6 shows the cumulative NCR and NCR after 7 years while Fig. 3 represents the graph of time against cumulative NCR in millions of dollars for the gas injection project.
12
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Fig. 5. Plot of NPV ($MM) against Natural Gas Price ($/scf).
Fig. 6. Plot of NPV ($MM) against CNG Vehicle Price ($).
From Table 6, cumulative NCR becomes zero between the 4th and 5th year. From Fig. 3 below, the point at which the cumulative NCR becomes zero can be read as 4.24 yrs.
Profit per dollar invested From Eq. (21), P/$ is estimated as follows: P/$ on the CNG project = ($25 MM) / ($15.44 MM + ($2.86 MM
∗
7)) = 0.72.
Internal rate of return (IRR) Table 7 is a table of the net present values for the project which was used in generating a plot of NPV against discount rate as shown in Fig. 4 for the determination of the IRR which is 14.42%. This value is the discount rate at which the NPV equals zero.
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Fig. 7. Plot of NPV ($MM) against CNG Station Price ($). Table 7 NPV at various discount rates. Discount rate (%)
NPV ($MM)
5 10 15 20 25 30 35 40
5.619599 2.278244 −0.29887 −2.32209 −3.93625 −5.24311 −6.31541 −7.20607
Table 8 Result of economics of the project. Parameter
Value ($)
Annual operating cost Total capital cost Gross Revenue at 1st Year Net Revenue at 1st Year Pay-out NPV @ 10% after 7 years Profit per Dollar invested IRR
$2.86 million $15.44 million $6.5 million $3.64 million 4.24 years $2.27 million 0.72 14.42%
Sensitivity analyses The effects of prices of natural gas, CNG vehicle and CNG station on the CNG Project are as shown below. The plot of NPV ($MM) against Natural Gas Price ($/scf) is shown in Fig. 5. That of NPV ($MM) against CNG Vehicle Price ($) is shown in Fig. 6, and Fig. 7 is the chart of NPV ($MM) against CNG station Price ($). From Figs. 5, 6 and 7 respectively, if natural gas price goes higher than $0.0068/scf, or price of CNG Vehicle goes higher than $32,700, or price of CNG station goes higher than $1.356 million, with other parameters being constant, then the NPV becomes negative and so it would not be advisable to invest in the CNG project. The summary of the results of the economic analysis of the project is as shown in Table 8. Conclusions Analyses on the introduction of CNG vehicles as means of public transportation in Nigeria using Port Harcourt – Onitsha expressway as case were conducted in this work. From the analyses conducted, the following conclusions can be drawn: • CNG vehicles are very suitable as alternative to diesel/petrol powered vehicles.
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• Proper analyses are needed to ensure that the dispensing capacity of the CNG refuelling stations sited would be enough to take care of the total GGE requirement of the CNG vehicles. • Compressor duty analyses are very much required to be able to recommend the energy required by the compressor stations to boost pressure to desired pressures at the pipelines and also to compress the natural gas at the CNG stations to CNG. • The project would incur very high investment cost of $15.44 million which is mainly resultant from the high cost of purchasing CNG vehicles and installing CNG stations. • In spite of the high investment costs of the project, the project is still economically viable since it has very high net present value of $2.27 million, good IRR of 14.42% and P/$ of 0.72 which are all strong indicators of an economically viable project. • It would take just less than five years to break even since it has a short pay-out of 4.24years. • The prices of natural gas, CNG vehicles and CNG refueling stations have very strong effect on the economic viability of the project, as seen from the sensitivity analyses. Recommendations At the moment, there is no policy that encourages the spread of the use of CNG vehicles in Nigeria. All of the government sponsored vehicles being used in the public transportation sector are diesel and gasoline powered vehicles. Considering that adopting CNG vehicles for public transportation through major routes in Nigeria would go a long way to ease transportation and reduce the pressure on gasoline and diesel which mostly result in fuel scarcity problems in the country, and also the fact that the introduction of CNG vehicles into the public transportation of the country is both technically feasible and economically viable according to this work, the federal and state governments can venture into bringing in CNG transport buses and injecting them into Nigeria’s public transportation. This can be taken into consideration in the financial allocation for the Ministry of Transportation in the next budget. The Nigerian government can also create a good avenue that would encourage the use of CNG vehicles, by establishing policy for subsidizing the importation of CNG vehicles to augment the high cost of CNG vehicles and encourage many private individuals to invest in the business. Declaration of Competing Interest None. Acknowledgments There is no other person that deserves all the thanks except Jesus, whose grace made it possible for us to bring this work to fruition. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. References [1] A. Norman, J.D. Corinchock, Diesel Technology, 7th Edition, The Goodheart-Wilcox Company, Inc., 2007 2007, ISBN-13: 978-1-59070-770-8. [2] J.E. Duffy, Modern Automotive Technology, 7th Edition, The Goodheart-Willcox Company, Inc., 2009 2009, ISBN 978-1-59070-956-6. [3] J.I. 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