Emissions in the Transportation Sector of Senegal

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Article Dynamics of Greenhouse Gas (GHG) Emissions in the Transportation Sector of Senegal

Bertrand Tchanche

Department of Physics, Faculty of Applied Science, University Alioune Diop, P.O. Box 30, 21400 Bambey, Senegal; [email protected] or [email protected]; Tel.: +221-7-7423-6771

Abstract: The transportation sector of Senegal is dominated by the road subsector, which relies on fossil fuels: gasoline and diesel. Their combustion generates substances such as carbon dioxide, methane, nitrous oxide, and many others responsible for climate change, which has negative impacts on the environment, human health, and activities. This study is based on data collected from Senegal’s ofﬁcial reports on transport and energy, and Intergovernmental Panel on Climate Change (IPCC) greenhouse gases’ analysis methods. In the period 2000–2013, growing emissions were experienced, 6 reaching up to 2.38 × 10 tCO2-eq in 2013. The aging vehicle ﬂeet (~20 years old on average), made up of light-duty vehicles (around 85%), a fast-growing number of imported cars, and the predominance of diesel engines (around 59%) are the aggravating factors. Beyond climate change, other gaseous

substances resulting from the combustion of fuels such as carbon monoxide (CO), sulfur oxide (SO2), and particle matters (PMs) contribute to the deterioration of the outdoor air quality. Therefore, it is becoming urgent to monitor the evolution of these emissions and take appropriate measures to reduce their concentrations in the atmosphere. The Government of Senegal has taken a step forward through the modernization of transport infrastructure, and the creation of a center dedicated to the monitoring of outdoor air quality (Centre de Gestion de la Qualité de l’Air—CGQA) and a center in charge of the technical control of vehicles (Centre de Contrôle Technique des Véhicules Automobiles—CCTVA) in Dakar, but much remains to be done.

Keywords: greenhouse gas emission; fossil fuels; transportation sector; combustion; air quality

Citation: Tchanche, B. Dynamics of Greenhouse Gas (GHG) Emissions in the Transportation Sector of Senegal. 1. Introduction Earth 2021, 2, 1–15. https://dx.doi.org/ The transport sector is an important part of the economy, allowing the movement of 10.3390/earth2010001 goods and people over varying distances. Historically, people move for various reasons: search for food, need for trade, leaving for battle grounds, fleeing from a disaster, diplomacy, Received: 19 November 2020 tourism, and so forth. Over time and thanks to technological, cultural, and political changes, Accepted: 11 December 2020 the means of transport have been greatly modified, reaching today’s sophisticated state Published: 23 December 2020 with diverse means [1]. Therefore, mankind, who at a period of his history had only walking as means of transport, now has a range of choices: bicycle, motorcycle, automobile, Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims train, aircraft, boat, and so forth. Modes of transport are usually grouped in categories: in published maps and institutional animal-powered transport, air transport (aircraft, airship, balloon, hang glider, helicopter), affiliations. human-powered transport (cycling, walking), ship transport (boat, ship, submarine), rail transport (train, metro, tram), road transport (motorcycle, bus, car, truck, etc.), and others like lifts, escalators, and spaceships. Depending on its implementation and integration, the role of each mode is specific. Dostal and Adamec, for instance, studied the transport Copyright: © 2020 by the author. Li- sector of the Czech Republic and showed the specific role and advantages of each mode [2]. censee MDPI, Basel, Switzerland. This New developments are modifying significantly the transport systems in the 21st century. article is an open access article distributed Autonomous vehicles, drones, maglev trains, electric vehicles, and the hyperloop will under the terms and conditions of the change the transport of the present century. To be attractive, these means of transport Creative Commons Attribution (CC BY) must combine comfort, speed, robustness, and some luxury items, and require dedicated license (https://creativecommons.org/ infrastructure. licenses/by/4.0/).

Earth 2021, 2, 1–15. https://dx.doi.org/10.3390/earth2010001 https://www.mdpi.com/journal/earth Earth 2021, 2 Earth 2020, 1, FOR PEER REVIEW 2 of 16 2

these means of transport must combine comfort, speed, robustness, and some luxury items, and require dedicated infrastructure.The state of the transport infrastructure in Africa is linked to its recent history. Precolo- The statenial of the infrastructure transport infrastructure was modified toin serveAfrica the is interestslinked to of its colonial recentcompanies history. Precolonial (i.e., transfer infrastructure mineralwas modified and agricultural to serve the resources interests to of Europe). colonial Transportcompanies facilities (i.e., transfer were built,mineral rail and being agricultural resourcespredominant to Europe as it offers). Transport efficient facilities and massive were built, freight rail transport being predominant [3,4]. By 1960, as mostit offers coun- efficient and massivetries became freight independent, transport [3,4 and]. By first 1960, rulers most had countries the ambition became to independent, bring prosperity and tofirst their rulers had thepopulations. ambition to bring Most infrastructureprosperity to the in their populations. modern Senegal Most areinfrastructure colonial heritage. in the modern In order to Senegal are coloniallink various heritage. parts In oforder the countries,to link various roads parts were of built the andcountries, in some roads places were car built manufacturers and in some places carinstalled manufacturers assembly installed lines, like assembly in Senegal lines [5]., like Therefore, in Senegal African [5]. nations,Therefore, till African the 1970s, enjoyed a relative era of prosperity, but the structural adjustment plans and other factors nations, till the 1970s, enjoyed a relative era of prosperity, but the structural adjustment plans and like low commodity prices (raw materials) and the Franc CFA currency devaluation (in other factors like low commodity prices (raw materials) and the Franc CFA currency devaluation (in 1994) led to severe economic crises (in Figure1, the decline in the trade balance in Senegal 1994) led to severe economic crises (in Figure 1, the decline in the trade balance in Senegal from 1995), from 1995), preventing them from investing in the development of infrastructure. This preventing thempartly from explains investing why in the Africa development lags behind of infrastructure. in transport development This partly explains [6]. The why state Africa of the lags behind intransportation transport development sector was [6] exposed. The state in previous of the transportation work, in which sector it is shown was exposed that African in previous work,transport in which systems it is shown still that need African improvement transport [3, 7systems]. still need improvement [3,7].

Figure 1. Time variation of the trade balance of Senegal (1960-2018), source: ref. [8]. Figure 1. Time variation of the trade balance of Senegal (1960-2018), source: ref. [8]. Senegal, a country located in West Africa, shares borders with the Atlantic Ocean in Senegal, athe country west, Mauritanialocated in West to the Africa, north, shares Mali in borders the east, with Guinea-Conakry the Atlantic Ocean and Guinea in the Bissau west, in Mauritania to thethe south.north, SomeMali in of the the e country’sast, Guinea data-Conakry are given and here Guinea [9]: Bissau in the south. Some of the country’s data• areclimate: given hot here tropical [9]: • area: 196,722 km2  climate: hot tropical • population: ~16.5 million inhabitants  2 area: 196,722• kmpopulation growth rate: ~2.8%  population:• ~16.5GDP million (Gross inhabitants Domestic Product) per capita (PPA): ~US $3349  population• growthdivisions: rate: 14~2.8% regions  GDP (Gross• Domesticcapital city: Product) Dakar per capita (PPA): ~US$ 3349  divisions:• 14 regionsHDI (Human Development Index): 0.51(2017)  capital city: DakarThe transport sector in Senegal represents around 10% of the GDP and consumes  HDI (Human33% Development of the total energy Index) consumed: 0.51(2017) in the country [10]. As in most African nations in The transportsub-Sahara sector Africa,in Senegal this represents sector is based around on the10% utilization of the GDP of fossiland consumes fuels which 33% are of a the major source of greenhouse gases and atmospheric pollutants. These emissions have negative total energy consumed in the country [10]. As in most African nations in sub-Sahara Africa, this sector impacts on the climate and on the health quality. Studies have shown that the level of is based on the utilization of fossil fuels which are a major source of greenhouse gases and pollution in West Africa is vastly underestimated [11], and is constantly increasing with atmospheric pollutants.population These growth emissions and urbanization. have negative According impact tos the on NGO the climate Public Eye, and pollution on the health is partly quality. Studiesdue have to theshown quality that of the the level fuels of found pollution on the in West market Africa [12]. is They vastly are underestimated imported from Europe[11], and is constantlywhere increas stricting regulations with population do not growth allow theirand urbanization. use. Countries According in West Africato the NGO are inundated Public Eye, pollutionwith is partly poor-quality due to the fuels quality without of the any fuels control. found Veryon the little market effort [12] is. madeThey toare reach imported a strict from Europe whereregulation strict inregulations those countries do not whereallow the nationalir use. C agenciesountries dedicated in West Africa to quality are inundated control are

Earth 2020, 1, FOR PEER REVIEW 3 of 16

Earth 2021, 2with poor-quality fuels without any control. Very little effort is made to reach a strict regulation in 3 those countries where national agencies dedicated to quality control are weak or simply do not exist. These fuels, and more specifically the substances released in the atmosphere after their combustion, deteriorate the quality of the air and contribute to climate change with adverse consequences: weak or simply do not exist. These fuels, and more specifically the substances released frequent floods, seasonalin the irregularities, atmosphere after disappearance their combustion, of flora deteriorate and fauna, the and quality so forth of. the Despite air and the contribute critical situation observed,to climate very change little effort with is adverse being made consequences: to assess these frequent emissions floods, in seasonal sub-Saharan irregularities, countries, as regionsdisappearance are severely ofhit flora and and conflicts fauna, due and to so climate forth. Despite change the have critical become situation frequent observed,, very especially in rural areaslittle and effort Sahel is being regions made. Combined to assess thesewith emissionshigh rate of in unemployment, sub-Saharan countries, poverty as, regions corruption, and lack areof sustainable severely hit development and conflicts policy due, to climate climate change change is fueling have become terrorism frequent, in Mali, especially Somalia, Sudan, Niger,in rural Nigeria, areas Cameroon and Sahel, regions.and Burkina Combined Faso. withThe high present rate study of unemployment, assesses the poverty, dynamics of greenhousecorruption, gas emissions and lack of in sustainableSenegal. Thanks development to the policy, statistical climate data change collected is fueling, these terrorism emissions are evaluatedin Mali, and Somalia, analyzed. Sudan, The paper Niger, is Nigeria, divided Cameroon, into several and parts: Burkina first, Faso. the transport The present study sector will be presented,assesses then the the dynamics greenhouse of greenhouse gases recalled gas as emissions well as the in Senegal. factors that Thanks influence to the statisticaltheir data concentration. Then,collected, statistical these data emissions are analyzed are evaluated and the methodology and analyzed. for The calculating paper is divided emissions into several presented. Results areparts: finally first, pre thesented transport and discussed sector will before be presented, some conclusion then thes are greenhouse raised. gases recalled as well as the factors that influence their concentration. Then, statistical data are analyzed and the methodology for calculating emissions presented. Results are finally presented 2. Materials and Methods and discussed before some conclusions are raised.

2.1. Description of the 2.Transportation Materials and Sector Methods of Senegal The transport sector2.1. Description in Senegal of is the multimoda Transportationl, divided Sector ofinto Senegal four modes: roadways, seaways, airways, and railways. EachThe mode transport has specific sector inequipment Senegal is and multimodal, infrastructure divided. Transport into four modes modes: need roadways, to be integrated, the seaways,objective being airways, to ensure and railways. an easy move Each modeof people has and speciﬁc goods equipment within and and outside infrastructure. the country. Transport modes need to be integrated, the objective being to ensure an easy move of people and goods within and outside the country. 2.1.1. Roadways Transportation 2.1.1. Roadways Transportation Roadways submodesRoadways are grouped submodes into two are main grouped categories into, twodepending main categories, on whether depending an engineon is whether used or not. Walking,an whichengine involves is used or the not. use Walking, of muscular which energy, involves is very the use present of muscular for two energy, main is very reasons: the low purchasingpresent forpower two of main the reasons:populations the lowand purchasingthe lack of infrastructure. power of the populations If walking is and the the lack of means of choice in theinfrastructure. countryside, Ifit is walking clear that is the in cities means also of choicepopulations in the are countryside, forced to walk it is clear [13]. that In in cities urban areas, motor transportalso populations is expensiv aree forced for the to majority walk [13 of]. Inpopulations urban areas,. Bicycle motors transportare not popular, is expensive for being used by very fewthe majoritypeople, and of populations. do not benefit Bicycles from the are notexisting popular, infrastructure being used, which by very does few not people, and keep special lanes fordo cyclists not beneﬁt. Animal from carriages the existing are infrastructure,popular among which the underprivileged does not keep special layers lanes of the for cyclists. population [14]. In urbanAnimal areas, carriages it is used are popularto transport among people the underprivileged(as in Figure 2), layersgoods, of and the munic populationipal [14]. In waste. It is very usefulurban in rural areas, areas it is where used to it transport appears to people be the (as only in Figure means2 ),of goods, transport andation municipal of large waste. It is quantities of goods, andvery serves useful as in an rural ambulance areas where in some it appears cases. Horse to be the-drawn only transport means of transportationis an income- of large quantities of goods, and serves as an ambulance in some cases. Horse-drawn transport is generating activity for craftsmen and donkey/horse breeders. an income-generating activity for craftsmen and donkey/horse breeders.

FigureFigure 2. A 2. horse A horse carriage carriage in the in the city city of Thies of Thies (left (left)) and and a locally a locally assembled assembled car car, (right “ndiaga), “ndiaga ndiaye”. ndiaye”. For the motorcycle taxi, a rise in power has been witnessed in recent years, with For the motorcycle taxi, a rise in power has been witnessed in recent years, with more than more than 100,000 vehicles recorded, an ever-increasing number. At the beginning, it was 100,000 vehicles recorded,used byan unemployedever-increasing young number. people, At the and beginning, it is gradually it was spreadingused by unemployed to all those without lasting employment. The lack of regulation exposes motorcyclists to all kinds of risks, Earth 2021, 2 4

and particularly to accidents. They contribute to the economy by transporting people and goods, and also through the fuel they consume. Tricycles have recently made their appearance into the transport of goods, and are gradually supplanting carts. They are imported from China, and mounted locally. The automobile is a privileged means over long distances. Low purchasing power limits the development of individual transport and strengthens mass transport. Both inside and outside cities, there are buses, minibuses, taxis, and informal transport by very old vehicles operated without license (the so-called “clandos”), that carry people. Minibuses are of several types: Tata (assembled by the company SENBUS Industries), “car rapid”, and “ndiaga ndiaye” (see Figure2). The latter are made in makeshift workshops by craftsmen with often insufﬁcient technical skills. The government holds a public transport company, with two branches: “Senegal Dem Dikk” for intercity transport and “Dakar Dem Dikk” for urban transport in the capital city, Dakar. The vehicle ﬂeet has more than 600,000 vehicles (more than 70% being in the Dakar region). These automotive vehicles are generally imported from other continents, with a small proportion assembled locally as minibuses. The road network was approximately 16,496 km long in 2016, and its modernization continued with the completion of several projects, including the construction of the Dakar-Diamniadio and Ila Touba highways. However, the density of the road network remains low as in most sub-Saharan African countries, and the percentage of paved roads is less than 40%.

2.1.2. Airways Transportation Senegal has about ten airports; the most important is the Diamniadio airport inaugurated in 2018. Less important ones are Saint Louis, Cap Skiring, Ziguinchor, and Tambacounda. Records show that Senegal has had several airline companies in its history, but these often ﬁzzled out. Senegal currently has a national company, Air Senegal, launched in 2018, and a private company, Transair.

2.1.3. Seaways Transportation The country has four ports, the most important of which is in Dakar. Kaolack, Saint Louis, and Ziguinchor also hold port facilities. The country’s foreign trade takes place mainly through the port of Dakar, or 95% of trade. Maritime transport links Casamance to the capital, Dakar, and is critical for opening up this part of the country. On 26 September 2002, the “Joola”, the main ferry linking both parts of the country, sank one night due to poor meteorological conditions, poor maintenance, and overload, and close to 2000 lives were lost. In order to improve the connection, the maritime transport was reorganized, another ferry, “Aline Sitoe Diatta”, was bought, and the Farafeni’s bridge that crosses the Gambia was built. It is worth noting that ﬁshing activities are important, involving populations living in the coastal regions and islands, where some craftsmen build local canoes with integrated gasoline engines.

2.1.4. Railways Transportation Railways transportation began in Senegal in the 19th century during the colonial period and was intended for the exploitation of raw materials from the hinterlands and neighboring countries. After the independence in 1960, there has been a gradual decline in traffic, and poor management has led to the difficulties that plunged rail transport into a state of disrepair. The network is approximately 906 km long. A rehabilitation plan has been adopted by the government and investors are still expected. In an effort to modernize public transport in the overcrowded Dakar region, a 36 km long electric line, the “train express regional (TER)”, is being built and will help to smooth traffic between Dakar and its suburbs.

2.2. Greenhouse Gases and Transport Greenhouse gases (GHGs) originate from natural sources and human activities (anthropogenic sources): transport and trade, industry, commercial and residential buildings [15]. Earth 2021, 2 5

Identified GHGs are [16]: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and halogenated hydrocarbons (containing F, Cl, or Br). Carbon dioxide (CO2) is derived from the combustion of fossil fuels and represents the bulk of anthropogenic emissions. Methane (CH4) results from human activities such as farming, extraction of natural gas, pasture systems, and grass burning and from fermentation of organic matters. Nitrous oxide (N2O) originates from crop farming, biomass combustion, and industrial activities. Halocarbons and other synthetic fluoro-compounds (HFC, PFC, and SF6) derive mainly from human activities. Globally, the emissions counted come from the dominant subsector of road transport. International air transport and intercontinental maritime transport enjoy a legal vacuum as they contribute significantly to global warming, with planes and ships using large quantities of fuels. With regard to road transport, many factors influence emissions and are classified into four categories classified as follows [17]: vehicle characteristics (vehicle category, vehicle weight, type of fuel, age of the engines in the fleet, engine displacement, type of transmission, tire configuration, oil viscosity, aerodynamics, maintenance, etc.), the characteristics of the journey (load weight, distance of the trip, type of road, condition of the road, morphology of the road, character of the driver, use of embedded electronic devices, etc.), the characteristics of the trip (average speed, road congestion, etc.), and environmental characteristics (ambient temperature, wind speed, altitude, precipitation, humidity, use of the air conditioning system, engine temperature, etc.). The analysis of these characteristics shows from Senegal old and poorly maintained vehicles, low-quality fuels, tires in poor condition, weight and aerodynamics of vehicles often modified, and a lack of strict regulation. Trip analysis reveals overloaded vehicles (passenger and freight), unpaved or very poor roadways, frequent congestion, and careless and often unskilled drivers (without a driver’s license or obtained fraudulently). The state of the transport sector as described here above explains the poor performance as obtained in previous work [5,18].

2.3. Statistical Data Statistical data on the vehicle fleet can be obtained from several organizations [19–24]: the Ministry of Transport, the Ministry of Energy and Oil, and the National Agency for Statistics and Demography (ANSD). Challenges in data collection and lack of synergy between organizations make it difficult to obtain extensive, detailed, reliable, and consistent data. Data regarding the vehicle fleet and presented in this study are those of the ANSD and the Department of Road Transport (DTR) of the Ministry of Transport. Although these data differ, they display the same reality: an increasing number of imported vehicles. In Figure3, it can be seen how fast the number of new vehicles has been growing since 2004. Before 2012, a vehicle of more than five years old could not be imported. But the newly elected government brought the limit to eight. However, pollution and congestion in the main roads of Dakar have prompted the government to elaborate a new regulation to prohibit import of used vehicles. According to the DTR, the vehicle fleet had about 290,977 vehicles by 2005, and 468,051 vehicles by 2015. By conjecture, Senegal’s vehicle fleet would be around 600,000 vehicles in 2020. In Senegal, automotive vehicles are classified into several categories: trucks, taxi cabs, buses, and minibuses, light duty, and so forth. The age of the car fleet is around 20 years, justified by the presence of very old vehicles on the roads. The oldest vehicles are found among taxi cabs, coaches, construction equipment, and trucks, with an average between 28 and 33 years of age [25]. Vehicles in good condition or relatively young are ambulances and vehicles belonging to tourism companies. The number of seats in a vehicle varies and depends on its use. Light-duty vehicles have a limited number of seats, around five, and are used for urban trips, while vehicles intended for mass transport (buses and minibuses) have more seats, usually more than 10. Construction or freight vehicles only have seats for the driver and the assistant. According to the National Agency for Statistics and Demography (ANSD), the vehicle fleet in 2010 had Earth 2021, 2 6

a total of 326,000 vehicles, of which 278,258 were of less than five seats, representing 85% Earth 2020, 1, FOR PEER REVIEW 6 of 16 of the fleet (see Figure4). Around 5% of the fleet is made up of public transport vehicles: Earth 2020, 1, FOR PEERminibuses REVIEW (car rapid, ndiaga ndiaye, etc.), buses, and tourist vehicles. 6 of 16

Figure 3. IncreasingFigure 3. Increasingnumber of numberimported of cars imported (source: cars DTR (source:, 2015). DTR, 2015). Figure 3. Increasing number of imported cars (source: DTR, 2015).

Figure 4. Distribution of the vehicle ﬂeet by number of seats (Source: ANSD, 2010). Figure 4. Distribution2.4. of Methods the vehicle for fleet the Evaluation by number ofof Greenhouse seats (Source: Gas ANSD, Emissions 2010). Figure2.4.1. 4. Distribution Energy Consumption of the vehicle in fleet Transportation by number of seats (Source: ANSD, 2010). 2.4. Methods for the Evaluation of Greenhouse Gas Emissions Transport is an energy-intensive activity. Globally, it is second after the residential 2.4. Methods for thesector, Evaluation and consumes of Greenhouse nearly Gas 29% Emissions of the total energy consumed globally [26]. Road transport 2.4.1. Energy Consumption in Transportation is heavily dependent on fossil fuels, with gasoline and diesel covering almost all needs. Transport2.4.1. is an Energy energy -ConsumptionintensiveThe debate activity overin Transportation. whetherGlobally, heat it is enginessecond after (gasoline the residential or diesel) shouldsector, beand phased out is going consumes nearly 29%Transport of the total ison, an energy as energy hybrid consumed-intensive and electric globally activity vehicles [26]. Globally,. Road are progressively transport it is second is heavily after introduced the dependent residential in developed sector, countries. and on fossil fuels,consumes with gasoline nearly Airand 29% transport diesel of the covering total is very energy almost dependent consumed all needs. on globally hydrocarbons, The [26]debate. Road over aviation transport whether gasoline is heatheavily or kerosene dependent jet fuel being used in most aircrafts. Small and single-person or remotely controlled electric planes engines (gasolineon fossilor diesel) fuels, should with gasoline be phased and out diesel is going covering on, asalmost hybrid all and needs. electric The vehiclesdebate over are whether heat (drones) are under development with good prospects. Maritime transport is also heavily progressively intenginesroduc ed(ga insoline developed or diesel) countries. should Air be transportphased out is veryis going dependent on, as hybridon hydrocarbons and electric, vehicles are dependent on fossil fuels: gasoline, heavy fuel oil, and light marine diesel (domestic fuel) aviation gasolineprogressively or kerosene int roduc jet fueled inbeing developed used in countries. most aircrafts Air transport. Small is and very single dependent-person on or hydrocarbons , are the fuels used. Railways transport is an exception and uses not only fossil fuels, diesel, remotely controlled electric planes (drones) are under development with good prospects. Maritime aviation gasolineand or heavy kerosene fuel oil, jet but fuel also being electricity. used in most aircrafts. Small and single-person or transport is also heavily dependent on fossil fuels: gasoline, heavy fuel oil, and light marine diesel remotely controlled Typeselectric of planes energies (drones) by subsector are under in development Senegal (in 2013)with good are as prospec follows:ts. Maritime kerosene for (domestic fuel)transport are the fuels is also used.aviation, heavily Railways dieseldependent transport fuel for on railways fossilis an exceptionfuels: (not takengasoline, and into uses heavy account not fuel only in thisoil, fossil study),and fuels, light gasoline marine for diesel maritime diesel, and heavy(domestic fuel oil, fuel) but transport,alsoare the electricity. fuels and used. gasoline Railways and transport diesel for is roadways. an exception Fossil and fuelsuses not undergo only fossil an exothermic fuels, Types of energiesdiesel, and by heavysubsectorchemical fuel inoil, Senegal reaction but also (in (combustion) electricity. 2013) are as from follows: which kerosene heat is for released. aviation, The diesel energy released is then fuel for railways (notTypes taken of into energiesused account in by various insu bsectorthis processes study in )Senegal, gasoline such as(in for rotating2013) maritime are the as crankshaft, transportfollows: kerosene, and therefore gasoline for converting aviation, diesel heat into and diesel for fuelroad forways railways. Fossilwork. (not fuels taken The und quantity intoergo account an of exothermic heat in released this study chemical during), gasoline thereaction combustion for (combustion)maritime process transport from is given , and by gasoline Equation (1): which heat is andreleased diesel. The for energyroadways released. Fossil is fthenuels undusedergo in variousan exothermic processes chemical such as reaction rotating (combustion) the from E = m LHV (1) crankshaft, thereforewhich convertingheat is released heat .into The work. energy The released quantity is of then heat used released in various during processes the combustion such as rotating the process is givencrankshaft by Equation, therefore (1): converting heat into work. The quantity of heat released during the combustion process is given by Equation퐸 (1=): 푚 LHV (1) 퐸 = 푚 LHV (1)

Earth 2021, 2 7

where m is the mass (in kg) of fuel, and LHV is the lower caloriﬁc value. Fuels are sold on the market in volume, and the mass is obtained by multiplying with the density. Fuels generally have different LHVs, and the more energetic they are, the higher the values will be. LHV values (in MJ/kg) are given in Table1 for a number of fuels. As can be seen, fossil fuels (gasoline, diesel, fuel oil, etc.) are more energetic than those of biological origin, such as biogas. The total energy for a transport mode is deduced by summing the quantities of energies used in this subsector, and subsequently, the total energy consumed in the transportation sector is given by the sum of all quantities from all modes as given by (Equation (2)) where i refers to the fuel and j to the mode.

Ets = ∑ Ei,j (2) i,j

Table 1. LHV values for fuels.

LHV Density Fuels (MJ/kg) (kg/m3) Gasoline 44.80 750 Diesel 42.87 840 Aviation gasoline 44.80 704 Kerosene jet fuel 40.53 794 Marine gasoline 44.80 750

2.4.2. Calculation of Emissions of Carbon Dioxide, Methane, and Nitrous Oxide

Transport systems produce direct greenhouse gas emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from the combustion of fuels, and other pollutants such as carbon monoxide (CO), non-methane volatile organic compounds (NMVOCs), sulfur oxide (SO2), particulate matter (PM), and nitrogen oxides (NOx). The quantity and the quality of the emitted substances depend on the type of fuels. The IPCC guidelines provide methods for the estimate of the gases emitted by all transport modes which will further be used in this study. For the road subsector, carbon dioxide emissions are calculated on the basis of the type of fuel consumed and its quantity. The IPCC guidelines display two approaches (Tier 1 and Tier 2) for the estimation of the direct carbon dioxide emissions. The Tier 1 approach calculates carbon dioxide emissions by multiplying estimated fuel consumed with a default CO2 emission factor. The Tier 2 approach is the same as Tier 1 except that a country-specific emission factor of the fuel consumed is used. Three approaches are available for the estimation of methane and nitrous oxide emissions. The Tier 1 approach uses fuel-based emission factors and is used when it is not possible to estimate the fuel consumption by vehicle type. Tier 2 uses fuel-based emission factors and vehicles’ subcategories. The Tier 3 approach uses country-specific data, and emissions calculations are based on vehicle subcategory and activity level. In this study, the default values as given by the IPCC were used. Although it is suitable to use values close to the reality, lack of reliable and consistent data is a challenge. The factors used might lead to the underestimation of the emissions. Investigations showed that the national fleet was old, above 20 years, and some vehicles may be functioning without catalytic converters. The improper operation or lack of catalytic converter increases methane emissions while lowering the nitrous oxide emissions. The engine loading is another factor which can increase methane and nitrous oxide emissions. Most cars are located in Dakar, which has a high traffic density. Moreover, buses and minibuses are usually overloaded. Fuel composition is an issue. Poor fuel quality and high sulfur content are said to be responsible for the poor air quality. Dakar is one of the most polluted cities Earth 2021, 2 8

in West Africa as medical doctors reported increased rate of respiratory diseases. Poor fuel quality adversely affects the engine efficiency and increases the emission rates. The air transport is usually divided into four main categories: civil IFR and civil VFR flights, helicopters, and military flights. In general, two types of engines, reciprocating engines and gas turbines, are used in aircraft. Most aircraft run on kerosene jet fuel while small aircraft use aviation gasoline. Emissions depend on aircraft type, fuel type, engine type and load, and the flying altitude. The operation of an aircraft is divided into two main parts: the LTO (landing/takeoff) cycle and the cruise. LTO takes place below 1000 m, and includes taxi-in and -out, take-off, climb-out, and approaching-landing. Cruise takes place above 1000 m and includes climbing, cruising, and descending from cruise altitudes. All these phases have an impact on the fuel consumption and gas emissions. The IPCC guidelines provide three approaches for emissions estimates: Tier 1 based on fuel consumption, Tier 2 based on the number of LTOs and fuel use, and Tier 3 based on the data of individual aircraft. Although Tier 2 and 3 give more accurate results, Tier 1 will be used in this study as the only data available is regarding the fuel consumption. Moreover, the data obtained are related to the kerosene jet fuel sold in the country. Therefore, (Equation (3)) will be applied to determine the emissions of various gases along emissions factor default values provided by the IPCC guidelines. Marine transport covers all water-borne transport from recreational boats to cargo ships (ferries, tankers, carriers, container vessels, etc.) and includes ocean-going, in-port, and inland waterway activities. Marine and inland vessels use mainly steam, diesel, and gasoline (2/4 stroke) heat engines. Electricity, hydrogen, and fuel cells are yet to be adapted in water transport. The combustion of the utilized fossil fuels (coal, gasoline, diesel, and bunker or distillate) generates greenhouse gases and pollutants as well. The emissions could be also evaluated based on the IPCC guidelines which provides two approaches (Tier 1 and Tier 2). The Tier 1 approach is based solely on the fuel consumption. The Tier 2 approach emphasizes the fuel type and engine type. In this study, the Tier 1 approach is used, thus applying (Equation (3)) for all gases. Moreover, the statistical data available take only into account the fishing activities along the coastal areas and the rivers in the country. Fishing activities are carried out by small groups of fishermen who use gasoline engines. It is assumed here they are two-stroke type engines similar to those found in European inland waterways. The default emission factors used are displayed in Table2. Railway transport uses diesel and electric locomotives. Diesel locomotives tend to be more popular and are grouped into three main categories: railcars and yard and haul locomotives. Electric locomotives are powered by stationary power plants. The estimate of the emissions in this subsector depends on the quality, quantity, and consistency of the available data. Unfortunately, for this mode, it was not possible to get any data despite the long history of the railway in Senegal. It should be recalled that the railway reached Senegal during the colonial period (19th century), but was progressively abandoned after the 1960s.

Emissions of the main greenhouse gases (carbon dioxide (εCO2 ), methane (εCH4 ) and

nitrous oxide (εN2O)) can be evaluated using Equation (3) [27]. Emission of a speciﬁc gas is obtained by multiplying the energy of each fuel k, Ek (in TJ) by the emission factor of the GHG gas, fk (in kg/TJ) contained in Table2 as given by the IPCC [28].

GHG εGHG = ∑ Ek. fk (3) k

Emissions can be further converted into CO2 equivalent, taking into account their global warming potential (GWP). With carbon dioxide as the reference, Table3 gives the global warming potential of several substances, including nitrous oxide and methane, which tend to be higher than that of the carbon dioxide. Nevertheless, the concentration of the carbon dioxide is much higher as the product of the combustion in the atmosphere. Total amount of carbon dioxide (i.e., the global effect of all three greenhouse gases) is Earth 2021, 2 9

therefore given using Equation (4) (as CO2-eq) in which i refers to the fuel, k to the gas, and αGHG is the global warming potential of the gas.

= GHG;k εCO2−eq ∑ ∑ Ei.αGHG,k. fi (4) i k

Table 2. Emission factors for greenhouse gases, source: Ref. [28].

Emission Factors Fuels CH N O CO (kg/TJ) 4 2 2 (kg/TJ) (kg/TJ) Gasoline/road 69,300 33 3.2 Diesel/road 74,100 3.9 3.9 Gasoline/water * 71,000 110 0.4 Jet kerosene/air 71,500 0.5 2 * IPCC default emission factors for European ships and boats on inland waterways (two-stroke engine).

Table 3. GHGs and Global Warming Potentials (GWP), source: Refs [29,30].

Chemical GWP (Over Substances Sources Formula 100 Years)

Carbon dioxide CO2 1 Combustion processes Landﬁlls, coal mining, wastewater Methane CH 25 4 treatment, biomass combustion Agricultural soils and nitric Nitrous oxide N O 298 2 acid production

3. Results 3.1. Energy Consumption Details on fuel consumption in the period 2000–2013 are given in Table4, by transport mode and by fuel type. Energy consumption analysis shows the dominance of road transport (see Figure5). It is seen that in the period 2000–2013, the share of the road transport has been increasing over the years, to reach up to 95% in 2013. Trips using motorized vehicles take place most often on roads. This is a characteristic found in developing nations, where transport facilities are not well established. For the specific case of Senegal, road transport appears as the most affordable means of transport, but the reality on the ground is complex. In this subsector, diesel is the most used fuel (Figure6), and this is justified by its price, lower than that of gasoline. The country’s vehicle fleet is made up of 59% diesel engines which consume 81% of total energy (see Figure6). This is partly explained by the fact that most diesel vehicles are used for public transport. Transport businesses see them as more profitable. Railways transport (not taken into account in the study) is in poor condition, and data on this mode are rather scarce. Nevertheless, efforts are being made to rehabilitate the existing infrastructure. Internal passenger transport with tram and metro is yet to be developed. Maritime transport is limited to the Atlantic coast, to passenger transport between the regions of Dakar and Casamance and to fishing activities. Air transport, which was a dynamic subsector before 2006, is declining due to the bankruptcy of successive companies. From 39%, its share in the energy consumption came down to almost 0%. A new airport was inaugurated in 2018 and a new company, Air Senegal, was created in 2019 to bring more activities in this subsector. However, air transport, less popular than road, will continue to serve a minority of privileged people with high income. Earth 2021, 2 Earth 2020, 1, FOR PEER REVIEW 10 of 16 10

Earth 2020, 1, FOR PEER REVIEW 10 of 16 Table 4. Fuel consumption (2000–2013), source: Refs [29,30].

Year RoadTable Table 4. Fuel 4. Fuel consumption consumption (2000–2013), (2000–Aviation2013 source:), source: Refs R [29efs,30 [29,30]. Water]. Total Gasoline Diesel Kerosene Gasoline Year Road Year RoadAviation AviationWater WaterTotal Total GasolinePJ % DieselPJ % KerosenePJ % GasolinePJ % PJ Gasoline Diesel Kerosene Gasoline 2000 PJ 2.54 % 9.55 PJ 12.08 % 45.49 PJ 10.41 % 39.20 PJ 1.53 % 5.76 PJ 26.56 2001 2.67 10.65 11.82 47.21 8.92 35.65 1.62 6.48 25.03 2000 2.54 9.55 PJ12.08 %45.49 PJ10.41 % 39.20 PJ %1.53 PJ5.76 %26.56 PJ 2002 2.89 11.70 12.99 52.51 7.17 28.98 1.68 6.81 24.73 2001 2.67 200010.65 2.5411.82 9.5547.21 12.088.92 45.49 35. 10.4165 39.201.62 1.536.48 25. 5.7603 26.56 2003 3.06 10.71 14.58 51.02 9.20 32.19 1.73 6.07 28.57 2002 2.89 200111.70 2.6712.99 10.6552.51 11.827.17 47.21 28.98 8.92 35.651.68 1.626.81 24. 6.4873 25.03 2004 3.13 10.08 16.13 51.94 10.23 32.94 1.56 5.03 31.06 2003 3.06 200210.71 2.8914.58 11.7051.02 12.999.20 52.51 32.19 7.17 28.981.73 1.686.07 28. 6.8157 24.73 2005 3.072003 10.10 3.06 15. 10.7150 50. 14.5895 51.0210.45 9.2034.33 32.191.40 1.734.62 6.0730.43 28.57 2004 3.13 10.08 16.13 51.94 10.23 32.94 1.56 5.03 31.06 2006 2.962004 9.05 3.13 17. 10.0812 52. 16.1334 51.9411.29 10.2334.52 32.941.34 1.564.09 5.0332.70 31.06 2005 3.07 10.10 15.50 50.95 10.45 34.33 1.40 4.62 30.43 2007 3.262005 11.93 3.07 21. 10.1059 78. 15.5087 50.951.26 10.454.60 34.331.26 1.404.61 4.6227.37 30.43 2006 2.96 20069.05 2.9617.12 9.0552.34 17.1211.29 52.34 34. 11.2952 34.521.34 1.344.09 32. 4.0970 32.70 2008 3.19 12.71 19.63 78.32 0.99 3.94 1.26 5.04 25.06 2007 3.26 200711.93 3.2621.59 11.9378.87 21.591.26 78.87 4.60 1.26 4.601.26 1.264.61 27. 4.6137 27.37 2009 3.65 13.55 21.61 80.22 0.08 0.28 1.61 5.96 26.94 2008 3.19 200812.71 3.1919.63 12.7178.32 19.630.99 78.32 3.94 0.99 3.941.26 1.265.04 25. 5.0406 25.06 2010 3.84 13.66 22.83 81.29 0.15 0.55 1.26 4.49 28.09 2009 3.65 200913.55 3.6521.61 13.5580.22 21.610.08 80.22 0.28 0.08 0.281.61 1.615.96 26. 5.9694 26.94 2011 3.92 13.06 24.36 81.24 0.45 1.49 1.26 4.21 29.99 2010 3.84 201013.66 3.8422.83 13.6681.29 22.830.15 81.29 0.55 0.15 0.551.26 1.264.49 28. 4.4909 28.09 2012 3.99 13.91 23.33 81.38 0.03 0.12 1.32 4.59 28.67 2011 3.92 201113.06 3.9224.36 13.0681.24 24.360.45 81.24 1.49 0.45 1.491.26 1.264.21 29. 4.2199 29.99 2013 4.512012 14.17 3.99 25. 13.9171 80. 23.3376 81.380.01 0.030.03 0.121.61 1.325.04 4.5931.83 28.67 2012 3.99 13.91 23.33 81.38 0.03 0.12 1.32 4.59 28.67 2013 4.51 14.17 25.71 80.76 0.01 0.03 1.61 5.04 31.83 2013 4.51 14.17 25.71 80.76 0.01 0.03 1.61 5.04 31.83

Figure 5. Distribution of the energy consumed by mode in the period 2000–2013 (source: adapted from data givenFigure by 5. theDistribution Ministry of of Energy the energy and Petroleum) consumed. by mode in the period 2000–2013 (source: adapted Figure 5. Distribution of the energy consumed by mode in the period 2000–2013 (source: adapted from data given by the Ministry of Energy and Petroleum). from data given by the Ministry of Energy and Petroleum).

Figure 6. Energy consumption distribution by fuel (left) and distribution of car ﬂeet by type of motor Figure 6. Energy(source: consumption ANSD, 2013). distribution by fuel (left) and distribution of car fleet by type of motor (source: ANSD, 2013). Figure 6. Energy3.2. consumption Greenhouse distribution Gas Emissions by fuel (left) and distribution of car fleet by type of motor (source: ANSD, 2013). Data from Table 4 were used to draw the evolution of different gases emitted after combustion in fossil-fuel-driven engines. Figures7–11 show the evolution of the main greenhouse gases. Direct carbon dioxide emissions come from all transport subsectors

Earth 2020, 1, FOR PEER REVIEW 11 of 16

3.2. Greenhouse Gas Emissions Earth 2021, 2 11 Data from Table 4 were used to draw the evolution of different gases emitted after combustion in fossil-fuel-driven engines. Figures 7–11 show the evolution of the main greenhouse gases. Direct carbon dioxide emissions come from all transport subsectors (road, aviation, and maritime transport), except rail transport(road,, which aviation, is not and taken maritime into account transport),. Figure except 7 shows rail the transport, evolution which of this is notgas takenin the into period 2000–2013account.. As it can Figure be seen7 shows, the thecarbon evolution dioxide of from this gas the in road the periodis steadily 2000–2013. increasing As, it reaching can be seen, 2.21 million tonsthe in carbon2013, 86% dioxide coming from from the the road combustion is steadily of increasing, diesel oil. reaching The contribution 2.21 million of aviation tons in 2013, 86% coming from the combustion of diesel oil. The contribution of aviation was between 28 was between 28 and 43%, peaked at 43% in 2004, before it fell below 4% after 2005. Air transport and 43%, peaked at 43% in 2004, before it fell below 4% after 2005. Air transport played a played a significant role in the period 2000–2006, but has always been a difficult business in Senegal. significant role in the period 2000–2006, but has always been a difficult business in Senegal. In 1961, 11 countriesIn 1961, including 11 countries Senegal including set up Air Senegal Afrique set and up by Air 2002, Afrique it closed and bydown. 2002, Senegal it closed had down. a public company,Senegal Air had Senegal, a public founded company, in Air 1971 Senegal,, which founded in 2000 in went 1971, bankrupt. which in 2000 Later went on, bankrupt. the government joinedLater with on, Roy the governmental Air Maroc, joined a Moroccan with Royal company Air Maroc,, to create a Moroccan Air Senegal company, International to create Air (ASI) in 2001. MismanagementSenegal International and disagreements (ASI) in 2001. among Mismanagement partners led and to a disagreements progressive decline among from partners 2006, and to its ledclosure to a progressivein 2009. Local decline entrepreneurs from 2006, with and tothe its support closure inof 2009.the government Local entrepreneurs founded with Senegal Airlinesthe in support2011, which of the was government dissolved founded in 2015. SenegalIn 2019, Airlines the government in 2011, which launched was another dissolved in company, Air Senegal.2015. In This 2019, brief the governmenthistorical review launched justifies another the variations company, observed Air Senegal. in carbon This brief dioxide historical emissions from reviewair transport. justifies The the contribution variations observed of maritime in carbon transport dioxide is emissionsbetween 4 from and air7% transport. and was The 114,000 tons in 2013.contribution It is worth of maritime noting that transport only gasoline is between used 4 by and fishermen 7% and was was 114,000 taken into tons account in 2013. It is in this study. Roadworth transport noting thatprovides only gasolinea significant used amount by fishermen of carbon was dioxide taken into due account to the growing in this study. vehicle fleet, dieselRoad fuel, transport economic provides activities a significant, and other amount factors of like carbon climate. dioxide Road due represents to the growing 52–96 vehicle% fleet, diesel fuel, economic activities, and other factors like climate. Road represents 52–96% of direct carbon emissions. of direct carbon emissions.

Earth 2020, 1, FOR PEERFigure REVIEW 7. Dynamics of the direct carbon dioxide emissions (2000–2013). 12 of 16 Figure 7. Dynamics of the direct carbon dioxide emissions (2000–2013).

Methane is a gas emitted by natural sources and as well by combustion of fossil fuels. Figure 8 shows that on the roads, the quantity of methane emitted is steadily increasing; from 130 tons in 2000, it reached 249 tons in 2013. Its share is between 42 and 61%. Maritime transport is the second contributor, with a share between 40 and 57%. Aviation has a very small impact, with nearly zero tons in 2013. In the period 2000–2013, aviation emitted less than 6 tons of methane per year. Nitrous oxide, as seen in Figure 9, is mostly emitted on roads. It is seen that its amount is constantly increasing. From 55.25 tons in 2000, it reached 114.59 in 2013. Its share was also increased from 72% up to 99%. Aviation emitted between 19 and 31%, and decreased drastically below 1% because of the low level of activity in this subsector. Maritime transport emits less than 1 ton/year while its share remains below 1%.

Figure 8. Dynamics and origin of methane emissions (2000–2013). Figure 8. Dynamics and origin of methane emissions (2000–2013).

Figure 9. Dynamics and origin of nitrous oxide emissions (2000–2013).

The effects of all greenhouse gases can be evaluated, taking the action of carbon dioxide as reference, thus using the global warming potential. Figure 10 shows the origin and the evolution of carbon dioxide emissions, which increase over time, from 1.96 up to 2.38 million tons in 2013. Road transport is the most important emitter, and sees its share increasing from 55% up to 95%. In the period 2000–2005, aviation emitted about 28–43% of total emissions before its contribution decreased down to almost 0%. Maritime transport emits an average of 108 ktCO2-eq/year, and its share is less than 7% and decreases over the years. At this point, one can conclude that the greenhouse gases in the transport sector in Senegal are mainly due to road transport. Figure 11 shows the impact of different fuels over time. The impact of the road gasoline is almost stable, with an average of 11.50%, and that of the maritime gasoline as well (5.28%). The impact of the aviation jet fuel, as high as 35% in the period 2000–2006, is less than 5% from 2006 and after. The negative impact of the diesel fuel has been growing over the studied period, from 46.59 in 2000 up to 81.50%. Therefore, the emissions produced by the transport sector is due to road transport, and more specifically, diesel oil has a key role.

Earth 2020, 1, FOR PEER REVIEW 12 of 16

Earth 2021, 2 12 Figure 8. Dynamics and origin of methane emissions (2000–2013).

Earth 2020, 1, FOR PEER REVIEW 13 of 16 Earth 2020, 1, FOR PEERFigure REVIEW 9. Dynamics and origin of nitrous oxide emissions (2000–2013). 13 of 16 Figure 9. Dynamics and origin of nitrous oxide emissions (2000–2013).

specifically, diesel oil has a key role. FigureFigure 10. 10.Total Total emissions emissions from from the the transport transport sector sector in thein the period period 2000–2013. 2000–2013. Figure 10. Total emissions from the transport sector in the period 2000–2013.

Figure 11. Evolution of the impact (CO2-eq) of each fuel (2000–2013). Figure 11. Evolution of the impact (CO2-eq) of each fuel (2000–2013). Figure 11. Evolution of the impact (CO2-eq) of each fuel (2000–2013). Methane is a gas emitted by natural sources and as well by combustion of fossil fuels. Fuel consumption is followed by the emission of harmful substances, and the more energy is Fuel consumptionFigure 8is shows followed that by on the the emission roads, the of quantity harmful ofsubstances methane, emitted and the is more steadily energy increasing; is consumed, the higher will be the emissions. Nevertheless, the link between fuel consumption, consumed, the higher will be the emissions. Nevertheless, the link between fuel consumption, greenhouse gas emissions, and economic growth should also be mentioned. Figure 12 shows the greenhouse gas emissions, and economic growth should also be mentioned. Figure 12 shows the correlation between the GDP (gross domestic product) and the emissions in the transportation sector correlation between the GDP (gross domestic product) and the emissions in the transportation sector of Senegal. Data related to the GDP were extracted from Ref. [8]. The GDP per capita has been of Senegal. Data related to the GDP were extracted from Ref. [8]. The GDP per capita has been increasing since 1990, from 1447 up to US$ 3430 in 2018 [8]. In the periods 2000–2004 and 2006–2013, increasing since 1990, from 1447 up to US$ 3430 in 2018 [8]. In the periods 2000–2004 and 2006–2013, it is seen that the GDP correlates with the greenhouse gas emissions increasing; the GDP/capita it is seen that the GDP correlates with the greenhouse gas emissions increasing; the GDP/capita increases with the carbon dioxide emissions. This confirms that at some point, the emissions in the increases with the carbon dioxide emissions. This confirms that at some point, the emissions in the transport sector are strongly correlated with economic growth. transport sector are strongly correlated with economic growth.

Earth 2021, 2 13

from 130 tons in 2000, it reached 249 tons in 2013. Its share is between 42 and 61%. Maritime transport is the second contributor, with a share between 40 and 57%. Aviation has a very small impact, with nearly zero tons in 2013. In the period 2000–2013, aviation emitted less than 6 tons of methane per year. Nitrous oxide, as seen in Figure9, is mostly emitted on roads. It is seen that its amount is constantly increasing. From 55.25 tons in 2000, it reached 114.59 in 2013. Its share was also increased from 72% up to 99%. Aviation emitted between 19 and 31%, and decreased drastically below 1% because of the low level of activity in this subsector. Maritime transport emits less than 1 ton/year while its share remains below 1%. The effects of all greenhouse gases can be evaluated, taking the action of carbon dioxide as reference, thus using the global warming potential. Figure 10 shows the origin Earth 2020, 1, FOR PEERand REVIEW the evolution of carbon dioxide emissions, which increase13 over time, from 1.96 up to 2.38 million tons in 2013. Road transport is the most important emitter, and sees its share increasing from 55% up to 95%. In the period 2000–2005, aviation emitted about 28–43% of total emissions before its contribution decreased down to almost 0%. Maritime transport emits an average of 108 ktCO2-eq/year, and its share is less than 7% and decreases over the years. At this point, one can conclude that the greenhouse gases in the transport sector in Senegal are mainly due to road transport. Figure 11 shows the impact of different fuels over time. The impact of the road gasoline is almost stable, with an average of 11.50%, and that of the maritime gasoline as well (5.28%). The impact of the aviation jet fuel, as high as 35% in the period 2000– 2006, is less than 5% from 2006 and after. The negative impact of the diesel fuel has been growing over the studied period, from 46.59 in 2000 up to 81.50%. Therefore, the emissions produced by the transport sector is due to road transport, and more speciﬁcally, diesel oil has a key role. Fuel consumption is followed by the emission of harmful substances, and the more

energyFigure 11. is Evolution consumed, of the impact the higher (CO2-eq) of will each be fuel the (200 emissions.0–2013). Nevertheless, the link between fuel consumption, greenhouse gas emissions, and economic growth should also be mentioned. Fuel consumptionFigure is followed12 shows by the emission correlation of harmful between substances the, GDPand the (gross more energy domestic is product) and the emis- consumed, the higher will be the emissions. Nevertheless, the link between fuel consumption, greenhouse gas emissionssions in, and the economic transportation growth should sector also of be Senegal. mentioned Data. Figure related 12 shows to thethe GDP were extracted from correlation betweenRef. the [GDP8]. The(gross GDP domestic per product) capita and has the beenemissions increasing in the transportation since 1990, sector from 1447 up to US$ 3430 of Senegal. Data in related 2018 to [the8]. GDP In the were periods extracted 2000–2004 from Ref. [8]. and The GDP 2006–2013, per capita it has is been seen that the GDP correlates increasing since 1990,with from the 1447 greenhouse up to US$ 3430 gas in emissions2018 [8]. In the increasing; periods 2000– the2004 GDP/capita and 2006–2013, increases with the carbon it is seen that the GDP correlates with the greenhouse gas emissions increasing; the GDP/capita increases with thedioxide carbon dioxide emissions. emissions This. This conﬁrms confirms that that at atsome some point, point, the emissions the emissions in the in the transport sector transport sector areare strongly strongly correlated correlated with economic with economicgrowth. growth.

Figure 12. Correlation between emissions (ktCO2-eq) and GDP per capita in the period 2000–2013. Figure 12. Correlation between emissions (ktCO2-eq) and GDP per capita in the period 2000–2013. Commented [UW15]: Change done

4. Discussion 4. Discussion Carbon dioxide emissionsCarbon as dioxideseen in the emissions previous section as seen are mainly in the due previous to diesel oil, section which at are mainly due to diesel oil, the same time produceswhich pollutants at the same like sulfur time dioxide, produces particle pollutants matter, carbon like dioxide sulfur, and dioxide, carbon particle matter, carbon monoxide, responsibledioxide, for several and carbondiseases monoxide,(asthma, lung responsiblecancer, cardiovascular for several attacks, diseases etc.). It is (asthma, lung cancer, car- worth noting thatdiovascular this fuel will be attacks,banned in etc.).the upcoming It is worth years in noting some countries that this across fuel the will world, be banned in the upcoming while in African nations, no debate has been organized around the adverse effects of this fuel. Public Eye, a Swiss NGOyears (non- ingovernmental some countries organization) across con theducted world, a study while which in showed African poor nations, fuels no debate has been orga-

Earth 2021, 2 14

nized around the adverse effects of this fuel. Public Eye, a Swiss NGO (non-governmental organization) conducted a study which showed poor fuels (with high level of sulfur and other pollutants like benzene) produced in Europe were dumped in Africa [12]. The World Health Organization (WHO) has urged African nations to put strict regulations on fuels and invest in establishing clean processes in local refineries to improve the quality of local products. A policy aiming at protecting the environment and reducing the negative impact of fossil fuels, and in particular, diesel, should be considered in Senegal. The first step will be to eliminate the use of diesel in light vehicles, but this is a huge challenge. In 2009, it was decided to establish a center dedicated to the monitoring of outdoor air quality (Centre de Gestion de la Qualité de l’Air—CGQA) and a center in charge of the technical control of vehicles (Centre de Contrôle Technique des Véhicules Automobiles—CCTVA) in Dakar. Both centers are active, but operate only in the capital city. The extension to other major cities (Thies, Saint Louis, or Touba) is still awaited. Beyond the fuel, actions in the direction of improving infrastructure and reducing the number of old vehicles with low efficiency should be taken. The government is about to introduce a new regulation to reduce the import of used vehicles, even though very old vehicles will still be found on roads. Another regulation on recycling of old vehicles would be more effective, but this approach is yet to be studied. Improvements of the road network are underway, but the maintenance of existing infrastructure is a huge challenge. In the Dakar region, a bus rapid transit (BRT) is under construction to reduce traffic congestion on main highways. The electric railway line (TER) will smooth the transport between Dakar, the Diamniadio airport, and its suburbs. Renewal of part of the vehicle fleet has been recorded and the introduction of a new and stricter driving license is in preparation. Substantial efforts remain to be made in the quality control of fuels, the introduction of electric motors, and the organization of less emitting means of transportation such as the bicycle. On the other hand, the automotive value chain is not fully mastered. The country does not have an automobile industry, and almost all vehicles in the fleet come from abroad in used condition. Special emphasis must be placed on training and mastery of the value chain including recycling. The idea of producing electricity in solar photovoltaic plants to power electric vehicles is not incongruous and deserves in-depth investigations. Transport research is important as well as data collection. Reliable data should be available from different stakeholders and agencies so as to allow researchers to get insight into transport systems. Moreover, research in dedicated labs is important, and curric- ula should be made available on different aspects of transport: engineering, economics, sociology, logistics, and so forth.

5. Conclusions The transportation sector of Senegal is multimodal with a dominant roadways subsector. Fossil fuel consumption is dominated by diesel oil, which generates the bulk of emissions. These emissions are increasing over the years, as seen in the period 2000–2013, and are favored by several factors, including the poor condition of the roads, the aging vehicle fleet, and so forth. The government is developing important projects like highways, airport, electric railway, and BRT construction, and installation of an air quality monitoring system, but a lot remains to be done. A sustainable transport policy should be established that would include a focus on light-duty diesel vehicles and their renewal, and in particular, light-duty vehicles, taxi cabs, and coaches with an average age of approximately 30 years. The modernization of transport infrastructure, with facilities in all parts of the country, must be a priority. The government would benefit from setting up a policy for the automotive sector, ranging from manufacturing to recycling, and whose benefits are numerous: protection of the environment, preservation of the health of populations, rebalancing of the trade balance, and job creation.

Funding: This research received no external funding. Conﬂicts of Interest: The author declares no conﬂict of interest. Earth 2021, 2 15

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