Estimating greenhouse gas emissions from port vessel operations at the Lagos and Tin Can ports of Nigeria

Greenhouse gas (GHG) emission, the number one contributor to global warming is not just a product of in-land transportation, industries and other anthropogenic effect but also the maritime and shipping industries. This article estimates the amount of greenhouse gases emitted from port vessel operations in the Lagos and Tin Can ports of Nigeria. The emission estimate was carried out based on the type of the vessel and its movement from the moment of its arrival (400 km from the coast). The emission estimate was done using the bottom-up approach based on the characteristics of individual vessels and using data on vessels processed by both ports in the first and second quarter of the year 2017. Among various types of vessels, Premium Motor Spirit (PMS) carriers are the heaviest emitters, followed by the container vessels and general cargo vessels. Result for the first and second quarter of 2017 indicates that approximately 16,335 t and 773 t of CO2 were produced and emitted during anchorage and while passing through lock gates movement, respectively. Also, 644 t of CO2 was emitted through maneuvering to the dock movement. Consequently, these three movements account for 85% of the total CO2 ABOUT THE AUTHOR Professor David O. OLUKANNI is a faculty in Civil EngineeringDepartment at CovenantUniversity. He is a Fulbright Scholar; studied at the University of Oklahoma, Norman and researched at North Carolina State University, Raleigh, U.S.A. He was Chair of Civil Engineering and currently Director, Quality and Academic Standards, Covenant University. He is a member of Council for the Regulation of Engineering in Nigeria (COREN); Nigerian Society of Engineers (NSE) and American Society of Civil Engineers (ASCE). He has published widely and serves on Editorial Board and reviewer for several journals. He serves as assessor and external examiner for postgraduate dissertations and thesis. He is the research cluster head of Urban Environmental IssuesandNationalDevelopmentat Covenant University. His research interest includes: Solid Waste Management; Environmental Sustainability; Rural-Urban Water Supply, Wastewater Management, Rural/Urban Sanitation and Hygiene studies. He has supervised and mentored several students towards the award of their degrees. PUBLIC INTEREST STATEMENT Greenhouse gas (GHG) emission, the number one contributor to global warming is not just a product of in-land transportation, industries and other anthropogenic effect, but also the maritime and shipping industries. These emissions are known to contribute to lung cancer, cardio vascular and cardio pulmonary functions, allergies and asthma, particularly for the inhabitants of communities lying along the sea shore. This article estimates the amount of GHGs emitted from port vessel operations in the Lagos and Tin Can ports of Nigeria. The emission estimate was done using the bottom-up approach based on the characteristics of individual vessels and using data on vessels processed by both ports in the first and second quarter of the year 2017. These movements of vessels considered account for 85% of the total CO2 emission from Lagos and Tin Can ports. It was found that if provisions are made for electricity from land, about 5% of the estimated emissions during cargo handling can be avoided. Olukanni & Esu, Cogent Engineering (2018), 5: 1507267 https://doi.org/10.1080/23311916.2018.1507267 © 2018 The Author(s). This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license. Received: 30 April 2018 Accepted: 30 July 2018 First Published: 07 August 2018 *Corresponding author: David O. Olukanni, Department of Civil Engineering, Covenant University, Ota, Ogun State, Nigeria E-mail: david.olukanni@covenantuniversity.edu.ng Reviewing editor: Mutiu Kolade Amosa, University of the Witwatersrand, South Africa Additional information is available at the end of the article


PUBLIC INTEREST STATEMENT
Greenhouse gas (GHG) emission, the number one contributor to global warming is not just a product of in-land transportation, industries and other anthropogenic effect, but also the maritime and shipping industries. These emissions are known to contribute to lung cancer, cardio vascular and cardio pulmonary functions, allergies and asthma, particularly for the inhabitants of communities lying along the sea shore. This article estimates the amount of GHGs emitted from port vessel operations in the Lagos and Tin Can ports of Nigeria. The emission estimate was done using the bottom-up approach based on the characteristics of individual vessels and using data on vessels processed by both ports in the first and second quarter of the year 2017. These movements of vessels considered account for 85% of the total CO 2 emission from Lagos and Tin Can ports. It was found that if provisions are made for electricity from land, about 5% of the estimated emissions during cargo handling can be avoided.

Introduction
The rise in shipping activities in the past two decades has made shipping standout amongst the most polluting industries. Emissions related with shipping industries have been overlooked in the past. However, attention of researchers is now drawn to gas emissions (Olukanni & Adebiyi, 2012) and the pollution effect (Olukanni & Aremu, 2017;Williams & Nsikak, 2010) as this medium of transportation is viewed as a very proficient method of transportation with regard to tonnage of cargo transported per kilometre travelled (IMO, 2016a). Global emissions from shipping have increased considerably, contributing to global anthropogenic emissions and most importantly impacting air pollution through climate change, reduction of ozone layer thickness and acid rain (Saraçoǧlu, Deniz, & Kiliç, 2013;Song & Shon, 2014). Consequently, public concerns about environmental and health impacts of maritime traffic emissions are increasing and the need to protect people and their socio-economic activities is important (Olukanni, Adejumo, Adedeji & Salami, 2016).
The most important pollutants produced by ships in in-port and international routes are particulate matters, volatile organic compounds and carbon (II) oxide (with effect on human wellbeing), as well as sulphur oxides (SOx) and nitrogen oxides (NOx) (contributing to the formation of acid rain), particulate matter through photochemical pathway and tropospheric ozone (O 3 ) formation, carbon dioxide (CO 2 ), black carbon (BC) and methane (CH 4 ) due to their role on the greenhouse effect (Eyring et al., 2009;Matthias, Bewersdorff, Aulinger, & Quante, 2010) CO 2 is a major ozone depleting substance discharged by ships with respect to amount and global temperature alteration potential. As presented in the 3rd International Maritime Organization Greenhouse Gas Emission Study (2014), global shipping discharged 796 million tons of CO 2 in 2012, showing 2.2% of aggregate emission volume that year. It was projected that by 2050, 15% of aggregate CO 2 emissions would be attributed to maritime transport (IMO, 2016a). Recent global assessments show that no less than 70% of emissions from vessels occur within 400 km from the coast, and the pollutants of these discharges can be transported several kilometres into the mainland, causing air quality issues even in extremely remote territories of the seaside zone (Corbett et al., 2009;Song & Shon, 2014). Emissions are also generated while ships are at ports and most of the environmental impacts associated with ships are caused due to the day-to-day operations such as in-port shipping activities (Ng et al., 2013;Song & Shon, 2014). These emissions contribute to lung cancer, loss of lung, cardio vascular and cardio pulmonary functions, allergies and asthma, particularly for inhabitants of regions lying along the sea shore (Eyring et al., 2009;Song & Shon, 2014).
From the forgoing, a more critical investigation of GHG emissions from ports is required, so as to help port authorities control current emission levels and figure out strategies to reduce GHG discharge. This work bridges a gap in literature by giving a thorough investigation of GHG emissions with respect to information from all vessels handled by Lagos and Tin Can ports in the first and second quarter of 2017. In precise terms, this article gauges GHG emissions emanating with respect to the category of vessel and the course of the vessel from the moment it arrives at the port, 400 km from the coast to unloading and finally departure.

The Lagos and Tin Can Ports of Nigeria
The oldest and biggest port in Nigeria is the Lagos Port which is also referred to as Premiere Port (Apapa Quays). It is located in the commercial hub of Nigeria, Apapa, Lagos State ( Figure 1). The Port was established in 1913 and the construction of the first four deep water berths commenced in 1921. The port is made of state of the heart facilities ranging from modern cargo handling equipment to personnel support facilities. It has good linkages with various means of transportation such as rail, road and water. It has four wheel gates of 8 meters long for oversize cargoes which gives it an added advantage in oversize cargoes handling (NPA, 2017).
The federal government introduced the landlord Port model for improved efficiency and operational activities. In 2006, the operation of the terminals was carried out by private operators. Now, Lagos port has five terminals all run privately by five operators with expert management and individuals with local and international experience in port operation. There are two logistics bases in the Lagos port, these are; Eko Support Services Ltd. and Lagos Deep Offshore Logistics (LADOL). These logistics bases have eight jetties. Operators own factories where sugar, salt and flour are produced in the port. Lagos port is registered and certified with the International Maritime Organization (IMO). The port runs for 24 hours with remarkable vessel turnaround time. The security personnels in the port are made of armed and unarmed individuals. Monitoring is also carried out with CCTV cameras placed at strategic positions in the port (NPA, 2017).
Close to Lagos Port Complex is the Tin Can Port (North West of Lagos port). During the oil boom period in 1975, there was a hike in economic activities in the country. Also, the rebuilding activities that took place after the civil war led to a rise in the volume of import and export which gave rise to congestion in Lagos port. As a result; there was need for the government to construct a new

Method of data collection
Emissions by each type of vessels at each phase of their course were gauged, from the moment it enters the port, 400 km from the coast to the point of unloading and exit. To estimate the CO 2 emitted, a measure of the fuel consumed by each type of vessel over their course of movement in the port was gauged. Fuel consumed by a ship for a given distance is taken into consideration and the quantity of fuel consumed by both the main and auxiliary engine of the ship was gauged (Corbett et al., 2009). Typical examples of the application of this technique involving Equations (1) and (2) in assessing CO 2 emissions in Taiwan's Kaohsiung harbour and Korea's Port of Incheon are based on NPA (2017) and Chang, Younghun, & Younghoon (2013), respectively. Based on the success of previous works and the type of data available from the Nigeria Port Authority (NPA), this method was adopted. The method was harnessed mainly to evaluate fuel consumptions of both the main and auxiliary engines from point to point from when the vessel is at about 400 km (215 nautical miles) from the coast of each of these ports (Figure 2).
The quantity of fuel used by a vessel at any stage of its movement within the port is given in Equation 1 (Chang et al., 2013;NPA, 2017) as: (1) where F ijk denotes the quantity of fuel used by vessel k moving from point i to j; MF k denotes the fuel used by the main engine daily; AF k denotes the fuel used by the auxiliary engine daily; S 1k denotes the operational speed of the vessel (nm/h); S 0k denotes the design speed of the vessel (nm/h) and d ij denotes the distance between point i and j.
After estimating the fuel used, CO 2 emissions are then calculated from fuel combustion. Variations in the type of fuel used by vessels are normal, but for the purpose of this work, it is largely known that residual marine oil is the commonly used type of fuel for vessels, and is made up of 86.4% of carbon per unit weight. Also, the CO 2 /C is known to be 44/12. As a result, CO 2 emissions resulting from residual marine oil combustion can be evaluated with Equation (2) (Chang et al., 2013;NPA, 2017): Substituting Equation (1) into Equation (2) gives: (3) The parameters required for calculating CO 2 emissions based on Equation (3) include: MF k which denotes the fuel used by the main engine daily; AF k which denotes the fuel used by the auxiliary engine daily; S 1k which denotes the operational speed of the vessel (nm/h); S 0k which denotes the design speed of the vessel (nm/h) and d ij which denotes the distance between point i and j.
The data acquired from the NPA database show that a total of 1,275 vessels were processed: Lagos (595) and Tin Can ports (680) from January to June (first and second quarter) of 2017 excluding Navy vessels. This came with other information such as docking time, berth number, nationality, vessel type, exit time, tonnage, cargo amount, etc. as can be seen on the NPA website http://nigerianports.gov.ng.
Some essential data used in this work are not available in the Nigerian Port Authority website. These include; vessel operating and design speed, time and distance traversed at various stages of the vessel's movement, engine power (kW h), engine load factor and fuel consumption rate (g/kW h). The data for time and distance traversed at various stages of the vessel's movement were obtained by tracking the vessels movement in the port by individuals in the pilot organization. The data for the vessel's operating and design speed by vessel type are obtained based on assistance from major shipbuilding websites as well as authorities in ship building research institutes. The data on fuel consumption rate, engine load factor were obtained from Corbett et al. (2009) and Chang & Wang (2012), while the engine power was based on European Environment Agency (2002) and Villalba & Gemechu (2011).

Results and discussion
The results for fuel consumed depending on the category of ship and various movement of the vessel are presented in Table 1 and Figure 3. The result indicates that PMS (premium motor spirit) carriers are the highest consumers of fuel, followed by container ships and general cargo vessels. The curve indicating passing through the lock gates movement and that anchorage movement overlap showing that the vessel CO 2 emission in both stages of movement are similar. This is as a result of the same time and distance covered during these movements. It is also observed that PMS vessels are the highest emitters of CO 2 followed by container vessels and general cargo vessels. Used vehicle vessels are the highest fuel consumers per vessel, followed by general cargo vessels and passenger ships. The error estimate of the CO 2 emitted is presented in Table 2.
In general, the vessel call which is the number of a particular type of vessel processed by a port determines the vessel with the most CO 2 emission. Figure 3 indicates the vessel call for each of the vessel types. This gives the reason why PMS vessels are the highest gross emitters of CO 2 as they have the highest vessel call in these ports. Figure 4 gives the percentage of fuel consumed based on the stage of movement of the vessel. The highest fuel consumption is recorded during anchorage and when passing through the lock gates, with 30% each leading to 60% of the total emission from a particular ship type. The least fuel consumed was during cargo handling at the dock which accounts for about 5% of the total emission from a ship as shown in Figure 4. Therefore, over 5% of the total emission can be curbed by powering the vessel from the national grid during cargo handling and in fact, a better situation can be obtained by using the national grid when the vessel gets to the port vicinity.

Uncertainties
The correctness of this CO 2 emission estimate is dependent on the information utilized and the presumptions made. As stated earlier, basic information regarding the vessels were acquired from NPA website which is a totally dependable source for essential ship data for the two ports in consideration. Experimental values utilized for vessels speeds, and engine powers were utilized as a part of the assessment, which may instigate a specific level of uncertainty. In spite of this, the calculation was performed to be the most illustrative for Lagos and Tin Can ports. To take care of the errors that must have occurred in course of the calculations, a ± 5% of the CO 2 emitted by each of the ship type was carried out and presented in Figure 3 as vertical bars on the value point.

Conclusion and recommendation
The CO 2 emissions at Lagos port and Tin Can port for the first and second quarter of 2017 was 8,167 t. The data obtained covered 6-months (January to June) in 2017. Extrapolation based on the result for the first and second quarter of 2017 indicates that approximately 16,335 t of CO 2 was  produced in 2017. Around 773 t of CO 2 were produced and emitted during anchorage and while passing through lock gates movement, respectively. Also, 644 t of CO 2 was emitted through maneuvering to the dock movement. Consequently, these three movements account for 85% of the total CO 2 emission from Lagos and Tin Can ports. Whereas maneuvering to the lock gates movement shows an emission of 258 t, and 129 t of emissions for the docking stage. As a result, if provisions are made for electricity from land about 5% of the estimated emissions docking handling can be avoided.