Emission reduction through ship routing

Among the four categories of measures to reduce emissions from shipping, operational measures are regarded as more readily available and highly effective. This section takes the ship-routing operational measure to address CO2 emission reduction for container ships, mainly focusing on re-engineering or adjusting the shipping service network. This section is mainly based on Song and Xu (2012b).

A common ship-routing problem in practice is the choice of using a direct-call service or a feeder service to serve a market. We take an Asia- Europe container shipping route and the UK market as an example in which deep-sea ships call at a few Europe-continental ports and one UK port in Northern Europe. Clearly, the service route could be easily adjusted by letting deep-sea ships skip the UK port and use feeder ships to serve the UK market. This gives rise to two alternatives: a direct deep-sea shipping route to serve the UK market, or a deep-sea shipping route plus a feeder shipping route to serve the UK market (See Figure 7.4). From the environmental impact’s perspective, by skipping the UK port and maintaining the overall structure and schedule of the deep-sea service, the ССЬ emission of the deep-sea service

Two alternatives of shipping service structures

Figure 7.4 Two alternatives of shipping service structures.

can be reduced because more sailing time is allowed for the deep-sea ships. On the other hand, a feeder service between the UK port and a Europe- continental port incurs additional CO2 emissions. An interesting question is which alternative is more preferable in different situations. This type of ship route choice can be regarded as an operational measure to reduce CO2 emissions. This section applies the operational activity-based method presented in previous sections to quantitatively evaluate the CO2 emissions of the above two alternatives and to identify their desirability in various scenarios.

Evaluate emissions for an Asia—Europe route directly serving the UK market

The Asia-Europe service route in Figure 7.4 incudes 11 ports in the sequence following BUS (Busan), XIN (Xingang), DAL (Dalian), Q1N (Qingdao),

KWY (Kwangyang), SHA (Shanghai), BRE (Bremerhaven), HAM (Hamburg), ROT (Rotterdam), FEL (Felixstowe), and TJP (Tanjung Pelepas). Nine ships are deployed in this service route to provide a weekly service with a total round-trip journey time of 63 days. The average ship capacity is 6,600 TEU. The maximum sailing speed is 25 knots. The castoff and mooring time is assumed to be three hours for each port. The detailed sailing schedule and port distance (in nautical miles) are given in Table 7.10 (based on Song and Xu 2012b).

The FC for the ship consists of the bunker FC of the main engine at sea and the auxiliary FC at sea and in ports. The total FC for a container ship in a single round-trip is the sum of FCs along the entire trip. The carbon emissions can then be calculated based on the total FC. As all the ships in the same service are statistically similar, we take one ship as an example.

Two factors have a significant impact on shipping service operational activities. The first is the demand volume. The west-borne voyages (from Asia to Europe) have high load factors, whereas the east-borne voyages (from Europe to Asia) have much lower load factors. In particular, the demand volume that flows into and out of the UK would affect the carbon emission performance of the two alternatives. Therefore, we experiment a set of scenarios with different demand volumes into the UK varying from 1,050 to 1,400 TEU. Considering all the laden container movements, the load factor (for laden containers on board) for the dominant leg from Asia to Europe in the west-borne voyage is in the range of [0.8591, 0.9121], while for the longest leg from Europe to Asia in the east-borne voyage, the load factor is 0.5250. The empty containers are repositioned using the CRP by balancing the container flow-in and flow-out for each port among all ports in the shipping route (Song and Dong 2011).

The second factor that has a significant impact on shipping service activities is the container handling rate at ports or terminals. Different ports (even different berths at the same port) may have different container handling rates

Table 7.10 Schedule and distance of an Asia-Europe service route (based on Song and Xu 2012b)

Port

Transit time (tlays)

Distance (nautical miles)

Busan

0

639

Xingang

2

187

Dalian

3

238

Qingdao

4

388

Kwangyang

6

383

Shanghai

8

10,608

Bremerhaven

30

117

Hamburg

32

305

Rotterdam

34

118

Felixstowe

36

8,212

Tanjung Pelepas

57

2,504

Busan

63

639

due to reasons such as the number of gantry cranes used to serve a container ship simultaneously may differ; the efficiency of the quay cranes and the mixture of 20-foot boxes and 40-foot boxes may vary. Based on the data in the literature, we create a base scenario as a reference point in which the Asian ports’ handling rates are 180 TEU per hour, and the North European ports’ handling rates are 210 TEU per hour. It is assumed that the electricity consumption of handling containers at quayside is proportional to the number of containers handled. In other words, as long as the total number of containers (including both laden and empty) to be handled at the port does not change, the electricity consumption will remain the same. This implies that the handling rate changes will not affect the electricity consumption. This assumption is reasonable if we regard the handling rate changes are caused by adding or removing quay cranes.

By applying the operational activity-based method, we can obtain the ССЬ emissions (in tonnes) and the Cl (in grams per TEU*km) for a single ship in a round-trip with different scenarios (i.e., the different combinations of the level of handling rate and the demand on Felixstowe) in Table 7.11. Here, the port handling rate takes three levels, i.e., the base scenario and ±40% from the base scenario.

From Table 7.11, it can be observed that as the demand in the UK market (via Felixstowe port) increases, the ССЬ emissions (in tonnes) and the Cl are increasing; on the other hand, as the port handing rate increases, the ССЬ emissions and the Cl are decreasing. This is in line with the intuition because more demands or lower handling rates require longer port times to handle the containers, which in turn reduces ship’s sailing time at sea and therefore

Table 7.11 ССЬ (tonnes) and Cl (g/TEU*km) for the first alternative with different scenarios

Handling rate level (%)

Demand to FEL (TEU)

CO2 (tonnes)

Cl (g/TEU*km)

1,050

18,089

90.52

1,120

18,730

93.05

-40

1,190

19,391

95.65

1,260

20,073

98.31

1,330

20,776

101.04

1,400

21,501

103.84

1,050

16,860

84.37

1,120

17,427

86.58

0

1,190

18,009

88.83

1,260

18,609

91.14

1,330

19,225

93.50

1,400

19,859

95.91

1,050

16,411

82.12

1,120

16,949

84.20

40

1,190

17,502

86.33

1,260

18,070

88.50

1,330

18,653

90.72

1,400

19,252

92.98

requires higher sailing speed and consumes more fuels. Another point is that the impact of port handling rate on the ship’s Cl is disproportional. For example, improving port handling rate from the —40% level to the base level can reduce the Cl much more significantly than from the base level to the +40% level.

 
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