at SciVerse ScienceDirect

Environmental Pollution 165 (2012) 1e10

Contents lists available

Environmental Pollution

journal homepage: www.elsevier .com/locate/envpol

The growth pattern and fuel life cycle analysis of the electricityconsumption of Hong Kong

W.M. To a,*, T.M. Lai a, W.C. Lo b, K.H. Lam c, W.L. Chung d

aMacao Polytechnic Institute, Rua de Luis Gonzaga Gomes, Macao SAR, People’s Republic of ChinabHong Kong Polytechnic University, Hung Hom, Kowlonn, Hong Kong SAR, People’s Republic of Chinac The University of Hong Kong, Pokfulam, Hong Kong SAR, People’s Republic of Chinad EDMS (Hong Kong) Limited, Central, Hong Kong SAR, People’s Republic of China

a r t i c l e i n f o

Article history:Received 19 October 2011Received in revised form11 January 2012Accepted 8 February 2012

Keywords:Electricity consumptionGrowth patternPollutant emissionsFuel life cycle analysis

* Corresponding author.E-mail addresses: wmto@ipm.edu.mo (W.M. To),

eewclo@polyu.edu.hk (W.C. Lo), khlam@eee.hku.hk (K(W.L. Chung).

0269-7491/$ e see front matter � 2012 Elsevier Ltd.doi:10.1016/j.envpol.2012.02.007

a b s t r a c t

As the consumption of electricity increases, air pollutants from power generation increase. In metro-politans such as Hong Kong and other Asian cities, the surge of electricity consumption has beenphenomenal over the past decades. This paper presents a historical review about electricity consump-tion, population, and change in economic structure in Hong Kong. It is hypothesized that the growth ofelectricity consumption and change in gross domestic product can be modeled by 4-parameter logisticfunctions. The accuracy of the functions was assessed by Pearson’s correlation coefficient, mean absolutepercent error, and root mean squared percent error. The paper also applies the life cycle approach todetermine carbon dioxide, methane, nitrous oxide, sulfur dioxide, and nitrogen oxide emissions for theelectricity consumption of Hong Kong. Monte Carlo simulations were applied to determine the confi-dence intervals of pollutant emissions. The implications of importing more nuclear power are discussed.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

In built environments such as Hong Kong and other Asian cities,electricity consumption has increased rapidly since the 1970s. Thegrowth of electricity consumption is partly attributed to populationgrowth, economic growth, change in life style, and the expansion ofthe services sector. According to the Hong Kong Census and StatisticsDepartment, Hong Kong’s electricity consumption increased from4451 million kWh in 1970 to 41,862 million kWh in 2010 (Censtatd,2011a). Hong Kong’s population increased from 4.00 millions in1970 to 7.10 millions in 2010 (Censtatd, 2011b), total gross domesticproduct (GDP) from US$ 22.6 billion in 1970 to US$ 223.9 billion in2010 (both figures chained to 2009), and contribution of the servicessector to the total GDP from 62 percent in 1970 to over 92 percent in2010. Nowadays, Hong Kong’s per capita electricity consumption andelectricity productivity are 5898 kWh/year and US$ 5.35 per kWh/year e one of the highest electricity productivity in the world,respectively. Nevertheless, the surge of electricity consumption alsoleads to rapid increase in pollutant emissions. The discharge ofgreenhouse gases including carbon dioxide, methane and nitrous

tmlai@ipm.edu.mo (T.M. Lai),.H. Lam), andy@edmshk.com

All rights reserved.

oxide, and other gaseous pollutants such as sulfur dioxide, andnitrogen oxides will not only contribute to the global climate change(IPCC, 2007), but also causes adverse effects onhumanhealth (Kampaand Castanas, 2008; Markandya et al., 2009; Wong et al., 2002).Combining with a high level of particulate matters, aerosols, andother organic matters discharged from various sources, the numberof haze days inmany Asian cities has increased rapidly in the past tenyears, especially inwinter months between October andMarch (Lamand Lau, 2005). The number of severe respiratory and cardiovasculardiseases was also found to be strongly associated with the concen-trations of sulfur dioxide and nitrogen oxides in Hong Kong (Wonget al., 2002). For these reasons, this paper explores the growthpatterns of electricity consumption, population, and GDP in HongKong. We also apply the life cycle approach (To et al., 2011) todetermine the environmental impact of the electricity consumptionof Hong Kong.

2. Literature review

2.1. Electricity consumption, population, and economic growth

The relationships between electricity consumption, population,and economic growth have been the focus of intense research overthe past fifty years. Foss (1963) showed that electricity consump-tion was strongly associated with the utilization of capital

W.M. To et al. / Environmental Pollution 165 (2012) 1e102

equipment, in turn affected economic growth in an industrialcountry such as the United States. Headthfield (1972) followedFoss’s idea to measure capital usage using electricity consumptiondata in the United Kingdom. Costello (1993) performed a cross-country, cross-industry comparison of productivity growth andsuggested that electricity consumption, as a measure of capitalusage, was strongly associated with productivity/economic growth.Ehrlich and Holdren (1971) published their article “Impact ofPopulation Growth” in Science. They reported that there was 760percent increase in electricity consumption from 1940 to 1969 andsuggested that this increase was partly contributed to increase inpopulation and electrification of the society. Brown and Koomey(2003) and Lai et al. (2008) found that population growth partlycontributed to the growth of electricity consumption in Californiaand Macao, respectively. In Hong Kong, Lam (1998), Lam et al.(2008), and Yan (1998) investigated the effect of climate on resi-dential and commercial electricity consumption. They showed thatelectricity consumption increased rapidly during the summermonths and concluded that air conditioning consumed more than50 percent of the total amount of electricity consumption in theresidential and commercial sectors. Other researchers approachedthe associations between electricity consumption, GDP, and/orpopulation using econometric modeling (Chontanawa et al., 2008;Kraft and Kraft, 1978; Lai et al., 2011; Lee, 2005; Meherara, 2007;Sharma, 2010; Soytas and Sari, 2003; Yoo, 2006). Many of themreported that the long-run and short-run causal relationships fromelectricity consumption to GDP exist in most developing countriesand cities (Chontanawa et al., 2008; Lai et al., 2011; Soytas and Sari,2003). However, there were mixed causal relationships in manyother countries (Sharma, 2010). In fact, none of the extant literaturehas examined the fuel life cycle impact of electricity consumptionon the environment in Hong Kong.

2.2. Life cycle approach

According to the US EPA (2006), life cycle analysis is a techniquefor identifying significant environmental aspects of a product,process and (or) service and evaluating the associated impacts on theenvironment. It consists of four major stages; (i) defining the goalsand scopes of the study, (ii) compiling an inventory of energy andmaterial inputs and pollutant emissions; (iii) assessing the impactsassociated with the identified inputs and emissions on naturalresources, ecosystem and human health; and (iv) interpreting theanalyzed results that helpmanagement/policy-makers in a decision-making process. A comprehensive life cycle analysis is normallya “forward” approach in which an analyst uses a multi-layer

Fig. 1. Hong Kong’s electricity con

procedure to identify and determine direct and indirect use ofresources and pollutant emissions along raw materials extractionand processing, components production, production of a product/service, and consumption and disposal of a product/service.However, as the number of layers increases, uncertainties increase(Ney and Schnoor, 2002). Recently, To et al. (2011) propose the lifecycle approach to analyze greenhouse gases emissions due to theelectricity consumption of Macao. By realizing that Macao, as mostother cities, does not have primary energy sources, To et al. (2011)traced backward to locate the sources of primary energy anddetermined the direct emissions due to the fossil fuel extraction,processing, transportation, and combustion. They demonstrated thatgreenhouse gases emissions could be underestimated by(i) neglecting the emissions from the extraction, transportation, andrefining of fuels, and (ii) not taking the imported electricity intoconsideration. Extending To et al.’s (2011) approach, this studyfocused on emissions of greenhouse gases and other pollutants dueto the electricity consumption of Hong Kong. We determined thedirect emission of air pollutants from the extraction, processing,transportation, refining, storage, and combustion of fuels.

3. Data sources

Data of electricity consumption, population, the total GDP forthe period of 1970e2010 were gathered from the Hong KongCensus and Statistics Department (Censtatd, 2011a, 2011b). Fueldata were also gathered from the Department (Censtatd, 2011a),and the environmental or sustainability reports of power compa-nies in Hong Kong and Shenzhen.

4. Results and discussions

4.1. Growth patterns of electricity consumption, population,and GDP

Hong Kong is a services center in Asia and an internationalfinance center that had the largest total funds raised through newinitial public offerings in 2010. It, as a former British colony, used tobe a major manufacturing center for light industrial goods in the1960s and 1970s because of its low labor cost. Hong Kong trans-formed to a commercial and trading center in the 1980s whenmanufacturers started moving their labor-intensive operations tomainland China. Over the past two decades, Hong Kong has trans-formed itself as an international finance center, emphasizing itsstrong link between East andWest and a gateway tomainland China.In the past couple of years, Hong Kong has benefited significantly

sumption from 1970 to 2010.

y = 0.0782x -149.94R2 = 0.9792

0

1

2

3

4

5

6

7

8

1970 1975 1980 1985 1990 1995 2000 2005 2010

Population

Pop

ulat

ion

in m

illio

ns

Fig. 2. Hong Kong’s population from 1970 to 2010.

W.M. To et al. / Environmental Pollution 165 (2012) 1e10 3

from the Individual Visit Scheme and its Close Economic PartnershipArrangement with mainland China. Under the Individual VisitScheme, 0.27 billion residents in 49 Mainland cities are allowed tovisit Hong Kong in their individual capacity. In 2010, Hong Kongattracted over 36 million visitors and most of them were short stayvisitors from mainland China. Electricity consumption grew by anorder of magnitude between 1970 and 2010. More specifically, thecommercial electricity consumption increased by 19 times between1970 and 2010. Fig. 1 shows Hong Kong’s electricity consumptionfrom 1970 to 2010.

The growth of electricity consumption resembled a typicallogistic curve. To et al. (2011) and Cho et al. (2007) demonstratedthat the logistic growth model had explanatory power in modelingelectricity consumption and predictive power for energy demandsin short-term. Hence, a 4-parameter logistic functionwas applied tothe data set. The resulting formula is:

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

4 4.5 5 5.5 6 6.5 7 7.5

Population in millions

Ele

ctric

ity c

onsu

mpt

ion

in m

illio

n kW

h

Fig. 3. Hong Kong’s total electricity consumption vs. population.

½Electricity consumption�year ¼ 2000þ 428001þ expð0:138� ð1990� yearÞÞ million kWh (1)

The value of R2 of Eq. (1) was 0.999. R2 is the coefficient ofdetermination, a measure of the proportion of the variation in onevariable that is explained by the variation in another variable. Thepredicted values of Hong Kong’s electricity consumption are alsoshown in Fig. 1. The accuracy of this 4-parameter logistic functionwas also assessed by using scale invariant measures - mean abso-lute percent error (MAPE) and root mean squared percent error(RMSPE). The calculated MAPE and RMSPE were 1.59 percent and2.09 percent respectively, representing a highly accurate prediction(Witt and Witt, 1992).

Fig. 2 presents Hong Kong’s population from 1970 to 2010. Itshows that population increased quite linearly between 1970 and2010 and R2, MAPE and RMSPE between the fitted linear curve andthe actual data were 0.979, 2.37 percent and 2.18 percent, respec-tively. By plotting electricity consumption as a function of pop-ulation, Fig. 3 shows the nonlinear relationship between them. Asin the other cities (Brown and Koomey, 2003; Lai et al., 2008), theincrease in Hong Kong’s total electricity consumption was partlydue to population growth, but more importantly due to changes ineconomic structure over the past forty years. Details of thesechanges were described earlier.

Fig. 4 shows Hong Kong’s total GDP from 1970 to 2010. Again,a 4-parameter logistic growth function could be employed torepresent the economic growth of Hong Kong.

The function of economic growth is given as:

½TotalGDP�year ¼ 10000

þ 1900001þexpð0:138�ð1999�yearÞÞ million US$

(2)

The value of R2 of Eq (2) was 0.965. However, if only the data setbefore 1997 were considered, the R2 value was 0.997. The change inR2 value between the data sets 1970e2010 and 1970e1997 can beunderstood because Hong Kong has gone through two criticalchanges in the past fourteen years. The first one was the Asianfinancial turmoil in 1997 in which Hong Kong’s economic was

slowed down drastically. The second one was the Severe AcuteRespiratory Syndrome (SARS) outbreak in 2003. And fortunately,Hong Kong has benefited greatly from the Individual Visit Schemeand Close Economic Partnership Arrangement withmainland China

0

50000

100000

150000

200000

250000

1970 1975 1980 1985 1990 1995 2000 2005 2010

Tota

l GD

P in

mill

ion

US

$

Actual

Predicted using Eq.(2)

Predicted using Eq.(3)

Fig. 4. Hong Kong’s total GDP from 1970 to 2010.

y = 0.2499x - 1908.7R2 = 0.9921

y = 0.0491x + 30759R2 = 0.9454

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

0 50000 100000 150000 200000 250000

Total GDP in million US$

Tota

l ele

ctric

ity c

onsu

mpt

ion

in m

illio

n kW

h

Fig. 5. Total electricity consumption vs. total GDP between 1970 and 2010.

W.M. To et al. / Environmental Pollution 165 (2012) 1e104

since then. The predicted values of Hong Kong’s total GDP are alsoshown in Fig. 4. It should be noted that a discontinuous4-parameter logistic function could be employed to model HongKong’s GDP closely; one (as given in Eq. (2)) for the period1970e1997, and another one for the period 1998e2010. The generalform of the logistic function is:

½Total GDP�t ¼ GDPintial þDGDP

1þ expðs� ðtmid � tÞÞ million US$

(3)

where GDPinitial is the base level of GDP,DGDP the eventual increasein GDP, s time constant, and tmid the year of the highest growth rate.These values were 10,000, 190,000, 0.138, and 1990 for t ¼ 1970,1971,..., 1997, and 125,000, 105,000, 0.5, and 2004 for t ¼ 1998,1999,..., 2010, respectively. The R2, MAPE, RMSPE of the discontin-uous 4-parameter logistic function were 0.997, 3.19 percent, and4.56 percent for the former period and 0.977, 1.07 percent, and 2.31percent for the later period respectively. Again, the functionproduced highly accurate predictions as shown in Fig. 4.

In fact, the total electricity consumption was significantly corre-lated to the total GDP (R2¼ 0.962, p< 0.001). The plot of Hong Kong’stotal electricity consumption vs. total GDP is shown in Fig. 5.

Fig. 5 indicates that there was piece-wise linear relationshipbetween electricity consumption and GDP. In the first period, i.e.1970e2002, electricity consumption increased by about 2.5 millionkWh when the total GDP increased by US$ 10 million. During therecent period, i.e. 2003e2010, electricity consumption increased byabout 0.5 million kWh when the total GDP increased by US$10 million. It is because the finance and service sector that hasexpanded rapidly since 2003 does not consume electricity as muchas the manufacturing or logistics industry per unit of GDP gain.Hence, the preferential treatment from mainland China greatlyboosts the energy effectiveness of Hong Kong.

As Hong Kong’s population was 7.10 million in 2010, per capitaelectricity consumption was 5898 kWh. Hong Kong’s electricityproductivity was US$ 5.35 GDP per kWh. Moreover, Hong Kong’selectricity consumption is going to increase bymore than 300millionkWh each year in the near future. How much more gaseous pollut-ants will be generated?

4.2. Fuel life cycle analysis

Table 1 shows the fuel consumed to generate electricity in HongKong for the period of 2002e2010 (no datawere available fromHongKong Electric before 2002). In 2010, the majority of electricity

generated was made by burning coal (66.4 percent), supplementedby burning natural gas (33.2 percent) and oil (0.4 percent).

Fig. 6 shows the fuel life cycle for the electricity consumption ofHong Kong. This figure indicates the operating greenhouse gases andother air pollutants emitted along the paths of fuel life cycle.Specifically, Hong Kong’s power companies imported fuels fromIndonesia (for 90 percent coal), Australia (for natural gas viaShenzhen LNG terminal for Hong Kong Electric (HKE) only and for4.3 percent coal), China (for natural gas fromHainan province for CLPonly and 3.8 percent coal), and theMiddle East (for heavy fuel oil andlight gas oil via oil refineries in Singapore) in 2010. Fig. 7 shows thetransportation routes of those fuels.

4.2.1. Emissions of gaseous pollutants for the “Mine/well-to-electricity” process

The fossil fuel extraction (or production), transportation, refiningand combustion generate carbon dioxide (CO2), methane (CH4),nitrous oxide (N2O), nitrogen oxides (NOx), and sulfur dioxide (SO2).Their amounts are dependent on the extraction method, productionmethod, transport mode, refinery process, storage mode, thecombustion efficiency, and flue gases treatment. To et al. (2011)suggest that each fuel can be analyzed individually and an emis-sion table can be compiled (see Table 2). Table 2 shows that theemission factors of different fuels are very different. For example, the

Table 1Fuel consumption for generating electricity in Hong Kong for the period 2000e2010.

Year Hong Konga,b China

Hong Kong Electric CLP power Nuclear plant

Coal � 103

tonneLight gasoil � 103

tonne

Heavy fueloil � 103

tonne

LNG � 103

tonneCoal � 103

tonneLight gasoil � 103

tonne

LNG � 103 tonne Imported electricity � 106

(kWh)Exported electricity � 106

(kWh)

2000 2821 29 1712 10,203 11812001 3115 30 1754 10,355 15812002 4136 8 6 0 3812 32 1708 10,182 21752003 4168 6 5 0 5813 39 1091 10,397 30082004 4242 5 5 0 5053 47 1577 9837 30872005 4327 5 5 0 5490 28 1576 11,001 44982006 4088 5 6 98 5638 26 1571 10,897 45282007 3646 5 4 279 6803 20 1168 10,959 40352008 3747 5 6 260 5817 24 1424 11,297 35532009 3583 16 8 316 6430 21 1294 11,590 37312010 3055 5 6 576 5615 20 1526 11,046 2609

a Hong Kong Electric and CLP Power provided information about fuels consumed in TJ in their sustainability reports and facility performance statistics.b The amounts of coal, light gas oil, heavy fuel oil, and liquefied natural gas (LNG) consumed were converted from TJ to kT based on the calorific values of 26.4 GJ/T for coal,

43 GJ/T for light gas oil, 40.4 GJ/T for heavy fuel oil, and 54.4 GJ/T for LNG, respectively (based on IPCC Guidelines and HK government and power companies’ energy statistics).

W.M. To et al. / Environmental Pollution 165 (2012) 1e10 5

Intergovernmental Panel on Climate Change (IPCC, 2010) indicatesthat emission factors of coal, liquefied natural gas, heavy fuel oil, andlight gas oil are 94600 kg CO2/TJ, 64200 kg CO2/TJ, 77400 kg CO2/TJ,and 74100 kg CO2/TJ while Sovacool (2008) found that the mining,processing and transportation of nuclear fuels would emit0.58e118 g (mean: 25.09 g) CO2-equivalent/kWh while the

Fig. 6. Fuel life cycle of the electrici

operation of a nuclear plant would produce 0.1e40 g (mean: 11.58 g)CO2-equivalent/kWh.

According to the Intergovernmental Panel on Climate Change(IPCC, 2007), CO2, CH4, and N2O are greenhouse gases that havea profound effect on global warming. The global warming potentials(GWP) of CH4 and N2O relative to CO2 are 25 and 298, respectively.

ty consumption of Hong Kong.

Fig. 7. Transportation routes of fuels used in Hong Kong.

W.M. To et al. / Environmental Pollution 165 (2012) 1e106

Based on the information provided in Table 2 and the GWPs ofCO2, CH4, and N2O, pollutant emissions due to the electricityconsumption of Hong Kong in 2010 were determined (see Table 3).Table 3 shows that 29.09 million tonnes of CO2, 576 tonnes of CH4,and 413 tonnes of N2Owere generated in Hong Kong’s power plantsin 2010. By converting CH4 and N2O to CO2-equivalent using GWP,greenhouse gas emissions amounted to 29.23 million tonnes ofCO2-equivalent in Hong Kong power plants. Table 4 shows that17770 tonnes of SO2 and 27010 tonnes of NOx were generated inHong Kong’s power plants in the same year. In addition, there were210 kilotonnes of CO2, 4679 tonnes of SO2, and 5936 tonnes of NOxfor fuel transport, and 384 kilotonnes of CO2-equivalent, 108 tonnesof SO2, and 109 tonnes of NOx for the extraction and processing offuels. Hence, the fuel life cycle for Hong Kong’s power plantsproduced 29.82 million tonnes CO2-equivalent greenhouse gases,22557 tonnes of SO2, and 33055 tonnes of NOx. As the plantsgenerated 38292 million kWh in 2010, emission factors due to theelectricity generated locally was 778.8 g CO2-equivalent/kWh,0.589 g SO2/kWh, 0.862 g NOx/kWh using the life cycle approach.However, Hong Kong imported 11046 million kWh of electricity, 26percent of the electricity consumed in 2010, from the Daya BayNuclear Power Plant located in Shenzhen. Sovacool (2008) exam-ined 103 life cycle studies of greenhouse gas emissions for nuclearpower plants and found that 19 studies were the most up-to-dateand transparent according to their methodologies and data sour-ces. He concluded that the emissions for nuclear energy over thelifetime of a power plant should range from 14 to 288 g CO2-equivalent/kWh. Specifically, Sovacool (2008) found that themining, processing and transportation of nuclear fuels would emit0.58e118 g (mean: 25.09 g) CO2-equivalent/kWh while the oper-ation of a nuclear plant would produce 0.1e40 g (mean: 11.58 g)CO2-equivalent/kWh. By taking the net imported electricity with

36.67 g CO2-equivalent greenhouse gases emissions per kWh,emission factors due to the electricity consumption of Hong Kongwould be 722.1 g CO2-equivalent/kWh, 0.539 g SO2/kWh, and0.790 g NOx/kWh.

4.2.2. Sensitivity analysis of emissions using Monte Carlosimulations

As shown in Section 4.2.1, the amounts of greenhouse gases, SO2,and NOx generated due to the extraction, production, and pro-cessing of a fuel depend on the geographical location of the mine,mining method, and processing techniques. Besides, the IPCC(2010) suggests that the 95 percent confidence intervals of CO2emission for coal, LNG, heavy oil, and light gas oil are [87,300,101,000], [58,300, 70,400], [75,500, 78,800], and [72,600, 74,800]kg per TJ respectively. The 95 percent confidence intervals of CH4and N2O emissions for coal are [0.3, 3] and [0.5, 5] kg per TJrespectively while the 95 percent confidence intervals of CH4 andN2O for LNG, heavy oil, or light gas oil are [1, 10] and [02, 2] kg per TJrespectively. The values of CO2, CH4 and N2O emissions for coal,LNG, heavy oil, and light gas oil follow lognormal distributions [27].In order to assess the impact on the overall emissions, Monte Carlosimulations were performed 1000 times, using lognormal distri-butions for pollutant emissions due to fuel combustion and uniformdistributions for the others. The results showed that emissionfactors due to the electricity generated locally was 776 g CO2-equivalent/kWh with the 95 percent confidence interval of [735,820], 0.589 g SO2/kWh with the 95 percent confidence interval of[0.587, 0.591], 0.863 g NOx/kWh with the 95 percent confidenceinterval of [0.861, 0.866].

On the other hand, by taking the net imported electricity, emis-sion factors due to the electricity consumption of Hong Kong wouldbe 720 g CO2-equivalent/kWh with the 95 percent confidence

Table 2Emission factors of coal, liquefied natural gas, and oil products.

Fuel Type Processes Description Emission Factors Reference

Coal Extraction Surface mining and coal processing in Indonesia. i. Mining: 0.3e2.0 m3 CH4/tonne IPCC (2010)ii. Processing: 0e0.2 m3 CH4/tonne

Transport From PT Indonesia Bulk Terminal at Pulau Lautto Hong Kong by Post-Panamax type bulk carriers.Distance: 4000 km

i. 4.92 g CO2/tonne-km Psaraftis and Kontovas (2009)ii. 0.11 g SO2/tonne-kmiii. 0.14 g NOx/tonne-km

Combustion Burnt in Hong Kong’s power plants withdesulfurization and selective catalyticreduction systems.

i. 94,600 kg CO2/TJ IPCC (2010); Hong Kong’spower companies and Censusand Statistics Dept.

ii. 1 kg CH4/TJiii. 1.5 kg N2O/TJiv. SO2 and NOx emissions

were provided by powercompanies in terms of kT/year.Net calorific value: 26.4 kJ/kT.

LiquefiedNaturalGas (LNG)

Extraction inAustralia

Venting of CO2, flaring and processing ofnatural gas (NG) to LNG at North WestShelf Gas in Australia.

i. 70 kg CO2/tonne Australian GreenhouseOffice (1998)ii. 0.68e0.76 kg CH4/tonne

Transport fromAustralia

From North West Shelf in Australia toGuangdong LNG Terminal at Shenzhen by LNGcarriers (for HK Electric) Distance: 5140 km

i. 12.72 g CO2/tonne-km Psaraftis and Kontovas (2009)ii. 0.28 g SO2/tonne-kmiii. 0.35 g NOx/tonne-km

Extraction andtransmissionin Hainan,China

Provision of LNG from the Yacheng Gas Fieldto Hong Kong’s CLP Power using subsea pipeline.Distance: 780 km

i. 2000 m3 CH4/km/yr IPCC (2010)

Combustion Burnt in Hong Kong’s power plants. i. 64,200 kg CO2/TJ IPCC (2010); HK Electric’ssustainability reports.ii. 3 kg CH4/TJ

iii. 0.6 kg N2O/TJNet calorific value: 54.4 kJ/kT.

Oil Extraction in theMiddle East

Flaring, venting and processing of oilin the Middle East.

i. 13.6e19.5 kg CO2E/bbl ofcrude oil; 1 barrel ofoil ¼ 138.8 kg

US DOE (2009); Al-Hamadand Khan (2008)

ii. 0.51 kg SO2/tonne of crude oiliii. 0.02 kg NOx/tonne of crude oil

Transport Crude oil is transported to Singapore forrefining. Heavy fuel oil (HFO) and light gas oil(LGO) are transported from Singapore to Hong Kongby Aframax oil tankers. Distances- Middle East /Singapore: 6870 km; Singapore / Hong Kong:2710 km

i. 5.63 g CO2/tonne-km Psaraftis and Kontovas (2009)ii. 0.12 g SO2/tonne-kmiii. 0.15 g NOx/tonne-km

Refining Crude oil is processed in refineries in Singapore. i. 17 kg CO2/tonne of HFO Babusiaux and Pierru (2007);EC (2003)ii. 27 kg CO2/tonne of LGO

iii. 0.03e6 kg SO2//tonne of oiliv. 0.06e0.7 kg NOx/tonne of oil

Combustion Burnt in Hong Kong’s power plants. i. 77,400 kg CO2/TJ of HFO IPCC (2010); Hong Kong’spower companies andCensus and Statistics Dept.

ii. 74,100 kg CO2/TJ of LGOiii. 3 kg CH4/TJiv. 0.6 kg N2O/TJ

Net calorific value: 40.4 kJ/kT of HFO.Net calorific value:43.0 kJ/kT of LGO.

Nuclear Mining, processing,and transport

Nuclear fuel is processed in France and transportedto Shenzhen’s Daya Bay Nuclear Power Station.

i. 0.58e118 g (mean: 25.09 g)CO2E/kWh

Sovacool (2008)

Operation of anuclear power

Pressurized water reactors are operated in Shenzhen. i. 0.1e40 g (mean: 11.58 g)CO2E/kWh

Sovacool (2008)

Table 3Greenhouse gases emissions due to the electricity consumption of Hong Kong in 2010.

Fuel Type Used ina kT Combustion Transport Extraction and Processing

CO2 (tonne) CH4 (tonne) N2O (tonne) CO2 (tonne) CO2/CO2E (tonne) CH4 (tonne)

Hong Kong Coal HKE & CLP 8669 21,651,347 228.9 343.3 169,921 7770Heavy fuel oil HKE 6 18,762 0.7 0.1 324 802Light gas oil HKE & CLP 25 78,472 3.2 0.6 1328 3537Natural gas (China) CLP 1526 5,329,049 249.0 49.8 1560 106,810 1099Natural gas (Australia) HKE 576 2,012,798 94.1 18.8 37,688 40,342 415Overall CO2E 29,227,812 210,821 383,580

Shenzhen Nuclearb 127,911 277,140Overall CO2E 127,911 277,140

a HKE and CLP stand for “Hong Kong Electric” and “CLP Power”, respectively.b Sovacool (2008) indicates that nuclear power emits 25.09 g CO2-equivalent kWh due to the mining, processing, and transportation of nuclear fuel and 11.58 g CO2-

equivalent kWh due to the operation of a nuclear power plant including cooling and fuel cycles, backup generators, and during outages and shutdowns.

W.M. To et al. / Environmental Pollution 165 (2012) 1e10 7

Table 4SO2 and NOx emissions due to the electricity consumption of Hong Kong in 2010.

Fuel Type Used in kT Combustion Transport Extraction and Processing

SO2 (tonne) NOx (tonne) SO2 (tonne) NOx (tonne) SO2 (tonne) NOx (tonne)

Hong Kong Coal HKE & CLP 8669 3814.5 4854.9 e e

Heavy fuel oil HKE 6 6.9 8.6 21.2 21.3Light gas oil HKE & CLP 25 28.3 35.4 86.8 87.4Natural gas (China) CLP 1526 e e e e

Natural gas (Australia) HKE 576 829.6 1037.0 e e

Overall emissions 17,770 27,010 4679.3 5935.9 108.0 108.7Shenzhen Nuclear e e e e e e

Overall emissions e e e e e e

W.M. To et al. / Environmental Pollution 165 (2012) 1e108

interval of [678, 770], 0.539 g SO2/kWh with the 95 percent confi-dence interval of [0.537, 0.541], and 0.790 g NOx/kWh with the95 percent confidence interval of [788, 792].

4.2.3. Effect of fuel mix on emissions of air pollutantsThe fuel life cycle approach was then applied to determine

emissions of air pollutants from 2002 to 2009, the period inwhichthe amount of fuels consumed and the total electricity generatedlocally were known (see Table 1). Fig. 8 shows that greenhousegases emission ranged from 774.6 to 832.6 g CO2-equivalent/kWhbetween 2002 and 2010. It also shows that SO2 emission peaked at2.493 g/kWh in 2003 and then dropped to 0.589 g/kWh in 2010while NOx emission peaked at 1.708 g/kWh in 2003 and thendropped to 0.863 g/kWh in 2010. Fig. 9 shows the energy mix inHong Kong’s power industry during the period 2002 to 2010. Byperforming a covariance analysis between the coal consumed in

0

100

200

300

400

500

600

700

800

900

1000

2002 2003 2004 2005 2006 2007

CO

2-eq

uiva

lent

em

issi

on in

g/k

Wh

Year

Notes: 1. In 2002, the energy mix of Hong Kong’s power industry (local)

The ratios of energy mix were 51.6 : 47.7 : 0.7 for CLP

2. CLP changed the energy mix, i.e. its primary energy from LNG

3. CLP started burning ultra low sulfur coal.

4. HKE changed its energy mix with 4.7% of primary energy from

5. HKE increased the use of LNG, i.e. its primary energy from LN

6. CLP changed the energy mix, i.e. its primary energy from LNG

7. HKE increased the use of LNG, i.e. its primary energy from LN

1

2

3

4

5

6

Fig. 8. . Emission factors due to th

percentage and air pollutants discharged, it was found thatgreenhouse gases emission was strongly and positively associatedwith the coal consumed in percentage (R2 ¼ 0.913, p < 0.001).Results of the covariance analysis also indicated that NOx emissionwas strongly and significantly associated with the coal consumed(R2¼ 0.646, p< 0.01) and SO2 emissionwas moderately associatedwith the coal consumed (R2 ¼ 0.406, p ¼ 0.07). Nevertheless, itshould be noted that SO2 emission was affected by changing fuelmix, sources of fuels, and improvement works in power plants.The footnote of Fig. 8 listed out CLP and HKE implementinga number of strategies as well as improvement works from 2002to 2010 so that SO2 varied more considerably then other airpollutants.

In sum, emissions of air pollutants decreased when thepercentage of coal in the fuel mix decreased, i.e. the percentage ofliquefied natural gas increased.

2008 2009 20100.0

0.5

1.0

1.5

2.0

2.5

3.0

SO

2/N

Ox

emis

sion

in g

/kW

h

CO2-eq emission

SO2 emission

NOx emission

was 68.9 : 30.5 : 0.6 (coal : LNG : oil)

and 99.5 : 0: 0.5 for HKE (coal : LNG : oil)

decreasing from 47.7 % to 27.7 %.

LNG. CLP optimized boiler performance.

G increasing to 13.6 %.

increasing to 33.4 % in 2008 (from 22.6% in 2007).

G increasing to 27.9 %. CLP implemented emission control projects.

7

e electricity generated locally.

0

10

20

30

40

50

60

70

80

90

2002 2003 2004 2005 2006 2007 2008 2009 2010

Year

Prim

ary

ener

gy in

per

cent

age

CoalLNGOil

Fig. 9. Energy mix of Hong Kong’s local electricity generation.

W.M. To et al. / Environmental Pollution 165 (2012) 1e10 9

5. Conclusion and implications

The consumption of electricity has increased rapidly worldwidein the past decades. In Hong Kong, electricity consumptionincreased by 9.4 times from 4451 million kWh in 1970e41,862million kWh in 2010. Hong Kong’s electricity productivity wasUS$5.35 GDP per kWh in 2010. Unfortunately, high electricityproductivity comes at an environmental cost. By analyzing thedata of electricity consumption, population, and GDP in HongKong spanning over the past forty years, it was found that thegrowth of electricity consumption resembled a logistic growthcurve closely, population increased quite linearly, and increase inGDP could be modeled accurately using a discontinuous logisticfunction. The pair-wise comparisons indicated that the growth ofelectricity consumption was partly contributed by the increase ofpopulation, and the growth of electricity consumption and changein GDP were strongly associated. In fact, the later pair was char-acterized very accurately by a piece-wise linear relationship witha turning point in 2003 e the year Hong Kong’s economic to bebadly hit by the SARS epidemic but fortunately then fully supportedby the Central Government for its preferential policy on thedevelopment of the finance and tourism sectors.

Using a holistic view of fuel life cycle analysis, we found that theemission factors due to the electricity generated in Hong Kong was778.8 gCO2-equivalent/kWh, 0.589g SO2/kWh, and0.863gNOx/kWhin 2010. However, Hong Kong imported electricity from a nuclearpowerplant in Shenzhenwith relatively lowCO2-equivalent emissionat 36.67 g CO2-equivalent/kWh. By taking account of the importedelectricity and the associated greenhouse gases emissions, emissionfactorsdue to theelectricityconsumed inHongKongwouldbe722.1gCO2-equivalent/kWh, 0.539 g SO2/kWh, and 0.790 g NOx/kWh. Wealso found that the extraction, production, transportation, and pro-cessing of fossil fuels contributed to 1.65, 5.65, and 5.72 percent of theoverall greenhousegases emissions for coal, heavyoil and light gasoil,and 3.48 and 4.19 percent of the overall greenhouse gases emissionsfor LNG from China and Australia, respectively. By using the logisticgrowth model of Hong Kong’s electricity consumption, it is expectedthat there is a net increase of 1624 million kWh from 2010 to 2015,representing an increase of 3.87 percent. Assuming that there is nochange in the imported electricity from the nuclear power plant inShenzhen, Hong Kong’s power companies need to generate an addi-tional 4.86 percent of electricity locally, resulting in a probableincrease of 1.42 million tonnes of CO2-equivalent.

Some Hong Kong’s people advocate importing more electricityfrom nuclear power plants in Shenzhen. Nevertheless, this strategy

will not solve the problem because the electricity demand inShenzhen has also surged rapidly in the past two decades. Besides,the true cost of nuclear power shall not be underestimated, fromboth environmental and economic perspectives. Sovacool (2008)concluded that the emissions for nuclear energy over the lifetimeof a power plant should range from14 to 288 gCO2-equivalent/kWh.Specifically, he indicated that the construction, treatment of nuclearwaste, and decommissioning of a nuclear power also contributedquite significantly to greenhouse gases emissions indirectly. Interms of the economic cost, the Daya Bay Nuclear Power Plante theone supplying over 10,000 million kWh electricity to Hong Kongevery year e cost US$ 4 billion in construction in 1994. The pres-surized water reactors have a life-span of 40 years. At the end oftheir life, it is expected that US$ 1.3 billion needs to be spent for theplant’s decommissioning. By taking all construction, operating anddecommissioning expenditures into consideration, the levelizedcost of electricity from nuclear power is about US$ 0.05 per kWh(Grubler, 2010). However, in light of the disaster in Fukushimanuclear power stations, a nuclear accident may eventually cost US$30 billion for containment, not counting the potential loss of humanlives and destruction of ecosystems in the affected region.

Based on the fuel life cycle analysis, it is proposed that HongKong should change fuel composition to increase the percentage ofliquefied natural gas in the total fuel mix. It is because liquefiednatural gas is more efficient as a fuel than coal and produces lessgreenhouse gases, SO2 and NOx per kWh generated as shown in4.2.3. In addition, Hong Kong can consider (i) usingmore renewableenergy such as wind and solar energy because wind turbines andsolar power systems do not emit air pollutants during operations,and (ii) planting trees to reduce building energy use (Akbari, 2002).In so doing, the amount of air pollutants discharged from powergeneration can be reduced.

Acknowledgment

The authors gratefully acknowledge the insightful commentsprovided by three anonymous reviewers which led to improvementof the paper.

References

Akbari, H., 2002. Shade trees reduce building energy use and CO2 emissions frompower plants. Environmental Pollution 116 (S1), S119eS126.

Al-Hamad, K.K., Khan, A.R., 2008. Total emissions from flaring in Kuwait oilfields.American Journal of Environmental Sciences 4 (1), 31e38.

W.M. To et al. / Environmental Pollution 165 (2012) 1e1010

Australian Greenhouse Office, 1998. National Greenhouse Gas Inventory.Commonwealth of Australia, Canberra.

Babusiaux, D., Pierru, A., 2007. Modelling and allocation of CO2 emissions ina multiproduct industry: the case of oil refining. Applied Energy 84, 828e841.

Brown, R.E., Koomey, J.G., 2003. Electricity use in California: past trends and presentusage patterns. Energy Policy 31 (9), 849e864.

Censtatd, 2011a. Hong Kong Energy Statistics. Hong Kong Census and StatisticsDepartment.

Censtatd, 2011b. Year-end Population for 2010. Hong Kong Census and StatisticsDepartment.

Cho, Y.S., Lee, J.S., Kim, T.Y., 2007. The impact of ICT investment and energy price onindustrial energy demand: dynamic growth model approach. Energy Policy 35(9), 4730e4738.

Chontanawa, J., Hunt, L.C., Pierse, R., 2008. Does energy consumption cause economicgrowth? Evidence from a systematic study of over 100 countries. Journal of PolicyModeling 30 (2), 209e220.

Costello, D.M., 1993. A cross-country, cross-industry comparison of productivitygrowth. Journal of Political Economy 101 (2), 207e222.

EC, 2003. Integrated pollution prevention and control (IPPC) e reference documenton best available techniques for mineral oil and gas refineries. EU Report,European Commission.

Ehrlich, P.R., Holdren, J.P., 1971. Impact of population growth. Science 171 (3977),1212e1217.

Foss, M.R., 1963. The utilization of capital equipment: postwar compared withprewar. Survey of Current Business 43 (June), 8e16.

Grubler, A., 2010. The costs of the French nuclear scale-up: a case of negativelearning by doing. Energy Policy 38 (9), 5174e5188.

Headthfield, D.F., 1972. The measurement of capital usage using electricity consump-tion data for the UK. Journal of the Royal Statistical Society, Series A-G 135 (2),208e220.

IPCC, 2007. Change in atmospheric constituents and in radiative forcing e IPCCfourth assessment report (AR4), Intergovernmental Panel on Climate Change.

IPCC, 2010. 2006 IPCC guidelines for national greenhouse gas inventories. In:Egglestrom, S., Buendia, L., Miwa, K., Ngara, T., Tanabe, K. (Eds.), IPCC NationalGreenhouse Gas Inventories Programme. IGES, Hayama, Japan. Intergovern-mental Panel on Climate Change.

Kampa, M., Castanas, E., 2008. Human health effects of air pollution. EnvironmentalPollution 151 (2), 362e367.

Kraft, J., Kraft, A., 1978. On the relationship between energy and GNP. Journal ofEnergy and Development 3, 401e403.

Lai, T.M., To, W.M., Lo, W.C., Choy, Y.Z., 2008. Modeling of electricity consumption inthe Asian gaming and tourism center e Macao SAR, People’s Republic of China.Energy 33 (5), 679e688.

Lai, T.M., To, W.M., Lo, W.C., Choy, Y.S., Lam, K.H., 2011. The causal relationshipbetween electricity consumption and economic growth in a gaming and

tourism center e the case of Macao SAR, the People’s Republic of China. Energy36 (2), 1134e1142.

Lam, C.Y., Lau, K.H., 2005. Scientific backgroundof haze and air pollution inHongKong.Presented in the 13th Annual Conference of Hong Kong Institution of Science(Made in Hong Kong II e Science for Better Health & Environment), Hong Kong.

Lam, J.C., Tang, H.L., Li, D.H.W., 2008. Seasonal variations in residential and commercialsector electricity consumption in Hong Kong. Energy 33 (3), 513e523.

Lam, J.C., 1998. Climatic and economic influences on residential electricityconsumption. Energy Conservation and Management 39 (7), 623e629.

Lee, C.C., 2005. Energy consumption and GDP in developing countries: a cointe-grated panel analysis. Energy Economics 27 (3), 415e427.

Markandya, A., Armstrong, B.G., Hales, S., Chiabai, A., Criqui, P., Mima, S., Tonne, C.,Wilkinson, P., 2009. Public health benefits of strategies to reduce greenhouse-gasemissions: low-carbon electricity generation. Lancet 374 (9706), 2006e2015.

Meherara, M., 2007. Energy consumption and economic growth: the case of oilexporting countries. Energy Policy 35, 2939e2945.

Ney, R.A., Schnoor, J.L., 2002. Incremental life cycle analysis: using uncertaintyanalysis to frame greenhouse gas balances from bioenergy systems for emissiontrading. Biomass Bioenergy 22, 257e269.

Psaraftis, H.N., Kontovas, C.A., 2009. CO2 emission statistics for the worldcommercial fleet. WMU Journal of Maritime Affairs 8 (1), 1e25.

Sharma, S.S., 2010. The relationship between energy and economic growth:empirical evidence from 66 countries. Applied Energy 87 (11), 3565e3574.

Sovacool, B.K., 2008. Valuing the greenhouse gas emissions from nuclear power:a critical survey. Energy Policy 36, 2940e2953.

Soytas, U., Sari, R., 2003. Energy consumption and GDP: causality relationship inG-7 countries and emerging markets. Energy Economics 25, 33e37.

To, W.M., Lai, T.M., Chung, W.L., 2011. Fuel life cycle emissions for electricityconsumption in the world’s gaming center e Macao SAR, China. Energy 36 (8),5162e5168.

US DOE, 2009. An Evaluation of the Extraction, Transport and Refining of ImportedCrude Oils and the Impact on Life Cycle Greenhouse Gas Emissions. US NationalEnergy Technology Laboratory. Report No.DOE/NETL-2009/1362, Department ofEnergy.

US EPA, 2006. Life Cycle Assessment: Principles and Practice. US EPA Report No.EPA/600/R-06/060. US Environmental Protection Agency.

Witt, S.F., Witt, C.A., 1992. Modeling and Forecasting Demand in Tourism. AcademicPress, London.

Wong, T.W., Tam, W.S., Yu, T.S., Wong, A.H.S., 2002. Associations between dailymortalities from respiratory and cardiovascular diseases and air pollution inHong Kong, China. Occupational and. Environmental Medicine 59, 30e35.

Yan, Y.Y., 1998. Climate and residential electricity consumption in Hong Kong.Energy 23 (1), 17e20.

Yoo, S.H., 2006. The causal relationship between electricity consumption andeconomic growth in the ASEAN countries. Energy Policy 34, 3573e3582.