Discussion of Energy Consumption and Management in Tianjin

ZHANG Lei，JU Meiting*，LIU Qinzhe，

GUAN Ze College of Environmental Science and Engineering

Nankai University Tianjin 300071, China Zhanglei-nk@163.com

YOU Qi Liaoning Academy of Environmental Sciences

Shenyang 110031, China;

Abstract—By using a modified emergy-based ecological footprint model, this paper dynamic calculated and analyzed the emergy-based ecological footprint and carrying capacity of energy consumption of Tianjin city from 2000 to 2008, and on the basis of this assessed the dynamic changes of carbon emission structure of energy consumption of Tianjin. The result showed that in past nine years the ecological carrying capacity per capita has slowly increased from 0.109 hm2·person-1 in 2000 to 0.234 hm2·person-1 in 2008 , the ecological footprint per capita of the city has quickly increased from 0.413 hm2·person-1 in 2000 to 0.578 hm2·person-1 in 2008, the ecological deficit per capita has steeply rose from 0.304 hm2·person-1in 2000 to 0.345 hm2·person-1 in 2008, and the ecological footprint per ten thousand GDP has decreased from 0.243 hm2·person-1 in 2000 to 0.107 hm2·person-1 in 2008. Along with the fast development, carbon emissions of energy consumption also grew rapidly from 3.478 t·person-1 in 2000 to 4.985 t·person-1 in 2008, and carbon emission intensity decreased from 2.046 t/104yuan in 2000 to 0.923 t/104yuan in 2008. Thus, the investigation revealed that the fast development over the past nine years, energy consumption was far over the carrying capacity, while carbon emissions increased unceasingly, shows that non-sustainability energy consumption has been threatening the economic and social development of Tianjin. According to the results, the paper proposes Tianjin city to promote sustainable energy consumption patterns by measures including restructuring of energy consumption construct, reducing the energy intensity, changing the mode of economic growth and make full use of renewable resources, etc.

Keywords-energy consumption; emergy analysis; ecological footprint; ecological carrying capacity ; carbon emission; energy management;Tianjin

I. INTRODUCTION Cities are center of technological progress, economic

development and social civilization, but also the focus of

conflicts among nature, social and economic development. Currently, more than half of the world's population live in cities and consume huge amount of energy. CO2 emission of global cities accounted for 80% of total emissions, while the CO2 emission by energy consumption accounted for 85% of the total emissions. According to State Statistics Bureau, in 2008, the GDP of China's prefecture and above level cities (not include counties under municipal jurisdiction) reached 18.6 trillion yuan and accounted for 62% of the national GDP, while China's urban CO2 emission reached 3.52 billion tons, accounted for 65% of total emissions. The best 100 cities in economic development discharged 227.9 million tons of CO2, which accounted for about 52% of total emissions. It can be seen that China's cities remains in "high-carbon development model," Economic development and energy consumption has not decoupled. To achieve the low-carbon development and give suggestions on energy management of cities, this paper calculated the emergy-based ecological footprint of energy consumption of Tianjin from 2000 to 2008 and analyzed emergy-based ecological carrying capacity and footprint of energy consumption from the perspective of supply and demand, based on emergy-based ecological footprint model. II. STUDY AREA AND METHODOLOGY A. Study Area

Tianjin is the largest coastal open city in northern China and economic center of the Bohai Rim Region, which locates in 117.2degree east longitude, 39.1degree north latitude and distribute in the elevation of 2-5m above sea level. Tianjin has a total area of 11919.7km2 with rich wetlands resources and total coastline of 153.669km. Tianjin belongs to warm temperate and semi-humid continental monsoon climate zone, has a clear seasonal variation of wind direction and annual average wind speed of 2-4m/s. Tianjin has annual average temperature varied from 11.4-12.9℃ and annual

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average precipitation varied from 520-660mm. Tianjin is rich in geothermal resources, the annual exploitable volume of area is 72.45million m3 and the water temperature is between 30 to 90℃. There are more than 20 kinds of mineral resources has been proven, the area is rich in crude oil and natural gas, but lack of coal that currently totally depend on import, this has been a bottleneck of economic development of Tianjin and the Binhai New Area and ecological environment security. In 2008 the city has resident population of 11.76 million people and regional gross domestic product (GDP) of 635 billion yuan.

B. Data Sources

The basic data in the paper are mainly from "Statistical Yearbook of Tianjin" (2001-2008), the energy conversion factors are mainly cited from "Agricultural ecology" and "Agrotechnique economy handbook", the energy conversion rates are mainly from "Emergy analysis of ecological-economic system". Carbon emission factors and carbon sequestration rates of different forms of energy are referred from reference such as IPCC, etc.

C. Methodology

Emergy analysis is a theory and method for eco-economy system analysis created on base of the traditional energy analysis. Emergy analysis compares different forms of energy that are in different categories and difficult to directly compare by converting them into a unified value, solar energy (sej) through solar energy conversion rate (sej / J or sej / g). By this, resource supply and ecological services of natural ecosystems can be integrated with material production and human consumption of socio-economic systems, thus the value of natural capital be brought into the areas of environmental-economic systems.

The emergy-based ecological footprint model is calculated as follows:

1) Calculation of emergy-based ecological carrying capacity of energy consumption

Emergy-based ecological carrying capacity of energy consumption of area can be calculate as follows：

PTycOEC in

i in

i i /)(11

×== ∑∑ == （1）

In formula, OEC represents ecological carrying capacity per capita；i represents energy types；ci is ecological carrying capacity per capita of energy i；yi is production per capita of energy i ； Ti is energy conversion rate of product i；P represents regional emergy density.

2) Calculation of emergy-based ecological footprint of energy consumption

Calculate emergy-based ecological footprint by set up accounts for energy consumption：

PTxaE n

i iin

i if /)(11 ∑∑ ==

×== （2）

In formula, Ef represents ecological footprint per capita； i represents energy types； ai is ecological footprint per capita of energy i；xi is consumption per

capita of energy i；Ti is energy conversion rate of energy i；P represents regional emergy density。

3) Calculation of ecological deficit and ecological surplus

Ecological deficit is the difference between ecological footprint and ecological carrying capacity when ecological footprint is larger than ecological carrying capacity, it represents that the energy consumption per capita is over ecological carrying capacity in the region; ecological surplus is the difference when ecological footprint is smaller than ecological carrying capacity, it represents that the energy consumption per capita can be support by ecological carrying capacity. To some extent, this value can reflect a quantitative situation of sustainable development of the region.

4) Calculation of carbon consumption According to IPCC-RA， carbon consumption of

energy consumption equals to product energy consumption and carbon emission factors, as follows：

iii inconsumptio EFNCVQE ××= ∑ （3）

Electricity consumption has no direct carbon consumption, the carbon consumption of which is the carbon consumption of raw material input like coal and other energy sources in production process, the formula is：

coalielec EFNCVqE ∑ ××= μ （4）

Qi represents consumption of energy i（kg or m3）；NCVi represents net calorific of energy i（J/t or J/m3），EFi represents carbon emission factors of energy i（kg/GJ），Eelec represents carbon consumption of eletricity（t），q is consumption of eletricity（kWh），NCVcoal represents net calorific of coal （ J/kWh ）， EFcoal represents carbon emission factors of coal（kg/GJ），µ is conversion factors between heat mechanical equivalent of eletricity and coal.

5) Calculation of energy-carbon consumption structure factors

Zhang Lei(2003) brought forward that Energy-Carbon Consumption Structure （ECCS） can be calculate as follows：

coali i EEECCS /1∑ =

= （5）

ECSS is short for energy-carbon consumption structure; i represents energy types; Ei represents terminal carbon consumption of energy i; Ecoal represents terminal carbon consumption of coal. III. RESULTS AND DISCUSSION A. Calculation of Emergy-based Ecological Footprint of Energy Consumption of Tianjin

According to "Statistical Yearbook of Tianjin" (2001-2009), the paper calculated and analyzed the emergy-based ecological footprint and emergy-based ecological carrying capacity output by energy consumption in Tianjin from 2000 to 2008 based on the

modified emergy-based ecological footprint model (see Table 1). As mentioned, crude oil and natural gas were the only two types of energy produced in Tianjin, and were also the only two considered when calculated the

value of the emergy-based ecological carrying capacity of urban energy output. Energy consumption accounts included coal, coke, crude oil, etc. Value of regional emergy density P used 1.73 × 1016 sej/hm2.

TABLE 1. CALCULATION FOR EMERGY-BASED ECOLOGICAL CARRYING CAPACITY AND FOOTPRINT OF TIANJIN FROM 2000 TO 2008

Item 2000 2001 2002 2003 2004 2005 2006 2007 2008

Emergy ecological carrying capacity（hm2·person-1）

Crude oil 9.93E-02 1.26E-01 1.57E-01 1.69E-01 1.83E-01 2.22E-01 2.35E-01 2.25E-01 2.21E-01

Natural gas 9.81E-03 9.62E-03 9.52E-03 9.06E-03 8.76E-03 9.11E-03 1.05E-02 1.29E-02 1.29E-02

Total 1.09E-01 1.35E-01 1.67E-01 1.78E-01 1.92E-01 2.32E-01 2.46E-01 2.38E-01 2.34E-01

Emergy ecological footprint（hm2·person-1）

Coal 1.67E-01 1.78E-01 1.97E-01 2.15E-01 2.32E-01 2.47E-01 2.40E-01 2.39E-01 2.29E-01

Coke 4.16E-03 3.73E-03 4.35E-03 4.12E-03 9.40E-03 9.23E-03 1.47E-02 1.75E-02 1.79E-02

Crude oil 9.21E-02 9.70E-02 8.73E-02 9.68E-02 9.98E-02 1.07E-01 1.09E-01 1.11E-01 8.77E-02

Fuel oil 1.28E-02 1.39E-02 1.38E-02 1.78E-02 1.76E-02 1.73E-02 1.57E-02 1.30E-02 1.23E-02

Petrol 1.99E-02 2.05E-02 1.66E-02 1.84E-02 2.07E-02 2.03E-02 2.09E-02 2.19E-02 2.24E-02

Kerosene 3.00E-03 1.79E-03 2.38E-03 2.97E-03 2.34E-03 2.30E-03 2.23E-03 2.69E-03 2.55E-03

Diesel 3.15E-02 2.91E-02 2.90E-02 3.06E-02 3.53E-02 3.75E-02 3.69E-02 3.71E-02 3.92E-02

Natural gas 3.93E-03 7.85E-03 7.82E-03 7.79E-03 7.70E-03 7.55E-03 1.10E-02 1.41E-02 1.67E-02

Electricity 7.84E-02 8.30E-02 9.23E-02 1.03E-01 1.13E-01 1.26E-01 1.37E-01 1.52E-01 1.51E-01

Total 4.13E-01 4.35E-01 4.50E-01 4.96E-01 5.38E-01 5.75E-01 5.88E-01 6.07E-01 5.78E-01

Ecological deficit -3.04E-01 -2.99E-01 -2.84E-01 -3.17E-01 -3.46E-01 -3.43E-01 -3.42E-01 -3.70E-01 -3.45E-01

GDP per capita (104) 1.6999 1.9113 2.1354 2.5492 3.0390 3.5452 4.0412 4.5295 5.4034

Population (104) 10011.4 10040.6 10071.8 10113 10236.7 10430 10750 11150 11760

1) Analysis on emergy-based ecological carrying capacity, ecological footprint and ecological deficit per capita of energy consumption

Figure 1. Change curves of emergy-based ecological carrying capacity, ecological footprint and ecological deficit per capita of energy consumption of Tianjin from 2000 to 2008 As shown in Figure 1, from 2000 to 2008, the

emergy-based ecological carrying capacity of energy consumption of Tianjin had a slow upward trend. The percentage that Tianjin’s oil output took up the national output had increased from 4.7% in 2000 to 10% in 2008; the percentage of natural gas had decreased from 3.3% in

2000 to 1.8% in 2008. The faster increase of emergy-based ecological footprint of energy consumption per capita has resulted in expansion of ecological deficit per capita year by year. By 2008, the ecological deficit is 0.345hm2·person-1, and the emergy-based ecological footprint per capita was 2.47times than emergy-based ecological carrying capacity per capita, showed that energy consumption in Tianjin has far exceeded the level of ecological carrying capacity, the energy load has threatened the ecological safety of the city and the dependence on foreign energy is growing.

2) Analysis on changes of emergy-based ecological footprint of energy consumption per ten thousand yuan GDP

Figure 2. Change curves of emergy-based ecological footprint of energy consumption per capita GDP and per ten thousand yuan GDP of Tianjin from 2000 to 2008 Emergy-based ecological footprint of energy

consumption per ten thousand yuan GDP can characterize energy efficiency, the emergy-based ecological footprint is larger, and the energy efficiency is lower. As shown in Figure 2, the GDP per capita of Tianjin has increased from 17 thousand yuan/person in 2000 to 54 thousand yuan/person in 2008, the emergy-based ecological footprint of energy consumption per ten thousand yuan GDP has decreased from 0.243 hm2/104yuan in 2000 to 0.107 hm2/104yuan in 2008. The fast decline reflected the continuing improvement of energy efficiency with economic development in Tianjin, the economy of the city had grown towards to positive trend.

3) Analysis on structure of energy consumption per capita GDP

Figure 3 shows from 2000 to 2008, consumptions of coal and coke took over 40% of total emergy-based ecological footprint, and because the total energy consumption was increasing year by year, the consumptions of coal and coke were also increasing year by year; consumptions of crude oil, fuel oil, petrol,

kerosene, diesel oil and other petroleum products were increased in gross amount while decreased in percent; emergy-based ecological footprint of electricity consumption had rapidly increased, while 75.2% of the electricity was thermal power locally produced, the other was transferred from other provinces. In essence, electricity consumption can be considered as coal consumption, so the percent of coal consumption in fact has maintained over 60%. It can be seen that emergy-based ecological footprint of coal took overwhelmingly important role in the structure of energy consumption of Tianjin, but the emergy-based ecological carrying capacity of coal is zero, the energy consumption structure which rely entirely on imported coal is very negative for energy consumption safety of the city.

Figure 3. Emergy-based ecological footprint structure of energy consumption per capita of Tianjin from 2000 to 2008 B. Calculation of Carbon Emissions From Energy Consumption of Tianjin

According to various types of energy consumption of Tianjin from 2000 to 2008, and combined with carbon emission imperfect data from IPCC Guidelines (2006) to calculated the carbon emissions from energy consumption of Tianjin from 2000 to 2008 (see Table 2).

TABLE 2. CALCULATION OF CARBON EMISSIONS FROM ENERGY CONSUMPTION OF TIANJIN FROM 2000 TO 2008(t)

Item 2000 2001 2002 2003 2004 2005 2006 2007 2008

Carbon

emission

imperfect

data kg/GJ

Coal 1.94E+07 2.07E+07 2.30E+07 2.52E+07 2.75E+07 2.98E+07 2.99E+07 3.08E+07 3.12E+07 26.8

Coke 1.18E+06 1.06E+06 1.24E+06 1.18E+06 2.73E+06 2.73E+06 4.49E+06 5.55E+06 5.98E+06 29.2

Crude oil 6.50E+06 6.86E+06 6.19E+06 6.90E+06 7.20E+06 7.90E+06 8.27E+06 8.71E+06 7.27E+06 22

Fuel oil 6.76E+05 7.38E+05 7.38E+05 9.53E+05 9.53E+05 9.53E+05 8.92E+05 7.69E+05 7.69E+05 20.2

Petrol 1.04E+06 1.08E+06 8.75E+05 9.76E+05 1.11E+06 1.11E+06 1.18E+06 1.28E+06 1.38E+06 20

Kerosene 1.49E+05 8.92E+04 1.19E+05 1.49E+05 1.19E+05 1.19E+05 1.19E+05 1.49E+05 1.49E+05 18.9

Diesel 2.44E+06 2.26E+06 2.26E+06 2.39E+06 2.80E+06 3.02E+06 3.07E+06 3.20E+06 3.56E+06 29.5

Natural

gas 2.23E+05 4.46E+05 4.46E+05 4.46E+05 4.46E+05 4.46E+05 6.69E+05 8.92E+05 1.11E+06 15.7

Electricity 3.21E+06 3.40E+06 3.80E+06 4.24E+06 4.73E+06 5.38E+06 6.02E+06 6.90E+06 7.25E+06

Total 3.48E+07 3.66E+07 3.87E+07 4.24E+07 4.76E+07 5.15E+07 5.46E+07 5.83E+07 5.87E+07

1) Analysis on carbon emission intensity of energy consumption

As shown in Figure 4, per capita GDP of Tianjin had rapidly risen from 2000 to 2008 with an annual average growth rate of 15.5%; energy consumption and carbon emissions had also risen, but the growth rate of carbon emissions was less than GDP growth rate. Especially after 2005, with in-depth implementation of energy-saving and emission reduction policies, growth trend of carbon emissions had clearly changed, carbon emissions in 2008 were 5.865 × 107t, 1.69 times than that in 2000, but slightly decreased compared with 2007. Carbon emission intensity of energy consumption means carbon emissions per capita GDP, can characterize contribution to climate change mitigation by economic development, while to some extent rate the decline of intensity can reflect the improvement of corresponding economic benefits from energy consumption and carbon emissions. As shown in Figure 4, carbon emission intensity had reduced from 2.046t/104yuan in 2000 to 0.923t/104yuan in 2008; the annual average decline rate of carbon emission intensity was 9.5%, less than GDP annual average growth rate of 15.5%, so Tianjin failed to achieve an absolute reduction of carbon emissions.

Figure 4. Curves of changes carbon emissions, carbon emission intensity and per capita GDP of Tianjin from 2000 to 2008 2) Analysis on carbon emission structure of energy

consumption per capita Carbon emission structure of energy consumption per

capita of Tianjin from 2000 to 2008 is shown in Figure 5. It can be seen that coal and coke took up the highest proportion, more than 60% of total carbon emissions from energy consumption in Tianjin. In 2008, carbon emissions from coal and coke were 3.158t·person-1, took

up 63.3% of total carbon emissions, the value increased 4.2% than in 2000. From 2000 to 2004, the proportion of carbon emissions from electricity consumption remained about 9%, while since 2005, the proportion of carbon emissions from electricity consumption had increased year by year, and in 2008 it reached 12.4%. The proportion of carbon emissions from consumptions of crude oil, fuel oil, petrol, kerosene, diesel oil and other petroleum products had decreased from 31.6% in 2000 to 24.3% in 2008, of which crude oil reduced most in carbon emissions, from 0.649t·person-1 in 2000 to 0.618t·person-1 in 2008. To further illustrate the characteristics of changes in energy consumption structure of Tianjin, the paper has calculated the energy-carbon consumption structure factors of Tianjin from 2000 to 2008 according to the formula (5). As shown in Figure 6, the factors of Tianjin structural changes in the energy-carbon consumption coefficient showed a volatility downward trend. From 2000 to 2004 the factor declined significantly, but since 2005 it had slow risen, while in 2008 decline again. This shows that the carbon consumption proportion of coal in Tianjin was expanded year by year. Since the implementation of energy-saving and emission reduction in 2005, the proportion was decreased, but overall it still has not changed energy pillar of coal in carbon consumption. Coal and coke were the largest contributor to carbon emissions and also the key to achieve carbon reduction of Tianjin in last nine years.

Figure 5. Carbon emission structure of energy consumption per capita of Tianjin from 2000 to 2008

Figure 6. Energy-carbon consumption structure of Tianjin from 2000 to 2008 IV. SUGGESTIONS ON ENERGY MANAGEMENT Tianjin has proposed "Energy conservation

regulations in Tianjin" in 2001 and has fully implemented energy-saving and emission reduction, a lot of success had also made. However, the analysis on current energy-based ecological footprint of energy consumption in Tianjin shows, there are still many issues to be solved. In order to reduce energy-based ecological footprint and ecological deficit of energy consumption, and to improve the quality of the ecological environment and sustainable development capability in urban areas of Tianjin without reducing the people's living standards, we recommend the following measures:

1) Speed up the restructuring of energy consumption construct and promote the optimum allocation and rational utilization of energy resources. Increase development and use of petroleum products based on the status quo that coal of Tianjin relies entirely on import, it should gradually convert the city's pillar of energy from coal to petroleum products, thus to reduce ecological deficit of energy consumption ;

2) Reduce the energy intensity and promote energy-saving. Actively promote energy-saving technological innovation such as transformation of coal-fired industrial boiler, cogeneration, utilization of waste heat and pressure, reconstruction of electrical system, to achieve cascade and efficient use of energy;

3) Change the mode of economic growth and industrial structure. Further increase the proportion of tertiary industry and adjust the structure of second industry to increase the proportion of high value-added industries. To achieve high economic growth, low energy consumption and negative growth of environmental pollution, through reform high-energy sector, energetically develop clean production and circular economy, improve energy use and recycling system, etc;

4) Make full use of renewable resources. Combined with natural characteristic of Tianjin, increase use of natural gas, liquefied petroleum gas and other clean energy, appropriate increase utilization of wind power and nuclear power;

5) Develop low-carbon economy. Research carbon sequestration technologies, actively promote the carbon emission reduction and encourage the adoption of emissions trading and CDM mechanisms in order to achieve the goals for carbon emission reduction.

6) Promote energy-saving and sustainable consumption living patterns. Establish a resource-saving system of social production and consumption through green building, sustainable procurement and consumption, green transportation, etc. ACKNOWLEDGEMENTS

This work was supported by the project of National Natural Science Foundation of China (No. 70873065). REFERENCES [1] CHEN Fu. Agricultural ecology [M]. Beijing: China

Meteorological Press, 1998:30-60. [2] Churkina G. Modeling the carbon cycle of urban systems[J].

Ecological Modeling, 2008; 216(2):107-113. [3] Editorial Committee of Agrotechnique Economy Handbook.

China Agriculture Press, 1983. [4] Feng ZJ, Jin Y, Niu WY, Xu DM. Considerations on scientific

promotion to low-carbon economy[J]. Guangxi energy-saving,2009(3):24-26.

[5] He Jiankun, Liu Bin. Analysis of carbon emission intensity as the main index for greenhouse gas emission mitigation commitments[J]. Journal of Tsinghua University (Science and Technology), 2004; 44(6):740-743

[6] IPCC. 2006 IPCC guidelines for national greenhouse gas inventories [R]. IGS, Japan: the National Greenhouse Gas Inventories Programme, 2006.

[7] IPCC/IEA/OECD/UNEP. Greenhouse gas inventory reporting instruction, revised 1996 IPCC guidelines for national.

[8] LAN Shengfang, QIN pei, LU Hongfang. Emergy analysis of ecological-economic[M]. Chemical Industry Press, 2002.

[9] ODUM HT. Systems ecology. New York: John Wiley and Sons, 1983.

[10] OECD/IEA. World Energy Outlook, 2007/2008[R]. Paris: International Energy Agency, 2007/2008.

[11] Tianjin Municipal Bureau of Statistics. Statistical yearbook of Tianjin[M]. Beijing: Chinese Statistics Press, 2001-2008.

[12] World observation research institute of Tsinghua University. Renewables Global Status Report 2007, 2008.

[13] Zhang Lei. Economic Development and Its Bearing on CO2 Emissions[J]. Acta Geographica Sinica, 2003; 58(4):629-637.