University of Groningen The developing role of gas in decarbonizing China's energy system Zhang, Jinrui

The developing role of gas in decarbonizing China's energy system

Zhang, Jinrui

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10.33612/diss.162017806

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Zhang, J. (2021). The developing role of gas in decarbonizing China's energy system: system analysis of technical, economic and environmental improvements of LNG and low carbon gas supply chains and infrastructure. University of Groningen. https://doi.org/10.33612/diss.162017806

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With the global population growth and economic development, natural gas (NG) consumption is projected to grow 1.6% per year accounting for a quarter of global energy demand in 2030 [1][2][3]. By 2035, natural gas could overtake coal as the second-largest fuel source of primary energy [4]. According to the International Energy Agency (IEA) World Energy Outlook [5], 80% of the NG market growth has been concentrated in three key regions since 2010: the United States (shale gas revolution), China (economic expansion and mitigation of air pollution and greenhouse gas (GHG) emissions), and the Middle East (economic diversification from oil). As shown in Figure 1, China and other developing Asia countries are the only regions with projections of gas import growth during 2018 – 2040. This growth accounts for a quarter of global gas production by 2040.

Figure 1 Change in natural gas supply in the Stated Policies Scenario during 2018 –2040. Source: IEA World Energy Outlook [5]

The Intergovernmental Panel on Climate Change (IPCC) Special Report of Global Warming of 1.5 °C [6] has highlighted that NG with carbon capture and storage (CCS) can play a transitional role by replacing coal in the power generation sector. Of the IPCC 1.5 °C compatible pathways of major fossil-based energy sources (coal, oil, and NG), NG is the only growing energy source during 2020 – 2050. The growth is driven by the fact that NG is the cleanest fossil fuel, emitting about 29% to 44% less CO₂, and very small

-5 0 5 10 15 20 Cha ng e o f g as suppl y dur ing 20 18 -2040 ( EJ ) Net imports Net exports Domestic supply

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[7]. Therefore, countries and international organizations have supported NG to reduce anthropogenic GHG emissions and air pollution [8].

According to the IEA [5], over 500 Mt of GHG emissions have been avoided globally by switching from coal to NG since 2010. The largest part of this GHG mitigation happened in the U.S. accounting for 255 Mt CO₂-eq. The shale gas revolution in the U.S. has reduced NG prices and underpinned the coal-to-gas switching in the power sector, reducing GHG emissions by 25% since 2010. In China, the GHG emissions reduction is 155 Mt CO₂-eq due to the coal-to-gas switching. China’s commitment to the Blue Sky Initiative pushes the switching in the industrial sector and residential heating, which will reduce SO₂ and NO_x by 15% in 2020 compared to 2015 [9]. The switching has also been supported by the policy in the European Union 28, which focused on large industrial combustion plants and the power sector. The switching reduced 66 Mt of GHG emissions since 2010. India is positively fighting the air pollution, thereby becoming the fastest growing liquefied natural gas (LNG) market. The effort in India for promoting NG was not only aimed at the largest gas-consuming sector, industrial sectors, but also in the transport sector [8], reducing GHG emissions by 29 Mt CO₂-eq. As an important example of an international organization, the International Maritime Organization (IMO) putted out new pollution regulations in 2020 for the marine sector pushing LNG bunkering into the spotlight [8]. Marine LNG emits almost no SO_x and particulate matter, and 90% less NO_x compared to heavy fuel oil [10]. The cases discussed above clearly show the emission mitigation opportunities for NG across a broad range of sectors in the short term.

In the long term, the gas energy system has the potential to reduce the global GHG emissions by 11.6 Gt CO₂-eq by 2040 accounting for 30% of total GHG emissions in the energy sector (according to IGU Global Gas report [8]). As shown in Figure 2, the coal-to-gas switching (power and industrial switching) and utilization of low-carbon gas have the largest mitigation potentials. The coal-to-gas switching has the potential to reduce 10 times more GHG emissions (5.3 Gt CO₂-eq) by 2040 compared to 2020 (0.5 Gt CO₂-eq) as discussed in previous paragraph. To achieve further reduction of GHG emissions in the long term, the gas system needs to evolve for supplying and using low-carbon gas. Low-carbon hydrogen and low-carbon methane are two main types of low-carbon gas. The production routes of low-carbon gas are discussed in section 3. The combination of these low-carbon gas routes has the potential to avoid 4.9 Gt CO₂-eq of

GHG emissions by 2040 [8].

Figure 2 GHG emissions mitigation potential of the gas energy system by 2040. (Source: IGU Global Gas report [8])

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The increasing importance of NG in global energy markets underpins the need for the NG infrastructure [11]. The NG infrastructure enables the delivery of NG from production sites to markets and end-users. The NG infrastructure can play an important role in the energy transition to a low emission future as well-established gas grids can deliver twice as much energy as electricity grids today, are a major source of flexibility, and have the potential to distribute low-carbon gas produced from renewable sources [5]. There are two options to transport NG to end-users: pipeline gas transport and LNG transport. According to the BP Statistical Review of World Energy [12], the amount of gas transported by pipeline is 32 EJ and by LNG is 19 EJ in 2019.The global gas trade and infrastructure capacity in 2019 are shown in Figure 3. Pipeline infrastructure is well developed in North America with extensive capacity and enormous length. Asia Pacific, CIS, and Europe are equivalent in pipeline infrastructure capacity, but the pipeline length in Asia Pacific is two times of that in CIS and Europe. For LNG import terminal, Asia Pacific and Europe account for over 80% of global LNG import capacity. Currently, the LNG export capacity is especially found in Asia Pacific, Middle East, North America, and Africa.

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Figure 3 Global natural gas trade and infrastructure capacity in 2019 (source: BP Statistical Review of World Energy [12] and Global Gas and Oil Network [13])

Pipeline transport is currently the main transport method and is suitable for short to medium-long transport distances (≤ 4800 km onshore and ≤ 1600 km offshore [14]). LNG transport is cost-effective at longer distances because of the need for a capital-intensive liquefaction plant and regasification terminal. LNG has compensating advantages that can justify its high cost and energy consumption, which includes: flexibility in the

transport route and the supply capacity; and capability of monetizing the remote small gas resources and offshore gas reserves. The average gas transport distance is projected to exceed 5000 km in developing Asian markets by 2040 [5], which will make the future gas supply rely heavily on LNG. According to the IEA World Energy Outlook [5] and BP Energy Outlook [15], LNG will surpass pipeline gas as the main form of international gas trade by the late 2020s.

Figure 4 Change in gas demand by region and sector during 2018 – 2040 in the Stated Policies Scenario. (Source: IEA World Energy Outlook [5])

The projected NG demand by region and sector during 2018 – 2040 is shown in Figure 4. The industrial sector is the most important driver for increasing NG demand, which accounts for around half of the projected growth. As NG is suitable to be used in boiler and furnaces to produce heat, its use is increasing in steelmaking, petrochemical production, and medium- and small-scale manufacturing industry [5]. Most of the NG demand growth in the industrial sector occurs in developing economies. In the power sector, gas usage is increasing in developing economies as well, but remains constant in advanced economies. For developing economies, the projected NG growth in the power sector is driven by strong electricity demand growth. For advanced economies, NG demand for power is projected to peak in the mid-2020s due to renewables growth. In the buildings sector, NG demand for water desalination, cooking, and residential heating is growing in developing economies. The NG demand is decreasing in advanced economies due to improved efficiency, increased electrification, and the use of renewables. In the transport sector, the NG growth is projected in both developing and

-5 0 5 10 15 20 25 30 Indu st ry Po w er Bu ild in gs Tr an sp or t Cha ng e o f g as de m and dur ing 2 01 8-2040 ( EJ )

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vehicles and LNG for marine shipping, trucks, and buses.

Along with increasing NG demand, the investment in NG infrastructure is increasing to enable NG distribution to potential end-users. The IEA projects that the annual average investment on natural gas would be 370 B$ during 2019 – 2040, of which 130 B$ is for gas infrastructure including transmission and distribution pipelines, shipping, and LNG liquefaction and regasification facilities [5].

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lnG

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LNG, as mentioned above, is used for long-distance transport. The typical amount of energy consumed to deliver gas via pipeline is 10–15% of the energy delivered, whereas for LNG this is about 25% of the energy delivered [16]. Liquefaction of NG is one of the most important thermodynamic processes in the cryogenic gas industry. Since the first LNG cargo was sent out, the LNG industry experienced over 60 years of development [3]. The first commercial LNG plant was built in 1964, which was based on the cascade liquefaction process. Then in the early 1970s, the single mixed refrigerant process was introduced. In 1972, the single mixed refrigerant process was substituted with the propane precooling cycle as the C3MR process. Since then, the C3MR process, designed by Air Products (AP), has been the dominant liquefaction process. The capacity of midsize to large size LNG plant is from 0.5 MTPA to 7.8 MTPA (28 PJ/year to 446 PJ/ year) per train. The currently used processes include AP C3MR, AP C3MR/SplitMR, AP-X, ConocoPhillips Optimized Cascade, Shell DMR, Shell C3MR, and Linde MFC. According to the International Gas Union (IGU) world LNG report [17], the Air Products cycles are expected to keep dominating mid to large size plants.

The liquefaction plant is the most capital-intensive part of the LNG value chain, which could account for 50% of gas transportation. The capital costs of liquefaction plants built since 1964 are shown in Figure 5. According to IEA World Energy Outlook [5], project-specific factors are the major factors that affect the capital costs, which include complexity, location, and size of the project.

Figure 5. Specific capital costs of LNG liquefaction plants (L: liquefaction train only) Supplying low-carbon gas in the existing gas infrastructure has the potential to reduce GHG emissions in the long term as discussed in section 1. Based on the IEA World Energy Outlook [5], several routes are available to produce low-carbon gases as shown in Figure 6. The low-carbon hydrogen can be produced from the electrolysis of low-carbon electricity (including fossil-based electricity with CCS), the gasification of biomass, and the steaming reforming of NG and coal gasification (potential methane pyrolysis) with CCS. For low-carbon methane, it can be produced by biogas upgrading to biomethane, gasification of biomass followed by methanation to bio-SNG, and methanation of low-carbon hydrogen with biogenic or air captured CO₂ to low-carbon SNG. A growing body of literature has examined the techno-economic possibilities of utilizing the NG infrastructure to supply low-carbon gas, including renewable hydrogen injection [18] [19] and low-carbon methane addition [20][21]. According to Blanco et al. 2018 [22], power-to-methane has four advantages: reducing CO₂ for hard-to-abate sectors; utilization of existing NG infrastructure without any modification; high energy density (CH₄ has over 3600 MJ/m3 _{while hydrogen has 972 MJ/m}3_{); suitable for the long term and} large-scale storage. Low-carbon gases are promising substitutes for NG, as they can fit in the current NG infrastructure with little or no modification, reduce GHG emissions and improve flexibility in future energy systems.

0 500 1000 1500 2000 2500 0 1 2 3 4 5 6 7 8 9 Sp ec ific C ap ita l C os t($ /T PA ) Capacity (MTPA) Cascade Cascade L MR MR L Others

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Figure 6 Low-carbon gas production routes (source: IEA World Energy Outlook [5])

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China is increasingly becoming a key market of global NG demand growth as shown in Figure 1. As highlighted by IEA World Energy Outlook [5], the NG demand growth in China is projected to be 12.3 EJ in 2040 compared to 2019, which is more than the growth in the rest of developing Asia combined. NG consumption in China has reached 11.1 EJ in 2019, while domestic NG production was only 6.4 EJ [12]. As the domestic NG production cannot meet consumption, China imported 2.9 EJ LNG and 1.7 EJ pipeline gas in 2019 [12]. The Chinese gas infrastructure consisted of 112 natural gas transmission pipelines with a total length of 76,000 km and a capacity of 17 EJ/year and 24 LNG terminals with a capacity of 4 EJ/year in 2019. Chinese LNG imports have surged in recent years, surpassing pipeline gas imports in 2017 [23]. Moreover, China is expected to double the import infrastructure for LNG from 2018 to 2022 [24].

The projected provincial NG demand in China during 2020 – 2050 is presented in Figure 7. As NG consumption is expected to increase during 2020 – 2040, new NG infrastructure is being planned or under construction to deliver NG from domestic and international gas fields to end-users [25]. The domestic NG fields are mainly located in the western part of China: Xinjiang, Sichuan, Chongqing, and Shaanxi, while the demand for NG is concentrated in the eastern part. The pipeline gas is imported from 11 international gas fields. The routes include (quantity order) Turkmenistan to Xinjiang,

Uzbekistan to Xinjiang, Myanmar to Yunnan, Russia to Xinjiang and Heilongjiang [26]. The LNG is mainly imported from 37 overseas gas fields (quantity order) in Australia, Qatar, Malaysia, Indonesia, the U.S., Oman, Russia, Papua New Guinea, Nigeria, Trinidad Tobago, and Norway [26]. To find the best way to supply and use NG from an environmental and economic perspective, it is important to assess the GHG emissions and economic performance of each process in different supply chains for various end-users and to identify potential improvements.

Figure 7 Natural gas demand in China at the provincial level during 2020 – 2050. (Source: China Renewable Energy Outlook [27])

Figure 7 shows that NG consumption is expected to increase during 2020 – 2040, then decrease during 2040 –2050 because of efforts to control GHG emissions for a low-carbon future. This development pushes the NG infrastructure expansion in the short term and leaves the NG infrastructure into the risk of under-utilization in the long term. Therefore, we must consider how to build and use NG the infrastructure in a way that will avoid over capacity and support this low-carbon future. As discussed in sections 1 and 3, the NG infrastructure can play an important role in a low-carbon energy system

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promoted in China for a sustainable growth pathway [28]. For biomethane production, China has utilized anaerobic digestion (AD) on an industrial scale to treat agricultural waste and industrial organic waste since the 1880s [29]. There were 113,000 biogas plants throughout China in 2018, of which 6,737 plants are large-scale (daily biogas yield 500 – 5,000 Nm3_{) and 34 plants are super large-scale (daily biogas yield ≥ 5,000} Nm3_{) [28]. These large-scale and super large-scale biogas plants are suitable for biogas} upgrading to biomethane [30]. For bio-SNG production, the gasification of biomass has great potential to generate combustible gas, heat, and electricity in rural areas of China [31]. Biomass gasification has been applied for three end-uses: residential heating, cooking, and power generation [32]. Since the 7th _{Five-year Plan of China in 1986,} biomass gasification had been promoted for energy development. There are currently more than 600 biomass gasification facilities in China, which provide bio-syngas for 210,000 households [31]. For hydrogen production, the excess electricity from wind and solar generation can produce hydrogen through water electrolysis. It has the lowest GHG emissions among all hydrogen production methods [19][33]. As estimated by Ma et al. [34], the excess wind power in China has the potential to cumulatively produce 17 EJ – 29 EJ of hydrogen during 2020 – 2050. The produced hydrogen can be injected into the existing NG infrastructure to 5% – 15% volume without modifications [35]. For low-carbon SNG production, methane can be produced from renewable hydrogen through the methanation process. The CO₂ source for the methanation could come from carbon capture at biomass facilities and direct air capture [33][22].

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The literature overview identified the following knowledge gaps: 1. A quantitative performance overview of LNG technology is missing in the literature and the small-scale LNG processes are not well optimized compared to large-scale processes on energy efficiency and costs; 2. Few studies focus on life cycle GHG emissions, costs, and potential improvement options of LNG supply chain for various end-users. 3. The future deployment of the NG infrastructure in China is still uncertain and the potential role of the NG infrastructure to supply low-carbon gases has not been well investigated. These knowledge gaps are described in detail in the following paragraphs.

Lack of studies focuses on economic optimization along with energy efficiency optimization for the NG liquefaction process, especially for small-scale liquefaction process. To identify the potential technical and economic improvements of NG

liquefaction process, there is a need for a quantitative overview of the techno-economic performance NG liquefaction processes. This overview will serve as the basis for the optimization of small-scale liquefaction processes and for proposing potential future configurations focusing on small-scale. Several studies focused on improving the energy efficiency of the expander-based natural gas liquefaction process. Their efforts include utilizing mixed refrigerant, two-phase expander, and adding precooling cycle. However, focusing on only energy saving will not always lead to the lowest production cost [36] [37] as the increase in capital and maintenance costs could exceed the energy costs saving. Therefore, optimization should aim at a balance between maintaining energy efficiency on the one hand and low capital costs and maintenance costs on the other hand.

Comprehensive analyses determining the life cycle GHG emissions, costs, and potential improvement options of the LNG supply chain for various end-users in China are missing. Life cycle assessment (LCA) is a robust methodology to evaluate

technologies, processes, projects, and supply chains for environmental impacts [38]. Previous studies focusing on life cycle GHG emissions of LNG can be divided into three general types. The first type of life cycle GHG emissions studies focus on specific parts of the LNG supply chain (mainly on the upstream), including NG production and processing, pipeline transportation, NG liquefaction, LNG shipping, and regasification [39][40][41]. The second type of life cycle GHG emissions studies focus on comparing LNG with pipeline NG or with other energy sources, such as coal gasification [42][43], domestic NG [44][45], coal [44][46][47], diesel [47][48][49], renewables [50][51]. The third type of life cycle GHG emissions studies focus on different usage options, such as power generation [39][52][53], hydrogen production [38], and vehicle fuel [45][49][54][55]. From these three types of studies, most studies only focus on a specific life cycle stage or a single usage option. Only few studies conduct life cycle GHG emissions analysis on the whole life cycle of LNG with various usage options, especially for hydrogen production. There is also a lack of research focusing on the economic performance of the LNG supply chain, which could be as crucial as the life cycle GHG emissions performance of the supply chain. Furthermore, novel improvements for cold utilization of LNG, including

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generation, etc. [56], are not included in the abovementioned studies.

Lack of analyses focuses on optimal deployment and use of the NG infrastructure in China considering low GHG emissions scenarios, availability/ potential of low-carbon gas, and balance of regional supply and demand during 2020 – 2050. There are a lot of studies focusing on transmitting natural gas

optimally through gas pipeline networks. According to a review from Rio-Mercado and Borraz-Sanchez [57], these studies can be classified into three groups: physical design of pipeline, design and location of compression stations, and optimization of network configuration [58][25][11][59]. These studies only focus on integration of natural gas from domestic production and import with gas infrastructure deployment. However, the potential of the NG infrastructure to supply low-carbon gases is not well investigated in China. The GHG emissions and costs of different low-carbon gas supply chains vary in a wide range [5]. The production sites of low-carbon gas are normally different from production sites of NG, the influence on NG infrastructure by supplying low-carbon gas is not yet investigated in previous studies. In order to identify the role of the NG infrastructure in a low-carbon future, it is crucial to estimate the regional low-carbon gas potential, evaluate the GHG emissions and costs of low-carbon gas supply chain, and balance the regional supply and demand in China during 2020 – 2050.

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As China is undergoing an energy transition from a coal dominated energy system to a low-carbon energy system, the main objective of this thesis is to investigate how gaseous energy carriers and the NG infrastructure can be used in the most efficient way for a low-carbon energy system in China towards 2050. In this thesis, the potential role of LNG in the short term and low-carbon gases in the long term for a low-carbon energy system with infrastructure deployment pathway in China are investigated by assessing the energy efficiency, GHG emissions, and costs of the supply chains.

Three research questions are formulated to meet the objective of the thesis:

gas liquefaction and low-carbon gas production when incorporating state-of-the-art improvement options?

2. How to supply and use gaseous energy carriers in a cost-effective way to reduce GHG emissions by assessing different markets and mitigation options on a life-cycle basis?

3. What are optimal deployment pathways of the gas system towards a low carbon future of China and what is the role of the NG infrastructure in these pathways considering low GHG emissions scenarios, availability/potential of low-carbon gas, and balance of regional supply and demand during 2020 – 2050?

The topic of each chapter in this thesis and the related research questions are summarized in Table 1.

Table 1 The topics of thesis chapters and corresponding research questions

Chapter Topic Research question

1 2 3

2 Quantitative harmonization of the technical and economic _{performance of natural gas liquefaction processes} X

3 Technical and economic optimization of expander-based

small-scale natural gas liquefaction processes X X

4 Techno-economic and life cycle GHG emissions _{assessment of LNG supply chain} X X

5 Potential role of natural gas infrastructure in China to _{supply low-carbon gases during 2020 – 2050} X X X

Chapter 2 addresses question 1 by providing a quantitative technical and economic

overview of the status of natural gas liquefaction processes. The LNG processes considered include 15 processes, which are classified into three categories: large-scale onshore, small-scale onshore and offshore. The comparison between liquefaction processes is made based on the type of refrigerant, heat exchanger, driver, and compressor. Primary energy input, specific capital costs, and total production cost were determined as indicators for a harmonized the technical and economic performance of LNG processes. The quantitative harmonization results on the technical and economic performance in Chapter 2 functions as a baseline in the subsequent chapters.

Chapter 3 focuses on improving the technical and economic performance for

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refrigerant; 2) use of two-phase expander; and 3) adding an absorption precooling cycle. These strategies were applied by incorporating an ammonia absorption precooling cycle to a conventional nitrogen expander process and to a novel open-loop expander process, which results in four processes. The optimization was done with two objective functions: minimization of specific energy consumption and minimization of production cost.

Chapter 4 aims to answer question 2 and 3 by assessing the techno-economic

performance and life cycle GHG emissions for various LNG supply chains in China. Chapter 4 improves the current literature by adding supply chain optimization options (cold energy recovery and hydrogen production) and by analyzing the entire supply chain of four different LNG end-users (power generation, industrial heating, residential heating, and truck usage). This resulted in 33 LNG pathways for which the energy efficiency, life cycle GHG emissions, and life cycle costs were determined by process-based material and energy flow analysis, life cycle assessment, and production cost calculation, respectively.

Chapter 5 addresses question 1, 2, and 3 by building a pipeline network flow

model in China at the provincial level and establishing low-carbon gases supply chains to show the GHG emissions and cost of utilizing natural gas infrastructure to supply low-carbon gases using scenarios analysis. Four low-carbon gases were considered in this study, including biomethane, bio-synthetic methane, hydrogen, and low-carbon synthetic methane. The research approach begins by harmonizing NG demand and supply, biomass potential, and solar and wind capacity at the provincial level. Then, low-carbon gas supply chains based on a process-based model were established. The GHG emissions and the cost of utilizing the NG infrastructure to supply low-carbon gases are determined using scenario analysis.

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