Near-term CO₂ storage potential for coal-fired power plants in China: A county-level source-sink matching assessment

Highlights

• Near-term storage potential was obtained by source-sink matching within counties.

• 60 counties have the storage potential of 224.67Mt/y without considering injection capacity.

• 30 counties have the storage potential of 99.01Mt/y considering injection capacity.

• The near-term demonstration provinces such as Hebei and Jiangsu were selected.

Abstract

Carbon capture, utilization, and storage (CCUS) is regarded as an important option to reduce the CO₂ emission of the electricity industry, especially in China. But emissions reduction potential of CCUS within each special administrative region needs to be identified. We explored the near-term CO₂ storage potential of coal-fired power plants in China from the county perspective. According to the results of emissions sources and storage sites within counties, the following findings were reached: 1) Coal-fired power plants are distributed in 441 counties, the oil fields are in 149 counties, and the deep saline aquifers are in 561 counties. The spatial distribution of storage sites and coal-fired power plants is not consistent across counties. 2) Considering the injection capacity of single well, the CO₂ storage potential decreased by more than 50%. Thirty counties have emission reduction potential through CCUS, with a total of 99.01Mt/y. 3) The CCUS emission reduction of counties in the top five provinces accounts for 83.9% of the total. Hebei, Xinjiang, Tianjin, Jiangsu, and Anhui provinces can be regarded as demonstration provinces for near term project deployment.

Introduction

As of 2018, the global carbon budget report indicated that with only 1200 Gt of cumulative global carbon dioxide (CO₂) emissions there is for a 66% chance of holding global temperature increase to 2 °C above preindustrial levels. To achieve a 1.5 °C target, the total carbon budget will decrease to 420 Gt by 2100 [1]. Given that the CO₂ emissions in 2017 were 53.5Gt [2], the aforementioned carbon amounts could be exhausted within 8–30 years at current emissions levels [3], [4]. Carbon capture, utilization, and storage (CCUS)¹ technologies may help achieve deep emissions reduction targets globally [5]. The International Energy Agency (IEA) pointed out that to hold global temperature increase to 2 °C above preindustrial levels in this century, the relative contribution of CCUS technology will need to reach 14% by 2060; the contribution of emission reduction by the Beyond Two Degree Scenario (B2DS) may have to be as high as 32% [6].

Research on CCUS includes: CO₂ capture, transportation, and storage [7], [8]; the economics of CCUS [9], [10]; the uncertainty in CCUS deployment [11], [12]; the risks of geological storage [13], [14]; aspects of geological exploration [15]; and public acceptance [16], [17]. With the development of CCUS research, as well as various demonstration projects and ongoing large-scale storage projects, an understanding of the basic physical processes and engineering issues of geological storage is maturing [18]. By 2019, there were 51 commercial large-scale global CCUS facilities (19 in operation, 4 under construction, 10 in advanced development using a dedicated front-end engineering design approach, and 18 in early development), which suggests that technical feasibility have not been the constraint for CCUS deployment. Also, there are no technology barriers to permanently store CO₂ at the rate and the scale needed to meet ambitious climate targets [19].

However, the large-scale development of the entire industrial chain for CCUS still faces external constraints, such as the types and location of emission sources, general geographical environment, and specific geological conditions of storage sites. In the future, for large-scale commercialization of CCUS, a challenge is to find suitable storage sites for CO₂ emission sources within a reasonable distance. The distance from emission sources to storage sites is related to the CCUS deployment potential and affects the operation cost of CCUS and the formation of CCUS industrial clusters [20]. Since 2006, China has been the largest CO₂ emitter and coal consumer in the world. The world’s biggest CO₂ emitter accounts for a quarter of humanity’s emissions today, making the nation a crucial part of any efforts to minimize global warming. Energy-related carbon emissions account for 89% of the total emissions in China, of which the power sector contributes half [21]. This is because electricity demand is growing rapidly; thermal power plants dominate power generation with an installed capacity accounting for 64% of the total installed capacity at the end of 2016 in China. And the installed capacity of coal-fired power plants (CFPPs) accounted for 89% of all thermal power plants [22].

The emission reduction of the power industry in other countries is different from that of China. For example, the energy structure of the United States is shifting from coal to natural gas. The proportion of coal-fired power generation in the power generation structure has dropped to 31.4%, while the proportion of natural gas has increased to 32.9% [23]; The EU is shifting from coal to wind and solar power generation. By 2018, many countries had implemented measures to replace coal-fired power generation, effectively reducing the carbon emissions of the power system [24]. In Germany, coal-fired power generation accounts for 42.2% of the total power generation, and the government is committed to vigorously developing renewable energy. According to the Transforming Germany’s Energy System (Energiewende) Plan [25], the proportion of renewable energy power generation will increase to 65% by 2030. Considering the fossil energy-based energy structure in China, the necessity of CCUS application in China's power industry is more apparent. CCUS is regarded as one of the most important technological options to reduce CO₂ emissions rapidly in CFPPs, as CCUS can achieve deep reduction of fossil fuel utilization in China [26]. By 2040 and 2050, CCUS in the power sector will contribute up to 238 MtCO₂/y and 1428 MtCO₂/y, respectively; and the share of CFPPs equipped with CCUS technology is expected to reach 6% in 2040 and 56% in 2050 [27].

The application potential of CCUS is also restricted by the suitability of storage sites, including CO₂ geological storage potential (abbreviated as “storage potential”) and injection capacity. The storage potential is huge in China, but the spatial geological conditions of sedimentary basins differ greatly [28]. Injection capacity is a key characteristic of storage sites, defined by the largest amount of CO₂ that can be injected per year in a single well [29], [30]. The storage potential and injection capacity per well vary widely under different geological conditions [31]. In general, although the implementation of CCUS is less impacted by the CO₂ storage potential compared to other restrictive factors [32], [33], the amount of CO₂ that can be injected by a project must be matched to the injection capacity of that area.

The scales of the existing CCUS projects in China have not yet reached 1 million-ton capacity, and they are far less than the Gt-scale deployment needed by the end of the century to meet climate change mitigation targets [8]. Under the current conditions of CCUS development in China, it is vital to assess the CO₂ storage potential for near-term deployment of CCUS (at a relatively low cost) and identify the early opportunities for promoting CCUS through its spatial characteristics, thereby providing for useful policy approaches for Chinese emission reduction. The early opportunities of CCUS can drive a new generation for technological breakthroughs, accumulate excessive engineering experience in future storage technologies with greater emission reduction potential, and lay the foundation for subsequent full-process technical system integration and large-scale demonstration [34]. Given the high cost of transporting CO₂, enterprises may not choose a storage site that is far away from the emission source, especially in the near term.

We assessed CCUS at the county level to identify the near-term application potential in coal-fired power fleets, considering the challenges of cross-county negotiation regarding storage activities. This is consistent with a recent study considering bioenergy with carbon capture and storage (BECCS) potential [30]. Further, for greater detail and practicality, we considered the CO₂ storage potential and injection capacity of deep saline aquifers (DSA) and oilfields. The following questions framed the research:

What is the CO₂ emission reduction potential of near-term application of CCUS for coal-fired power fleets in China and how does the injection capacity affect it?

What is the distribution of emission reduction potential at the county-level and what is the utilization of DSA and oilfields?

Which provinces can be regarded as demonstration areas for early CCUS project deployments?