1. Introduction
Scholars have traditionally emphasized the importance of environmental and economic sustainability (e.g., maritime industry, product supply chain) [
1,
2,
3]. In contrast, the sustainability of society receives less attention [
4]. However, with the considerable impact of global warming on society, achieving global carbon neutrality is an inevitable choice for mitigating climate warming and ensuring sustainable social development. In 2021,
The Sixth Assessment Report (AR6) by the Intergovernmental Panel on Climate Change (IPCC) confirmed the relationship between the magnitude of global warming and CO
2 emissions, stating that for every trillion tons of CO
2 emitted by human activities the global average surface temperature will rise by 0.27 °C to 0.63 °C [
5]. As the most important greenhouse gas, the concentration of CO
2 in the atmosphere has increased from 300 ppm in 1950 to 410 ppm in 2019, which is 48% higher than pre-industrial levels [
6]. This phenomenon has resulted in unprecedented changes in all the Earth’s major circles [
7]. To reduce the negative effects of global warming, countries have formulated climate control targets such as net zero emission of CO
2, climate neutrality and carbon neutrality [
8,
9,
10]. China has committed to peak carbon CO
2 emissions before 2030 and achieve carbon neutrality before 2060.
With carbon emissions becoming a hot topic in recent years, studies have begun to focus on the future trends of carbon emissions and make suggestions for lowering them. Schmalensee et al. [
11] predicted the future global CO
2 emissions up to 2050 using reduced-form models that were calculated with national-level panel data. Jie et al. [
12] analyzed future energy consumption in the context of urbanization and confirmed the close relationship between carbon emissions and energy consumption. Based on the IPAT model, Zhang et al. [
13] proposed three future scenarios and predicted the future carbon emissions of Anhui Province. They found that technology and mechanism innovation were highly important to reduce carbon emissions in China. In addition, several studies constructed future development scenarios through an energy optimization model [
14], STIRPAT model [
15], MARKAL-MACRO model [
16] and optimized CGE model [
17], and predicted carbon emissions and the driving factors of industries [
18], such as transportation [
19], agriculture [
20] and other sectors or regions [
21,
22,
23]. However, it was found that once the parameter setting is unreasonable, the panel data-based forecasting result will exhibit a large deviation from the reality [
24]. In addition, models based on general equilibrium theory, such as the MARKAL-MACRO model and CGE model, focus on the optimization suggestions of allocation mechanisms, but cannot accurately reflect the technological changes and technological simulations in reality; thus, the simulation results may be quite different from the actual situation [
25]. Among many forecasting models, the Long-range Energy Alternatives Planning System (LEAP) model, based on scenario analysis, has solved these problems to a great extent [
26]. Emodi et al. used the LEAP model to simulate the energy consumption and carbon emissions of industries and regions [
27]. Because of its simple data input and accurate prediction result, the LEAP model is commonly used.
Another path toward the reduction in CO
2 concentration is absorbing CO
2 from the atmosphere; thus, carbon sink also plays an important role in this regard [
28,
29]. Carbon sink is mainly classified as terrestrial and oceanic types [
30]; China’s terrestrial carbon sink absorbs an average of 14.6–16.1% of industrial CO
2 emissions annually [
31]. As the mainstay of terrestrial ecosystems, forest is an important carbon sink. Their carbon sink capacity can be enhanced by afforestation, as well as improving the structure and quality of tree species [
32,
33]. For the prediction of future carbon sink, owing to the strong heterogeneity of terrestrial ecosystems, the estimation of terrestrial carbon sink has tremendous inherent uncertainty [
34]. Previous studies have used ecosystem process models to predict future carbon sink [
35,
36]. Potter et al. [
37] estimated carbon fluxes in terrestrial ecosystems in the United States by using a simulation model based on satellite observations of vegetation cover. Yamagata et al. [
38] evaluated the future carbon sink by combining the simulation of carbon storage change and land use change. The CA-Markov model can not only accurately predict the future land use change, but also effectively simulate the spatial distribution of land use types [
39]; therefore, this model can be an effective way to predict future carbon sink.
The achievement of the carbon neutrality target relies on both reducing CO
2 emissions and increasing carbon sink. A carbon neutrality target is achieved if the source and sink offset each other or if the difference between the two is negative [
40,
41]. In addition, the adoption of carbon capture, utilization, and storage (CCUS) technology to reduce CO
2 can also aid in achieving carbon neutrality targets [
42]. As the realities of different regions differ greatly, such as in their resource endowments and development conditions, setting regional carbon neutrality pathways should highlight local advantages and be tailored to local conditions [
43]. Overall, previous works laid a solid foundation for carbon neutrality research. However, most studies mainly focused on either carbon source or carbon sink [
44,
45], and rarely combined them to discuss the specific realization pathway to the carbon peaking and carbon neutrality targets.
Some studies have found that economic growth is the primary driver of China’s increased carbon emissions [
46]. Furthermore, the increase in carbon emissions sources is influenced by energy intensity, energy structure, and industrial structure [
47,
48]. If carbon emissions sources are to be reduced without impacting economic output, it is necessary to reduce energy intensity, optimize industrial structure and increase the share of non-fossil energy sources [
49]. As a major energy province, Shanxi Province, with high CO
2 emissions, supplies energy to 14 provinces (autonomous regions and municipalities) in China and is under the high pressure to achieve carbon neutrality target. Therefore, based on the aforementioned research shortcomings, and in the context of social sustainability, it is particularly important to analyze the future development of carbon source and carbon sink in Shanxi Province; this is to evaluate the time nodes and specific CO
2 emissions reduction paths for achieving the carbon peaking and carbon neutrality targets in different carbon source–sink scenarios.
In this study, the CO2 emissions generated by terminal energy in Shanxi Province from 2000 to 2020 were calculated. By combining the results with future development policies, three carbon source development scenarios (baseline, policy, and carbon neutrality scenario) were set to estimate carbon source trends from 2020 to 2060 using the LEAP model. In addition, the net primary productivity (NPP) obtained from remote sensing imagery data was used to estimate the carbon sink in this study area from 2000 to 2020. Subsequently, three carbon sink development scenarios (historical, sustainable, and ecological) were generated to predict carbon sink trends from 2020 to 2060 using the CA-Markov model. Finally, the achievement of the carbon peaking and carbon neutrality targets for each combination of carbon source and carbon sink pathways was analyzed. The results will provide scientific support for and carbon neutrality policymaking in Shanxi Province.
4. Discussion
The comprehensive application of non-fossil energy is the key to sustainable development [
72]. The realization of the carbon peaking and carbon neutrality targets around the world largely depends on reducing energy intensity and increasing the share of non-fossil energy [
73]. The path toward carbon neutrality in Shanxi Province is the same as that of most developed countries and regions, focusing on controlling total energy consumption and adjusting energy structures. However, unlike the United States, the European Union, Canada, and other countries that have taken the lead in completing the carbon peaking, the time interval between China’s carbon peaking target and carbon neutrality target is much shorter than that in developed countries [
74], which implies that China faces an even tougher emissions reduction task. Moreover, it also means that China’s carbon peaking should be a low peak of rational development, which is consistent with our prediction results of the policy scenario and the carbon neutrality scenario for Shanxi Province. In addition, as a major energy province in China, Shanxi Province’s special industrial foundation and limited renewable resources render it more dependent on the CCUS technology in achieving carbon neutrality than other provinces in China, such as Beijing, Hainan, Yunnan and other regions with a low proportion of heavy industry or rich in renewable energy.
Accounting the carbon source and sink in Shanxi Province, followed by an exploration of the possibility and timing of achieving the carbon peaking and carbon neutrality targets via different pathways, will provide scientific support for the formulation of carbon neutrality policy in Shanxi Province. Although this study only considers CO
2 emissions from energy consumption in the calculation of carbon source, previous studies have shown that CO
2 from fossil energy combustion accounts for more than 80% of anthropogenic greenhouse gas emissions in China [
75,
76]. As a typical energy province in China, the proportion of CO
2 generated by energy consumption in Shanxi is bound to increase further. Therefore, it is important to conduct carbon peaking and carbon neutrality studies in Shanxi Province using CO
2 emissions from terminal energy consumption as the main carbon source. In addition, NPP changes are less persistent and future developments are highly uncertain [
77]. Therefore, to reduce the impact of NPP changes on future carbon sink projections, this study only considers the possible future changes in land use and uses fixed values for NPP in 2020 for each category. The prediction results have little impact on the overall results of future carbon sink. However, as research progresses, the accurate accounting and prediction of carbon sink would be a key task for future research in the direction of carbon neutrality.
Combining the LEAP model with the CA-Markov model to predict the future development of carbon source and carbon sink, respectively, provides a novel approach to studying carbon neutrality pathways. However, in this study, the use of the LEAP model for future CO
2 emission accounting did not subdivide the industrial sectors, such as iron and steel, metallurgy, machinery, real estate, and transportation sectors. In the future, if we further subdivide and predict CO
2 emissions from various industrial sectors, our predictions will be increasingly close to reality. Furthermore, population, GDP growth, energy intensity, and the share of non-fossil energy are the primary factors for achieving carbon neutrality; all three carbon source scenarios assume the same population and GDP growth based on the aforementioned reasons. However, various intensities of carbon neutrality transition or carbon emissions reduction have been consistently shown to affect the GDP growth path in existing literature [
67,
68]. Population dynamics can be also affected by carbon neutrality-related effects. For example, more people might be willing to move to a region where the energy structure has been improved, whereas shocks to local employment associated with carbon transition (for example, coal mine or coal power plant employees) may lead to migration out of Shanxi if the transition is particularly rapid. Therefore, the potential change in population and GDP growth will be factored into our future work.