Steel supply chain emission reduction method under carbon tax-carbon transaction collaborative management and control policy

Abstract

The invention provides a steel supply chain emission reduction method under a carbon tax-carbon transaction collaborative management and control policy, and the method comprises the steps: giving a model assumption condition in order to optimize a collaborative emission reduction decision among a government, a steel manufacturer and a transportation carrier; based on a given model assumption condition, constructing a steel manufacturer and transportation carrier collaborative emission reduction differential game model, and seeking to realize an optimal collaborative decision of both parties in the aspect of emission reduction while pursuing enterprise profit maximization; in order to improve the overall social welfare, a government and steel supply chain Stackelberg game model is constructed, and the optimal carbon tax rate and the initial carbon quota which should be formulated by the government in the low-carbon policy are determined. On the basis of the Stackelberg differential game theory, under the carbon tax-carbon transaction collaborative management and control policy, a double-layer game model between the government and the steel supply chain and between the government and the steel supply chain is established, reference suggestions are provided for the government to formulate the policy, and the optimal steel supply chain carbon emission reduction strategy is obtained.

Description

Technical Field

[0001] The present invention relates to the field of steel supply chain industry and carbon emission reduction policy formulation technology, and in particular, to a steel supply chain emission reduction method under a carbon tax-carbon trading coordinated management and control policy. Background Art

[0002] At present, existing research has not involved the coordinated management policy of carbon tax and carbon trading, and the research on carbon emission reduction in the steel supply chain is mostly limited to decision-making issues in steel companies' manufacturing technology improvements, corporate operations management, etc. There has been no research on the coordinated emission reduction strategies of steel manufacturers and transportation carriers, the two closely linked upstream and downstream companies in the supply chain.

[0003] Existing literature has not yet incorporated the newly proposed carbon tax-carbon trading coordinated control policy into the research context, which is of great significance for achieving China's "dual carbon" goals (i.e., carbon peak and carbon neutrality). Existing research has mostly focused on a single low-carbon policy or a "mixed" low-carbon policy, and has failed to fully consider the cross-implementation conditions and mutual influence of carbon tax and carbon trading in the coordinated control policy.

[0004] Existing research often focuses on emission reduction issues of steel enterprises, such as manufacturing technology improvements and operational management decisions, while ignoring the collaborative emission reduction strategies between steel manufacturers and transport carriers, two high-carbon nodes in the steel supply chain. This leads to insufficient assessment of the overall emission reduction potential of the supply chain.

[0005] In summary, existing research on carbon emission reduction strategies in the steel supply chain has problems such as lagging policy background updates and insufficient research on collaborative emission reduction strategies at key nodes in the supply chain. These shortcomings limit the comprehensive understanding of the carbon emission reduction potential of the steel supply chain and the formulation of effective strategies. Summary of the invention

[0006] According to the technical problems raised above, a method for reducing emissions in the steel supply chain under the carbon tax-carbon trading coordinated control policy is provided. Based on the Stackelberg differential game theory, the present invention establishes a two-layer game model between the government and the steel supply chain and within the steel supply chain under the carbon tax-carbon trading coordinated control policy, provides reference suggestions for the government to formulate policies, and obtains the optimal carbon emission reduction strategy for the steel supply chain.

[0007] The technical means adopted by the present invention are as follows:

[0008] A method for reducing emissions in the steel supply chain under a carbon tax-carbon trading coordinated management policy, comprising:

[0009] S1. In order to optimize the collaborative emission reduction decision between the government, steel manufacturers and transport carriers, the model assumptions are given;

[0010] S2. Based on the given model assumptions, a differential game model of coordinated emission reduction between steel manufacturers and transport carriers is constructed to seek to achieve the optimal coordinated decision-making of both parties in emission reduction while pursuing the maximization of corporate profits;

[0011] S3. With the goal of improving overall social welfare, a Stackelberg game model between the government and the steel supply chain is constructed to determine the optimal carbon tax rate and initial carbon quota that the government should formulate in its low-carbon policy.

[0012] Furthermore, step S1 specifically includes:

[0013] S11. Assume that the emission reduction costs of steel manufacturers are:

[0014]

[0015]

[0016] Among them, C M (E m (t)) represents the emission reduction cost of upgrading the technology and equipment of steel manufacturers; E m (t) represents the degree of emission reduction efforts of steel manufacturers at time t, E m (t)≥0;η m represents the effort cost coefficient of the steel manufacturer, η m >0;C M (τ m (t)) represents the CO2 recycling and reuse emission reduction cost of steel manufacturers; α represents the CO2 recycling and reuse cost coefficient of steel manufacturers, α>0; τ(t) represents the CO2 recycling and reuse level of steel manufacturers at time t, τ(t)≥0;

[0017] Assume that the emission reduction cost for transport carriers is:

[0018]

[0019] Among them, C T (E t (t)) represents the emission reduction cost of transport carriers investing in green transport equipment; η t represents the transport carrier's effort cost coefficient, η t >0;E t (t) represents the degree of emission reduction efforts of transport carriers at time t, E t (t)≥0;

[0020] S12. Assuming that the degree of emission reduction in the steel supply chain is determined by the emission reduction efforts of steel manufacturers and transport carriers, which is a dynamic process, the emission reduction trajectory of the supply chain is expressed as:

[0021] x(t)=γ(E m (t)+τ(t))+γ t E t (t)-δx(t)

[0022] Where x(t) represents the degree of emission reduction in the steel supply chain at time t, and x(0) = x0 ≥ 0; γ t The coefficient that represents the impact of the transport carrier’s emission reduction efforts on the steel supply chain’s emission reduction efforts, γ t >0; δ represents the attenuation coefficient of the steel supply chain emission reduction when steel manufacturers and transport carriers do not take emission reduction measures, δ>0;

[0023] S13. Assuming that the concept of low carbon is gaining popularity, steel market customers will choose long-term partners based on the degree of carbon emission reduction in the supply chain. The emission reduction efforts of steel manufacturers and transport carriers will indirectly affect the demand for products through the emission reduction degree of the supply chain. The demand function is simplified to:

[0024] Q(t)=a+θx(t)

[0025] Where Q(t) represents the total output of steel products at time t; a represents the potential market demand, a>0; θ represents the coefficient of the impact of the enterprise's emission reduction efforts on demand, θ>0;

[0026] S14. Assume that all products produced by the steel manufacturer are transported by the transport carrier and the output Q is the total transport volume;

[0027] S15. The government imposes carbon taxes on steel manufacturers and transport carriers at different rates. Enterprises need to pay taxes on their initial carbon quotas. The carbon tax function is as follows:

[0028] t t (t) = β2(t)q t (t)

[0029] t m (t) = β1(t)q m (t)

[0030] Among them, t t (t) represents the total amount of carbon tax collected by the government from transport carriers at time t; m (t) represents the total amount of carbon tax collected by the government from steel manufacturers at time t; β1(t) represents the carbon tax rate levied by the government on steel manufacturers at time t; β2(t) represents the carbon tax rate levied by the government on transport carriers at time t; q m (t) represents the initial carbon quota of the steel manufacturer at time t; q t (t) represents the initial carbon quota of the transport carrier at time t;

[0031] S16. The initial carbon quota allocated by the government in a single period is an exogenous variable and cannot be transferred to the next period;

[0032] S17. In the model based on CO2 reuse, the CO2 generated by steel production is re-invested in production at a ratio of α. The actual carbon quota available to steel manufacturers in carbon trading is:

[0033] q m (t)-(1-α)Qe m

[0034] Among them, e m represents the carbon emissions per unit of product produced by steel manufacturers, e m >0;

[0035] S18. Assume that the internal carbon trading price is inversely proportional to the emission reduction efforts of steel manufacturers and directly proportional to the emission reduction efforts of transport carriers, as follows:

[0036] p1(t)>p2(t)

[0037]

[0038] Where p2(t) represents the internal carbon quota transaction price at time t, p2(t)≥0; σ represents the internal carbon quota transaction price coefficient, σ>0;

[0039] S19. For the government, the negative externality of carbon emissions when steel manufacturers consider CO2 reuse is expressed as ωQ(1-α)e m , the negative externality of carbon emissions when CO2 reuse is not considered is ωQe m The negative externality of carbon emissions from transport carriers is ωQe t ; Among them, ω represents the negative externality coefficient of carbon emissions generated by producing or transporting a unit of product, ω>0;

[0040] S20, assuming that the maximum initial carbon emission quota allocated by the government to steel manufacturers is K m The maximum initial carbon emission quota allocated to the transport carrier is K t , K m , K t The value of is calculated by the free allocation method; all parameters in the model are time-independent constants; and it is assumed that the carbon quota trading price is higher than the carbon price baseline, that is, the carbon emissions obtained through carbon quota trading are not subject to carbon tax.

[0041] Further, step S2 includes:

[0042] S21. Construct a decentralized emission reduction decision model for external carbon trading based on CO2 reuse, and use the HJB equation to solve the equilibrium strategy;

[0043] S22. Construct a centralized emission reduction decision model for external carbon trading based on CO2 reuse, and use the HJB equation to solve the equilibrium strategy;

[0044] S23. Construct a centralized emission reduction decision-making model for internal carbon trading without considering CO2 reuse, and design a balance strategy;

[0045] S24. Construct a two-way cost-sharing contract model for external carbon trading without considering CO2 reuse, and design an equilibrium strategy.

[0046] Furthermore, step S21 specifically includes:

[0047] S211. Steel manufacturers decide on their own emission reduction efforts E m (t), transport carriers decide their own emission reduction efforts based on the manufacturer’s decision E t (t), the decision-making goal is to maximize the interests of each party; for the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading costs are P 1m ((1-α)e m Q m ), P 1t (e t Q t ), for the convenience of writing, some t representing the time is omitted in the model, and the following models are applicable, so the decision model is as follows:

[0048]

[0049]

[0050] in, represents the profit present value function of the steel manufacturer in the decentralized emission reduction decision model of external carbon trading; represents the profit present value function of the transport carrier in the decentralized emission reduction decision model of external carbon trading; π m represents the marginal profit per unit of steel manufacturer, π m >0;π t represents the marginal profit of the transport carrier, π t >0;

[0051] S212. The Hamilton-Jacobi-Bellman (HJB) equation is used to solve the differential game problem, and then the equilibrium strategies of manufacturers and retailers are obtained. According to the Stackelberg game sequence, the transport carrier as the follower takes the steel manufacturer's emission reduction efforts as a given parameter E m(t), and use this to decide the optimal emission reduction effort level E t (t), as follows:

[0052] The equilibrium strategies of the steel manufacturer and the transport carrier are:

[0053]

[0054]

[0055]

[0056] Among them, γ m The coefficient that represents the impact of steel manufacturers’ emission reduction efforts on the emission reduction degree of the steel supply chain, γ m >0; ρ represents the discount rate, ρ>0;

[0057] The optimal trajectory function for carbon emission reduction in the steel supply chain is:

[0058]

[0059] Among them, A D = -δ,

[0060] The optimal profit present value functions of the steel manufacturer and the transport carrier are:

[0061]

[0062]

[0063]

[0064] Among them, e t It represents the carbon emission per unit product transported by the transport carrier, e t >0.

[0065] Further, step S22 specifically includes:

[0066] S221. In this game, steel manufacturers and transport carriers are considered as a whole, with the overall profit optimization of the steel supply chain as the decision-making goal. Manufacturers and carriers jointly determine their own emission reduction efforts. m (t) and E t (t); In view of the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading costs are P 1m ((1-α)e m Q m ), P 1t (et Q t ), the decision model is as follows:

[0067]

[0068] in, It represents the profit present value function of the steel supply chain in the centralized emission reduction decision model of external carbon trading;

[0069] S222. Use the Hamilton-Jacobi-Bellman equation to solve the differential game problem, as follows:

[0070] The equilibrium strategies of the steel manufacturer and the transport carrier are:

[0071]

[0072]

[0073]

[0074] The optimal trajectory function for carbon emission reduction in the steel supply chain is:

[0075]

[0076] Among them, A C = -δ,

[0077] The optimal profit present value functions of the steel supply chain are:

[0078]

[0079]

[0080] Further, step S23 specifically includes:

[0081] S231. Assume that under the carbon tax-carbon trading coordinated control policy, the steel manufacturer still has insufficient carbon quota after emission reduction, while the transport carrier has surplus quota through emission reduction and can meet the quota demand of the steel manufacturer; the steel manufacturer and the transport carrier complete the transfer of carbon quota through internal transactions; the two jointly determine their own emission reduction efforts E m (t) and E t (t) The internal carbon trading price P2; for the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading cost is P2(e m Q m ), the decision model is as follows:

[0082]

[0083]

[0084] st.q t -eQ≥e m Q m

[0085] in, represents the profit present value function of the steel manufacturer in the centralized emission reduction decision model of internal carbon trading; It represents the profit present value function of the transport carrier in the centralized emission reduction decision model of internal carbon trading;

[0086] S232. In the centralized emission reduction decision-making model of internal carbon trading without considering CO2 reuse, the equilibrium strategy is as follows:

[0087] The equilibrium strategies of the steel manufacturer and the transport carrier are:

[0088]

[0089]

[0090]

[0091]

[0092] The optimal trajectory function for carbon emission reduction in the steel supply chain is:

[0093]

[0094] Among them, A IC = -δ,

[0095] The optimal profit present value functions of the steel manufacturer and the transport carrier are:

[0096]

[0097]

[0098]

[0099] Further, step S24 specifically includes:

[0100] S241. Consider steel manufacturers and transport carriers as a whole, and make the decision to optimize the profits of steel manufacturers and transport carriers. In addition to jointly determining their own emission reduction efforts, manufacturers and carriers should also m (t) and E t(t), and jointly decide the proportion of costs λ m (t) and λ t (t); In view of the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading costs are P 1m (e m Q m ), P 1t (e t Q t ), the decision model is:

[0101]

[0102]

[0103] in, represents the profit present value function of the steel manufacturer in the external carbon trading two-way cost sharing contract model; It represents the profit present value function of the transport carrier in the two-way cost sharing contract model of external carbon trading;

[0104] S242. In the external carbon trading two-way cost sharing contract model without considering CO2 reuse, the equilibrium solution is as follows:

[0105] The equilibrium strategies of the steel manufacturer and the transport carrier are:

[0106]

[0107]

[0108]

[0109]

[0110] The optimal trajectory function for carbon emission reduction in the steel supply chain is:

[0111]

[0112] Among them, A S = -δ,

[0113] The optimal profit present value functions of the steel manufacturer and the transport carrier are:

[0114]

[0115]

[0116]

[0117] Further, step S4 specifically includes:

[0118] S41. Construct a government decision-making model for decentralized emission reduction based on external carbon trading for CO2 reuse. Under this model, the government decision-making issues are as follows:

[0119]

[0120]

[0121] In the decentralized emission reduction decision model of external carbon trading based on CO2 reuse, for the government, the optimal carbon tax rate and the optimal initial carbon quota equilibrium solution are:

[0122]

[0123] S42. Construct a government decision-making model for centralized emission reduction based on external carbon trading for CO2 reuse. Under this model, the government decision-making issues are as follows:

[0124]

[0125]

[0126] In the centralized emission reduction decision-making model of external carbon trading based on CO2 reuse, for the government, the equilibrium solution of the optimal carbon tax rate and the optimal initial carbon quota is:

[0127]

[0128] S43. Construct a government decision-making model for centralized emission reduction under internal carbon trading without considering CO2 reuse. Under this model, the government decision-making problem is as follows:

[0129]

[0130]

[0131] In the centralized decision-making model of internal carbon trading without considering CO2 reuse, for the government, the equilibrium relationship between the optimal carbon tax rate and the optimal initial carbon quota is:

[0132]

[0133] S44. Construct a government decision-making model for an external two-way cost-sharing contract without considering CO2 reuse. Under this model, the government decision-making problem is as follows:

[0134]

[0135] In the two-way cost-sharing contract model of external carbon trading without considering CO2 reuse, for the government, the equilibrium solution of the optimal carbon tax rate and the optimal initial carbon quota is:

[0136]

[0137] Compared with the prior art, the present invention has the following advantages:

[0138] 1. The present invention provides a steel supply chain emission reduction method under the carbon tax-carbon trading coordinated control policy. Under the carbon tax-carbon trading coordinated control policy, through a two-layer game study, an optimal coordinated emission reduction contract is designed for steel manufacturers and transport carriers, and the optimal carbon tax rate and initial carbon quota set by the government are determined.

[0139] 2. The present invention provides a steel supply chain emission reduction method under the carbon tax-carbon trading coordinated management policy. By constructing a game model between steel manufacturers and transportation carriers, it seeks to achieve the optimal collaborative decision-making between the two parties in emission reduction while pursuing corporate profit maximization.

[0140] 3. The present invention provides a steel supply chain emission reduction method under the carbon tax-carbon trading coordinated management policy, which aims to improve overall social welfare, constructs a Stackelberg game model, and determines the optimal carbon tax rate and initial carbon quota that the government should formulate in its low-carbon policy.

[0141] Based on the above reasons, the present invention can be widely promoted in the fields of steel supply chain industry, carbon emission reduction policy formulation, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0142] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0143] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0144] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0145] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0146] The game subjects of the present invention are composed of three parties: the government, steel manufacturers and transport carriers. Steel manufacturers invest in emission reduction technologies and equipment and adopt CO2 recycling methods to reduce carbon emissions in steel manufacturing; transport carriers reduce carbon emissions in the steel transportation process by optimizing routes and investing in green transportation equipment; the government formulates carbon tax rates and initial carbon quotas based on the actual carbon emissions and emission reduction effects of enterprises.

[0147] The present invention establishes four double-layer game models. Considering that steel manufacturers can use the CO2 generated in the production process as a chemical raw material and put it into the steelmaking process, the recycled CO2 can offset part of the total carbon generated in the steel production process, thereby achieving the purpose of emission reduction. However, the CO2 emitted by the transport carrier directly enters the air and is difficult to collect and reuse. Therefore, based on this feature, the model of the present invention is divided into two types: based on CO2 reuse and not considering CO2 reuse (here CO2 reuse is only for steel manufacturers); in addition, considering that the implementation method of carbon trading policy in my country is divided into two modes: external carbon trading and internal carbon trading. In order to make the emission reduction strategy studied by the present invention more comprehensive in line with the current carbon emission reduction policy, these two carbon trading modes are introduced into the model, combined with the relevant research on existing emission reduction games, and referring to the idea of ​​establishing the game model, three emission reduction models to be established by the present invention are formed: an external carbon trading decentralized decision model based on CO2 reuse, an external carbon trading centralized decision model based on CO2 reuse, and an internal carbon trading centralized decision model without considering CO2 reuse. In addition, in order to reasonably share the emission reduction costs and improve supply chain efficiency to reduce carbon emissions, the present invention constructs a fourth emission reduction model: a two-way cost-sharing contract that does not consider CO2 reuse, further improving the collaborative emission reduction strategy between steel manufacturers and transportation carriers.

[0148] First, a decentralized decision-making model for external carbon trading based on CO2 reuse is established. In this model, the government sets carbon tax rates and initial carbon quotas for steel manufacturers and transport carriers. Steel manufacturers determine their own emission reduction efforts and CO2 recycling levels, and transport carriers determine their own emission reduction efforts based on the decisions of steel manufacturers. The two pay carbon taxes to the government and trade carbon quotas in the carbon market. For example, the government sets a carbon tax rate of 20%, allocates an initial carbon quota of 1,000 tons to steel manufacturers, and allocates 500 tons to transport carriers. Considering the cost of emission reduction and technical feasibility, steel manufacturers decide to reduce their original carbon emissions by 20% and recycle 80% of the remaining CO2. If emissions exceed the quota, additional quotas need to be purchased on the carbon market. Transport carriers decide to reduce their original carbon emissions by 15% based on the steel manufacturer's emission reduction and CO2 recycling. Similarly, if emissions exceed the quota, additional quotas need to be purchased on the carbon market.

[0149] Next, a centralized decision-making model for external carbon trading based on CO2 reuse is established. The decision-making process of this model is as follows: the government first decides on the carbon tax rate and the initial carbon quota. Steel manufacturers and transport carriers, as a whole, jointly decide on their respective emission reduction efforts and the CO2 recycling level of steel manufacturers. However, steel manufacturers and transport carriers must pay carbon taxes to the government separately and trade carbon quotas in the carbon market. For example, as in the decentralized model, the government sets the carbon tax rate and the initial carbon quota. Steel manufacturers and transport carriers jointly decide to reduce emissions by 25%, of which steel manufacturers are responsible for reducing emissions by 20% and recycling 80% of the remaining CO2 emissions, while transport carriers are responsible for reducing emissions by 5%. Although the two make decisions as a whole, they still need to pay carbon taxes to the government and trade quotas in the carbon market.

[0150] Subsequently, a centralized decision-making model for internal carbon trading without considering the reuse of CO2 is established. In this model, the government's decision-making content remains unchanged, and the carbon trading price is determined internally by steel manufacturers and transport carriers. The two complete carbon trading through agreement transfer and pay carbon taxes to the government respectively. For example, steel manufacturers and transport carriers jointly decide on emission reduction targets, such as a 25% reduction. The two parties negotiate internally to determine the carbon trading price, such as 80 yuan per ton of CO2, and complete carbon trading through agreement transfer.

[0151] Finally, a two-way cost-sharing contract model for external carbon trading without considering CO2 reuse is established. Based on the centralized decision-making model of external carbon trading, the steel manufacturer and the transport carrier need to decide the proportion of their mutual sharing of emission reduction costs, and other decision contents remain unchanged. For example, the two parties decide through an agreement that the steel manufacturer bears 60% of the emission reduction costs of the transport carrier, and the transport carrier bears 40% of the emission reduction costs of the steel manufacturer. As a whole, the two parties jointly decide on their respective emission reduction efforts, but each still needs to pay carbon taxes to the government and trade carbon quotas in the carbon market.

[0152] In order to solve the above problems, Figure 1 As shown, the present invention provides a method for reducing emissions in a steel supply chain under a carbon tax-carbon trading coordinated management policy, comprising:

[0153] S1. In order to optimize the collaborative emission reduction decision between the government, steel manufacturers and transport carriers, the model assumptions are given;

[0154] S2. Based on the given model assumptions, a differential game model of coordinated emission reduction between steel manufacturers and transport carriers is constructed to seek to achieve the optimal coordinated decision-making of both parties in emission reduction while pursuing the maximization of corporate profits;

[0155] S3. With the goal of improving overall social welfare, a Stackelberg game model between the government and the steel supply chain is constructed to determine the optimal carbon tax rate and initial carbon quota that the government should formulate in its low-carbon policy.

[0156] In specific implementation, as a preferred embodiment of the present invention, step S1 specifically includes:

[0157] S11. Assume that the emission reduction costs of steel manufacturers are:

[0158]

[0159]

[0160] Among them, C M (E m (t)) represents the emission reduction cost of upgrading the technology and equipment of steel manufacturers; E m (t) represents the degree of emission reduction efforts of steel manufacturers at time t, E m (t)≥0;η m represents the effort cost coefficient of the steel manufacturer, η m >0;C M (τ m(t)) represents the CO2 recycling and reuse emission reduction cost of steel manufacturers; α represents the CO2 recycling and reuse cost coefficient of steel manufacturers, α>0; τ(t) represents the CO2 recycling and reuse level of steel manufacturers at time t, τ(t)≥0;

[0161] Assume that the emission reduction cost for transport carriers is:

[0162]

[0163] Among them, C T (E t (t)) represents the emission reduction cost of transport carriers investing in green transport equipment; η t represents the transport carrier's effort cost coefficient, η t >0;E t (t) represents the degree of emission reduction efforts of transport carriers at time t, E t (t)≥0;

[0164] S12. Assuming that the degree of emission reduction in the steel supply chain is determined by the emission reduction efforts of steel manufacturers and transport carriers, which is a dynamic process, the emission reduction trajectory of the supply chain is expressed as:

[0165] x(t)=γ(E m (t)+τ(t))+γ t E t (t)-δx(t)

[0166] Where x(t) represents the degree of emission reduction in the steel supply chain at time t, and x(0) = x0 ≥ 0; γ t The coefficient that represents the impact of the transport carrier’s emission reduction efforts on the steel supply chain’s emission reduction efforts, γ t >0; δ represents the attenuation coefficient of the steel supply chain emission reduction when steel manufacturers and transport carriers do not take emission reduction measures, δ>0;

[0167] S13. Assuming that the concept of low carbon is gaining popularity, steel market customers will choose long-term partners based on the degree of carbon emission reduction in the supply chain. The emission reduction efforts of steel manufacturers and transport carriers will indirectly affect the demand for products through the emission reduction degree of the supply chain. The demand function is simplified to:

[0168] Q(t)=a+θx(t)

[0169] Where Q(t) represents the total output of steel products at time t; a represents the potential market demand, a>0; θ represents the coefficient of the impact of the enterprise's emission reduction efforts on demand, θ>0;

[0170] S14. Assume that all products produced by the steel manufacturer are transported by the transport carrier and the output Q is the total transport volume;

[0171] S15. The government imposes carbon taxes on steel manufacturers and transport carriers at different rates. Enterprises need to pay taxes on their initial carbon quotas. The carbon tax function is as follows:

[0172] t t (t) = β2(t)q t (t)

[0173] t m (t) = β1(t)q m (t)

[0174] Among them, t t (t) represents the total amount of carbon tax collected by the government from transport carriers at time t; m (t) represents the total amount of carbon tax collected by the government from steel manufacturers at time t; β1(t) represents the carbon tax rate levied by the government on steel manufacturers at time t; β2(t) represents the carbon tax rate levied by the government on transport carriers at time t; q m (t) represents the initial carbon quota of the steel manufacturer at time t; q t (t) represents the initial carbon quota of the transport carrier at time t;

[0175] S16. The initial carbon quota allocated by the government in a single period is an exogenous variable and cannot be transferred to the next period;

[0176] S17. In the model based on CO2 reuse, the CO2 generated by steel production is re-invested in production at a ratio of α. The actual carbon quota available to steel manufacturers in carbon trading is:

[0177] q m (t)-(1-α)Qe m

[0178] Among them, e m represents the carbon emissions per unit of product produced by steel manufacturers, e m >0;

[0179] S18. The transaction price of enterprises in the carbon market is determined by the carbon trading organization, while the internal carbon trading price is determined internally by steel manufacturers and transport carriers. Compared with steel manufacturers, transport carriers have relatively lower carbon emissions. In internal carbon trading, transport carriers are more likely to become sellers. In order to ensure that transport carriers choose to cooperate with steel manufacturers with the best emission reduction level, and to promote their own emission reduction in reverse, more carbon quota surpluses are sold, while ensuring the maximization of profits for both parties and the maximization of emission reduction in the steel supply chain, it is assumed that the internal carbon trading price is inversely proportional to the emission reduction efforts of steel manufacturers and directly proportional to the emission reduction efforts of transport carriers, as follows:

[0180] p1(t)>p2(t)

[0181]

[0182] Where p2(t) represents the internal carbon quota transaction price at time t, p2(t)≥0; σ represents the internal carbon quota transaction price coefficient, σ>0;

[0183] S19. The government's benefit is social welfare, which is composed of corporate profits, carbon tax revenue, and the negative effects of carbon emissions. For the government, the negative externality of carbon emissions when steel manufacturers consider CO2 reuse is expressed as ωQ(1-α)e m , the negative externality of carbon emissions when CO2 reuse is not considered is ωQe m The negative externality of carbon emissions from transport carriers is ωQe t ; Among them, ω represents the negative externality coefficient of carbon emissions generated by producing or transporting a unit of product, ω>0;

[0184] S20, assuming that the maximum initial carbon emission quota allocated by the government to steel manufacturers is K m The maximum initial carbon emission quota allocated to the transport carrier is K t , K m , K t The value of is calculated by the free allocation method (historical method / benchmark method); all parameters in the model are time-independent constants; at the same time, since the present invention studies the carbon tax-carbon trading coordinated management policy, the situation involved in this policy is relatively complicated, so it is assumed that the carbon quota trading price is higher than the carbon price baseline, that is, the carbon emissions obtained through carbon quota trading are not subject to carbon tax.

[0185] In specific implementation, as a preferred embodiment of the present invention, step S2 includes:

[0186] S21. Construct a decentralized emission reduction decision model for external carbon trading based on CO2 reuse, and use the HJB equation to solve the equilibrium strategy;

[0187] S22. Construct a centralized emission reduction decision model for external carbon trading based on CO2 reuse, and use the HJB equation to solve the equilibrium strategy;

[0188] S23. Construct a centralized emission reduction decision-making model for internal carbon trading without considering CO2 reuse, and design a balance strategy;

[0189] S24. Construct a two-way cost-sharing contract model for external carbon trading without considering CO2 reuse, and design an equilibrium strategy.

[0190] In specific implementation, as a preferred embodiment of the present invention, step S21 specifically includes:

[0191] S211. Steel manufacturers decide on their own emission reduction efforts E m (t), transport carriers decide their own emission reduction efforts based on the manufacturer’s decision E t (t), the decision-making goal is to maximize the interests of each party; for the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading costs are P 1m ((1-α)e m Q m ), P 1t (e t Q t ), for the convenience of writing, some t representing the time is omitted in the model, and the following models are applicable, so the decision model is as follows:

[0192]

[0193]

[0194] in, represents the profit present value function of the steel manufacturer in the decentralized emission reduction decision model of external carbon trading; represents the profit present value function of the transport carrier in the decentralized emission reduction decision model of external carbon trading; π m represents the marginal profit per unit of steel manufacturer, π m >0;π t represents the marginal profit of the transport carrier, π t >0;

[0195] S212. The Hamilton-Jacobi-Bellman (HJB) equation is used to solve the differential game problem, and then the equilibrium strategies of manufacturers and retailers are obtained. According to the Stackelberg game sequence, the transport carrier as the follower takes the steel manufacturer's emission reduction efforts as a given parameter E. m (t), and use this to decide the optimal emission reduction effort level E t (t), as follows:

[0196] The equilibrium strategies of the steel manufacturer and the transport carrier are:

[0197]

[0198]

[0199]

[0200] Among them, γ mThe coefficient that represents the impact of steel manufacturers’ emission reduction efforts on the emission reduction degree of the steel supply chain, γ m >0; ρ represents the discount rate, ρ>0;

[0201] The optimal trajectory function for carbon emission reduction in the steel supply chain is:

[0202]

[0203] Among them, A D = -δ,

[0204] The optimal profit present value functions of the steel manufacturer and the transport carrier are:

[0205]

[0206]

[0207]

[0208] Among them, e t It represents the carbon emission per unit product transported by the transport carrier, e t >0.

[0209] In specific implementation, as a preferred embodiment of the present invention, step S22 specifically includes:

[0210] S221. In this game, steel manufacturers and transport carriers are considered as a whole, with the overall profit optimization of the steel supply chain as the decision-making goal. Manufacturers and carriers jointly determine their own emission reduction efforts. m (t) and E t (t); In view of the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading costs are P 1m ((1-α)e m Q m ), P 1t (e t Q t ), the decision model is as follows:

[0211]

[0212] in, It represents the profit present value function of the steel supply chain in the centralized emission reduction decision model of external carbon trading;

[0213] S222. Use the Hamilton-Jacobi-Bellman equation to solve the differential game problem, as follows:

[0214] The equilibrium strategies of the steel manufacturer and the transport carrier are:

[0215]

[0216]

[0217]

[0218] The optimal trajectory function for carbon emission reduction in the steel supply chain is:

[0219]

[0220] Among them, A C = -δ,

[0221] The optimal profit present value functions of the steel supply chain are:

[0222]

[0223]

[0224] In specific implementation, as a preferred embodiment of the present invention, step S23 specifically includes:

[0225] S231. In the steel supply chain, steel manufacturers usually dominate the supply chain, and the carbon emissions of the steel manufacturing industry are about 1.6 times that of the transportation industry. Therefore, under the low-carbon policy, steel manufacturers are under greater pressure to reduce carbon emissions, which creates opportunities for transportation companies, especially small and medium-sized transportation companies, to cooperate with steel manufacturers. Before the rise of the trend of carbon control and emission reduction, freight was the decisive competitiveness of transportation carriers, but now carbon emissions have become a new generation of cooperation chips. Transportation carriers can transfer their remaining carbon emission rights to steel manufacturers that cooperate with them through internal carbon trading, thereby establishing a stable supply chain strategic cooperation relationship. Therefore, assuming that under the carbon tax-carbon trading coordinated control policy, steel manufacturers still have insufficient carbon quotas after emission reduction, and transportation carriers have quota surpluses through emission reductions and can meet the quota needs of steel manufacturers; steel manufacturers and transportation carriers complete the transfer of carbon quotas through internal transactions; the two jointly determine the extent of their own emission reduction efforts E m (t) and E t (t) The internal carbon trading price P2; for the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading cost is P2(e m Q m ), the decision model is as follows:

[0226]

[0227]

[0228] sq t -eQ≥e m Q m

[0229] in, represents the profit present value function of the steel manufacturer in the centralized emission reduction decision model of internal carbon trading; It represents the profit present value function of the transport carrier in the centralized emission reduction decision model of internal carbon trading;

[0230] S232. In the centralized emission reduction decision-making model of internal carbon trading without considering CO2 reuse, the equilibrium strategy is as follows:

[0231] The equilibrium strategies of the steel manufacturer and the transport carrier are:

[0232]

[0233]

[0234]

[0235]

[0236] The optimal trajectory function for carbon emission reduction in the steel supply chain is:

[0237]

[0238] Among them, A IC = -δ,

[0239] The optimal profit present value functions of the steel manufacturer and the transport carrier are:

[0240]

[0241]

[0242]

[0243] In specific implementation, as a preferred embodiment of the present invention, step S24 specifically includes:

[0244] S241. Consider steel manufacturers and transport carriers as a whole, and make the decision to optimize the profits of steel manufacturers and transport carriers. In addition to jointly determining their own emission reduction efforts, manufacturers and carriers should also m (t) and E t(t), and jointly decide the proportion of costs λ m (t) and λ t (t); In view of the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading costs are P 1m (e m Q m ), P 1t (e t Q t ), the decision model is:

[0245]

[0246]

[0247] in, represents the profit present value function of the steel manufacturer in the external carbon trading two-way cost sharing contract model; It represents the profit present value function of the transport carrier in the two-way cost sharing contract model of external carbon trading;

[0248] S242. In the external carbon trading two-way cost sharing contract model without considering CO2 reuse, the equilibrium solution is as follows:

[0249] The equilibrium strategies of the steel manufacturer and the transport carrier are:

[0250]

[0251]

[0252]

[0253]

[0254] The optimal trajectory function for carbon emission reduction in the steel supply chain is:

[0255]

[0256] Among them, A S = -δ,

[0257] The optimal profit present value functions of the steel manufacturer and the transport carrier are:

[0258]

[0259]

[0260]

[0261] In specific implementation, as a preferred embodiment of the present invention, step S4 specifically includes:

[0262] S41. Construct a government decision-making model for decentralized emission reduction based on external carbon trading for CO2 reuse. Under this model, the government decision-making issues are as follows:

[0263]

[0264]

[0265] In the decentralized emission reduction decision model of external carbon trading based on CO2 reuse, for the government, the optimal carbon tax rate and the optimal initial carbon quota equilibrium solution are:

[0266]

[0267] S42. Construct a government decision-making model for centralized emission reduction based on external carbon trading for CO2 reuse. Under this model, the government decision-making issues are as follows:

[0268]

[0269]

[0270] In the centralized emission reduction decision-making model of external carbon trading based on CO2 reuse, for the government, the equilibrium solution of the optimal carbon tax rate and the optimal initial carbon quota is:

[0271]

[0272] S43. Construct a government decision-making model for centralized emission reduction under internal carbon trading without considering CO2 reuse. Under this model, the government decision-making problem is as follows:

[0273]

[0274]

[0275] In the centralized decision-making model of internal carbon trading without considering CO2 reuse, for the government, the equilibrium relationship between the optimal carbon tax rate and the optimal initial carbon quota is:

[0276]

[0277] S44. Construct a government decision-making model for an external two-way cost-sharing contract without considering CO2 reuse. Under this model, the government decision-making problem is as follows:

[0278]

[0279] In the two-way cost-sharing contract model of external carbon trading without considering CO2 reuse, for the government, the equilibrium solution of the optimal carbon tax rate and the optimal initial carbon quota is:

[0280]

[0281] Comparative Example 1: Design of collaborative emission reduction contracts under decentralized and centralized decision-making for external carbon trading based on CO2 reuse

[0282] Table 1 Comparative analysis content table

[0283]

[0284] Through comparative analysis, it can be found that when the decision-making targets are the emission reduction efforts of steel manufacturers and transport carriers, the CO2 reuse level of steel manufacturers, and the carbon emission reduction trajectory of the steel supply chain, centralized emission reduction decisions are always better than decentralized emission reduction decisions. When the decision-making targets are the profits of steel manufacturers and transport carriers, decentralized emission reduction decisions are better than centralized emission reduction decisions.

[0285] Therefore, steel manufacturers and transport carriers can choose to cooperate in the centralized emission reduction decision based on external carbon trading of CO2 reuse, so that they and the entire steel supply chain can achieve a more ideal carbon control and emission reduction level. However, the profits obtained by steel manufacturers and transport carriers in the centralized emission reduction decision are not optimal. In order to improve this problem and make the two choose the centralized emission reduction decision as the coordinated emission reduction contract to achieve the optimal equilibrium strategy for the four decision-making goals, the government can provide subsidies to steel manufacturers and transport carriers, increase their profit income, and stimulate steel manufacturers and transport carriers to choose the centralized emission reduction decision for cooperation.

[0286] Comparative Example 2: Design of collaborative emission reduction contract based on external carbon trading based on CO2 reuse and internal carbon trading decision without considering CO2 reuse

[0287] Table 2 Comparative analysis content table

[0288]

[0289] Through comparative analysis, the conclusions are shown in Table 3. For steel manufacturers and transport carriers, there are three decision-making objectives for comparison, namely, the emission reduction efforts of steel manufacturers and transport carriers, the carbon emission reduction trajectory of the steel supply chain, and the profits of steel manufacturers and transport carriers. As can be seen from the table below, when the decision-making objectives are the emission reduction efforts of steel manufacturers and transport carriers or the carbon emission reduction trajectory of the steel supply chain in which emission reduction decision is better, the conclusions are related to the value of H. H means the sum of the unit marginal profits of the products of steel manufacturers and transport carriers after deducting the external carbon transaction costs per unit product, that is, H represents the marginal profit that can be obtained per unit product in the steel supply chain after deducting the external carbon transaction costs per unit product. When the steel manufacturers and transport carriers know the value of H, they can use the value of H as the selection condition for the collaborative emission reduction contract. According to the range of the value of H, it can be obtained that the decision-making objective is better in which emission reduction decision, and the optimal collaborative emission reduction contract for steel manufacturers and transport carriers is determined. The size of the profits of steel manufacturers and transport carriers in the two decisions is directly related to the carbon emission reduction trajectory x of the steel supply chain, and has nothing to do with the value of H. Therefore, when the decision-making goals of the two are to optimize their respective profits, the carbon emission reduction trajectory of the steel supply chain should be used as the selection condition for the collaborative emission reduction contract, and the optimal collaborative emission reduction contract between steel manufacturers and transport carriers can be determined based on the conditions satisfied by the carbon emission reduction trajectory of the steel supply chain.

[0290] Table 3 Comparative analysis results

[0291]

[0292] Comparative Example 3:

[0293] Design of collaborative emission reduction contract under the comparison between centralized decision-making of internal carbon trading without considering CO2 reuse and two-way cost sharing contract of external carbon trading

[0294] Table 4 Comparative analysis content

[0295]

[0296] Through comparative analysis, the conclusions are shown in Table 5. When the decision goal is to maximize the emission reduction efforts of steel manufacturers and transport carriers, or the carbon emission reduction trajectory of the steel supply chain is optimal, The values ​​of and H directly affect the selection results of the collaborative emission reduction contract. represents the equilibrium strategy of the internal carbon quota trading price coefficient, and H still represents the marginal profit per unit product in the steel supply chain after deducting the external carbon trading cost per unit product. At this time, steel manufacturers and transport carriers need to comprehensively consider when choosing a cooperation strategy. As well as the value of H, this is used as the judgment condition of the collaborative emission reduction contract, so as to determine the collaborative emission reduction contract that is advantageous to both parties. When steel manufacturers and transport carriers use the profits of both parties as their decision-making goals, the conclusions obtained are directly related to the carbon emission reduction trajectory x of the steel supply chain, and It has nothing to do with the value of H. Therefore, when the decision-making objectives of the two parties are to optimize their respective profits, the carbon emission reduction trajectory x of the steel supply chain should be used as the selection condition for the collaborative emission reduction contract, and the optimal collaborative emission reduction contract between the steel manufacturer and the transport carrier can be determined based on the conditions satisfied by the carbon emission reduction trajectory x of the steel supply chain.

[0297] Table 5 Comparative analysis results

[0298]

[0299]

[0300] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for reducing emissions in the steel supply chain under a carbon tax-carbon trading collaborative management policy, characterized in that: include: S1. In order to optimize the collaborative emission reduction decision between the government, steel manufacturers and transport carriers, the model assumptions are given; S2. Based on the given model assumptions, a differential game model of coordinated emission reduction between steel manufacturers and transport carriers is constructed to seek to achieve the optimal coordinated decision-making of both parties in emission reduction while pursuing the maximization of corporate profits; S3. With the goal of improving overall social welfare, a Stackelberg game model between the government and the steel supply chain is constructed to determine the optimal carbon tax rate and initial carbon quota that the government should formulate in its low-carbon policy.

2. The method for reducing emissions in the steel supply chain under the carbon tax-carbon trading coordinated management policy according to claim 1 is characterized in that: Step S1 specifically includes: S11. Assume that the emission reduction costs of steel manufacturers are: Among them, C M (E m (t)) represents the emission reduction cost of upgrading the technology and equipment of steel manufacturers; E m (t) represents the degree of emission reduction efforts of steel manufacturers at time t, E m (t)≥0;η m represents the effort cost coefficient of the steel manufacturer, η m >0;C M (τ m (t)) represents the CO2 recycling and reuse emission reduction cost of steel manufacturers; α represents the CO2 recycling and reuse cost coefficient of steel manufacturers, α>0; τ(t) represents the CO2 recycling and reuse level of steel manufacturers at time t, τ(t)≥0; Assume that the emission reduction cost for transport carriers is: Among them, C T (E t (t)) represents the emission reduction cost of transport carriers investing in green transport equipment; η t represents the transport carrier's effort cost coefficient, η t >0;E t (t) represents the degree of emission reduction efforts of transport carriers at time t, E t (t)≥0; S12. Assuming that the degree of emission reduction in the steel supply chain is determined by the emission reduction efforts of steel manufacturers and transport carriers, which is a dynamic process, the emission reduction trajectory of the supply chain is expressed as: x(t)=γ(E m (t)+τ(t))+γ t E t (t)-δx(t) Where x(t) represents the degree of emission reduction in the steel supply chain at time t, and x(0) = x0 ≥ 0; γ t The coefficient that represents the impact of the transport carrier’s emission reduction efforts on the steel supply chain’s emission reduction efforts, γ t >0; δ represents the attenuation coefficient of the steel supply chain emission reduction when steel manufacturers and transport carriers do not take emission reduction measures, δ>0; S13. Assuming that the concept of low carbon is gaining popularity, steel market customers will choose long-term partners based on the degree of carbon emission reduction in the supply chain. The emission reduction efforts of steel manufacturers and transport carriers will indirectly affect the demand for products through the emission reduction degree of the supply chain. The demand function is simplified to: Q(t)=a+θx(t) Where Q(t) represents the total output of steel products at time t; a represents the potential market demand, a>0; θ represents the coefficient of the impact of the enterprise's emission reduction efforts on demand, θ>0; S14. Assume that all products produced by the steel manufacturer are transported by the transport carrier and the output Q is the total transport volume; S15. The government imposes carbon taxes on steel manufacturers and transport carriers at different rates. Enterprises need to pay taxes on their initial carbon quotas. The carbon tax function is as follows: t t (t)=β2(t)q t (t) t m (t)=β1(t)q m (t) Among them, t t (t) represents the total amount of carbon tax collected by the government from transport carriers at time t; m (t) represents the total amount of carbon tax collected by the government from steel manufacturers at time t; β1(t) represents the carbon tax rate levied by the government on steel manufacturers at time t; β2(t) represents the carbon tax rate levied by the government on transport carriers at time t; q m (t) represents the initial carbon quota of the steel manufacturer at time t; q t (t) represents the initial carbon quota of the transport carrier at time t; S16. The initial carbon quota allocated by the government in a single period is an exogenous variable and cannot be transferred to the next period; S17. In the model based on CO2 reuse, the CO2 generated by steel production is re-invested in production at a ratio of α. The actual carbon quota available to steel manufacturers in carbon trading is: q m (t)-(1-α)Qe m Among them, e m represents the carbon emissions per unit of product produced by steel manufacturers, e m >0; S18. Assume that the internal carbon trading price is inversely proportional to the emission reduction efforts of steel manufacturers and directly proportional to the emission reduction efforts of transport carriers, as follows: p1(t)>p2(t) Where p2(t) represents the internal carbon quota transaction price at time t, p2(t)≥0; σ represents the internal carbon quota transaction price coefficient, σ>0; S19. For the government, the negative externality of carbon emissions when steel manufacturers consider CO2 reuse is expressed as ωQ(1-α)e m , the negative externality of carbon emissions when CO2 reuse is not considered is ωQe m The negative externality of carbon emissions from transport carriers is ωQe t ; Among them, ω represents the negative externality coefficient of carbon emissions generated by producing or transporting a unit of product, ω>0; S20, assuming that the maximum initial carbon emission quota allocated by the government to steel manufacturers is K m The maximum initial carbon emission quota allocated to the transport carrier is K t , K m , K t The value of is calculated by the free allocation method; all parameters in the model are time-independent constants; and it is assumed that the carbon quota trading price is higher than the carbon price baseline, that is, the carbon emissions obtained through carbon quota trading are not subject to carbon tax.

3. The method for reducing emissions in the steel supply chain under the carbon tax-carbon trading coordinated management policy according to claim 1 is characterized in that: Step S2 comprises: S21. Construct a decentralized emission reduction decision model for external carbon trading based on CO2 reuse, and use the HJB equation to solve the equilibrium strategy; S22. Construct a centralized emission reduction decision model for external carbon trading based on CO2 reuse, and use the HJB equation to solve the equilibrium strategy; S23. Construct a centralized emission reduction decision-making model for internal carbon trading without considering CO2 reuse, and design a balance strategy; S24. Construct a two-way cost-sharing contract model for external carbon trading without considering CO2 reuse, and design an equilibrium strategy.

4. The method for reducing emissions from a steel supply chain under a carbon tax-carbon trading collaborative management policy according to claim 1, characterized in that: Step S21 specifically includes: S211. Steel manufacturers decide on their own emission reduction efforts E m (t), transport carriers decide their own emission reduction efforts based on the manufacturer’s decision E t (t), the decision-making goal is to maximize the interests of each party; for the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading costs are P 1m ((1-α)e m Q m ), P 1t (e t Q t ), for the convenience of writing, some t representing the time is omitted in the model, and the following models are applicable, so the decision model is as follows: in, represents the profit present value function of the steel manufacturer in the decentralized emission reduction decision model of external carbon trading; represents the profit present value function of the transport carrier in the decentralized emission reduction decision model of external carbon trading; π m represents the marginal profit per unit of steel manufacturer, π m >0;π t represents the marginal profit of the transport carrier, π t >0; S212. The Hamilton-Jacobi-Bellman (HJB) equation is used to solve the differential game problem, and then the equilibrium strategies of manufacturers and retailers are obtained. According to the Stackelberg game sequence, the transport carrier as the follower takes the steel manufacturer's emission reduction efforts as a given parameter E m (t), and use this to decide the optimal emission reduction effort level E t (t), as follows: The equilibrium strategies of the steel manufacturer and the transport carrier are: Among them, γ m The coefficient that represents the impact of steel manufacturers’ emission reduction efforts on the emission reduction degree of the steel supply chain, γ m >0; ρ represents the discount rate, ρ>0; The optimal trajectory function for carbon emission reduction in the steel supply chain is: Among them, A D =-d, The optimal profit present value functions of the steel manufacturer and the transport carrier are: Among them, e t It represents the carbon emission per unit product transported by the transport carrier, e t >0.

5. The method for reducing emissions in the steel supply chain under the carbon tax-carbon trading coordinated management policy according to claim 1 is characterized in that: Step S22 specifically includes: S221. In this game, steel manufacturers and transport carriers are considered as a whole, with the overall profit optimization of the steel supply chain as the decision-making goal. Manufacturers and carriers jointly determine their own emission reduction efforts. m (t) and E t (t); In view of the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading costs are P 1m ((1-α)e m Q m ), P 1t (e t Q t ), the decision model is as follows: in, It represents the profit present value function of the steel supply chain in the centralized emission reduction decision model of external carbon trading; S222. Use the Hamilton-Jacobi-Bellman equation to solve the differential game problem, as follows: The equilibrium strategies of the steel manufacturer and the transport carrier are: The optimal trajectory function for carbon emission reduction in the steel supply chain is: Among them, A C =-d, The optimal profit present value functions of the steel supply chain are:

6. The method for reducing emissions from the steel supply chain under the carbon tax-carbon trading coordinated management policy according to claim 1 is characterized in that: Step S23 specifically includes: S231. Assume that under the carbon tax-carbon trading coordinated control policy, the steel manufacturer still has insufficient carbon quota after emission reduction, while the transport carrier has surplus quota through emission reduction and can meet the quota demand of the steel manufacturer; the steel manufacturer and the transport carrier complete the transfer of carbon quota through internal transactions; the two jointly determine their own emission reduction efforts E m (t) and E t (t) The internal carbon trading price P2; for the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading cost is P2(e m Q m ), the decision model is as follows: s.t.q t -e t Q≥e m Q-q m in, represents the profit present value function of the steel manufacturer in the centralized emission reduction decision model of internal carbon trading; It represents the profit present value function of the transport carrier in the centralized emission reduction decision model of internal carbon trading; S232. In the centralized emission reduction decision-making model of internal carbon trading without considering CO2 reuse, the equilibrium strategy is as follows: The equilibrium strategies of the steel manufacturer and the transport carrier are: The optimal trajectory function for carbon emission reduction in the steel supply chain is: Among them, A IC =-d, The optimal profit present value functions of the steel manufacturer and the transport carrier are:

7. The method for reducing emissions from the steel supply chain under the carbon tax-carbon trading coordinated management policy according to claim 1 is characterized in that: Step S24 specifically includes: S241. Consider steel manufacturers and transport carriers as a whole, and make the decision to optimize the profits of steel manufacturers and transport carriers. In addition to jointly determining their own emission reduction efforts, manufacturers and carriers should also m (t) and E t (t), and jointly decide the proportion of costs λ m (t) and λ t (t); In view of the carbon tax-carbon trading coordinated control policy, the initial carbon quota obtained by the enterprise is taxed t m (t), t t (t), the carbon trading costs are P 1m (e m Q m ), P 1t (e t Q t ), the decision model is: in, represents the profit present value function of the steel manufacturer in the external carbon trading two-way cost sharing contract model; It represents the profit present value function of the transport carrier in the two-way cost-sharing contract model of external carbon trading; S242. In the external carbon trading two-way cost sharing contract model without considering CO2 reuse, the equilibrium solution is as follows: The equilibrium strategies of the steel manufacturer and the transport carrier are: The optimal trajectory function for carbon emission reduction in the steel supply chain is: Among them, A S =-d, The optimal profit present value functions of the steel manufacturer and the transport carrier are:

8. The method for reducing emissions from the steel supply chain under the carbon tax-carbon trading coordinated management policy according to claim 1 is characterized in that: Step S4 specifically includes: S41. Construct a government decision-making model for decentralized emission reduction based on external carbon trading for CO2 reuse. Under this model, the government decision-making issues are as follows: In the decentralized emission reduction decision model of external carbon trading based on CO2 reuse, for the government, the optimal carbon tax rate and the optimal initial carbon quota equilibrium solution are: S42. Construct a government decision-making model for centralized emission reduction based on external carbon trading for CO2 reuse. Under this model, the government decision-making issues are as follows: In the centralized emission reduction decision-making model of external carbon trading based on CO2 reuse, for the government, the equilibrium solution of the optimal carbon tax rate and the optimal initial carbon quota is: S43. Construct a government decision-making model for centralized emission reduction under internal carbon trading without considering CO2 reuse. Under this model, the government decision-making problem is as follows: In the centralized decision-making model of internal carbon trading without considering CO2 reuse, for the government, the equilibrium relationship between the optimal carbon tax rate and the optimal initial carbon quota is: S44. Construct a government decision-making model for an external two-way cost-sharing contract without considering CO2 reuse. Under this model, the government decision-making problem is as follows: In the two-way cost-sharing contract model of external carbon trading without considering CO2 reuse, for the government, the equilibrium solution of the optimal carbon tax rate and the optimal initial carbon quota is:

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