Based on the analysis results of Section 2.1 and 2.2, a three-level supply chain is simulated. The raw material flow between suppliers, purchasers and green energy plants is carried out by different means. Green energy plants could produce products by different processes. The carbon emission cost is taken as a part of the supply chain cost. Considering the raw material output and the constraints of the national energy-saving and emission-limiting policies, a single objective optimization decision-making problem, i.e. the minimization of the total cost of the raw material supply chain, is proposed. The following assumptions are made:

Only the operation of the supply chain within one cycle is considered;

The discrepancy caused by external factors such as natural disasters and climate change will not be considered.

Green energy plants are located in the central area of the region and collected within a certain radius of the region;

Green energy procurement and product sales channels are fixed.

The rental of premises and warehouses will remain unchanged.

The demand of the processing plant can be satisfied without importing raw materials from other fields.

Carbon emissions are only related to transport distance among different transport nodes.

According to the above assumptions, the complexity and the modeling time of building the renewable green building’s energy supply chain model are reduced. The construction of renewable green building energy supply chain model based on LCA is completed. The detailed process is as follows:

1) Establishment of an economic goal oriented model:

Depreciation cost of fixed assets:

$$INV=EQU+HOU+PLA$$(2)$$BINV=\frac{INV}{T}$$(3)where *NV* represents the fixed assets of green building energy, *BINV* represents the depreciation cost of fixed assets, *EQU* represents the purchase cost of green building’s equipment, *HOU* represents the construction cost of green building, *PLA* represents the rental cost of green building’s energy sites, *T* represents the service life.

Procurement cost is:

$$\begin{array}{r}PUR=\sum {N}_{g}\cdot {U}_{g}\end{array}$$(4)where *PUR* represents the cost of green building’s energy procurement, *N*_{g} represents the corresponding amount of *g* green building’s energy procurement, *U*_{g} represents the unit cost of *g* green building’s energy procurement. The cost of renewable green building’s energy procurement is related to the purchase price and quantity of energy units.

Transportation cost *TRA*:

$$\begin{array}{r}TRA=TR{A}_{1,g}+TR{A}_{2,g}+TR{A}_{3,g}\end{array}$$(5)where *TRA*_{1,g}, *TRA*_{2,g} and *TRA*_{3,g} represent the transportation of *g* kinds of renewable green building’s energy transportation costs mainly include three parts: transportation, loading and unloading costs and oil charges.

Inventory cost *STO*:

$$\begin{array}{r}STO=\sum \left(PR{E}_{g}\cdot ST{O}_{g}+ST{O}_{g}\cdot {S}_{g}\right)\end{array}$$(6)Where *PRE*_{g} represents the pretreatment cost of *g* green energy unit, *STO*_{g} represents the inventory of *g* green energy, *S*_{g} represents the inventory cost of *g* green energy unit.

The cost of taxation *TAX*:

$$\begin{array}{r}TAX=\sum {Q}_{h}{R}_{h}{P}_{o}\end{array}$$(7)where *Q*_{h} denotes the number of the *h*th green building’s energy product, *R *_{h} represents the unit price of the *h*th green building energy, and *P*_{o} represents the tax rate.

In summary, the total cost model *SC* of renewable green building’s energy supply chain is:

$$\begin{array}{r}SC=BINV+PUR+TRA+STO+CON+TAX+MB\end{array}$$(8)where, *CON* represents the daily management cost of green building’s energy, and *MB* represents the wages of workers.

2) Building the low carbon target oriented model

The carbon emission *C *_{o} of renewable green building’s energy in procurement sector is:

$$\begin{array}{r}{C}_{o}=\sum {D}_{g}\cdot {C}_{m,g}\end{array}$$(9)where *D*_{g} represents the transportation distance of *g* kinds of green energy, *C*_{m}_{,g} represents the carbon emission per unit distance of *g* kinds of green energy.

The carbon emission *C*_{y} of renewable green building’s energy in the transport link is:

$$\begin{array}{r}{C}_{y}={C}_{a}+{C}_{b}\end{array}$$(10)where *C*_{a}∞ stands for the carbon emissions during transportation and *C *_{b} represents carbon emissions during loading and unloading. Total carbon emissions are directly related to total green energy consumption during transportation, indirectly related to transport distance, transport volume and transport green energy consumption per unit [12].

The carbon emission *C *_{d} in storage link is:

$$\begin{array}{r}{C}_{d}=\sum STO\cdot {\omega}_{q}\cdot {T}_{q}\cdot {V}_{q}\end{array}$$(11)where *⍵*_{q} represents the potential value of greenhouse gas emission of *q*gases, *T*_{q}represents the time of greenhouse gas emission of *q*gases, and *V*_{q} represents the greenhouse gas emission rate of *q* gases. Carbon emissions from storage links are related to energy storage, greenhouse gas emission rate and emission time [14, 15, 16, 17, 18, 19, 20, 21].

In summary, the greenhouse gas emission model *C *_{to} of renewable green building’s energy supply chain is:

$$\begin{array}{r}{C}_{to}={C}_{o}+{C}_{y}+{C}_{d}+{C}_{f}+{C}_{q}\end{array}$$(12)where *C *_{f} represents carbon emissions in production, and *C*_{q} represents carbon emissions from workers’ activities. Through the consideration of air pollution, we can reduce the pollution index of renewable green building’s energy supply.

According to the analysis and calculation of 1) and 2), the building’s energy supply chain model oriented by the comprehensive objective of economy and low carbon can be expressed as follows:

$$\begin{array}{r}Z=\lambda \left[SC+{C}_{to}\cdot {P}_{C}\right]s\end{array}$$(13)In Eq. (13), *λ* represents the impact parameters of normal operation of the renewable green building’s energy supply chain, the value is controlled at [1.3, 1.4], renewable green building’s energy supply chain is the most perfect, with the highest modeling accuracy. *Z* represents the renewable green building’s energy supply chain model based on LCA.

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