Construction waste is an issue that has attracted increasing worldwide attention recently. With the rapid development of socioeconomic and urbanization in China, the building industry has emerged as a pillar of the national economy. In particular, a large number of raw materials are used and massive construction waste is generated along a gradient of increasing urbanization, resulting in environmental pollution and scarcity of nature resource. At present, construction waste recycling has been proven to be the most effective method of managing construction trash.
The government agencies, waste recyclers, and waste producers are members of the construction waste recycling system. In this system, the government agency aims to increase the proportion of implementing construction waste recycling to realize and promote construction sustainability development. As for waste recyclers and producers, they try to maximize their interests. It is worth noting that if waste producers do not implement construction waste recycling, the construction waste will increase, which will further pollute the environment and lead to higher environmental management costs. Therefore, strategies from waste recyclers and producers play an essential role for the environment and eco-system, the more these two enterprises adopt waste recycling, the less pollution led by construction waste. Following Ref. [2], this work first introduces a more precise multi-agent evolutionary model by introducing environmental benefits and penalties for waste recyclers and producers, respectively. In particular, it is assumed that government is more prone to support waste recyclers than waste producers. Then the evolution behavior of three participants is analyzed during the procedure of construction waste recycling through the evolutionary game framework. The three-party game tree of government agencies, waste recyclers, and waste producers is shown in Figure 1.
Figure 1. The three-party game tree of government agencies, waste recyclers, and waste producers
Based on Figure 1, the following replicator dynamics equation is given:
$$F(x)=x(1-x)\left[y z\left(-G_{1}-F_1-F_2\right)-y S_{j}-z S_{s}+\left(G+G_{1}+F_1+F_2-C_{g}\right)\right]$$
$$F(y)=y(1-y)\left\{-x z S_j+x S_{j}+z\left[(1-\lambda) R-\left(C-\eta C_{1}\right)-P_{j}+\Delta C_{j}\right]+x z F_1-\Delta C_{j}\right\} $$
$$F(z)=z(1-z)\left[x\left(S_{s}+F_2\right)+y\left(\lambda R+C_{0}\right)-C_{0}-\eta C_{1}\right] $$
In addition, it is obvious that 1-x, 1-y, and 1-z are non-negative, so they will not influence the results of the evolution analysis. Next, the replicator dynamic formulas of government agencies, waste recyclers, and waste producers can be rewritten as:
$$F(x)=dx / dt = x\left[y z\left(-G_{1}-F_1-F_2\right)-y S_{j}-z S_{s}+\left(G+G_{1}+F_1+F_2-C_{g}\right)\right]$$
$$F(y)=dy / dt = y\left\{-x z S_j+x S_{j}+z\left[(1-\lambda) R-\left(C-\eta C_{1}\right)-P_{j}+\Delta C_{j}\right]+x z F_1-\Delta C_{j}\right\} $$
$$F(z)=dz / dt = z\left[x\left(S_{s}+F_2\right)+y\left(\lambda R+C_{0}\right)-C_{0}-\eta C_{1}\right] $$
To the best of researchers' knowledge, there exist high uncertainty in the game among the government agencies, waste recyclers, and waste producers because of the complexity of the external environment. To this end, the different participants will have different strategic selections because of their profits. In particular, there always exists random noise in the replicator dynamics formula, leading to bad performance for the deterministic evolutionary game framework, since the existing uncertainty around different participants. Therefore, it is necessary to take random noise into account in the tripartite game model. To further improve the previous deterministic game model, in this entry, the replicator dynamic formula is combined with Gaussian white noise, which results in the multi-agent stochastic evolutionary game framework, as follows:
$$dx(t)= \left[y z\left(-G_{1}-F_1-F_2\right)-y S_{j}-z S_{s}+\left(G+G_{1}+F_1+F_2-C_{g}\right)\right]x(t)dt +\delta x(t)d\omega(t) $$
$$dy(t) = \left\{-x z S_j+x S_{j}+z\left[(1-\lambda) R-\left(C-\eta C_{1}\right)-P_{j}+\Delta C_{j}\right]+x z F_1-\Delta C_{j}\right\}y(t)dt+\delta y(t)d\omega(t) $$
$$dz(t) = \left[x\left(S_{s}+F_2\right)+y\left(\lambda R+C_{0}\right)-C_{0}-\eta C_{1}\right]z(t)dt+\delta z(t)d\omega(t) $$
Figure 2 shows the results that how noise intensity affects the trajectory of the evolutionary game model. It can be observed that the uncertainty will bring random disturbance into the evolution process and then affect the evolution process. In addition, it also can be seen that the higher the noise intensity is, the more fluctuation exists in the evolutionary trajectories. This means the uncertainty can affect the strategy choice of the government agencies, waste recyclers, and waste producers.
Figure 2. Multi-agent dynamic evolutionary trajectories under different noise intensities
Facilitating the implementation of construction waste recycling is the primary basis to realize construction sustainability and it has a great practical significance for the quality improvement of construction waste recycling. In this entry, the three-party stochastic evolutionary game framework is proposed for construction waste recycling, making the payoff matrix and combining the Gaussian white noise with the replicator dynamic formula. Then the random Taylor expansion is used to solve the numerical approximation, and finally, the numerical simulations are conducted to study the dynamic evolution between the government agencies, waste recyclers, and waste producers. The main conclusions are as follows: (1) Smaller sorting costs make, the group strategy more stable and effective. (2) Larger disposal costs make waste producers do not implement construction waste recycling. (3) The more waste producers put into disposing of the construction waste enthusiasm the waste recyclers recycle construction waste. (4) Based on the comparative analysis of Gaussian white noise intensity, the effect of uncertainty external environments brings the random disturbance into the evolution trajectory of different participants, which leads to fluctuation of a smooth curve. To evade strategy fluctuation for different participants, it is necessary to let government agencies actively guide the waste producers and waste recyclers.
In a brief, this entry investigated the tripartite stochastic evolutionary game model for construction waste recycling policies analysis, filling the multi-agent stochastic game study of construction waste recycling and offering a practical basis for different agencies to implement construction waste recycling.
This entry is adapted from the peer-reviewed paper 10.3390/su14063702