In 2015, the Paris Agreement was established with the aim to strengthen the global response in limiting the increase in the global average temperature. This can be achieved by, amongst other measures, lowering of CO2 emissions. The Paris Agreement was also signed by the Netherlands. Within the Netherlands, the construction sector has the largest environment impact of all sectors; accounting to 36% of the national CO2 emissions, 50% of the national material usage and 40% of the total energy consumption. Research has shown that implementing a CE in this sector may significantly lower these CO2 emissions and material usage. Despite the establishment of several national agreements aiming to accelerate the implementation of a CE in Dutch infrastructure projects, progress is slow. Several barriers are assumed to hamper this transition, while drivers may accelerate the transition towards a CE. This study aims to identify the barriers to and the drivers of the implementation of a CE in part of the Dutch construction sector; the infrastructure sector. The research question is “What are the barriers and drivers that respectively need to be overcome and enhanced in order to accelerate the implementation of a Circular Economy in Dutch infrastructure projects?”

Based on a review of the literature on barriers and drivers for the implementation of a CE in general and in the construction sector, a literature-based framework of CE barrier- and driver-categories was developed. This framework provided the basis in formulating the questions for the interviews. A total of 15 interviews were conducted with respondents from a diverse and balanced group of stakeholders in the infrastructure sector. Respondents were asked what they think are the barriers and drivers for the implementation of a CE in Dutch infrastructure projects. A total of 135 barriers and 72 drivers were identified during the interviews, which could be grouped in the categories of the literature-based framework. The most frequently mentioned barriers relate to the procurement of infrastructure projects, the aversion of risks and the higher costs of secondary or circular materials as compared to ‘virgin’ materials. The most frequently mentioned drivers often require the government to take action, and involved developing more binding legislation and regulation on the use and application of circular materials (at least to an extend) in infrastructure projects. Additionally, as the commissioner of the majority of infrastructure projects in the Netherlands, the government providing more room for circular innovations or pilot projects was mentioned as a driver.

While this study is novel in the sense that it is the first to provide an overview of the barriers and drivers for the implementation of CE in the context of infrastructure project, further search is required to determine how the identified barriers and drivers can respectively be overcome and enhanced. Additionally, further research to validate the applicability of the literature-based framework of CE barrier- and driver-categories in infrastructure projects in other countries is recommended.

The construction industry is a large generator of waste. The interest in improving the resource efficiency is growing. A move towards a Circular Economy (CE) has been assigned as the solution for a more efficient use of resources in the construction industry. The aim of a circular economy is to create a system in which waste and energy leakage is minimised and resource input is avoided by closing the material and energy loops. Despite the advantages of CE, the construction industry has not yet made a significant step towards
the CE. The theory of Reverse Logistics (RL) could be the enabler of circular economy in the construction industry. RL in the construction sector is defined as the management of collecting, sorting, processing and reusing construction waste. In the field of RL, quantitative models have proven to be a successful tool to combine environmental goals with financial constraints. However, such models are missing in the field of construction industry. In this context, this research proposed a general applicable RL-model that supports decision-makers in implementing circular principles in the return flow of their assets while minimising the costs.
Literature review has been conducted to obtain a theoretical framework for the model design. The first part of the literature study has provided a framework to prioritise different waste management strategies based on their level of circularity. The second part of the literature study has been conducted to get an insight in the characteristics of the reverse logistics in the infrastructure and how the principles of circular economy can be included in the RL-process.
The most suitable modelling approach for the proposed problem has been found to be linear programming.
The proposed RL-model has been designed as a transhipment model and is based on mixed integer linear programming (MILP). The proposed model design simulates the reverse flow of one asset moving from a deconstruction project, through the processing facilities to the final redistribution. The proposed model has been complemented by a guideline that supports the application of the model for specific cases.
To test the applicability of the model and the proposed guideline, the model has been applied on two different types of assets in the infrastructure: concrete and street lights.
The model for both cases have been run for multiple scenarios, based on the developments in the industry. The results of the model provides two types of information. Firstly, it provides a trade-off between the level of circularity and the costs. Secondly, it gives the corresponding network-design for the different outcomes. It was found that technical innovations in combination with efficient transportation will help to create return flow in the infrastructure, according to the principles of circular economy, which is financially feasible.
Overall the model has been proven to be general applicable and it supports decision-makers in making decisions about the reverse flow. The outcome gives information about the financial impact on implementing circular principles. The corresponding RL-network provides an insight in which aspects in the RL-process influences the outcome.