The largest waste types in construction projects are surplus rock, stone fractions and other construction- and demolition waste, with a large potential for reuse and recycling. In order to fulfill national and international goals of 70 % material recovery from construction and demolition projects, it is necessary to facilitate adequate management of these waste flows.
Collaboration
On the other hand, there is an increased demand and scarcity of construction materials. Recycling and reuse of construction and demolition waste are of both environmental and economic importance, as it can reduce landfill, transportation and resource extraction. The Norwegian municipality of Bærum wants to facilitate the optimal use of such masses through the collaborative project Bærum Ressursbank. Eirik Halvorsen wrote his master thesis to evaluate the potential benefits.
The aim of Eirik’s thesis is to provide decision support for the planning of recycling and handling of surplus material from construction and demolition projects. The hypothesis is that better planning of mass transportation and recycling collaboratively across projects will facilitate increased reuse of waste materials and reduced transportation needs, resulting in both economic and environmental benefits.
Modelling
This is done by analyzing the distribution network of construction masses and which processing machines that are needed at different recycling facilities. The problem is solved by the means of a deterministic Mixed Integer Linear Programming (MILP) optimization model that combine a supply chain network problem formulation with a formulation of transportation backhauling (in this thesis denoted roundtrip). The model considers both environmental (CO2 emissions) and economic criteria, from the perspectives of individual projects and the overall system/society. Using this model, different scenarios are analyzed based on a real-life case in the municipality of Bærum in Norway.
The research provides a model that can be used as a decision support tool for both government agencies and commercial participants in the construction and demolition sector when planning transportation and logistics around construction wastes. The research shows that if trade and transportation of masses are planned cooperatively across projects is beneficial for recycled and reused construction waste.
Less cost and emissions
The analysis shows that emissions and costs can be reduced at least 20 % and 34 %, respectively, compared to individually optimizing each respective project. However, the results indicate that not all environmental impacts are reflected by only considering CO2 emissions. Benefits for local inhabitants surpass the reductions in carbon emissions, as a transportation collaboration could reduce empty truck kilometers by as much as 55%.
The model proposed in Eirik’s master thesis is ready to be implemented in real-world applications. Several industry participants have already shown interest in the model with positive feedbacks. By increasing the quality of input data, even more, the produced results become increasingly accurate and can be used as decision support for governmental agencies, project owners, entrepreneurs and other parties in the construction and demolition sector.
Source: NTNU Open