It is forecast that 800 million tonnes of excavated material will be generated from tunnelling projects currently planned in the EU. Although a small amount of this material may be used within the jobsite (e.g. to make concrete) the vast majority will end up in landfill. This is tremendously wasteful as much of this material could potentially be used by other industries (e.g. for concrete, aggregates, brickmaking, or for producing glass or steel, depending upon the rock type).
The goal of DRAGON is to develop technologies that can be installed directly on tunnel boring machines (TBMs) to analyse and characterise excavated material as it is generated within the tunnel. This equipment will assess various physical and chemical parameters including elemental composition, moisture content, mica content and rock strength. This information can be used to determine whether the excavated material meets the specifications from local industry near the jobsite. Suitable material can then be stored and processed separately before being sold to these industries, thus diverting material from landfill. Herrenknecht, the global leader in TBM manufacture, is a project partner and developed a working prototype to demonstrate the technology.
The use of this excavated material by other industries will have a number of environmental and social benefits
- Divert material from landfill, which, as well as being unsightly and aesthetically undesirable, may also have negative environmental impacts on local ecosystems
- Reduce costs associated with the disposal of the excavated material; these can be significant and entail additional expense for the project owner.
- Improve resource efficiency and support the circular economy. Material excavated from tunnelling projects is often suitable for use by other industries. Depositing this material on land represents a huge missed opportunity to use these resources more beneficially.
- Meeting demand for minerals from tunnel projects conserves other sources of these minerals and so can extend the life of quarries.
Role of thinkstep
thinkstep is the leader in the environmental assessment of DRAGON. This included three main tasks:
- Assessment of potential for diverting material from landfill: based on assessment of material supply and demand for 54 recent tunnel projects
- Development of LCA model for tunnelling projects
- Projection of future benefits: running the LCA model for all 54 studies assessed in task 1 and scaling up to 800 million tonnes to estimate overall expected impact.
The overall benefits from applying DRAGON technology to planned future European tunnelling projects are potentially very large, e.g. saving 5 million tonnes of CO2-equivalent (equivalent to the annual greenhouse gas emissions of more than 460,000 European citizens). Even larger improvements were seen for other impact categories.
Project website: www.dragonproject.eu