The path to infrastructure with a lower CO₂ footprint

In 2023, requirements were introduced in Denmark for LCA calculations on new construction and a maximum limit for CO₂ emissions from new buildings over 1,000 m². There are still no requirements for civil works, even though they represent a large item in the climate accounts.

It is no secret that the building area for many years have had a leading position compared to the civil works area when it comes to the use of LCA. InfraLCA, which is the name of the common tool in the civil works industry, was not launched until 2022 and is still under development.

But due to the climate challenges, it will only be a matter of time before we see sustainability requirements for infrastructure, which is something we are prepared for.

Integration with BIM
At Artelia, we work with InfraLCA, and we are therefore ready to help the infrastructure owners who want to focus on climate footprint.

Our dream is that BIM will eventually become a flexible and efficient supplier of data. For BIM to really gain ground within the civil works area, there is a need for a uniform classification of civil works parts and their features, says our experienced BIM expert, Gita Monshizadeh.

This means getting a clear data structure for how to describe the objects that represent the civil works parts in a digital model:

Cooperation across industries
Gita emphasises that not only 3D models are worth considering in this context :

Points, lines and surfaces are in principle also objects that information can be connected to. This has been done for a long time in GIS systems, and with the right structure, you can create a better link between BIM and GIS and ensure the right data for CO₂ analyses.

According to Gita, the development of standards is, to a large extent, conditional on much better cooperation across the industry.

This is why she participates in several professional forums such as FRI – Danish Association of Consulting Engineers’ digitisation task force, DiKon Civil Works and buildingSMART Denmark.

From layer to object structure
The joint effort may be valuable, as the use of objects with classified data has a much greater potential than the layer structure, which has otherwise been the dominant method in the civil works industry for a long time, says Gita :

The layer structure used in the civil works industry is an efficient way of structuring the geometry in civil works models. If you need to connect properties and make analyses on e.g. CO₂ savings, geometry is not enough. There is a need for an object-based classification system which can describe the objects with their associated properties, including their CO₂ impact.

Digital soil models
One of the things Gita notices specifically is the soil utilisation. Unspeakable amounts of soil are moved and disposed of in the civil works projects in Denmark, which is why she is pleased that our geotechnicians have dived into Leapfrog Geo and OpenGround, which are relatively new software in a Danish context.

By combining the two programmes, you can better automate the processing of geotechnical data and model soil conditions efficiently. This is an advantage especially on the long sections and large areas that characterise infrastructure projects.

Volume, surfaces and data on soil types are part of the information that can be extracted from the models and become particularly relevant for the work related to sustainability.

The value of reused soil
If you want to illustrate how big a role soil management actually plays, you can look at the positive effects that recycling of soil may have rather than sending it to landfill. We have two brilliant examples of just that.

With the district heating project in Ørslev for the utility company Vordingborg Forsyning, we gained our first experience. Instead of disposing of the soil that was excavated during the construction phase of new cable routes, it was lime stabilised and extra gravel was added, so that it could be used as fill with the right properties.

This resulted in a saving of approx. 2 billion kilometres driven in passenger cars, which corresponds to 49,906 trips around the world. The financial savings were DKK 4 million.

These figures are difficult to ignore, and our district heating engineer Morten Borris Jensen, who had a large role in the project, has made several external presentations about the experience.

Pilot project with great effect
We experienced the same good results when we used the experience on a pilot project related to separate sewerage in Strøby Egede. Oddly enough, it was exactly rainwater that caused problems during the installation of the new rainwater and wastewater pipes.

The summer of 2023 was one of the wettest ever, which is why extra soil had to be removed. The parties therefore took on the task of recycling by establishing a local site for processing the soil using the same method as in Ørslev.

The pilot project ran for just under a month, and during that period, the team avoided disposing of 2,600 tons of soil and purchasing approx. 2,400 tons of new gravel and stone materials.

Even with the costs of soil processing, it resulted in financial savings of DKK 116,000 together with another gain for society, says Nick Rønnow Hoffmann, who took part in the process :

An extremely scarce resource
As pointed out by both Gita and Nick, it is significantly easier to get permission to recycle materials in civil works projects than in building project.

In addition to CO₂ and price, there is a third important factor that strongly suggests that soil should be recycled to the greatest extent possible:

In a few years, we will have no more gravel and stone materials in all of Zealand. We will then have to ship it from Jutland or abroad, which will be expensive both in price and CO₂ emission.

Far greater recycling of soil is therefore not only a gain. It is a necessity, says Nick and is supported by sustainability specialist Kristian Kromann: