A route to Net Zero in the Construction Supply Chain: The Circular Economy
Part 2
What if we could apply the principles of circular economy to the construction sector?
The circular economy is a model of production and consumption, which involves sharing, leasing, reusing, repairing, refurbishing and recycling existing materials and products as long as possible. In this way, the life cycle of products is extended.
In practice, it implies reducing waste to a minimum. When a product reaches the end of its life, its materials are kept within the economy wherever possible. These can be productively used again and again, thereby creating further value.
Material Passports aim at giving an identity to buildings’ materials.
The method of building removal determines whether a building becomes waste or provides building materials for reuse. Traditional demolition methods can produce a lot of waste by destroying the component parts. Deconstruction — careful and selective dismantling and separation for reuse and recycling — reduces the volume of waste disposed to landfill and cleanfill and allows the removal of components in a form that can easily be reused. Most buildings that have reached the end of their desired life or are undergoing renovations have materials and systems that still have some useful life.
The concept of a “material passport” was developed by Thomas Rau, a Dutch architect who has been working on the development of a public database of existing building materials and their potential for reuse. A material passport is a digital record of the specific characteristics and value of each material in a building project, thus allowing the recovery, recycling and reuse of the different parts. In simple terms, the idea is that in order to recycle a product, we first need to know what that product is. However, once materials are used to construct a building, they lose their unique identity. Therefore, the passport of each material of a building aims to restore its identity so that it can be treated as a commodity in the future.
Material passports are one of the key enablers of efficiency and resiliency in the built environment, turning buildings into material banks and facilitating circular business models. One purported method is improving life cycle analysis by incorporating, amongst other things, technical data sheets, materials safety data sheets, environmental product declarations and bill of materials information. Ideally, material passports would be used from the design of buildings through their construction to demolition and recycling.
The passports need to be dynamic in a distributed cyber-physical-social environment.
Data needs to be updated and linked together by actors with differing technical capabilities over long periods of time.
Concular is creating material passports for the construction industry. Concular has automated the process of creating Material Passports for new buildings. Contractors can upload a BIM model and it will be automatically translated into material passports. As of today, the process for existing buildings is semi-automated. Contractors can assess the outside and inside of a building with Concular’s software on a phone or tablet. After selecting a category, contractors can annotate materials or products with all the necessary information, across more than 200 categories. Concretely, a project developer reaches out to Concular and accepts an offer from them. Either a third-party or Concular will go to the building and will digitize the materials in it using Concular’s software. If a demolition is planned, the project developer can tell what in the software and the materials will be marked as being in sale. On the other side, project developers and architecture offices upload their demand on Concular (e.g. uploading a BIM model or material demand list). The materials will be automatically matched with a buyer. The project developer of the building to-be demolished gets a list of materials that will be selectively deconstructed.
Automation of material identification in un-digitized built environments is a key challenge.
For existing buildings, the methods used to generate passports for each material are still rather manual. Most of the time, experts have to physically go to the buildings, take a picture of the materials, and for each of them, select the right category and fill in the information. What technologies can help automatise this process?
Laser Scanning is the controlled deflection of laser beams, visible or invisible. Laser scanning is used in construction to produce 3D object scanning. Within the field of 3D object scanning, laser scanning (also known as lidar) combines controlled steering of laser beams with a laser rangefinder. By taking a distance measurement at every direction the scanner rapidly captures the surface shape of objects, buildings and landscapes. Construction of a full 3D model involves combining multiple surface models obtained from different viewing angles. Small objects can be placed on a revolving pedestal, in a technique akin to photogrammetry. 3D object scanning allows enhancing the design process, speeds up and reduces data collection errors, saves time and money, and thus makes it an attractive alternative to traditional data collection techniques.
- Pros: Accurate dimension measurement.
- Cons: Lack of completeness mainly due to two factors: occlusions and the temporal gap between two laser scans.
Imagery: Images captured by RGB-D cameras, DSLR cameras, and smartphones are also used for supporting deconstruction documentation.
- Pros: Perfect completeness thanks to the possibility of gathering images continuously. Here, we can imagine a camera that is continuously filming the building while being constructed or deconstructed.
- Cons: Lack of accuracy in dimension measurement.
Zephyr 3D is the photogrammetry software solution by 3Dflow. It uses photogrammetry to create 3D models out of 2D photos. 3DF Zephyr works with a high definition camera (which could be a smartphone camera) to capture photos of an object. The photogrammetry software then stitches the photos together to create a 3D mesh or model.
The reverse logistics case of circular construction: how and where can pre-used materials be bought and exchanged?
In a perfect world, when a deconstruction or a renovation happens, non-reusable materials are being recycled, but what happens to reusable materials? Two options:
Remanufacturing is a manufacturing process that involves dismantling a product, restoring and replacing components, and testing the individual parts and the whole product to its original design specifications. The performance after remanufacture is expected to be at least the same as the original performance specification (‘like new’) or better, and the remanufactured product generally comes with a warranty. Concretely, the product is sent back to the original manufacturer who then refurbishes it and sells it as pre-owned to another customer.
Renting or buying on pre-owned construction materials marketplaces: Second-hand marketplaces are places where people can meet to buy, sell, or trade essentially anything secondary: products that have been pre-used, pre-owned, or remanufactured, or materials that are left-overs or by-products of a production. There are several different marketplace types that participate to the circularity of construction supply chain:
- Rental marketplaces for construction equipment: Renting construction equipment is a way of maximizing asset utilisation on site, while reducing environmental impact as it takes place in a sharing model. Yardkink is one of them: a platform where site managers can easily rent construction materials, from asset heavy items such as concrete crushers, to asset light items such as drills.
- Pre-owned marketplaces for construction equipment.
- Marketplaces of pre-used and refurbished materials: to date in Europe, the most mature marketplace of pre-used construction materials is Restado, the largest platform to buy and sell second-hand construction material. It has several thousand construction materials coming from overproduction, leftovers or demolitions.
Key Takeaways
- The construction sector is the largest waste generator, accounting for 35.9% of the waste generated by the EU in 2018.
- A few different construction processes produce waste as a byproduct: Materials Budgeting and Procurement, Building Processes, and Demolition.
- To address this massive problem, new technologies and companies are emerging and receiving increasing investment from venture capitalists.
- Sustainable building materials and processes are being developed.
- Designs are being rethought, and I think the future of construction will be modular.
- Circular methodologies are being implemented to turn old buildings into material banks — think material passports and building twinning.
- Marketplaces are arising to provide the basis for this new economy.
