Making progress with sustainable materials
Circular working often feels like pioneering. Contracts do not always provide the flexibility to encourage this. Richard Pool, advisor for spatial planning and sustainability at Rijkswaterstaat Noord-Nederland, shares promising initiatives.
‘Opportunities for circular working are best explored early,’ he says, emphasizing the importance of matching supply with demand.
Exploring bank structures
According to Pool, many discussions about circularity converge in the Main Waterway Lemmer-Delfzijl program. This 118 km waterway is being upgraded to Class Va, including the replacement of 8 bridges. ‘It’s an extensive project where you can really make strides using sustainable materials,’ he explains.
During the project, old sheet piles will be removed. Pool adds, ‘From a sustainability perspective, I suggested during the exploratory phase that the bank structures be constructed with sustainable materials. The project team is also investigating how the removed sheet piles can be reused in smaller waterways or other applications.’
Sheet piles or riprap
A life cycle cost analysis was conducted for the sheet piles to reduce the environmental impact of the waterway works. ‘An engineering firm analyzed all possible bank structures, including plastic, concrete, steel, and wood,’ explains Pool. The analysis concluded that European hardwood sheet piles are the most sustainable choice below the waterline.
However, they are not suitable for structures above the waterline. Riprap banks also performed well, with CO₂ emissions 30 - 40% lower than steel and costs about 50% less. A drawback of riprap is its larger spatial footprint compared to sheet piles.
The entire lifecycle of riprap, including quarrying in Scandinavia, was examined. ‘Based on these studies, we recommended riprap banks in our sustainability vision,’ Pool summarizes. The project team’s commitment to sustainability made this choice feasible. ‘That enthusiasm is essential for applying reusable materials in practice.’
Making sustainability stand out in procurement
Pool highlights a challenge in standard procurement systems: materials released from projects automatically belong to the contractor. ‘It’s economically advantageous to reuse these materials locally, but this depends on the contractor’s network or efforts to find a new purpose for them. Unfortunately, this cannot be mandated in procurement,’ he explains.
Regional sludge becomes grasscrete
Transport is an unavoidable factor in circular materials, as emissions from transport can offset their environmental benefits. ‘That’s why circular materials from the local region are preferred. However, it’s challenging to capitalize on the advantages of regional products within procurement policies,’ Pool notes.
‘Under European procurement rules, you can’t specifically request regional circular products.’ For example, he investigated whether the roadside along the N33 could be reinforced with grasscrete blocks made from pressed sludge from the Ems Dollard. ‘This would create a win-win situation by applying a specific circular product from the area.’
Developing circularity
Pool identifies regional storage locations for reusable materials as an important development. ‘Think of storing sheet piles, bridge sections, portals, and guardrails for highways to avoid unnecessary long-distance transport of materials.’
Collaborating with other government bodies in shared material banks could also offer opportunities for Rijkswaterstaat. He predicts that standardizing dimensions for components like beams and movable bridge parts will increase reuse possibilities.
‘Standardized sizes make materials easier to repurpose for other projects,’ he explains. Making materials easier to locate is also crucial. ‘In circular working, everything revolves around connecting supply and demand,’ Pool concludes.