A contract-specific environmental plan is a significant way to promote climate sustainability in paving works

News 2023-09-01 at 17:00

City of Helsinki news 24 January 2023 

Emission-intensive asphalt used for paving is the most common material in cities for the surface layer of roads, bicycle lanes and pavements, and due to wear and tear, the paving must sometimes be replaced. In Helsinki, 70,000–80,000 tonnes of asphalt are installed every year. In order to reduce significant climate and environmental impacts in Helsinki, the paving works annually tendered by Helsinki City Construction Service (Stara) were reviewed. The development work strived to account for the life cycle, circular economy and climate perspective better than before by making use of procurement criteria. 

Cost benefits through resource-smart material usage and decreasing fuel consumption are being sought in asphalt work. Trials have also been actively carried out in terms of material production and emissions from transport and installation equipment in order to map out the opportunities of low-temperature asphalt. Key emission reductions in asphalt works are achieved through recycling asphalt as the raw material of new asphalt, producing asphalt at a lower temperature and using biofuels at the asphalt plant and in the installation equipment, among others. 

In addition to taking these into account, the City’s paving works’ development looked into the opportunities for carbon footprint calculations and tools for tendering paving contracts, as well as hearing the market’s views on emissions calculations. The aim was to increase skills and gain data on how much emissions result from the paving sector during the life cycle’s different stages. The aim was also to increase the sector’s operators’ awareness of environmental criteria and reporting. 

Recycling and low-temperature asphalt is the way of the future 

When preparing for procurement, operators’ readiness to implement contracts with low-temperature asphalt was mapped out. Contractors wish for large sites for this; adjusting the plant’s temperature is not simple, making it difficult to produce small quantities of asphalt. As production develops, the City of Helsinki will also utilise more low-temperature asphalt, provided that the quality is found to be sufficient. More trials are needed, and the opportunity to order separate low-temperature asphalt test sites on low-traffic roads was added to the contract period. 

Stara has monitored the utilisation rate of recycled asphalt for three years, and rate in Helsinki is about 50–57%. Clarifications were made to the procurement so that, going forward, the maximum share of recycled asphalt in accordance with norms can be used, and test sites using more than the asphalt norm can be implemented as a separate order. Currently, the asphalt norm is 70% in load-bearing asphalt layers and 50% in surface layers, but as the norms are updated, the maximum permitted amount of recycled asphalt will be 60% for both. However, the total amount of recycled asphalt will increase, as surface layer asphalt is installed in significantly greater amounts than load-bearing asphalt. In 2023, however, the municipalities in the Helsinki metropolitan area still retain the percentages according to the old norms, as the first requests for tenders were published while the approval process for the norms was still ongoing. 

During the tendering process, we learned that the transport of materials for paving contracts is not significant in terms of emissions, but rather, the largest emission reductions can be achieved in the production of material and in the selection of raw materials. Low-temperature and recycled asphalt are seen as having potential in the promotion of environmental sustainability. However, more detailed product-specific data about the materials as well as cost impacts is needed for making climate-sustainable decisions. In this round of tendering, the use of recycled asphalt did not impact the contracts’ costs. It is, however, advisable to evaluate the amount of low-temperature asphalt in the future in order for it to be a part of the tendered prices. 

Carbon footprint criteria for sustainable procurement in Canemure 

Environmentally responsible procurement criteria can be used to guide the selection of products and services offered by the markets. As a significant procurer, the City of Helsinki wishes to promote this and to develop currently existing procurement criteria and start using new ones which better take into account the perspectives of life cycle impacts, circular economy and the climate. 

Helsinki is tackling the promotion of low-carbon procurements through various development projects. One of these is the Towards Carbon Neutral Municipalities and Regions (Canemure) project, in which Helsinki’s aim is to develop low-carbon procurements and research the usability of carbon footprint as a factor guiding procurement. The project, which implements practical measures to mitigate climate change, is coordinated by the Finnish Environment Institute. 

In addition to paving contracts, the Helsinki subproject has piloted eight other low-carbon procurements, from construction to food and work clothing procurements, among others. A case description summarising the procurement’s preparations and the lessons learned has been created for each procurement. The results obtained from the Canemure project and the development work support the City’s carbon neutrality actions. 

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