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Synthetic turf systems – current developments
By Bjørn Aas, Senior Engineer, Department of Civil and Environmental Engineering Faculty of Engineering, Norwegian University of Science and Technology
Over the last 30 years, synthetic turf systems have become a reference solution for ball sports globally. “Less or no impact on climate”, “More durable than natural systems” are statements used to promote the systems. In Europe, more than 20 000 pitches are now in operation, and we are about to face the long-term impact of the development. There is an elderly-wave of turf systems growing behind us, and with a lifetime of 10 years or so, the renovation market is supposed to grow substantially, provided available funding. Along the way, the environmental impact has become visible, with growing piles of disposed turf systems, heavy metal pollution, and microplastic contamination of soil below the turf - and in the ambience of the fields. The future may belong to systems based on reduced number and quantities of synthetic products, recycled materials used in turf, shock pads and infills. Longer lifetime and reduced maintenance costs are mandatory to achieve an economically sustainable sport.
In the mid 90-ties, rubber infills based on old vehicle tyres were introduced as “performance infills”. By increasing the length of the fibre, this infill could more or less replace the underlying shock-pad. As this infill is a waste product, prices were – and still are – low, allowing to reduce the overall cost of a turf system. The increasing number of synthetic turf fields in the subsequent 15 years made the environmental impact of this infill visible. Not only as a substantial growth in waste volumes by renovation of fields, but also pollution by heavy metals and microplastic to an extent beyond guidelines and regulations from other sectors like agriculture and construction industry.
In Norway, the market for new synthetic turf fields boomed in 2005-2010, and 4-5 years ago, the renovation market started to grow accordingly. As in many other countries, reports were stating that this product may cause environmental concerns. Heavy metal seepage from SBR rubber granulate is well known, and the rubber particles brought away by users, wind, rain or maintenance equipment caused both the chemical and microplastic pollution to grow.
As a call from three Norwegian regions (Viken, Trøndelag, Vestland), the project KG2021- a project on future synthetic turf fields, was launched in 2019. With additional funding from the Ministry of Culture (the Lottery Fund) and Norwegian FA, the project’s objective is to identify and test turf systems without synthetic infills. The project is managed by SIAT - Centre for Sports Facilities and Technology at the Norwegian University of Science and Technology, Trondheim.
During the project, six pilot fields are constructed in cooperation with sports clubs and municipalities. The pilot fields are constructed by three different suppliers of synthetic turf, and comprise of prefabricated as well as e-layer shock-pads, a variety of fibre products, organic infills or non-infill systems. The scope of the project is to develop systems with the following properties:
- less content of synthetic materials in the system
- no heavy metals in any product included
- substantial part of system from recycled materials
- improved quality of turf, longer lifetime
- reduced lifetime cost of system
All test fields are designed for low level senior, children and youth user groups. The performance reference is Nordic Norm, equal to the EN15330 which is the European norm for synthetic turf for sports areas. Knowing that less than 2% of football players in Norway are on top national level, and less than 10% of the fields are used for top football, the project is aiming to identity the future systems for all the other fields and users. The project is organized in three work packages: Sport, System and Environment.
During the project period, some interesting findings are worth mentioning. In recent years, the infill has been highlighted as the problem, and maybe also the most important product in a system. There is a substantial development in the market in the direction of infill based on organic materials, systems using only sand as infill, or complete non-infill turf.
From KG2021, it seems clear that understanding of the whole turf system, including shock-pad, backing, fibre and infill, needs to be addressed more. Properties of the shock-pad combined with length of fibres are not fully understood with respect to user experience, maintenance and durability over the lifespan of the system. Each of the pilot fields, and additionally two reference fields with rubber infill, are tested annually by an accredited lab. Experience from pilot fields so far indicates that the users prefer a thicker shock-pad, which allows for reduced length of yarn and equal reduction in infills.
With respect to the system, two findings may be highlighted: The quality of the yarn with respect to climate impact (UV, air, temperature) and maintenance. The loss of fibres from the turf due to low quality materials may be substantial. Finetuning maintenance equipment to turf systems is less understood by owners as well as suppliers. This is of major importance during winter operations. It is also interesting to observe that during the project period, the first systems made using recycled products from old fields are introduced. This includes shock-pad as well as turf and sand. A variety of organic infills are introduced, and one interesting finding is the reduced quantities required, compared with systems with synthetic infills. While rubber infills normally are applied in the range of 7-15 kg/m2, organic infills like olive pits and cork/coconut mixtures may be used in lower quantities, typically in the range of 1-5 kg/m2.
The market for infills may be described by three categories: Polymer-based, organic, and non-infill as a new option. The recent introduction of mixed products such as polymer-coated sand, SBR + hemp and SBR + cork may be an attempt to reduce the quantity of polymer in the infill. The backside is that these mixtures are applied in large quantities, and there are question marks on the end-use. Recycling has so far not been addressed as an option for any of them.
An analysis of tenders in the Norwegian market the recent two years have led to an LCC-model for turf systems. The analysis includes investment, maintenance including refill and finally disposal. The preliminary result of the analysis indicates that systems with infills containing microplastic represents higher total cost of ownership than systems with pure organic infills or non-infill systems.
As the project KG2021 moves on, several knowledge gaps are identified. FIFA’s recently launched project on development of new test equipment and methods is welcomed. The present test reports (Nordic Norm) from the pilot fields do not allow for clear conclusions with respect to which system are working best for the different user groups. Equipment for maintenance must be developed further and more fit to the different turf systems. Fibre quality must be addressed with respect to climate impact. Test methods for wearability must be developed in order to simulate a required lifetime of at least 15 years. The ECHA agency is working on restrictions for the use of microplastic and infills in synthetic turf are among the products discussed. Construction of fences and walls around a field will only solve a fraction of the problem, as heavy metals and microplastic pollution of soil and waterways are not taken care of. Substitution, i.e., replacing the infills containing microplastic with organic infills, may be the only solution.
The most important challenge is to create a value chain for removal, processing and material recycling of old turf systems. At present, this value chain is fragmented and capacity in the different parts is limited. In Norway, an Innovation Contract is out for inquiry these days, and the objective is to support development of this value chain. Reduce waste quantities, facilitate material reuse and reduce lifetime costs are some of the pieces in the puzzle to reach a sustainable future for synthetic turf systems on the sports fields as well as the playgrounds.