Contrary to popular belief, organic infill can be used for third-generation synthetic turf in Scandinavian countries. Scientists of the Centre for Sports Facilities and Technology (SIAT) and the University of Science and Technology in Norway have come to this conclusion after studying several synthetic turf systems with organic infill over a five-year period.

The investigators studied six full-size synthetic turf football fields in central and southern Norway. In addition to facilitating football, all fields were also used by nearby communities for leisure activities.

The main objectives of the pilot fields were to:

• Reduce the spread of microplastics from artificial grass pitches by >80%
• Reduce the amount of synthetic materials by >85%
• Reduce pollution from heavy metals by >90%
• Achieve a recovery rate of >60%
• Improve the lifespan of synthetic turf pitches

Three systems studied

The investigators studied three different synthetic turf systems. One used a fibre structure with a combination of a straight fibre and a curled, underlying fibre with a density of 2,500g/m2. This particular system used 1-2kg/m2 olive peat as infill. The second system had a more dense fibre structure of around 2500 – 3000g/m2. The pile height was around 34mm and the carpet didn’t have any infill. Instead, it was clamped around the field as it was installed on a 6mm shockpad. The third system used solely 45mm monofilament yarns on a 10mm shockpad. A mixture of cork particles with coconut fibres was used as infill.

The study also showed that the usage of fields like these is more complex than expected, and around 50% of the users are using non-football shoes, i.e., flat soles. This is typically when the field is located close to schools where the field is both a playground in spare time and used for physical education.

E-layer over shockpad

A key takeaway from the study is that the focus should be on the entire system, instead of just one or two components, to achieve the abovementioned objectives. A good example is the advice to invest in third-generation synthetic turf surfaces that require a shock absorbing layer.

Historically, Scandinavian FAs and suppliers have promoted systems with no shockpad, or maybe 10-12mm pads, while the performance properties were achieved by the rubber infill layer in a 50-60mm high monofilament structure.

The researchers now go as far as advising a 22-35mm e-layer over a prefabricated shockpad. They justify this preference because, in their view, the hydrophobic structure of the e-layer prevents it from freezing up, while this is still possible for a prefabricated shockpad.

Further, when removing the performance properties of the synthetic infills and introducing organic infills with reduced weight and volume, the performance properties of the system will be transformed to the carpet and the shockpad. In order to reach the expected properties, an e-layer of 25-30mm is recommended.

Different maintenance approach

The researchers point out that synthetic turf systems like the three tested are less demanding in terms of maintenance frequency but do require more intense activity to keep the infill loose. This applies to both summer and winter operations. Since the system does not contain environmentally harmful materials, the owner’s responsibility for environmental monitoring is much simpler to manage. The reason for the reduced maintenance demand is explained by the use of the e-layer, the dense fibre structure and the limited content of the infill.

Financial implications

In terms of financial viability, they conclude the following:

• It is expensive to own a synthetic turf system with synthetic infill
• The new hybrid infills (a mixture of polymeric and organic infill) increase the costs to an even higher level
• Systems with sand or sand/organic fillings are the most economical solutions
• Systems without infill are in the upper tier in terms of cost, but prices are expected to fall

when production volumes increase.