Microplastic fromcast rubber granulate andgranulate-free artificial grass surfaces

• This assignment, commissioned by the Swedish Environmental Protection Agency, focused on expanding knowledge about the dispersion of microplastics from cast rubber and granulate-free artificial grass surfaces by supplementing previous studies with new measurements and calculations. The goal was to improve estimates of how much these sources contribute to microplastics nationally and to identify strategies to better prevent leakage into the environment.To our knowledge, this is the first time this method has been used. The method allowed us to quantify the leakage of microplastics from cast rubber surfaces and granulate-free artificial grass surfaces in wash water from cleaning machines specifically adapted for these types of surface. By analysing a well-mixed subset of wash water and using information on the size of cleaned surface areas, the leakage of microplastics from these materials per unit area was determined to be 0.4–20 g/m2per year for granulate-free artificial grass and 0.6–48 g/m2 per year for rubber surfaces. The variation between different surfaces is, however, very high and the uncertainty in both measurements and analysis is high. This is a level of dispersion on par with a road surface with an annual mean daily traffic of 5,500–13,000 vehicles, which is estimated to be 56 g microplastic/m2. Some artificial grass surfaces release their artificial grass much more easily than others (about 50 times easier). This is why standardised methods for identifying high-emission artificial grass surfaces should be developed. Well-designed and well-maintained granulate-free artificial grass surfaces are likely to meet the EU’s proposed threshold limit for dispersion of microplastics at 7 g/m2 per year.Based on municipal surveys, supplier data and GIS analyses, Sweden’s total area of cast rubber surface is estimated to be 1,200,000 m2 in 2020, of which approx. 550,000 m2 is on playgrounds and approx. 650,000 m2 is on sports pitches. Previous studies looked at Sweden’s total area of granulate-free artificial grass in 15 cities, which this project estimates, based on population, to total about 447,000 m2.Based on the estimated rubber area on playgrounds and sports pitches combined with the measured microplastic emissions per year and square metre, total emissions from Sweden’s rubber surfaces are estimated to be about 16 tonnes/year. The equivalent estimate for artificial grass surfaces without granulates is about 2 tonnes/year. These are thus considerably smaller sources of emissions than such sources as road traffic (8,190 tonnes/year) and artificial grass with infill (676 tonnes/year), and in line with estimated microplastic emissions from fishing nets and other fishing implements (4–46 tonnes/year). The relatively low values are attributable to the total area of these surfaces being significantly smaller compared with the total area of roads in Sweden. Measures to reduce microplastic emissions from car traffic can thus reduce Swedish microplastic emissions more than measures for rubber surfaces. However, the latter measures are also important because they are relatively easy and cost-efficient to implement.The project developed technical specifications to limit the leakage of microplastics from surfaces with cast rubber granules. These include making good material choices, such as recycled SBR (styrene-butadiene rubber), choosing European tyres newer than 2010 which do not contain hazardous HA oils, and using 10–20 % PUR binder if casting occurs outdoors. Always consider the use of natural materials, which do not generate microplastics, such as grass, wood chips or sand. Available cork products on the market have the same function and appearance as rubber materials. Though these still contain PUR binders, they are considered a more environmental-friendly alternative from a microplastic perspective and probably from a climate perspective as well.Construction (environment, substrate and design) is another important aspect for reducing the leakage of microplastics from rubber surfaces and artificial grass surfaces. Open street drains near these surfaces should be avoided, and in exposed places these should be fitted with filters. Good drainage should be ensured by using stable draining substrate, such as crushed stones and stone dust. Sand on granular surfaces increases wear and should be avoided by separating with edges and spacing. Trees, particularly fruit trees, and berry bushes should be avoided next to rubber surfaces due to bird droppings and troublesome soiling that can require expensive maintenance.Maintenance is crucial for long lifespan and reduced leakage of microplastics from rubber materials. Prepare a maintenance plan together with the supplier and the maintenance contractor. Check the surfaces regularly (approx. 3–10 times/season) and repair damage as soon as possible so that it does not worsen. Pick, vacuum, brush and/or blow off debris and leaves from the surfaces regularly (3–10 times/season). Do not plough and clear snow on granulate surfaces and avoid using the surfaces for dumping snow. Empty any microplastic filters regularly, at least once a season and more often as needed. Do a deep clean with a cleaning machine if necessary, about once per every 1–4 years, depending on how dirty the surface becomes. It is important that the wash water be treated properly, so that it does not contribute to emissions of microplastics. Standardised methods for identifying and addressing high-emission artificial grass pitches and rubber surfaces should be developed to cost-effectively reduce the dispersion of microplastics from these surfaces.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

Publikations- och innehållstyp

vet (ämneskategori)

rap (ämneskategori)