Broader environmental considerations

Chapter 7 of the Natural Grass vs Synthetic Turf Surfaces Study Final Report.

There are many environmental issues that need to be considered when making a decision on a preferred surface. Many factors come into consideration and rather providing advice on which is the more environmentally sustainable choice the information below, is provided as a initial starting point and to help initiate thinking and discussion.

If it is an area that is important in the decision making process then it is advisable to conduct and seek further research and information in this area, as there are many helpful resources available. These are referenced but not fully expanded on within this report.

Synthetic turf is often promoted as being a ‘green’ alternative to natural grass. The main ecological benefits of synthetic turf that are promoted are:

  • Conserves water (research in the US has shown that each full-sized rectangular field saves between 1.8 million to 3.7 million litres of water each year);
  • No mowing (mowing, especially large areas of natural grass, use fossil fuels and contribute carbon dioxide into the atmosphere);
  • No pesticides or herbicides for pest and disease management are required (reducing harmful chemical inputs)
  • Recycled materials are often used (rubber granules are often used in the base of synthetic turf as infill, these rubber granules are usually made from recycled tyres, keeping them out of landfill and reused sandshoe cushioning can be used for the shock pad).[1]

There are other environmental considerations such as water issues, carbon emissions, materials manufacture, maintenance and disposal and the impact on local environments. These need to be taken into account when considering the full environmental impact of each surface. They are elaborated on in the following.  

Water issues

Water usage

With many states of Australia experiencing extreme drought and water shortages over the past decade, the heavy irrigation needs of maintaining natural grass sports grounds has been questioned and alternatives have been sought.  These include better management and use of water by harvesting rainwater for re-use, or using recycled waste water for irrigation. Another alternative is to install a synthetic turf surface, which, from a water perspective has a major advantage over natural grass for most sports. Irrigation is a key component in maintaining good quality natural grass, whereas, synthetic turf does not require irrigation in most situations.  There are some types of synthetic turf that do perform better when watered, as it helps to decrease static cling, helps to wash away bacteria and fluids on fields, improves playability in some sports, such as hockey and helps to cool (at least temporarily) the often high temperatures of synthetic turf.  This water usage is generally significantly less than that needed to irrigate and maintain natural grass.[2]

Table 1: Typical grass water use per year

Sport

Area (ha)

Water Use ML/yr

AFL

1.60

9.6

Soccer

0.80

4.8

Rugby

1.00

6.0

Hockey

0.70

4.2

Bowls

0.16

1.0

Tennis

0.06

0.4

Athletics

0.70

4.2

For example, elite level hockey pitches are water based synthetic turf and require large amounts of water, this is something that the sport is conducting further research on and alternatives are currently being developed, which reduce the level of water required to ‘wet down’ a pitch.  Estimates are that a single hockey pitch requires 12,000 to 18,000 litres to take the pitch from a dry condition to a playable condition.

Irrigation not only requires the resource of water, but also needs energy to deliver it to the end user.

Stormwater and runoff

In addition to irrigation demands for water, a field’s ability to take in storm water is another environmental consideration. There are several environmental problems associated with storm water runoff. In general, natural habitats absorb storm water better than impermeable surfaces.

There is little groundwater retention when the soil surface is bare or when there are impervious surfaces such as streets, driveways, parking lots, rooves and synthetic turf. However, synthetic turfs can include drainage systems that compensate for their inability to take in water. A thick, healthy area of natural grass reduces rainwater runoff to practically nothing. The natural grass areas and the soil beneath create a good quality medium to purify water as it leaches through the root zone and the soil into underground aquifers.[3]

Studies in relation to the water quality of the runoff from synthetic turf compared to natural grass are conflicting and depend on the type of synthetic turf used. There are reports available that show the run-off into waterways from natural grass (that contain pesticides and fertilisers) compares poorly with the quality of runoff from synthetic turf.[4]  However, other studies show that leaching of zinc and other metals from rubber infill can be found in runoff from synthetic turf which may affect water quality and aquatic organisms.[5] The lack of consistency in the reported literature makes it difficult to draw conclusions, but it seems that the synthetic turf manufacturers are addressing the issues of contamination as the need for water harvesting becomes more important.

Capturing rainwater

Unlike natural grass, synthetic turf does not absorb rainwater—it simply drains through the surface or along the ground into storm sewers.  The harvesting of this water runoff, for re-use on site or locally, is an area that has been investigated and there are several reports available on this topic.  The general consensus is that whilst the idea has merit and can been seen as being environmentally responsible the practicalities of setting up the infrastructure and ongoing management require significant capital investment, often making it economically unviable.[6] However, this has been achieved and there are a number of cases in Australia where hockey fields have been designed to incorporate stormwater runoff and reuse technology, in which much of the water is recycled and re-used for watering the field.

Case study - State Netball Hockey Centre, Victoria

Victoria's State Netball Hockey Centre in Parkville is a world-class sporting venue catering to a variety of sports at a local, state and international level.  Maintaining the centre's two synthetic wet hockey pitches to international standards required around 24 megalitres of drinking quality water every year.  This significant use of water resources was a concern shared by the players, the wider community and the Centre's management. In response, the State Netball Hockey Centre took up the challenge to find an alternative source of water.

Victorian State Netball Hockey CentreThe Centre was awarded a government grant to research and introduce a recycled water harvesting scheme allowing for the irrigation of pitches with recycled water from a range of sources.  Instead of using mains water, the scheme allows rainwater collected from pitch areas and roofing to be stored in four 45 kilolitre underground tanks.  The stored water is treated before use. Overflow from the tanks irrigates the centre's native plants, while the bulk of the water irrigates the hockey pitches.

The new recycled water system will save 19 of the 24 megalitres the State Netball Hockey Centre uses each year on the pitches, reducing its use of drinking quality water by 80 per cent.  The initiative will not only result in significant water savings but will also deliver financial savings for the Centre. (Content supplied by Hockey Victoria).

Carbon dioxide

Carbon footprint

When comparing the carbon footprint of natural grass and synthetic turf the whole life cycle of the product, not just the maintenance component needs to be investigated.  The carbon footprint for natural grass tends to come from the installation and maintenance stage (fertiliser production, mowing and lawn management), whereas for synthetic turf it is derived from production, transportation and disposal of materials.  Synthetic turf is a petro-chemical product which requires the use of virgin materials, high levels of processing and production, transportation and disposal at end of life. When considering the entire life cycle, these material impacts of synthetic turf significantly increase the total emission of this product and far outweigh the emissions that occur from maintaining natural grass.[7]

In 2007, a Canadian study set out to estimate the greenhouse gases emitted during the life cycle of the synthetic turf system as opposed to a natural grass surface. The study also determined the number of trees to be planted to achieve a 10-year carbon neutral synthetic turf installation.  This was a very complicated process and many assumptions were made, but the findings give an indication of the greenhouse gas emissions related to the life cycle (from raw material acquisition through manufacturing, transportation, use and maintenance, and end-of-life disposal) of the synthetic turf field. In conclusion, the study found for a 9,000 square metre facility over a 10-year period, a total CO2 emission of 55.6 tons plus additional greenhouse gases.  The tree planting offset requirements to achieve a 10-year carbon neutral synthetic turf installation for the same sized facility was estimated to be 1861 trees (based on a medium growth coniferous tree, planted in an urban setting allowed to grow for 10 years).[8]

Carbon sink

Natural grass helps remove carbon dioxide from the atmosphere through photosynthesis and stores it as organic carbon in soil, making them important “carbon sinks.” A typical lawn (2,500 sq. ft./232 m2) converts enough carbon dioxide from the atmosphere to provide adequate oxygen for a family of four. [9] There is some recent research from the United States that suggests greenhouse gas emissions from fertiliser production (mowing, leaf blowing and other lawn management practices) are greater than, the amount of carbon that can be stored in them, suggesting that natural grass may contribute to global warming rather than reduce it.  This study also found that athletic sports fields do not store as much carbon as ornamental grass due to soil disruption by tilling and resodding.[10] However, it was later discovered that there were several computation errors in this research and when the computations were corrected, it was found that natural grass actually is a net sequesterer of carbon dioxide, reversing the conclusions of the original report.[11]  This is backed up by another recent US study that concludes “After reviewing the direct carbon sequestration of grasses and their root systems, we found that managed lawns sequester, or store, significant amounts of carbon, capturing four times more carbon from the air than is produced by the engine of today’s typical lawnmower. The study also finds that well-managed turfgrasses (natural) that are cut regularly and at the appropriate height, fed with nutrients left by grass clippings, watered in a responsible way, and not disturbed at the root zone actively pull pollutants from the air, creating a greater carbon benefit.”[12]

It must also be noted that whilst synthetic turf does not require mowing, it still does require ongoing maintenance, often using fuel powered machinery to help keep it clean and performing well.  Ride on mowers with brushes rather than mowing blades are used to brush the surface and leaf blowers are also used to remove leaves from fields. This maintenance equipment produces greenhouse gas emissions but unlike natural grass there is no carbon sink to counter balance it.

Ride on gromming and cleaningFigure 2:  Ride on grooming and cleaning machine with petrol engine used to maintain synthetic turf.

Often artificial turf replaces a natural grass surface, so another contribution synthetic turf makes to global warming is the removal of a natural grass surface that reduces carbon dioxide, by converting it into oxygen. [13]

Materials

Some of the key environmental issues related to synthetic turf revolve around the production, transportation and disposal of materials.

Recycled content

Recycled shock padThe crumb rubber used as infill in synthetic turf fields is often made from recycled tyres. Products made from recycled content are generally preferable to those made from virgin material in two respects, firstly, they do not draw on resources that may be limited, and secondly they address issues of waste.[14]  It is estimated that a large synthetic soccer pitch uses approximately 27,000 tyres.[15]  Many see the use of recycled waste products for field infill as one of the primary environmental benefits of synthetic turf and whilst this is an environmental positive, synthetic turf also requires the use of many virgin materials in its production.34

The shockpad used underneath the synthetic turf can also be made from reused materials.  The shockpad underneath the new facility at Point Cook in Victoria is made from reused running shoe soles. Figure 2:  Shock pad made from recycled sports shoe soles being incorporated into the Australian Rules football and Cricket ground at Point Cooke, Victoria

Material safety

There has been some concern over the use of recycled car tyres as rubber infill.  Whilst it is considered sustainable to use recycled tyres, it has been suggested, but not yet proven, that tyres have the ability to leach out volatile organic hydrocarbons and other toxic materials causing concern for human health (if ingested or absorbed) and also concern over leaching toxic chemicals into soil and groundwater.

A review of existing literature points to the relative safety of crumb rubber fill playground and athletic field surfaces. Generally, these surfaces, though containing numerous elements potentially toxic to humans, do not provide the opportunity in ordinary circumstances for exposure at levels that are actually dangerous. Numerous studies have been carried out on this material and have addressed numerous different aspects of the issue. For the most part, the studies have identified it as a safe, cost-effective, and responsible use for tyre rubber40.

There remain a few objects of concern, though. First, the allergen potential of latex in tyres used for athletic (sports) fields remains obscure. Though there has not been experimental confirmation of the risk of crumb rubber triggering a latex allergy, the possibility cannot be ruled out and needs to be investigated more thoroughly.

Additionally, lead exposure remains an object of some concern. The results of experimental evaluation of lead in these fields have been thus far inconclusive. Most studies have cleared the fields as safe in terms of lead risk, but others have noted an elevated presence of lead.[16] Given the fact that lead levels in tyres varies significantly, according to production processes, it is advisable, as part of the tender process to insist upon suppliers that all materials are lead-free.

Finally, and most significantly, repeated testing has shown that the presence of zinc in leachate from crumb rubber fields remains problematically high. It would appear that levels of zinc leaching into groundwater from crumb rubber fields are significant. Further research needs to be conducted into this question to determine whether it is a real issue, and if it is, greater innovation needs to be carried out at the level of product development to eliminate this issue.40

Given these continual questions and concerns, alternatives to crumbed rubber infill are being sought, the new facility at Point Cook in Victoria has chosen to use round sand sourced from the Middle East as the infill for its facility (Figure 3).  The roundness of the sand means that it is not as abrasive on the player’s skin as other sand particles and it removes any of the concerns outlined above about using rubber infill.

Rounded sand as turf infillFigure 4:  Rounded sand being used as the turf infill in place of rubber granules

Transportation

Generally speaking, synthetic turf is transported long distances (usually all or part of the product is made overseas), whereas ‘instant’ natural grass fields have short shelf lives and can only be transported shorter distances, or are planted from seeds which have minimal transportation costs and the associated reduced carbon footprint.

End of life disposal

Synthetic turf

An additional environmental (and financial) challenge associated with synthetic turf comes in its disposal.  Synthetic turf is not designed to breakdown quickly (that is one of its advantages) which means that when the surface has passed its useful life it has the potential to stay in landfill for long periods of time.

Figure 4:  Disused sand filled synthetic turf waiting for transport to landfill

Recycled shock padEnd of life disposal involves costs associated with removal, transportation and landfill charges (which are generally based on weight, and synthetic turf is a relatively weighty product), making the disposal of a disused surface a significant expense.  It is beneficial to try and re-sell or recycle parts of the synthetic turf wherever possible, for example often community groups can utilise different aspects of an elite playing surface that is being replaced. Whilst this enables the surface to achieve a greater life span it is important to note that this option does not remove the disposal issue, it just delays it, and at some point in time the surface will need to be disposed of.   Currently, in Western Australia, if the surface cannot be reused in any way it ends up in landfill.  There is ongoing research into better ways in which synthetic turf can be removed, cleaned and re-used, or components of it recycled. Currently in the United States and the United Kingdom, there are cement plants that turn disused synthetic turf surfaces into a clean burning energy source by using it to fuel kilns and furnaces in the production of their products.[17] With the increase in the number of fields being installed, this is a technology that may make its way into Australia in the future.

Natural grass surfaces have no end of life costs as it is naturally renewing and regenerating.

Other environmental considerations

Soil regeneration and dust stabilisation qualities

Topsoil takes thousands of years to develop. It is lost quickly by wind and water erosion. Natural grass sends many fine rootlets into crevices of the soil where they grow and, as they decay, add organic matter to the soil.  Natural grass is the most effective plant in conditioning the soil.  Natural grass roots are continually developing, dying, decomposing and redeveloping. By leaving clippings on the lawn and by allowing them to decay, the equivalent of three applications of lawn fertiliser is made. This process builds humus, keeps soils microbiologically active and, over time, improves soils both physically and chemically.  Natural grass improves the soil by stimulating biological life and by creating a more favourable soil structure.

On the other hand, before installing synthetic turf it is recommended that all soil be heavily compacted.  This damages soil structure, soil microbes and soil life.  It can also significantly damage any tree roots in the vicinity.[18]

Healthy, well maintained natural grass helps with dust stabilisation and soil erosion control. Healthy grass surfaces capture dirt and dust from the atmosphere.38 During severe drought periods and tight water restrictions, natural grass can deteriorate and loss of natural grass can create ‘dust bowls’.  During prolonged periods of drought synthetic turf has an advantage in this area.

Heat dissipation

Most synthetic turf surfaces absorb rather than reflect sunlight, causing the emission of heat.  These high temperatures not only impact the surrounding environment, but they can also affect the health and safety of athletes and children who use the synthetic turf grounds.  They can become an uncomfortable playing surface very quickly, especially for summer sports like cricket, tennis and lawn bowls.  (Refer to section 9 for more information on the health impacts of heat related issues).

Recent local research for the AFL and CA, suggests that in hot conditions, an artificial grass sporting area can be up to 40% hotter than a natural field, although this increased heat dissipates quickly on a windy day.[19]

Natural grass plays an important role in controlling climate. Natural grass is one of the best exterior solar radiation control ground covers, because it absorbs radiation and converts it to food for growth through photosynthesis. Natural grass surfaces reduce temperature extremes by absorbing the sun’s heat during the day and releasing it slowly in the evening.44

The replacement of natural grass with synthetic turf has the opposite effect and can contribute to rising temperatures in urban settings, known as the urban heat island effect. Urban heat islands are created when natural grass and trees are replaced by impervious surfaces which absorb heat.  Urban heat islands increase demand for energy (particularly air conditioning), intensify air pollution, and increase heat-related health problems.  Not only does removing natural grass exacerbate the urban heat island effect – most synthetic turf fields absorb rather than reflect sunlight, causing them to emit heat.[20]

Noise and glare reduction

Sun glare

Natural grass provides greater noise abatement and glare reduction when compared with synthetic turf.  Natural grass plants have the ability to absorb sound.  Noise levels are affected by the softness or hardness of the surface over which sound travels.  Because grassed areas present such an irregular soft surface, they are very effective at reducing noise levels.[21]  To help reduce glare from synthetic turf fields it is important in the design stage, that the pitch is orientated correctly to avoid high sun glare during peak playing times, it is also important to place lights in the correct position to avoid glare.

Figure 6:  Sun glare arising from a recently installed synthetic turf soccer pitch in Melton, Victoria

Biodiversity and habitat

Natural grass offers habitats for insects, plants, and other organisms, and provides food for birds.  Natural grass and the topsoil are home to zillions of beneficial organisms that break down and recycle organic and inorganic products that fall into the grass.  Plants absorb gaseous pollutants into their leaves and assimilate them, helping to clean the air and create oxygen. Synthetic turf does nothing to enhance biodiversity, though most synthetic turf fields have drainage systems, they do not contain microorganisms that can break down pollutants.[22]

In conclusion, detailed consideration of a variety of environmental factors needs to be taken into account when planning the installation of a synthetic turf or natural grass surface.  It is advisable to conduct and seek further research and information in this area, as there are many helpful resources available that are referenced but not fully expanded on within this report.

Footnotes 

  1. Synthetic Turf Council USA, 2011. ‘The Environmental Benefits of Synthetic Turf’, http://www.syntheticturfcouncil.org  ( viewed August 2011)
  2. Simon, R, 2010. ‘Review of the Impacts of Crumb Rubber in Artificial Turf Applications’,  University of California, Berkeley, USA.
  3. TurfGrass Producers International, 2010. ‘Natural Grass and Artificial Turf: Separating Myths and Facts’ published by Turf Grass Resource Centre, www.TurfResourceCenter.org viewed August 2011.
  4. Moretto, Dr R, 2007. ‘Environmental and Health Assessment of the use of Elastomer Granulates (Virgin and from used tyres) as infill in Third Generation Artificial Turf’.  Ademe/Aliapur - Fieldturf - Tarkett Publication.
  5. Connecticut Department of Environmental Protection, July 2010. ‘Artificial Turf Study Leachate and Stormwater Characteristics’.  State of Connecticut, USA
  6. State Government Victoria, 2011.  Artificial Grass for Sport, Sport and Recreation Victoria Department of Planning and Community Development, Melbourne, Victoria.
  7. Simon, R, 2010. ‘Review of the Impacts of Crumb Rubber in Artificial Turf Applications’,  University of California, Berkeley, USA.
  8. Meil, J and Bushi L, 2007.  ‘Estimating the Required Global Warming Offsets to Achieve a Carbon Neutral Synthetic Field Turf System Installation’. Athena Institute, Merrickville, Ontario, Canada.
  9. TurfGrass Producers International, 2010. ‘Natural Grass and Artificial Turf: Separating Myths and Facts’ published by Turf Grass Resource Centre, www.TurfResourceCenter.org viewed August 2011.
  10. Townsend-Small, A and Czimczik, C. I, 2010. ‘Carbon Sequestration and Greenhouse Gas Emissions in Urban Turf’ University of California (Irvine). Published in: Geophysical Research Letters (USA) Vol 37, 22 January 2010.
  11. Neighbourhood Nursery, 2010. ‘Error in University Turf Study Voids Negative Conclusion About Turf Grass’. http://neighborhoodnursery.com/error-in-university-turf-study-voids-conclusion/ viewed August 2011.
  12. Sahu R, 2008. ‘Technical Assessment of the Carbon Sequestration Potential of Managed Turfgrass in the United States.  Research Report, USA.
  13. Sahu R, 2008. ‘Technical Assessment of the Carbon Sequestration Potential of Managed Turfgrass in the United States.  Research Report, USA.
  14. Simon, R, 2010. ‘Review of the Impacts of Crumb Rubber in Artificial Turf Applications’,  University of California, Berkeley, USA.
  15. Huber, C, 2006. A New Turf War - Synthetic Turf in New York City Parks’, Research Department at New Yorkers for Parks, New York, USA.
  16. Simon, R, 2010. ‘Review of the Impacts of Crumb Rubber in Artificial Turf Applications’,  University of California, Berkeley, USA.
  17. Target Technologies International Incorporated, 2011. End-of Life solutions for Synthetic Turf: STDF  http://www.ttiionline.com/stdf.htm, viewed July 2011
  18. TurfGrass Producers International, 2010. ‘Natural Grass and Artificial Turf: Separating Myths and Facts’ published by Turf Grass Resource Centre, www.TurfResourceCenter.org viewed August 2011.
  19. Twomey D, Otago L, Saunders N, Schwarz E, 2008. ‘Development of Standards for the Use of Artificial Surfaces for Australian Football and Cricket’. University of Ballarat, Ballarat, Victoria, Australia.
  20. Huber, C, 2006. A New Turf War - Synthetic Turf in New York City Parks’, Research Department at New Yorkers for Parks, New York, USA.
  21. TurfGrass Producers International, 2010. ‘Natural Grass and Artificial Turf: Separating Myths and Facts’ published by Turf Grass Resource Centre, www.TurfResourceCenter.org viewed August 2011.
  22. Huber, C, 2006. A New Turf War - Synthetic Turf in New York City Parks’, Research Department at New Yorkers for Parks, New York, USA.