Our estimates indicate that — for homeowners who cannot do without turf — artificial turf could be a win-win situation for the environment as water and energy is conserved. For your pocketbook, budget about $10 per square foot, but rebates up to $1 per square foot are available from some water agencies.
The drought and possible mandatory water restriction across southern California are all over the news. The California Department of Water Resources estimates that about 50 percent of the urban residential water is used outdoors (primarily landscape irrigation and some car washing). Urban sprawl and low-density housing developments have resulted in up to 30 percent landscaping in urban areas. To keep these, mostly non-native, plants alive a large amount of water is necessary. The water n even when applied at night – quickly evaporates and transpires as the California sun is beating down. Think of a flood 5 feet high n this is how much water is lost from these landscaped surfaces ever year and becomes ‘gone with the wind’.
I think we can all agree that outdoor water use is less necessary to our well-being than drinking, showers, washing dishes and clothes, and flushing toilets. However, while low-flow fixtures and toilet flushes are mandated in new construction or renovation, only a small fraction of homeowners have targeted water use outdoors. The reason is not a lack of other options: Flowers can be replaced by native plants. (see for example the Water Conservation Garden at Cuyamaca College in El Cajon.) Lawns can be replaced by rock gardens or — artificial turf. Artificial turf (originally known as Astroturf since it was first installed in the Houston Astrodome in 1966) is made out of a black plastic mat, to which dark green plastic filaments are attached. This design is supposed to imitate a healthy lawn, but mowing and irrigation are not required. Athletic fields have remained the primary market for artificial turf, for reasons of increased durability and lowering of maintenance cost (lawn mowing, sprinkler system). For example, several high schools and the University of San Diego have artificial turf fields. The market penetration into the residential market, however, is low. For many homeowners the primary reason for getting artificial turf is winning the battle between a healthy lawn and a dog, since ‘dog irrigation’ will kill grass.
However, the gains in water savings with artificial turf come at a price. The evaporating water from irrigated grass cools the surface to about the same temperature as air. Touch a grass surface in midday and then burn your hand on an asphalt parking lot to witness the effect. Thus for the environmentally conscious consumers, the water conservation argument may have been outweighed by concerns about the chemical components of artificial turf and the heat emitted from artificial turf to nearby buildings and the urban atmosphere.
To holistically evaluate whether grass or turf saves more energy one would need to consider a myriad of factors. Grass consumes energy through lawn moving, fertilizer, water treatment and transport, and landscapers’ trips. Artificial turf consumes energy during production and transport, but since it is often made from recycled materials, the more significant factor is how the heat from artificial turf affects nearby buildings and the temperature in urban areas. (As an aside: A similar catch 22 presents itself for desalination. Desalination supplies fresh drinking water, but at the expense of high energy use). As California has set targets for reduction in greenhouse gas emissions the topics of water and energy become increasingly intertwined. Water uses energy and energy uses water.
In a report submitted to the Journal of Applied Meteorology and sponsored by the Hellman Foundation, my student and I have analyzed the effects of artificial turf on urban air temperature. We have analyzed the — admittedly unrealistic — scenario that all landscaped surfaces covering an estimated 20 percent of the 3,379,658 acres of urban area in California are replaced by artificial turf. If one assumed that all these landscaped surfaces had been covered by grass and irrigated with 50 percent water use efficiency one would obtain a total water use of 6 billion gallons of water on a sunny summer day for California (or 18 thousand acre feet to use the lingo of water managers). The California Energy Commission has estimated that it takes 7 Wh of energy to produce and transport one gallon of water to the consumer (this number is 11 Wh on average for southern California considering the long hilly route from the Colorado river and northern to southern California). So the energy embodied in each gallon of water that we consume is equivalent to turning a compact fluorescent light bulb on for about 30 minutes. Thus the energy used to irrigate grass on a sunny summer day would be 4.3 gigawatthours per day (or 4,300,000 kWh per day), which is about 1 percent of the total average daily electricity use in California. This energy cost is not paid directly by the consumer, rather it is part of the water price charged by the water utilities.