This week’s episode of the green machine is brought to you courtesy of your lawn. Lawns are water hogs and also require a substantial amount of energy for their upkeep. Each day one can see numerous pickup trucks with gardeners traversing Tiburon Boulevard near where I live on their way to mow lawns and blow leaves to the other end of someone’s yard. I often have thought a great name for a landscaping company would be “mow and blow”.
The typical lawn is 5,000 square feet and requires mowing some 30 times a year. The amount of gasoline used for fuelling the mowing machines and the pick up trucks to bring and return the gardeners from and to their distant homes must at least equal 2 gallons each time the gardeners visit us to perform their landscaping chores. This means each lawn requires some 60 gallons of gasoline a year to be kept in pristine condition. 60 gallons of gasoline has a carbon dioxide foot print of about 1,300 pounds. There are approximately 3,000 houses on the Tiburon Peninsular so our collective carbon dioxide footprint for having manicured grass lawns is some 2,000 tons per year.
A 5,000 square foot lawn generates about 1,200 lbs a year of grass clippings. Grass clippings have a carbon composition of 40%. Performing all the requisite and tedious math calculations, these grass clippings took in 1,800 pounds of carbon dioxide via their photosynthesis or carbon dioxide and water. This means that the lawn carbon intake exceeds by almost 50% the carbon emissions of the gasoline used by the gardeners performing the maintenance of the lawn. If the lawn clippings are composted and used as fertilizer, owning a lawn is positive with respect to the carbon aspect of the environment even if one utilizes the services of a gardener who lives far away.
The water footprint of a grass lawn is another matter. Given the long dry summers here in Marin County each homeowner’s lawn requires nearly 50,000 gallons a year of irrigation water. There is an alternate to grass lawns. A company named Fieldturf has developed a synthetic lawn using recycled rubber and sand. http://www.fieldturf.com/ Each square foot of Fieldturf requires 3 pounds of rubber and 7 pounds of sand. The carbon composition of rubber is approximately 90% therefore each square foot of Fieldturn contains 2.7 pounds of carbon. Therefore, the average 5,000 square foot Fieldturf lawn has over 13,000 pounds of carbon that has been sequestered from used tires. The Fieldturf lawn also requires no mowing but will need the occasional blowing. If all the residents of the Tiburon Peninsular changed our lawns to FieldTurf, we would save 150 million gallons of irrigation water a year, and the traffic on Tiburon Boulevard would also be reduced.
There are some 25 million acres of lawn in the USA. http://www.thelawninstitute.org/faqs/?c=183313 This is just more than a trillion square feet of lawn. If the entire US got onto the Fieldturf bandwagon we could recycle almost 3 trillion pounds of old tires. Only 280 million tires that in total weigh 6 billion pounds are sold in the USA each year. http://findarticles.com/p/articles/mi_qn4179/is_20060430/ai_n16483711 Fieldturf will need to wait 500 years to replace all of our grass lawns, but when this happens Goodyear would really have a good year and Sears would never sell another riding mower. The result of today’s analysis is that the grass is greener on the both sides of the hill