Wednesday, February 3, 2010

Green Roofs; by Scientific America

NEW YORK—Through the rain-pocked window of his Prius heading east on the Queensboro Bridge, Stuart Gaffin sees a black, watery sea of missed opportunities.

"Look at all those. Another 100,000 square feet!"

Gaffin, a climatologist at Columbia University's Center for Climate Systems Research, is on his way to the Con Edison power plant in Queens's Long Island City neighborhood. His view from the 40-meter-high bridge is bleak, and not just because of the rain.

"Just sitting there," he sighs. "Useless black roofs."

Since 2003 Gaffin has been studying "green" roofs—those covered with vegetation growing on top of a waterproof membrane—and their potential to mitigate urban climate change.

Like most big cities, New York City is a hot spot, and not just in the cultural sense. The solar energy absorbed into the concrete buildings and asphalt street surfaces is transformed into heat, making it significantly hotter than surrounding rural areas—a phenomenon known as the urban heat-island effect.

Green roofs can cool near-surface air temperatures by an average of 16.4 degrees Celsius per unit area—slightly behind street trees in terms of heat island mitigating potential, according to a 2006 report from the New York City Regional Heat Island Initiative. And the obvious advantage to green rooftops is that they don't take up valuable ground-level space. "Roof space is just this wasted resource," Gaffin explains. "We have somewhere between 30 and 40 square miles [in New York City]—that's 22 times Central Park!"

Although cooling heat islands is an important aspect of urban climate change mitigation, an even bigger impact could come from large-scale energy conservation. That's where green roofs hold gallons of potential. Most of the rainwater dripping off black roofs mixes with pollutants in the streets and wastewater in the sewer system as it flows to 14 water treatment facilities across the city—where it costs money and energy to clean and store. During big storms, that tainted water bypasses treatment plants altogether, pouring contaminants directly into rivers.

A four-inch-thick green roof can hold a gallon of water per square foot. If all the rooftops in the city were green, they would represent a billion gallons of storage potential. Engineering tanks to store that quantity of water is "almost inconceivable," Gaffin says. "There are so many more benefits to this type of approach," he adds. "It's stopping the problem at its source."

Although many like the idea of green roofs, the installation cost ($10 to $35 per square foot, depending on roof size, accessibility for installation, and roofing and drainage components as well as the types of plants) makes them impractical for some buildings.

"There's no argument that painting a roof white is cheaper than installing a green roof," says Chris Brunner, co-founder of New York Green Roofs, LLC. But Brunner says when it comes to reducing storm water runoff and improving air quality, white roofs just don’t stack up.

That's why Gaffin is visiting Con Edison's quarter-acre green roof on this rainy afternoon. Using sensors developed for agricultural research, Gaffin is turning city roofs, like this one on top of New York City's biggest energy provider, into field sites where he can measure the energy and water absorption properties that dictate surface temperature and water storage.

Con Edison's sprawling green roof is covered with sedum plants, hardy succulents that thrive with little maintenance, if any. It is mostly green, except for a raised level that is black with a patch of white. This raised section is used as a control: Energy sensors probe the black and white surfaces to measure their surface temperatures and compare it with those of the planted area, while metered troughs collect water running off the two surfaces. Today, rainwater is cascading down the sides of the control roof.

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Banana This; Recycle Old Peels~ fertilizer or silver polish

There are things you can do with that old peel.

1. Do you have a green thumb? House hold plants and outside gardens require fertilization. A great way to give your plants nutrients is with a banana peel. The banana peel is very rich in potassium and phosphorus, which give that added boost to your plants soil, especially so with roses. Here is how to use a banana peel to fertilizer your soil for your plants. Remove the peel from the banana. Place the banana peel on a cookie sheet to let it air dry. Grab a paper bag or envelope. Crumble the dried banana peel and place it in the bag. Let the banana sit at room temperature for about two days. When your caring for your plant, give it a potassium treat of crumbled banana peel. Mix well in the soil to ensure the roots are fed evenly.
2. Have you been thinking about pulling out that old silver? Well there is no time like the present. Bananas peel can also be used to polish silver. Yes, polish silver. Take the old peels and place them in a blender. You want the peels to become smooth and creamy. Once they have, grab a cloth and small amounts of the creamed banana peel and begin polishing your silver. The shine will be breath taking.


Wild yeasts exist in the air around you and to some extent on the wheat berries. There are wild yeasts on grapes (unsulphured) and apples and other fruits. It is those wild yeasts which are 'captured' to make a sourdough starter. The process takes from 3 to 5 days. I wish I had specific amounts for you, but you could start with 1/4 to 1/2 cup of flour and mix in enough warm (not hot) water to make a thin paste. DO NOT make it too soupy. That, in fact, is the trick to a good starter, according to the French bread makers, and I think they should know. And after you've fooled around with the flour and water thing, you might wish to branch out into adding those unsulphured grapes, apples, sour milk, etc as a catalyst in order to capture other strains of yeast. Each of these strains has a slightly different taste. In fact if you move to another area, you might end up with a starter that produces an entirely different flavor. For instance, San Francisco sourdough bread is well known and has a distinct taste due to the wild strains in the air there. On day one you mix the flour and water (and add any catalysts to encourage fermentation) and place in a warm spot. After 3 days, the dough should be moist, inflated, and slightly sour. More flour and water is added (mixed in) and left to sit in a warm spot. After 2 days the process is repeated. Then the next day it is done again. Note the order: 3 days, 2 days, 1 day. At this point you should be able to make a loaf of bread using part of the starter and adding back what you took out in the form of more flour and water. Rule of thumb: Use about 10% starter to size of loaf. In the case of a 2 lb loaf this is a bit over 3 oz of starter (3.2 to be exact). For a 1 lb loaf 1.5 oz would be used. A book that describes this process in great detail is The Village Baker by Joe Ortiz, copyright 1993, published by Ten Speed Press, Berkley CA. If it's not still in print, try the used books stores, that's where I got mine. Or try your local library. If they don't have it, they might be able to get it for you. ©2008 by Ernestina Parziale

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