Facility Profile - March 2010
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Bottom's Up!

Morton Arboretum in Lisle, IL.

By Dawn Klingensmith

It might be a stretch to say that drinking beer helps trees, or that beer is good for ecosystems. But at the Morton Arboretum in Lisle, Ill., beer bottles play a starring role in an eco-friendly project that calls for a celebratory toast.

As reporters looked on, a work crew in September poured a 1,000-square-foot walkway made of crushed, recycled beer bottles, other glass and bits of granite. The arboretum is testing this recently developed, highly porous pavement, called FilterPave, as part of its mission to protect trees and the environment.

FilterPave was designed to be "exceedingly permeable," said Bill Handlos, director of Appleton, Wis.-based manufacturer, Geosystems, a Presto Products company. "More water will go through this than through a lawn or grass."

Porous pavements help the environment by trapping pollutants and keeping them out of the groundwater. On a traditional surface such as asphalt, pollutants are usually swept away by rainwater and deposited into storm drains, detention areas and streams.

So, does this make FilterPave a "cutting-edge" product? Yes and no.

"Everyone is so concerned when they hear it's glass that kids are going to get cut up on it," said Kris Bachtell, the arboretum's director of collections and facilities.

But in fact, the glass has been specially processed to round its edges and is as structurally sound and safe as any traditional surface, according to the manufacturer. The tumbled bits of 100 percent post-consumer glass come out almost cube-like in shape, with no pointy edges. The glass is then mixed and held together with a pliable, elastomeric binder and has "kind of a Rice Krispie bar look to it" when it's poured in place, Handlos said.

The decorative, durable surface is about 40 percent porous. By comparison, the porosity of asphalt ranges from 18 percent to 23 percent, he said.

In addition to filtering stormwater, porous pavement can reduce the heat island effect by trapping and mitigating heat, rather than reflecting it, as a blacktop surface does. Tree roots benefit when pavement and the soil surrounding it are cooler.

The systems also benefit the environment by diverting recycled glass from landfills. Most folks probably don't realize that the glass bottles they clean and sort often don't get recycled. Instead, they are ground up and used to cover landfills, partly as a means of discouraging scavenger birds.

FilterPave consists of about 90 percent recycled glass. Up to 90 beverage bottles are used in just one square foot.

FilterPave is available in Sedona red, sapphire blue, jade green, amber brown and topaz brown, with optional color enhancements. The Morton Arboretum's walkway is amber brown, which complements the natural surroundings and glitters in the sun. The colors can be traced back to the beer brands they represented in their previous life. Heineken and Rolling Rock bottles make up the green aggregate, while Budweiser, Amstel Lite and other brands go into the amber-colored mix. But though the poured pavement looks like a solid color from a distance, closer inspection reveals that it's multicolored, like a mosaic.

"At nighttime, it looks so nice on a lit path—almost like polished terrazzo," said John Donahue of Frankfort, Ill.-based Emerald Site Services, which donated the materials and labor for the Morton Arboretum project.