Green Life and Afterlife

Some common materials, such as certain plastics, are often referred to as "recyclable" and that's factual, they can be recycled: once. At some point the chain-like molecular structure of most plastics break down.

In another example, wood in some life cycle calculations is favored as a rapidly renewable, easily recycled material. But wood, which according to EPA represents 20 to 30 percent of construction waste, is not always straightforward to recycle due to paints, sealants, nails and other possible toxins and the necessity for careful sorting. Even when reclaimed for recycling, used and discarded wood that escapes the landfill will in large part end up as a lower value product such as mulch or feedstock for particleboard.

Zinc is often chosen for its compatibility with other materials. Shown here, Telenor, in Fornebu, Norway. Architect: HUS PKA Arkitekter & NBBJ Architects, Norway. Photo courtesy RHEINZINK America, Inc.

Metallic zinc can be recycled indefinitely without loss of its chemical or physical properties. This theoretically infinite recyclability is, in fact, being approached in reality in the case of zinc used in buildings.

Architectural-grade zinc must be very pure, and so it contains higher percentages of pure ore than industrial-grade zinc. However, once the pure architectural alloy has been created, it can be recovered and reprocessed for use in new architectural products. Some current zinc manufacturers achieve very high levels of this recycled content in their architectural zinc, over 45 percent, almost all of which is post- consumer content. The overall recycling rate for architectural zinc-for example, recovered from renovations and removal from old building-is over 90 percent in some countries because of its high value and the preservation of all its chemical and physical properties. Not all of the old buildings with zinc components were precious monuments to be preserved for all time. Buildings whose zinc parts outlasted them are numerous in Europe. Virtually no zinc on a building ever goes to a landfill.

Recycling of zinc is a well-established industry because products can be recovered easily at the end of their life and there is an extensive network of buyers offering advantageous prices. Even small amounts of scrap zinc generated on jobs are valuable and readily sold.

The amount of energy used to produce zinc from ore is already the lowest of non-ferrous metals, as discussed further below. But recycled zinc conserves approximately 95 percent of that initial energy content. It is also energy efficient to reprocess. Only a fraction-between 0.49 percent and 19.7 percent-of the energy used to produce zinc from ore is necessary to produce zinc from recycled material.

Designing with Zinc: Green into the Future

Architects all over the world have long been in agreement that zinc is beautiful and durable. However, now that the distinct environmental benefits of zinc throughout the life of the building-and well before and beyond-are becoming known, the nature of the cost calculation is changing. The reasons why a zinc roof on the oldest building in a northern European town may be next door to the compound curves and complex geometries of the newest, most innovative building in town are directly related to the environmental benefits of today's zinc alloys.

And some day, when one of the Baron's rooftops is finally removed, it will no doubt go on to another life, with luck in a new building in the future where it will be valued for its sustainability, its durability, its positive response to the atmosphere and environment, and, not least, its enduring beauty.