Evaluating the Environmental Impact of Architectural Metals with the Life Cycle Assessment

Metal’s Unrivaled Useful Life

Metal has a longer useful life than other materials. Metal surfaces and structures offer a resilience that withstands the confrontations posed by the weather and human interface.

Metal roofs outlast all other roofing materials. Metal walls will outlast all other materials when correctly designed. And while surface coatings such as paints may fade or chalk over, the metal will last.

Consider the DeYoung Museum of Art in San Francisco, California. Originally made of stone, the museum was damaged in an earthquake. And before, while cutting the material for the museum, the off-fall and miscut stone ended up as waste.

For all its strength and durability, stone lacks resilience and cannot be recycled. Some of the stone was repurposed after the original museum’s demolition. But much of the material went to the landfill.

The new DeYoung Museum is clad in copper. Mismanufactured, damaged, or scrap sections of the copper were recycled. All the perforations were recycled. And because copper metal is more resilient, it will not crack during an earthquake.

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de Young Museum

Herzog & de Meuron developed the idea of a variably perforated screen exterior which would mirror the green foliage and forestry of the surrounding Golden Gate Park, San Francisco's central park. The architects worked with Zahner whose engineers and software specialists developed a system which would allow unique perforation and patterned dimples, variably sized and placed throughout the exterior. This included near 8000 unique facade panels — the collective whole which formed patterns of light as seen through trees. This was the first iteration of the Zahner Interpretive Relational Algorithmic Process, or the ZIRA Process.

Several hundred years from now, when the building’s life is over, the copper will be recycled into new copper, returned for future generations.

A Product’s Five Stages of Life

The Life Cycle Assessment considers five distinct stages in the life of a product. Each stage of the assessment compiles the inputs required from the environment. These inputs include energy, water, packaging materials such as wood, and temporary protective coatings.

Additionally, each stage records any detrimental outputs into the environment. These outputs include landfill waste, air quality effects from dust or VOCs released, and water quality effects such as silt, pH-altering chemistry, and contamination.

Life Cycle Assessment (LCA)

The Mines of Spain recreational area outside of Dubuque, Iowa is an example of reclaimed land. Large lead mining operations occurred here in the 19th and early 20th centuries.

In the late 1970s, the community and the Department of Natural Resources purchased the property and created a park and wildlife habitat that flourishes today.

The extraction of metal from ore requires an extensive amount of energy. Extraction equipment consists of large earth-moving machines, and transportation from the site requires dozens of massive trucks.

The extraction process requires an input of water in the floatation and separation of the ore. Once contaminated with various substances, this water is held in containment ponds and can be considered an output.

Air quality from the dust released in the excavation process and emissions from smelting operations are additional undesirable outputs from the extraction process. However, most mining operations are remote, so the risks of dust are concentrated near the mine.

The Enigma of Metal Extraction

The extraction of ore to generate new metal is, without question, the most detrimental stage to the environment in the Life Cycle Assessment. This introduces a conundrum, as the produced metal has the potential to exist in useful forms indefinitely after this extraction.

Energy used to transform a mineral substance into a refined metal remains ‘locked’ into the material. Corrosion of metals occurs slowly, and for most metals used in architecture, this corrosion adds a protective layer that resists further change.

What’s more, recycling metals has become an industry unto itself. It keeps metals out of landfills and is of such importance that scrap values are established as a market (metal scrap is a traded commodity).

Recycling metals can replace mining and the detrimental characteristics that mining possesses. And it can restore physical and mechanical properties to the point where there is no distinction between recycled and virgin metal.

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The Semantic Metal Surface

When defining a logic to use a particular surface material, various aesthetic qualities such as color, texture, patterns and boundaries are often considered. In our pursuit to arrive at materials that perform over a lifetime and do not possess hidden cost to our children's future, considerations of manufacture and eventual recovery and recycling of the material must also play a part. Architectural metals achieve these design requirements. They are durable and lightweight. They can be formed, shaped, pierced, cut and machined in ways only plastics can attempt to copy.

The energy needed to recycle and restore metal is considerably less than the energy used in the extraction process. There is no damage to the land, and you can find recycling centers in every sizable city around the globe. No other material used in construction can make this claim.

Once melted, the metal scrap or ingots are transformed into large slabs or cylinders before they are shaped under mechanical pressure into plates, sheet metal coils, wire, extrusions, and other structural forms.

These base metal forms may now continue to the next destination, where transporting, stocking and distribution are maximized on flatbed vehicles or containers on a rail.

After arriving at phase two of the manufacturing process, the energy requirements drop significantly. The required inputs are mainly limited to forklifts and large shaping machinery.

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For the average-size factory, the energy required to shear, laser cut, weld, press form, stamp, forge or extrude is equivalent to the energy needed to operate several homes at best.

Material outputs can include wood for the skids and crating, plastic films for protecting the surface, steel banding, and cardboard.

Water is required for some of the finishing operations. But at Zahner, the water is purified and recycled through reverse ionization, so it is not considered a negative output.

Of all the outputs, plastic film is the most problematic. It protects the finished surface, but like so much single-use plastic, it becomes landfill material for a very long time.

Exposed copper develops its green-blue color after it captures sulfur from the air. This mineral layer adds natural beauty and an inert surface that resists change, similar to zinc, which weathers over time by combining with atmospheric carbon and turning a dark gray.

The energy requirements to build with metal products are minimal compared to other options.

Metals are stronger yet lighter than most materials and can offer a more economical structure (greater spans with minimized support attachments). No water nor sacrificial material other than packaging is involved.

When evaluating metals in this stage, it should be assessed with a reduction of the extraction stage because it replaces the need for extraction.

Recycled metal has all the properties of metal made from raw material extraction but at a much lower energy input. Little to no water is required in the recycling process.

On the output side, there is little waste, dust, or damage to our water systems to produce recycled metals. With the exception of removing paints from metals, the air quality is not affected.