Steel + Zinc: The Healthy Metal
Before we examine the impact of hot-dip galvanized steel to the environment, it is import to understand the primary components of the corrosion protection system zinc and iron ore are naturally occurring, abundant elements. Iron ore (steel) is the 4th most abundant element in the Earths crust, and zinc, which comprises 98% of the hot-dip galvanized coating, is the 24th.
Zinc naturally exists in the air, water, and soil as most rocks and many minerals contain zinc in varying amounts. More than 5.8 million tons of zinc are naturally cycled through the environment by plant and animal life, rainfall, and other natural phenomena. The amount of zinc present in the environment varies from place to place and season to season. During the course of evolution, all living organisms have adapted to the zinc in their environment and use if for specific metabolic processes.
In fact, zinc, known as the healthy metal, is essential to life. All living things, from the smallest microorganisms to humans require zinc to live. Zinc plays a critical role in cell division, growth, and wound healing, and also plays an important part in daily, bodily functions such as breathing, digestion, reproduction, and cognition. Of all micronutrients, zinc has the strongest effect on our immune system which can help prevent disease and fight infection.
Although zinc in excess can be detrimental, zinc deficiency is a much greater concern. The World Health Organization (WHO) estimates 800,000 people in developing countries die each year due to lack of zinc in their diet. Children are the most affected by inadequate zinc, and more than half of these annual deaths (450,000) are children under the age of five. To help combat this vulnerability, the International Zinc Association (IZA) partnered with UNICEF to develop the Zinc Saves Kids program (zincsaveskids.org).
Zinc is also common in day-to-day life; in fact, zinc oxides and other compounds are used in a number of household products. In addition to zinc-fortified foods, zinc is found in all sunscreens as zinc oxide blocks more UV rays than any other single ingredient. Zinc is also found in cosmetics, tires, and treatments for sunburn, diaper rash, acne, common colds, burns, and much more. One of the oldest and most common uses for zinc is in construction as a corrosion resistant coating for steel.
Infinitely Renewable Resources
In addition to being natural and abundant, both zinc and steel are infinitely recyclable without the loss of any physical or chemical properties. This means rather than being down-cycled into other, lesser product, zinc and steel can be used as zinc and steel again and again without compromising their integrity. Therefore, hot-dip galvanized steel is a cradle-to-cradle product, as there is essentially no grave for the zinc or steel.
The 100% recyclability of hot-dip galvanized steel is a great benefit to minimizing environmental impact, but it is only half of the story. The ability for both zinc and steel to be recycled is important, but to capitalize on the positive contribution, they must actually be reclaimed for reuse. Therefore it is important to consider both the recycled content, amount of a product produced from recycled sources, and reclamation rate, how often a product is actually recycled at the end of its useful life. Steel is the most recycled material in the world, and zinc has a very high reclamation rate and often the reclaimed zinc and steel are put right back into use.
a International Zinc Association (IZA), Zinc Recycling, 2004. |
b Steel Recycling Institute, Steel Takes LEED® with Recycled Content, March 2009.