Steel

Continuing with our discussion about the many hidden costs of traditional building construction. In this third post, let’s look at unsustainable steel. Steel is one of the world’s most important engineering and construction materials. There is a lot of steel in our homes, it’s so ubiquitous that we rarely even think about it. It’s very strong and relatively inexpensive, making it an excellent structural material for all manner of items. But it has a dark underbelly; steel is very energy intensive to produce and has a significant carbon footprint. Globally, the production of steel is responsible for 6-8% of carbon dioxide emissions.

Unsustainable Steel Production

Steel is an alloy of iron and carbon, with small amounts of other metals added in to produce specific grades of steel. Iron is one of the most abundant elements in earth’s crust, but it is never found in its pure form. Iron is nearly always tightly bound to oxygen, chemically iron oxide, commonly known as rust. The iron oxide is often mixed with quartz and other minerals to form the iron ore found in nature.

The production of steel is a complex process, combining ancient techniques with modern industrial methods. To get to steel, we first need to dig up vast amounts of earth using explosives and huge machines. Then we need to remove the quartz and other minerals just to get to the iron oxide, often done using huge magnets. All this digging and separating uses a lot of energy, usually in the form of diesel fuel.

Blast Furnace

Then we must separate the oxygen from the iron, sort of reversing rust. By far the most common method of reversing rust (known as reduction) is to mix coke, a type of coal, with the iron oxide in a blast furnace. The coke burns intensely hot, stripping the oxygen from the iron oxide, leaving behind pig iron and releasing copious quantities of carbon dioxide gas. Pig iron is high in carbon, about 4-5% carbon, and is too brittle for most applications. See Fig 1.

The next step in the steel making process uses the basic oxygen furnace (BOF) to convert the pig iron into low carbon steel. The BOF blows pure oxygen into the molten pig iron at supersonic speeds to burn out most of the carbon and remove other impurities such as sulfur. The BOF also releases a considerable amount of the CO2. See fig 2.

See this YouTube for an interesting video of the process.

The amount of CO2 ultimately produced depends on the iron mineral used. Like concrete, steel is ultimately unsustainable nor is it a green material.

There are some positive aspects in this process, however. Steel is one of the best materials for recycling. Steel producers can simply be re-melt scrap steel and make into new products. American steel producers, recycle most industrial and commercial scrap steel. But we use far more steel than is available from recycling, so we still produce a lot of virgin steel from iron ore. Other good news are, in Sweden they’ve built a pilot steel plant which uses a new reduction process which nearly eliminates the carbon dioxide emissions from steel production.

Solutions

But there are more good news on this front. By using less concrete as outlined in a previous blog, we will at the same time use less steel. Also, we can look at using non-steel alternatives for the reinforcing bar. There are various fiber-based alternatives available, such as glass fiber, polymers, and basalt. Not only are these alternatives greener and more sustainable, they have other advantages such as corrosion resistance, greater durability, and lighter weight.

Another option for reducing the amount of steel in our homes is to consider using engineered wood support beams instead of the steel I-Beams which have been traditionally used. The new engineered wood beams are very strong, lighter weight than steel, infinitely renewable, and remove carbon dioxide from the air during the tree’s life. This is a much greener and sustainable material than steel.

At Delta Energy Solutions, we are always on the lookout for new ways of doing things. Some solutions include, using less steel, concrete, and other unsustainable materials where possible and substituting unstainable materials with greener, more sustainable materials. It’s not rocket science, but it does require thought from an environmental point of view.