Why Steel?

A lot of people might be wondering why I've chosen steel as the primary building material for my homes. Isn't wood the traditional "greenie" building material, more the sort of thing you would want for that "back to nature" kind of feeling?

There are plenty of reasons.

Steel is plentiful

Steel is basically made from iron with a small amount of carbon. Iron is the most abundant metal in the universe and we're not going to run out. Ever. Steel is therefore very cheap. On the other hand, we are cutting down way too many trees, and if we run out of these, we are, as a species, up the proverbial creek. See the next point.

Trees growing in the dirt have a lot more value than iron ore in the ground

Right now, scientists around the world are trying to figure out how to pull carbon out of the atmosphere. Well, the best technology we have for doing this is trees. They reproduce without our help, plus they look nice, smell nice, and provide food and shelter to our animal friends. It doesn't matter if the trees were planted especially so they could be cut down and turned into houses. With the planet in the state it's in, we really need to stop cutting down all trees right now, and start planting millions more. We need to be using hemp for paper, and steel for buildings.

In the days when trees were plentiful and building materials weren't, cutting down a tree may once have increased its value. Not any more - now it has much more value alive and breathing CO₂. Iron ore, on the other hand, is much more valuable in the form of steel. So, dig it up!

Steel lasts a lot longer than wood

Steel is resistant to termites, and fire and water damage, which means it lasts a lot longer than wood. If you've ever traveled around outback Queensland then you may have noticed that almost every pub has been rebuilt at least once. The reason? Hit by lightning and burned down - which means, all that carbon goes into the atmosphere, and a new building is needed.

Why do old wooden buildings get condemned? Because of water-rot or termite damage. What happens to your wooden doors when it rains? They swell and jam.

These problems don't happen with steel.

Steel is earthquake resistant

The comparison here is with bricks or blockwork. Steel is somewhat elastic, which means it withstands ground vibrations very well. If the vibrations are especially strong then the steel members will deform plastically, but the building won't fall down in most cases. With bricks or blocks however, which are brittle, earth tremors can cause walls to crack and break, and the whole building collapses. Ground subsidence can also cause brick or block walls to crack - but not steel.

Steel is highly recyclable

In fact, steel is one of the most recycled and recyclable materials on Earth. About three quarters of all steel produced is recycled. Old cars, teaspoons, fridges and bridges get tossed into an electric arc furnace, melted, and turned into beams and columns which can then be made into houses. Wood can be recycled, but frequently isn't, and there is much more effort involved. Also, wood can only be recycled so many times. Steel can be recycled again and again and again.

About 97.5% of structural steel beams and plates are recycled (from Wikipedia article on steel). For more information, see this page on recycling at BlueScope Steel or this "Steel is Green" PDF from the Steel Framing Alliance (USA).

Steel results in less material wastage

If you have two short lengths of steel, but need a big one, all you have to do is weld the two lengths of steel together.

It's very hard to do this with wood or bricks. This means lots of small pieces of material are wasted.

Also, when building with wood a large percentage (about 20%) is discarded for being under grade. This means one on every 5 trees is killed for nothing!

Steel results in less tree removal at construction site

Because of the reduced likelihood of fire, there's no need to remove trees close to the building.

Steel allows for much more interesting architecture

This is one of those cases where a picture paints a thousand words. Maybe you could build some of these things out of wood or bricks, but I wouldn't want to!

So, what's the downside?

To be fair, plenty of greenies don't like steel. Here's why:

Mining requires land clearing

True. Mining does often require removal of trees, and these usually aren't regrowth either, but old-growth. However - in the case of steel, because iron is pretty much everywhere, we don't have to mine it where there are trees. We can mine iron in the middle of the desert (and do). This problem is therefore not solved by avoiding steel, but by being more selective about where we get it from.

In any case, the amount of trees that need to be removed to build an iron mine is much less than the amount of trees that would be needed to build the same number of houses that can be built using the metal produced by that mine (whew!). So we're still ahead.

Furthermore, current legislation (in Queensland anyway) means that mining projects almost always need to submit rehabilitation plans for their mining project in order for their lease application to be approved. So, when the mine is complete, the mining company is required to plant thousands of native trees and restore the natural environment. In some cases the mining company actually leaves the land in a better state than it was when they got there.

Steel production uses coal, and produces carbon emissions

True. Traditional steel manufacture involves adding large amounts of coking coal to iron ore in a blast furnace, to reduce the iron oxide to metallic iron. The oxygen atoms in the iron oxide combine with the carbon in the coal to produce our old mate CO₂. More CO₂ is produced in a basic oxygen furnace as carbon levels are lowered.

Also, the problem with coal isn't just about carbon emissions, but also mercury, which ends up in the air and the oceans.

The solution here is not simple. One method which is gaining ground is called direct reduction, which uses natural gas instead of coal, and in which carbon dioxide is captured and recycled. This results in much lower emissions.

A better system would use atmospheric carbon rather than fossil fuels (which, incidentally, is what we will have to do on Mars - go to the Downloads page for my Steelmaking on Mars paper). A steel plant that did this would produce negative carbon emissions, which means under a carbon tax system they might get paid by the government. The question, of course, is whether a system like this can produce steel at an economically competitive rate. While at present this might be difficult, under a carbon tax system it may be possible.

Note that recycled steel does not use coal.

Steel represents greater embodied energy than wood

True. The energy used to produce and transport steel is much greater than that required for wood. It's harder to get iron out of the ground than it is to cut down trees, and then of course it needs to be refined and turned into steel before hot rolling into beams. Trees only need to be taken to the sawmill and sliced up. Steel also often needs to be transported further.

However, because of the benefits explained above, it's still worth this extra cost to use steel (imho).

This disadvantage can be ameliorated by using renewable energy to power steel production. As society shifts towards greater usage of solar, wind, wave and geothermal energy, this issue of embodied energy will become less important. The steel itself is not the issue - energy is.

Steel isn't "natural" - it doesn't biodegrade

True - that's why it lasts a long time, and in any case, it's 100% recycleable.

Steel rusts

A lot of old steel buildings look brown and rusty, so it's understandable that people think that their steel home might end up that way. However, modern construction steel is galvanized (coated with zinc), to prevent rusting. A modern home is much more likely to be recycled long before it rusts.

Steel is cold - wood is warm

Fair enough. But the structural framing components of your house you won't see anyway, so it makes sense to use steel for these, then use sustainable wood paneling on your internal walls if you prefer.