At the very beginning of a yacht search, the owner needs to choose the type and the size, with the latter being strongly connected to the build material. The range and load of a yacht of 15m is completely different of a yacht of 110m, so their materials have to fit for purpose. The majority of the yachts are built from steel, aluminium and composite and organically there is a threshold for each aforementioned medium, with composites dominating the market up to 35m, aluminium being more dominant up to 50m and thereafter it is the combination of steel hulls with aluminium or composite superstructures.
Noting the above and before getting red flags from readers out there, I respect that there are other materials, like wood for example that are still quite popular for certain traditional types. Yet the mainstream production is around the three aforementioned types. And I also know, not to mention had the pleasure to be onboard the beautiful “Silver” line of aluminium yachts that have a length of 73m and which are sleek and fast, but these are not the standard. And my objective is to concentrate as much as possible to the majority.
From the three popular materials listed above, steel is the favourite in the marine industry, the vast majority of commercial large ships are made of steel and it has been in production over a century, its manufacture has been tested and proven to the most sceptical. Therefore I choose to start my review of materials with it.
Steel, although it has been found in very small quantities as a raw material, it is mainly produced as a secondary product of iron. The latter is also manmade and is sourced from different ores, like hematite and magnetite, all extracted from stones and minerals found in the earth’s crust. Thereafter the ore is subjected to what is called the primary steel making, where the ore is smelted in a furnace that carbon is introduced at temperatures exceeding 1350ºC, resulting to pig iron. The pig iron in what is called the secondary steel making process is further mixed with other elements, including but not limited to manganese, nickel, vanadium, which add to its strength and longevity. As most of you have heard of stainless steel, it is produced through this method by adding among others 11% of chromium.
I realise that the previous paragraph is barely touching the elaborate process, especially of the secondary steel making, which is quite complex and has challenged manufacturers for years in order to achieve the multitude of available alloys. Yet since this is not the subject of the post, I’ve restricted its length and described only the key elements that are needed to understand the evaluation posited below. Nonetheless I strongly recommend those of you that wish to learn more to refer to these sites, thebalance, WorldCoalAssociation, GeoscienceAustralia.
Refocusing on our review for the environmental aspects of steel as a material, I have to point out the following.
- Almost three quarters of the steel produced today still comes from the ore. It is reported that the ore is the fourth most abundant material in earth’s crust, but what does that mean practically in respect of the available resources? Australia has the largest reserves of magnetite and hematite and is the biggest producer today. It is an established economy with regulated mining procedures and measurements of the remaining ore, which was estimated in 2012 to have enough for the next 85 years, with the current demand. Our demand though is constantly rising and the deadline is less than a century away. I won’t live to see that day, but it is not that far in the distant future;
- Simultaneously there is a considerable amount of energy consumed during both the primary (around 13.5MJ per kg) and secondary (around 11MJ per kg) steel making process. Off course it can be done with renewable energy sources, minimising the impact to nature, but still it is up to the manufacturers and states to ensure that;
- Last but not least, during smelting significant quantities of CO2 are released with the known effects of the greenhouse gases;
Luckily there is also that 25% which is made from recycled steel, namely use our scrap or what is called “Direct Reduced Iron” DRI, implement another steel making procedure of the Electric Arc Furnace EAF, not that dissimilar to the ore procedure, but overall more environmentally friendly.
- The basis of this method is existing steel, it is from ships put to rest, revived to be once again a valuable asset, part of a construction;
- From its name one can deduce that it is consuming energy, but the energy required for EAF is one tenth of what is required from the ore, estimated at only 2.25MJ per kg;
- And it is emitting CO2 as well, but only one fourth of what smelting is generating;
So in a more positive outlook and depending on wise management of the existing steel, ready to be thrown away, the world possibly can have enough resources to go by for more than a century to come. Indeed the available resources is the main concern with steel, especially while considering the ever increasing demand for it.