We’ve gone through the production processes of steel, aluminium and composites independently and noted their advantages, as well as their shortfalls in regards to the environment. Yet we also require their relative value, in order to be able and identify the preferable option for yacht building.
The primary production of all aforementioned materials stems from ore. Steel originates from hematite, magnetite or siderite. Aluminium is mainly sourced from bauxite, although it is found in other minerals from which extraction is not viable today. Lastly the core components of carbon fibres of composites are sourced from natural gas or oil refinery and the resin is a petroleum product. The largest producers of the ores for steel and aluminium are countries with strict guidelines for mining and recovering of the land, giving some reassurance that nature is protected as much as possible through the extraction. On the other hand oil and gas industry is now targeting pristine locations and such movements have rightfully raised concern.
A very important factor is also the remaining resources of the ores, juxtaposed to the present requirements of the various industries using them. The shortest lifespan is for steel, reportedly vanishing within the next 85 years. Composites come from versatile sources, but taking for example just natural gas, it is estimated that it will go extinct in the next 250 years. Aluminium is in an advantageous position with resources calculated for 1250 years, definitely adding to its appeal.
Taking one step further from the minerals and looking at their manufacturing procedures, there are some parameters prompting our attention. Energy consumption for producing aluminium is 10x the amount required for primary steel production, then again it is between 1/5 to 1/4 the amount consumed for the carbon fibres of the composites. Considering that there are countries like Norway generating 95% of their electric power from hydro, I appreciate that is is a manageable obstacle. Yet the main producers of steel, aluminium and composite don’t have that percentage of their electricity produced from renewable sources.
Moreover these procedures are marred with emissions and by-products hazardous for nature. Both steel and aluminium emit CO2, and the latter is adding in this mix “red mud”, fluoride and rubble. As the process of producing the carbon fibres is protected due to proprietary rights, emission and by-products are not reported. Yet since only 50% of the input material is taken as an output, it is safe to assume that the rest is emitted or left as a residue. Furthermore since the source is relatively harmful, I believe that the result is not benign either.
Fortunately for steel and aluminium there is recycling. The energy consumed is both cases is a lot less, actually in the case of aluminium it is only 5% compared to the one from ore. CO2 emissions are also reduced, for steel only a quarter, but it is adding in some other greenhouse gases. We all understand that this is scrap material that is renewed, which in the case of aluminium is mounts to 85% of the old trash and which counted for 28% of the overall production in 2013. It is another sour point for composites, which have a limited lifespan, no recycling method and are simply adding to the pile of garbage waiting for treatment.
Taking into account the parameters described in the previous paragraphs, aluminium poses as a clear winner, as long as the energy consumption is tackled and considering that its by-products are continuing to be marketed, limiting the negative environmental impact. At the same time though, composites qualities, in respect of strength, weight and thermal performance, add to a tremendous potential for the marine, submarine and space industry. Light structure is paramount for a vehicle in view of using as little fuel as possible. Thin, strong panels are sought after. Also the ability to endure extreme weather conditions are necessary for expanding our horizons.
Concluding we need to make some compromises and plan for the near and further future.
- Since there is available scrap steel, it makes perfect sense to make the best use of it;
- Invest in better manufacturing procedures for aluminium and invent new alloys that improve its qualities. Don’t stop evolution;
- Develop alternative reinforcing fibres for composites, similar approach to that of resin with plant based sources. The objective is to have the attractive, superior qualities of carbon fibres, yet be free (or at least close to free) of all the harmful aspects;