One of the key differences between recycled steel vs. virgin steel is how sustainable they are. They are both ideal for construction, but which is better for the environment?
With more of us keen to follow sustainable construction techniques and principles, it’s essential to understand the difference between these two types of steel to choose the best for the environment and our projects.
Recycled steel is the best option for construction projects due to its sustainability, strength, and durability. Steel recycling saves between 60 and 74% of the energy used to make virgin steel, and recycled steel retains its structural properties no matter how many times it’s recycled.
In the rest of this article, I’ll compare and contrast recycled and virgin steel to help you choose the best for the environment and your project. From how they’re made and their costs to their environmental impacts, you’ll get everything you need to make an informed decision. Keep reading!
The first difference between recycled and virgin steel stems from their production processes. Let’s look at how each type is made.
Recycled steel is produced from scrap steel instead of raw materials.
Scraps used to manufacture recycled steel come from end-of-life products like cars, cans, and buildings.
Metal recyclers collect these materials in person or from designated drop-off points and deliver them to recycling plants.
Once at the recycling plants, steel scraps undergo the following processes:
- Sorting: While differences between some metals are obvious to the naked eye, tools such as X-ray fluorescence help to ensure the recycled steel is contaminant-free and high-quality.
- Shredding and separation: It involves passing the scraps through a shredder to cut them into smaller sizes for efficient processing. Larger scraps occupy more space and consume more energy. They’re separated based on type: ferrous and non-ferrous.
- Melting: After separation, the scraps are transferred into electric arc furnaces for melting. The furnaces operate at approximately 3,500°C (6,332°F) to turn the steel scraps into liquid. Other components like oxygen and slag foaming agents are added into the furnace to improve efficiency.
- Refining and purification: This step removes impurities like tin, zinc, and lead to ensure the final product is of excellent quality. Magnetism and electrolysis are the most commonly used methods.
- Casting and rolling: The purified molten steel is cast into molds to form ingots for rolling into the final product.
- Quality control: The products undergo quality control tests like metallurgical testing to ensure safer, greener building materials.
Iron ore is the primary material for virgin steel production and is extracted from the earth’s crust through opencast mining.
After extraction, the iron ore is transported to steel manufacturing plants for processing.
The first step in the manufacturing process is pig iron production by melting and converting the iron ore to elemental iron in coke-fired blast furnaces. Limestone is added to the furnaces to remove impurities.
Pig iron settles at the bottom of the furnaces as the impurities form a slag at the top for easy removal.
Pig iron is the primary feedstock in virgin steel production, although practically all steel plants also use up to 30% scrap steel in their mix of raw materials. The raw materials are processed to manufacture steel in one of two ways:
- Basic Oxygen Furnace (BOF): This energy-intensive process combines steel scrap and pig iron in a blast furnace to produce steel. The furnaces operate at high temperatures and lower the carbon content to the required level for steel (typically between 0.25% and 1.25%, depending on the type of steel required). Oxygen is blown into the hot furnace at high speed to oxidize the impurities, including carbon and silicon, which form a slag that is then removed.
- Electric Arc Furnaces (EAF): Also an energy-intensive process for melting steel scraps and ferroalloys to create stainless steel. Oxygen, lime, and fluorspar are then blown into the furnace to purify stainless steel to pure steel.
Cost is crucial when considering the type of material to build with.
The differences in cost between recycled and virgin steel are largely due to their production methods, including the cost of the raw materials and the amount of energy required for the process to operate.
So, is recycled steel cheaper than steel?
Recycled steel is cheaper because its raw materials don’t need to be mined, whereas virgin steel requires iron ore to be mined from large opencast mines. The production of recycled steel is also less energy-intensive than its virgin counterpart, further reducing its cost of production.
Manufacturing virgin steel is an energy-intensive and resource-demanding process. The process uses iron ore and coal, and producing a ton (2,000 lb) of primary steel consumes approximately 6.0 MJ of energy. In contrast, the production of recycled steel uses about 60-74% less energy, as mentioned above.
Virgin steel is not better than recycled steel. Both types of steel are the same chemically and physically, but virgin steel is more damaging to the environment.
Producing virgin steel has the following environmental impacts:
- Landscape degradation: Clearing forests and creating large pits during opencast mining degrades the landscape. It also affects wildlife, water quality and often lowers the water table, reducing groundwater levels and water flows in nearby rivers.
- Energy consumption: The process of producing virgin steel is more energy-intensive.
- Natural resource depletion: Virgin steel uses large amounts of iron ore and coal, depleting natural reserves.
- Greenhouse gas emissions: The production of virgin steel generates gases like carbon dioxide and sulfur dioxide that contribute to global warming.
- Air and water pollution: Dust and runoff from opencast mining pollute the water environment and can compromise local air quality.
Due to the above effects, virgin steel is not an eco-friendly material for sustainable building.
Thankfully, steel doesn’t lose quality when recycled.
The material retains its structural properties like tensile strength and durability. Therefore, you can use it in construction in the same way you use virgin steel – they are identical physically and chemically.
Recycled steel has the same strength as its primary counterpart because recycling doesn’t alter its physical properties.
Scrap melting is the primary process undertaken during recycling. The process transforms the scraps into molten steel, which is then cast and rolled to produce the same product as made using iron ore. Therefore, after cooling, the resulting recycled steel has the same properties as primary steel, including strength.
There are no obvious disadvantages of recycling steel. In fact, steel scrap is normally used even in virgin steel production, where scrap is added into the furnace along with pig iron, which means there is often some recycling going on even in virgin steel production.
One potential impact from recycling steel could arise during the scrap collection and processing steps if, for example, scrap cars are not handled appropriately. Oil and other polluting chemicals must be carefully removed from vehicles during scrapping, which might not always be true.
If these substances spill onto permeable ground, they can enter the environment and cause pollution. However, good management practices can avoid such issues.
Recycled steel is good because it’s strong, durable, and promotes green building practices.
Unlike primary steel, manufacturing recycled steel doesn’t entail opencast mining that degrades the environment. Moreover, recycled steel conserves most of the energy and natural resources used in virgin steel production.
Recycled steel is better than virgin steel due to its strength, durability, and eco-consciousness.
Using recycled steel is an eco-conscious approach that saves money.
Moreover, the material will not compromise your project’s structural integrity because steel retains its properties after recycling. Therefore, as an eco-conscious builder, opt for secondary steel to conserve the environment and save money.