When conducting an LCA (Life Cycle Assessment) that includes metals, using accurate datasets is an important step for obtaining reliable results. Ecoinvent offers a comprehensive database for modeling metals, but with so many options, it can be helpful to follow a structured approach. This article offers a step-by-step guide to modeling metal materials and components using ecoinvent datasets.
Don't feel like reading an article? Watch a video tutorial on this topic instead!
Feel like you're missing information? This article builds upon the following articles, check them out if you want to learn more:
On adding impact in Mobius: Mobius - How to: Add impact to your model using datasets
On adding impact in Helix: Helix- How to: Company level inputs
On ecoinvent datasets: Explained: Ecoinvent datasets
On modeling materials with multiple datasets: How to: Model materials with multiple datasets
Step 1: Find a dataset for the raw metal
You often need multiple datasets when modeling metals using ecoinvent. Typically, you'll need one dataset for the metal itself (step 1) and another dataset (step 2) to model the specific processing method used to shape the metal into its final form. This is necessary because metals are often purchased in a processed form, and each step—material production and processing—contributes distinctly to the overall environmental impact of the product in an LCA.
Step 1a: Determine the type of metal
First, identify the type of metal you're working with. Ecoinvent has an extensive list of available metals, which includes, but is not limited to steel (unalloyed, low alloyed, chromium steel), iron, precious metals (platinum, gold, silver), and non-ferrous metals (copper, aluminium, lead, nickel).
If you know the exact type of metal (or alloy), search for that material in the ecoinvent database.
Pro tip - Metal synonyms: Some metals might have synonyms in the database. For example, stainless steel is listed as chromium steel in ecoinvent. If you don't find the specific metal, try searching for synonyms of common alloys or metal grades online. Similarly, some alloys are too granular so ecoinvent groups them into types. Consider checking what group a specific alloy falls under.
Step 1b: Determine whether the metal is primary or secondary
Next, determine whether the metal is primary or secondary. The two have different production methods and environmental impacts. Therefore, they have separate dataset types.
Primary metals are produced from raw materials (e.g., iron ore for steel). For example, primary steel is often produced in a blast oxygen furnace. Primary metals are often identified in ecoinvent with the word ‘converter’.
Secondary metals are recycled metals. Secondary steel, for example, is produced via an electric arc furnace. Secondary metals are often found in ecoinvent with the word ‘electric’.
Note - Distinction between primary and secondary metals: If you're unsure whether the metal is primary or secondary, you can use a market dataset to capture a regionally representative mix of primary and secondary metals.
Step 1c: Select a metal dataset
Select a metal dataset using the information gathered in the previous steps on the type of metal and whether it’s of primary or secondary origin. Table 1 provides examples of datasets for common raw metals.
Table 1: Ecoinvent datasets for raw metals.
Raw Metal | Ecoinvent Dataset |
Unalloyed steel | Steel production, converter, unalloyed | steel, unalloyed | Cutoff, U |
Low-alloyed steel (virgin) | Steel production, converter, low-alloyed | steel, low-alloyed | Cutoff, U |
Low-alloyed steel (recycled) | Steel production, electric, low-alloyed | steel, low-alloyed | Cutoff, U |
Stainless steel | Steel production, electric, chromium steel 18/8 | steel, chromium steel 18/8 | Cutoff, U *The majority of stainless steel nowadays is made using recycled steel, with some fresh alloys as additives. For this reason, ecoinvent only has an ‘electric’ dataset available for stainless steel. |
(Cast) iron | Cast iron production | cast iron | Cutoff, U |
Platinum | Platinum group metal, extraction and refinery operations | platinum | Cutoff, U |
Gold | Market for gold | gold | Cutoff, U |
Silver | Market for silver | silver | Cutoff, U |
Copper | Market for copper-rich materials | copper-rich materials | Cutoff, U |
Aluminium | Market for aluminium, primary, ingot | aluminium, primary, ingot | Cutoff, U *Keep in mind that there are many different aluminium alloys - this might not be the right fit for every case) |
Lead | Primary lead production from concentrate | lead | Cutoff, U |
Nickel | Market for nickel concentrate, 16% Ni | nickel concentrate, 16% Ni | Cutoff, U |
Note - Dataset selection: All datasets listed in Table 1 exist as ‘production’ and ‘market for’ datasets. Similarly, these datasets are available for several regions (Europe, Rest-of-World, or Global). Consider this when deciding which dataset to use.
Caution- Recycled metals: Ecoinvent has many datasets available for primary metals. However, ecoinvent has a limited selection of recycled secondary metals datasets. Contact the Ecochain Helpdesk if you’re determining the environmental impact of recycled metal. Our environmental specialists can help you!
Step 2: Find a dataset for the metal processing method
Step 2a: Determine the metal processing method
Once you've found a dataset for the raw metal, the next step is to model the processing. Metals are often purchased in a processed form, so you'll likely need a second dataset for manufacturing steps like:
Hot rolling
Casting
Forging
Laser cutting
Sheet rolling
Impact extrusion
Welding
Note - Metal processing: If you're unsure which processing method is used, you can:
Research common manufacturing practices for your metal component.
Opt for the Average Metal Working dataset in ecoinvent. While this approach is less precise, it still gives a good approximation of the environmental impact. These datasets exist for different metals like copper, aluminum, steel, and chromium steel.
Caution - Excluding processing: A metal material dataset essentially represents a ‘block’ of that metal. It is unprocessed. It does not represent a finished metal component. Excluding or ignoring the processing of the metal results in an underestimation of the impact associated with the metal component.
Step 2b: Select a metal processing dataset
Select a metal processing dataset using the information gathered in the previous step. Table 2 offers examples of common metal processing datasets.
Metal Processing Method | Ecoinvent Dataset |
Hot rolling | hot rolling, steel | hot rolling, steel | Cutoff, U |
Casting | casting, brass | casting, brass | Cutoff, U |
Forging | forging, steel, large open die | forging, steel | Cutoff, U |
Laser machining | market for laser machining, metal, with CO2-laser, 5000W power | laser machining, metal, with CO2-laser, 5000W power | Cutoff, U |
Sheet rolling | sheet rolling, copper | sheet rolling, copper | Cutoff, U |
Impact extrusion | impact extrusion of steel, cold, tempering | impact extrusion of steel, cold, tempering | Cutoff, U |
Welding | welding, gas, steel | welding, gas, steel | Cutoff, U |
Metal working | market for metal working, average for metal product manufacturing | metal working, average for metal product manufacturing | Cutoff, U |
Step 3: Check your results
After selecting your material and processing datasets, double-check that the units (e.g., kilograms) match across all selections. Misaligned units can lead to incorrect impact results.
This is especially important for the processing datasets, as these can differ from the usual ‘mass, kg’ unit. Processing datasets can be measured in time (hours), or length (meters), amongst others.
Video tutorial
Watch these concepts explained in our Mobius software:
Next steps
Modeling metals with ecoinvent is a step-by-step process where you need to know the type of metal, whether it is primary or secondary, and model the appropriate processing method. If you need further assistance with finding a proper metal dataset, consult your environmental specialist or contact the Ecochain Helpdesk!
Good luck with your metal modeling in LCA!