Putting Product Carbon Footprint Accounting into Practice in the Molybdenum Electrode Industry

For the same batch of molybdenum electrodes, two companies may report carbon footprint figures that differ noticeably. The gap does not necessarily come from the process; more often it comes from the accounting basis. Writing the functional unit, boundary and data sources into a one-page statement before accounting begins saves the effort of repeated explanations later.

Functional Unit and System Boundary

A per-tonne unit makes comparison with other molybdenum products easier, while a per-piece unit is closer to delivery and use; converting between the two requires the weight per piece and the yield rate. On boundary, a gate-to-gate basis starting from molybdenum powder purchase is easier to collect, while a full life cycle basis covering raw material acquisition and waste treatment is more complete but depends on supplier data upstream. In the first draft, start with gate-to-gate and extend upstream step by step, so that a data gap does not stall the work from the outset. Once the functional unit is fixed, all subsequent data are collected around it. If customers buy by piece, reporting both per-piece and per-tonne results is more convenient to use, but the two must be mutually convertible and the conversion factor must be stated clearly.

The boundary statement should also set out the cut-off rules, for example whether equipment manufacturing and plant construction are included, and the reason for anything excluded.

Where the Activity Data Come From

• Raw materials: purchase quantities of molybdenum powder and additives, and emission data or composition information provided by suppliers.
• Energy: sub-metered electricity for melting, sintering, forging and annealing, collected by batch.
• Auxiliary materials: consumption records for hydrogen, nitrogen, cutting fluid and packaging materials.
• Transport: mode and distance for incoming raw materials and outgoing products.

Sub-metered electricity is a common gap. If only a workshop total meter is available, consumption can be estimated from equipment power and running hours, but the estimated share must be flagged and replaced with measured values in the next version. Where supplier data are missing, industry averages can be used temporarily, but the substituted share must be flagged and replaced with measured values in the next version. Combining data records with the quality system makes traceability easier.

Divergence in Allocation Methods

When several products share a line, allocating by output, by labor hours or by energy consumption gives different results. Allocation by energy consumption is more reasonable for the melting stage, while allocation by labor hours fits the machining stage better. Once a method is chosen it must be kept consistent, and the reason for the choice stated in the report. How the energy consumption of shutdown and cleaning on shared equipment is allocated should also be agreed in advance; seemingly minor decisions accumulate and change the comparison result. Whether the electricity emission factor is the regional grid average or a supplier-specific value also creates differences; when a market-based basis is used, the attribution of green power and green certificates must be checked with the energy department to avoid double counting.

Order of Improvement from First Draft to Verifiable Result

First unify the functional unit and boundary, then fill in sub-metered electricity and raw material data, then settle the allocation method and factor choice, and only after that move to third-party verification. Reversing the order often leads to rework: if the boundary changes, all previously collected data must be recalculated. Each version of the report should keep a list of parameters and assumptions, stating the data year and the type of source. To discuss the accounting scope for a specific product specification, you are welcome to consult our technical service section.

The value of carbon footprint accounting is not one number but a clear picture of energy and material flows. Only with a stable basis do year-on-year comparisons mean anything, and only then can the result support external disclosure. Before disclosing externally, do an internal review in which people familiar with the process check that the parameters match the shop floor; that saves time compared with submitting for verification directly.