# How do I calculate the carbon footprint of a padlock?

Canonical: https://senseible.earth/answers/padlock-carbon-footprint-per-unit

Weigh the metals in each lock, such as brass, zinc alloy and steel, and multiply each by its supplier's per-kg figure. Add casting, machining, plating, assembly and packing energy, then divide the plant's energy by locks passed.

## Materials

- Body: brass, zinc die cast, iron or steel by weight.
- Shackle, springs and levers in steel.
- Keys in brass or nickel silver.

## Process

- Casting or forging the body, with furnace fuel.
- Machining, polishing and nickel or chrome plating.
- Assembly, testing and blister or box packing.

## Per lock

Report per lock by model and size. Metal is usually the largest share, so record weights from the bill of materials.

## Worked example: lock unit per piece (one month)

- Electricity: 20,000 kWh x 0.710 = 14,200 kg CO2
- LPG: 1,000 kg x 2.98 = 2,980 kg CO2
- Locks passed: 50,000
- Plant total: 17,180 / 50,000 = 0.344 kg CO2 per lock
- Add brass, zinc and steel for the full figure

Inputs are illustrative; use your own bills and production records.

## What Senseible does here

Senseible reads the plant's electricity bills (CEA grid factor 0.710 kg CO2 per kWh, CO2 Baseline Database version 21.0) and fuel invoices (IPCC 2006 defaults) into a fingerprinted Scope 1 and 2 record, the plant-level input to a per-unit figure. Bought-in materials go to the supplier evidence trail; product reports are self-declared drafts.

- [Product carbon footprint calculator](https://senseible.earth/calculators/product-carbon-footprint)
- [Brass component footprint per kg](https://senseible.earth/answers/brass-component-carbon-footprint-per-kg)
- [Electroplating footprint per m2](https://senseible.earth/answers/electroplating-carbon-footprint-per-square-metre)

Sources: [GHG Protocol Product Standard](https://ghgprotocol.org/standards), [ISO 14067:2018, Carbon footprint of products (iso.org)](https://www.iso.org), [IPCC 2006 Guidelines, Volume 2 Energy (fuel defaults)](https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html), [CEA CO2 Baseline Database, version 21.0](https://cea.nic.in/cdm-co2-baseline-database/?lang=en)

Last reviewed 2026-10-20.