Steel Bolt & Nut Set

Material Composition Assumptions

A standard steel bolt and nut set weighs approximately 100 grams total and consists primarily of carbon steel forming the structural components. The bolt shaft, head, and threaded nut represent roughly 95% of the total mass using medium-carbon steel alloy. Hot-dip galvanized variants include a zinc coating layer contributing approximately 3-5% of the component weight for corrosion protection. Stainless steel alternatives incorporate chromium and molybdenum alloying elements that alter both the carbon intensity and manufacturing process requirements compared to standard carbon steel fasteners.

Manufacturing Geography

Steel bolt and nut production concentrates heavily in China, which accounts for the largest global share of fastener manufacturing capacity. Chinese steel production relies predominantly on coal-fired electricity generation, resulting in a grid intensity of 555 gCO2e per kilowatt-hour that significantly influences the manufacturing emissions profile. The combination of integrated steel mills using blast furnace technology and extensive cold forming facilities creates a manufacturing ecosystem optimized for high-volume fastener production at competitive costs.

Regional Variation

Manufacturing Region	Grid Intensity	Estimated CCI Score	Adjustment vs Default
China	555 gCO2e/kWh	2.1	Baseline
Germany	485 gCO2e/kWh	1.8	-14%
India	708 gCO2e/kWh	2.4	+14%
United States	386 gCO2e/kWh	1.6	-24%
South Korea	502 gCO2e/kWh	1.9	-10%

Provenance Override Guidance

1. Steel production method documentation specifying blast furnace basic oxygen furnace versus electric arc furnace routes with actual energy consumption data
2. Recycled content percentage verification for steel feedstock with third-party certification of scrap steel utilization rates
3. Manufacturing facility energy consumption records showing electricity and natural gas usage per unit of fastener production
4. Surface treatment process specifications detailing galvanizing or coating methods with associated chemical and energy inputs
5. Transportation distance documentation from steel mill to fastener manufacturing facility and final packaging location

Methodology Notes

• The CCI score represents cradle-to-gate emissions including raw material extraction through finished fastener production but excludes use phase and end-of-life disposal
• Scope 3 dominance reflects the carbon-intensive nature of iron ore mining and steel production occurring upstream from fastener manufacturing operations
• Functional unit assumes a standard M12 bolt with matching hex nut suitable for structural applications weighing approximately 100 grams total
• Surface coatings and specialized alloys can increase emissions by 15-30% depending on treatment complexity and material specifications
• Regional production route variations between primary steelmaking and recycled content create the largest uncertainty factors in emissions estimation