Food Packaging -- Glass (Bottles, Jars)

Material Composition Assumptions

The default reference is 1 kg of virgin container glass (soda-lime-silica glass), the standard composition for food and beverage containers:

• Silica sand (SiO2): Approximately 70-72% of batch weight — the primary glass-forming oxide.
• Soda ash (Na2CO3): Approximately 12-14% — acts as a flux to lower the melting temperature from approximately 1700C to approximately 1500C. The thermal decomposition of soda ash releases process CO2 (approximately 0.41 kg CO2 per kg of soda ash).
• Limestone (CaCO3): Approximately 10-12% — provides chemical durability. Also releases process CO2 on decomposition (approximately 0.44 kg CO2 per kg of limestone).
• Minor additives: Alumina, magnesia, colorants (iron oxide for green/amber, chromium for green) — approximately 2-5%.
• Cullet (recycled glass): The default assumes 0% cullet (virgin glass) for the baseline score. Industry practice varies widely: EU average is approximately 52% cullet, US average is approximately 33%.

A standard 750 mL wine bottle weighs approximately 400-500 g; a 330 mL beer bottle weighs approximately 180-220 g; a food jar weighs approximately 200-400 g depending on size.

Manufacturing Geography

The default manufacturing scenario assumes a global weighted average for container glass production:

• Grid intensity (EU): ~300 gCO2e/kWh (average). Europe is a major glass container producer with moderate grid intensity.
• Grid intensity (China): ~565 gCO2e/kWh (IEA 2024). China is a growing glass packaging producer.
• Grid intensity (USA): ~390 gCO2e/kWh (EPA eGRID 2024).
• Rationale: Unlike aluminum, glass production emissions are dominated by Scope 1 direct emissions (approximately 60% of total), primarily from natural gas combustion in the melting furnace and process CO2 from carbonate raw material decomposition. Scope 2 (electricity) is secondary at approximately 18%, meaning grid carbon intensity has a moderate but not dominant effect on total emissions. The furnace fuel type (natural gas vs. fuel oil vs. coal) is the primary variable.

Regional Variation

Manufacturing Region	Furnace Fuel / Grid	Estimated CCI Score	Adjustment vs Default
Global weighted (default)	Natural gas / mixed grid	1.1 kgCO2e/kg	Baseline
EU (high cullet, natural gas)	Natural gas, ~52% cullet	0.75 kgCO2e/kg	-32%
USA (moderate cullet)	Natural gas, ~33% cullet	0.95 kgCO2e/kg	-14%
China (coal furnaces)	Coal or mixed fuel	1.3 kgCO2e/kg	+18%
China (natural gas furnaces)	Natural gas	1.0 kgCO2e/kg	-9%

Note: Cullet (recycled glass) usage has a significant impact on emissions. Each 10% increase in cullet content reduces furnace energy by approximately 3% (cullet melts at a lower temperature than virgin batch) and reduces process CO2 from carbonate decomposition proportionally. EU plants achieve lower scores primarily through high cullet rates (50-90% in some plants).

Provenance Override Guidance

A supplier or brand may override the default CCI score by submitting:

1. Environmental Product Declaration (EPD) or Product Carbon Footprint (PCF) certified per ISO 14067 or the EU PEF method, specifying system boundary, cullet rate, and furnace fuel type.
2. Cullet (recycled glass) percentage used in the furnace batch. Each 10% increase in cullet reduces the score by approximately 3-5%. Plants using greater than 80% cullet can achieve scores below 0.6 kgCO2e/kg.
3. Furnace fuel type and consumption data specifying natural gas, fuel oil, electric boost percentage, or oxy-fuel firing configuration. Oxy-fuel furnaces can reduce NOx and improve thermal efficiency by 10-15%.
4. Glass plant energy data including total thermal and electrical energy consumption per tonne of packed glass.
5. Lightweight container data specifying container weight for the specific packaging format. Lightweighting (reducing glass thickness while maintaining strength) directly reduces per-unit emissions.

Methodology Notes

• CCI score of 1.1 kgCO2e/kg represents a conservative estimate for virgin container glass with natural gas furnaces at a global weighted average. Literature values range from approximately 0.4-1.3 kgCO2e/kg depending on fuel type, cullet rate, and system boundary. The EPA reports U.S. median direct emissions of 0.40 kgCO2e/kg (Scope 1 only); adding Scope 2 and 3 brings the total to the range used here.
• Scope breakdown: Scope 1 dominates at 59% (0.65 kgCO2e/kg), consistent with Saint-Gobain’s report that direct emissions (fuel combustion plus process CO2) account for approximately 75% of Scope 1+2 combined. Furnace fuel combustion contributes approximately 40% of total emissions, and carbonate decomposition (process CO2 from soda ash and limestone) contributes approximately 20%. Scope 2 (electricity for electric boosting, forming machines, annealing lehrs) is 18% (0.20 kgCO2e/kg). Scope 3 (raw material extraction, transport) is 23% (0.25 kgCO2e/kg).
• Functional unit: 1 kg of finished glass food/beverage container, cradle-to-gate. The gate is the annealed, inspected, and palletized container ready for filling.
• Use-phase emissions are excluded. Glass containers have negligible use-phase emissions.
• End-of-life: No credit or debit for recycling is included. Glass is infinitely recyclable without quality degradation. Global container glass recycling rates vary from approximately 33% (USA) to greater than 75% (EU average), with some EU countries exceeding 90%.
• Weight penalty: While glass has a lower per-kg carbon intensity than aluminum or plastics, glass containers are significantly heavier. A 330 mL glass beer bottle (~200 g) has a higher per-unit footprint than a 330 mL aluminum can (~15 g) despite the lower per-kg emission factor. Per-unit comparisons require format-specific analysis.
• Data gaps: Furnace efficiency varies significantly by age, size, and technology. End-port regenerative furnaces, oxy-fuel furnaces, and electric melting have different efficiency profiles. The estimate uses a moderate natural gas regenerative furnace assumption.