Ceramics & Glassware

Material Composition Assumptions

The default reference product is a ceramic mug weighing approximately 0.35 kg (350 g), or equivalently a glass tumbler weighing approximately 0.3 kg (300 g). The CCI score of 3 kgCO2e applies to the ceramic mug; glass tumblers are approximately 15-20% lower.

Ceramic mug composition:

• Ceramic body: Stoneware or porcelain clay body, approximately 330 g. Composed of ball clay (25-30%), china clay/kaite (20-25%), feldspar (20-25%), and silica (20-25%) by dry weight.
• Glaze: Vitreous glaze coating, approximately 10-20 g. Composed of silica, feldspar, metal oxides (for color), and fritting agents. Applied by dipping or spraying before the glost (glaze) firing.

Glass tumbler composition:

• Soda-lime glass: Approximately 300 g. Composed of silica sand (70-75%), soda ash/sodium carbonate (12-15%), limestone (10-12%), and minor additives. Melted at 1500-1600 degC in a continuous tank furnace.

Both ceramic and glass production are dominated by high-temperature thermal processes — kiln firing for ceramics (1000-1300 degC) and furnace melting for glass (1500-1600 degC). These thermal processes are predominantly fueled by natural gas (or coal in some Chinese and Indian facilities), making Scope 1 emissions the largest single contributor.

Manufacturing Geography

Ceramics and glassware production is concentrated in specific regional clusters:

• China: World’s largest producer of both ceramics (Jingdezhen, Chaozhou, Dehua) and household glassware. Exports the majority of global tableware volume.
• EU: Germany (Villeroy & Boch), UK (Stoke-on-Trent/Potteries), Portugal, and Italy have longstanding ceramic traditions. French and German glassware production (e.g., Arc International, Schott).
• Japan: Premium ceramic production (Arita, Seto, Mino regions).
• Grid intensity (China): 565 gCO2e/kWh (IEA 2024). Used as conservative default.
• Grid intensity (Germany): 350 gCO2e/kWh (IEA 2024).
• Rationale: Kiln firing is the dominant energy input and uses direct combustion (natural gas or coal), making Scope 1 emissions relatively high (40% of total). Grid electricity is used primarily for clay preparation (milling, mixing), forming (jiggering, pressing, casting), and drying. Chinese production often uses coal-fired kilns, which have higher CO2 intensity per unit of thermal output than gas-fired kilns.

Regional Variation

Manufacturing Region	Grid Intensity	Kiln Fuel	Estimated CCI Score	Adjustment vs Default
China — coal kiln (default)	~565 gCO2e/kWh	Coal	3.0 kgCO2e	Baseline
China — gas kiln	~565 gCO2e/kWh	Natural gas	2.5 kgCO2e	-17%
UK (Stoke-on-Trent)	~210 gCO2e/kWh	Natural gas	2.0 kgCO2e	-33%
Germany	~350 gCO2e/kWh	Natural gas	2.2 kgCO2e	-27%
Japan	~460 gCO2e/kWh	Natural gas/LPG	2.4 kgCO2e	-20%

Note: Kiln fuel type has a larger effect on total emissions than grid intensity, because Scope 1 (direct kiln combustion) is the single largest emission source at 40% of total. Switching from coal to natural gas reduces kiln CO2 emissions by approximately 40%.

Provenance Override Guidance

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

1. Environmental Product Declaration (EPD) or Product Carbon Footprint (PCF) per ISO 14067 covering raw materials through finished product.
2. Kiln energy data: Fuel type (natural gas, LPG, coal, electric), kiln efficiency, firing temperature and cycle time. Electric kilns powered by renewable electricity can reduce Scope 1 emissions to near zero.
3. Factory energy data: Renewable electricity procurement for forming and drying stages.
4. Cullet/recycled content (for glassware): Recycled glass (cullet) reduces melting energy by approximately 2.5% for every 10% increase in cullet content. High-cullet glass production (70-90% recycled) can reduce production emissions by 25-40%.
5. Lightweight design: Thinner walls and optimized shapes reduce material use and kiln energy per piece.

Methodology Notes

• CCI score of 3 kgCO2e represents a conservative estimate for a ceramic mug (~350 g) produced in China with coal-fired kilns. WRAP/University of Sheffield (2010) reports 2-4 kgCO2e per mug. Almeida et al. (2016) reports 2-3.5 kgCO2e/kg for ceramic tile, broadly consistent on a per-kg basis.
• Scope breakdown: Scope 1 is unusually high at 40% (1.2 kgCO2e), driven by direct combustion in kilns. Scope 2 is 20% (0.6 kgCO2e) from grid electricity for forming, drying, and finishing. Scope 3 is 40% (1.2 kgCO2e) from raw material extraction, glaze production, and transport.
• Functional unit: One ceramic mug (~350 g), cradle to gate through finished glazed product.
• Glass comparison: A comparable glass tumbler (~300 g) has approximately 2.0-2.5 kgCO2e cradle to gate, lower than ceramics primarily because glass furnaces are more thermally efficient than ceramic kilns and soda-lime glass has lower chemical process emissions.
• Data gaps: Significant variation exists between earthenware (fired at 950-1100 degC), stoneware (1200-1300 degC), and porcelain (1260-1400 degC). Higher firing temperatures increase kiln energy consumption approximately proportionally. The default score assumes stoneware-grade firing.
• Durability context: Ceramics and glass have essentially infinite material lifespans but are fragile. Breakage during transport and use is a significant contributor to lifecycle waste. Per-use emissions depend heavily on product longevity.