CO, emissions were estimated following a Tier 2 methodological approach available in the 2006 IPCC Guidelines, by multiplying the above-mentioned emission factors to annual activity data on hydrated lime production considering the type of lime produced, the correction factor or the amount of lime kiln dust, LKD representing a mixture of raw materials varying from an uncalcined state to a completely calcined state. Virtually, all types of kilns used to produce lime generate such dust, but the amount depends on the technology applied within the respective factory. It should be noted that the lime kiln dust can be retained by electrostatic precipitation or filtration, and it is possible to return it to the kiln as raw material. Related to CO₂ emissions, any amount of dust that is not returned to the kiln is considered to be a system loss. Table 4-20: Default EFs used to estimate CO₂ emissions from glass production Under this source category are covered GHG emissions originated from the production of different types of glass (flat window glass, multi-layer insulating glass, mirrors, glassware, tableware, specialty glass, etc.). Glass is produced from a raw material mix containing silica (SiO₂), sodium (Na,0), lime (CaO) or other carbonates (CaCO,, CaMg(CO), Na₂CO,, BaCO,, K,CO, SrCO,, etc.), with small admixture of aluminium (AIO) and alkaline substances, plus other minor ingredients. The process of glass production allows for a small quantity of recycled glass (cullet) to be used (its share can vary between 10-80 per cent of the total raw material used). The melting process for different types of glass is similar. The process of glass production implies the following phases: selection and preparation of the raw material, melting, moulding, hardening, quenching, and finishing.