Principal raw materials for cement production are clay and limestone. There are four main process routes for the manufacture of cement: the dry, semi-dry, semi-wet and wet processes. These processes are described in detail in the BAT&BEP Guidance.

Modern cement kilns often use the dry process, in which raw mill material may be pre-heated in a vertically arrayed multi-cyclone pre-heater, in which the rising hot gases exiting the kiln contact the downward flowing raw materials. Some dry processes also employ a pre-calciner stage just before the raw material enters the kiln. The use of the wet process, where the ground meal is mixed with water and fed into the kiln uses about 40% more energy than the dry process. Semi-dry and semi-wet processes use grate pre-heaters, also known as Lepol kilns.

Typical fuels used are coal, oil, gas or petroleum coke. In many cases a variety of alternative fuels derived from high calorific wastes are also used to supplement the fossil fuel. The wastes may include: waste oils, solvents, animal meals, certain industrial wastes, and in some cases hazardous wastes. Most of these will be fired at the burner (hot) end of the kiln. Tires are often used and may be added to the kiln as whole tires or chipped.

Emission Factors

PCDD/PCDF emission factors for four source classes are listed in Table II.4.3. As can be seen, there is no emission factor for releases with residues. Typically cement kilns do not generate residues since the ESP dust is reintroduced and releases via this vector are negligible. Some cement kilns with a high input of chlorine (from wastes or raw materials) have a bypass installed to separate high chlorine containing Cement Kiln Dust (CKD; up to 10% chloride) before the first cyclone. Typically this CKD is sent to specific landfills or underground mines. More information on how process outputs are managed can be found in the BAT&BEP Guidelines. Detailed information on how emission factors have been derived can be found in Annex 35.

Table II.4.3 PCDD/PCDF emission factors for source category 4a Cement Production

4a	Cement Production	Emission Factors (µg TEQ/t cement produced)
Classification		Air	Water	Land	Product	Residue
1	Shaft kilns	5	ND	NA	ND	ND
2	Old wet kilns, ESP temperature > 300°C	5	ND	NA	ND	ND
3	Rotary kilns, ESP/FF temperature 200-300°C	0.6	ND	NA	ND	ND
4	Wet kilns, ESP/FF temperature < 200°C Dry kilns preheater/precalciner, T< 200°C	0.05	ND	NA	ND	ND

Guidance for Classification of Sources

Class 1 includes shaft kilns.
Class 2 includes old wet kilns and with dust collectors operating at temperatures above 300°C.
Class 3 includes modern rotary kilns, where the dust collector is between 200 and 300°C.
Class 4 includes modern plants where dust collector temperatures are held below 200°C.

Activity rates

Activity rates may be obtained from various sources, such as the following:

• Owners/operators of the relevant facilities (by questionnaires);
• State, provincial, national and/or international agencies that gather centralized statistical information, including cement production;
• State, provincial and national agencies that issue permits;
• Other release inventories such as the inventory of heavy metals, criteria pollutants and/or greenhouse gases;
• International statistics such as EUROSTAT, OECD, FAO, World Bank, etc.

Level of Confidence

The emission factors are based on data available from various regions of the world, and are thus assigned a high confidence level.

Lime is used in a wide range of products. Quicklime (or burnt lime) is calcium oxide (CaO) produced by decarbonization of limestone (CaCO3). Slaked lime is quicklime with water content and mainly consists of calcium hydroxide (Ca(OH)2). Major users of lime are the steel industry, construction, pulp and sugar industries.

The lime making consists of the burning of calcium and/or magnesium carbonate at a temperature between 900 and 1,500°C. For some processes, higher temperatures are needed. The calcium oxide product (CaO) from the kiln is generally crushed, milled, and/or screened before being conveyed into a silo. The burned lime is either delivered to the end user in the form of quicklime or reacted with water in a hydrating plant to produce hydrated lime or slaked lime.

Different fuels - solid, liquid, or gaseous - are used in lime burning. Most kilns can operate on more than one fuel. The lime burning process involves two phases (BREF 2010):

1. Providing sufficient heat at above 800°C to heat the limestone and cause decarbonization, and
2. Holding the quicklime at sufficiently high temperatures (around 1,200-1,300°C) to adjust reactivity.

Most of the kilns are either shaft or rotary design. Most kilns are characterized by the counter-current flow of solids and gases. Fluidized bed kilns and rotary hearths may also be found. The typical kiln sizes are between 50 and 500 tons per day (BREF 2010).

Emission Factors

PCDD/PCDF emission factors for two source classes are listed in Table II.4.4. Detailed information on how these emission factors have been derived can be found in Annex 36.

Table II.4.4 PCDD/PCDF emission factors for source category 4b Lime Production

4b	Lime Production	Emission Factors (µg TEQ/t lime produced)
Classification		Air	Water	Land	Product	Residue
1	No dust control or contaminated, poor fuels	10	NA	NA	ND	ND
2	Lime production using dust abatement	0.07	NA	NA	ND	ND

Guidance for Classification of Sources

Class 1 includes plants with poorer combustion and simple or no gas cleaning systems.
Class 2 includes kilns are highly energy efficient and fitted with fabric filter gas cleaning.

Activity rates

Activity rates may be obtained from various sources, such as the following:

• Owners/operators of the relevant facilities (by questionnaires);
• State, provincial, national and/or international agencies that gather centralized statistical information, including lime production;
• State, provincial and national agencies that issue permits;
• Other release inventories such as the inventory of criteria pollutants and/or greenhouse gases.

Level of Confidence

The way the kiln inputs are controlled and maintaining a stable kiln operation is an important factor impacting PCDD/PCDF releases. Emission factors for less controlled processes such as those of class 1 are assigned a medium level of confidence. The emission factor in class 2 is assigned a high level of confidence due to better control of the process and available data.

Brick production with simple kilns, ranging from informal to industrial dimensions, is an important activity in developing and emerging countries. The installations present in various parts of the world have different characteristics. For instance, industrial scale kilns with a large capacity of production (approximately 100 million tons per year) are encountered in South Africa. In Mexico, typical kilns have significantly lower production capacities (around 100 tons per kiln per year), and most often are concentrated in small areas. Kenyan kilns are small size installations, with the output entirely used for own demand.

Various fuels are used, and especially in emerging economies traditional fuels (wood) are often replaced by wastes with high caloric values (oil, tires, plastic). These fuels may promote higher emissions of PCDD/PCDF, PCB and HCB.

Emission Factors

PCDD/PCDF emission factors for two source classes are listed in Table II.4.5. The air emission factors for PCDD/PCDF are the same as in the 2005 edition of the Toolkit. However, high levels detected in ash (around 100 ng/kg PCDD/PCDF TEQ) and bricks (around 10 ng/kg) at one Mexican site using a mix of heavy oil and tree bark indicate the need for further investigations to assess whether these data pertain to another class (Umlauf et al. 2011). However, with regards the bricks, it can be assumed that PCDD/PCDFs are immobilized to a large extent.

Revised or newly added emission factors are highlighted in red. Emission factors for other unintentional POPs are listed in Annex 37. Detailed information on how default emission factors have been derived can also be found in Annex 37.

Table II.4.5 PCDD/PCDF emission factors for source category 4c Brick Production

4c	Brick Production	Emission Factors (µg TEQ/t brick produced)
Classification		Air	Water	Land	Product	Residue*
1	No emission abatement in place and using contaminated fuels	0.2i	-	NA	0.06iii	0.02v
2	No emission abatement in place and using non-contaminated fuels Emission abatement in place and using any kind of fuel No emission abatement in place but state of the art process control**	0.02ii	-	NA	0.006iv	0.002vi

* In countries with no waste management or no reuse of the residue for brick making, this often goes to Land.
** For brick kilns with state of the art process control, such as the Hoffmann type, it has been demonstrated that co-incineration of waste does not promote emissions of PCDD/PCDF when compared to the use of coal (Ubaque et al. 2010).
ⁱConfirmed/derived with field measurements at Mexican artisanal brick kilns using waste oil
ⁱⁱConfirmed/derived with field measurement at Mexican Kilns using virgin wood
ⁱⁱⁱDerived from field measurements at Mexican artisanal brick kilns using waste oil
^ivDerived from coal and virgin wood fired brick kilns in Mexico, South Africa at industrial and artisanal scale
^vDerived from Mexican artisanal brick kilns fired with contaminated fuels
^viDerived from virgin wood and coal fired kilns in Mexico, South Africa and Kenya at industrial and artisanal scale

Guidance for Classification of Sources

Class 1 factors should be applied to smaller and less controlled kilns with no gas cleaning technology.
Class 2 includes technologies with no emission abatement in place and using non-contaminated fuels, those using emission abatement and any kind of fuel, and with no emission abatement in place but state of the art process control.

Activity rates

Activity rates may be obtained from various sources, such as the following:

• Owners/operators of the relevant facilities (by questionnaires);
• State, provincial, national and/or international agencies that gather centralized statistical information;
• State, provincial and national agencies that issue permits;
• State, regional or national construction and commerce chambers;
• Other release inventories such as the inventory of heavy metals, criteria pollutants and/or greenhouse gases;
• IPCC databases may be also considered to assess activity rates;
• Energy efficiency programs and projects databases may help to assess activity rates and identify implementation of upgraded kilns. Because of recent interest in controlling emission of black carbon, changes in brick production may happen towards more efficient and even emission control in the kilns (UNEP 2011a).

Additional guidance on estimating activity rates for artisanal brick production is included in the example inventory 5.

Level of Confidence

No other reports from artisanal kilns have been produced regarding POPs. The data used to derive the emission factors to air were produced via two experiments with partial geographical coverage. Emission factors to land and residues have a broader coverage. In particular, kilns typical to China and other Asian countries were not assessed. Because of energy efficiency programs, continuous types of kilns are being implemented in Asia, Africa and in the near future in Latin America. Based on the above, the level of confidence assigned to emission factors for class 1 is high to medium, and for class 2 is medium.

Furnaces used for glass manufacture may be continuously or intermittently operated. Typical fuels are oil and gas. The raw materials are principally sand, limestone, dolomite, soda, and in some cases recycled glass. In addition a wide range of other materials may be used to achieve desired properties such as color, clarity, and for purification. Chlorinated and fluorinated compounds may be added (SCEP 1994). In some modern glass furnaces, gases are cleaned with sorbents and electrostatic precipitators or fabric filters.

Emission Factors

PCDD/PCDF emission factors for two source classes are listed in Table II.4.6. Detailed information on how these emission factors have been derived can be found in Annex 38.

Table II.4.6 PCDD/PCDF emission factors for source category 4d Glass Production

4d	Glass Production	Emission Factors (µg TEQ/t product)
Classification		Air	Water	Land	Product	Residue
1	No dust control or contaminated, poor fuels	0.2	NA	NA	ND	ND
2	Glass production using dust abatement	0.015	NA	NA	ND	ND

Guidance for Classification of Sources

Class 1 includes furnaces with no dust controls which use poor, contaminated fuels.
Class 2 includes furnaces using dust abatement.

Activity rates

Activity rates may be obtained from various sources, such as the following:

• Owners/operators of the relevant facilities (by questionnaires);
• State, provincial, national and/or international agencies that gather centralized statistical information, including glass production;
• State, provincial and national agencies that issue permits;
• Other release inventories such as the inventory of heavy metals, criteria pollutants and/or greenhouse gases.

Level of Confidence

Emission factors are provided with a medium level of confidence, based on the limited geographical scope of available data.

There is not enough information available to consider the production of ceramics as a source of PCDD/PCDF. As ceramics production is a thermal process, PCDD/PCDF will most likely be released to air. An estimate of these releases can be made by applying the emission factors developed for brick making.

Asphalt is generally used for road construction, and consists of rock chips, sand, fillers bound together in bitumen. Fillers can include fly ash from incineration or power plants. The first stage of the process is generally an air-drying unit for the minerals. The hot minerals are then mixed with hot bitumen to obtain asphalt. Asphalt mixing plants in industrialized countries may typically have gas cleaning such as fabric filters or wet dust control devices.

Emission Factors

PCDD/PCDF emission factors for two source classes are listed in Table II.4.7. Detailed information on how these emission factors have been derived can be found in Annex 39.

Table II.4.7 PCDD/PCDF emission factors for source category 4e Asphalt Mixing

4e	Asphalt Mixing	Emission Factors (µg TEQ/t asphalt mix)
Classification		Air	Water	Land	Product	Residue
1	Mixing plant with no gas cleaning, poor fuels	0.07	NA	ND	ND	ND
2	Mixing plant with fabric filter or wet scrubber	0.007	NA	ND	ND	0.06

Guidance for Classification of Sources

Class 1 includes installations without gas cleaning systems or using poor or contaminated fuels.
Class 2 includes modern asphalt mixing installations fitted with fabric filter or wet scrubbers for gas cleaning.

Activity Rates

Activity rates may be obtained from various sources, such as the following:

• Owners/operators of the relevant facilities (by questionnaires);
• State, provincial, national and/or international agencies that gather centralized statistical information, including on road construction;
• Oil refineries producing asphalt.

Level of Confidence

Emission factors are provided with a medium level of confidence, based on the limited geographical scope of available data.

Oil shale is a general term applied to a group of fine black to dark brown shales rich enough in bituminous material (called kerogen) to yield petroleum upon distillation. The kerogen in oil shale can be converted to oil through pyrolysis. During pyrolysis the oil shale is heated to 500°C in the absence of air and the kerogen is converted to oil and separated out, a process called "retorting". The term "oil shale" is a misnomer. It does not contain oil nor is it commonly shale. The organic material is chiefly kerogen and the "shale" is usually a relatively hard rock, called marl. Properly processed, kerogen can be converted into a substance somewhat similar to petroleum. However, oil shale was not converted into “oil” by natural processes and therefore, oil shale has to be heated to a high temperature to become fossil fuel (WEC 2004).

There are two conventional approaches to oil shale processing (WEC 2004): in the first one, the shale is fractionated in-situ and heated to obtain gases and liquids. The second approach is by mining, transporting, and heating the shale to about 450°C, adding hydrogen to the resulting product, and disposing of and stabilizing the waste.

Oil shale has been burned directly as a fuel in a few countries such as Estonia, whose energy economy remains dominated by shale. For emission factors in the oil shale fired power plants, see source category 3a Fossil Fuel Power Plants.

Emission Factors

PCDD/PCDF emission factors for two source classes are listed in Table II.4.8. Detailed information on how these emission factors have been derived can be found in Annex 40.

Table II.4.8 PCDD/PCDF emission factors for source category 4g Oil Shale Processing

4g	Oil Shale Processing	Emission Factors (µg TEQ/t oil shale)
Classification		Air	Water	Land	Product	Residue
1	Thermal fractionation (process 1)	ND	ND	ND	ND	ND
2	Oil shale pyrolysis	0.003	NA	ND	0.07	2

Guidance for Classification of Sources

Class 1 includes thermal fractionation process.
Class 2 includes oil shale pyrolisis.

Activity Rates

Activity rates may be obtained from various sources, such as the following:

• State, provincial, national and/or international agencies that gather centralized statistical information;
• National energy balance;
• Owners/operators of the relevant facilities (by questionnaires);
• State, provincial and national agencies that issue permits.

Level of Confidence

Emission factors are provided with a medium level of confidence, based on the limited geographical scope of available data.