In a cement kiln, calcium carbonate (CaCO₃) is broken down to CaO and carbon dioxide. The emission was estimated from the annual UK production of clinker (DETR, 1998d) and an emission factor of 138.3 t/ kt clinker produced (IPCC, 1997). The clinker produced is then ground up with gypsum to produce cement. Since clinker may be imported or exported the production of cement is not precisely related to the production of clinker. Hence it is preferable to use clinker data to estimate carbon dioxide emissions.

Lime (CaO) is manufactured from limestone (CaCO₃ ) and dolomite (CaCO₃MgCO₃) by heating in a lime kiln resulting in the evolution of carbon dioxide. UK limestone use is given in BGS(1999) and an emission factor of 120 t carbon/kt limestone was used based on the stoichiometry of the chemical reaction assuming pure limestone. For dolomite an emission factor of 130 t carbon /kt dolomite would be used, however dolomite calcination data is not given explicitly but included in the limestone data. Hence emissions will be under estimated. Dolomite calcination is believed to be a small proportion of the total hence the over estimate is unlikely to be significant. The limestone calcination data used excludes limestone calcined in the chemical industry since a large proportion of this is used in the production of sodium carbonate by the Solvay process. The limestone is calcined to produce carbon dioxide but nearly all this is recovered and is sequestrated in the sodium carbonate produced. Some of the subsequent uses of sodium carbonate result in the emission of CO₂ (e.g. glass manufacture) but others do not (e.g. water softening). More data on sodium carbonate consumption by use is required before an estimate can be made. Hence the current estimate of lime calcination emissions are low.

Emissions from the use of limestone and dolomite were estimated from the following sources:

• iron and steel manufacture
• glass manufacture
• agricultural soils (liming of soils)

Usage data is available in BGS(1999) and ISSB(1998) for iron and steel use. The emission factors were 120 t carbon/kt limestone or chalk and 130 t carbon /kt dolomite and assume all the carbon is released to the atmosphere.

Sections 2.6.1 and 2.6.2 describe the emission of CO₂ from the degradation of limestone and dolomite used in cement and lime manufacture.

The category cement&lime (fuel combustion) covers emissions of all pollutants arising from the combustion of petroleum coke, coal, oil or natural gas in kilns. In DUKES (DTI, 1998), this fuel consumption is included under 'other industries'. For the pollutants NO_x, CO, PM₁₀ and SO₂ , estimates were based on the emissions for these plant reported by the Environment Agency (1999). For earlier years this data was extrapolated on the basis of clinker production and limestone consumption. The aggregate factors cover all fuels and are shown in Table A10. For the other pollutants, emissions were estimated using default emission factors and fuel consumption data. Fuel estimates were for 1990-1993 (Blyth et al, 1996) and were extrapolated to other years by using clinker production data (DETR, 1998d) and limestone calcination data (BGS, 1999). Having estimated the consumption of coal, fuel oil and natural gas by the lime and cement sector, the fuel consumption by other industry was adjusted so that the total consumption agreed with DUKES (DTI, 1998).

Table A10: Emission Factors for Fuels Burnt in Cement and Lime Kilns

Table A11: Emission Factors for Cement and Lime Production

Estimates were also made of emissions from the combustion of scrap tyres and waste oils in cement kilns. The non-CO₂ factors for scrap tyres are the same as for coal, because this fuel is normally burnt mixed with a larger proportion of coal. The carbon content of scrap tyres was estimated from data in Ogilvie (1995). The fuel consumption was taken from Collingwood (1997).

Some of the uses of sodium carbonate result in the emission of CO₂ (e.g. glass manufacture, food and drink, pharmaceuticals) but others do not (e.g. water softening). Only the emission from soda ash used in glass production is reported. This is based on estimates of the consumption of soda ash in the production of soda glass (British Glass, 1998). This is around 15% of the mass of glass produced. An emission factor of 113 kt C/ Mt soda ash is used

The inventory reports emissions of NMVOCs from asphalt paving and road construction. The emission estimates are based on consumption data of bitumen emulsions, cut-back bitumen and cut-back fluxes. The emission factors used are 7, 87.5 and 700 kg/t for each component respectively. Data is provided by the Bitumen Association. Emissions from asphalt roofing are not reported due to lack of data.

The manufacture of nitric acid produces emissions of both NO_x and nitrous oxide. Up to 1988 estimates of NO_x are estimated from the annual production of nitric acid (CIS, 1991). The NO_x emission factor is 3.98 t/kt of 100% acid produced. This is an aggregate factor based on CORINAIR (1989) emission factors for the different types of processes ranging from 3-12 t/kt of 100% acid produced. The aggregate factor was based on data on UK Manufacturing plant provided by the Nitric Acid Association for the year 1985 (Munday, 1990)

UK production data have not been published since 1988. Since then a number of plants have either closed down, changed ownership, moved or have been fitted with abatement technology. Since 1994 estimates of NO_x were made based on returns from manufacturers. Emissions from 1989 to 1993 were estimated by linear interpolation.

Only Dupont (1998) were able to supply data on nitrous oxide emissions. For the remaining plant, the emissions were calculated from production data and application of the appropriate emission factors. This is an average factor based the range quoted in IPCC Guidelines (IPCC, 1997) for medium pressure plant. From 1995 onwards, a lower factor has been used to reflect abatement measures at some of the plant. Up to 1988, the production data from (CIS, 1991) was used. Since 1994 production estimates based on returns from manufacturers were used. These are based mainly on plant capacity data which may over estimate true production levels. Production from 1989 to 1993 was estimated by linear interpolation.

Adipic acid is manufactured from cyclohexane by oxidation with nitric acid. Nitrous oxide is produced unavoidably with an emission factor of around 300 kg/t of adipic acid produced (IPCC, 1997). Production figures and emission estimates are provided by DuPont (1998).

Emissions of PM₁₀ from mining and quarrying were estimated using USEPA (1997) factors. This gives an average factor of 0.1g/kg of material throughput. Clearly this is a rather crude estimate and so no time series has been estimated.

The UK emissions of SO₂ from sulphuric acid manufacture were supplied by NSAA(1998). ). Emissions of NMVOC, reported for the organic chemical industry are based on the Chemical Release Inventory (Environment Agency, 1999).

The CRI (Environment Agency, 1998a) contains estimates of total particulate emissions from large industrial processes (part 'A' processes). However the CRI is incomplete. Table A9 lists the emissions in the CRI from industrial processes. The increasing trend of the figures is due to the increasing coverage of the database and not a real increase in emissions.

Table A12 1997 CRI Particulate Emissions (tonnes)

An estimate of the total emissions of PM₁₀ of 'about 30 ktonnes' from industrial processes was given in the third report of the Quality of Urban Air Review Group. This estimate was made by taking the total production and using emission factors from the USEPA (1995). However, this calculation is fairly crude. It was compared with the CRI data for 1994 (the latest year at the time). The total for 1994 was 19,764 (since revised by the Environment Agency to 31,064; see Table A9). As the CRI estimate includes all suspended particulates not just PM₁₀ it was thought that the estimate of 32 ktonnes was reasonable.

Now, the CRI includes more sources and the total has been revised upwards. The total for 1996 of 39983 tonnes probably represents less PM₁₀ that the 32000 tonnes quoted above. However, as the CRI does not cover smaller sources it is likely that the current figure is an underestimate. Also the USEPA data has been revised with more detailed emission factors. Work is continuing to match these emission factors to the UK and to revise the current estimates. When this is completed revised estimates for the industrial process sector will be produced.

Natural gas is used as a feedstock for the manufacture of ammonia (for fertilizer), methanol and acetic acid. The largest use is for ammonia manufacture by the steam reforming of natural gas to make hydrogen:

CH₄ + H₂O Û CO + 3H₂

CO + H₂O Û CO₂ + H₂

The hydrogen is then reacted with nitrogen from air to form ammonia

N₂ + 3H₂ Û 2NH₃

If there is no use of the by-products CO and CO₂ formed then these are emitted to atmosphere. The CO is oxidised to CO₂ prior to emission. Hence the CO₂ emission can be estimated from the natural gas usage or the amount of ammonia produced. In principle the emission is 0.97 t CO₂ /t NH₃ produced based on the reaction stoichiometry.

In the UK some ammonia plants are integrated with methanol and acetic acid manufacture for greater efficiency. Thus hydrogen formed as a by-product from acetic acid manufacture is used as the feedstock for ammonia manufacture. Some carbon monoxide and carbon dioxide from the reforming process is used to manufacture methanol. This carbon is sequestrated as methanol and is not emitted to atmosphere.

Methanol is manufactured from natural gas using a process similar to the steam reforming process:

CO + 2H₂ Û CH₃OH

so that all the carbon content of the natural gas is sequestrated as methanol.

Acetic acid is manufactured from methanol and natural gas and again the carbon content of the natural gas is sequestrated.

Two estimates were made:

• The amount of CO₂ emitted from ammonia manufacture
• The amount of natural gas used in the manufacture of products. This can then be deducted from the total combustion of gas by industry in order to calculate the combustion emissions of the non- CO₂ pollutants.

The procedure adopted for the emission of CO₂ from ammonia manufacture was:

1. Data on the plant capacity, natural gas consumption or CO₂ emission from

ammonia plant

acetic acid plant

methanol plant

were collected from manufacturers. This included a breakdown between natural gas used as a feedstock and natural gas used as a fuel.

2. The ammonia capacity of the plants using hydrogen by-product from acetic acid manufacture was excluded.
3. Corrections were made based on manufacturers advice on the 'recovery ' of carbon in methanol manufacture.

The procedure used to estimate the natural gas use as a feedstock was to perform a carbon balance over the three processes:

1. Methanol plant capacity data was used to estimate its natural gas use
2. The natural gas usage of the acetic acid plant was available
3. The natural gas use equivalent to the CO₂ emission from ammonia manufacture was calculated
4. The total feedstock use of natural gas was estimated as the sum of items 1-3

The Inventory includes an estimate of the NO_x emission from the ammonia reformer reported under ammonia combustion. This arises from the combustion of natural gas to produce the high temperatures required by the process. The estimate was based on data provided by the manufacturers.

The necessary data were supplied by Terra Nitrogen, Kemira and BP Chemicals.

Aluminium is produced by the electrolytic reduction of alumina in large pots. During the reduction, the carbon anode is consumed resulting in the emission of CO₂ , SO₂ and other pollutants. In the UK most aluminium is produced by the prebaked anode cell process, though one plant operates the older Soderberg Cell process. Emissions were estimated based on the production of aluminium for each type of process and the carbon emission factors shown in Table A13. The carbon emission factors reflect current practice, and higher emission factors were used for earlier years. For the other, pollutants the same factors were used for each process.

Table A13 Emission Factors for Aluminium Production (kt/Mt Al production)

a CO₂ as carbon, Alcan (1997).

b IPCC (1997)

Emissions from limestone use in blast furnaces are discussed in 2.6.3. The following emissions are also estimated and reported under production processes.

• Iron and Steel Blast Furnaces: CO₂ and other process emissions (see Section 2.5.5)
• Flaring of blast furnace gas
• Electric arc furnaces
• Basic Oxygen Furnaces.

Electric arc furnaces are used in the production of stainless and mild steel and also for recycling scrap. Emissions are based mainly on default emission factors taken from the UNECE/CORINAIR Draft Chapter on electric arc furnaces. The CO₂ emission arises from the consumption of a graphite anode and is based on manufacturer's data.

Large emissions of carbon monoxide have been reported by British Steel (1999). These were allocated to basic oxygen furnaces and sinter plant in proportion to the USEPA (1997) emission factors for uncontrolled plant. Sinter plant emissions are reported under combustion in industry and emission factors are given Table A5.

Table A14: Emission Factors for Electric Arc and Basic Oxygen Furnaces

a BISPA(1997)

b Berdowski et al (1997)

c USEPA (1997)

d Emission factor estimated to be consistent with British Steel (1999).

Emissions of NMVOC are estimated from the hot rolling and cold rolling of steel using emission factors 1 g/tonne product and 25 g/tonne product respectively (EMEP/CORINAIR, 1996). Activity data is taken from ISSB(1998).

The NAEI reports emissions from the following food and drink processing activities. These are reported under Production Processes. Emission factors are listed below and are taken from EMEP/CORINAIR (1996). Activity data for food and drink is taken from ONS(1998) and data on whiskey production is taken from SWA(1998). Bread production data is based on estimates for 1988-1992 published in DTI(1992) which have been extrapolated to other years on the basis of population (ONS, 1998)

Table A15: NMVOC Emission Factors for Food and Drink Processing