2.2 CO₂ Emission Estimates

Carbon dioxide emissions have reduced by around 15% since 1970, as shown in Figure 2.2. However, this decline has not been steady, and peaks were observed in 1973 and 1979 which were due, to the state of the economy, high oil prices and severe winters in these years. Emissions fell again during the early eighties reflecting the recession during this period and the coal miners strike of 1984. Since the mid-1980s the emissions profile has been much smoother showing an overall reduction in emissions.

The major emissions of carbon dioxide arise from the combustion of fossil fuels in power generation, and the transport, domestic and industrial sectors (Figure 2.2, Table 2.2). The level of emissions depends on the fuel mix and the fuel consumption data. Details of UK fuel consumption are given annually in the Department of Trade and Industry's Digest of United Kingdom Energy Statistics (DTI, 1997). The fuel consumption data used to calculate the pollutant emission totals in the NAEI is given in Table 2.3; fuels which are used as feedstocks are omitted (principally natural gas used for the production of ammonia, methanol and acetic acid and some use of LPG and OPG in petrochemical plants).

Table 2.2 UK Emissions of Carbon Dioxide as Carbon by UNECE¹ Source Category and Fuel (Mt)

	1970	1975	1980	1985	1990	1993	1994	1995	1996	1996%
By UNECE Source
Comb. in Energy Prod & Transf.
Power Plant	57.0	56.5	58.3	51.9	54.1	45.5	44.3	44.0	43.4	28%
Petroleum Refining Plants	5.2	5.2	5.6	4.7	4.9	5.6	5.6	5.7	5.8	4%
Other Combs. & Trans.	8.2	3.5	2.8	3.9	3.9	3.9	4.4	4.7	5.2	3%
Comb. in Comm/Inst/Resid/Agri
Domestic	26.5	22.6	23.3	24.2	21.5	24.2	22.9	21.7	24.7	16%
Other	10.3	8.8	9.9	9.9	8.4	8.8	8.7	8.8	9.4	6%
Combustion in Industry	47.7	38.4	30.0	24.0	24.6	23.9	24.0	23.5	23.9	15%
Production Processes	4.9	5.1	4.2	4.7	4.0	2.8	3.3	3.1	3.2	2%
Extr./Distrib. of Fossil Fuels	0.1	0.1	0.1	0.3	0.4	0.1	0.2	0.2	0.2	0%
Solvent Use	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0%
Road Transport
DERV	4.3	4.6	5.0	6.1	9.1	10.1	11.1	11.5	12.3	8%
Petrol	11.7	13.3	15.9	17.1	20.4	20.0	19.2	18.4	18.8	12%
Other Transp & Mach.
Off-Road	2.5	2.4	2.1	2.0	1.7	1.8	1.7	1.6	1.7	1%
Other2	3.3	3.4	3.4	3.4	3.6	3.5	3.3	3.2	3.2	2%
Waste Treatment & Disp.	0.2	0.3	3.3	2.1	2.2	1.9	2.5	1.8	1.9	1%
Agricult/Forest/Land Use Change	0.5	0.5	0.4	0.5	0.4	0.3	0.3	0.4	0.4	0%
Nature	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0%
By Fuel
Solid	90.3	67.5	70.6	60.8	61.4	49.4	46.1	42.9	39.9	26%
Petroleum	67.5	65.6	58.0	54.5	56.6	56.5	55.3	53.9	55.1	36%
Gas	20.4	27.6	29.6	34.1	35.7	41.8	44.5	47.2	54.2	35%
Non-fuel	4.0	4.1	6.4	5.3	5.7	4.6	5.4	4.9	5.0	3%
Total	182.3	164.8	164.5	154.7	159.4	152.3	151.4	148.9	154.2	100%

1 UK emissions reported in IPCC format (Salway, 1998) differ slightly due to the different source categories used.
2 Railways, civil aircraft, shipping, naval vessels and military aircraft.

Figure 2.2 Time Series of CO₂ Emissions

The electricity supply industry is the major consumer of fossil fuels, and hence the major source of carbon dioxide emissions in the UK (Tables 2.2 and 2.3). There have been significant changes in the generating mix between 1980 and 1996, as shown in Figure 2.3. The level of CO₂ emissions is determined by both the fuel mix and the generating technology used. During the 1970s the electricity supply industry was dominated by coal and fuel oil fired thermal power stations, and coal and oil consumption increased to meet the rising demand for electricity. The use of coal for generation peaked in 1980 at 89.6 Mt and has subsequently declined. The fall has not been steady showing minima in 1982 and 1984 due to recession in the early 1980s and the miners strike. During the late 1980s and early 1990s, the closure of inefficient plant led to an overall increase in the thermal efficiency of the conventional thermal power plants, and the contribution of nuclear power generation increased with the greater utilisation of existing nuclear plants and the commissioning of Sizewell B in 1991. The use of oil generation peaked in 1972 and apart from increased consumption during the miners strike of 1984 has been in decline ever since. Two oil-fired stations have been converted to burn Orimulsion^® (an emulsion of bitumen and water) although this practice is in decline, largely on environmental grounds. More recently, the privatisation of the power industry has resulted in a move away from coal and oil generation towards combined cycle gas turbines (CCGT). The use of gas in power generation has increased by a factor of 29 since 1991. Further increases are expected as more CCGT stations come on line.

Table 2.3 UK Fuel Consumption

Fuel	Consumer	Units	1970	1980	1985	1990	1991	1992	1993	1994	1995	1996
Coal	Major Power Producers	kt	77216	89569	73940	82555	82021	76989	64096	60650	57943	53423
Coal	Industry	kt	21540	8503	7806	7856	8059	8140	7358	6726	6146	5117
Coal	Domestic	kt	20142	8946	8636	4239	4778	4156	4639	3901	2690	2706
Coal	Others	kt	37888	16419	15005	13607	12656	11295	10634	10506	10169	10157
Other Solid Fuels	All Consumers	kt	25795	9793	11272	10298	9806	9416	9216	9019	8822	9534
Motor Spirit	Road Transport	kt	14235	19145	20403	24312	24021	24044	23766	22843	21953	22409
Gas Oil	Road Transport	kt	5035	5854	7106	10652	10694	11132	11806	12914	13457	14365
Gas Oil	Industry	kt	5059	4706	3452	2970	2901	2856	2918	2933	2846	3041
Gas Oil	Others	kt	7746	7842	7456	6216	6325	6256	6024	5773	5509	5820
Fuel Oil	Major Power Producers	kt	11903	6336	9509	6358	5542	4152	3272	2337	2225	2217
Fuel Oil	Refineries	kt	3533	3526	2188	2020	2217	2263	2356	2448	2318	2300
Fuel Oil	Industry	kt	20888	10594	4683	4402	4866	4833	4783	4356	3275	2699
Fuel Oil	Others	kt	7514	3882	2721	2479	2413	2517	2622	2470	2553	2528
Orimulsion	Major Power Producers	kt	0	0	0	155	418	1286	1416	1227	1276	872
Burning Oil	Domestic	kt	2018	1699	1403	1567	1825	1914	2037	2058	2101	2551
Burning Oil	Others	kt	4033	498	533	484	554	558	587	597	673	780
Aviation Turbine Fuel	Air Transport	kt	3481	4728	5036	6615	6200	6693	7133	7313	7689	8081
Petroleum Gases	Refineries	GWh	29336	31622	36253	42988	42460	42056	44863	46206	47897	49591
Petroleum Gases	Others	GWh	20515	18317	15650	15134	17655	15840	16333	17731	17754	19410
Other Petroleum Prod.	All Consumers	kt	672	1076	955	1023	1116	1122	1153	1022	1179	1172
Natural Gas	Major Power Producers	GWh	1758	1612	3693	88	202	11600	72901	105670	133066	176704
Natural Gas	Industry	GWh	20808	193896	200783	205602	200738	192685	198257	221741	232128	256472
Natural Gas	Domestic	GWh	18376	246766	283517	300398	333954	330115	340168	329705	326012	375834
Natural Gas	Others	GWh	64651	64124	83672	88546	104580	105470	105185	106797	116962	128944
Other Gases	All Consumers	GWh	205413	33000	36810	39781	38105	36026	35215	36214	36346	38328

Figure 2.3 Generating Mix (1980-1996) Million Tonnes Oil Equivalent.

The effect of these changes in the power sector are clearly reflected in the carbon dioxide emissions. Since 1970 there has been an increase in the electricity generated of around 42% but a large decrease in emissions of around 24%. More significantly, emissions have decreased by 20% between 1990 and 1996. This is due specifically to:

• The greater efficiency of the CCGT stations compared with conventional stations - around 50% as opposed to 34%.
  
• The calorific value of natural gas per unit mass carbon being higher than that of coal and oil (the inventory takes account of unrefined gas or sour gas used by some plant).
  
• The proportion of nuclear generated electricity increasing from 18% to 26%.
  

Figure 2.4 Average CO₂ Emissions ktonne/GWh Electricity Generated

The domestic use of coal (including anthracite) shows an overall decline between 1970 and 1996, falling by 85%; domestic use of smokeless solid fuels (including coke) has also fallen significantly by around 77%. This reflects a trend away from solid fuels towards alternatives such as electricity and gas in sectors. Over the same period the domestic use of gas has increased by over a factor of 3.6.

2.2.4 Industrial

The industrial emissions have fallen by 50% since 1970. The curve exhibits peaks in 1973, 1979, and 1988 which are due in part to the cold winters in these years but mainly to the various levels of economic activity. According to DTI (1997), industrial energy consumption has declined since 1970 by 40% reflecting the decline in a number of the energy intensive industries and improvements in energy efficiency. Over this period, there has also been a marked move away from coal and oil consumption to gas and to a lesser extent electricity.

2.2.5 Transport

Total emissions from the transport sector have steadily increased since 1970. Of these road transport emissions have risen by 94% and currently accounts for around 86% of the total transport emissions or 20% of the total UK's carbon dioxide emissions. Although emissions fell a little during 1974-75 reflecting the increase in motor fuel prices after the oil crisis. The steady increase in fuel use by most forms of transport reflects the increased demand for transport in the UK between 1970 and 1996. The increased use of private motor vehicles has resulted in a 57% increase in the consumption of petrol. However, petrol consumption has declined by 8% since 1990 which is a result of the increase in popularity of diesel cars. Increased use of goods vehicles is reflected in the increase in DERV consumption by a factor of 2.9 since 1970.

2.2.6 Agriculture/forests/land use change

The effect of changing land-use can result in either net emission or net absorption of CO₂ , particularly on a global scale. For example, forest clearing for agricultural use could be a net source of CO₂. Recently the Intergovernmental Panel on Climate Change agreed new guidelines for preparing national inventories (IPCC, 1997). Land use change and forestry estimates are included in the UK Greenhouse Gas Inventory (Salway, 1998) for the years 1990-96. The estimates have yet to be included in the NAEI which covers the longer period 1970-1996. For comparative purposes the land use change estimates of carbon emissions and removals are summarised in Table 2.4 (Milne, 1997). The new guidelines for Land Use Change and Forestry include emissions from liming of soils under 'D CO₂ Emissions and Removals from Soils'. These are already included in the NAEI under Agricultural Soils.

2.4 Emissions and Removals of Carbon Dioxide¹ from Land Use Change and Forestry in 1996 (ktonnes)

1. Reported as ktonnes carbon dioxide according to IPCC Guidelines; 1 ktonne CO₂ is equivalent to 0.27 ktonnes of carbon.
   
2. Includes agricultural land use change. Net emission reported.
   
3. Agricultural set-aside.
   
4. CO₂ emission arises from liming of soils. Agricultural soils could be a net sink of methane.
   
5. Emission of CO₂ is from wetland drainage and peat extraction. Removal arises from salt marshes.