As described in Information Sheet 3 you can choose between energy based targets or CO2 based targets. One of the advantages of CO2 based targets is that it gives you additional flexibility. This is because different fuels have different carbon contents and by switching to one with a lower carbon content you will contribute towards a CO2 based target without changing the energy intensity of your process.
For example, by simply substituting electrical heating with gas you would reduce carbon dioxide emissions by around 50% per unit of energy used. Similarly, conversion from heavy fuel oil to gas reduces CO2 emissions by about 25% per unit of energy. Another example is replacing electrical power from the grid with electricity sourced from renewables. Renewable power could either be provided through the grid or via local generation. In this case using renewables would provide two benefits: a) a 100% reduction in CO2 emissions in proportion to the amount of renewable energy used, and b) a reduction in the amount of Levy paid, again in proportion to the amount of renewable energy used.
Calculating CO2 Emissions
When any fuel is burnt, energy is produced and carbon dioxide (CO2) and other chemicals, mostly water, are produced. The ratio of energy produced to CO2 differs according to the type of fuel used. Table 12.1 shows the carbon emission factor of different fuels, expressed as kg Carbon/kWh.
Table 12.1 Carbon Intensity of Different Fuels
|
Type of fuel |
kgC/kWh primary |
|
Electricity (from grid) |
0.0453 |
|
Natural Gas |
0.0518 |
|
Gas Oil / Diesel Oil |
0.0680 |
|
Heavy Fuel Oil |
0.0709 |
|
Coal |
0.0817 |
|
Liquid Petroleum Gas |
0.0627 |
|
"New Renewables" |
0 |
It may be seen for example that the carbon emissions per unit of energy from burning natural gas are much less than those from the high carbon-content fuels such as coal and oil.
Electricity is generated from a range of fuels including nuclear, gas, oil and coal. The figure in for "grid" electricity in Table 12.1 reflects the current mix of fuel sources used in UK electricity generation. The carbon figure stated is per kWh of primary energy – for electricity primary energy is 2.6 times the delivered energy. Some power is generated from "new" renewable sources such as wind or landfill gas. New renewables have a zero CO2 emission.
To calculate the carbon dioxide emissions associated with your energy use, simply multiply your primary energy use by fuel type by the appropriate factor from Table 5.1. If you measure your energy used by weight or volume rather than directly in energy terms, then you should first convert your fuel use to energy units using the conversion factors shown in Table 12.2.
Table 12.2 Fuel Conversion Factors
|
Fuel |
Usual Units |
Conversion Factor |
Conversion Factor units |
|
Natural gas |
00 ft3 |
Depends on local conditions. See bill. |
|
|
Electricity |
kWh |
1.00 |
kWh/kWh |
|
Gas Oil |
litres |
10.6 |
kWh/litre |
|
Light Fuel Oil |
litres |
11.2 |
kWh/litre |
|
MediumFuel Oil |
litres |
11.3 |
kWh/litre |
|
Heavy Fuel Oil |
litres |
11.4 |
kWh/litre |
|
Propane |
kg |
13.89 |
kWh/kg |
|
Butane |
kg |
13.69 |
kWh/kg |
|
Dry steam coal |
tonnes |
8,500 |
kWh/tonne |
|
Anthracite |
tonnes |
8,236 |
kWh/tonne |
|
Coke |
tonnes |
7,750 |
kWh/tonne |
|
Nitrogen |
hcum |
kWh/hcum |
|
|
Carbon dioxide |
hcum |
kWh/hcum |
|
|
Steam |
kg |
Depends on conditions. Check with supplier. |
|
|
Hot water |
kg |
Depends on conditions. Check with supplier. |
|
|
Condensate |
kg |
Depends on conditions. |
|
The following table of unit conversions may be useful.
|
To convert |
Operation |
Constant |
|
|
From |
To |
||
|
ft3 |
m3 |
multiply by |
0.02832 |
|
therms |
kWh |
multiply by |
29.31 |
|
MJ |
kWh |
divide by |
3.6 |
|
Example: Lovely Lollies Ltd annually uses 1 million litres of heavy fuel oil in its boiler house. What are the annual carbon emissions associated with this oil use? By how much would the emissions be reduced by converting the boiler house to natural gas firing? Step 1. Refer to Table 12.2. The calorific value of heavy fuel oil is 11.4 kWh/litre. Therefore the energy used in Lovely Lollies’ boiler house is given by: 1,000,000 litres x 11.4 kWh/litre = 11,400,000 kWh. Step 2. Table 12.1 shows that 0.0709 kg of carbon are emitted per kWh of energy derived from heavy fuel oil. The annual carbon emissions associated with this energy use is: 11,400,000 kWh x 0.0709 kg/kWh = 808,260 kg of carbon. Step 3. Refer again to Table 12.1. The carbon emissions per kWh of energy from natural gas burning are 0.0518 kg/kWh. Hence if the same amount of energy were to be derived from natural gas rather than heavy fuel oil, the carbon emissions would be: 11,400,000 kWh x 0.0518 kg/kWh = 590,520 kg of carbon. Step 4. The emissions saving is (808 – 590) or 218 tonnes. This is 26.9% of current emissions from combustion of boiler fuel. Note that this calculation assumes unchanged combustion efficiency, which might not be the case in practice.
|
Renewable Energy
Energy derived from "new renewable" sources are defined, for the purposes of the Climate Change Levy and energy reporting to have zero carbon dioxide emissions. "New renewable" sources are listed below:
|
|
Renewable electricity is available from many electricity supply companies and can be bought in the same way as conventional electricity. Definitions regarding what is truly renewable are being developed, with a view to establishing a green accreditation scheme in time for the introduction of the Climate Change Levy in April 2001.