Assess the impact of air emissions on global warming
How to work out the impact of air emissions on global warming if you're applying for a bespoke environmental permit.
Applies to England
You must read this guide if you’re applying for a bespoke environmental permit and your activity produces air emissions.
Read the risk assessment overview first. It explains the other steps you need to take in completing your risk assessment.
Work through the following steps to calculate your impact on global warming.
- Identify your greenhouse gas emissions.
- Work out the impact these emissions have on global warming.
- Work out the impact of your ‘process option’ on global warming.
- Add up the impacts from steps 2 and 3 for each of your current or proposed process options to give the total impact on global warming.
A process option is a production process you aim to follow (eg making iron in a blast furnace) and the method you take to prevent or minimise emissions from it.
Knowing the impact of emissions on global warming will help you:
- choose a process option (if you can choose from more than one) that has the least impact on global warming
- establish the best available techniques to control emissions
Risk assessment tool
You can use the risk assessment tool to help complete this part of your permit application. It can do the calculations in this guide for you.
Identify greenhouse gas emissions
Identify all greenhouse gases your site produces.
You must list each of your:
- direct emissions - you’ll already have identified these in your air emissions risk assessment
- indirect emissions
Direct emissions
Direct emissions are produced by the energy your activity uses from storing, handling and processing at your site. They include any heat or power you produce directly at your site.
Direct emissions aren’t limited only to energy use - they can arise from any manufacturing process in which a substance releases a greenhouse gas.
Indirect emissions
Indirect emissions are produced from the heat or power imported into your site (eg electricity you buy from a supplier).
Indirect emissions also include energy used away from your site by others (eg when your site’s waste is treated elsewhere).
Treat any direct or indirect carbon dioxide emissions that come from renewable energy sources (eg from waste or from ‘biomass’ - biodegraded waste) as having an impact of ‘0’ on global warming.
Calculate impact of emissions on global warming
- Do this calculation: annual tonnes produced of the released greenhouse gas, multiplied by the appropriate global warming potential factor. The result should be shown in annual tonnes produced.
- Repeat this calculation for all substances released.
- Add up the totals to get the total impact of your emissions for your site.
Greenhouse gases: impact of your emissions
| Substance | Global warming potential factor |
|---|---|
| Carbon dioxide | 1 |
| Carbon tetrachloride | 1400 |
| Chloroform | 4 |
| CFC-11 | 4000 |
| CFC-12 | 85000 |
| CFC-13 | 11700 |
| CFC-113 | 5000 |
| CFC-114 | 9300 |
| CFC-115 | 9300 |
| H-1301 | 5600 |
| HCFFC-22 | 1700 |
| HCFC-123 | 93 |
| HCFC-124 | 480 |
| HCFC-141b | 630 |
| HCFC-142b | 2000 |
| HCFC-225ca | 170 |
| HCFC-225cb | 530 |
| HFC-23 | 12000 |
| HFC-32 | 550 |
| HFC-41 | 97 |
| HFC-43-10mee | 1500 |
| HFC-125 | 3400 |
| HFC-134 | 1100 |
| HFC-134a | 1300 |
| HFC-152a | 120 |
| HFC-143 | 330 |
| HFC-143a | 4300 |
| HFC-227ea | 3500 |
| HFC-236fa | 6300 |
| HFC-245ca | 640 |
| Methane | 21 |
| Methylene chloride | 9 |
| Methyl chloroform | 110 |
| Nitrous oxide | 310 |
| Perfluorocyclobutane | 10000 |
| Perfluoroethane | 11900 |
| Perfluorohexane | 9000 |
| Perfluoromethane | 5700 |
| Perfluoropentane | 8900 |
| Sulphur hexafluoride | 23900 |
Global warming impact of energy used by your process option
You must work out the impact on global warming from the energy used by your process option, or (if you can choose from more than one) each process option.
The risk assessment tool will do these calculations for you. If you’re not using the tool, you must complete the following steps.
Direct and indirect carbon dioxide emissions
For each type of energy (eg electricity) used in an option list separately in annual kg its:
- direct carbon dioxide emissions
- indirect carbon dioxide emissions
Calculate carbon dioxide emissions by multiplying the amount of energy you use in annual kg by the relevant multiplier (also known as ‘conversion factor’) for carbon dioxide.
Calculate annual tonnes of carbon dioxide produced
Different conversion factors apply depending on how you measure the energy you use (ie megawatt hours or gigajoules).
| Fuel | Conversion factor: tonnes per megawatt hour | Conversion factor: tonnes per gigajoule |
|---|---|---|
| Electricity | 0.166 | 0.0462 |
| Coal | 0.3 | 0.0832 |
| Coke | 0.43 | 0.1192 |
| Gas oil | 0.25 | 0.0693 |
| Heavy fuel oil | 0.26 | 0.0722 |
| Petrol | 0.24 | 0.0667 |
| Liquid petroleum gas (LPG) | 0.23 | 0.0638 |
| Jet kerosene | 0.24 | 0.0667 |
| Ethane | 0.2 | 0.0557 |
| Naphtha | 0.26 | 0.0722 |
| Refinery gas | 0.2 | 0.0191 |
| Petroleum coke | 0.34 | 0.0946 |
| Natural gas | 0.19 | 0.0528 |
Treat any heat and power from a direct or indirect renewable source as having ‘0’ carbon dioxide impact.
Energy efficiency conversion factor: indirect emissions
You must use 2 additional conversion factors if you use any of the following indirect energy sources.
| Energy source | Conversion factor 1 | Conversion factor 2 |
|---|---|---|
| Electricity from National Grid | 2.4 | 0.166 |
| Electricity from other suppliers | Ask your supplier | Ask your supplier |
Where you’re told to ‘ask your supplier’, ask them for either:
- the ‘delivered to primary conversion factor’, for conversion factor 1
- the ‘primary carbon dioxide factor’ in tonnes per megawatt hour, for conversion factor 2
Energy efficiency conversion factor: direct emissions
You must use additional conversion factors if you use any of the following direct energy sources.
| Energy source | Conversion factor 1 | Conversion factor 2 |
|---|---|---|
| Coal | 1 | 0.3 |
| Coke | 1 | 0.43 |
| Gas oil | 1 | 0.25 |
| Heavy fuel oil | 1 | 0.26 |
| Petrol | 1 | 0.24 |
| Liquid petroleum gas (LPG) | 1 | 0.23 |
| Jet kerosene | 1 | 0.24 |
| Ethane | 1 | 0.24 |
| Naphtha | 1 | 0.2 |
| Refinery gas | 1 | 0.2 |
| Petroleum coke | 1 | 0.34 |
| Natural gas | 1 | 0.19 |
| Other sources | 1 | Ask your supplier for the primary carbon dioxide factor in tonnes per megawatt hour |
Conversion factor: tonnes to kg
Because you must show the total carbon dioxide impact in annual kg produced, you need to use an additional conversion factor of 1000. (This is because other conversion factors in this guide have been calculated based on tonnes rather than kg.)
Calculate your total impact on global warming
Add up:
- the impact of emissions on global warming
- the impact each option has on global warming
The result is the the total impact (kg of carbon dioxide) on global warming produced from your site’s activities.
Rank global warming impact of different options
If there’s more than one process option you can use, you must include the impact for each option in your assessment.
Rank these options to show which has the least impact on global warming and which has the most.
Example:
- 1: Option 2 - 2,821,750 annual kg of carbon dioxide
- 2: Option 1 - 3,131,600 annual kg of carbon dioxide
- 3: Option 3 - 3,539,600 annual kg of carbon dioxide
Check if you need to complete further risk assessments
Check if you need to complete more assessments as part of your permit application.
Submit the data you’ve calculated in this guide with your permit application.