Well-to-Tank

Zemo Partnership assesses the impact of vehicles on a Well-to-Wheel basis. The reason for this is to ensure that both tailpipe emissions and the emissions associated with generating a fuel or energy vector are fully captured to enable a fair comparison of all technologies and fuels. e.g. an electric bus has no tailpipe emissions, but there are emissions produced in the generation and transmission of that electricity and so we must include the well-to-tank emissions to truly understand the greenhouse gas impact of that electric bus.

A Well-to-Tank emissions factor, also known as upstream or indirect emissions, is an average of all the GHG emissions released into the atmosphere from the production, processing and delivery of a fuel or energy vector.

To ensure a fair comparison of all technologies, the Low Emission Bus and Ultra-Low Emission Bus Schemes use the UK national carbon conversion factors that are produced annually by the Department for Business, Energy and Industrial Strategy. These factors are published annually and emission factors will vary depending on the origin, production process and feedstocks of various energy vectors and fuels.

The only fuel not to have a UK average factor is hydrogen (as there is no hydrogen grid) and so each operation will be assessed independently on a case by case basis. Hydrogen must be produced from renewable sources in order to have a strong case to reduce greenhouse gas emissions from transport operations.

Zemo Partnership will publish the latest factors below as well as list the factors used on each LEB/ULEB certificate to ensure transparency and consistency. We will also aim to use these emission factors across all projects to enable fair comparison of greenhous gas performance of different vehicle types.

This page was last updated on 10th November 2022.

2022 Well-to-Tank Conversion Factors

1. Figure has been sourced from DBEIS 'Government emission conversion factors for company greenhouse gas reporting' - conversion factors for 2022. Available here. 
2. Range sourced from JEC “Well-to-Tank Appendix 4 – Version 4a: Description, results and input data per pathway” from “Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context” (2014). Available here.

The UK Grid Electricity factor for 2021 is broken down in the table below:

2021 Well-to-Tank Conversion Factors

1. Figure has been sourced from DBEIS 'Government emission conversion factors for company greenhouse gas reporting' - conversion factors for 2021. Available here. 
2. Figure has been sourced from the Renewable Fuel Statistics 2020: Fourth Provisional Report. Available here. 
3. Range sourced from JEC “Well-to-Tank Appendix 4 – Version 4a: Description, results and input data per pathway” from “Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context” (2014). Available here.

The UK Grid Electricity factor for 2021 is broken down in the table below:

2020 Well-to-Tank Conversion Factors

1. Figure has been sourced from DBEIS 'Government emission conversion factors for company greenhouse gas reporting' - conversion factors for 2020. Available here.
2. Figure has been sourced from the Renewable Fuel Statistics 2019: Fifth Provisional Report. Available here.
3. Range sourced from JEC “Well-to-Tank Appendix 4 – Version 4a: Description, results and input data per pathway” from “Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context” (2014). Available here.

The UK Grid Electricity factor for 2020 is broken down in the table below:

2019 Well-to-Tank Conversion Factors

1. Figure has been sourced from DBEIS 'Government emission conversion factors for company greenhouse gas reporting' - conversion factors for 2019.
2. Figure has been sourced from the RTFO 2017/18 Year 10 - report 6. 
3. Range sourced from JEC “Well-to-Tank Appendix 4 – Version 4a: Description, results and input data per pathway” from “Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context” (2014). 

The UK Grid Electricity factor for 2019 is broken down in the table below:

2018 Well-to-Tank Conversion Factors

1. Figure has been sourced from DBEIS 'Government emission conversion factors for company greenhouse gas reporting' - conversion factors for 2018 energy (for energy supply 2016/17). 
2. Figure has been sourced from the RTFO 2016/17 Year 9 - report 6.
3. Range sourced from JEC “Well-to-Tank Appendix 4 – Version 4a: Description, results and input data per pathway” from “Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context” (2014).

The UK Grid Electricity factor for 2018 is broken down in the table below:

2017 Conversion Factors

1. Figure has been sourced from DBEIS 'Government emission conversion factors for company greenhouse gas reporting' - conversion factors for 2017 energy (for energy supply 2015/16).
2. Figure has been sourced from the RTFO 2015/16 Year 8 - report 6. 
3. Range sourced from JEC “Well-to-Tank Appendix 4 – Version 4a: Description, results and input data per pathway” from “Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context” (2014).

The UK Grid Electricity factor for 2017 is broken down in the table below:

2016 Conversion Factors

Bus Operators intending to use compressed hydrogen should contact their fuel provider to determine the pathway used in producing and distributing the fuel to determine the appropriate WTT GHG emission factor. The ranges provided in the above table are indicative figures.

1. Figure has been sourced from DECC's UK greenhouse gas inventory - conversion factors for 2014/15 energy. 

The UK Grid Electricity factor for 2016 is explained in the table below:

2 Figure has been sourced from the RTFO 2014/15 Year 7-report 6. 

3 Range sourced from JEC “Well-to-Tank Appendix 4 – Version 4a: Description, results and input data per pathway” from “Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context” (2014). 

*Liquefied Biomethane is produced by capturing biogas released from organic municipal waste disposed at landfill. Compressed Biomethane Gas is produced from biogenic waste e.g. animal slurry, using anaerobic digestion.