Greenhouse gas (GHG) emissions
It is necessary for us to release quantities of methane (which is a potent greenhouse gas) from the commissioning, operation, maintenance and decommissioning of the assets in the system. We are incentivised on the quantity of greenhouse gas emitted from our system compressors as these are currently the most significant venting source.
Each asset type on the NTS has different characteristics including the extent to which gas is inherently released, or periodically vented, as part of its operation or maintenance. Based on existing knowledge and data we believe that routine compressor venting accounts for 70% of the total NTS venting that is currently quantified. Research is in progress to better understand the quantity of venting from compressors and other assets on the NTS.
Greenhouse gas emissions incentive
The current Greenhouse Gas Emissions Incentive compares actual venting quantities against a defined volumetric allowance of 2,897 tonnes per year.
The current scheme is a downside only scheme, which means that there is no scope for National Grid to earn revenue from venting below the allowance but is currently penalised for any venting in excess of the allowance. The scheme value is based upon the Treasury's Green Book providing government analysts with rules for valuing energy usage and greenhouse gas emissions. You can view our performance on this incentive by downloading our Supporting Information document.
Pursuant to Special Condition 8D of our Licence, we have an obligation to investigate in more detail the sources and scale of the emissions caused by operating the gas transmission system. This includes venting from assets other than compressors. This obligation aims to increase the accuracy of emissions calculations for natural gas vented from a number of different vent types, including venting during the maintenance of pipelines.
We are also investigating alternatives to venting natural gas, which will identify the potential to reduce emissions from assets such as compressors and chromatographs taking into account the prevailing mandatory maintenance requirements.