For UK gas distribution networks, gas venting remains a necessary part of normal operations, for maintenance and safety purposes which can be either manual or automatic. Gas venting results in unburned natural gas being released into atmosphere. This has an environmental impact as the main constituent of natural gas, methane, has approximately 28 times the global warming potential of carbon dioxide (based on the IPCC Fifth Assessment Report (AR5) over a 100-year period).

Depending on the source of venting, varying quantities of gas will be released and there is limited understanding of the environmental impact this causes. Additionally, vented gas results in shrinkage, defined as the volume of gas that is lost from the network which cannot be accounted for. GDNs have an obligation under Special Condition 1F.14 to improve the Shrinkage and Leakage Model (SLM) by improving the accuracy and calculation of Shrinkage Gas reporting.

Currently, there are varying methods to different degrees of sophistication, to quantify and forecast the extent and impact of venting.

Objectives

Following the 3 stage approach to the project, the objectives of each stage are:

Stage 1 objectives

Identify and detail current venting processes and equipment which release gas. Include literature review of previous projects and identify the lessons learnt.
Provide an assessment of the frequency at which gas is released (considering variation through periods of high and low demand).
Provide a detailed understanding of the volume of gas being vented annually from equipment and operations.
Provide an assessment of the environmental impact of current venting processes.

Stage 2 objective
Identify safe, environmentally friendly alternative processes and technologies that could be adopted by the networks.

Stage 3 objective
Quantify the benefits associated with the options identified and highlight the most appropriate.