Natural gas transmission grid
The transport system for natural gas in Denmark consists of gas pipelines in the Danish part of the North Sea, transmission pipelines going north-south and east-west, the net distribution pipelines towards the consumers, two subterranean natural gas storage facilities and a natural gas treatment plant. The Transmission grid owned by Energinet.dk consists in total of 860 km pipelines, 43 M/R (meter and regulator) stations and four metering stations. In addition, Energinet.dk owns the gas storage facility at Lille Thorup whereas Dong Energy owns the gas storage facility at Stenlille.
Impacts on the landscape
The natural gas transmission grid consists of underground steel pipes and M/R stations above ground that blend in with the landscape and are surrounded with hedgerows. The impacts on the landscape are therefore moderate. Energinet.dk is currently buliding a compressor station in Egtved.
Environmental impacts from the transport of natural gas
The most important environmental impacts from the gas transmission grid are the direct emission of natural gas from the grid, especially during operation and maintenance, the use of natural gas at M/R stations, and the addition of odorant as required by Danish Law.
Transport of natural gas in 2012
In 2012, Energinet.dk transported 5.36 bn Nm3 of natural gas in the main transmission grid. The transport of natural gas gives rise to minor atmospheric emissions of natural gas. Such emissions, also known as blow-off gas, are seen in connection with maintenance work, repairs and gas pipe metering and when special metering equipment is sent through the transmission grid.
The environmental impacts from emissions of natural gas in 2012 are shown below. Natural gas consists primarily of methane (CH4), which is a greenhouse gas that can be converted into CO2 equivalents using a factor 21.
|Total transport of natural gas
|Emissions of natural gas
|Emissions of natural gas in per mille of transported volume
Energy consumption in connection with transport of natural gas
There are currently no compressor stations in Energinet.dk's transmission grid as the compression at the natural gas fields in the North Sea and the two storage facilities owned by Dong (Lille Torup and Stenlille) is sufficient to transport the natural gas through the Danish transmission grid. Energinet.dk has M/R stations in its grid.
The natural gas pressure is reduced at the 43 M/R stations in Energinet.dk's transmission grid. In order to compensate for the accompanying drop in temperature, the natural gas is heated prior to pressure regulation. Natural gas is used as a fuel for the heating. The natural gas is burnt using high-efficiency burners in boilers. The environmental impacts of this heat production are shown in the table below.
|Energy consumption (natural gas in boilers)
|CO2 (carbon dioxide - greenhouse gas)
|CH4 (methane - greenhouse gas)
|N2O (dinitrogen oxide - greenhouse gas)
|Total greenhouse gases (CO2 -equivalents)
|CO (carbon monoxide)
|NMVOC (unburnt hydrocarbons)
|SO2 (sulphur dioxide)
Consumption of odorants
The natural gas from the Danish section of the North Sea is cleaned offshore of hydrogen sulphide down to max. 5 mg per Nm3, and the natural gas is almost odourless. In order to detect possible gas leaks, Energinet.dk adds an odorant to the natural gas when it is delivered to the distribution systems. The odorant is a hydrogen sulphide compound consisting of C4H8S and is burnt in connection with the end-use of the natural gas. The most significant environmental impact from the burning of the odorant is SO2, which contributes to the acidification of the environment.
|Volume of odorant consumed
Energinet.dk performs regular aerial inspections of the transmission grid with a view to observing any lack of growth in crops, which may be a sign of leaks. In densely built-up areas routine leak detection is carried out on foot using very sensitive gas measuring equipment. No leaks were detected in 2012.