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, 42 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. There are no current plans to expand the Danish natural gas transmission grid, but Energinet.dk has nevertheless reserved the land which may be required for an expansion of transmission capacity. Land has been reserved for compressor stations at Egtved in Jutland, Langeskov on Funen and Avedøre on Zealand.
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 2008
In 2008, Energinet.dk transported 7.6bn Nm3 of natural gas (79 TWh) 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 2008 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.
Environmental impacts from transport of natural gas in 2008
|
Total transport of natural gas |
7.6 bn Nm3 |
|
Emissions of natural gas |
24,204 Nm3 |
|
Emissions of natural gas in per mille of transported volume |
0.004 per mille |
|
Emitted volumes of CO2 equivalent |
344 tonnes |
Energy consumption in connection with transport of natural gas
There are 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 42 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.
Environmental impacts from heating of natural gas in
Energinet.dk’s MR stations in 2008
|
Energy consumption (natural gas in boilers) |
37,286 MWh |
|
CO2 (carbon dioxide - greenhouse gas) |
7,622 tonnes |
|
CH4 (methane - greenhouse gas) |
2,013 kg |
|
N2O (dinitrogen oxide - greenhouse gas) |
134 kg |
|
Total greenhouse gases (CO2-equivalents) |
7,705 tonnes |
| CO (carbon monoxide) |
3,758 kg |
|
NMVOC (unburnt hydrocarbons) |
268 kg |
|
SO2 (sulphur dioxide) |
40 kg |
|
NOx (nitrogen oxides) |
5,638 kg |
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.
Environmental impacts from the use of odorant in Energinet.dk's transmission grid in 2008
| Volume of odorant consumed |
55,565 litres |
| SO2 (sulphur dioxide) |
40,373 kg |
Leaks
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 2008.