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ENVIRONMENT REPORT
2016
Trend Data
Figure 8 shows that in general there has been a steady decline in CO
2
, CO, NO
x
and SO
2
emissions from UK offshore
oil and gas installations since 2000. The decline in production over the long term has been influential in reducing
emissions, as has been lower emissions fromnew fields that have come on-streamusing more efficient technology.
Emissions of CO
2
, CO, NO
x
and SO
2
have, however, increased in 2015 by 5 per cent to 13.3 million tonnes combined,
reflecting the growth in production last year. Nevertheless, emission levels are still well below what they were
prior to 2013 and so there continues to be a downward trend over the longer term.
Seventy-five per cent of CO
2
emissions in 2015 were generated from fuel consumed by combustion equipment to
provide electrical power and drive compressors for gas export. This activity is essential as offshore installations
are not connected to the national grid for power supply. Power is required to run oil pumps, equipment used in
production processes, for electricity and heat (cooking, lighting and heating on offshore installations), as well as
for compression equipment so that gas can be transported ashore. CO
2
is also emitted during flaring and venting
offshore, which are necessary for maintenance, well testing and, crucially, for the safety of offshore workers.
CO emissions have declined by 29 per cent since 2000. It is important to note that, as of 2015, the factor used to
calculate CO values from fuel consumed has been amended in EEMS and the resulting value is shown as a dotted
line in Figure 8. Therefore, the 2015 figure is not comparable with previous years and does not represent an actual
increase in the mass of CO emitted in 2015.
NO
x
emissions, on the other hand, follow a general downward trend but have been more variable over the
timeframe. This could be due to the varying use of diesel for fuel when reservoir gas supply is unavailable such as
during drilling activity, when new installations are being brought online, maintenance turnarounds, turbine ‘trips’
or disruption to the gas supply. Last year, just over 48,300 tonnes of NO
x
were released offshore.
There is a trade-off between CO and NO
x
emissions in turbines as they occur at different combustion temperatures,
with CO emissions decreasing with rising temperatures and NO
x
emissions increasing with rising temperatures.