What's been driving GHG emissions cuts in the UK? Gas, renewables or both and more?
Total UK GHG (Greenhouse Gas) emissions have fallen from 799.0 MtCOeq (Million tonnes of CO2 equivalent) in 1990 to 495.7 MtCO2eq in 2015 - a drop of 38%
With the exception of Hydrofluorocarbons (which rose from a 1990 level of 14.4 MtCO2eq to 15.8 MtCO2eq and probably reflects their greater use as a replacement for banned Chlorofluorocarbons in refrigerant gases) GHG emissions have fallen steadily across the range of 7 gases that are measured and reported by the Government.
Net CO2 emissions in particular have fallen from 595.7 MtCO2eq in 1990 to 403.8 MtCO2eq in 2015. That's a 32.2% reduction.
Methane levels have dropped more drastically by around 60% from 135.6 MtCO2eq in 1990 to 52.2 MtCO2eq. Nitrous Oxide emissions reduced from 51.2 MyCO2eq to 23.1 MtCO2eq - a drop of around 55%.
In this 25 year window, we've seen a switch from petrol to diesel vehicles and big changes in the fuel mix used in electricity generation.
Curiously, the switch from petrol to diesel cars has been blamed for an air quality epidemic linked to the higher levels of Nitrous Oxide emitted in diesel exhaust fumes, but that isn't borne out by the numbers - which suggests that something else significant changed and produced a reduction in NOx levels that offset any gain in road transport emissions. Between 1990 and 1998 inclusive, yearly NOx emissions averaged 44.99 MtCO2eq but from 1999 to 2015, they averaged just 25.73 MtCO2eq.
CO2 emissions were relatively static until they dipped below 500 MtCO2eq a year in 2009, after which they've continued to fall (with the exception of brief "blips" when they rose in 2010 and 2012).
So, what might have driven these emissions cuts?
The immediate assumption will be that it's the growth we've seen in renewables, but there's more to it than that.
For example, in 2009, Anglesey Aluminium closed - prior to that, it was a huge electricity consumer in the production of 145,000 tonnes a year of aluminium. The closure of the 178,000 tonne capacity Lynemouth aluminium plant followed in 2012. This drop in electricity demand will have helped cut CO2 emissions, as will other factory closures in the energy-intensive manufacturing sectors. In 1990, industrial electricity consumption was 100.64 TWh (Terrawatt Hours) by 2015 it had fallen to 93.32 TWh, having begun to decline year-on-year in 2012.
Then there's the decline in landfill disposal of putrescible waste in favour of anaerobic digestion and Mechanical Biological Treatment, plus more harvesting of landfill gas to generate power - which will have undoubtedly helped reduce methane emissions along with the closure of more of our coal mines.
But the biggest change, affecting both CO2 and NOx emissions, will be the increased use of gas in electricity generation alongside the growth in renewables that's occurred, at the expense of dirtier coal and oil.
In 1990, the electricity generating fuel mix looked like this in MtOE (Million tonnes of Oil Equivalent):
Wind and solar 0.0
By 1999, coal had slumped to 25.51 MtOE, and oil to 1.54 MtOE. Gas, on the other hand, had leapt to 27.13 MtOE. Wind and solar only put in an appearance in 1996 at just 0.04 MtOE and didn't get above 1.0 MtOE until 2010. Hydro has remained very static throughout.
At the end of 2015:
Wind and solar 4.12
What this tells us is that the reductions in UK GHG emissions, particularly CO2 and NOx have resulted from a combination of:
- reduced industrial electricity demand
- replacement of coal and oil with gas
- cleaner waste handling techniques
But wind and solar renewables? It doesn't really seem as though they've contributed all that much so far. As in the US, it seems that it's coal-to-gas switching that's had the biggest impact.
Advocates of climate action everywhere should be continuing to push for coal to be fully retired as quickly as possible, and replaced with cleaner burning gas, nuclear and renewables. Part of this drive should also be to produce our onshore shale gas resources rather than importing higher emission Liquefied Natural Gas (LNG) in ships from Qatar in order to obtain a further 10% CO2eq saving.