By Pete Brownsort, SCCS Scientific Research Officer
Our mission in Scottish Carbon Capture & Storage (SCCS) is to enable carbon dioxide (CO₂) emissions reduction through carbon capture and storage (CCS), to help address the challenges of climate change. Among lots of other things, this means we need to know where CO₂ is emitted, particularly in our own patch.
Industry emissions in Scotland
Each year since I joined SCCS I have done some simple analysis of the CO₂ emissions in Scotland that are relevant for CO₂ capture, that is, the larger fixed sources such as industry and power stations. I use the data compiled by Scottish Environment Protection Agency (SEPA) in their database, the Scottish Pollutant Release Inventory (SPRI), which lists CO₂ emissions of greater than 10,000 tonnes/year (t/yr) from sites ranging from hospitals to oil refineries, cheese factories to super quarries, sewage treatment works to power stations. The analysis of 2014 data was used in a 2016 journal publication (summarised here), which gives more background and detail of the methodology.
The data for one year is usually published late the following year. The 2017 data was even later, released in early January 2019, and it’s taken me a while to find time for the analysis, but here we are now. This blog gives a summary of the main observations.
Having now looked at this data over seven years, 2011 to 2017, I have a good picture of how the emissions and their sources have varied over recent years. The headlines when the 2017 data was released were positive: “Greenhouse gases from Scottish industry at 10-year low”, said the BBC. Total reported CO₂ emissions were 11.3 Mt in 2017, down by 1 Mt or 8.1% from 2016. But, as is often the case, a good news headline can hide detail that gives a less rosy picture, as I’ll explain.
There are two basic factors that lead to variation in the total CO₂ emissions from year to year, either the number of emitters can change or individual site emissions can change. We can distinguish the two factors but, in most cases, not the reasons for the changes at the level of analysis I’m making.
For the first factor, emitting sites may close or they may have emissions in one year that are below the reporting threshold. When large sites, such as power stations, have closed, we usually know about these and can see the effect it has on the total, as explained further below. When smaller sites drop out of the record, it may not be clear if this is just because emissions have fallen below the threshold or if a plant has closed; some sites come and go from the record over a number of years.
For the second factor, when an ongoing site’s emissions change, this may either be because the company has taken measures to improve process or energy efficiency, or because its activity level has changed. Sometimes we know which, but more often it is difficult to tell.
Chart 1 shows the total CO₂ emissions reported in the SPRI in the years 2011 to 2017 and the number of emitters contributing. These are sites with emissions above the reporting threshold of 10,000 t/yr. It is clear there is a relationship between the number of emitters and the total emissions - not surprising, but potentially a concern if our emissions are only falling due to closure of plant. But it is not just a simple effect.
Breaking the total emission figures down into industry sectors gives some more insight, as shown in Chart 2. This shows, in the lowest blue sector of the columns, that the sector with the greatest change over the period is electricity generation.
Most of this change is due to closure of two coal-burning power stations. Cockenzie emitted 2 Mt in 2012 but closed early in 2013. Longannet emitted 9.5 Mt in 2013 but then wound down, with the advance of renewable generation, before closing at the end of March 2016, still emitting 1.6 Mt that year. This is a success story at one level – that of reducing overall emissions – but it hides the fact that the emissions from the other industry sectors have barely changed, despite 24 other sites no longer reporting to the SPRI.
The remaining emissions from electricity generation, 2.1 Mt in 2017, are from one major gas-fuelled power station, a handful of large biomass-fuelled power stations and some smaller facilities. The emissions from the biomass burners are largely carbon neutral, but they still amount to 1 Mt of CO₂ in 2017, which it would be better if not emitted.
Underlying trend – a concern
If I strip the emissions from electricity generation out of the picture we can see, in Chart 3, that combined emissions from the other sectors haven’t changed much over the period. They fell from 2011 to 2015, but increased over the last couple of years, despite a fall in the number of sites reporting.
As mentioned above, I can’t distinguish any trend in industry activity from this data, but it appears unlikely that industrial efficiency, in terms of CO₂ emissions, has improved much over this period, which is a matter of some concern, but possibly not surprise.
Changes by site and sector
Given this continuing slight upward trend in CO₂ emissions when the effect of major power station closures is excluded, this year I have taken a look at the emission changes at site level, for sites that have reported in both 2016 and 2017. This analysis includes the ongoing electricity generators that emit CO₂, but excludes the closed Longannet plant.
Seventy-six sites reported in both years, with a combined CO₂ emission from these sites rising from 10.6 Mt in 2016 to 11.3 Mt in 2017, an increase of 5.9%. Of these sites, more than half, 46, reported increased emissions, with 27 decreased (three sites had exactly the same emissions).
Of the 46 sites with increased emissions, 35 reported increases of 3% or over, of which 24 increased more than 10% and six more than 30%. Conversely, of the 27 sites with decreased emissions, 18 reduced by 3%, of which 5 reduced more than 10% and 2 more than 30%.
I’m not going to name names here (although the data is public in the SPRI) but Table 1 gives a general idea of the sectors that have increased or decreased CO₂ emissions by more than 3% between 2016 and 2017, listed roughly in decreasing order of relative change (i.e. larger changes at top of columns).
With a few exceptions, it seems most likely that these changes resulted from changes in industry activity levels, rather than from changes in efficiency. For example, the largest absolute emission reductions were recorded by facilities associated with the Forties Pipeline System, which was offline for about a month in late 2017. Similarly, the largest absolute increase in emissions was at Peterhead power station, and the biomass power stations also reported large increases in emissions, presumably filling some of the gap in generating capacity left by the closure of Longannet.
More effort required
All of this emphasises the need for a continuing focus on reducing CO₂ emissions from industry in Scotland by all means possible, but without affecting the extent and viability of our industry and the benefit it brings to society and the economy. In past days, perhaps even before I were a lad, “more smoke up the chimney” was seen as a sign of economic prosperity, but this sign gives a mixed message today. We now need to develop the technologies we already know of – improving efficiency where possible, switching to low-carbon fuels, and capture and permanent storage of CO₂ – to sustain our industry and the jobs it provides, without the climate-damaging emissions it currently still causes.
|Pete Brownsort, left, with SCCS Team|