Five years since the concept of unburnable carbon – those fossil fuel reserves that may not be used if we are to reduce carbon dioxide emissions into the atmosphere – was first articulated, countries across the world are still struggling to meet global climate targets. In order to limit the rise in global average temperatures to within 2 degrees of pre-industrial levels, decisive action is urgently needed, and that will certainly mean further efforts to decarbonise economies everywhere.
Carbon capture and storage technology has been acknowledged as one way to allow more reserves to be combusted within a low-carbon framework, but with few examples existing in practice, its potential and limitations are still uncertain.
In a May 2016 white paper, Dr Sara Budinis and colleagues from the Sustainable Gas Institute (SGI) at Imperial College London ask ‘Can technology unlock unburnable carbon?’ and look further into the barriers to widespread adoption of CCS. Adjacent Oil & Gas caught up with Dr Budinis shortly after the research launch to discuss the paper’s findings.
The term started to be widely used in 2011 following its adoption by the Carbon Tracker Initiative in their first report on this topic. Due to the nature of the Initiative, their approach had more to do with the financial aspects; for example, they very strongly linked the idea of unburnable carbon with the idea of a carbon bubble.
So, while the idea originally came from a financial perspective, the concept has now been more widely adopted by those people who are concerned about the environmental aspects of this issue and how we can meet future global energy demands without relying on fossil fuels.
The primary aim was to understand how technology – more specifically, carbon capture and storage – could potentially unlock unburnable carbon by granting access to fossil fuel reserves while still enabling us to meet climate targets. We knew there was an emerging literature looking at ways to decarbonise the energy sector, but different papers were reporting different numbers and it was not easy to give a decisive answer to this question.
Of course, as you work you learn more about the topic. We realised that there was very little agreement on the issue and decided a systematic review was needed.
There are quite a few publications – academic papers from conferences and scientific journals, governmental reports, and grey literature from industry and other institutions – but very few were looking specifically at this question. Many more were looking at the uncertainty around the estimation of global fossil fuel reserves, or the estimation of carbon budgets, for example.
There was only one other research paper – by Christophe McGlade and Professor Paul Ekins at UCL, published in Nature – which was specifically covering unburnable carbon and CCS. It was not the main topic of the paper, but they did look at the role of CCS up to 2050.
Other publications had not been subjected to external review; McGlade and Ekins was the most reliable source we found. The authors analysed energy scenarios up to 2050 and found that with access to CCS, you can utilise 5.5% more global reserves than without access to CCS.
Starting from that point, we decided to go beyond 2050 and look at the full century. We divided our analysis into what might happen up to 2050, to see if our findings agreed with those reported by UCL, and we looked at 2050 up to 2100.
What we found up to 2050 – what we can compare to what is reported by McGlade and Ekins – is that with CCS you can access 11% more fossil fuel reserves than without. A doubling of the figure might seem like a lot, but given we have used a different model and different assumptions there is a lot of uncertainty. We consider the 5.5% and 11% figures essentially in agreement.
At the Sustainable Gas Institute we are building our own model: MUSE. It is still in the early stages of development, so we were unable to use it for our analysis. Instead we used the database from the IPCC’s Fifth Assessment Report, and specifically we focused on the EMF27 projects. This project includes 18 integrated assessment models that have scenarios in common, so it is easier to compare results between models and scenarios. We excluded those that did not model beyond 2050.
We carried out an analysis of potential barriers to CCS. We have been talking about CCS for quite a while now, but it’s not really happening yet. One of the important findings is that there are no purely technical barriers to CCS. It is more to do with policy, regulation, markets, agreement amongst countries, and public acceptance.
Another large section of the white paper covers the cost of CCS. If you do CCS, your power processing plant will be more expensive because you have to build an extra piece of equipment and run it. According to our analysis, cost will not be a barrier in the long term; CCS is still the cheapest way to decarbonise the energy system.
We also report on how the capture rate can affect the outcome of the analysis. The capture rate is a percentage that represents how much carbon dioxide you can store. For example if you have a capture rate of 90% it means you can capture 90% of carbon dioxide and the rest has to be released into the atmosphere. This is a very important parameter because it heavily affects the performance of the plant. In an ideal world, the capture rate would be 100%, but we don’t live in an ideal world. We suggest this is an engineering challenge which we would like to investigate further.
In the long term, cost won’t be a limiting factor, but there is an economy of scale. Some CCS plants are currently running, but very few – only around 15 largescale plants. Over time, technology becomes cheaper and the cost goes down according to a learning curve. The more you know about the technology, the more you can refine it and lower the cost, but if you never start doing that the price will never go down.
Looking at potential barriers to CCS, some people ask: Do we have enough space to store all this carbon dioxide underground? The answer is: Yes, there is more space than we need. In our projections for further research, we say that each country that would like to do CCS should conduct evaluation and assessment of its carbon storage capacity. Worldwide, there is enough storage capacity, but each country needs to understand its own geology and identify suitable storage sites.
From our perspective, we would like to investigate further how capture rate affects CCS and the numbers we reported. In terms of what governments or policy makers should do, I would say it’s very difficult to evaluate the potential of CCS or how costs could decrease without actually doing it.
Most analyses of the cost of CCS compare it to other technologies that have been developing over the last decade – there is simply not enough data on CCS because very few people are using it.
For the oil and gas industry, it means there is definite potential to keep using fossil fuel reserves without endangering climate change targets, so if they were to end up in this carbon bubble that was described in 2011, they should really think about investing in CCS.
For the CCS industry, the challenge is to improve the capture rate and possibly reduce the cost, but, as I said, costs are estimations not solid numbers and will tend to go down. ■
Dr Sara Budinis
From Adjacent Oil & Gas 4, August 2016