Will technology be able to unlock ‘unburnable carbon’?

Sara Budinis's picture
Sara Budinis, Research Associate at the Sustainable Gas Institute, Imperial College London
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Last year, at COP21, an agreement by governments was reached on climate change with the aim of limiting global warming to below 2°C.  As of 2011, the world had a ‘carbon budget’ of 1,000 gigatonnes of carbon dioxide (the amount of CO2 left to emit in order to have a two-thirds or greater chance of staying below two degrees). However, at the current yearly emission rate of 34 gigatonnes, this budget will be exceeded within the next thirty years.

With global energy consumption set to double in the next thirty-five years, industry and the power sector are faced with an enormous challenge. Alongside making improvements in energy efficiency, the dilemma is to either not use a significant proportion of fossil fuel reserves that would exceed the budget (referred to as ‘unburnable carbon’), or capture emissions before or after being emitted the atmosphere. Carbon capture and storage (CCS) is a significant mitigation opportunity that could potentially enable us to use some fossil fuel reserves while preventing CO2 emissions.

The Sustainable Gas Institute (SGI) at Imperial College recently examined and quantified the long-term potential of CCS technologies in enabling access to, or ‘unlock’, fossil fuel reserves in a way that will meet climate targets and therefore mitigate climate change.

So what is the potential impact of CCS? While recent studies have examined the extent to which CCS impacts on the use of unburnable carbon, most studies only considered a short timeframe up to 2050, which showed CCS could make only a small impact (5.5%).  Our review used the results from several integrated assessment models (IAMs), and revealed that the potential of CCS in unlocking ‘unburnable carbon’ is greater in the second half of the century. In global scenarios without CCS, only 26% of fossil fuel reserves can be consumed by 2050. The proportion increases to 37% when CCS is available. By 2100, in scenarios without CCS, only slightly more fossil fuel reserves (33% vs 26%) were consumed, whereas in scenarios where CCS is widely deployed a greater proportion, up to 65% of global reserves could be consumed. This equates to 15,000 exajoules (EJ).

The results also showed that among the three key fossil fuels, natural gas and coal consumption were the most strongly affected by the adoption of CCS. There was an increase in coal use of 82–86 exajoules per year (EJ/yr) and gas use of 65–104 EJ/yr by 2100, while oil consumption could increase by 29–31 EJ/yr.

Future fossil fuel use will also be heavily dependent on improvements in capture rate, which is the percentage of CO2 that can be captured, transported and finally stored by CCS. Capture rate is particularly important for the role of natural gas, in future energy systems. Higher capture rates (>90%) could lead natural gas to maintaining its 2050 share of primary energy supply up to 2100. Achieving a lifetime capture rate greater than 95% of emissions is crucial.

In the short-term, there are a range of important barriers to overcome, including cost, lack of market and regulatory arrangements, potential supply chain gaps and cautious public perception. The use of CCS entails non-trivial capital costs and energy penalties, leading to relatively high overall cost versus unabated energy production, particularly high for early-stage demonstrations of the technologies.

For the long term future of CCS to be realised, all of these issues need to be addressed via research, development and demonstration, along with an effective set of policy instruments to support early-stage demonstration through to mass market application. Download the full report or the summary.

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